Introduction: How to Design and Build a Go Kart.
Hello everyone this Instructable is a collaboration of nine year 10 engineering students work. Their task is to work as a team to research, design and build a go kart, using sound engineering principals. As this is a student project the frame must be kept as simple as possible, so that students can build the kart with minimal tools, and with in the time frame allocated.
This Instructable has lots of photos with notes, just run your cursor over the box on most photos to make the text pop up
Go-karts must have!
- Bumpers to stop the rear wheels coming into contact with another kart.
- Plastic front bumper
- The chain must be able to be adjusted.
- Standard off the shelf parts must be used.
- Toe-in and chain must be able to be adjusted.
- No sharp edges
- Correct steering geometry
- Remote kill switch
Members of the team
- iTz Monkeeh
Step 1: Stuff You Will Need
The first thing you need to do is to gather all the parts, as it makes it much easier to design if you can lay out all the parts where they will be on the kart and kind of "join the dots"....
Materials you will need:
25 or 30mm Square Steel
Aluminum Sheet 1.6mm thick
19mm and 25mm Steel Tubing
30mm bright solid (If you want to make your rear axle)
13mm tube or pipe.
lots of 6mm and 8mm nuts and bolts
Parts you will need: (Screen shot are includes as the ebay links can go dead)
- I recently bought a number of parts from cut price racing, they have almost everything you will need and their service was excellent .
- Axel (You can find these second hand on eBay for about $50 or new for $150 - $200)
- 30mm hubs
- Sprocket or disc carrier
- sprockets chain and clutch
- Mechanical Brake Caliper With Brake Pads & Cable
- Go Kart Brake Disc
- Self Align Pillow Block Bearing 30mm
- 4 Wheels (These can be quite expensive, new and second hand. A used set can cost you up to and over $100 on eBay)
- 4 Tires (You can find these on eBay, a new set can cost up to and over $300, but if you get a used set they can cost less than $100 or free)
- Steering Wheel (You can get a cheap second hand wheel for about $20 on eBay)
- Seat (You can use any seat you can find but we are using a fiberglass seat. You can get one on eBay for about $40)
- Engine (We are using a mower engine which you can off an old mower or look on eBay for a few dollars)
Tools we used.
- Drill press
- Metal Lathe
- Tap and die
- Hack saw
- MIG welder
- Cordless drill
Step 2: Steering Geometry
Getting the steering geometry correct on your Kart is one of the most important consideration when designing the frame. If you don't get it right you Kart will not turn but plough straight ahead. Unlike a car the rear wheels do not have a differential but are locked together and always spin at the same speed, this requires some cleaver engineering to make the inside rear wheel lift of the ground when turning and allowing the front of the kart to turn in.
Understeer happens when the front of a car tends to go straight on when you turn the wheel into a corner. You can feel the tires scrubbing against the tarmac. Most modern cars are front wheel drive and they tend to understeer. It’s inherently quite safe, as the speed is scrubbed off, and as long as there’s enough road, the tires will eventually grip and turn the car the way you want!
This happens when the back end of the car slides away from the direction of the turn. Rear wheel drive cars are much more prone to this. It’s less safe than understeer, because it can be the prelude to a spin, and suddenly lifting off the power (which is a natural reaction) can actually cause the spin as they tires “bite.” Cars like the Porsche 911, where the weight is all behind the back axle are prone to this.
Camber is the angle of the wheel relative to vertical, as viewed from the front or the rear of the car. If the wheel leans in towards the chassis, it has negative camber; if it leans away from the car, it has positive camber. so on a Go Kart it should be 0. in the middle of both positive and negative.
Positive caster angle is best illustrated by the rearward tilt of the steering fork on a bicycle. Positive caster obviously places the front wheel ahead of its pivot point and most vehicles are designed with positive caster angle. It’s defined as the angle created by the steering's pivot point from the front to back of the vehicle. Caster is positive if the line is angled forward, and negative if backward.
The Kingpins on a kart should be laid back at the top 12-15 degrees
Toe out on turns
When the vehicle negotiates a curve, the inner wheel turns more sharply and while the wheels remain in this position, the wheels will toe out, and will return to the correct toe in when the the steering wheel is returned to the straight ahead position. This is achieved by angling the steering arms toward the center of the rear axle this will cover in step 12
Wheel Jacking or Weight Jacking is related to the caster and the kingpin inclination, which controls the ability to turn and lift the inside back wheel off the ground according to which way you turn. Having a solid rear axle causes the wheels to spin at the same rate, so you need the inside rear wheel to lift off the ground which enables the kart able to go around corners.
