Hi all.

I am scheming to build a front-end loader for my tractor, and I have
been looking into hydraulics. I have a couple of pretty basic
questions which I have generated after reading various sources and
looking through the catalogs. Any help/insight into any of these
questions would be much appreciated.

First question regards spools for open-center systems. Some Army
literature talks about open-center spools versus tandem-center spools.
Assuming a 4way with lines T (tank), P (pump), A and B (ports to
cylinder) my understanding is that in neutral an "open center" spool
connects all ports (A,B and P) to the T (tank), such that there
wouldn't be any pressure to the cylinder (i.e. it is floating in
neutral). A tandem open-center spool (in neutral) connects P to T (so
it is just passing through the spool), and closes off A and B, holding
pressure in the A/B loop.

In the first case, a loader w/ an open-center as described would come
crashing down when you let off the controls, whereas the tandem would
hold it's position. Looking at the catalogs I haven't seen a
reference to a "tandem" spool, but I have seen "open-center with load
checks", and further reading suggests that load checks will hold the
cylinder in position.

So, is what I'm calling a tandem spool the same as an "open-center
with load checks"? Does a load check in a spool close off the lines
in neutral?

Second, if you have a spool that is rated for say 25GPM, will there be
any problem running it at a lower GPM? Say 12GPM or 5? Will it still
function properly/safely?

How is pressure controled in the system? Is it just a matter of
setting the relief/bypass values, and the lowest one will control the
pressure (although I guess this would depend on how it was plumbed)?
Most seem to say that they function from 1000psi to 3000psi - does
this mean I can make any combination of pressure/flow rate in the
system to achieive my goals or fit my pump/equipment?

What is the difference between a welded versus a tie rod cylinder?
Pros/cons?

Finally, in parallel spool decks is the flow simply divided between
the open spools, such that everything will work, but at a lower speed?
And pressure in all A/B lines is the same (so all spools get there
input from the P line)? In series is it that the flow out of one
spool feeds into another spool (so input is from the T line), and we
get a decrease in the pressure (with the same flow)?

Thanks in advance for your help. I appreciate any and all comments
and info.

don

Don
If I can remember my basic hydraulic classes of
so long ago, there are two types of hyd. systems.
Open center and closed center types. The difference centers around
the type of pump used..The closed center type only flows then there is
some demand, and the open center flows constantly, broadly speaking.

To design a hyd attachment would start with the type of pump
you have, if any, and what type of system ie open or closed center.
Give us some more info--what type of tractor,power steering, brakes
etc. Are you retrofitting an older 9N type or is this something a
more modern/larger?

DE





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I'd also like some good links or recomended texts on Hydraulics as I'm
starting to 'play' with them. First project will be a press. I have a
powerpack (AC 5Hp) already but I don't want to 'screw it up'
I have found and understand the basic theories, but could anyone
suggest a good place to get a glossary or explanaition of terms like
spools, 2 3 4 way valves etc.

I understand the Army (US) had a publication, but since most of those
sites were secured last year you cannot download the docs anymore.

Any reference texts (basics) you recommend?

Most of what I know was found in the Hydraulics 101 section of
http://northernhydraulics.sofastweb.net

Sorry Don, can't answer your questions but thought I'd ask on this
thread anyway.

Tom

(don schad) wrote in message . com...
Hi all.

I am scheming to build a front-end loader for my tractor, and I have
been looking into hydraulics. I have a couple of pretty basic
questions which I have generated after reading various sources and
looking through the catalogs. Any help/insight into any of these
questions would be much appreciated.

First question regards spools for open-center systems. Some Army
literature talks about open-center spools versus tandem-center spools.
Assuming a 4way with lines T (tank), P (pump), A and B (ports to
cylinder) my understanding is that in neutral an "open center" spool
connects all ports (A,B and P) to the T (tank), such that there
wouldn't be any pressure to the cylinder (i.e. it is floating in
neutral). A tandem open-center spool (in neutral) connects P to T (so
it is just passing through the spool), and closes off A and B, holding
pressure in the A/B loop.

In the first case, a loader w/ an open-center as described would come
crashing down when you let off the controls, whereas the tandem would
hold it's position. Looking at the catalogs I haven't seen a
reference to a "tandem" spool, but I have seen "open-center with load
checks", and further reading suggests that load checks will hold the
cylinder in position.

So, is what I'm calling a tandem spool the same as an "open-center
with load checks"? Does a load check in a spool close off the lines
in neutral?

Second, if you have a spool that is rated for say 25GPM, will there be
any problem running it at a lower GPM? Say 12GPM or 5? Will it still
function properly/safely?

How is pressure controled in the system? Is it just a matter of
setting the relief/bypass values, and the lowest one will control the
pressure (although I guess this would depend on how it was plumbed)?
Most seem to say that they function from 1000psi to 3000psi - does
this mean I can make any combination of pressure/flow rate in the
system to achieive my goals or fit my pump/equipment?

What is the difference between a welded versus a tie rod cylinder?
Pros/cons?

Finally, in parallel spool decks is the flow simply divided between
the open spools, such that everything will work, but at a lower speed?
And pressure in all A/B lines is the same (so all spools get there
input from the P line)? In series is it that the flow out of one
spool feeds into another spool (so input is from the T line), and we
get a decrease in the pressure (with the same flow)?

Thanks in advance for your help. I appreciate any and all comments
and info.

don

(surftom) wrote in
om:

I'd also like some good links or recomended texts on Hydraulics as I'm
starting to 'play' with them. First project will be a press. I have a
powerpack (AC 5Hp) already but I don't want to 'screw it up'
I have found and understand the basic theories, but could anyone
suggest a good place to get a glossary or explanaition of terms like
spools, 2 3 4 way valves etc.

I understand the Army (US) had a publication, but since most of those
sites were secured last year you cannot download the docs anymore.

Any reference texts (basics) you recommend?

Most of what I know was found in the Hydraulics 101 section of
http://northernhydraulics.sofastweb.net

Sorry Don, can't answer your questions but thought I'd ask on this
thread anyway.

Tom

(don schad) wrote in message
. com...
Hi all.

I am scheming to build a front-end loader for my tractor, and I have
been looking into hydraulics. I have a couple of pretty basic
questions which I have generated after reading various sources and
looking through the catalogs. Any help/insight into any of these
questions would be much appreciated.

First question regards spools for open-center systems. Some Army
literature talks about open-center spools versus tandem-center
spools.
Assuming a 4way with lines T (tank), P (pump), A and B (ports to
cylinder) my understanding is that in neutral an "open center" spool
connects all ports (A,B and P) to the T (tank), such that there
wouldn't be any pressure to the cylinder (i.e. it is floating in
neutral). A tandem open-center spool (in neutral) connects P to T
(so it is just passing through the spool), and closes off A and B,
holding pressure in the A/B loop.

In the first case, a loader w/ an open-center as described would come
crashing down when you let off the controls, whereas the tandem would
hold it's position. Looking at the catalogs I haven't seen a
reference to a "tandem" spool, but I have seen "open-center with load
checks", and further reading suggests that load checks will hold the
cylinder in position.

So, is what I'm calling a tandem spool the same as an "open-center
with load checks"? Does a load check in a spool close off the lines
in neutral?

Second, if you have a spool that is rated for say 25GPM, will there
be any problem running it at a lower GPM? Say 12GPM or 5? Will it
still function properly/safely?

How is pressure controled in the system? Is it just a matter of
setting the relief/bypass values, and the lowest one will control the
pressure (although I guess this would depend on how it was plumbed)?
Most seem to say that they function from 1000psi to 3000psi - does
this mean I can make any combination of pressure/flow rate in the
system to achieive my goals or fit my pump/equipment?

What is the difference between a welded versus a tie rod cylinder?
Pros/cons?

Finally, in parallel spool decks is the flow simply divided between
the open spools, such that everything will work, but at a lower
speed?
And pressure in all A/B lines is the same (so all spools get there
input from the P line)? In series is it that the flow out of one
spool feeds into another spool (so input is from the T line), and we
get a decrease in the pressure (with the same flow)?

