Metalworking (rec.crafts.metalworking) Discuss various aspects of working with metal, such as machining, welding, metal joining, screwing, casting, hardening/tempering, blacksmithing/forging, spinning and hammer work, sheet metal work.

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Default Alternatives to aluminum tube

More design questions:

I need a stick-like thing, about 30 inches long, to go from a pivot
point to a little electric motor. It needs to be moderately rigid,
light and inexpensive in lots of 50 each or so. It would also be quite
nice if it's moderately attractive -- mill finish aluminum without too
many scuff marks is just fine for this. Prettier is better.

I'm thinking that thin-wall aluminum* tube of about 5/8" diameter will
work well, and I'm getting ready to be shocked once again by how much
things cost these days. While I'm waiting for quotes, I thought I'd
solicit the group for suggestions.

Fiberglass? Carbon fiber? Phenolic? Other plastics? Titanium**?
Extra thin-wall steel? Balsa wood comes to mind, but while it is low
tech I suspect it'll cost more than aluminum. Cooked spaghetti is too
limp, and uncooked is too brittle.

Anyone have suggestions? Do you have supplier names to go with your
suggestions?

* Alloy isn't terribly important. Even dead soft would work, although
harder would be better.

** OK, maybe it's more expensive than aluminum.

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com

Do you need to implement control loops in software?
"Applied Control Theory for Embedded Systems" gives you just what it says.
See details at http://www.wescottdesign.com/actfes/actfes.html
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Default Alternatives to aluminum tube


"Tim Wescott" wrote in message
...
More design questions:

I need a stick-like thing, about 30 inches long, to go from a pivot point
to a little electric motor. It needs to be moderately rigid, light and
inexpensive in lots of 50 each or so. It would also be quite nice if it's
moderately attractive -- mill finish aluminum without too many scuff marks
is just fine for this. Prettier is better.

I'm thinking that thin-wall aluminum* tube of about 5/8" diameter will
work well, and I'm getting ready to be shocked once again by how much
things cost these days. While I'm waiting for quotes, I thought I'd
solicit the group for suggestions.

Fiberglass? Carbon fiber? Phenolic? Other plastics? Titanium**? Extra
thin-wall steel? Balsa wood comes to mind, but while it is low tech I
suspect it'll cost more than aluminum. Cooked spaghetti is too limp, and
uncooked is too brittle.

Anyone have suggestions? Do you have supplier names to go with your
suggestions?

* Alloy isn't terribly important. Even dead soft would work, although
harder would be better.

** OK, maybe it's more expensive than aluminum.


pvc pipe? venetian blind replacement rods? wooden dowels? you don't give a
lot of specs on size or what kinds of forces it has to withstand, whether it
has to be weatherproof, etc.


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Default Alternatives to aluminum tube

On Mar 11, 10:35 am, Tim Wescott wrote:
More design questions:

I need a stick-like thing, about 30 inches long, to go from a pivot
point to a little electric motor. It needs to be moderately rigid,
light and inexpensive in lots of 50 each or so. It would also be quite
nice if it's moderately attractive -- mill finish aluminum without too
many scuff marks is just fine for this. Prettier is better.

I'm thinking that thin-wall aluminum* tube of about 5/8" diameter will
work well, and I'm getting ready to be shocked once again by how much
things cost these days. While I'm waiting for quotes, I thought I'd
solicit the group for suggestions.

Fiberglass? Carbon fiber? Phenolic? Other plastics? Titanium**?
Extra thin-wall steel? Balsa wood comes to mind, but while it is low
tech I suspect it'll cost more than aluminum. Cooked spaghetti is too
limp, and uncooked is too brittle.

Anyone have suggestions? Do you have supplier names to go with your
suggestions?

* Alloy isn't terribly important. Even dead soft would work, although
harder would be better.

