Having built 12 different types of karts in the last 25 years, I have been asked the question many times: “How do you build a kart?”
I’ll be honest, my first few karts weren’t pretty, but once I got the hang of it, it wasn’t too bad.
Basically what you do is follow a series of steps:
– Design it in your head
– Put it on paper
– Analyze it
– Acquire Materials
– Manufacture
– Proof
– retouch
– Paint
– Start again….
Sounds easy enough…
1. Design it in your head
The first step of “designing it in your head” really means that you are struggling with all the variables:
– Number of people
-Machine size
– Clutch type
– Management system
– Typical suspension
– Component sizes
– Type of material
– expected terrain
2. Put it on paper
The second step is to put all those variables on paper. You want to design the go kart preferably in a scale drawing format. If you can use a computer that’s fine, otherwise you used to use a piece of paper and scale the go kart to 1 inch = 1 foot. The easiest thing is to place it in real life on the floor of the garage or shop.
What I mean by that is take the tubes, put them on the floor, put the motor where you want it, and the seat where you want it. This will give you a very rough idea of the size of the gokart.
3. Analyzing the Go Kart
Analyzing it is probably the step that most skip, because they think they know better and can design a kart the way they want.
Not analyzing the design of the kart is fine up to a point, until you discover that when you step on the throttle, the clutch smokes and the kart doesn’t really move. Also, the go kart is so heavy that it takes three people to retrieve it in the garage. And that wasn’t bad enough now that the go kart doesn’t corner very well (it only goes straight), it’s drunk (it likes to ride two wheels), and the frame keeps bending and sagging. Things start to break, and you just throw up your hands and say stop! All these things could be prevented by analyzing the go kart.
The go-cart analysis involves the following areas:
– Center of gravity (over all centers of weight and weight)
– Engine to driveline ratios
– Frame strength
– Component sizes
4. Calculation of the center of gravity
The calculation of the center of gravity sounds complex, but in reality it is not. The poor way to get the center of gravity is to take two scales (or if you’re poor, a single scale) and place them where the wheels would be located. (The thing to keep in mind is that the equivalent weight of a person must be included and correctly distributed.) When the scale reads half of the total weight, it has a 50/50 weight distribution.
The “Fifty-Fifty” (50/50) weight distribution is vital for good ride and handling. When you start to get out of that ratio, you’ll have driveability issues. Again, this weight distribution can be done on the floor with a scale or it can be calculated. I prefer to calculate it because the placement of things can be easily changed without having to do mega-redos and reconsider the kart design.
The downside to laying materials out on the floor and weighing them is that you need to have a general idea about the layout of the frames, and you may need to piece the pieces together to get an approximation of where things should be. This may involve breaking welds to place components in new places to optimize the frame. (Again, a good layout on paper helps here.)
5. Engine Driveline Calculations
Engine driveline calculation is pretty important if you want a go kart that actually moves. The size of the drivetrain components is taken into account and then calculated to see how well the go kart will actually perform with the engine size, weight and proportions.
When I was designing karts, I got tired of having to calculate drive systems, so I put together a computer program and calculated it for myself. I made it pretty fancy at a point where you could plug in horsepower and get how unbelievably fast the go kart would go. Or I could do time trials with my go kart and figure out how much power my go kart really had. So the bottom line is to do some type of drive train analysis or calculation.
6. Frame Strength Calculations
Frame strength can be somewhat of an illusion unless you know a little about the strength of materials and how to calculate crack stress and flexural deflections. Usually what we do is, “When in doubt, make it loud.” It’s a good adage, but it can be detrimental to kart design. You can end up dumping a lot of steel on one section of the go kart and not actually moving forward. Therefore, analyzing the framework before putting it together is a good idea. The last thing you want is a frame that splits in half or cracks down the middle.
7. Selection of components
Component sizes are very important if you want the go kart to last. For example, the chain size you selected may be 3/8 pitch and unsuitable for your go kart. You may only have 10 hours off the go kart before you need to replace the chain. You may also have bearings that are too small or not the right size for your axles and the wheels are falling off or almost falling off. It can also cause a clutch to go up in smoke because it wasn’t set up correctly for your kart’s design.
Analysis is the longest and most difficult part of the process because nothing seems to be happening. All this thinking goes to the go kart, but there is no such thing as a go kart! This is similar to painting a car.
That?!
