Building a Go Kart

INTRODUCTION:
Hello makers! This is a go kart made by 12 engineering students (from Siddaganga Institute of Technology, INDIA). This was fabricated for a go kart race event held in Bangalore. It took around 30 days for us to fabricate it (it was our first time).

So, here is an instructable to help you guys build your own go kart!!!!

Main parts of a go kart:

1. Chassis

2. Engine and transmission

3. Seat

4. Steering

5. Brakes

6. Wheels

7. Bumpers

8. Kill switches

Go karts must have:

1. Correct steering geometry

2. Proper fail proof brakes

3. Kill switches

4. Bumpers to stop wheels coming in contact with other karts

5. chain must be adjustable and protected

6. adjustable toe in

7. Strong welds for the chassis

8. Locknut and graded (or high tensile) bolts only.

9. All fabricated parts must be hardened (heat treated).{we did not do it, but I suggest you do it }

10. Spring washers are really important.

And if you don’t have them bolts can come loose due to the vibrations and this is very potentially disastrous. (saying this from experience :- we had neglected using spring washers anywhere, so after every 7 laps or so we had to retighten the bolts on the wheels, this was real scary as we feared as to what would happen if the wheel came loose during the race. And then, after the race when we were just enjoying driving the go-kart the left wheel just flew out of the rear shaft.it was only after analysing as to why this disaster happened that I concluded it was because of not using the spring washer while securing the wheel to the wheel hub using high tensile bolts.)

11. SAFETY :- TRUST ME THIS IS THE MOST IMPORTANT OF ALL. I WOULD SAY DON’T BUILD A GO-KART AT ALL, IF YOU CANT MAKE IT SAFE. ( ONE OF THE DRIVERS WHO WAS WITH US IN THE EVENT HAD A METAL ROD PIERCED THROUGH HER LEG, AND SHE WAS IMMEDIATELY RUSHED TO THE HOSPITAL. WE NEVER FOUND OUT WHAT HAPPENED TO HER BUT IT WAS A LESSON FOR EVERYONE TO MAKE SAFE GO-KARTS. )

12. A FEW NOTES ON SAFETY :

1.BOLTS ARE EITHER FULLY TIGHTENED OR NOT PUT AT ALL. THERE SHOULD NEVER BE ANY SOMEWHAT TIGHT OR HALF TIGHT BOLTS.

2. WHEN IT COMES TO BOLTS USE ONLY HIGH TENSILE BOLTS(PREFERABLY TVS or UNBRAKO BRANDED HT BOLTS). I SUGGEST NOT USING ORDINARY BOLTS ANYWHERE.

3. FOR NUTS USE ONLY LOCK NUTS (ANY TYPE WILL DO – NYLOCK NUTS, DOUBLE NUTS, SLOTTED NUTS, CASTLE NUTS, K-LOCK NUTS, ETC.)

3. YOU WILL HAVE TO USE A SPRING WASHER IN MANY PLACES, THIS WILL KEEP THE BOLT IN A TIGHT CONDIDITON AND PREVENT IT FROM LOOSENIGN DUE TO VIBRATIONS.

4. USE THREAD LOCKER ( FROM LOCTITE ) ALSO TO PREVENT LOOSENING OF BOLTS DUE TO VIBRATIONS

Step 1: Gather the Parts

It will be very helpful if you gather all the parts before you start the build. That way it would be easier for you to design and think which parts goes where and how. And your total build time will be less. (in our case, we bought parts one by one when there was the need (please don’t do this)).


Materials you will need: (actually you need a lot, but these are some important ones)

1. Round or square tube for the chassis (30mm OD, 2.5 mm thickness)

2. Aluminum sheet for flooring (or CR sheet or zinc sheet which is inexpensive)

3. 30mm solid rod for rear axle

4. Lots of m6 and m8 lock nuts and bolts

5. Spirit level

6. C clamps (keep around 10 nos. they will be very handy)

Tools you will need:

1. Drilling machine(hand and vertical drill)

2. Hacksaw

3. Hand grinder(or cutter)

4. Cut off machine

5. MIG welding equipment

6. Lathe

7. Milling machine

Parts of Go-Kart that were purchased:

1. Hydraulic disc brake system

2. Steering knuckles

3. centrifugal clutch

4. engine

5.steering wheel

6. wheels

7.seat

8.steering tie rods

and a few other things which i donot remember as of now.

