3 wheel go kart design for under $300 x4 (or more)

[michaelr123]

hey everybody, sorry if you see a bunch of my threads today, i've been researching for quite awhile and i need some expert opinions

so me and a bunch of my friends in engineering classes had a crazy idea after i mentioned seeing a 7hp engine at harbor freight for only $120. a lot of bouncing off each other later resulted in plans and a design group... and we got no work done that day in class haha... but anyway, our original idea was a 4 wheeled, super small simple go kart, we were going to machine our live axles and make pretty much every piece of the frame that we could.

but as i was calculating a typical live axle set up i realized that it wasn't going to fit into our budget very well...

and just when i was going to break the news to my friends, inspiration!!

a 3 wheel design i had in my head could get rid of the live axle, the keyed wheel hubs and bearing hangers we'd need! instead take two 10" wheels and run threaded rod through them, use nuts to hold the two wheels together, but the use that threaded rod to attach the the sprocket, and disc for the disc brake to the bake wheel. then run a 5/8" axle rod through the middle and use the bearings already inside of the wheels to create the bearing to axle connection. now the wheels are directly driven and braked, and there is no need to extend the axle very far, so the frame can also be decreased in width here. this helps with storage as well as decreases material cost.

i've seen plenty of these 3 wheel designs and the seem very stable, even better in donuts then 4 wheels as a few builders claimed! i'm sort of basing the design off the spider karts design if you want a visual reference.

now for a few things i don't have entirely figured out, what is a good size of square tube that we should use for the frame? again, we're being cheap, so the lighter the better, can i get away with say, 1" 18guage? thats pretty light steel.

after that, we're making the steering wheel and front wheel assembly in the shop. also we're making our own seats.

for the disc brake, i figured that i can just get 3/16" steel plate, cut it and balance it to make the disc, and then pull a brake set off of a crappy old bike and set it to clamp to the disc. has anyone tried this before? again, i'm not looking for super braking power, just something to slow down pretty quick.

now for a few big issues we have, we really need places to ride them, and storage. are there any public places you can ride go karts? say forest preserves or parks? or do you pretty much have to take them to a private farm or trails? for storage i was originally going to have them be modular so they could break down, but with the new design, i don't think storage is as much of an issue, the being less than 3' by 5.5'.

i'll post some drawings i made so you can have a visual reference, any issues or suggestions you see that you want to bring up are much appreciated!

 

[OzFab]

I'm not quite getting your rear wheel design concept, maybe a diagram will help. Having said that, threaded rod anywhere near an axle is asking for trouble.

3 wheel designs are only stable if your front end is wide enough; too narrow & you'll face the same problems as a narrow 4 wheel kart.

16ga 1" SHS (square tube) is perfect for a small, lightweight kart.

I made just about everything on my daughters kart; frame, seat, steering components, rear axle, etc, everything but the wheels (for obvious reasons) & the brakes! Brake discs are highly balanced & hardened! Mild steel won't last long, if it's up to the task at all. By all means make the carrier hubs but spend the few dollars on a proper disc. It makes even more sense when you consider you can buy a full setup for as little as $40 or isn't your safety worth that much?

Technically, it's illegal to ride a go kart in any public area; a private track or property is the safest bet.

Good luck with the project, keep us informed

 

[michaelr123]

ok so 16ga steel, got it. i posted the diagrams if it helps, the wheel hubs have 4 holes already drilled in them and they have a dual bearing set up, they are the cheap 10" wheels from harbor freight.

the front two wheels are going to be set really wide, maybe 4' as opposed to less then 2' wide in back.

 

[OzFab]

they are the cheap 10" wheels from harbor freight.

If you haven't bought them yet, please don't, they won't last you a month. It's a bit more expensive but, IMO, you're better off with something like this. With a double flange hub on each side, you can mount a sprocket to one side & a brake disc to the other & a solid axle through the centre.

the front two wheels are going to be set really wide, maybe 4' as opposed to less then 2' wide in back.

Perfect

 

[michaelr123]

whew... $60 just for the wheel... in my opinion replacing $6 wheels works out better for price. i have to convince a bunch of almost broke 18 year old guys to do this with me lol... eventually i'll upgrade to something like that though.

really i need to figure out a place that i'm going to be able to use this thing... its all highway and cornfields around me, but i don't own any of it :/ where do guys typically take these things?

 

[Aladinbama]

whew... $60 just for the wheel... in my opinion replacing $6 wheels works out better for price.

You're asking people who know. There are many options between the $6 wheel and the $60 wheel you'll just have to do a little searching. BMI Karts even has many others for sale.
The main problem with the $6 wheel is that it really isn't made for the application you would be using it for. The bearings are cheap and the tire/rim are pretty whimpy as well. IMO, not really worth "trusting" on something you'll definitely be trying to tear up a field or a parking lot with. A wheel barrow OK, a go kart - it's your rear!
I was broke and 18 at one time as well. Search craigslist for parts/frames/whole karts that need help. Sometimes starting with something is a little easier - you'll still be able to create/machine parts, you just won't have to buy so much "other" stuff.

 

[michaelr123]

true... the treads feel a little foamy... shoot, would just a higher quality wheel like this hold up? or does it have to be a go kart wheel?

 

[exenos]

Lawn tractor wheels work great, just not for extreme high speeds. With the predator you should be fine.


EDIT: How would the school react if you drove them abound the parking lot when its not busy? Also if you get enough guys together to form a "club" some schools give funds to clubs.

 

[qtband]

If you want to be a broke 19 year old, don't use those tires. AT ALL!!!

 

[OzFab]

See, it's not just me...

Somehow, I knew you'd have that reaction. If you look closely, I did say "something like that", meaning a wide rim that hubs can be bolted to with a wide, chunky tyre. Here's another, or this one...

Note: Most of the price is in the tyre, not the rim...

IMO, if you don't at least try to convince a bunch of broke 18yo's to spend a bit more money on safe parts, you'll soon have a bunch of broke 18yo's complaining that their karts don't work...

 

[landuse]

Using those wheels might mean that you don't reach 19. There are many options out there that don't cost $60. You could even go to the junkyard and find scrapped quad tyres

 

[Aladinbama]

Just for example;
Carlisle turf saver tires - $13.95 each - if you look on Ebay sometimes Summit will have $4.95 shipping for up to 4 tires (that's a steal all by itself)
http://www.summitracing.com/parts/crr-5110201/overview/
http://www.summitracing.com/parts/crr-5112201/overview/
Put those on the 6" rims from BMI and you've got a good tire for under $30 each.
I ride motorcycles about 12 or so thousand a year. Tires get eaten in the heat of S. Texas, but I still buy the quality tires for it - I only have two and if one goes .... well, let's not even go there.
I realize a go kart isn't THAT fast nor does it have only two tires, but I could see wheels like the HF wheel being eaten up in one or two parking lot sessions. You wouldn't want to see one flying apart in a turn, much less a hard turn.

We have some drainage areas/ponds in the area along with a school nearby. So far nobody has said anything! Just stay off any practice fields and play areas. Go with the idea that if you don't tear it up they may not mind (but don't get mad if they do).

 

[michaelr123]

haha ok you guys convinced me not to use the wheel barrow wheels, at the moment we just stumbled upon a bunch of awesome deals on craigslist and we're now planning to take those and fix em up, for instance the one i'm getting for $200 (minus bartering) is 4 wheeled and running with a brigg and stratt 5hp. no way we can buy all new components and do it for under $350 as i'm starting to realize

 

[OzFab]

Darn, I was looking forward to your build