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Black Forest
08-26-2010, 11:58 AM
I need to transform 400 rpm's of a 50mm sprocket down to roughly 8 rpm's.

I think I will need to do it in two stages. Is it better to try to match the ratio's over the two stages or do one larger ratio and one smaller? I would like to use 1/2 " pitch X 5/16's roller chain.

So if I start with my 50mm sprocket what size sprockets would you use for the other three?

camdigger
08-26-2010, 12:07 PM
400 rpm in and roughly 8 rpm out translates to 50:1 reduction.

2" small sprocket (+/- 12 teeth at 1/2 pitch) and 14" (84 teeth at 1/2" pitch) large sprockets will give 7:1 reduction each

7x7=49 or "roughly" 50:1

The next question is what is available from your supplier. Sprockets selection with more than 50 teeth at my supplier seem to be a bit sparse...

Dr Stan
08-26-2010, 12:24 PM
I considered changing my V belt drive system on my bandsaw to a chain & sprocket. After I looked at the necessary sprockets & chain along with the required modifications and costs I also looked at a reduction gear box. It turned out this was the less expensive and simplest modification. In addition it is quieter and does not need the guarding a chain & sprocket system should have. In the long term it also requires a lot less maintenance.

You may want to look at https://www.surpluscenter.com/home.asp for either your sprockets or a gear box.

Black Forest
08-26-2010, 01:35 PM
I can get almost any size I need.

Readily available is a sprocket 313mm and 385mm in the pitch and width I need.

I ordered the switch I need to control the motor today. Ouch. It is a two pedal momentary switch. left pedal runs the motor ccw, right pedal runs the motor cw.

I think when I test this on a live sheep I will use my neighbors sheep! Or do any of you know where I can buy a blow up sheep?

camdigger
08-26-2010, 02:29 PM
FWIW, a vee belt reduction can serve as a torque limiter as well as one of the reduction steps...

Black Forest
08-26-2010, 02:57 PM
This motor and reduction is for the pivot arm of my leg restraints on my sheep shearing machine. The motor will only have to run very intermittently and turn the pivot arm from perpendicular 90 degree's each direction. Definitely going to need some limit switches. I don't want my sheep coming of the machine looking like corksrews!

davidh
08-26-2010, 05:54 PM
Definitely going to need some limit switches. I don't want my sheep coming of the machine looking like corksrews!


that one would be for sunday supper i would guess. . . . .

The Artful Bodger
08-26-2010, 06:30 PM
I Or do any of you know where I can buy a blow up sheep?

I am sure Australians would have some of those!:D

brian Rupnow
08-26-2010, 07:10 PM
Blackforest---I hope you bought a gearmotor with an internal brake like I suggested. Those gearmotors coast a lot. You may end up with pretzel-sheep.

PeteF
08-26-2010, 08:16 PM
I am sure Australians would have some of those!:D

Oh the irony :p

Black Forest
08-26-2010, 10:17 PM
Brian, I took your suggestion and bought a motor with a brake!