Having built 12 different types of go kart over the past 25 years, the question has been asked of me many times: "How Do You Build A Go Kart?"
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I'll be honest, my first go karts weren't pretty, but once I got the knack of it, it wasn't so bad.
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Basically what you do is follow a series of steps:
- Design it in your head
- Put it on Paper
- Analyze it
- Procure Materials
- Fabricate
- Test
- Tweak
- Paint
- Start over....
Sounds easy enough...
1. Design It In Your Head
The first step of "design it in your head" really means you are wrestling with all the variables:
- Number of Persons
- Engine Size
- Clutch Type
- Drive System
- Suspension Type
- Component Sizes
- Material Type
- Expected Terrain
2. Put It On Paper
The second step is to put all those variables on paper. You want to layout the go kart preferably in a scale drawing format. If you can use a computer that is fine, otherwise, I used to use a piece of paper and scale the go kart at 1 inch = 1 foot. The easiest is to lay it out in real life on the floor in the garage or shop.
What I mean by that is to take the tubes lay them out on the floor, put the engine in the spot you want, 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 most skip, because they think they know better, and can design a go kart any old way they please.
Not analyzing the go-kart design is okay to a certain extent, until you discover that when you step on the gas the clutch smokes and the go kart doesn't really move. Also the go kart is so heavy that it takes three people to get it back in the garage. And it that wasn't bad enough now the go kart doesn't corner very well (it just goes straight), it is tipsy (likes to ride on two wheels) and the frame keeps bending and sagging. Things start breaking off, and you just throw your hands up and say enough! All these things could be prevented by analyzing the go kart.
Analyzing the go-cart involves the following areas:
- Center Of Gravity (Over All Weight and Weight Centers)
- Engine to Drive-Line Ratios
- Strength Of Frame
- Component Sizes
4. Center of Gravity Calculation
The center of gravity calculation sounds complex, but it really isn't. The poor mans way to get the center of gravity is to take two scales (or if you are poor yet one scale) and place it where the wheels would be located. (Thing to keep in mind is that an equivalent weight of a person(s) needs to be included and distributed properly.) When the scale reads one half the total weight, you have a 50/50 weight distribution.
"Fifty-Fifty" (50/50) weight distribution is vital for good driving and handling. When you start stepping out of that ratio, you will have handling problems. Again, this weight distribution can be performed on the floor with scales, or it can be calculated. I prefer calculating it because the placement of things can be changed easily without having to do mega-redoes, and rethinks about the go kart layout.
The downside about laying the materials out on the floor and weighing them is that you need to have general idea about the frames layout, and you may have to tack weld 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 Drive Line Calculations
The engine drive line calculation is pretty important if you want a go kart that is actually going to move. The size of the drive components are taken into account and then calculated to see how well the go kart will actually perform with the engine size, weight and ratios.
When I was designing go-karts I grew tired of having to calculate the drive line systems, so I put together a computer program and had it calculate for me. I made it pretty fancy at one point where you could insert horsepower and get out how insanely fast the go kart would go. Or I could do time trials with my go kart and calculate how much power my go kart actually had. So bottom line is do some sort of drive train analysis, or calculation.
6. Strength of Frame Calculations
The strength of the frame can be an illusive thing unless you know a bit about strength of materials and actually how to calculate the cracking stress and bending deflections. Usually what we do is: "If in doubt make it stout." That is a nice adage but it can be detrimental to a go kart design. You can end up throwing a lot of steel at a section of the go kart and actually not get any headway. So analyzing the frame prior to actually putting it together is a good idea. The last thing you want is a frame that snaps in half, or cracks in the middle.
7. Component Selection
Component sizes are pretty important if you want the go kart to last. For example, the chain size you selected may be 3/8ths pitch and be inadequate for your go kart. You may only get 10 hours out of the go kart before you have to replace the chain. Also you may have bearings that are too small or not the right size for your axels and end up having wheels fall off, or nearly fall off! You can also have a clutch just go up in smoke because it was not set up properly for your go kart layout.
Analysis is the longest most trying part of the process because nothing appears to be happening. All this thought is going into the go kart, but no go kart exists! This is similar to painting a car.
What?!
Yeah, painting a car. When you paint a car you don't take out can of spray paint and just start painting. In fact most of the time painting a car involves NOT painting the car! First you have to prep the surface. Then you tape it off. Taping and papering is probably the most time consuming process. You can spend hours taping off the spot and end up painting in 10 minutes.