Yes, painting a car. When you paint a car, you don’t get out the can of spray paint and just start painting. In fact, most of the time painting a car means NOT painting the car! First you have to prepare the surface. Then you tape it down. Engraving and wallpapering is probably the most time consuming process. You can spend hours filming the location and finish painting in 10 minutes.
The same goes for making a kart. Unless you have an elaborate game plan, you will NOT just fail in a weekend. You need to first analyze the systems and then carve them in stone (ie weld them together!).
8. Procurement of materials
Procuring (gathering materials) can be a spell treasure hunt. Buying all the components can be quite expensive, so it is very useful to put old garden equipment components to good use. You can get great engines and other components out of a lawn mower. Some of the things you might need to buy are clutches, chains, sprockets, etc. It is recommended to gather at least 90% of the components unless you want to run back to the store and waste time.
There are quite a few reputable online kart shops that ship their parts to you relatively cheap. Try to buy as many as you can, usually you will get a good shipping rate. You can also get some good deals.
9. Go-kart manufacturing
Once you have analyzed your go kart, you can begin the manufacturing process.
Welding a frame is not that bad. First it obviously involves getting all the pieces to the correct length and shape. Then hold them all together and tack weld the frame. The biggest trick is to keep everything straight and flat. I usually use a homemade jig and attach the pieces together. I then weld the frame until it’s solid after I’ve tacked it together.
Because you know where the pieces go, almost everything fits together as planned.
what i usually do is
– Weld the main frame
– Tack on the rear axle
– Weld/fit on engine and drive train and braking systems
– Put the steering system in place
– Assemble the seat
– The lower skin
– Assemble the accelerator and brake pedal systems
10. Try it!
The test drive usually involves one or two things that aren’t right. So wait for something to go wrong. Obviously, do good pre-checks on all vital components before you leave, but expect failures in the following areas:
– loose chain
– Brakes not adjusted correctly
– Accelerator not adjusted correctly
– Pedal position not fully adjusted
These areas will likely require minimal adjustments before the go kart is fully ready.
A word about being anxious:
It’s not unusual to just hop in a go-kart and go for a fun ride. This week I was reading about a sad incident where a high school boy got in the go-kart and went for a fun ride. Unfortunately the go kart was not complete yet and the brakes were not working. He crashed into a chain-link fence and sprained his leg 90 degrees on the fence. It took them a couple of hours to get him off the fence. Not to mention he was rushed to the hospital and he had to undergo surgery.
The bottom line is that being in a hurry is never an option. Always think safety, drive smart and never be in a rush. If you’re in a hurry, slow down, take a break. Never rush something, that could really end up being tragic.
I’m sure the boy will never get on a kart again…
11. Seats and direction
Note that I haven’t mentioned anything about seats and steering, because that’s part of the go kart analysis part. Getting the seat the right size and location is just as important as mounting the engine in the right place.
There are also several different styles of steering systems (over and under systems, for example) that need to be clarified. Also for good cornering the layout is very important, how the steering is set up.
12. Paint the kart
I usually leave the go kart unpainted until I have fixed all the bugs. This is useful when not having the go kart painted because then I can weld different modifications to the frame if necessary.
I found this to be especially useful when I was setting up my supercharger system. Initially the engine mounted supercharger required a raised gas tank, then I changed the system so it didn’t need a raised tank, but rather one like a Briggs where the tank is part of the engine. As a result, I cut off the tank mount from the go kart. Once testing was complete I painted the go kart.
When it comes to go kart paint, there are a wide variety of options to choose from. However, the dirty method is to paint the go kart with a primer, preferably a rust resistant primer. A spray can is doable, but you’ll end up going through cans and cans of paint. The best option is to use an electric sprayer, either air or mechanical, there is no difference. The purpose of the primer is to get a good binder for the metal. (Oh, and obviously, clean the metal first!) If you can get a shot at sandblasting, that would be ideal, because then the primer will really stick to the metal.
The final paint job would be to use an enamel style paint and recoat it (not with a brush!), but with a sprayer.
The best finish is obtained when you use a two-part mix paint. This is more automotive style paint. You will get an incredible finish. (I’m not going to go into all the nuances of painting – wet sanding and whatnot, ie!) If you’d like more information on painting, talk to your local auto paint shop and they can help you get the mix that’s right for you. want. In fact, they could even paint it for $50!
13. Start over
You’ll find that once you’ve gone through the process of making one gokart, it’s hard not to make another. As you probably realized, analytics is high on the list, and when done right, it will make this whole project worth your while.