Are there any joints on the kart I should avoid welding? And how do I straighten my chassis? One weld is on the end of the seat stay (for context previous team “repaired” it and missed the crack) and the second one is on the right side bumper mount. Last picture was the old seat stay weld.
These two things are the last bits I need to address before I can put an engine on it and take it out to the track. Thanks in advance!
Really anything can be welded if it is done right (straight, HAZ, penetration etc.)
I have welded at least 3 of my son’s karts. I probably would have replaced the bumper bracket. Not because the weld won’t hold but because usually when I have seen them like that they pretty worn where they slide. Of course I would weld it anyway and throw it in the trailer in case I ever needed one in a pinch.
With things like that I worry about it failing and costing us a race.
For frame straightening you will find most big teams or tracks will offer that service. Some guys are good at it and some are absolute magicians.
Thanks for your wisdom man, that bumper bracket just had a terrible weld from factory so I fixed it, still got some life in it. Chassis straightening is like 200 bucks though I was looking for a diy solution for that. This is a pretty beat up frame and I’m not expecting it to last me a ton. Also it will probably bend back with a light crash or just with time.
Also I forgot to specify that I’m using a fluxcore welder, hence my question on what I should avoid welding since FC by nature is terrible for thing metals.
I have read some DIY frame straitening advice on here. What needs straightening? If you could a few pics that would help.
Someone charging 150-200 should have a good table that can do anything. Thiago charges 150 for a simple frame adjustment and 200-250 for more complex stuff like C hub adjustments. He is the best in the business.
Here is the thing on frame straightening: you can bend it easily, it’s just about controlling where you bend it. If you have a proper flat table and some way to tie the kart down and control where you bend it, you can do an excellent job of straightening. These frames are soft and don’t take nearly as much as you think to bend. But that also means you can bend somewhere you didn’t intend to very easily!!
As for the welding, I would avoid MIG unless it is a trackside emergency repair. I would have someone proficient in TIG welding perform the repairs. Typically these karts fail in the heat affected zone (HAZ) which is the base metal immediately adjacent to the weld. They are often MIG welded with no PWHT from the factory. This allows faster production, but can result in some residual stress in the HAZ areas of welds, especially on the smaller tubes like the seat. TIG lets you better control the heat input and reduce the residual stresses in the HAZ post welding. Pre-heating and post weld cool down could also be used, but why when you can just TIG!?!?
Having a guy tig weld the frames is expensive, tig welders chug gas, welders need to be more proficient, and it’s slower. MiG is faster, uses less gas, and needs a less experienced welder. I just use my fluxcore welder. I’m intending on buying a tig welder eventually though l, because I can’t live with myself if I keep doing fluxcore. Thanks for the help man. This is a fatty chassis so I don’t mind fixing the seat stays with fluxcore, I welded over the thin transition between the tubing and the plate so now I’m good. But yes, definitely tig welding in the future.
PSA: Welding together metal that’s already at the end of its fatigue life is going to result in the HAZ, which is already microscopically cracked, cracking even more quickly. If you perform a weld repair on a kart I’d recommend also welding a sleeve around it.
For straightening, there are more and less sophisticated systems out there. A ten foot pole, a pair of axle supports, and a height gauge works very well for correcting ordinary twist. I’ve done a good job at the track by supporting the low corner on a piece of firewood, having the track owner stand on the opposite corner, and jumping on the high front corner until the crossweight was correct.
Any welding will result in a haz, I’ll think about a sleeve but it’s going to be difficult since it’s the make some. Thanks for the help!