Thanks in advance for your help. I appreciate any and all comments
and info.

don


I suggest the open center valve, since constant flowing fluid requires
less energy than running everything through the pressure relief back to
tank. There will still be some go through the relief, depending on your
pump and the rest of the plumbing.
The open center, to my understanding, will, as you move the spool off-
center, divert flow from the T line to either A or B ports. when the
valve returns to center, all flow goes to T. Remember, unlike pneumatic
systems, you have a constant flow of fluid. It has to flow somewhere. If
it doesn't flow back to the tank through the spool, it will have to go
through the pressure relief, meaning your engine will have to produce
enough power to maintain the max system pressure at all times, not the
best way...you only need pressure when there is work to do.



--
Anthony

You can't 'idiot proof' anything....every time you try, they just make
better idiots.

Remove sp to reply via email

(surftom) wrote in message . com...
I'd also like some good links or recomended texts on Hydraulics as I'm
starting to 'play' with them. First project will be a press. I have a
powerpack (AC 5Hp) already but I don't want to 'screw it up'
I have found and understand the basic theories, but could anyone
suggest a good place to get a glossary or explanaition of terms like
spools, 2 3 4 way valves etc.

I understand the Army (US) had a publication, but since most of those
sites were secured last year you cannot download the docs anymore.

The Army hydraulics manual is at:

http://www.adtdl.army.mil/cgi-bin/at.../5-499/toc.htm

and there are some other interesting links at www.metalworking.com
under the links to learning section.

The Army manual and supplier catalogs, and deja are the things which I
have found the most useful in figuring out stuff. I don't think it's
all that hard, you just have to understand the lingo (I think )

don

Okay, a brief description:

It's going to be a self contained unit for a compact/garden tractor
(PowerKing). So I will be purchasing a dedicated pump and all the
associated plumbing for the project, since the current hydro pump is
of much lower flow (like 4-6GPM I think). The tractor has a 14HP
motor, so I should be able to run at least 10GPM at 1500PSI, possibly
slightly more. I believe that most loaders have 10-12GPM pumps.
Since it's a relatively small tractor the lifting limit is going to be
limited by the size of the tractor (i.e. it'll fall over forward)
rather then by the hydraulic system, but I would like it to be fairly
quick to go up/down. (Unless convienced otherwise) I was planning on
using an open-center system since that seems to be more popular and
common. Seems like it might be a bit simplier also.

I guess that's it...any advice is welcome.

Thanks,

don


DE wrote in message . ..
Don
If I can remember my basic hydraulic classes of
so long ago, there are two types of hyd. systems.
Open center and closed center types. The difference centers around
the type of pump used..The closed center type only flows then there is
some demand, and the open center flows constantly, broadly speaking.

To design a hyd attachment would start with the type of pump
you have, if any, and what type of system ie open or closed center.
Give us some more info--what type of tractor,power steering, brakes
etc. Are you retrofitting an older 9N type or is this something a
more modern/larger?

DE





-----= Posted via Newsfeeds.Com, Uncensored Usenet News =-----
http://www.newsfeeds.com - The #1 Newsgroup Service in the World!
-----== Over 100,000 Newsgroups - 19 Different Servers! =-----

"don schad" wrote in message
om...
Hi all.

I am scheming to build a front-end loader for my tractor, and I have
been looking into hydraulics. I have a couple of pretty basic
questions which I have generated after reading various sources and
looking through the catalogs. Any help/insight into any of these
questions would be much appreciated.

Your best bet is the simplest type of open-center system. This has a pump
that pumps a constant volume and in the "idle" condition, with all the
spools at center position, there is free flow through the system and the
only power consumed (and heat generated) is from friction loss in the pump
and plumbing. Almost any other type of system is far more expensive and
complicated.

Open-center valves are so common that the term has come to mean what your
old text calls "tandem". In the center position there is free flow from P
to T, and A and B are shut off and blocked, so that whatever cylinder is
connected to A and B is locked in position.

There is typically only a single pressure relief in the system, built in to
the valve body, set at whatever the safe limit is for the pump, hoses, valve
body, cylinders etc. This could be anywhere from 1500 to 3000 psi for a
minimum-cost system. Won't find it in minimum-cost equipment.

If your cylinder bores and mechanical linkages are sized properly, there is
no need for separate pressure relief settings for each cylinder. Pressure
and flow limiting comes into play only in equipment where the operator can
plausibly break something, and for some reason it's easier to protect the
equipment by pressure limiting than by sizing the cylinder.

The limitation of open-center is that to get predictable response at the
cylinders, you can operate only one spool at a time. For example raise the
boom, tilt the bucket, raise the boom, tilt the bucket.

In an open-center system, with more than one spool open there is nothing to
distribute or balance the pressure between the active spools and their
cylinders, so all the flow will go to whichever cylinder is presenting the
least resistance to work. In an extreme case, the fluid might even flow
backwards through a spool. For example raising a boom (lots of effort)
while lowering a bucket (low effort) may result in the boom at first falling
instead of rising, until the bucket has tilted to its extreme.

But the cost advantage is so strong that you just deal with it by operating
only one at a time.
with all your spools

Closed-center can mean a number of different types of systems. It can be
the same constant-volume pump that in the "idle" condition is pumping its
full output against a pressure relief valve set at a full system pressure of
say 2500 psi. The advantage of this design is to the extent that the pump
can supply the required volume, multiple spools can be opened with
predictable flow in response to each's position independent of the load on
the cylinders. Burst-flow at full pressure can be had by adding an
accumulator, that is a bladder pressure tank. This is probably the
second-cheapest system design and is used for equipment that requires
precise operation of multiple spools at the same time while still keeping
the cost reasonable. Its behavior has more in common with compressed air
systems. The main disadvantage of this type is that the system is running
continuously at full power and the entire output of the engine and pump are
going into heat that must be blown off in a radiator.

More sophisticated closed-center systems use variable-volume pumps that
maintain constant pressure at all the spools while wasting far less power.
There are also more sophisticated multiple-spool valves that behave like
open-center valves when all the spools are at center.

A "load check" is a one-way flow valve that prevents backwards flow through
a spool when multiple spools are open in an open-center system. It has
nothing to do with pressure relief or with whether the valve blocks flow or
"floats" when at center.

The only disadvantage of using a spool that is rated for a much higher flow
than your application is that it may provide less of a "fine touch" control
than a smaller valve. It should not be a problem for what you describe.

"Normal" multiple-spool valves are parallel flow which has the issue
described above, with all flow going the path of least resistance when
multiple spools are active.

Bob

On 28 Jan 2004 10:46:21 -0800, (surftom) brought
forth from the murky depths:

I'd also like some good links or recomended texts on Hydraulics as I'm
starting to 'play' with them. First project will be a press. I have a

Try your local library. I found a fun little 1,000 page book
titled Audel's "Pumps, Hydraulics, Air Compressors; A practical guide
covering theory, constructon, and operation of modern pumps, hydraulic
machinery, air compressors and blowers" (How's that for a title?)
Author: Graham, Frank Duncan



----------------------------------------------
CAUTION: Driver Legally B l o n d (e)
http://www.diversify.com Web Database Development
================================================== =====

On Wed, 28 Jan 2004 22:32:42 GMT, Anthony
vaguely proposed a theory
.......and in reply I say!:


I suggest the open center valve, since constant flowing fluid requires
less energy than running everything through the pressure relief back to
tank. There will still be some go through the relief, depending on your
pump and the rest of the plumbing.
The open center, to my understanding, will, as you move the spool off-
center, divert flow from the T line to either A or B ports. when the
valve returns to center, all flow goes to T. Remember, unlike pneumatic
systems, you have a constant flow of fluid. It has to flow somewhere. If
it doesn't flow back to the tank through the spool, it will have to go
through the pressure relief, meaning your engine will have to produce
enough power to maintain the max system pressure at all times, not the
best way...you only need pressure when there is work to do.

