I'm building a turntable from wood that will operate outside,
approx 3 feet in diameter.
I have an old electric wheelchair motor that works on 12 volts and rotates
approx 200 revs per minute. (no speed controller)
I'd like to get this down to about 20 revs per min.
I thought I could drop the turntable on one of the wheels and hope the
friction would turn the edge
but this does'nt appear to work
Any ideas how I can get this to work with basic household/garage parts?
(I've not got suitable chains and sprockets, belts and pullies in my garage)
Come on uk.d-i-y here's a challenge for you.
TIA
--
Vass

Vass wrote:
I'm building a turntable from wood that will operate outside,
approx 3 feet in diameter.
I have an old electric wheelchair motor that works on 12 volts and
rotates approx 200 revs per minute. (no speed controller)
I'd like to get this down to about 20 revs per min.
I thought I could drop the turntable on one of the wheels and hope the
friction would turn the edge
but this does'nt appear to work
Any ideas how I can get this to work with basic household/garage parts?
(I've not got suitable chains and sprockets, belts and pullies in my
garage)
Come on uk.d-i-y here's a challenge for you.
TIA
Why does your scheme not work then?
To get the speed you want, a wheel of 3.6" diameter is needed. How about
a childs push chair wheel or a wheel from a medium sized castor.

Bob

Vass wrote:
I'm building a turntable from wood that will operate outside,
approx 3 feet in diameter.
I have an old electric wheelchair motor that works on 12 volts and
rotates approx 200 revs per minute. (no speed controller)
I'd like to get this down to about 20 revs per min.
I thought I could drop the turntable on one of the wheels and hope the
friction would turn the edge
but this does'nt appear to work
Any ideas how I can get this to work with basic household/garage parts?
(I've not got suitable chains and sprockets, belts and pullies in my
garage)
Come on uk.d-i-y here's a challenge for you.
TIA
Drop the voltage to about a volt. With a capacitor to give full
voltage 'start ' volts. Probably a very fat resistor of a few ohms, and
a big electrolytic would do the job.

But really, you want a gearbox.

See if you can cannibalise an old belt drive turntable..

Vass wrote:
I'm building a turntable from wood that will operate outside,
approx 3 feet in diameter.
I have an old electric wheelchair motor that works on 12 volts and
rotates approx 200 revs per minute. (no speed controller)
I'd like to get this down to about 20 revs per min.
I thought I could drop the turntable on one of the wheels and hope the
friction would turn the edge
but this does'nt appear to work

Do you mean with the drive wheel vertical & the turntable horizontal?

How about using both horizontal so the wheel turns against the edge of the
turntable?


--
Dave - The Medway Handyman
www.medwayhandyman.co.uk

"Vass" wrote in message
o.uk...
I'm building a turntable from wood that will operate outside,
approx 3 feet in diameter.
I have an old electric wheelchair motor that works on 12 volts and rotates
approx 200 revs per minute. (no speed controller)
I'd like to get this down to about 20 revs per min.
I thought I could drop the turntable on one of the wheels and hope the
friction would turn the edge
but this does'nt appear to work
Any ideas how I can get this to work with basic household/garage parts?
(I've not got suitable chains and sprockets, belts and pullies in my
garage)
Come on uk.d-i-y here's a challenge for you.
TIA
--
Vass


More info required. Is the turntable just supported on an axle or will you
use additional support at the periphery? What sort of load does the
turntable carry, what sort of bearings will you use, is the load centred or
does it put a moment on the axle. Once you have that lot, we can think about
the torque required and see if it is feasible to have a frictional drive as
you are suggesting, or whether you might need something like a chain or
gear.

On Sat, 11 Jul 2009 11:01:22 +0100, Vass wrote:

I thought I could drop the turntable on one of the wheels and hope the
friction would turn the edge but this does'nt appear to work

Direct drive from the motor shaft to the edge of the turntable I take
it?

Smooth timber against a smooth metal isn't going to have much
friction. Try wrapping the shaft in self amalgamating tape to give a
soft rubbery surface with lots of friction. You may well have to rig
up some form of sprung pivot mount for the motor to keep the shaft
pressed against the edge of the turn table unless your engineering of
that is *very* good.

With the 10:1 reduction required the "shaft" dia will need to be
about 3 1/2" that wouldn't be practical to build up with SA tape...

The simple and easiest solution is probably a belt drive of some sort
that will take up the engineering tolerances for you. Pullies can be
made from wood, a round block of suitable diameter with ply sides to
create the grove for the belt. The belt can be an old
fan/timing/washing machine drive belt.

--
Cheers
Dave.

In message , Vass
writes
I'm building a turntable from wood that will operate outside,
approx 3 feet in diameter.
I have an old electric wheelchair motor that works on 12 volts and
rotates approx 200 revs per minute. (no speed controller)
I'd like to get this down to about 20 revs per min.
I thought I could drop the turntable on one of the wheels and hope the
friction would turn the edge
but this does'nt appear to work
Does your turntable turn with little effort when not on the wheel?
Wheelchair motors are fairly high torque so I can't imagine it doesn't
have the power (unless you're loading it down with tons of weight),
rather your mechanical design has a flaw (and that's not a criticism)
that you've not spotted. Perhaps you need to sit the turntable on
another two wheels or castors?

