MGExp

MG Midget Forum

WELDING QUESTION

Moss Motors
AutoShrine Sponsor
AutoShrine Sponsor
AutoShrine Sponsor
AutoShrine Sponsor

WELDING QUESTION
#1
  This topic is about my 1967 MG Midget MkIII
Yankeedriver Avatar
Yankeedriver Platinum AdvertiserAdvertiser Joel Young
Albuquerque, NM, USA   USA
Gentlemen (and ladies, too, by all means):

I need to MIG weld mild steel tubing with .058" wall (so, roughly 16 gauge) to 1/8" thick x 3/4" wide mild steel bar. The bar rests the long way with its 1/8" edge against the tubing. The only force exerted on the weld in the application is effectively to pull the bar away from the tube; no significant torsion will be exerted along the joint.

So, here are my questions for the experienced welders on the forum:

First: for best adhesion and strength, should I radius the edge of the steel bar to match that of tubing, such that the fillet lies in a tight corner (as viewed from a cross section of the two components fitted together). Or would it be better to leave the gap formed by the square-edged bar against the round tubing? It's not very big, I guess, due to the 1/8" thick bar, but it's there.

Well, a third possibility occurs to me. I suppose I could radius the bar to match the tubing, then break the edges of the bar a little to make a smaller, custom-sized gap.

Second: should there be fillets on both sides of the bar? I'm guessing one would do one side, let it cool down, then do the other. But wouldn't it be less likely to pull off if there were dual fillets...? Or maybe an inch-long fillet on one side, then alternate to place the next inch on the other, or...? The whole affair is 3" long, by the way.

Finally: any tips for determining the best setting for dual-thickness welding? I've read both views--that you should aim for penetration appropriate for the 1/8" bar and keep the wire focused mainly on it to avoid blowing through the thinner material, and others who say you should match heat to the thinner material in a mismatched thickness joint, and use thinner wire, too.

Anyone done something like this? Tips and tricks? I would like to start next weekend's attempts with the benefit of experienced welder's suggestions to save materials.

Thanks very much!

Joel


Member Services:
Innovative DIY performance and reliability upgrades.
S1 Elan Kurt. Appley
Akron, Ia., USA   USA
Don't champher the thicker piece but grind it to fit the thin tubing precisely. Direct the welding heat into the thicker piece as much as possible and don't pause. The best thing you could do is a practice piece first if you are unsure. A amperage lower than normal for the thick piece but a little too high for the thin. That is how I would do it but you could also run a low amperage bead on the thin and then join the two with a higher amperage on top of the bead you have run on the thin piece. Brazing works in a situation like that as well.

Kurt

. Hide banner ads & support this website by becoming a > Gold Supporting Member <
Yankeedriver Avatar
Yankeedriver Platinum AdvertiserAdvertiser Joel Young
Albuquerque, NM, USA   USA
In reply to # 3695358 by S1 Elan Don't champher the thicker piece but grind it to fit the thin tubing precisely. Direct the welding heat into the thicker piece as much as possible and don't pause. The best thing you could do is a practice piece first if you are unsure. A amperage lower than normal for the thick piece but a little too high for the thin. That is how I would do it but you could also run a low amperage bead on the thin and then join the two with a higher amperage on top of the bead you have run on the thin piece. Brazing works in a situation like that as well.

Kurt

Thanks, Kurt. And beads on both sides of the bar when it meets the tube, or just one? I was thinking do one side, let it cool, then hit the other?

Joel


Member Services:
Innovative DIY performance and reliability upgrades.
S1 Elan Kurt. Appley
Akron, Ia., USA   USA
Joel, I'd recommend at least running a bead on a price of scrap the same thickness as the thin tube to get a feel for it first before you risk your part. if the part is moveable position sometimes helps. You would want the weld metal to flow towards the thin section even though you would be concentrating the heat on the thick.

Not my profession but I've done quite a bit of welding since I first started at around 15. Retired now.