No kidding there. If you run a hnydraulic FEL, and let it keep pumping
when the ram has reached full stroke, you feel even a quite powerful
machine (120HP) hesitate. I have been caught by the crowd a couple of
times (the lift is a little more obviuos G). A little tractor will
die, at anything other than something approaching full revs, trying to
run the max pressure of a hydro system of any grunt. I learned this
when I took a backhoe off a Massey 40 tractor with FEL/backhoe and
forgot to join the out and in hoses. They have an auto stop on them. I
wanted to move the tractor a few yards, and it just would not run.
************************************************** ** sorry
remove ns from my header address to reply via email

Spike....Spike? Hello?

Don,
What you described is doable, there is a good
description of a basic hydraulic system below. You would
need a pump, tank, double spool valve, cylinders press relief,filter
and plumbing. Sounds a lot like a script for an upcoming Monster
Garage......:-) While I can't say I am familar what your specific
unit is.... but check this out
http://cgi.ebay.com/ws/eBayISAPI.dll...tegory=50 377

This has a very well designed hydraulic system, closed center I do
believe, compact and integrated, the pump is an axial
piston servo type, a spitting image to the big ones used in the heavy
ag stuff. I had one apart years ago IIRC it couples internally to a
motor for the drive. and has two fittings for the remote lines. You
can see the valve handles along the steering wheel.
If this would fit into your unit it might be a lot more cost efficient
not to mention simpler than buying just the pump. There seems to be a
fair supply of these around the series1 Kohler engines evidently had
a serious problems staying together. I know loader att. were used on
these units.
email for more info if needed
Good luck
Dan


On 28 Jan 2004 15:31:31 -0800, (don schad)
wrote:

Okay, a brief description:

It's going to be a self contained unit for a compact/garden tractor
(PowerKing). So I will be purchasing a dedicated pump and all the
associated plumbing for the project, since the current hydro pump is
of much lower flow (like 4-6GPM I think). The tractor has a 14HP
motor, so I should be able to run at least 10GPM at 1500PSI, possibly
slightly more. I believe that most loaders have 10-12GPM pumps.
Since it's a relatively small tractor the lifting limit is going to be
limited by the size of the tractor (i.e. it'll fall over forward)
rather then by the hydraulic system, but I would like it to be fairly
quick to go up/down. (Unless convienced otherwise) I was planning on
using an open-center system since that seems to be more popular and
common. Seems like it might be a bit simplier also.

I guess that's it...any advice is welcome.

Thanks,

don


DE wrote in message . ..
Don
If I can remember my basic hydraulic classes of
so long ago, there are two types of hyd. systems.
Open center and closed center types. The difference centers around
the type of pump used..The closed center type only flows then there is
some demand, and the open center flows constantly, broadly speaking.

To design a hyd attachment would start with the type of pump
you have, if any, and what type of system ie open or closed center.
Give us some more info--what type of tractor,power steering, brakes
etc. Are you retrofitting an older 9N type or is this something a
more modern/larger?

DE





-----= Posted via Newsfeeds.Com, Uncensored Usenet News =-----
http://www.newsfeeds.com - The #1 Newsgroup Service in the World!
-----== Over 100,000 Newsgroups - 19 Different Servers! =-----



-----= Posted via Newsfeeds.Com, Uncensored Usenet News =-----
http://www.newsfeeds.com - The #1 Newsgroup Service in the World!
-----== Over 100,000 Newsgroups - 19 Different Servers! =-----

"surftom" wrote in message
om...
I'd also like some good links or recomended texts on Hydraulics as I'm
starting to 'play' with them. First project will be a press. I have a
powerpack (AC 5Hp) already but I don't want to 'screw it up'
I have found and understand the basic theories, but could anyone
suggest a good place to get a glossary or explanaition of terms like
spools, 2 3 4 way valves etc.


We used both Industrial Hydraulic Technology by Parker and
Industrial Hydraulics Manual by Vickers in a hydraulics class I
recently took. Both books cover basic hydraulics and include
color drawings indicating pressures in a variety of circuits.
The Vickers book has an additional chapter on basic electricity
and electronics.

Nate


--
http://www.NateTechnologies.net:8000

Can an automotive power steering pump be used for hobby uses such as a
press?

Gunner


"This device is provided without warranty of any kind as to reliability,
accuracy, existence or otherwise or fitness for any particular purpose
and Bioalchemic Products specifically does not warrant, guarantee,
imply or make any representations as to its merchantability for any
particular purpose and furthermore shall have no liability for or
responsibility to you or any other person, entity or deity with respect
to any loss or damage whatsoever caused by this device or object or by
any attempts to destroy it by hammering it against a wall or dropping it
into a deep well or any other means whatsoever and moreover asserts
that you indicate your acceptance of this agreement or any other
agreement that may he substituted at any time by coming within
five miles of the product or observing it through large telescopes or
by any other means because you are such an easily cowed moron
who will happily accept arrogant and unilateral conditions on a piece
of highly priced garbage that you would not dream of accepting on a
bag of dog biscuits and is used solely at your own risk.'

Toolbert wrote:
"don schad" wrote in message
om...

Hi all.

I am scheming to build a front-end loader for my tractor, and I have
been looking into hydraulics. I have a couple of pretty basic
questions which I have generated after reading various sources and
looking through the catalogs. Any help/insight into any of these
questions would be much appreciated.


Your best bet is the simplest type of open-center system. This has a pump
that pumps a constant volume and in the "idle" condition, with all the
spools at center position, there is free flow through the system and the
only power consumed (and heat generated) is from friction loss in the pump
and plumbing. Almost any other type of system is far more expensive and
complicated.

Open-center valves are so common that the term has come to mean what your
old text calls "tandem". In the center position there is free flow from P
to T, and A and B are shut off and blocked, so that whatever cylinder is
connected to A and B is locked in position.

There is typically only a single pressure relief in the system, built in to
the valve body, set at whatever the safe limit is for the pump, hoses, valve
body, cylinders etc. This could be anywhere from 1500 to 3000 psi for a
minimum-cost system. Won't find it in minimum-cost equipment.

If your cylinder bores and mechanical linkages are sized properly, there is
no need for separate pressure relief settings for each cylinder. Pressure
and flow limiting comes into play only in equipment where the operator can
plausibly break something, and for some reason it's easier to protect the
equipment by pressure limiting than by sizing the cylinder.

The limitation of open-center is that to get predictable response at the
cylinders, you can operate only one spool at a time. For example raise the
boom, tilt the bucket, raise the boom, tilt the bucket.

In an open-center system, with more than one spool open there is nothing to
distribute or balance the pressure between the active spools and their
cylinders, so all the flow will go to whichever cylinder is presenting the
least resistance to work. In an extreme case, the fluid might even flow
backwards through a spool. For example raising a boom (lots of effort)
while lowering a bucket (low effort) may result in the boom at first falling
instead of rising, until the bucket has tilted to its extreme.

But the cost advantage is so strong that you just deal with it by operating
only one at a time.
with all your spools

Closed-center can mean a number of different types of systems. It can be
the same constant-volume pump that in the "idle" condition is pumping its
full output against a pressure relief valve set at a full system pressure of
say 2500 psi. The advantage of this design is to the extent that the pump
can supply the required volume, multiple spools can be opened with
predictable flow in response to each's position independent of the load on
the cylinders. Burst-flow at full pressure can be had by adding an
accumulator, that is a bladder pressure tank. This is probably the
second-cheapest system design and is used for equipment that requires
precise operation of multiple spools at the same time while still keeping
the cost reasonable. Its behavior has more in common with compressed air
systems. The main disadvantage of this type is that the system is running
continuously at full power and the entire output of the engine and pump are
going into heat that must be blown off in a radiator.

More sophisticated closed-center systems use variable-volume pumps that
maintain constant pressure at all the spools while wasting far less power.
There are also more sophisticated multiple-spool valves that behave like
open-center valves when all the spools are at center.

A "load check" is a one-way flow valve that prevents backwards flow through
a spool when multiple spools are open in an open-center system. It has
nothing to do with pressure relief or with whether the valve blocks flow or
"floats" when at center.

The only disadvantage of using a spool that is rated for a much higher flow
than your application is that it may provide less of a "fine touch" control
than a smaller valve. It should not be a problem for what you describe.

"Normal" multiple-spool valves are parallel flow which has the issue
described above, with all flow going the path of least resistance when
multiple spools are active.

