To Weld Or Not To Weld? That Is The Question.
When we look at go-karts there are different fabrication techniques. It depends on what kind of go-kart you are dealing with, but there are different fabrication techniques in putting them together.
You can bolt them together. I suppose if you are really desperate you could rivet them together. You could even epoxy them together, meaning you could glue them together, or you could weld them together.
Basic Fabrication Techniques: Welding And Bolting
So the basic fastening options that you have to use are really: welding and bolting perhaps gluing or epoxing (or another way of saying having a body that is composite or a frame work that is fiber glass.) All these options are reliable and perfectly acceptable.
Welding is usually a preferred option when you are with a go-kart because it gives you greater freedoms as far as how many variables that you can get done. So you do not have to drill holes. You do not have to have a fastener. It can be done quicker.
Fastening or bolting gives you greater strength options in movement and variability and it is removable.
Combinations: Welding and Bolting
You can have combinations of bolting and welding which I would recommend.
When you are bolting and welding you are going to bolt a muffler on to the engine. You are not going to weld it on, you are going to bolt it to the framework so that it is removable and supported.
I would not suggest welding the muffler to the frame. Because if you need to remove the engine, then you just cannot do it very well. You will have to take a grinder out and grinding off the welds to access the part or what ever else you are trying to access.
How Easily Can I Work On This Go Kart?
One of the things to think about is when you are welding or choosing to weld or bolt is accessibility. How easy can I work on this thing?
So really we should title this article “How easily can I fix or maintenance certain items on the go-kart? “
Welding and bolting or gluing (whatever method that you are using) determine how easily it is going to be fixed.
The second option is to determine how strong your joint is going to be.
Third how quickly you can get the job done fabricating.
If you are talking about a wood go-kart you can actually have combinations to weld the parts and bolt on the parts.
So what we are talking about here really is involved in all sorts of go-karts and how they are designed.
Wood Go Kart Fastening Options
Let us start with the simplest of the go-karts and that would be the wood go-kart.
Obviously you can not weld to much on wood but you can do a lot with bolting. So the question would be what fastener should I use?
Well the fasteners that you should use on wood would be either lag bolts meaning that a wood screw bolt do you know what I mean? They are very heavy duty woods screw bolts that can handle bending. It also determines which direction the load is going well. On a heavily loaded part I would suggest you use larger fasteners to hold the thing together.
The obvious one, for instance, would be the steering mechanism. I have used a very large bolt, ½ in. bolt, for pivoting. I would not use much smaller bolts than that just because the stresses that are involved.
What you want to do is drill a hole and through both the steering beams. Put a bolt through and support the bolt with two washers. This then is a pivoting section. If you go smaller than that you have to risk shearing or breaking the bolt. Let us say you used a ¼ in. bolt, there is a high chance that you are going to bend it and break it.
So using a ½ in. bolt is a much better option, it is much safer.
As far as holding the wheels on, you can use a lag bolt that goes into the wood. We are not talking about tires right now, but in the Wood Go-Kart Section we talk about what kind of wheels you use. What you will find is that you are going to have difficulties, probably finding a lag bolt that is going to go into the wood and has a larger enough diameter.
So what you will be using is a smaller bolt with a bushing system around it. Or, you will end up making a welded rod that fastens onto an angle iron. This angle iron then has drilled holes in it. The angle then is fastened using screws of some sort, or strapping as in my case. That is how I did it to the board.
So the fastening options that we are dealing with here (on the wood) are, you can use a whole host of range of options. I would not suggest using glue primarily. Glue pulls away and delaminates. What you need is something that pentetrate all the sections of the wood. So the drywall screws actually do come in handy. For instance it penetrates all the sections of the wood. It can hold down a seat. They also hold down strappings.
Bolt Grades and Lag Bolt Types
Lag bolts are good for pivoting if you are mounting an engine obviously you are going to make sure that you use a heavier style bolt. I would use something greater than grade 2. Use something like a grade 5. You can get those at the hardware store. Grade 5’s have markings on the top.
I believe it is 6 markings if you look on the figure I will show you the different styles grade bolts and what psi they are rated at.
Now let us get on to the metal go-karts.
On metal go-karts you can use all sorts of metal styles and you can bolt it all together. You will have dilliculties and great challenges trying to bolt plates on to tubes. The reason that I am saying this is, because if the plate is being bolted on to the smaller tube (like a 1 in. square tube) you got to make sure there is no torque moment on it. If there is you have stopped the torque moment with 2 sets of bolts at least. Now the other problem is, if you have 2 sets of bolts spaced too closely together. They will shear or break.
You are going to run into the same problem with welding if you have a torque moment. On that spot you are going to tear the metal out too.
