Custom Manifold...

[oliwb]

Alright here's one for you....I'm trying to fit a set of motor bike carbs to my Pinto engine kitcar and I've got my manifold designed. Now I've got the tough job of trying to make the thing! I've got some Aluminium pipe 4mm wall, 38 mm I/diameter, and I'm gonna mill up some plates to fit the pipe to. However whats the best way to join the pipe and plate? I've tried welding with aluminium wire and not had much success so I'm inclined to avoid this method! Would I be able to braze aluminium? or has anyone any experience with these sort of Ali brazing rods? Also on a related note I'm about to setup a BOC account for welding gas, what should I get. I'll prob mostly be doing mild steel, chassis and bodywork, though I'm gonna be doing alot of stainless work and aluminium/brazing (hopefully!) What are the disadvantages of having a 100% Argon gas shield?? I wont be welding thick steel prob 2-3 mm max....Or can I use a low 5% CO2 mix and still weld ali and stainless still??? Can't afford 2 bottles unfortunately, and little bottles are proving far too pricey! Thanks...Oli.

 

[sclurgess]

cant you just chop up an old manifold. thats what most people do

 

[malcolm]

That is a tough one - welding thin tubes to a thick plate in aluminium. The really easy solution would be to to make it out of stainless - that would be much easier to weld.

MIG welding with aluminium wire does take a lot of getting used to. It would probably be possible if you spent a lot of time practicing with similar shaped scrap bits of metal, probably using a brass heat sink inside the tube (if you could make it so it would come out again). Even then it would take a lot of practice, delicate technique and power setup.

Most of these manifolds tend to be TIG welded - it would be giving in, but taking it to a fabrication shop wouldn't cost the earth.

These aluminium brazing rods might be an idea, although I don't know anyone who has tried them. I'm going to be cheaky and try to blag a kit so I can try it out and write a review. They would probably work if you had a press fit between the pipes and the manifold to give the joint some mechanical strength that just needed tacking on and sealing.

For the gas, with aluminium wire you'll definately need pure argon. For brass brazing it's recommended as well. I was using argon for mild steel the other day, and it works OK, but the weld wasn't a lovely shape - seems to stand up a little from the metal as if I was using too low a current (penetration is normal). My preference would be use argoshield light (argon/CO2) for everything. If you need to weld aluminium then use pure argon for everything and put up with the slightly less tidy mild steel welds (no worse than gasless).

 

[oliwb]

thanks for the replies, firstly unfortunately I can't chop up an old one as they don't exist! The metal walls aren't particularly thin (4mm) So was thinking it might not be too hard! I've been using pure Argon on mild steel and it doesn't seem too bad? What does the CO2 actually do to it?? doesn't it help with penetration so would enable me to weld thicker stuff??? Thanks Oli.

 

[malcolm]

CO2 is supposed to result in a hotter weld. Argoshield also has a little oxygen in it that improves wetting and arc stability. In practice the weld seems to end up flatter, wider and neater with argoshield.

I'd been preparing a few new photos for the welding tutorial, but I'm struggling with making the welds look neat enough. Also the wire speed seems a lot more sensitive (same situation as yourself - one bottle only and that's argon at the moment). I'll change back to argoshield light when the bottle has run out.

 

[sclurgess]

what do you mean they dont exist. you get a standard pinto carb inlet manifold and chop of the carb end

 

[oliwb]

Problem is, the diameter's are wrong, the carbs are mounted at a 30 degree angle (off vertical) the cahssis rail sits higher than the inlet manifold and carbs have to sit above this....thus a manifold doesn't exist! Would make life much easier if one did....do people recon I should get pure argon or argon shield? Can you still weld ali and stainless steel with the argo-shield? Cheers Oli.

 

[Hitch]

If your welding ally/stainlees yo need pure argon.
If you dont want to percivere with the ally mig, jut take it to a fab shop. an hours work, £40 or so and its done. Or a Saturday morning job for one of the lads, £20.
If you do it yourself, take the time to make up something solid to bolt the flanges onto to minimise any distortion. You will need to skim it afterwards still.
When you make the plates up, if you aim to make the the pipes sit in snug, allow 4-5mm gap between the end of the tube and mounting face of the flange, so you can weld the inside aswell, just polish it up smooth with a die grinder once you have skimmed the mating surface.

 

[Nial]

Alright here's one for you....I'm trying to fit a set of motor bike carbs to my Pinto engine kitcar and I've got my manifold designed. Now I've got the tough job of trying to make the thing! I've got some Aluminium pipe 4mm wall, 38 mm I/diameter, .

Why are you making it in aluminium? Would you not be better making it
from thin walled mild steel tube?

An easier option you might have overlooked.

Nial

 

[^neo^]

Wouldnt even bother trying to MIG it........ it will look awful!
As Hitachi said, take it to someone who does TIG welding and bung them £20 to stick it together

 

[ray]

if this was me i would like to do it myself JUST to see if i can, love a challenge , anyway. how good do you feel when you d.i.y.? i love it