can someone help me build a motorized barbecue spit?

Question

I have a 1 inch dia. 5 foot stainless steel spit rod,a pillow block and 1750 rpm motor. need to know what sprockets to use to slow the spit down to three or three and a half rpm's.

Answer 1

Now yours is an intriguing project!
(Sounds like you want to be able to BBQ a whole cow.)

Anyway, to come up with 3.5 rpm you'd need somehow to change 500 rev's of input to 1 rev of output (which you get from dividing 1750 by 3.5) So in effect you're needing a one inch diameter "cog" on the motor and a 500 inch (!) diameter "cog" on the spit, connected together cog-to-cog "teeth" (or maybe a v-belt between pulleys).

Certainly you can do the "transmission" aspect other ways (using a series of pulleys/sprockets, having co-axially mounted "cogs" to effect the reduction, but that's a whole new/other problem.

You might consider buying a commercially available "transmission" that provides this reduction (500 to 1) you're after; and get it with more variation -- like 1000 to 500 revs input produces 1 rev output; or respectively 1.75 rpm and 3.5 rpm. GOOD LUCK!

Answer 2

I know this isn't hte answer you want but:

You have to reduce the sped of your motor by almost 500X.
To do this you are going to want to look at something allong the lines of a worm drive, which at le3ast is fairly easy to build.
However, that will produce a lot of torque so there is a good chance ytou motor will be overrated.

If you have to do too much jury rigging to geet the overpowered motor to work in yoour system, then it would probably be cheaper to buy a different motor that fit your ap better.

Also if your motor is AC, you and drive it as a stepper motor by feeding it DC current pulses.