** OK, maybe it's more expensive than aluminum.

--

Tim Wescott
Wescott Design Serviceshttp://www.wescottdesign.com

Do you need to implement control loops in software?
"Applied Control Theory for Embedded Systems" gives you just what it says.
See details athttp://www.wescottdesign.com/actfes/actfes.html


Hi, Tim.
Should I say "here we go again!"? First, how will it be fastened to
your device? Will it be twisted, pushed or pulled? Will it matter if
it is solid or must it be a tube?

The first thing that comes to mind is using a piece of the white resin
electric fence post available in your local farm store. These are
either 3 or 4 ft. long and about 1/2 inch or perhaps 3/8 inch in
diameter. We cut pieces off to use in a customer's product. I am not
sure of what it is used for, but sometimes I am sent to buy another
stick or two. They are quite stiff, but light.

If you want to look at carbon fiber tubes or fiberglass tubes, go
check out an archery store. They have both for the local arrow makers.
They might even cut them to the length you need.

The most critical factor with tube is crushing it when you make
attachments.


Good luck!

Paul Drahn, President
Jodeco, Inc.
Redmond, OR
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Default Alternatives to aluminum tube

On Tue, 11 Mar 2008 11:01:30 -0700, charlie wrote:

"Tim Wescott" wrote in message
...
More design questions:

I need a stick-like thing, about 30 inches long, to go from a pivot
point to a little electric motor. It needs to be moderately rigid,
light and inexpensive in lots of 50 each or so. It would also be quite
nice if it's moderately attractive -- mill finish aluminum without too
many scuff marks is just fine for this. Prettier is better.

I'm thinking that thin-wall aluminum* tube of about 5/8" diameter will
work well, and I'm getting ready to be shocked once again by how much
things cost these days. While I'm waiting for quotes, I thought I'd
solicit the group for suggestions.

Fiberglass? Carbon fiber? Phenolic? Other plastics? Titanium**?
Extra thin-wall steel? Balsa wood comes to mind, but while it is low
tech I suspect it'll cost more than aluminum. Cooked spaghetti is too
limp, and uncooked is too brittle.

Anyone have suggestions? Do you have supplier names to go with your
suggestions?

* Alloy isn't terribly important. Even dead soft would work, although
harder would be better.

** OK, maybe it's more expensive than aluminum.


pvc pipe? venetian blind replacement rods? wooden dowels? you don't give
a lot of specs on size or what kinds of forces it has to withstand,
whether it has to be weatherproof, etc.


Of course I'm being vague! It wouldn't be a proper posting if I left
everything in!

It's for a table-top thing. It's only expected to work in a shirt-sleeve
environment. The arm's job is to hold a lightweight motor (2oz or so) a
good length away from a counterweight. The motor runs a fan, and the
goal of the assembly is to servo the arm position to a given spot (it's
for control systems training).

A 30-inch piece of 5/8 OD 3003 tubing with a 0.04" wall should weigh
about 4 ounces, if I got my numbers right. To keep the counterweight to
a reasonable size and weight I'd like to investigate things of comparable
weights.

A 5/8 inch tube is a good size to mount the motor -- I can fish-mouth the
end of the tube, drill for a peg, and hold the motor on with elastic. If
I get paranoid about safety I can mount a little ducted fan onto the end
of the tube, screwing into a plug or a large, threaded peg. Down to 1/2
inch is probably doable, up to 1 inch is fine as long as the weight
doesn't grow by more than a couple of ounces.

PVC water pipe is probably much too heavy. Thin-wall PVC tube may work,
but it may have the same problems as uncooked spaghetti. Venitian blind
replacement rods may work, although I'd like tubes for the motor wiring
to travel inside of, and I'd be a bit worried about brittleness. Ditto
dowels, plus there's a problem of looks.

Thanks for the suggestions -- I will consider them.