Step 2: Know the Basics

Steering geometry:

There are three different factors when deciding on the Steering Geometry for Go-Karts. Those are:

Caster:

Camber:

Kpi: King pin inclination.

Ackermann Angle

Toe:

Wheel jacking:

Our setup: in our setup we used a castor of 15 degrees and a Kpi of 10 degrees. The camber and toe are zero. You can use 12-15 degree castor and 9-12 degree of Kpi. The toe is adjustable (not to worry, u can adjust and make it zero or any other value later.). The camber is fixed(zero degrees). Welding:

Step 3: the Frame

We got a standard design for the frame, used by professional go kart builders(it was a side mounted engine design, so we had to modify it to make it rear mounted engine). We used their design to get dimensions like track width wheel base, etc and designed the rest ourselves. Our go kart is a rear engine type (so that weight gets properly balanced and the CG remains on the center line irrespective of the driver weight). This makes the kart longer but easier to design.
The frame was made of a material(mild steel) called ASTMA 106 GRADE B. you can also use AISI 1018 OR AISI1020. You can go for aluminum but that would be around 5times more expensive (a crude guess) and require TIG (titanium inert gas welding) but this would be lighter. We used round tubing on the outside (30mm OD, 2.5 mm thick) and square tube on the inside (same specs). The advantage of using square tubing is that you don’t have to make fish mouth cuts (which are time consuming). We used MIG (metal inert gas) welding. Mig welding is better than arc welding as it is stronger and takes lesser time to master. But we got our frame welded by a professional welder after putting all the pieces in the jig. If you do arc welding anywhere use good quality rods (prefer ss rods, or whichever best quality is available, it makes a lot of difference). If there are any gaps use filler material to cover it and then weld. For the jig, a drawing was made on a sheet of 6 feet by 8 feet by 1 inch plywood and the metal pieces were placed on it and secured in place by nailing wooden pieces. It was then taken for welding. Before this just keep the seat, engine, steering and check if it all fits right.

If you mess up in ergonomics you’ll up with a kart like the one shown in the picture!! 

Step 4: Making the Steering Wheels and Steering Column:

The steering column
was made out of 19mm 2.5mm thickness tubing. The dimensions are given in the pictures. The steering hub was purchased but it can be made on a lathe from aluminum. The steering wheel was made out of 25mm round hollow tubing and the central part was cut out of a 2mm MS sheet. The entire thing was given a padding to make it feel good.

Step 5: Mounting the Seat

The seat was purchased for 2800 Rs. It is made out of fire retardant FRP (fiber reinforced plastic). Use a 19mm or 20mm round hollow tube for the rear supports. Flatten the ends in a bench vise and drill it. We made an 8.5 mm drill to put an M8 bolt and lock nut to secure the
seat. (You have to make a corresponding hole in the seat too).weld the other end of the support to the frame. For the front seat support we placed square tubing (1.6mm thickness). And welded L joints with an 8.5mm drill in it to secure the front part of the seat with 8mm locknut and bolt. A support was also made for the middle portion but it was not secured using nut bolts. seat rear and front mountings seat before and after cushioning

Step 6: Engine Mounting

The engine mounting blocks were fabricated as per the drawing. We used HE30 aluminum alloy (normal aluminum won’t work, it is just too weak for engine mounting) for the upper block and EN8 MS (mild steel) alloy. This alloy is really very very strong. It has a very high carbon percentage in it. The machining was done in a vertical milling machine. It should preferably be hardened(heat treatment) before use. We skipped the hardening due to lack of time. We used rubber bushes in between the engine and the mounting blocks but I doubt it was of any use. We had to re tighten the mounting blocks after every race, so you can probably mount it without the rubber bushes, or put extremely hard(the hardest) rubber bushes.

Step 7: Rear Axle

The rear axle was made out of 30mm solid EN8 MS (mild steel) alloy. Key-ways are made in the shaft and the parts fitting on the shaft so that there is no rotational movement or slippage in between the parts. The key-ways on the rear axle was 3mm x 6mm. the key that fits in is 6mm x 6mm. so 3mm x 6mm key way is machined into every other part that goes on the axle( 2 wheel hubs , 1 sprocket hub and one disc hub). Cut the key into the length and shape of the key made on the axle. Make sure the key fits in properly; one of our keys was filed too much so during the race the key was grinded by the forces of the rear axle and the wheel just came out. And make sure the keyways are hardened (heat treated before you assemble them. The keyways on the axle can be made using a vertical milling machine and even a lathe.