Stress and Shear Considerations
I would check into the Stress Section in our Go-Kart Guru website. That will help show you how stress is generated, and how to analyze the stresses. There are 2 types of stress there is pulling stress and shearing stresses and really what I am talking about here is a shear stress which is more so, than a tensional stress. The bolts are good in tension, that is really what we are driving at. The bolts are good at tension, not so good at shear.
If you are in a shear situation then you need to make sure that your bolts diameter can handle it.
Plate fastening the bolting or securing things together really, if I were to sum them up, it would include the following areas:
- mounting an engine
- mounting a brake system
- mounting a belt tentioner system
- mounting a muffler mounting a seat
- mounting the pedals for the throttle
- mounting the steering system cause you may want to move it back and forth
- mounting the steering column you may need to remove it and work on it
- mounting the rear bearings because those come on and off.
Obviously the bolts are going to be used for tie-rods you are going to use pins and so forth to hold your throttle cables. You may need to have a bolt mechanism for your throttle exchange system. Really what I mean by that is, on my go-kart what I have on my go-kart a throttle exchange system which is basically an arm with a spring on it. Because I am pulling forward, I actually crank on the arm. Then it pulls on the throttle and it gives me greater variability that way so I can change motors out. I do not have to be stuck with a broken Tecumseh or a Honda or any motor.
I just put a wire on to the mechanism, and hook it up to the throttle. The mechanism has a spring on it, I do not have to add additional spring systems to it.
Bolting Advantages in Certain Applications
So it gives me much greater variability on the engine that you want to use.
The way I set my go kart up is be a more research and development platform, so that I can change out super chargers and motors in a relatively short period of time. In fact because most motors have the same bolt platform (bolt circle or bolt spacing) there really is not a whole lot of changing there. I just pop them on and I have my new motor on it.
The prime example for bolting is my super/charger system. It bolts on the head of the cylinder head of the engine. If you want to take it off you just unbolt it, take it off and you are done. You just put on a new air cleaner and it is over. It is a simple system. I designed it that way on purpose, so it was a bolt on horsepower.
So bolting vs. welding is an important question.
Definitely Weld A Frame Together
I would highly recommend if you are putting a frame together of any substance that you weld. What primarily you are trying to do is use the strength of the material itself so the weld will grab approximately 75% of the cross area and join the pieces together. So you are getting a relatively good bond between two pieces.
Let us say you are dealing with a tube and you are welding it to another tube. If you butt them together and weld them all the way around you have about 75% of the area grabbed in a tension. Welding can be very critical if you design it at a high stress joint, so you may want to buttress that joint with a gusset which will help support that weld.
Basic Stress Considerations
You will have determine through your calculations whether or not that weld can handle it. If it cannot then maybe you have to ad additional support using a gusset. A gusset is a back up. Which we like to call in engineering “an increase in the cross sectional moment of inertia” which helps reduce the stress. The formula of stress equals the force-moment times the crossectional center divided by the moment of inertia or the ”I” value.
Stress = Mc/I
If your “I” value gets low your stress goes up. If your “I” value gets large then your stress goes down.
So to answer the question in the beginning “To Weld or Not to Weld”, I would highly advise if you are making a welded frame (you are making a steel tube frame) you should do some welding.
Now on my go-kart design there is a roll cage and the roll cage itself is designed to be of lighter material to keep the center of gravity down toward the center of the go-kart (down lower.)
Bolting On The Roll Cage
So I would recommend that you bolt on the roll cage. The reason for that is, say you want to transport it. In my designs (go kart plans) you can throw it in the back of the suburban. You can roll it in the back of the truck or van. If you have a roll cage on there it might be too tall. So if you can just unbolt it and then put it in the back of the vehicle with the go-kart, you will be all right. Then you bolt it on when you get there. If you want to keep that in mind that you are making a roll cage, but you may want to unbolt it so you can have better packaging options when you are moving.
Now the roll cage again is designed to take a roll over load, or say a direct hit in the front, like a tree falls on you or something, it at least stops the tree. It is not designed to be any thing integral with the frame as far as strength. Its design purpose is to keep the go-kart in a roll condition from being destroyed and the occupant from being hurt or crushed.
So you need keep in mind that it needs to be reasonably strong and fastened in place. It may actually get bent or twisted. If you plan on rolling the go-kart (or there is a high chance that you will roll it and in what you are doing) you may want to keep that in mind with the gage tubing that you are using and the fastening (how you are going to fasten it.)
You may want to fasten it a lot heavier than you normally would.
So welding and fastening you may end up determining that you are going to need to weld it if you are going to be rolling it.
If there is high chance of rolling it, the twisting moment on it is really what you are dealing with. You are going to have a high twist and you need to make sure that if you use a bolted on the fastener that it will hold it and not bend.
Basic Rules Of Thumb
A rule of thumb is “A welded system is stronger than a bolted system.”
So “To Weld or Not to Weld” it really comes down to the three things:
- What are you trying to access?
- How strong do you need it to be?
- How fast do you want to make it?