--
Tim Wescott
Control systems and communications consulting
http://www.wescottdesign.com

Need to learn how to apply control theory in your embedded system?
"Applied Control Theory for Embedded Systems" by Tim Wescott
Elsevier/Newnes, http://www.wescottdesign.com/actfes/actfes.html
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Default Alternatives to aluminum tube

On Tue, 11 Mar 2008 11:01:30 -0700, charlie wrote:

"Tim Wescott" wrote in message
...
More design questions:

I need a stick-like thing, about 30 inches long, to go from a pivot
point to a little electric motor. It needs to be moderately rigid,
light and inexpensive in lots of 50 each or so. It would also be quite
nice if it's moderately attractive -- mill finish aluminum without too
many scuff marks is just fine for this. Prettier is better.

I'm thinking that thin-wall aluminum* tube of about 5/8" diameter will
work well, and I'm getting ready to be shocked once again by how much
things cost these days. While I'm waiting for quotes, I thought I'd
solicit the group for suggestions.

Fiberglass? Carbon fiber? Phenolic? Other plastics? Titanium**?
Extra thin-wall steel? Balsa wood comes to mind, but while it is low
tech I suspect it'll cost more than aluminum. Cooked spaghetti is too
limp, and uncooked is too brittle.

Anyone have suggestions? Do you have supplier names to go with your
suggestions?

* Alloy isn't terribly important. Even dead soft would work, although
harder would be better.

** OK, maybe it's more expensive than aluminum.


pvc pipe? venetian blind replacement rods? wooden dowels? you don't give
a lot of specs on size or what kinds of forces it has to withstand,
whether it has to be weatherproof, etc.


Your "venetian blind rods" turned into "polycarbonate tube".

McMaster sells polycarbonate tube -- they have some 1/8 wall 5/8 OD tube
that should be OK, if a bit more brittle than I'd really like. They want
less than $2.50 a foot, and I should be able to get it for much less
elsewhere if I dig. I'll see what else they have.

Thanks.

--
Tim Wescott
Control systems and communications consulting
http://www.wescottdesign.com

Need to learn how to apply control theory in your embedded system?
"Applied Control Theory for Embedded Systems" by Tim Wescott
Elsevier/Newnes, http://www.wescottdesign.com/actfes/actfes.html


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Default Alternatives to aluminum tube

On Tue, 11 Mar 2008 11:16:23 -0700, pdrahn wrote:

On Mar 11, 10:35 am, Tim Wescott wrote:
More design questions:

I need a stick-like thing, about 30 inches long, to go from a pivot
point to a little electric motor. It needs to be moderately rigid,
light and inexpensive in lots of 50 each or so. It would also be quite
nice if it's moderately attractive -- mill finish aluminum without too
many scuff marks is just fine for this. Prettier is better.

I'm thinking that thin-wall aluminum* tube of about 5/8" diameter will
work well, and I'm getting ready to be shocked once again by how much
things cost these days. While I'm waiting for quotes, I thought I'd
solicit the group for suggestions.

Fiberglass? Carbon fiber? Phenolic? Other plastics? Titanium**?
Extra thin-wall steel? Balsa wood comes to mind, but while it is low
tech I suspect it'll cost more than aluminum. Cooked spaghetti is too
limp, and uncooked is too brittle.

Anyone have suggestions? Do you have supplier names to go with your
suggestions?

* Alloy isn't terribly important. Even dead soft would work, although
harder would be better.

** OK, maybe it's more expensive than aluminum.

--

Tim Wescott
Wescott Design Serviceshttp://www.wescottdesign.com

Do you need to implement control loops in software? "Applied Control
Theory for Embedded Systems" gives you just what it says. See details
athttp://www.wescottdesign.com/actfes/actfes.html


Hi, Tim.
Should I say "here we go again!"? First, how will it be fastened to your
device? Will it be twisted, pushed or pulled? Will it matter if it is
solid or must it be a tube?


Asking dumb questions helps me think through all the details.

It'll (most likely) be glued into a hole (in a counterweight) on one end,
and either have a motor/propeller assembly held to the other with an
elastic on a peg, or a little ducted fan unit held to the other with a
tapped cross-peg or an expandable plug (if I can find one).