Any ideas how I can get this to work with basic household/garage parts?
(I've not got suitable chains and sprockets, belts and pullies in my garage)
Find a scrap pushbike somewhere, judicious application of angle grinder
or hacksaw will yield a nice selection of bits you can use.
Come on uk.d-i-y here's a challenge for you.
TIA

--
Clint Sharp

"Dave Liquorice" wrote in message
ll.co.uk...
On Sat, 11 Jul 2009 11:01:22 +0100, Vass wrote:

I thought I could drop the turntable on one of the wheels and hope the
friction would turn the edge but this does'nt appear to work

Direct drive from the motor shaft to the edge of the turntable I take
it?

Smooth timber against a smooth metal isn't going to have much
friction. Try wrapping the shaft in self amalgamating tape to give a
soft rubbery surface with lots of friction. You may well have to rig
up some form of sprung pivot mount for the motor to keep the shaft
pressed against the edge of the turn table unless your engineering of
that is *very* good.

With the 10:1 reduction required the "shaft" dia will need to be
about 3 1/2" that wouldn't be practical to build up with SA tape...

The simple and easiest solution is probably a belt drive of some sort
that will take up the engineering tolerances for you. Pullies can be
made from wood, a round block of suitable diameter with ply sides to
create the grove for the belt. The belt can be an old
fan/timing/washing machine drive belt.


I can use the shaft or keep the wheel on it. I'm having to fix the other end
of the shaft or else the
diff kicks in and I get no drive at all at one end
Like the idea of putting the shaft against the edge of the turntable, that
had not occurred to me.
Everything horizontal, Table will carry approx 8 kilos.
bearings for turntable? I have no idea, was going to use 4 small castors
from a sofa.
I could use bungies for the pressure against the table.
will give this a go, maybe supply pics if this fails...
Ta for help so far folks.
--
Vass

"Vass" wrote in message
...

"Dave Liquorice" wrote in message
ll.co.uk...
On Sat, 11 Jul 2009 11:01:22 +0100, Vass wrote:

I thought I could drop the turntable on one of the wheels and hope the
friction would turn the edge but this does'nt appear to work

Direct drive from the motor shaft to the edge of the turntable I take
it?

Smooth timber against a smooth metal isn't going to have much
friction. Try wrapping the shaft in self amalgamating tape to give a
soft rubbery surface with lots of friction. You may well have to rig
up some form of sprung pivot mount for the motor to keep the shaft
pressed against the edge of the turn table unless your engineering of
that is *very* good.

With the 10:1 reduction required the "shaft" dia will need to be
about 3 1/2" that wouldn't be practical to build up with SA tape...

The simple and easiest solution is probably a belt drive of some sort
that will take up the engineering tolerances for you. Pullies can be
made from wood, a round block of suitable diameter with ply sides to
create the grove for the belt. The belt can be an old
fan/timing/washing machine drive belt.


I can use the shaft or keep the wheel on it. I'm having to fix the other
end of the shaft or else the
diff kicks in and I get no drive at all at one end
Like the idea of putting the shaft against the edge of the turntable, that
had not occurred to me.
Everything horizontal, Table will carry approx 8 kilos.
bearings for turntable? I have no idea, was going to use 4 small castors
from a sofa.
I could use bungies for the pressure against the table.
will give this a go, maybe supply pics if this fails...
Ta for help so far folks.
--
Vass
Well, four casters from a sofa aren't designed for high mileage. If it's
just for intermittent use, OK, but if for continuous rotation for a year or
more they might wear out. I assume you mean to use these to take the table
weight? You might only need three, but you also need something to keep it
centred. If you are using a belt drive then the belt tension will put a
radial load on the table, as will pressure from a friction drive. Bungies
are definitely a good idea for this. You might get away with metal on wood
for your radial bearing, or you could use some more castors (at least two,
using the belt or bungee tension to keep the table in contact with them,
assuming they are "fixed" to something non-moving).

Personally, I would probably try to use rolling element bearings for low
friction and long life. At low speed you can run them without lubricant even
in wet conditions. Or, if you keep the rain off, grease will give even lower
friction. You might adapt something like a washing machine drum bearing, a
car wheel bearing assembly, or an old bicycle wheel. With this layout, a
single bearing assembly (probably two bearings) will take both the radial
and axial (vertical) load.

In an earlier contribution to this discussion,
Vass wrote:

I'm building a turntable from wood that will operate outside,
approx 3 feet in diameter.
I have an old electric wheelchair motor that works on 12 volts and
rotates approx 200 revs per minute. (no speed controller)
I'd like to get this down to about 20 revs per min.
I thought I could drop the turntable on one of the wheels and hope the
friction would turn the edge
but this does'nt appear to work
Any ideas how I can get this to work with basic household/garage
parts? (I've not got suitable chains and sprockets, belts and pullies
in my garage) Come on uk.d-i-y here's a challenge for you.
TIA

In what way doesn't it work:
- is the speed wrong?
- does it stall the motor, or
- do you get wheel-spin?
--
Cheers,
Roger
______
Email address maintained for newsgroup use only, and not regularly
monitored.. Messages sent to it may not be read for several weeks.
PLEASE REPLY TO NEWSGROUP!