The kingpin inclination angle, together with the caster angle, creates the phenomena of the return of the wheels to straight position after a steering operation, it also tends to maintain this position after an impact with an obstacle that attempts to alter the trajectory,
So you will need 10 degress KPI and 12-15 caster we will show you how to set this up in step 9. If you plan to make your own stub axles you will need to make sure that the camber is set up a 0 degrees and the ackerman angle is correct. this will be covered in step 12
Step 3: Designing the Frame
This is the design that we did for the go kart we got the distant of the wheels (wheel base and Track) from a internet deign of a go kart. We based the frame off previous go karts and scaled model go kart. We are making the frame out of 30mm square tubing and 25mm round tubing and 19mm round tubing for seat supports and the steering column just to make it easier to work with.
- So few things to consider, first the wheel base and track need to be approximately the same as a race kart, so 1040mm wheel base, and around 680mm between the king pins. This will give us the best handling kart as most race kart are pretty close to that size.
- The front wheels need space to move as they steer, you don't want a tire rubbing on the frame.
- Multiple bend are difficult to make so keep the frame a simple as possible
- The rear axile is likely to bend if the bearings are too far from the wheels, make the frame wide at the back.
- Four stroke engines a wider than race kart engines and are difficult to fit on the side of the kart
- The chain has to be able to be adjusted
- The rest of the design it up to you as long as everything fits (including the driver) and the kart looks good the rest of the measurements are not that important at this stage
- It is useful to draw everything full size on a workbench and lay all the part and driver out so you can kind of "join the dots"
- The driver is the most important part, so the driving position should be comfortable and the top of the steering wheel around shoulder height arms and legs slightly bent
- The steering angles have to be correct but more on that later.
Step 4: Frame Jig
The Jig for the frame is very important, it holds all your frame parts so they don't move and keeps every thing flat, straight and square.
Fortunately a jig is not to difficult to make, You just need a sheet of plywood or MDF, some small blocks of wood and some screws.
- Start by drawing a center line down the middle of the sheet and use that line for all your measurements and angles.
- Draw your kart frame full size, and put your motor, seat, axles, pedals and driver on the board as well to check everything is going to fit.
- Its much easier to change the drawing now that change the frame later on.
- Once you have checked and rechecked that the drawing is correct, you can start cutting steel and laying it on top of the drawing.
- We decided to put the engine behind the rear axle which is an unusual design but works really well
- The engine mount can be made with four 30mm square tubes. We used four 9mm drills as spaces so the engine bolts slide between the tubes.
- It very important to then lock each piece into place with three blocks of wood so accurate measurements can be taken to cut other parts. This is especially helpful if you have several people working on the project, as they can see what is missing and a quick measure and they can go away and cut that part
Step 5: King Pins
The king pins are the pivots for the front wheels :) The size that we needed the king pins had to be 50mm in length and 25mm in diameter
- Start by cutting a 55mm lengths off a steel solid round.
- Using the lathe and the pieces you just cut off, you now use them to create the hole in the middle, the hole should be 8mm in diameter, start off with the center drill and create a hole about 10mm in
- Using a 8mm drill bit you can create the rest of the hole, make sure to lube it up every now and then otherwise you can break the drill bit
- Now that you have your hole use the cutting tool on the lathe to face each end to take off the excess 5mm
- Sand off the sharp bits and now you have your first king pin
- Repeat from step one to create your second one :D
Step 6: Steering Bush
We are making the Steering Bush for our class Go Kart. We are using the program PTC to recreate the Steering Bush with a 3D printer.
After making the steering bush, you will have to remove scaffold on the steering bush and file the holes slightly because the 3D printer make the holes about 1 or 2 % undersize.
if you don't have access to a 3D printer the steering bush are quite cheap to buy you could try ebay or a karting store. There are a few different styles and they generally come in 2 different shaft sizes, 19mm 20mm. So check you have correct size tube and steering hub so everything fits together
Step 7: Steering Column
The steering column was rather easy to make, it was just a little bit difficult to get the measurements correct. It took around three hours to make and around half an hour to shape and put the holes in it. Below is a screen shot of how much a Go kart Steering column would cost brand new on eBay.
- We drilled the holes in it with a drill press set on a low speed. Once the holes were done we started cutting it into its basic shape just by putting it in a vice and using a hacksaw.
- We were pretty much finished, all we had to do now was get a file and curve the edges so it looked better. The Steering Arm was now finished and ready to be put onto the steering column.