In normal use uncooked spaghetti would work, it mostly needs strength to
avoid damage during handling and while the student is learning about
stability and overshoot.

The first thing that comes to mind is using a piece of the white resin
electric fence post available in your local farm store. These are either
3 or 4 ft. long and about 1/2 inch or perhaps 3/8 inch in diameter. We
cut pieces off to use in a customer's product. I am not sure of what it
is used for, but sometimes I am sent to buy another stick or two. They
are quite stiff, but light.


I'll take a look the next time I'm at Wilco's.

balance snipped

--
Tim Wescott
Control systems and communications consulting
http://www.wescottdesign.com

Need to learn how to apply control theory in your embedded system?
"Applied Control Theory for Embedded Systems" by Tim Wescott
Elsevier/Newnes, http://www.wescottdesign.com/actfes/actfes.html
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Default Alternatives to aluminum tube

"Tim Wescott" wrote in message
...
More design questions:

I need a stick-like thing, about 30 inches long, to go from a pivot point
to a little electric motor. It needs to be moderately rigid,

...

Unless you've ruled out aluminum tubes completely, try

http://www.texastowers.com/aluminum.htm

- Pretty good properties

- UPSable lengths.

- Cheaper than a lot of other stuff.

- Adjacent sizes in the list telescope too.

- If you insist on 6061, google for OnlineMetals.com

Hth,
Fred


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Tim Wescott wrote:

Your "venetian blind rods" turned into "polycarbonate tube".

McMaster sells polycarbonate tube -- they have some 1/8 wall 5/8 OD tube
that should be OK, if a bit more brittle than I'd really like. They want
less than $2.50 a foot, and I should be able to get it for much less
elsewhere if I dig. I'll see what else they have.


You can get 5/8" hardwood dowels for
less than $.50/foot.

http://www.hobbylinc.com/htm/mid/mid7910.htm
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On Mar 11, 11:40 am, Tim Wescott wrote:
On Tue, 11 Mar 2008 11:16:23 -0700, pdrahn wrote:
On Mar 11, 10:35 am, Tim Wescott wrote:
More design questions:


I need a stick-like thing, about 30 inches long, to go from a pivot
point to a little electric motor. It needs to be moderately rigid,
light and inexpensive in lots of 50 each or so. It would also be quite
nice if it's moderately attractive -- mill finish aluminum without too
many scuff marks is just fine for this. Prettier is better.



This seems to be an ideal application for virtual reality. That way
your device could be made from smoke and mirrors!!!!! As stiff as you
want and NO weight!

Sorry, just had to suggest this, but know it's not practical for the
few you are designing for. Would be fun, however.

Paul

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On Mar 11, 10:35*am, Tim Wescott wrote:
More design questions:

I need a stick-like thing, about 30 inches long, to go from a pivot
point to a little electric motor. *It needs to be moderately rigid,
light and inexpensive in lots of 50 each or so. *It would also be quite
nice if it's moderately attractive


How about a hardwood dowel? Easy to find in craft shops or
woodwork places, diameters 1/4" to 3/4", and with some effort
(sand smooth, wax, wrap with a string and friction-polish) you can
get nice surface appearance.

A length of bamboo could do, too, but unless you have a weedy patch
of the stuff in your backyard, it's gonna be hard to find a source
of short sticks.


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I'd like tubes for the motor wiring
to travel inside of


Just a thought, Tim.

Several years ago we needed some very light, thin and very flexible
wire to connect sensors on the pick-up-head of an old pick-and-place
machine. The wire was subject to a lot of torque as the head rotated
to the correct theta to place the part. Original wire was unobtanium.

I found a source of two conductor litz wire on Ebay. It was from
England and was for hi-fi record pick-up heads. I think I ordered it
from them a couple of times. It had one copper wire and one gold wire.
The copper was insulated and the gold was twisted around the copper.
The guy sold it by the meter and a meter was good for a couple of
years for us. Something like this would power your fan motor and not
add much weight to the arm. I am sure this will be a question in the
near future .

