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Old 02-06-2017, 12:09 PM
TIGL TIGL is offline
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Default Front engine 212 kart build - first real kart

So after a mostly successful albeit very sketchy prototype kart, I'm embarking on better planned out build and I was hoping I could get some general input from you all. This is my prototype.



My main complaints are lack of stability due to the high COG, flimsy rear axle, poor turning authority, and an uncomfortable riding position. I also really dislike how dumb it looks which has the practical implication that the less conventional and polished the appearance, the more scrutiny I am likely to get from safety inspectors if I end up running it in a KYSCCA autocross even like I'm hoping to be able to.





Here is my general frame design. I found a bundle of 1.25" steel tube in the shop so I'll be making it out of that. I also have a 1-3/8" hole saw which makes fish-mouthing the The single biggest design limitation at the moment is that I want to be able to transport thing in the trunk of my ford focus hatchback with minimal disassembly so overall length is severely limited (~4.5'). With that in mind, I'm planning on going with a layout that puts the seat all the way at the back of the kart with the engine next to my feet and a long drive chain running through the sidewall of the kart. The seat will be centered between the rear wheels but my feet and the pedals will be offset to the right corner with the engine on the left. I think this arrangement would give me better weight distribution with the engine sitting close to the front instead of just having my feet up there.



In addition the much more comfortable seating position, other planned improvements will be a more shallow angle for the steering column which will gave less front to back movement in the pitman arm over its arc (which I think will improve my steering geometry), band brakes on both back wheels (still only one driven wheel) and a lower frame and COG by making my own spindles instead of just lifting a steering system out of a lawn tractor. I am addressing the flimsy rear axle by bumping up from 3/4" all-thread to a 1" heavy walled steel tube (actually a section of 3/4 black pipe cleaned up on a lathe but who's counting ) with a 7/8"all-thread welded into the ends. The all-thread will be turned down to 3/4" so I can re-use the wheel bearings and hubs I made for the prototype.
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Old 02-06-2017, 12:39 PM
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The unique design is refreshing, and the motor placement would be useful if you could make the kart front wheel drive.. Also it's much safer with this design because your kind of enveloped in the kart lolol
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Old 02-06-2017, 12:44 PM
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Basically I'm looking for some general feedback on the design and any specific things to watch for if anyone has made a front engine or ultra compact kart before

---------- Post added at 02:44 PM ---------- Previous post was at 02:40 PM ----------

I thought about front wheel drive for a second but unless I went with wagon steering and had the motor mounted on the kingpin, IDK how I would get it to work.

Yes, it should be much safer than my current death trap I'm planning on adding a roll bar/cage, seat belt and some pool noodle padding for the frame to make it even better
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Old 02-06-2017, 12:51 PM
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Quote:
Originally Posted by TIGL View Post
Basically I'm looking for some general feedback on the design and any specific things to watch for if anyone has made a front engine or ultra compact kart before

---------- Post added at 02:44 PM ---------- Previous post was at 02:40 PM ----------

I thought about front wheel drive for a second but unless I went with wagon steering and had the motor mounted on the kingpin, IDK how I would get it to work.

Yes, it should be much safer than my current death trap I'm planning on adding a roll bar/cage, seat belt and some pool noodle padding for the frame to make it even better
If you find an old 4wd four-wheeler then you can harvest the U-joints, splined shafts and mounts and do it that way. It will probably be more efficient since the motor will be pulling the direction of your front wheel rather than pushing in a straight line when you are trying to turn! Otherwise you'll be running quite a lot of chain
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Old 02-06-2017, 01:15 PM
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Quote:
Originally Posted by tinamcjittles View Post
If you find an old 4wd four-wheeler then you can harvest the U-joints, splined shafts and mounts and do it that way. It will probably be more efficient since the motor will be pulling the direction of your front wheel rather than pushing in a straight line when you are trying to turn! Otherwise you'll be running quite a lot of chain
All that sounds much too complicated TBH. The makerspace I go to has about 80lbs of #40 chain just chilling in a box so the cost of power transmission is pretty much zip
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Old 02-06-2017, 01:15 PM
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I wouldn't bother with the pipe rear axle, is just get a piece of keyed shaft... It's going to be flimsy and not have alot of strength ... Not to mention... The effort to build...