Pics (I’m looking for these, I’ll update once I get it) :
keyway slots on axle

keyway slots on wheel hubs

and disc hub

sproket hub keys

Step 8: Rear Axle Hubs

On the rear axle go four hubs: 2 wheel hubs and one sprocket hub and one disc hub. (sprocket and disc hub are both the same).We purchased the hubs for disc and sprocket and made the wheel hubs using HE30 aluminum alloy. Drawing for the wheel hub is shown below. The hub can be machined on a lathe. Mistakes we did here are 1.we put and m10 tap on the hub (we were supposed to put m8) and 2.we used a full threaded graded bolt to fasten the wheel to the hub(the threads ate into the wheel frame enlarging the holes) and 3.we filed off the holes in the rim to match that on the wheel hub(losing strength because the surfaces are hardened and we filed it off) and 4. we forgot to use spring washers(the stupidest of all mistakes) this was the reason the bolts had to be retightened after every race. The result of this mistake was that the hole got enlarged during the race and the wheel flew out (literally) off the rear axle (luckily, this happened after the race). So I suggest you to use double side threaded bolts as shone in the figure. The flat part of the bolt to come In contact with the wheel rim (this won’t wear out the rim).


Pics (I’m looking for these, I’ll update once I get it) :

rear wheel hub drawing

rear disc hub

the hole enlarged

double side threaded bolts

Step 9: Assembly of the Rear Axle

Aassemble all the parts of the rear axle as shown in the figure. Tighten all the bolts very well. The locking collars prevent the shaft from displacement along the direction of its axis. The ball bearing used is SBR206 it is a self-align ball bearing, meaning, it will align itself once you put the axle into it, tighten the bearing holder after sliding the rear axle into it.


Pics (I’m looking for these, I’ll update once I get it) :

lock collar and its installation in the rear axle

ball bearing and its holder

Step 10: About the Engine

We used a Briggs and Stratton 208cc engine (950 series). But I would recommend you to use a Honda gx engine because the parts are easily available in India. You don’t get Briggs and Stratton parts in case something goes wrong. And you need to use an external spring for the throttle because the internal ones are not reliable, a few karts in the race which did not have external springs lost throttle control because the internal spring got cut!!!. Mount the centrifugal clutch on the engine axle. Your kart will go much faster if you put a CVT. one of the kart in the race had it and it held the record for the fastest lap.


Pics (I’m looking for these, I’ll update once I get it) : the external throttle spring

Step 11: Priming of the Engine

This step is very important. for this u should put fresh engine oil up to the specified level and run the engine for five hours then change the oil and run it again at little higher than idling speed for another few hours, change the oil and you can now use it. If you don’t do this (we did not do it) your engine will misfire after some time at full throttle, (when this happens you wont feel the kart accelerating even if you have pressed the throttle, infact the kart slows down for sometime before it picks up . This is very annoying and disadvantageous in a race. It would be best to go to a good bike mechanic to get your engine tuned and also learn from him how to do it and set the air fuel ratio, throttle limit, adjust the speed governor , etc.
Pics (I’m looking for these, I’ll update once I get it) :

air fuel ratio adjuster

the governor

Step 12: Trial Run

Fit the engines on the mounting blocks put the centrifugal clutch and chain, adjust the engine location till the chain is not slack and then tighten the mounting blocks in place. As a rule of thumb the direct distance between the engine axle and the rear axle should be between 8 to 10 inches.
Pics (I’m looking for these, I’ll update once I get it) : centrifugal clutch and its connection to the sprocket using chain

Step 13: Steering

The c bracket and the spindle shown in the figure were readily available for me .if you are going to make it, then follow the instructable: The Kpi is set into the spindle as 10 degrees so the c bracket should be welded at an angle of 10 degrees when seen from the front(camber) and it should be rotated by 15 degrees as seen from the side(castor). Also we have to ensure the tie rod connector of the spindle (spindle arm) does not interfere with the c bracket when you take a turn.

To do this you should either turn the c bracket like in figure __ or you should cut a part of the c bracket so that the c bracket won’t obstruct the spindle arm during a turn like in figure__.

The fabrication procedure:

1. First cut a part of the c bracket where the spindle arm interferes such that the spindle axis (the wheel goes over this rod) can turn by about 40 degrees. Repeat for the other c bracket too.
2. The square tube is cut to the required length with the ends at 10 degrees. You can set this angle in a cut off machine.

