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sprocket placement on go kart?


H3re2Learn's Avatar
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04-04-18, 09:43 PM   #1  
sprocket placement on go kart?

building my first shifter go kart. its 30inches wide and 5 ft long. the frame is 1 inch square stock and all is welded. my pillow bearings are on the edge of from so that would be 30 inchs apart from each other my axle is 1 1/14. now to my question, does it matter where I put the sprocket/power? if its in the middle will it make it harder to turn since there is no differential? or is that the purpose of putting it closer to one wheel than the other?

btw I am using a 79` honda cb650 motor as the power plant.

 
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04-05-18, 04:57 AM   #2  
If you have a solid rear axle the sprocket location does not matter as far as turning. You have no differential action regardless of where the driven sprocket is located. You sprocket location is usually dictated by the engine/transmission's drive sprocket location as they both must be exactly in line with each other.

I've only seen straight rear axle (no differential) on karts raced on dirt/clay oval tracks. Usually then the entire kart geometry including frame is designed for it to only turn left. Different size and diameter tires are run on all four corners to further help the kart turn left. The kart is set up so it naturally follows through the turns but you are pulling reasonably hard on the wheel to hold it straight on the straightaways.

Karts run on pavement have differentials. I've driven karts without differentials on pavement and turning can be extremely difficult. And when you do get it to turn you can get what I call the "differential hop" as the solidly locked tires try to negotiate the turn. If going fast enough it can almost make you loose control of the kart. This also leads to... a kart on pavement without a differential doesn't turn worth a squat. It only wants to go straight. Trying to turn you loose control, you loose traction and with all that tire scrubbing you loose a lot of speed.

 
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04-05-18, 08:36 PM   #3  
Okay, so I read that racing go karts have straight axles also but they do 2 specific things, one is they change the caster on the front wheel so that the top is tilted towards the back by 9 degrees and they also use a system called ackerman steering. the ackerman steering thing is pretty cool logic but looks like it will eat up tires but im not sure how changing the caster helps with steering. hoping someone else will chime in here. any other advice would be great to hear.

 
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04-06-18, 05:17 AM   #4  
Some racing carts have straight axles and they do many more than two things.

 
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04-06-18, 06:22 AM   #5  
"Go kart" is often misused to describe anything from a flat pan with no suspension & a lawnmower engine connected to one rear tire, to large offroad machines with long-travel suspensions and full enclosures.

What kind are you building?

 
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04-06-18, 02:16 PM   #6  
650cc engine on a straight axle, low frame and 10 inch slicks.

 
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04-08-18, 08:36 AM   #7  
50 hp and 10 inch tires. What kind of gearing are you using?

 
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04-08-18, 04:13 PM   #8  
Where type track or driving will you be doing with this kart? I'm wondering with that straight axle and no differential. It's certainly not going to be a normal shifter kart. Maybe suited to a fun run on an oval dirt track.

 
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04-08-18, 07:54 PM   #9  
its the same 5 speed that is built into the honda engine I dont plan on ever going past 3rd gear. no track this project was a just for fun build as a tribute to my wrecked honda which wasnt included in the post but it was a 79 honda cb650 and fall of 16` a truck turned left in front of me and put me in the hospital for a few months.

 
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04-09-18, 05:10 AM   #10  
You've got quite a power package but you will be severely limited by the straight axle and even more so with the tires you're considering. Wide slicks will increase the effective width of your rear axle assembly making it very difficult to get the cart to turn.

When I raced on dirt ovals I too had a straight rear axle but the frame was designed so the front and rear axle were not parallel. They were angled to help with turning left. Then the outside/right tires were wider and larger in diameter while the left side tires were narrower and smaller in diameter. Then a ton of other frame and rigging tricks to find the happy balance between something you can force to go straight and will naturally turn to match the radius of the track. When going to a different track I would change the setup depending on the radius of turns on each track.

For fun I would sometimes take my kart out to the airport and gear it for high speed. On pavement it was all I could do to hold it in a straight line. When I'd let go of the wheel it would naturally go into a left turn of the radius for which it was set-up. If I tried a sharper turn it would really fight the turn hard and develop a hop as the rear wheels would alternately slip and grip. I knew there was almost no way to flip the cart and there was nothing to hit but it was till scary to be going so fast and have it start hopping and bucking uncontrollably.

Shifter kart they are a totally different monster as most are designed to turn equally well in both directions and usually run on pavement. There is almost nothing in common between the two designs. On a dirt oval the kart built specifically for it would win hands down. On pavement and with turns in both directions the straight axle kart couldn't even drive the course at any speed while the shifter can do it pulling almost 3g's in the turns.

 
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04-09-18, 07:31 AM   #11  
The "superkarts" I see on Youtube have no suspension, ridiculous power and appear to have no differential. I think tire scrub is accepted.

About 10 years ago I had a dirt track shifter buggy powered by a Kawasaki 750cc 1-cylinder bike motor. Quite the torquey beast. On dirt the solid rear axle/swingarm did just great but once when making a tight turn on a paved cul-de-sac the buggy flipped and broke my hand. I didn't enjoy that crazy machine quite so much afterwards.

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