Paul
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On Tue, 11 Mar 2008 13:29:43 -0500, Tim Wescott
wrote:

Your "venetian blind rods" turned into "polycarbonate tube".

McMaster sells polycarbonate tube -- they have some 1/8 wall 5/8 OD tube
that should be OK, if a bit more brittle than I'd really like. They want
less than $2.50 a foot, and I should be able to get it for much less
elsewhere if I dig. I'll see what else they have.

1/2" CPVC pipe might work. It is readily available and not very
expensive.
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Default Alternatives to aluminum tube

On 2008-03-11, Tim Wescott wrote:
More design questions:

I need a stick-like thing, about 30 inches long, to go from a pivot
point to a little electric motor. It needs to be moderately rigid,
light and inexpensive in lots of 50 each or so. It would also be quite
nice if it's moderately attractive -- mill finish aluminum without too
many scuff marks is just fine for this. Prettier is better.


Hmm ... does it need to be more rigid in one direction of
rotation than the other (e.g. more load with clockwise rotation than
with counter-clockwise?) If so, then either carbon fiber or fiberglass,
laid with the right fiber orientation would probably be stronger. (Note
that this is presuming that you are transferring torque through the tube
from the motor's shaft.

If you need it stronger in compression or tension, then other
choices might be better -- though tension would do well with either
fiberglass or carbon fiber.

I'm thinking that thin-wall aluminum* tube of about 5/8" diameter will
work well, and I'm getting ready to be shocked once again by how much
things cost these days. While I'm waiting for quotes, I thought I'd
solicit the group for suggestions.


Thin wall? Is it being used for torque (as I suggested above)
or just to hold a motor tensioned against the belt or gears?

Fiberglass? Carbon fiber? Phenolic? Other plastics? Titanium**?
Extra thin-wall steel? Balsa wood comes to mind, but while it is low
tech I suspect it'll cost more than aluminum. Cooked spaghetti is too
limp, and uncooked is too brittle.


Define how you are planning to use it, and perhaps we can come
up with better selections.

Anyone have suggestions? Do you have supplier names to go with your
suggestions?

* Alloy isn't terribly important. Even dead soft would work, although
harder would be better.

** OK, maybe it's more expensive than aluminum.


Especially if it needs any working to make it the right shape.

Enjoy,
DoN.

--
Email: | Voice (all times): (703) 938-4564
(too) near Washington D.C. | http://www.d-and-d.com/dnichols/DoN.html
--- Black Holes are where God is dividing by zero ---
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DoN. Nichols wrote:
On 2008-03-11, Tim Wescott wrote:
More design questions:

I need a stick-like thing, about 30 inches long, to go from a pivot
point to a little electric motor. It needs to be moderately rigid,
light and inexpensive in lots of 50 each or so. It would also be quite
nice if it's moderately attractive -- mill finish aluminum without too
many scuff marks is just fine for this. Prettier is better.


Hmm ... does it need to be more rigid in one direction of
rotation than the other (e.g. more load with clockwise rotation than
with counter-clockwise?) If so, then either carbon fiber or fiberglass,
laid with the right fiber orientation would probably be stronger. (Note
that this is presuming that you are transferring torque through the tube
from the motor's shaft.

If you need it stronger in compression or tension, then other
choices might be better -- though tension would do well with either
fiberglass or carbon fiber.

I'm thinking that thin-wall aluminum* tube of about 5/8" diameter will
work well, and I'm getting ready to be shocked once again by how much
things cost these days. While I'm waiting for quotes, I thought I'd
solicit the group for suggestions.


Thin wall? Is it being used for torque (as I suggested above)
or just to hold a motor tensioned against the belt or gears?