- The steering column is just a piece of 19mm tube with a bolt welded in the bottom, make it longer than you need as you can always cut it down when you fit the steering wheel
- We used a drill press as a jig to hold everything straight while welding.
Step 8: Steering Hub
The steering hub is the part connecting the steering column and steering wheel. We are making ours out of a chunk of aluminum, but if you are unable to make it they sell for on ebay steering hub. The steering hub was made on a lathe out of a cast piece of aluminum, and do take a bit of time to make.
A few pointer to success,
- Go kart steering columns come in two diameters 19mm and 20mm. so make sure your steering bush and tube are the right size before you start.
- We used the steering wheel as a jig to get the mounting holes in the correct place.
- Mark the location of the first hole and use a 5 mm drill and 6mm tap to put a thread in the hub
- Bolt the steering wheel on and use a 6 mm drill to mark the center of the other 2 holes.
- You can then drill the other 2 holes 5mm and tap them with a 6mm tap.
- One side of the steering hub has a large hole in it. this is so the head of the cap screw tightens up on the tube not the hub. This has the effect of slightly crushing the tube inside the hub and making a tight fit that does not come lose.
- The hub can be removed by removing the cap screw.
Step 9: King Pin Jigs
Setting up the king pin angles is the most important part of building your kart, No matter how good your kart looks, if it wont go around corners, it will not be any fun.
- Just cut your self 2 plates and drill 4 holes so that they can be screwed down to your frame jig. Then weld an 8mm bright steel rod to your plate making sure you get the 2 angles right.
- K.P.I. or king pin inclination is the angle that the top of the rod leans in toward the center of the frame and should be 10 degrees.
- The caster angle lean the rod back towards the back of the frame and should be 12-15 degrees.
- These two jigs are a mirror image of each other so make sure you mark them left and right. The can be quite difficult to get the angles right, so spend a bit of time checking that they are correct, so you don't end up with a kart that doesn't turn one way properly or wants to drive in circles when you let the steering wheel go.
Many first time builders have told me that my steering angles don't look right, trust me they look a little weird the first time you see them but if you weld the kingpins on straight up and down your kart will not turn or steer.
You will find two drawings that you can download and print out which will help you to get the angles right if you don't have a protractor.
Step 10: Fun With Tube
We used 25mm OD tube for the front and rear bumpers and 19 mm OD for the top bumper mount, seat mount, steering column and steering column mounts. Using a tube bender can be a little tricky, you have to remember that each bend has a beginning and an end and it uses up material as you bend it. So it is a good Idea to remove the die from the machine and lay it on your Jig to give yourself a better idea of where the tube will lay after it is bent. Also cut more tube than you think you will need as you can always cut a bit of each end to get it to fit.
- The first bend is easy, its the second one on the same tube that you realy need to think about.
- Make sure you think about where the bend starts, as Ive lots of students bend the second curve in the wrong place and the bumpers end up too wide. (By the same distance as the width of the die)
- To get the two bends exactly the same angle and length it can be useful to draw around the bumper and then flip it over, as it give you a great visual on the symmetry of the part your making.
- Another tip is if you over bend the tube and need to straighten it a few degrees give the bend good smack on a concrete floor (it works surprisingly well)
- The end of the 19mm tube can be crushed in a press and drilled to use for seat and steering column mounts. Just remember to round of the sharp edges as it will rip trough a go kart seat or your leg if left with those sharp corners on them.
Step 11: Pedals
The pedals are made out of 13mm steel pipe and were heated by a Oxy acetylene gas plant and bent into shape. We copied a racing kart pedal, so they have a bend in the upright to stop[ your foot from sliding off the side of the pedal. The pedals are a mirror image of each other, and have a piece of flat with holes for the brake and throttle cable.
- The holes allow you to adjust the way the brake and throttle responds, as you can have a very hard brake pedal (when adjusted to the top hole ) or a soft brake pedal if the cable is fitted to the lower holes.
- If you don't have a pedal to copy, you can use a piece of wire to create a template then you can have custom pedal to match your foot.
- The 2 bends are 90 and 135 degrees.
- Use a piece of pipe as a handle when bending your tube.
- Care need to be taken so the tube bends without collapsing. Heat the tube all the way around and move the heat along the tube as you bend.
Step 12: Stub Axels
You can make your own stub axles, or buy them ready made. It is much easier to make them in four pieces as shown in the the photo and use the stub axle jig, the king pin and the wheel to hold the parts in place while welding. On our kart we drilled a hole in the end of the axle, tapped a 10mm thread and used a bolt to fasten the wheel on.
