Go-cart Gearing

When it just doesn't fit anywhere else.
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Admiral Acbon
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Go-cart Gearing

Post by Admiral Acbon »

This may appeal to only a small subset of you (gcdonner + ?), but here goes. Let's say I'm seriously considering running a 30-tooth (+/-) sprocket on my go-cart's axle. The driven sprocket has 10 teeth. That's a 3:1 ratio. Later this year I hope to install a "40 series" torque converter. Based on my clumsy Internet research I gather that such torque converters have themselves roughly a 3:1 ratio (at engagement). Does this result in an overall gear ratio of 9:1? It seems too obvious, so that's why I'm asking.

Yes, I like to go fast.
Yes, there's an engine quite a bit bigger than this 5.5 hp GX160 waiting in the wings. ;)
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In a time of universal deceit, telling the truth is a revolutionary act.
Neto
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Location: Holmes County, Ohio
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Re: Go-cart Gearing

Post by Neto »

The way I understand gear ratios, you are correct. I think that if you go with the CVT, you can push your ratio down even farther, to around 6:1 or so.
I don't have personal experience with this, but I've done a lot of reading on the CycleKart site. These are basically adult go-carts running 16" motorcycle wheels, with bodies designed after the race cars of the 20's & 30's. The majority opinion (or 'guidelines') on that site limits the HP to a 6.5 Honda or Predator engine, with some modifications permitted (removing the governor, billet flywheel, etc.). I have been interested in Cycle Cars for as far back as I can recall, and through an interest in RatRods, I saw what a guy did with the radiator shell & cowling off of a Allis Chalmers tractor. I have the same parts from a Farm-All M, about a 39 model or so, that I would like to use to build a Rat Cycle-Tractor of sorts, following the basic guidelines of the cyclekart people. But I can't afford to buy a CVT - I'm just trying to use what ever parts I can scrape together for cheap. They don't use any rear suspension, and generally only power one rear wheel, and no reverse, but I'd like to have all of these features. (I injured my back in my early 20's, and the bouncing w/o some kind of springs in the rear would aggravate that old injury.) They run up to around 40 MPH +, but I'd shoot for a top speed of only 25, so I can run it on the roads here with a flag & an SMV on the back. At least I hope that would be permitted. The Amish run all sorts of non-licensed small vehicles around here, so I think it would work out, and maybe would still be classified as a tractor. Planning to use the differential out of a Snapper riding mower, with some modifications to change the gear ratio.

On your go-cart, is the rear sub-frame all unsprung weight? (Looks like you've got a suspension set up on it in the rear as well.)
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Congregation: Gospel Haven Mennonite Fellowship, Benton, Ohio (Holmes Co.) a split from Beachy-Amish Mennonite.
Personal heritage & general theological viewpoint: conservative Mennonite Brethren.
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Admiral Acbon
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Joined: Wed Oct 19, 2016 3:57 pm
Location: Ohio
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Re: Go-cart Gearing

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JohnsKart1.jpg
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JohnsKart5.jpg
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^A few pics from the years-ago Craigslist ad I bought this from.

Thanks for the reminder about the CycleKart site. I hadn't been there in a while. :-)

The Honda GX200 engine (6.5 hp) is pretty popular around here for kart racing. I should say, the knockoffs are. I get the attraction of starting off with a cheap engine, but once they're modified reliability seems to go downhill. I just checked Craigslist and there's an "almost new" GX200 2.5 hours from my house for $120, which is about what Harbor Freight normally sells their Predator engine (212cc/6.5hp) for. You might be able to scavenge parts (like a CVT) off cheap go-carts. Definitely keep us/me updated.

I bought a virtually-new GX390 (13 hp) for $200 less than new. That's what's ending up in this puppy, along with a CVT setup I bought from GoPowersports. I don't plan on going faster than 60, so the stock rating should be sufficient. :twisted:

Here in central Ohio the only motorized vehicle I could definitely get away with riding on/along most roads without any requirements more onerous than an SMV sign and a top speed of 20 or 25 would be "agricultural equipment" (Dad, could I dig out the old Wheelhorse?). Where are you located?
Neto wrote:On your go-cart, is the rear sub-frame all unsprung weight? (Looks like you've got a suspension set up on it in the rear as well.)
The rear subframe is attached to the main frame via hinges at the bottom (immediately behind the seat) and those motorcycle(?) shocks at the top.
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