Bob


If I was doing this I would not use oversize valves or pump . With small
bore rams it will go up and down too damned fast . You will never be
able to feather the loader like you will need at times . That plus
smaller components will be a lot cheaper to buy . Ask any industrial
supplier and they will be able to help you size the components to where
they will work with what is already proven acceptable .
Ken Cutt

On Thu, 29 Jan 2004 01:20:19 GMT, "Toolbert"
vaguely proposed a theory
.......and in reply I say!:

Lovely. Seriously. I have learnt all this after much searching. It is
beautifully put.

Only thing....

Your best bet is the simplest type of open-center system. This has a pump
that pumps a constant volume and in the "idle" condition, with all the
snip
The only disadvantage of using a spool that is rated for a much higher flow
than your application is that it may provide less of a "fine touch" control
than a smaller valve. It should not be a problem for what you describe.

A large flow spool with little feel can be a problem if the unit is to
be used as a "crane" (and if you say it wont' you LIE G), and you
don't have the feel.
************************************************** ** sorry
remove ns from my header address to reply via email

Spike....Spike? Hello?

On Thu, 29 Jan 2004 01:20:19 GMT, "Toolbert"
vaguely proposed a theory
.......and in reply I say!:

OK. You give a good impression of being able to put the truth across.

I have a backhoe. I find that some of the controls for the digger
(slew in particular) are way too fast. I wanted to place a flow
limiter in the circuit, preferably adjustable within limits, so that I
do not have to be _so_ careful with the slew controls when working,
especially in confined sirrounds.

I was told this would not work, as it would force fluid back through
the pressure release/return all the time and heat the fluid too much.

The system is quite large for the machine (industrail, not farm setup
on a little Massye 40) and has about 30-40 litres of tank capacity. I
spend a lot of time "feathering" the controls anyway, which is going
to have the same effect, no? Is there really a problem?

Thanks for you attention and any help.
************************************************** ** sorry
remove ns from my header address to reply via email

Spike....Spike? Hello?

Yes, they are used to drive the Milemarker winches. They aren't a
very big pump, don't have any specs for you.

Gunner wrote:

Can an automotive power steering pump be used for hobby uses such as a
press?

Gunner


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responsibility to you or any other person, entity or deity with respect
to any loss or damage whatsoever caused by this device or object or by
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that you indicate your acceptance of this agreement or any other
agreement that may he substituted at any time by coming within
five miles of the product or observing it through large telescopes or
by any other means because you are such an easily cowed moron
who will happily accept arrogant and unilateral conditions on a piece
of highly priced garbage that you would not dream of accepting on a
bag of dog biscuits and is used solely at your own risk.'

Heh, heh. Just use an undesize hydrualic line going to the slew
cylinder(s). I'm sure a 1/4" line will work just fine.

Old Nick wrote:

On Thu, 29 Jan 2004 01:20:19 GMT, "Toolbert"
vaguely proposed a theory
......and in reply I say!:

OK. You give a good impression of being able to put the truth across.

I have a backhoe. I find that some of the controls for the digger
(slew in particular) are way too fast. I wanted to place a flow
limiter in the circuit, preferably adjustable within limits, so that I
do not have to be _so_ careful with the slew controls when working,
especially in confined sirrounds.

I was told this would not work, as it would force fluid back through
the pressure release/return all the time and heat the fluid too much.

The system is quite large for the machine (industrail, not farm setup
on a little Massye 40) and has about 30-40 litres of tank capacity. I
spend a lot of time "feathering" the controls anyway, which is going
to have the same effect, no? Is there really a problem?

Thanks for you attention and any help.
************************************************** ** sorry
remove ns from my header address to reply via email

Spike....Spike? Hello?

"Old Nick" wrote in message
news
On Thu, 29 Jan 2004 01:20:19 GMT, "Toolbert"
vaguely proposed a theory
......and in reply I say!:

OK. You give a good impression of being able to put the truth across.

I have a backhoe. I find that some of the controls for the digger
(slew in particular) are way too fast. I wanted to place a flow
limiter in the circuit, preferably adjustable within limits, so that I
do not have to be _so_ careful with the slew controls when working,
especially in confined sirrounds.

I was told this would not work, as it would force fluid back through
the pressure release/return all the time and heat the fluid too much.

The system is quite large for the machine (industrail, not farm setup
on a little Massye 40) and has about 30-40 litres of tank capacity. I
spend a lot of time "feathering" the controls anyway, which is going
to have the same effect, no? Is there really a problem?

I haven't had the pleasure of operating anything with high-quality fine
touch control. It's second nature to just throttle down. I spent a bit of
last summer operating a little excavator within inches of a building and
tried hard to not punch any extra holes. Spent a lot of time near idle.

I think with a farm tractor you just deal with its limits. It'll have
enough other limits. If the hydraulic system is not properly sized or
designed it'll still get the job done, just with more risk of breaking
something. (An engineeered system will have all the cylinder bores sized
to the mechanical design so full pressure won't bend things.)

Adding a flow limiter is beyond my depth. I like the suggestion about
going with smaller hoses, though there is more risk of blowing the hoses
with pressure surges from mechanical shock.

Bob

I've read stories of them being used for presses and even
for forming motorcycle headers from flat edge welded sheet
by internal pressure, kinda like blowing up a balloon.
Some of them have pressure capabilities of 4000-6000 psi,
I've heard. This is a little more than the typical "farmer"
hydraulic pressure standard of 2100 psi. They usually don't
have the volume flow capabilities of the lower pressure
pumps.

Gunner wrote:

Can an automotive power steering pump be used for hobby uses such as a
press?

On Thu, 29 Jan 2004 09:24:15 -0600, Roy J
vaguely proposed a theory
.......and in reply I say!:

Heh, heh. Just use an undesize hydrualic line going to the slew
cylinder(s). I'm sure a 1/4" line will work just fine.

I wondered about that or longer runs, but was concerned about the same
"problem" that was presented by a reducing valve.

I would not be surprised if the hoses are the wrong size anyway G.
Old machine


************************************************** ** sorry
remove ns from my header address to reply via email

Spike....Spike? Hello?

On Thu, 29 Jan 2004 16:20:19 GMT, "Toolbert"
vaguely proposed a theory
.......and in reply I say!:

I will try the smaller hose size. The danger of hoses bursting is not
unknown this machine anyway, so new lines too smalle are probably the
least of my worriesG

This is actually an industrial setup, but old.

I haven't had the pleasure of operating anything with high-quality fine
touch control. It's second nature to just throttle down. I spent a bit of
last summer operating a little excavator within inches of a building and
tried hard to not punch any extra holes. Spent a lot of time near idle.

I think with a farm tractor you just deal with its limits. It'll have
enough other limits. If the hydraulic system is not properly sized or
designed it'll still get the job done, just with more risk of breaking
something. (An engineeered system will have all the cylinder bores sized
to the mechanical design so full pressure won't bend things.)

Adding a flow limiter is beyond my depth. I like the suggestion about
going with smaller hoses, though there is more risk of blowing the hoses
with pressure surges from mechanical shock.

Bob


************************************************** ** sorry
remove ns from my header address to reply via email

Spike....Spike? Hello?

Hi all,

Thanks for all the help/suggestions. It's very much appreciated.

I'll take the liberty to ask another question while we are he

There has been a lot of talk about having things sized properly such that
the system is controllable. Is proper sizing just a question of making some
assumptions and doing the math?
For example, lets say that I wanted the loader to go from the ground to the
full-up position in 3 seconds (is this too fast? too slow?).
Assuming:

Two hydraulic cylinders with a bore of 2", and a stroke of 14" to go from
down to full up.
3 seconds to extend ram 14"

To compute flow:
Speed (in/min) = flow (in3/min) / area (in2)
flow = speed (in/min) * area(in2) = 14"/0.05min * 3.141in2 = 880in3/min *
1g/260in3 = 3.4gpm
and since we have two cylinders, we need 6.8gpm?