- When welding use the wheel without a tire as a jig, it should sit flat on the bench when the wheel is in the straight ahead position.
- The angles will look a little strange (not square) , this is normal.
- The two steering arms should be welded on last, with the holes from the kingpin, and end of the steering arm forming and imaginary line to the center of the rear axle
- The drawings have all the dimensions you need
Step 13: Brakes
We used a cable brake caliper designed for use on cheap go karts, fun karts or buggies. The mount doesn't take long to make, and has to be strong enough to keep the brake caliper straight and take a far amount of abuse. It also needs to have a hole in the middle so the brake pad adjustment screw can be access.
- We used a large hole saw on the drill press on its lowest speed to cut the large hole.
- Use cutting fluid or lubricant on the hole saw to keep it cool or it will rip all the teeth off as it over heats.
- The two mounting holes are 80mm apart between centers
- We used 100mm x 6mm flat mild steel
- The corners are cut off for safety and it also looks better than having the end square.
- Don't weld the mount on until after the the axle and brake disc is bolted on.
Step 14: Welding
We are using a MIG to weld our go kart together as they are a very quick welder there a lot quicker than and ark welder, and you don't have knock the slag off after your finished welding.
- If you have never done any welding before it is worthwhile getting a few hours practice before you start welding the frame. Before you start make sure all the parts fit, if you have any large gaps either cut a small piece to fill in the hole or cut a new piece of steel.
- This is not a project you want to learn to weld on, if the kart falls in half while your driving it would not only be dangerous but also hilarious.
- It is really important that you tack the whole frame together and check that everything is straight and square.
- Use the seat as a jig by bolting the the supports to the seat and tacking them in place. The seat can then be removed
- Don't weld the brake calliper or the arm on the steering column until the rest of the kart is assembled.
Step 15: Floor and Chain Guard
You kart will need a floor so weld in some tabs so it can be bolted on with 6mm bolts and nylock nuts. The floor and chain guard are made with 1.2mm thick aluminium sheet, and is left unpainted as the paint would soon wear off near the pedals as your shoes rub against it, and aluminium looks cool anyway.
- You will need 10 or 12 tabs and 6mm bolts, with nylock nuts
- The tabs are made from 25mm x 3 m flat
- Make sure you round off the ends or as the sharp corners will cut and crack the floor.
- The Kart frame can be layed on top of the aluminium sheet and traced around with a sharpie to get the shape of the floor.
- It can then be cut out with a nibbler. Again look out for those sharp bits.
Step 16: Assembly
In this step we made sure that everything fits probably and finished off the welding and assembled the motor and axle. One of the things we should of documented a bit better is how to build the rear axle, But it is one of the easiest parts of the kart so you shouldn't have any problems with it. We used 1meter of 30m solid bright mild steel, and fitted the sprocket, brake disc bearing and wheel hubs. We then fitted this to the kart and slid the sprocket and brake disc to the correct positions. The axle then had these position marked and it was then sent off to a machine shop to have the key-ways cut in the shaft.
- The position of the can be changed a little forward or back to fit the driver.
- The axle and engine must be straight and square when fitted.
- The floor and seat can be fitted.
- Keep the chain as short as possible.
- The engine need to be fitted with large washers under the frame.
- One of the last things to weld on is the brake caliper mount. Use the caliper and disc as a jig, and put a spacer under the caliper while welding to keep the spacing on the brake pads correct.
Use a cable tie to hold the brake pads tight on the disc, this will ensure the caliper is straight, the mount can now be tacked in place
Step 17: Steering Arms
The steering arms are made from thick walled 1/2 inch tube with bolts welded into each end. They are not too difficult to make but they need to be the correct length and the bolts need to welded on perfectly straight. If you are able to buy two left hand threaded bolts and nuts, put a left and a right hand threaded bolt on each end, and you will be able to adjust the toe in with out removing the steering arms.
Unfortunately we could not find any left hand threaded bolts locally, so to adjust the toe in, one end of the steering arm has to be disconnected.
- First bolt the rod ends to the kart and screw the adjustment bolts in half way into the rod ends.
- With the wheels straight ahead and the steering wheel centered carefully measure the length of of tube needed .
Also move the arm on the steering column up or down so that the pivot points on each stub axle and the steering column are in a straight line.
- Both tubes should be the same length, if you have a tube cutting or lathe it will be easy to get the ends nice a square.
