Pig roasting machine

[keith]

Im going to build a simple small pig roaster....

Im looking at a motor that says 130 rpm...with a gearbox that say 25 to 1.
Motor is off a golf trolley.


Is it safe to assume that this will give a final rotation of about 5 rpm....

Or am i missing something

[Dazco]

That looks about right to me, final speed may be a bit either way depending on load etc . Not sure how to add small pig into the equation though when you get it up and running giz a shout and we will pop round to sample it .

[AdrianC]

Im looking at a motor that says 130 rpm...with a gearbox that say 25 to 1.

Is it safe to assume that this will give a final rotation of about 5 rpm....

So long as the gearbox is "right way round"...
130/25 = 5.2, so 11.5 sec for a revolution - but 130x25 = 3,250rpm... <grin>

But really all you need is a pair of gears and a chain - you probably wouldn't want to direct-drive the spit anyway, so you'd have to mount it elsewhere and chain drive. Just adjust the gear sizes to get the right speed. It might be 130rpm max, but wouldn't a motor off a golf trolley have a speed controller anyway?

[keith]

Cheers

Wanted to make on for ages....i now have a simple design ...based around a simple frame and fire tray...partly fabbed at work.

Rpm is key though.

[keith]

Im looking at a motor that says 130 rpm...with a gearbox that say 25 to 1.

Is it safe to assume that this will give a final rotation of about 5 rpm....

So long as the gearbox is "right way round"...
130/25 = 5.2, so 11.5 sec for a revolution - but 130x25 = 3,250rpm... <grin>

But really all you need is a pair of gears and a chain - you probably wouldn't want to direct-drive the spit anyway, so you'd have to mount it elsewhere and chain drive. Just adjust the gear sizes to get the right speed. It might be 130rpm max, but wouldn't a motor off a golf trolley have a speed controller anyway?

I was thinking about the speed controller....problem is this is just a motor and g box....not the whole trolley....but its cheap and unused.

Also looking at some complete trollies.....assuming they have variable speeds ?

[xs1100515]

AC or DC?

If AC single phase I presume

[keith]

12 volt dc

[xs1100515]

12 volt dc

Speed control shouldn't be so much of a problem. With the high gearing the on load start current will be fairly high. It might be better to start the motor off load and then feed the load in progressively. Or gradually build the gearing. Running a wheel on a cone should do it.

[keith]

Thanks for that....i think im with you.

[xs1100515]

It's basically a play on the DAF Dafodil auto principle. A small wheel that's driven by a shaft with a conical drive. The shaft is a direct drive from the motor. So within reason it doesn't really matter what speed the motor runs at. It's speed will be fairly constant. The diameter that the driven wheel is running on dictates the speed. You just need to maintain a pressure between the cone and the driven wheel.

[Ian and Lins]

Brilliant project!
The last one I saw/ate had a big, covered 'lid' (like a posh BBQ?) The meat was really, really good.
Personally I'd go for direct drive 130 rpm. Should cook faster.

[Plasticman]

hehe, errrr if using a chain then its sprockets not gears
why not use a pair of pulleys and a fan belt, quiter and easier i reckon,
now all we need to ascertain it the breed (rare ??) of oinker and its weight
mm

[xs1100515]

A rubber tyred wheel running round a cone will be almost silent with lots of speed control and progressive acceleration control. But I agree that with he right sized drive pulleys and a belt would be a much simpler albeit without any means of changing speed. The starting current may be high too. requiring a larger motor and supply circuit. This may not be an issue.

[Plasticman]

your about there. a cone with a pulley on the end ,then as long as you are able to move a drive wheel lkaterally across the cone then start at the pointy end slow/startup and progress along to give a higher rpm
mm

[xs1100515]

your about there. a cone with a pulley on the end ,then as long as you are able to move a drive wheel lkaterally across the cone then start at the pointy end slow/startup and progress along to give a higher rpm
mm

That about sums it up.

The size of the driven wheel and the drive wheel will govern the drive ratio. If they are the same size then the drive is 1:1 I.e. the same. If the drive wheel (cone) diameter is reduced the gearing is increased and the driven wheel slows down proportionally and of course if the diameter increased then it will speed up. The cone can be straight or curved like a minaret. This can then change the rate of change of gearing i.e. non-linear. A straight cone is much easier to manufacture.

But of course a simple sprocket and chain is much easier to manufacture.

Why not cut out the motor and use a bicycle and enthusiastic progeny. That's what we breed them for.