Need a 7/8" bore DRIVE pully

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FortCollinsZJ

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need torque converter for 9hp

As the title states.

I have a 9 horse B&S engine from a newer generator. I removed the coil, and found that only the last 3/4" or so of the shaft is tapered, the rest of the shaft is 7/8" diameter, I know I will need to cut a keyway, and was contemplating doing so with a grinder. :ack2:

I had my head set on using a centrifugal clutch, but the more I read, the less I wanted one. That brings me to here. I can't seem to find a DRIVE pulley/clutch with a 7/8" bore. I like the comet setups. Now as I understand, the DRIVE unit isn't just a normal pulley, it acts as a clutch correct?

As for the jack shaft, would stepping down to 3/4" be a bad idea, or should the jack shaft remain the same size as the crankshaft?

Planning on using a 1" bar straight axle for the rear, would it be a possible option to mount the DRIVEN unit directly on the axle without using a jack shaft? or is chain driven final drive the better solution?

Also, can anybody recommend sprocket sizes to use with a 9 horse engine, 20" rear tires, and a 160lb adult driver? Aiming to have the kart weigh no more than 200-225, sans driver.

I am very very new to go karts, but not at all new to fabrication and mechanical hobbies.

Thanks for reading! I am very excited to get started with this project.
 
r_chez_08

r_chez_08

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Welcome to the forum.
I just wrote out a load of text, and accidentally hit ctrl r instead of shift r, so i will write it again in short.

here are some options, in order of what would be best.
1. buy a new shaft for the engine (1") and get a 1" bore torque converter.
2. get a machine shop to machine it down to 3/4" and put a keyway in, then get a 3/4" torque converter.
3. make an adapter/ buy an adapter, to make the shaft 1"
4. get a pulley with a tapered bore and run it to a jackshaft with the torque converter driver on.

you are correct, the torque converter unit is a clutch. however you cannot mount it straight on the axle, as it would give you a 1:1 ratio and your engine would move you nowhere.

I would reccomend 1:6 for on road or 1:7 for offroad (10-60t or 10-70t)
http://www.diygokarts.com/speed-calculator.html

Hope that helps,
Rob
 
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FortCollinsZJ

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Definitely helps. Thanks Rob. I am going to see about removing the shaft, and having the local shop turn it down to 3/4 and cutting a keyway 3/16" wide. But how deep? That would be an easy option I had not really thought of.
 
r_chez_08

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3/16 divided by 2 = 3/32" deep. However, that is 3/32" once you have got a flat on the shaft if you get what i mean, so not 3/32" from the very edge of the shaft, 3/32" once you have milled enough to get a flat surface, 3/16" wide.
 
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FortCollinsZJ

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I'm pulling the shaft today to have it machined, I am also shopping for a torque a verter. I seem to only find them good to 8hp, would my 9hp kill it? or is the bolt pattern different?
 
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FortCollinsZJ

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Well, the shaft is at Canfield (local machine shop) and will be ready for pickup early next week, and the work was quoted at only 40$. Also good news, this engine is a bit bigger than I had first thought, this thing is a 297cc engine! That should be good for a decent amount of power!

I'm looking now at the 40 series torque a averter, anybody able to lend some insight to one that will bolt up to this engine?

http://www.amazon.com/Briggs-Stratton-185432-0235-B1-Vanguard-Crankshaft/dp/B000N50IXQ
 
r_chez_08

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Nice! $40 sounds about right, however you could have probably picled up a used one for that. Used either way though.
I would get a 30 series rated to 8hp, like this one as that is a good price for a genuine comet. Also 30 series are more simple as you dont need to design your own jackshaft setup and you cannot buy a 40 series in 3/4" bore. As long as you do not plan to modify this engine to above 10hp i would stick with the cheaper 30 series ($138-160) instead of a more complex expensive 40 series ($330 ish)
 
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