- We used a drill press to hold the bolt straight and tack welded it into place
- Repeat on all four ends and check everything is straight and the right length (test fit on the kart) before fully wielding.
Step 18: The Little Stuff
Its the little stuff that can be quite time consuming, Attaching the pedals in the correct spot, pedal stops, making the steering arms, cable holders, fitting the steering wheel to the correct height and attaching the brake can be fiddly.
A throttle cable can be connected to the governor arm. We used a bicycle brake cable and a screw down electrical connector with the plastic removed.
The steering wheel can be bolted on The cap screw crushes the tube inside the hub, to give it a tight fit.
Step 19: Testing
Our first run went really well, the only things that were a slight worry was that a small screw came loose underneath the steering wheel and the back wheel slid slightly down the axle so nothing disastrous happened and nothing came off. For a first run, we couldn't of asked for a better go. The kart reached up to 40 km/h so it went really well.
Step 20: Fitting Racing Bodywork
The front bumper simply clips on as it has the same mounts as the old bumper, but brackets have to be made for the side pods and front panel.
Not to difficult but the two side pods will have to be mounted exactly the same distance from the back wheel and the same height and angle or your eye will pick it as been "wrong"
- Make sure the karts tires are pumped up or sit the frame on blocks so the side pods are the same height from the ground.
- Don't weld anything until all the parts are made and fit correctly
Step 21: Strip Down
On our kart someone did a very poor job of cutting the bars for the side pods, so some tube was cut to fill in the gaps so it could be welded properly.
- It a good idea to put all the parts and the bolts that go with them, into containers and label everything to make it easier to assemble.
- The frame must be cleaned with a solvent to remove any oil or grease and given a quick sand to help the paint "key" to the surface of the steel.
- Go kart frames are quite difficult to paint as there are lot of difficult angles so make sure to check that you haven't missed spots before packing up the spray gun
- Give the paint time to harden up before assembling I recommend a couple days sitting in the hot sun.
Step 22: Paint
Painting a gokart frame is is quite difficult as there are so many tubes and funny angles for you to miss. Even hanging the frame up to paint, is not going to cut it as there is always something thats not painted. I recommend painting everything you can see and fliping the frame over, even if you have it hanging from wires. We ended up painting the bottom side first on a table then flipping the frame over, as it was easier than trying to paint it while hanging.
There are a few tricks to using a spray gun as it has a number of adjustment, But first make sure you stir the paint and thin it correctly with the recommend thinners. The paint can will usually tell you what % to thin your paint for spraying.
Step 23: Reassemble
Only a couple of thinks left to do reassemble the kart, and then check everything before you go racing, things to check include
- The toe in should be set at 0 degrees or slightly toeing out 1or 2 degrees.
- Chain should be adjust and aligned so the sprockets are parallel and on the same plane.
- Brake cable needs to be double checked
- Throttle cable needs to adjust so the pedal reaches it stop, to protect the carburetor butterfly from damage.
- Throttle also needs to be checked to make sure it cannot be stuck wide open.
- Every nut bolt and screw needs to be checked every time you take the kart out, as karts are subject to lots of vibration things tend to work lose.
- Petrol, oil, tire pressures and lets go racing!
Step 24: Racing Photos
We were lucky enough to get to a few hours at a race track, and the Kart preformed really well, despite the photos due to a crappy camera! Even thought the kart has only four horse power, it was more than enough to spin out in the corners if your not careful. The wheels didn’t fall off and there were not mechanical problems on the day.
The Students had a great time and one kid said "I never thought the drive a kart could be so much fun"!.... then she went a did another 50 laps.
Step 25: Year 10 Class 2015
In 2015 the year 10s designed and built another kart, this one a little different, as it has a CVT gear box. The gear box makes it accelerate like a cat thats caught fire, and it makes the kart even more fun to drive. You can get the gear box from cut price racing, and apart from the size making it a little difficult to squeeze on the frame, the conversion was very straight forward, bolting straight on the side of a Honda GX style engine with a 19mm shaft.
Step 26: Class of 2016
In 2016 I run three go kart classes, and they decided to put the engine on the side. The project was quite a bit more challenging as fitting the motor and driver into the space takes a fair amount of thought. This year to get the class started with younger kids we have striped a kart down, painted and reassembled the kart before starting on a new design. It seems to help keep the kids motivated and gives them a better understanding of how karts are designed.
Enjoy the photos, and the video of Chad drifting into a mud hole.