washing machine motor - how does variable speed control work

[theflyingpig]

here's and odd one for you . . . . i want to use a washing machine motor to turn a BBQ spit . . . .havn't built the BBQ yet but the plan is to bolt a couple of bearing mounts to the top layer of bricks on the BBQ 'sides' and run a steel spit over the fire. I'm picturing it being big enough to cook a small pig . . . mmmmmm . .yum!

to drive the spit I thought a washing machine motor might do the trick, I have an old machine kicking around and know that the motor runs . .
so to my questions:

I expected the large pulley on the back of the drum to come off after nI removed the central bolt .. . . do I just need to apply a bit more elbow grease ?

and the motor - what do all the wires leading to the motor do? how is motor speed controlled? I'd obviouly want it to turn my spit very slowly . .

thanks in advance for any input .

Huey

 

[Minton]

The motor speed on washing machines is generally controlled by the programmer via a printed circuit board. Some machines have a variable spin speed as an option which could be either another control switch or a set of fixed speed switches.

You'd need to get the motor down to the wash speed really for it to be of any use. I fear if you try spinning the pig it would indeed probably become a flying one. I'm not sure how even the cooking will be at 1200rpm.

I think you should consider the weight of the average small pig in the first instance though. As far as I can see they start at about 6KG and some domestic washing machines might struggle with that kind of load.

Another thing to consider would be a Chicken.

 

[theflyingpig]

thanks for the reply. hmmm, so maybe the motor won't have the power to spin me pig. might still be worth a try . . . using the components from the washing machine any idea how I could fix the speed at wash speed (or even better, less than wash speed)

cheers!

 

[Steve]

http://www.olishogs.co.uk/hire1.htm

 

[big-all]

you need to gear down by around 1000 to one [25 to1 and 25 to 1]and use something like an18v battery drill 450 rpm the spit would rotate around 1 rpm every 2 mins or so

 

[theflyingpig]

thanks big-all - sounds like that rules out a washing machine motor . . .

anyone got any further ideas on best way to construct this? hiring a unit for 300 quid was not exactly what I had in mind!

thanks!

 

[big-all]

whatever motor you choose will require a great deal of gearing down electric motors only give out maximum power at high revs

if you electronicly slow a down a large motor you have a large motor with very little power

if you mechanicly slow down a motor you multiply the power fairly closely to the reduction providing the gearing is strong enough
so a 1000 to 1 will probably give you 800 times the power

so the solution to your problem is small and very very low geared

 

[2CVman]

Just a thought- what about an electric screwdriver? The motor is geared down to run with a lot of torque at low speeds and if you have a good bearing at each end of the pig and you balance the sideways weight on the shaft, the actual weight may not be a problem as the motor will not be trying to spin it up from a standing start, but only retain momentum until the crackling is crisp.
Or rig it up to a water wheel; plenty of power and low speed!
Good luck!

 

[mfarrow]

Consider the head to a central heating control valve.

These are relatively low speed and are geared, or at least the Honeywell ones are.

You can also get ELV and 110V options which would be safer for your application.

 

[big-all]

suspect the pig has grown into a giant porker in the last 5 years