This estimate seems to be reasonable based on what I have seen for other
loaders regarding pump size. Is this (basically) all there is to it? And
from there should I pick the lowest pressure which will (a) operate all the
parts and (b) give me the force which I need to do what I want? So if I
want to have the loader capacity be 1000#, I would have two cylinders which
could produce (minimally, since I guess there is geometry to consider and
the loss of usable lifting force - haven't gotten there yet ) 500# each
at a given PSI (seems like 1500 is the lowest common on, and this will
produce a force 500#)?

Easy...so what am I missing?

As always, thanks a lot for your help.

don



"don schad" wrote in message
om...
Hi all.

I am scheming to build a front-end loader for my tractor, and I have
been looking into hydraulics. I have a couple of pretty basic
questions which I have generated after reading various sources and
looking through the catalogs. Any help/insight into any of these
questions would be much appreciated.
.....

Thanks in advance for your help. I appreciate any and all comments
and info.

don

Hi all,

Thanks for all the help/suggestions. It's very much appreciated.

I'll take the liberty to ask another question while we are he

There has been a lot of talk about having things sized properly such that
the system is controllable. Is proper sizing just a question of making some
assumptions and doing the math?
For example, lets say that I wanted the loader to go from the ground to the
full-up position in 3 seconds (is this too fast? too slow?).
Assuming:

Two hydraulic cylinders with a bore of 2", and a stroke of 14" to go from
down to full up.
3 seconds to extend ram 14"

To compute flow:
Speed (in/min) = flow (in3/min) / area (in2)
flow = speed (in/min) * area(in2) = 14"/0.05min * 3.141in2 = 880in3/min *
1g/260in3 = 3.4gpm
and since we have two cylinders, we need 6.8gpm?

This estimate seems to be reasonable based on what I have seen for other
loaders regarding pump size. Is this (basically) all there is to it? And
from there should I pick the lowest pressure which will (a) operate all the
parts and (b) give me the force which I need to do what I want? So if I
want to have the loader capacity be 1000#, I would have two cylinders which
could produce (minimally, since I guess there is geometry to consider and
the loss of usable lifting force - haven't gotten there yet ) 500# each
at a given PSI (seems like 1500 is the lowest common on, and this will
produce a force 500#)?

Easy...so what am I missing?

As always, thanks a lot for your help.

don



"don schad" wrote in message
om...
Hi all.

I am scheming to build a front-end loader for my tractor, and I have
been looking into hydraulics. I have a couple of pretty basic
questions which I have generated after reading various sources and
looking through the catalogs. Any help/insight into any of these
questions would be much appreciated.
.....

Thanks in advance for your help. I appreciate any and all comments
and info.

don

"don schad" wrote in message
...
Hi all,

Thanks for all the help/suggestions. It's very much appreciated.

I'll take the liberty to ask another question while we are he

There has been a lot of talk about having things sized properly such that
the system is controllable. Is proper sizing just a question of making
some
assumptions and doing the math?
For example, lets say that I wanted the loader to go from the ground to
the
full-up position in 3 seconds (is this too fast? too slow?).
Assuming:

Two hydraulic cylinders with a bore of 2", and a stroke of 14" to go from
down to full up.
3 seconds to extend ram 14"

To compute flow:
Speed (in/min) = flow (in3/min) / area (in2)
flow = speed (in/min) * area(in2) = 14"/0.05min * 3.141in2 = 880in3/min *
1g/260in3 = 3.4gpm
and since we have two cylinders, we need 6.8gpm?

This estimate seems to be reasonable based on what I have seen for other
loaders regarding pump size. Is this (basically) all there is to it? And
from there should I pick the lowest pressure which will (a) operate all
the
parts and (b) give me the force which I need to do what I want? So if I
want to have the loader capacity be 1000#, I would have two cylinders
which
could produce (minimally, since I guess there is geometry to consider and
the loss of usable lifting force - haven't gotten there yet ) 500# each
at a given PSI (seems like 1500 is the lowest common on, and this will
produce a force 500#)?

Easy...so what am I missing?

As always, thanks a lot for your help.

don

Probably most useful to work backwards from what you want to accomplish and
are willing to spend. Look at the tractor, figure out how much weight can
be cantilevered how far in front of the front wheels, and what size pump
(pressure x volume) the engine can drive. Then work out the geometry of
the linkages and cylinders to figure out what straight force is required at
each cylinder or pair of cylinders to accomplish the lift (force, not
speed). Then compute the cylinder bore to provide that force. This will
tell you the lifting speed.

If you want a different lift speed, resize the pump (and maybe the engine)
or lower the lifting load capacity.

It's probably best to go with a 2500 psi design pressure, going lower is a
waste of $ as the common pumps, valves, hoses are intended for that working
pressure.

I've never designed and actually built anything hydraulic, just lots of
pencil exercise. So this is pretty rough. A basic valve will give you
some fine control. I think you're better off to get finer control by
throttling down the engine than by going with a fancier design.

As for your geometry and mechanical design, that's more on topic I suppose,
but it's hard to quantify. A well-engineered piece of professional
equipment will be much lighter for the same strength than a quick-and-dirty
homebrew. You can use handbook references to size the main members, pins,
bolts and such but figuring out all the stresses in 3-D is much more of a
challenge. Stresses will concentrate at joints, that calls for gussets, and
you'll want to consider side forces and twisting forces from off-center
loads or digging with the corner of a bucket. Common sense and intuition
goes a long way. I've been impressed with some homebrew loader designs but
they tend to be overbuilt and work better with a large, heavy tractor. If
I was going this route with a small tractor I would literally prototype it,
cut and patch and try different geometry until it felt right and then
finish, clean and paint it.

Bob

On Fri, 30 Jan 2004 11:21:05 -0500, "don schad"
brought forth from the murky depths:

Hi all,

Thanks for all the help/suggestions. It's very much appreciated.

I'll take the liberty to ask another question while we are he

There has been a lot of talk about having things sized properly such that
the system is controllable. Is proper sizing just a question of making some
assumptions and doing the math?
For example, lets say that I wanted the loader to go from the ground to the
full-up position in 3 seconds (is this too fast? too slow?).

I'm not an engineer and don't play one on TV or the net, but...

Probably too fast. Add in calcs for mass/velocity/stress. With
a load, your 3-second rate would probably make your loader do
a reverse wheelie before bouncing back and dropping the load
on your head. You're building a loader, not a trebuchet, right?


That's just a f'rinstance. Calculations will tell you a bit more
closely whether the load@velocity will overstressthe beams and/or
unbalance the tractor.

Grab a rigging book from the library. I just returned Rossnagel's
"Handbook of rigging, for construction and industrial operations"
to the library as I didn't have time to go through the thing,
but it looked interesting. Any book on hydraulic design might
be of help, too.

----------------------------------------------
CAUTION: Driver Legally B l o n d (e)
http://www.diversify.com Web Database Development
================================================== =====

On Fri, 30 Jan 2004 11:16:56 -0500, "don schad"
vaguely proposed a theory
.......and in reply I say!:

OK. You think even the theory's simple. I am a RAG (Rough as GUTS)
dirt breaker "engineer" who uses old "big boys toys" to try to make my
property behave itself, but hydraulics fascinates me, and I needed to
look at a few things, because I wanted to make up strong things to fit
on buckets etc.

I am reasonably bright, even though I often hide it well. But I am not
qualified and I am ony fiddling around the fringes.

So even at my level I am constantly coming up against inertia,
pressure, area, physics, geometry, just in design. Then when I started
welding the steels used in these machines, along came chemistry,
metalurgy.....and in some cases quite a bit of bloody inertia, when
trying to move the bits about.G

Then there is bearing mechanics, lubrication, wear steels etc etc.

You don't _need_ to be qualified. But remember that many years' worth
of though has gone into machines that continually evolve as new
mistakes are made.

Hi all,

Thanks for all the help/suggestions. It's very much appreciated.

I'll take the liberty to ask another question while we are he

There has been a lot of talk about having things sized properly such that
the system is controllable. Is proper sizing just a question of making some
assumptions and doing the math?

Yes. Provided you make the right assumptions. From what you say you
are not even looking at tractors with loaders on them.

Assumption #1. You do NOT knwo what you are doing
Assumption #2. Others do things for a reason.

For example, lets say that I wanted the loader to go from the ground to the
full-up position in 3 seconds (is this too fast? too slow?).