The same goes for making a go kart. Unless you have a game plan put together, it will NOT just flop together in a weekend. You need to analyze the systems first then carve it out in stone (ie weld it together!).
8. Procuring Materials
Procuring (getting materials together) can be treasure hunt of sorts. Buying all the components can be quite expensive, so a good use of components from old lawn equipment is quite useful. You can get engines, and other great components off of a riding lawnmower. Some of the things that might need to be bought are clutches, chains, sprockets etc... Getting together at least 90% of the components is advised unless you want to be running back to the store and back and waste your time.
There are quite a few reputable on-line go kart stores that ship you your parts relatively cheap. Try to buy as many as you can, typically you will get a good shipping rate. You also can get some good deals.
9. Go Kart Fabrication
Once you have analyzed your go kart, you may begin with the fabrication process.
Welding a frame together is not that bad. It first involves, obviously, getting all the pieces to the right length and shape. Then hold them all together, and tack-weld the frame together. The biggest trick is getting everything to stay straight and flat. I typically use a homemade jig and clamp the pieces together. Then I weld the frame up solid after I have tacked it together.
Because you know where are the pieces go, it pretty much falls together as planned.
What I typically do is
- Weld the main frame
- Tack on the rear axel
- Weld/place in the engine and drive train and braking systems
- Place the steering system in place
- Mount the seat
- The bottom skin
- Fit the throttle and brake pedal systems
10. Test Drive It!
The test drive usually involves one or two things that aren't right. So expect something to fail. Obviously, do good pre-checks of all vital components prior to setting off, but expect failures in the following areas:
- Loose Chain
- Brakes Not Adjusted Properly
- Throttle Not Adjusted Properly
- Foot Pedal Positioning Not Adjusted Fully
These areas will probably require minute adjustments before the go kart is fully ready.
A word about being anxious:
It is not uncommon to just jump on a go kart and go for a joy ride. I was just reading this week about a sad incident where a high school boy jumped on the go kart and went for a joy ride. Unfortunately the go kart was not yet complete and the brakes were not working. He slammed into a chain link fence and twisted his leg 90 degrees in the fencing. It took them a couple of hours to extract him from the fencing. Not to mention being rushed to the hospital and having to undergo surgery.
Bottom line is that being in a hurry is never an option. Always think safety, drive smart and never be in a hurry. If you are in a hurry, slow yourself down, take a break. Never rush something, that could really end up being tragic.
The boy I am sure will never just jump on a go kart again...
11. Seating and Steering
Notice I haven't mentioned anything about seating and steering, because that is part of the analysis portion of the go kart. Getting the seat the correct size and location is just as critical as mounting the engine in the correct spot.
There are also several different styles steering systems, (above and below systems for example) that need to be clarified. Also for good cornering the layout how the steering is set up is pretty important.
12. Painting The Go Kart
I usually leave the go kart unpainted until I have worked all the bugs out of it. This is handy not having the go kart painted because then I can weld to the frame different modifications if needed.
I found this to be especially helpful when I was setting up my supercharger system. The engine mounted supercharger required an elevated gas tank initially, then I changed the system to not need an elevated tank, but one like a Briggs where the tank is part of the engine. As a result I cut the tank bracketry off of the go kart. Once the testing was complete, I painted the go kart.
As far as painting the go kart is concerned there are a wide variety of options to choose from. The down and dirty method though is to paint the go kart with a primer, preferably a rust resistant primer. A spray can is doable, but you will end up running through cans and cans of paint. The better option is to use a power sprayer, whether it is air powered or mechanical, makes no difference. The purpose of the primer is to get a good binder to the metal. (Oh and obviously, clean the metal first!) If you can get your hands on a sand blaster, 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 again cover it (not with a paint brush!) but with a sprayer.
The best finish comes when you use a two part mix paint. This is more automotive style paint. You will get an amazing finish. (I am not going to go into all the nuances about painting: i.e. wet sanding and so forth!) If you want more info on painting talk to your local car paint shop and they can help you get the mix you want. In fact they might even paint it for you for 50 bucks!
13. Starting Over
You will find that once you have gone through the process of making a gokart, that it will be hard to not make another. As you probably gathered, analysis is big on the list and when done right will make this whole project worth while.
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