Neither. The tube is pivoted on a horizontal axis, the motor has a
propeller on it that turns the assembly on the pivot. The only working
load that the tube has is the weight of the motor and any transitory
loads from the thrust of the propeller while it is accelerating the
assembly.

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com

Do you need to implement control loops in software?
"Applied Control Theory for Embedded Systems" gives you just what it says.
See details at http://www.wescottdesign.com/actfes/actfes.html
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On Mar 11, 3:05*pm, Jim Stewart wrote:

You can get 5/8" hardwood dowels for
less than $.50/foot.


Why bother, when you can get sticks for free?

John Martin


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John Martin wrote:
On Mar 11, 3:05 pm, Jim Stewart wrote:
You can get 5/8" hardwood dowels for
less than $.50/foot.


Why bother, when you can get sticks for free?

John Martin


So I'm going to be including the cost of these things (A $x49 value!) in
a high-end seminar, and you want me to put it together with stuff I find
in the woods behind my house?

Hmm.

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com

Do you need to implement control loops in software?
"Applied Control Theory for Embedded Systems" gives you just what it says.
See details at http://www.wescottdesign.com/actfes/actfes.html
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On Tue, 11 Mar 2008 14:32:16 -0700, pdrahn wrote:

I'd like tubes for the motor wiring
to travel inside of


Just a thought, Tim.

Several years ago we needed some very light, thin and very flexible wire
to connect sensors on the pick-up-head of an old pick-and-place machine.
The wire was subject to a lot of torque as the head rotated to the
correct theta to place the part. Original wire was unobtanium.

I found a source of two conductor litz wire on Ebay. It was from England
and was for hi-fi record pick-up heads. I think I ordered it from them a
couple of times. It had one copper wire and one gold wire. The copper
was insulated and the gold was twisted around the copper. The guy sold
it by the meter and a meter was good for a couple of years for us.
Something like this would power your fan motor and not add much weight
to the arm. I am sure this will be a question in the near future .

Paul


I actually have the circuitry, wiring and software issues well in hand.
I even know where I'll be getting motors and propellers.

Hard to believe, I know, yet it's true.

--
Tim Wescott
Control systems and communications consulting
http://www.wescottdesign.com

Need to learn how to apply control theory in your embedded system?
"Applied Control Theory for Embedded Systems" by Tim Wescott
Elsevier/Newnes, http://www.wescottdesign.com/actfes/actfes.html
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On Tue, 11 Mar 2008 13:51:17 -0700, pdrahn wrote:

On Mar 11, 11:40 am, Tim Wescott wrote:
On Tue, 11 Mar 2008 11:16:23 -0700, pdrahn wrote:
On Mar 11, 10:35 am, Tim Wescott wrote:
More design questions:


I need a stick-like thing, about 30 inches long, to go from a pivot
point to a little electric motor. It needs to be moderately rigid,
light and inexpensive in lots of 50 each or so. It would also be
quite nice if it's moderately attractive -- mill finish aluminum
without too many scuff marks is just fine for this. Prettier is
better.



This seems to be an ideal application for virtual reality. That way your
device could be made from smoke and mirrors!!!!! As stiff as you want
and NO weight!

Sorry, just had to suggest this, but know it's not practical for the few
you are designing for. Would be fun, however.

Paul


I could 'make' these things as simulations a heck of a lot easier than I
can make the physical article. But control systems implementation is
often very hands-on; having a sample of the real thing, in a way that's
fun, slow enough to see what's going on, noisy enough to get a visceral
feel for it, and the right size to grab, is the right thing to accompany
what I'm doing.