3. Now weld the c bracket to the square tubing and ensure it is centered and symmetrical on both the sides.

4. Now, put the spindle into the c bracket and secure it in position with the bolt- nut. Now put the front wheel into the spindle axle and secure it.

5. Set the wheels in the desired position according to the drawing and put some sort of wheel stops.

6. Now assemble the rear axle and put the wheels. This will set the ground clearance.

7. Now put supports below the chassis everywhere to raise the chassis by whatever the ground clearance is. Make sure the chassis is horizontal using a spirit level.

8. Now turn the square tubing by 15 degrees, get someone to hold it in that position and weld some temporary supports at the middle that would keep it at 15 degrees (castor). This will later be cut off after proper supports to the c bracket are welded from the edges of the chassis.

Pics (I’m looking for these, I’ll update once I get it) :

1.c braket welded at angle

2. c bracket cutt off to avoid interference

3. all the pics relating to c bracket fitting

Step 14: WELDING THE REAL C BRACKET SUPPORTS

Use round hollow shaft to join the c bracket to the chassis at the edge of the chassis. For this just cut rods of length approximated using a measuring tape. Then, use a table grinder to make the profiles at both the ends. Grind – check- grind- check-grind –check repeated until it is perfect. then weld it. If there is some gap use some filler material. This probably took us around 2 hours.
After this is done cut off the square tubing you used as temporary members for setting the castor. Use can use a hand held cutting machine for this.

Pics (I’m looking for these, I’ll update once I get it) : actual c bracket v supports

Step 15: BRAKES

we decide to use hydraulic disc brakes instead of mechanical, as it was required by the competition, but I still prefer the mechanical disc brakes as they are sufficient and simpler. The pictures illustrate the setup we used to make the hydraulic brakes. Make sure the reservoir is above the calipers or any other part of the brake(otherwise brake fliud can leak out of the reservoir). The main components of a hydraulic brake are: 1.force multiplier arrangement. 2.reservoir : this is a container into which you pour the brake fluid
3.master cylinder: this is cylinder and piston arrangement . When you press the pedals the piston is pushed and this in-turn applies pressure in the fluid that gets transferred along the hose to the calipers where the brake pads apply the braking force on the disc. 4. calipers: they contain the brake pads which press against the rotating disc, when brakes are applied 5. disc: it rotates with the rear live axle.

Pics (I’m looking for these, I’ll update once I get it) : everything related to brakes

Step 16: Front Assembly

Making the tie rod: we purchased a ready made tie rod, but if you are going to make it then here are the details. One side of the tie rod has a normal threading( right handed threading) and the other side has a left handed threading( meaning : to push a bolt inside you have to turn it anticlockwise and to remove it you have to turn the bolt or a tie rod end, clockwise). If you need more length of the tie rod ( if you have made some mistake) then take another small cylindrical rod and drill tap on both sides and use a double sided bolt to increase the length of the tie rod. We used this because the toe on one of the wheel was too much (probably due to some error in centering the bottom edge of the steering column). Assemble everything as you see in the pictures.

Pics (I’m looking for these, I’ll update once I get it) :

tie rod

tie rod extenders

location of the left hand and right threads

Step 17: Bumpers

You can do this in whatever design you wish, it just has to be strong and protect the kart when another kart hits you. Also put some sort of bumpers around the wheels too (this is very important and not there in our kart). This will prevent the wheel of another kart from touching the wheels of your kart, if this happens one of the karts could topple (very dangerous if karts are at high speeds (>40kmph)). Put some sort of foam padding on the bumpers to reduce the shock.

WE ACTUALLY MESSED UP THIS PART BY USING LOW QUALITY RODS FOR BUMPERS THINKING THEY ARE NOT SO IMPORTANT. THIS RESULT OF THIS WAS , A FRIEND OF MINE RIDING THE KART CRASHED INTO A STONE(?) AND THE FRONT BUMPERS GOT SMASHED. IT SMASHED INTO THE BRAKE ARRANGEMENT TOO WHICH WE HAVEN'T BEEN ABLE TO EFFECTIVELY REPAIR TILL DATE, SO THE BRAKES WORK JUST FINE, NOT AS GOOD AS IT USED TO BE BEFORE. SO USE VERY GOOD MATERIAL FOR THE BUMPERS TOO. DON'T THINK OF SAVING WEIGHT HERE.