WooHoooo! Too fast. Just sit there and imagine you are in your tractor
(or sit in the tractor if it's available) and imagine a tonne or so of
stuff raising to right above your head from the ground in 3 seconds!
Most tractor-based loaders lift very high towards over your head to
get the height for trucks etc.

Speaking of which, you would not want to go _too_ far. The rams should
not be too long or too short.

Also, imagine the force on the back of the tractor. You would probably
bite the dirt right under the bucket.

8-15 seconds is more common, with lowering a lot faster. For a farm
tractor, head toward the 15 seconds IMO.

You should need to keep the revs up to get a fast lift, so that you
have a slow lift when needed. To give you an idea of how important
this is, a commercial loader often has a brake pedal that also
disengages the auto transmission, so you don't need to be in neutral
when raising the bucket.

Assuming:

Two hydraulic cylinders with a bore of 2", and a stroke of 14" to go from
down to full up.
3 seconds to extend ram 14"

To compute flow:
Speed (in/min) = flow (in3/min) / area (in2)
flow = speed (in/min) * area(in2) = 14"/0.05min * 3.141in2 = 880in3/min *
1g/260in3 = 3.4gpm
and since we have two cylinders, we need 6.8gpm?

Nope. To go from full down to full up will take more like 2 x 36"
cylinders, maybe 2.5" working diam. A lot of this is neeed not for
lift but for strength.


This estimate seems to be reasonable based on what I have seen for other
loaders regarding pump size. Is this (basically) all there is to it? And
from there should I pick the lowest pressure which will (a) operate all the
parts and (b) give me the force which I need to do what I want? So if I
want to have the loader capacity be 1000#, I would have two cylinders which
could produce (minimally, since I guess there is geometry to consider and
the loss of usable lifting force - haven't gotten there yet ) 500# each
at a given PSI (seems like 1500 is the lowest common on, and this will
produce a force 500#)?


Easy...so what am I missing?

shudder....wrong attitude.

In answer to your question....what you are missing is that geometry
that you "have not got to yet".

This is off the top of my head. I may get a few details wrong. but I
think I am close. For 10 to one maybe say 8:1 etc. But the errors will
cut both ways, I am sure. Prove me working and you are on the way to
designing G

Your 14" cylinders above will have to move the end of the bucket maybe
12' full down to full up. So to lift 1000lbs _at the best angle_,
firstly we need 144"/14" = 10,000 lb. Then the cylinders are often at
an angle (to the _direction of effort required_) of maybe 45 deg.
Divide by the sin of 45 deg. 14500 lbs. If the angle changes to 30 deg
than divide by the sin of 30 deg. I admit that I did quick diagram
that showed 14" rams at 90 deg. So we could arrange that to go. But as
soon as the arms begin to lift, the angle changes. best check at many
locations.

Remember the weight of the loader arms and bucket. Probably a good
100lbs in themselves, spread in quite a complex manner. So let's say
the arms are weight spread evenly. You immediately add another 1000lb
with COG at 4' from the fulcrum. In other words you have to multiply
all your forces by 1.5.....say 21,000 lbs. The beam strength at the
rams attachment point would need to be impressive with such short
rams, as they need to be attached right near the fulcrum. The fulcrum
pins would be impressive as well.

etc

It can be quite complex, and is very dynamic as the loader cycles
through its actions.

There is no way that two 500lb pushes will lift a 1000lb bucket in a
loader. Not even near the mark. What will probably happen is that with
the pump you are using in your calcs, you will need 3 times the ram
area - volume and get the 10 seconds' lift I want you to get above
G.

For instance I have a loader that I did some calcs for. The crowd
cylinders are able to do 21 tonne. The bucket tip actually comes to
about 7 tonne....at the best angle. This constantly changes as the
bucket moves. The Lift rams are 32 tonne. The lift theoretically is
about 6.25 tonne, again at the max situation, which continually
changes....and yes I _can_ lift the back of the bloody loader off the
ground!

Immediately the system changes from that best angle, it all goes
haywire, in both directions. You don't want to get the load halfway
up, and then find that you simply cannot lift any further.

You will also be surprised at eh length of ram needed to do a job,
even with all the mech disadvantage that hydraulics allows.

In all of this, remember that most tractors are not designed for
really heavy loads at the front. When you hang the bucket out there,
allow for the moment of arm of the weight, especially when driving
around and going over bumps. loaders wreck tractor front ends.

Are you going to make the bucket self levelling? That's law here,
because a few guys have dropped things on their heads as they raise
the load.

etc.

See if there are any plans on the net, or buy secondhand. Believe me,
making one from scratch, the excitement could be only _starting_ when
you have finished the loader.

While you may well be able to work out all the answers, the hardest
part is knowing all the questions.

And I am not even very good with hydraulic circuits in practice,
although the _theory_ is not that difficult.
************************************************** ** sorry
remove ns from my header address to reply via email

Spike....Spike? Hello?

don schad wrote:
Hi all,

Thanks for all the help/suggestions. It's very much appreciated.

I'll take the liberty to ask another question while we are he

There has been a lot of talk about having things sized properly such that
the system is controllable. Is proper sizing just a question of making some
assumptions and doing the math?
For example, lets say that I wanted the loader to go from the ground to the
full-up position in 3 seconds (is this too fast? too slow?).
Assuming:

Two hydraulic cylinders with a bore of 2", and a stroke of 14" to go from
down to full up.
3 seconds to extend ram 14"

To compute flow:
Speed (in/min) = flow (in3/min) / area (in2)
flow = speed (in/min) * area(in2) = 14"/0.05min * 3.141in2 = 880in3/min *
1g/260in3 = 3.4gpm
and since we have two cylinders, we need 6.8gpm?

This estimate seems to be reasonable based on what I have seen for other
loaders regarding pump size. Is this (basically) all there is to it? And
from there should I pick the lowest pressure which will (a) operate all the
parts and (b) give me the force which I need to do what I want? So if I
want to have the loader capacity be 1000#, I would have two cylinders which
could produce (minimally, since I guess there is geometry to consider and
the loss of usable lifting force - haven't gotten there yet ) 500# each
at a given PSI (seems like 1500 is the lowest common on, and this will
produce a force 500#)?

Easy...so what am I missing?

As always, thanks a lot for your help.

don


Hi Don
I think Nick had a lot of sound points well worth listening to . Common
Hydralic systems these days tend to run from 2500 to 4000 PSI . The rams
, pump , controls and hoses all have to match the maximum setting to
be safe . This is controled by a relief valve somewhere in the system .
Most controls have stepped spools , this allows you to feather them ,
but not all have this . For a loader you will want to be sure you get
this feature . The speed you mentioned , well as others have posted I
would say that is too fast . I might have missed it but you do not say
what tractor this is for . A loader capable of lifting 1000 lbs plus the
weight of the loader hanging out front of everthing is a lot . You
should call up a dealer and ask them what size loader this tractor is
rated for . You also have to be able to steer it after the loader is on
it . Will your steering take it ? I mention this as I have a tractor
with a factory loader that snapped the front spindles off . Yep the
engineers got it wrong . It is a real jolt to the heart when that
happens driving with a loaded bucket . Good reminder to carry the load
low to the ground which I wasn't at the time . Hey factory system has to
be safe right ? ha ha . I will point out that this little 25HP tractor
has a foolishly wide bucket on it . Maybe it would be ok lifting saw
dust or snow but anything else is more then the tractor can handle .If
you can find the same model tractor with a loader it would be well worth
trying to copy . Might save yourself a lot of grief down the road .
there are lots of companies that sell aftermarket loaders . Phone one
and ask them what they recomend for your tractor . At least you would
know what limits you should be planning for .
Ken Cutt

On Fri, 30 Jan 2004 22:45:05 GMT, Larry Jaques
vaguely proposed a theory
.......and in reply I say!:


Probably

??????

too fast. Add in calcs for mass/velocity/stress. With
a load, your 3-second rate would probably make your loader do
a reverse wheelie before bouncing back and dropping the load
on your head. You're building a loader, not a trebuchet, right?