--
Tim Wescott
Control systems and communications consulting
http://www.wescottdesign.com

Need to learn how to apply control theory in your embedded system?
"Applied Control Theory for Embedded Systems" by Tim Wescott
Elsevier/Newnes, http://www.wescottdesign.com/actfes/actfes.html
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On Tue, 11 Mar 2008 14:09:37 -0700 (PDT), whit3rd
wrote:

On Mar 11, 10:35*am, Tim Wescott wrote:
More design questions:

I need a stick-like thing, about 30 inches long, to go from a pivot
point to a little electric motor. *It needs to be moderately rigid,
light and inexpensive in lots of 50 each or so. *It would also be quite
nice if it's moderately attractive


How about a hardwood dowel? Easy to find in craft shops or
woodwork places, diameters 1/4" to 3/4", and with some effort
(sand smooth, wax, wrap with a string and friction-polish) you can
get nice surface appearance.

A length of bamboo could do, too, but unless you have a weedy patch
of the stuff in your backyard, it's gonna be hard to find a source
of short sticks.

Dollar store bamboo plant stakes @ 12/$1
Gerry :-)}
London, Canada
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Tim Wescott wrote:
More design questions:

I need a stick-like thing, about 30 inches long, to go from a pivot
point to a little electric motor. It needs to be moderately rigid,
light and inexpensive in lots of 50 each or so. It would also be quite
nice if it's moderately attractive -- mill finish aluminum without too
many scuff marks is just fine for this. Prettier is better.

I'm thinking that thin-wall aluminum* tube of about 5/8" diameter will
work well, and I'm getting ready to be shocked once again by how much
things cost these days. While I'm waiting for quotes, I thought I'd
solicit the group for suggestions.

Fiberglass? Carbon fiber? Phenolic? Other plastics? Titanium**?
Extra thin-wall steel? Balsa wood comes to mind, but while it is low
tech I suspect it'll cost more than aluminum. Cooked spaghetti is too
limp, and uncooked is too brittle.

Anyone have suggestions? Do you have supplier names to go with your
suggestions?

* Alloy isn't terribly important. Even dead soft would work, although
harder would be better.

** OK, maybe it's more expensive than aluminum.

How about economy grade hunting arrow shafting? I know its smaller than
5/8 but unless your motor weights a couple pounds or something it should
be fine. It's fairly thick walled so drill and tap each end to
facilitate attaching the counterweight and motor.

Regards
Paul



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Default Alternatives to aluminum tube

FRP would be good and light weight




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Default Alternatives to aluminum tube

On Tue, 11 Mar 2008 20:47:26 -0600, Paul wrote:
Tim Wescott wrote:
I need a stick-like thing, about 30 inches long, to go from a pivot
point to a little electric motor. It needs to be moderately rigid,
light and inexpensive in lots of 50 each or so. It would also be quite
nice if it's moderately attractive -- mill finish aluminum without too
many scuff marks is just fine for this. Prettier is better.

....
How about economy grade hunting arrow shafting? I know its smaller than
5/8 but unless your motor weights a couple pounds or something it should
be fine. It's fairly thick walled so drill and tap each end to
facilitate attaching the counterweight and motor.


The description in an earlier thread (see beginning of any hit at
http://groups.google.com/groups/sear...d8e61b8f8f6fe4 )
refers to "a propeller on a stick. You mount the propeller on a
motor on the stick (light aluminum tube), you counterweight and
pivot the stick so the thrust of the propeller will move it easily,
...." [for use in control systems seminar workshops] so I suppose
TW probably will use a few ounces of DC PM motor with fairly low
current draw.

I think 6063 .75x.75x.06" tubing, at under $1/foot, is probably a
dollar less per beam than arrow shafting, plus being easier to attach
to the axle. In TW's plan, the beam is fixed to the axle, which
rotates in bearings and turns the sensor pot that provides feedback
to the PID controller. One way to save on bearings would be to glue
the pot to the side of a .5" (.840" OD) PVC pipe in line with a
drilled-through pivot hole, and use a fixed axle. Schedule 40 .5"
PVC at .17#/ft is slightly lighter than the aluminum tubing, and
..75" PVC at 0.226#/ft is slightly heavier. Both have about 0.11"
wall thickness in Schedule 40 so are fairly stiff.

-jiw
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Default Alternatives to aluminum tube

Bamboo
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