Also you'll be much better with the live axle, as it it easier to mount brake, sprocket and hubs for wheels...
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Old 02-06-2017, 02:04 PM
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I'd say the design is rather unique, but my brain asks why?
I suppose because you can.
But, how are you going to deal with 8 or 10 feet of chain whizzing by you while you drive it?
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Old 02-06-2017, 03:13 PM
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Quote:
Originally Posted by Bbqjoe View Post
I'd say the design is rather unique, but my brain asks why?
I suppose because you can.
But, how are you going to deal with 8 or 10 feet of chain whizzing by you while you drive it?








Front engine kart... looking forward to see how it goes.
I think a hotrod-esque front engine kart would be pretty neat.
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Old 02-06-2017, 03:43 PM
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Front wheel drive and rear wheel steer would be easy enough I think.
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Old 02-06-2017, 04:29 PM
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The why is because of space constraints make it better to gave the seat aaallllll the way in the back. The chain will be fully enclosed for most of its length so the risk shouldn't be too huge.

I will be doing a live rear axle, one of the wheels will just won't be keyed into the shaft so that it can turn more easily. Also the pipe will be vastly more rigid than the threaded rod I used last time which mostly worked so it should work well. And be a lot less expensive.

Rear wheel steering sounds like a nightmare and is almost certainly not legal for auto cross.

I am planning on going for the arched hood hotrod look, it should be lots of fun.

Sorry about the disjointed thoughts, I'm typing on a phone rn.
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Old 02-06-2017, 04:53 PM
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You will probably have to use a jackshaft or two, which could rob some power over the whole length of the chains. All that rotating mass of the jackshafts, or a long chain, would seem like it would use up a decent amount of the power from the engine.
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Old 02-06-2017, 05:07 PM
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I've seen front engine builds, and at least one of them switched to a shaft drive because of the long chain. Here is a long video.

I'm sure you can find the original build off their channel to get some idea's.

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Old 02-06-2017, 05:12 PM
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That's different.

Last edited by Kentucky Boy; 02-06-2017 at 05:15 PM. Reason: Spl
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Old 02-06-2017, 05:33 PM
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This dude did probably the best build I've ever seen, and it's front engine.

http://www.diygokarts.com/vb/showthr...ight=mini+jeep

(With a chain)

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Old 02-06-2017, 05:45 PM
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Quote:
Originally Posted by Joe-405 View Post
Front wheel drive and rear wheel steer would be easy enough I think.
Isn't that the same as turning the seat around on a standard Go Kart LMAO!!!!!!!!

---------- Post added at 07:45 PM ---------- Previous post was at 07:43 PM ----------

Quote:
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Rear wheel steering sounds like a nightmare and is almost certainly not legal for auto cross.
Not legal for autocross? I don't recall ever seeing a front engine go kart auto cross class????
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Old 02-06-2017, 06:05 PM
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Quote:
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Isn't that the same as turning the seat around on a standard Go Kart LMAO!!!!!!!![COLOR="Silver"]
Hmm....a solid axle Forklift. Sounds like a horrible, awful idea to me.
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Old 02-06-2017, 06:21 PM
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I do not think you will have much luck getting the Chain to run that long Distance.
Possibly with Jack shafts But still just a pain in the butt and most likely constant head ache of derailed chain.
Also I think it will Rob Horse power.

The Shaft used in the Cars and Cameras Video "Rat Rod Wagon" posted above. Is only 69.99 and good for up to 40 HP However limited to 540 RPMS. The Rat Rod wagon Got away with it...So far but probably not for long and surely not in an Auto Cross.
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Old 02-06-2017, 07:02 PM
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Quote:
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Isn't that the same as turning the seat around on a standard Go Kart?
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Old 02-07-2017, 12:48 PM
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I guess the issue with running chain long distance is that it requires a lot of force to keep it tensioned and that it would be hard to align? Currently I'm planning on using a long piece of 1"x 3" rectangular steel tube as a chain guide/guard. If I run it through that with occasional UHMWPE blocks as low friction guides to keep the lower part of the chain centered and supported in the interior, I think I have a decent shot at making it work. Hopefully I'll be able to answer that question tonight or tomorrow.

Karts are legal for autocross so long as they fit these rules (250 kart rules start on page 5)

Also, heres a vid of the prototype running successfully (no spils!)
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Old 02-07-2017, 01:28 PM
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I don't what your gear ratio is, but how are you going to fit the rear sprocket and clutch when they are bigger than the OD of the tube.
More so, there is going to be and excessive amount of wear of the "tensioning" blocks, at the point of contact in the tube as they do there job in the confined space, that's if there is enough to move to tension without touching the opposite running chain, I doubt you'll get far before it starts skipping teeth... from wear or stretch.
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