Sez exactly what I envisaged an of course said in more words. G
************************************************** ** sorry
remove ns from my header address to reply via email

Spike....Spike? Hello?

On Sun, 01 Feb 2004 07:22:22 +0800, Old Nick
brought forth from the murky depths:

On Fri, 30 Jan 2004 22:45:05 GMT, Larry Jaques
vaguely proposed a theory
......and in reply I say!:


Probably

??????

Wull, if he just lifted bunny rabbits that fast...


too fast. Add in calcs for mass/velocity/stress. With
a load, your 3-second rate would probably make your loader do
a reverse wheelie before bouncing back and dropping the load
on your head. You're building a loader, not a trebuchet, right?


Sez exactly what I envisaged an of course said in more words. G

Just a few more words. Well done, Nick.


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On Sat, 31 Jan 2004 03:00:46 -0800, Ken Cutt
vaguely proposed a theory
.......and in reply I say!:

I actually have a bucket and arms from an old bobcat lying around.
When I mentioned in machinery circles that I was thinking of fitting
them to my tractor, some guy said "Well, I hope you've got the
geometry right" Naturally I said yes. Then I started to think about it
all......

It's a fascinating idea, but quite a project, and with
expensive/dangerous consequences if done wrongly. I shudder to think
waht would happen if a loader arm let go while I was sitting in the
tractor, because a pin bent or broke.

Your mention of steering rings a bell, Ken. My little Zetor has no
power steering. It would have been useless with a loader anyway.

It must have been something to have the fron drop with a full load. I
have losta wheel, with just a plough on the back and that was alarming
enough.

Hi Don
I think Nick had a lot of sound points well worth listening to . Common
Hydralic systems these days tend to run from 2500 to 4000 PSI . The rams
, pump , controls and hoses all have to match the maximum setting to

snip
************************************************** ** sorry
remove ns from my header address to reply via email

Spike....Spike? Hello?

On Sun, 01 Feb 2004 03:05:00 GMT, Larry Jaques
vaguely proposed a theory
.......and in reply I say!:

On Sun, 01 Feb 2004 07:22:22 +0800, Old Nick
brought forth from the murky depths:

On Fri, 30 Jan 2004 22:45:05 GMT, Larry Jaques
vaguely proposed a theory
......and in reply I say!:


Probably

??????

Wull, if he just lifted bunny rabbits that fast...


Hmmmm...happens in Oz from time to time. :-

Question: How far can _your_ loader throw a bucket of rabbits? G

Sez exactly what I envisaged an of course said in more words. G

Just a few more words. Well done, Nick.

Been down that path. I really wanted to pound the message home. Guess
I felt strongly about it. Hydraulics make things look simple and easy
because they have so much bloody _power_, and that power coould do a
lot if it lets go.
************************************************** ** sorry
remove ns from my header address to reply via email

Spike....Spike? Hello?

On Mon, 02 Feb 2004 17:31:56 +0800, Old Nick
brought forth from the murky depths:

On Sun, 01 Feb 2004 03:05:00 GMT, Larry Jaques
Wull, if he just lifted bunny rabbits that fast...

Hmmmm...happens in Oz from time to time. :-

Question: How far can _your_ loader throw a bucket of rabbits? G

Loader? 0' But the trebuchet...


Sez exactly what I envisaged an of course said in more words. G

Just a few more words. Well done, Nick.

Been down that path. I really wanted to pound the message home. Guess
I felt strongly about it. Hydraulics make things look simple and easy
because they have so much bloody _power_, and that power coould do a
lot if it lets go.

Ayup. Bloody messy, that.


------
We're born hungry, wet, naked, and it gets worse from there.
- http://diversify.com Website Application Programming -

On 28 Jan 2004 06:45:19 -0800, (don schad)
vaguely proposed a theory
.......and in reply I say!:

So I am not a complet naysayer:

http://www.okdpm.com/catalog/product...olume_III.html

ARC WELDED PROJECTS Volume III
This book gives you the plans, material lists, and instructions for
67 Welding projects!

AGRICULTURAL EQUIPMENT:
Adjustable pruning stand, heavy duty hydraulic tillage markers, quick
hitch, portable feed lot, spring loaded gate for calf roping, cattle
cake feeder, sub soil ripper, sheep blocking stand, tractor scraper,
box scraper, **Construction of a Custom built front end loader**, barn
fan, PTO driven buzz saw, hydraulically operated ditching unit, 60
foot spray rig, flat bed truck three point PTO wire winder.

US$14.99

I have Vol II and the plans vary in depth and quality, bt there are a
lot of useful ideas in these books for the $$.



Hi all.

I am scheming to build a front-end loader for my tractor, and I have
been looking into hydraulics. I have a couple of pretty basic
questions which I have generated after reading various sources and
looking through the catalogs. Any help/insight into any of these
questions would be much appreciated.

First question regards spools for open-center systems. Some Army
literature talks about open-center spools versus tandem-center spools.
Assuming a 4way with lines T (tank), P (pump), A and B (ports to
cylinder) my understanding is that in neutral an "open center" spool
connects all ports (A,B and P) to the T (tank), such that there
wouldn't be any pressure to the cylinder (i.e. it is floating in
neutral). A tandem open-center spool (in neutral) connects P to T (so
it is just passing through the spool), and closes off A and B, holding
pressure in the A/B loop.

In the first case, a loader w/ an open-center as described would come
crashing down when you let off the controls, whereas the tandem would
hold it's position. Looking at the catalogs I haven't seen a
reference to a "tandem" spool, but I have seen "open-center with load
checks", and further reading suggests that load checks will hold the
cylinder in position.

So, is what I'm calling a tandem spool the same as an "open-center
with load checks"? Does a load check in a spool close off the lines
in neutral?

Second, if you have a spool that is rated for say 25GPM, will there be
any problem running it at a lower GPM? Say 12GPM or 5? Will it still
function properly/safely?

How is pressure controled in the system? Is it just a matter of
setting the relief/bypass values, and the lowest one will control the
pressure (although I guess this would depend on how it was plumbed)?
Most seem to say that they function from 1000psi to 3000psi - does
this mean I can make any combination of pressure/flow rate in the
system to achieive my goals or fit my pump/equipment?

What is the difference between a welded versus a tie rod cylinder?
Pros/cons?

Finally, in parallel spool decks is the flow simply divided between
the open spools, such that everything will work, but at a lower speed?
And pressure in all A/B lines is the same (so all spools get there
input from the P line)? In series is it that the flow out of one
spool feeds into another spool (so input is from the T line), and we
get a decrease in the pressure (with the same flow)?

Thanks in advance for your help. I appreciate any and all comments
and info.

don

************************************************** ** sorry
remove ns from my header address to reply via email

Spike....Spike? Hello?

Old Nick wrote:
On Sat, 31 Jan 2004 03:00:46 -0800, Ken Cutt
vaguely proposed a theory
......and in reply I say!:

I actually have a bucket and arms from an old bobcat lying around.
When I mentioned in machinery circles that I was thinking of fitting
them to my tractor, some guy said "Well, I hope you've got the
geometry right" Naturally I said yes. Then I started to think about it
all......

It's a fascinating idea, but quite a project, and with
expensive/dangerous consequences if done wrongly. I shudder to think
waht would happen if a loader arm let go while I was sitting in the
tractor, because a pin bent or broke.

Your mention of steering rings a bell, Ken. My little Zetor has no
power steering. It would have been useless with a loader anyway.

It must have been something to have the fron drop with a full load. I
have losta wheel, with just a plough on the back and that was alarming
enough.

Hi Nick
Well to be honest about losing the front end , it was all over by the
time it occured to me to get scared . Heart sure got going though . One
spindle broke and when it that side hit the ground the weight transfer
took out the other one . Called up a dealer who said new spindles would
be $800.00 a side and break again since it was a weakness of this model
.. This tractor is a 25 HP Satoh a make I would not recomend to anyone .
So made up my own for about a days labour and $200.00 . Still holding up
the tractor so guess the fix took , ;-) . On the other hand this tractor
is such junk it runs so few hours . Loaders are great but for most
people it is easier to live with " too small " then " too big " not to
mention safer . Me I am looking forward to bouncing a few grandkids on
my knee so tend to think a hell of alot more then I did when younger .
Ken Cutt

Old Nick wrote:
On Sat, 31 Jan 2004 03:00:46 -0800, Ken Cutt
vaguely proposed a theory
......and in reply I say!:

I actually have a bucket and arms from an old bobcat lying around.
When I mentioned in machinery circles that I was thinking of fitting
them to my tractor, some guy said "Well, I hope you've got the
geometry right" Naturally I said yes. Then I started to think about it
all......

