silly question but a a complete novice to metal work so here goes............I am making some brackets up to fit my trials chair to a bike. what thickness of steel should I use to make the brackets? I am learning to mig weld and can just about do steel so stainless and ali are out of the question for now.

No idea what is normally used on such and will depend upon year of bike and frame design accordingly. Might contact MRS for help or examples, yet if you can barely weld with Mig, you may be well advised to stay off this and find yourself a decent Tig welder as needed before you botch it up!

Good money spent there!

Does tig make for an easier/better weld?

I am looking to put the chair on a 159 bultaco or a 301 fantic.

I want to do all fabrication and welding myself as you will never learn by paying for some one to do it for you.

its harder to tig weld I think but tig welding is stronger than mig I can weld biut totally agree with bultoboy there is going to be a lot of strain on these welds and although the weld may look ok it could be more so a surface weld.

surface weld is where the weld is on the surface and not melted or eaten in to the two pieces of metal.

the weld may look ok but it will be as much use as a chocolate t pot.

also consider the brackets are going to be quite thick and don't attempt if your not using at least a 180amp mig or you will be wasting your time anything under

this ampage just wont get hot enough for the welds on the thickness of metal used .

hope this helps

As again I have no idea just how this is normally done by others, but I would find examples if I were you. I would think some type of clamp-on brackets may be preferable as trials frames are thin wall metal, and a large bracket welded to it may just pull right out of the base material.

And yes, the Tig offers much better control and a better outcome if done properly.

Edited August 4, 201313 yr by copemech

Tig would be best but is hard to do right. Mig is easier than ark welding and by the sounds of things you are just learning how to weld.

No offence but I dont think you should be learning on something like a chair that will have some poor dude riding inside. It would be a spectacular FAIL if your welds parted.

Ok I have had most people I know say the same about welding.

I think i will have to spend some money and give it to some one who knows what they are doing.

Ok I have had most people I know say the same about welding.

I think i will have to spend some money and give it to some one who knows what they are doing.

why not use MIG to tack it then take it to someone to TIG? I do that on my roadracing sidecar when I need to change things.

Hi Bultoboy,

MIG welding is fine for this job!

I made the brackets to fit my chair to my Bultaco from 3 mm and 5 mm plate. You should try to pick up on the swing arm bolt and the foot peg mount with your first bracket. Then the front engine mount/bolt with the front lower mount. Front upper mount can pick up on the headstock web under the tank ( make sure it's low enough to clear the tank)

My 14 year old son did most of the welding on our chair as a learning project.(yes some weld's were ground out and done a second time. But we have had NO breakages)

So go on give it a go!

Edited August 13, 201313 yr by p@ul250

Metal thickness? Near impossible to answer, depends if its in tension, compression or subject to torque etc. If your tube has a wall thickness of say 1.6mm then a good guide is to make the brackets about 1mm thicker, ie 2.5 or 3mm.

As a previous poster says a frquent MIG problem is lack of fusion or cold lapping by not melting into the metal. As a general guide use 40 to 50 amps per mm of metal thickness. Get some metal same thickness as on you sidecar and practice. Flex your practice welds until they break. the break should occur in the metal, not the weld. Clean the metal thoroughly and heat it with a propane torch before welding. Heat it until is is dark straw colour and then weld fast before it cools.

Argon with 5 % CO2 is probably the best gas.

Cheers

Edit added - suggest you read Performance Welding by Richard Finch.

Edited August 12, 201313 yr by dadof2

bultoboy

Just have a look at the welds on your dad's Bultaco!

look at the size of the web's used in it's construction!

If you use steel of the same size and can do a weld as well as a drunk Spaniard after Friday lunch GIVE IT A GO!

Welding isn't rocket science. The only way to learn is to try!

We have been bashing our outfit about for coming on for six months now. Running in to tree's. Rolling it down bank's and bouncing of rock. NOT ONE WELD HAS GIVEN WAY!

My Beta Evo will be fixed to it's chair by three M 8 BOLTS. That is all it need's.

thanks for all the help guys.

big thanks to paul who shares my attitude of give it a go and try, I have the day off work today and have found a happy medium.

I have found via my mate, a proffesional welder who is out of work and is willing to weld the outfit with me and teach me a bit about welding. Basicaly he is watching me weld and will point out any mistakes and correct them.

The waters have broke! a new outfit should be born by the weekend.........watch this space.

The examples pictured do reflect what I was trying to get across, notice nothing is welded to frame, all bolt on bracketry. no clamp on brackets used, however on different bikes that may still be an option. Don't look too bad either. Good welder can make MIG look better even, takes practice though!