Educate me as to homebuilt Go Karts

I have a 13-year-old son who has been bugging me for something motorized for a while now (go kart, dirt bike, etc). Naturally, I'd like to feed this interest in mechanical things, if nothing else because it'll get him off the damn Playstation for a while. I also have a Father-in-law who is a retired machinist with 40+ years of experience and a full machine shop in his garage. I mean full, multiple lathes, CNC milling machine, several welders, tubing benders, etc etc. The FIL has offered to help the boy and I build a go kart. Needless to say, he's all for it. I am, too, though I'm not exactly swimming in free time, it would be great grandfather-father-son bonding, and he'd learn a ton. Heck, I might even pick up a thing or two!

Now, I'm fully aware that the better/cheaper/faster way would be to either buy a fixer-upper kart on Craigslist or get a kit, but since the building is half the point with this, we are going to start from scratch. As I said, he has all the tools and expertise we could ever need and access to metal suppliers and such. I have 20+ years of CAD experience and access to high-end software (Siemens NX). I have considered buying a set of plans and building from those. Here are a couple of places that have them:

http://www.kartbuilding.net/ http://www.spidercarts.com/alt/index.html

But, looking at them, they seem pretty simple, and I'm not sure it's worth it. Let's face it, there's not a lot to these things. Any parts we couldn't make we could easily source from one of these places:

http://www.mfgsupply.com/gomini.html http://www.gokartsupply.com/partcat.htm

The plan is to build a simple kart with a lawnmower-type engine, no suspension. We'll put some knobby tires on it so he can rip around our backyard and other large field-type areas.

So, any tips? Anybody done this before and has advice? Are the plans worth buying? Any other online resources I should know about?

I've seen some of the plans and don't think they are worth buying. It's a fairly simple device. Frame, simple steering with rods, engine with centrifugal clutch powering one (or both if you can find a differential) rear wheels, brake can be a band that acts on the outside of the clutch (might want to try something more advanced, but that's what mine had when I was a kid).

Design it yourself and turn it into part of the learning process. Triangulation for strength and whatnot. It's not rocket surgery!

Didn't the guy who wrote the locost book also write one for building a go cart? That would be a good place to start.

Next easiest would be to buy a riding mower as a parts donor and plan on replacing a pulley or two. Axles, transmission, engine, brakes, all there, just add frame.

What is that???

1/4 scale locost?

I am probably going to sound like a kart snob....but why not buy a cheap race kart frame, maybe even one that is bent (part of the challenge could be straitening it and re-designing it) Once completed your child could either race around the yard or even race/autocross. The only reason I mention that is sounds like you idea is more like a big scale model, then something you can enjoy after it is done.

trigun7469 wrote: I am probably going to sound like a kart snob....but why not buy a cheap race kart frame, maybe even one that is bent (part of the challenge could be straitening it and re-designing it) Once completed your child could either race around the yard or even race/autocross. The only reason I mention that is sounds like you idea is more like a big scale model, then something you can enjoy after it is done.

A reasonable suggestion, but I think he'd learn more from a "from scratch" project.

One thing I would change on the one I built several years ago would be to not have a solid axle driving both rear tires. It made the kart very "understeer-y". Second thing would be to have much beefier front knuckles and kingpins. They needed to be rewelded after being bent from direct impacts with dirt berms. Kids are stupid, very stupid, and abusive to things.

I bought the plans to build one of these->

http://www.edge.au.com/categories/Trax_II

and built it as close as I could with my skillset and tools at the time. The steering was crude and it needed way more power.

Build a cyclekart

It will be enjoyable for a larger number of years and has a big self design and fabrication edge to it.

I wrote a story in GRM about this a few years back. I've built several of these with my sons. My favorite starting point is a small, rear-engined riding mower with a 5 speed transmission. These things can be lowered pretty easily. They're usually around 8 HP, but we actually have gone to smaller/lighter engines. There is an OHV Briggs engine that's very robust--we would get them for about $25 with a push mower (some even have electric start), then get about a year out of them after we removed the governor and pushed them to about 6000RPM max instead of a steady 3600RPM. We'd use the 5 speed and clutch (kids like to shift too) and could re-use much of the original linkage etc. We'd also use the lawn mower differential. There are several types of differentials, my favorite being the ones on the lowest-end mowers. Instead of gears, these use spring-loaded pucks. If you shim the springs, you get a limited slip. There are many more tricks and it's all just about free if you go to garage sales or have a good lawnmower junkyard in town.

My boys both learned a ton from this and they've moved on to bigger things with a much better understanding of what it takes to make and fix things.

Have fun! Carl

Those Ron Champion Kart chassis starred in a (really pathetic) early 2000's reality/technology/challenge TV show: "Escape From Experiment Island" - episode 3.

I know this 'cause I was on that episode.

They made up the rules on the fly, wouldn't let us bleed the tires down once we were at the beach, and centrifugal clutches with a 3000 rpm stall speed don't work on industrial diesel engines that are rev limited below 3000 rpm.

It was a nice vacation on an island off the coast of Scotland though.

I was a racer-tyrant 11 years ago, too.

Tom_Spangler wrote:

trigun7469 wrote: I am probably going to sound like a kart snob....but why not buy a cheap race kart frame, maybe even one that is bent (part of the challenge could be straitening it and re-designing it) Once completed your child could either race around the yard or even race/autocross. The only reason I mention that is sounds like you idea is more like a big scale model, then something you can enjoy after it is done.

A reasonable suggestion, but I think he'd learn more from a "from scratch" project.

Fair enough, on that note I have a HF engine completely apart, might be a good engine to power the go-cart

http://grassrootsmotorsports.com/forum/200x-classifieds/fscomplete-hf-clone-engine-vega-helmet/74777/page1/

Or...

http://newhaven.craigslist.org/mcy/4195430964.html

I always thought it would be cool to build a 2/3 scale rock buggy. Might be a neat alternative to "normal" homebuilt carts.

You had the right idea in your first sentence get the boy and yourself a dirt bike and get out and ride, TOGETHER!

carbon wrote: I always thought it would be cool to build a 2/3 scale rock buggy. Might be a neat alternative to "normal" homebuilt carts.

Those are neat, rotate a 4cyl FWD powerplant 90* and drive a set of stock jeep axles off the FWD trans diff.

dont forget to weld the diff!

The racing Go Karts of today are very sophisticatedcompared to the Karts I raced in the mid 60's early 70's. I guess that really dates me! However, I would think it would be fairly easy to duplicate say a Bug or other brand from that time and have a Kart that handles well and is somewhat safe for your son.

Don't skimp on the brakes. Many of the karts from that era used a live rear axle on which the sprocket was mounted for power but also used a rear axle mounted disc brake which was pretty effective. I found this video to give you an idea about frame shapes. http://www.youtube.com/watch?v=1LdbuJlzaQg

If you father in law can machine some parts and weld iyou shoud be able to come up with a nice project everyone will be proud of and have learned something..

ok, after a vry quick google search, I found little info on cyclekarts. but what I did find intrigued me.

anyone have more info? maybe detailed build thread/plans? I think I want one for my in town car.....

carbon wrote: dont forget to weld the diff!

Why the hell would you do that when you could install front and rear driveshaft brakes and plumb them to a sandrail steering brake setup for full manual torque vectoring?

In reply to pirate: This is more the example I was thinking of:

http://www.gokartsoftexas.com/1959bugkart.html

Pretty staight forward in design and pretty easy to duplicate for a first project and could probably be powered with a cheap Harbor Freight engine.

My high school metalwork students build these for quite cheap:

Video in action: Midget Electric Kart