Starting a Go Kart build

[blmiller93]

Well here i am, in the go kart section. Ive been over in the mini bike section cuz i thought thats what ill build, then i found this decent little go kart frame for 20 (USD). The frame itself is a little rough around the edges but i believe with some tlc and some parts i think it will be a better choice over the mini bike. Ive posted some pics below. I dont think i will need help or ideas working on anything but the rear end.

Engine: 3hp briggs and stratton straight pipe exhaust

Mainly im wanting a dual rear wheel drivetrain, instead of the normal 1 wheel. I was thinking if there were some bearings that i could attach somehow to the frame and run an axle with the drive sprocket attached through that id have it made. Any ideas or info would be greatly appreciated

Other than that ill check around at other posts to get ideas.

Thanks for looking

 

[blmiller93]

Drive ratio

I dont know standard tire size to aid in my search but im guessing a 6" wheel is about the right size for the rear on a go kart. im using a 127cc 3 hp briggs and stratton 3600rpm engine for this build, and id like to get a decent amount of top speed, say at least 15 mph. What would be a good gear ratio for something around there or maybe more powerful. I know tire size plays a key role in this so if a bigger tire is recommended please let me know.

 

[gvfc2]

We do have a speed calc. On the front page. Just type in diygokarts.com I would post the direct link but I'm on my phone. Once you find the ratio post and and see if people think it could pull the wieght

 

[gvfc2]

Well I did maage to get the link but it took awhile

http://www.diygokarts.com/speed-calculator.html

 

[blmiller93]

Thanks. According to that and looking at a 6:1 ratio it says 11mph. using a 6" wheel. and apparently 6" is a little on the small side for go karts. The kart and myself included shouldnt weigh over 250lbs. going with an 8" wheel and a 4:1 ratio it increases to 21mph so that isnt a bad deal at all honestly. What do you think

 

[blmiller93]

Eh with a 10 inch tire and a 5:1 ratio like that calculator recommends for go karts produces the same speed of 21. 5:1 sounds more feasible.

 

[landuse]

Well I did maage to get the link but it took awhile

http://www.diygokarts.com/speed-calculator.html

It should not be hard for people to find anything on this forum. Have a look at the Helpful Links Sticky

http://www.diygokarts.com/vb/showthread.php?t=10036

Eh with a 10 inch tire and a 5:1 ratio like that calculator recommends for go karts produces the same speed of 21. 5:1 sounds more feasible.

If I were you, I would go with about 10-12" wheels, and a 6:1 ratio. If you go to 5:1 (which is higher), you will put more strain on your clutch. 6:1 is always a good ratio for a kart unless the wheels get too large. Then you will need to go lower.

If you want to convert your kart to a live axle, you will just need to get some pillow block bearings, or some axle hangers. You will also need a keyed axle.

 

[gvfc2]

i meant took a wile with my phone to get it. my phone is slow due to dropped hundreds of times.

 

[landuse]

i meant took a wile with my phone to get it. my phone is slow due to dropped hundreds of times.

I didn't mean that you didn't know about it, I was just throwing it out there for all to see. Sorry for the confusion

 

[Doc Sprocket]

Let's not confuse wheel sizes with tire sizes. For the purpose of calculation, we use overall tire diameter, not wheel size. I doubt very much that anybody is going to use a tire that measures 6" overall. Wheel size (or more accurately rim size) is entirely unimportant for calculation purposes, as you can have the same diameter tire available in multiple rim sizes.

 

[OzFab]

So, wrapping all that up into one small package:
6" rims with 13" tyres, which is a pretty standard size, 10t clutch & 60t axle sprocket should net you a top speed of around 23mph. A 72t axle sprocket will give you 19mph & a bit more torque on take off which, IMO, would be better with the weight consideration.

As for the live axle conversion: First, you need to cut off the existing spindles. Then you get an axle & wheels that will closely match the width of the front wheels (track). It's up to you whether you use axle hangers or pillow block bearings, that depends on your desired overall height. You can make that decision after you have your axle & wheels setup.

There are a few "live axle conversion" threads; use the search feature to find them

 

[gvfc2]

also wouldnt it be worth noting if he had alittle more money a torque converter will help with speed and more take off power?

sorry landuse i didnt read it carefully enough.

 

[blmiller93]

Thanks guys, i was looking at wheels at northern. Specific go kart wheels with tires are approximately 9 inches in diameter. (together) But those are 40 bucks a wheel. Kinda pricey to be honest. Id rather spend 200 bucks elsewhere. im not going to have boo koos of money till later this fall, but if im doing this right im doing it the first time, not rebuild after rebuild. I bought this kinda crappy frame b/c i wanted to have some sort of starting point. if a torque converter is the best then i might use that, i dont know where i should get them. I was also looking at "mountable bearings" at northern to use if i mounted a bracket on each side of the go kart on or near the existing axles. Is this what you refer to as pillow stock bearings?

 

[OzFab]

Have a look at this thread:
http://www.diygokarts.com/vb/showthread.php?t=1180

Places like BMI, Go Kart Galaxy & MFG are great places to start