It's a fascinating idea, but quite a project, and with
expensive/dangerous consequences if done wrongly. I shudder to think
waht would happen if a loader arm let go while I was sitting in the
tractor, because a pin bent or broke.

A bobcat is a lot different from a same-size farm tractor with a front-end
loader. I don't know much about farm tractors but I think the whole setup
is much different - how far out front the load is held, ratio of load
capacity to machine weight, and protection of the operator from the load
and/or equipment failure. Yes grafting a bobcat loader onto tractor would
require some thought.

A bobcat holds the load close in and when fully raised the load is literally
right on top of the operator. Mine is 34 years old and even then it came
stock with a roll cage with steel plate on top, a 1/4" welded-wire cage on
the sides and a seat belt. Even with the top, raising a full bucket
without tilting it forward dumps it on your knees from 11' up. Without the
roll cage any number of mechanical failures would make sausage of the
operator.

The bobcat can lift about 2000 lbs close-in in the bucket and about 1000 out
on forks, limited by balance not power. The machine weighs about 4000 lbs
and is counterweighted on the rear to the point of being unsafe to operate
with the front attachment removed. I routinely operate it right at the
tipping limit, where the back wheels aren't doing much of anything, and all
the weight is on the front spindles, 3000 lbs dead load plus considerable
shock load. The spindles are approx. 2" solid steel.

Aside, it's a great shop tool.

Bob

Or you can order it for half the price he

https://ssl.lincolnelectric.com/lincoln/spmount/store.asp?PID=16&cat=7

Cheers,

Kelley

On Tue, 03 Feb 2004 06:33:25 +0800, Old Nick
wrote:

On 28 Jan 2004 06:45:19 -0800, (don schad)
vaguely proposed a theory
......and in reply I say!:

So I am not a complet naysayer:

http://www.okdpm.com/catalog/product...olume_III.html

ARC WELDED PROJECTS Volume III
This book gives you the plans, material lists, and instructions for
67 Welding projects!

AGRICULTURAL EQUIPMENT:
Adjustable pruning stand, heavy duty hydraulic tillage markers, quick
hitch, portable feed lot, spring loaded gate for calf roping, cattle
cake feeder, sub soil ripper, sheep blocking stand, tractor scraper,
box scraper, **Construction of a Custom built front end loader**, barn
fan, PTO driven buzz saw, hydraulically operated ditching unit, 60
foot spray rig, flat bed truck three point PTO wire winder.

US$14.99

I have Vol II and the plans vary in depth and quality, bt there are a
lot of useful ideas in these books for the $$.



Hi all.

I am scheming to build a front-end loader for my tractor, and I have
been looking into hydraulics. I have a couple of pretty basic
questions which I have generated after reading various sources and
looking through the catalogs. Any help/insight into any of these
questions would be much appreciated.

First question regards spools for open-center systems. Some Army
literature talks about open-center spools versus tandem-center spools.
Assuming a 4way with lines T (tank), P (pump), A and B (ports to
cylinder) my understanding is that in neutral an "open center" spool
connects all ports (A,B and P) to the T (tank), such that there
wouldn't be any pressure to the cylinder (i.e. it is floating in
neutral). A tandem open-center spool (in neutral) connects P to T (so
it is just passing through the spool), and closes off A and B, holding
pressure in the A/B loop.

In the first case, a loader w/ an open-center as described would come
crashing down when you let off the controls, whereas the tandem would
hold it's position. Looking at the catalogs I haven't seen a
reference to a "tandem" spool, but I have seen "open-center with load
checks", and further reading suggests that load checks will hold the
cylinder in position.

So, is what I'm calling a tandem spool the same as an "open-center
with load checks"? Does a load check in a spool close off the lines
in neutral?

Second, if you have a spool that is rated for say 25GPM, will there be
any problem running it at a lower GPM? Say 12GPM or 5? Will it still
function properly/safely?

How is pressure controled in the system? Is it just a matter of
setting the relief/bypass values, and the lowest one will control the
pressure (although I guess this would depend on how it was plumbed)?
Most seem to say that they function from 1000psi to 3000psi - does
this mean I can make any combination of pressure/flow rate in the
system to achieive my goals or fit my pump/equipment?

What is the difference between a welded versus a tie rod cylinder?
Pros/cons?

Finally, in parallel spool decks is the flow simply divided between
the open spools, such that everything will work, but at a lower speed?
And pressure in all A/B lines is the same (so all spools get there
input from the P line)? In series is it that the flow out of one
spool feeds into another spool (so input is from the T line), and we
get a decrease in the pressure (with the same flow)?

Thanks in advance for your help. I appreciate any and all comments
and info.

don

************************************************* *** sorry
remove ns from my header address to reply via email

Spike....Spike? Hello?

On Tue, 03 Feb 2004 01:20:59 -0800, Ken Cutt
vaguely proposed a theory
.......and in reply I say!:


Hi Nick
Well to be honest about losing the front end , it was all over by the
time it occured to me to get scared . Heart sure got going though.

Ah! Like falling off a motorcycle! G

One
spindle broke and when it that side hit the ground the weight transfer
took out the other one . Called up a dealer who said new spindles would
be $800.00 a side and break again since it was a weakness of this model

hmmm....right good PR! G?

. This tractor is a 25 HP Satoh a make I would not recomend to anyone .

Taken into consideration.

So made up my own for about a days labour and $200.00 . Still holding up
the tractor so guess the fix took , ;-) . On the other hand this tractor
is such junk it runs so few hours . Loaders are great but for most
people it is easier to live with " too small " then " too big " not to
mention safer .

But so tempting to get that extra bit of dirt!

Me I am looking forward to bouncing a few grandkids on
my knee so tend to think a hell of alot more then I did when younger .

Yeah. I stopped riding motorcycles.

Ken Cutt

************************************************** ** sorry
remove ns from my header address to reply via email

Spike....Spike? Hello?

On Tue, 03 Feb 2004 17:36:20 GMT, "Toolbert"
vaguely proposed a theory
.......and in reply I say!:


A bobcat is a lot different from a same-size farm tractor with a front-end
loader.

I agree. The tractor was actually physically quite a bit larger than
the bobcat. But because the bobcat has its anchor points right at the
back, and up on arms, for lift height, the arms fitted really well
around the tractor, as if for a normal tractor loader.

I take all you points about dumping the load in your lap. My silliest
actio on a backhoe was to put some pipe across the arms behind the
bucket to simply carry it from a to b. When I lifted the arms I was
glad the pipe was only light! A lucky lesson.
************************************************** ** sorry
remove ns from my header address to reply via email

Spike....Spike? Hello?

On Tue, 03 Feb 2004 18:45:37 GMT, Kelley Mascher
vaguely proposed a theory
.......and in reply I say!:


Or you can order it for half the price he

https://ssl.lincolnelectric.com/lincoln/spmount/store.asp?PID=16&cat=7

Cheers,

OK. Fine. I was surprised at the price, compared to in the past. Mind
you in Oz I paid $40 for VolII, even from Lincoln themselves! Bah!
************************************************** ** sorry
remove ns from my header address to reply via email

Spike....Spike? Hello?

Old Nick wrote:



But so tempting to get that extra bit of dirt!


Me I am looking forward to bouncing a few grandkids on my knee so
tend to think a hell of alot more then I did when younger .


Yeah. I stopped riding motorcycles.


Ken Cutt


Well really I use a 70 HP with a loader to work with . But it will not
go inside the barns :-( . No matter how big the loader you always
want/wish for more . Gave away my old racing bikes summer before last ,
:-( . Nothing quite like a bike but when on one I for some reason still
seem to think I am 20 . Oh well always the memories .
Ken Cutt