Pics (I’m looking for these, I’ll update once I get it) :

the bumpers rear and front

the padding

the broken front bumpers

the not so working properly brake arrangement which came of in the accident

Step 18: Kill Switches

We used very cheap kill switches, but I suggest you use good ones. There is a black wire that comes out of the engine if you touch that black wire to the body of the engine or anywhere on the body of the go kart ( ground = body) the engine switches off. If you are using a battery for some purpose connect the negative of the battery to the body of the go kart, so the body of go kart is considered the negative or the ground. so, here, one end of the kill switch is to be connected to the body of the go kart and the other end to the black wire coming out of the engine. install it in two places, one where it is comfortable for the driver to access and another for someone outside to access easily.

Pics (I’m looking for these, I’ll update once I get it) : the kill switch grounding

click here for a video

https://youtu.be/0HsX-acs0_E

Step 19: Paint and Assemble

clean the chassis from all the dirt , oil, grease, etc. with a cloth .sand it with sand paper or put the emry disc to the angle grinder(or hand grinder or hand cutter) and do the emry , using the machine is easier and better. Paint the chassis with metal primer and then with paint and assemble everything. Spray painting or powder coating would give a very good look, or u can use a paint brush like we did.


Pics (I’m looking for these, I’ll update once I get it) :

emry disc fitted in an angle grinder

go kart after a coating of primer

go kart after painting

Step 20: TEST RUN

after the paint has dried, assemble all the parts. Double check to ensure all the bolts and nuts are tight. Now raise the chassis and keep something like a brick below it as support so that the wheels are in air. Now start the engine and first check if the kill switches are working. Then test test the throttle and the brakes. The brakes are a very important part of a go kart, so make sure they are working very well.

Step 21: BODY PANELS

for this process I did not take many pics . But ill try to upload some relevant pics from the web. We decided to make the body panels using FRP ( fiber reinforced plastic?).

For this we made the mold ( female) using sheet metal. The exterior of the body panels are on the side of the sheet metal this gives a smooth finish to the body panels exterior.

For this you will need:

1. Chopped strand mat (CSM) (1 layer = 1mm thick FRP)

2. Resin

3. Hardener

4. Catalyst

5. Hand gloves:- DON’T TOUCH THE CATALYST WITH BARE HANDS!

6. Paint brushes(2inch)

7. Empty containers:- for mixing (resin + hardener) with catalyst

8. Digital weighing scale:- to check the weight of resin and CSM

9. Syringes(2, 5, 10 ml):- to measure the amount of catalyst

The procedure:

1. Make the female molds using sheet metal or themocoal. If you ar using thermocoal you have to put a layer of putty on it , otherwise the resin will melt the thermocoal.

2. Apply a nice thin even layer of wax( we used automobile wax) using cotton waste , only if you do this will you be able to remove the FRP from the mould. If you forget this or dont do this properly the resin will stick to the mould and you cant remove the frp.

3. We got the resin and hardener mixed by the supplier , so I don’t know the exact proportions for this. This is just like mixing the two packets in mseal or araldite. This mixture takes around 10 days to harden or set. So you can mix it and use it within 3 or 4 days ( we used it up in a single night).

4. 10 days to set is too much time to wait. This is where you’ll need the catalyst, you have to mix the catalyst with the 2 part mixture(resin + hardener) this will set in about 20 mins, and you will have around 5-7 minutes to apply, after this time the 3 part mixture will become like hard jelly and you cant apply it. So don’t mix everything at once , mix in small batches how much ever you will need for the next 2-3 minutes.

5. After applying the wax on the mould, put a layer of 3 part mixture on the mould to make the smooth top layer and then place a layer of CSM cut to the dimension of the mould, and then wet it with the 3 part mix using a painter’s brush. Press at the edges using the brush.

6. Put another layer and apply the freshly prepared 3 part mix on this.

7. Mix fresh resin for every layer.

8. After about an hour or more, you can take out the casting with the help of a screwdriver to separate the sheetmetal mould from the frp.

9. Once the frp is completely cured, paint it and screw it into palce by making holes in it. We used self tapping screws for this.(even though they are called self tapping you need to pre drill a small hole to make things easy).

The proportions: Resin: hardener = I don’t know(find out from the place you buy it from)

Pics (I’m looking for these, I’ll update once I get it) : pics of the sheet metal mould pics of the process breaking the frp from mould painting the frp

Step 22: Thank You

I would like to thank all my team members sachin, sehran, pode, udri, gidda, ritesh, bikal, and all others for being a part of this. i would like to thank hiremath sir for being a part of this and thank YOU for looking into this instructable.

Enjoy!!!

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