On 11 July, 11:01, "Vass" wrote:

I thought I could drop the turntable on one of the wheels and hope the
friction would turn the edge
but this does'nt appear to work

Should do, so why not? Most likely you have insufficient force down
onto the wheel, thus no traction. Either the disk must flex, the
bearing must allow movement vertically, or you'll need to lift the
drive wheel with some adjustable (and sprung) linkage.

"Andy Dingley" wrote in message
...
On 11 July, 11:01, "Vass" wrote:

I thought I could drop the turntable on one of the wheels and hope the
friction would turn the edge
but this does'nt appear to work

Should do, so why not? Most likely you have insufficient force down
onto the wheel, thus no traction. Either the disk must flex, the
bearing must allow movement vertically, or you'll need to lift the
drive wheel with some adjustable (and sprung) linkage.


its slipping but I dont have the load on the table yet.

"newshound" wrote in message
...

Well, four casters from a sofa aren't designed for high mileage. If it's
just for intermittent use, OK, but if for continuous rotation for a year
or more they might wear out.

its for 3 weeks

I assume you mean to use these to take the table weight? You might only
need three, but you also need something to keep it centred. If you are
using a belt drive then the belt tension will put a radial load on the
table, as will pressure from a friction drive. Bungies are definitely a
good idea for this. You might get away with metal on wood for your radial
bearing, or you could use some more castors (at least two, using the belt
or bungee tension to keep the table in contact with them, assuming they are
"fixed" to something non-moving).

Personally, I would probably try to use rolling element bearings for low
friction and long life. At low speed you can run them without lubricant
even in wet conditions. Or, if you keep the rain off, grease will give
even lower friction. You might adapt something like a washing machine drum
bearing, a car wheel bearing assembly, or an old bicycle wheel. With this
layout, a single bearing assembly (probably two bearings) will take both
the radial and axial (vertical) load.

I'll pop down the local tip, see what they have on offer
ta
--
Vass

Vass wrote:
"Andy Dingley" wrote in message
...
On 11 July, 11:01, "Vass" wrote:

I thought I could drop the turntable on one of the wheels and hope
the friction would turn the edge
but this does'nt appear to work

Should do, so why not? Most likely you have insufficient force down
onto the wheel, thus no traction. Either the disk must flex, the
bearing must allow movement vertically, or you'll need to lift the
drive wheel with some adjustable (and sprung) linkage.


its slipping but I dont have the load on the table yet.

What ferzacerly is this for then? We are all intrigued?


--
Dave - The Medway Handyman
www.medwayhandyman.co.uk

"The Medway Handyman" wrote in message
om...
Vass wrote:
"Andy Dingley" wrote in message
...
On 11 July, 11:01, "Vass" wrote:

I thought I could drop the turntable on one of the wheels and hope
the friction would turn the edge
but this does'nt appear to work

Should do, so why not? Most likely you have insufficient force down
onto the wheel, thus no traction. Either the disk must flex, the
bearing must allow movement vertically, or you'll need to lift the
drive wheel with some adjustable (and sprung) linkage.


its slipping but I dont have the load on the table yet.

What ferzacerly is this for then? We are all intrigued?


we have a scarecrow festival soon, mine will be animated and kids can press
a button
to spin the crows :-)

--
Vass

"The Medway Handyman" wrote in message
om...


here we are so far...
http://www.youtube.com/watch?v=Fb3CvH2-xy8
--
Vass

Vass wrote:
"The Medway Handyman" wrote in
message om...


here we are so far...
http://www.youtube.com/watch?v=Fb3CvH2-xy8

Lookin good! All you need is something spring like to ensure contact.

How did you cut the circle & how 'circular' is it?


--
Dave - The Medway Handyman
www.medwayhandyman.co.uk

Vass wrote:

"The Medway Handyman" wrote in
message om...


here we are so far...
http://www.youtube.com/watch?v=Fb3CvH2-xy8
OK much slower than you said you wanted.

If you want the turntable speed to be one tenth of the shaft speed as
you originally stated, then you need a wheel of 3.6 inches fitted to the
motor shaft.

Bob

"The Medway Handyman" wrote in message
om...
Vass wrote:
"The Medway Handyman" wrote in
message om...


here we are so far...
http://www.youtube.com/watch?v=Fb3CvH2-xy8

Lookin good! All you need is something spring like to ensure contact.

How did you cut the circle & how 'circular' is it?

string and jigsaw, its pretty good
speed appears usable with other shaft held so might just add something to
the shaft to ensure good adhesion
dont need it to be too quick, the scarecorws might fly off !
--
Vass