Kurt

Yankeedriver Avatar
Yankeedriver Platinum AdvertiserAdvertiser Joel Young
Albuquerque, NM, USA   USA
Thanks, Kurt. I'll get some extra material and spend next weekend experimenting before commencing the first actual mount.

Joel


Member Services:
Innovative DIY performance and reliability upgrades.
humbucker Avatar
humbucker Silver Member Paul Whitworth
Toronto, NSW, Australia   AUS
Hi Joel,

If this is what you mean (see pic) then tack weld one end, check for square and alignment with tube, then tack weld the other end.

Run a fillet on each side of the bar, lowering the amps to suit material thickness and direct the arc more towards the bar as it is thicker than the wall of the tube. Ensure the nozzle is angled about 45 deg from the vertical otherwise you will blow a hole. Don't pause during the weld and don't go too slow.

Maybe practice first.

Good Luck!

. Hide banner ads & support this website by becoming a > Gold Supporting Member <

Attachments:
20180312_182441.jpg    13.8 KB
20180312_182441.jpg

trevorwj Avatar
trevorwj Trevor Jessie
Louisville, KY, USA   USA
If paul's diagram is correct, then his advice sounds good. Match the heat to the 1/8" thickness steel. You will most likely will need experiment with your wire feed speed.

When you tack a bar on the first corner, it will draw to that side. You might want to shim the part out .025 or so before your first tack so that you have wiggle room to resquare it.

humbucker Avatar
humbucker Silver Member Paul Whitworth
Toronto, NSW, Australia   AUS
In reply to # 3695601 by trevorwj If paul's diagram is correct, then his advice sounds good. Match the heat to the 1/8" thickness steel. You will most likely will need experiment with your wire feed speed.

When you tack a bar on the first corner, it will draw to that side. You might want to shim the part out .025 or so before your first tack so that you have wiggle room to resquare it.

If you tack it and immediately put pressure on the bar away from the tack and hold about 10 seconds, it should stay square to the tube. (I do a lot of welding in my trade as a Fitter/Machinist for 40 years!)

Cheers.

trevorwj Avatar
trevorwj Trevor Jessie
Louisville, KY, USA   USA
I was suggesting the shim because I wasn't sure if he would not only need it perpendicular to the length, but also perpendicular to the tangent of the tube at that point.

I'm NOT a professional welder. As an amateur, I get better results using the shim method. smiling smiley

humbucker Avatar
humbucker Silver Member Paul Whitworth
Toronto, NSW, Australia   AUS
In reply to # 3695609 by trevorwj I was suggesting the shim because I wasn't sure if he would not only need it perpendicular to the length, but also perpendicular to the tangent of the tube at that point.

I'm NOT a professional welder. As an amateur, I get better results using the shim method. smiling smiley

Hi Trevor,

Using a shim is fine (as long as you don't tack weld the shim too, ha ha)

It's called presetting - it anticipates that the bar will bend towards the tack as it cools because of heat shrinkage.

As long as the shim is not so thick that you end up with a large gap beneath the bar which would cause the arc to blow through under the flat bar.

A shim of about 0.015" should be enough to allow correction to square after the first tack.

Cheers, mate!

. Hide banner ads & support this website by becoming a > Gold Supporting Member <
S1 Elan Kurt. Appley
Akron, Ia., USA   USA
As thin of material as he is welding to I wouldn't expect that realigning after the first tack to really be a problem. Best to do it while the tack is still hot.Yes to a fillet on both sides and personally I would TIG it. Just me but I have no fear of burn through on thin stuff when I TIG.

Kurt

Yankeedriver Avatar
Yankeedriver Platinum AdvertiserAdvertiser Joel Young
Albuquerque, NM, USA   USA
Dear Paul (and everyone),

This is very helpful and much appreciated.

Paul, I'm sorry that my description of the bracket wasn't clear. Here is a sketch of what I intended to describe.

Immediately below what I'll call Design #1 is a simple alignment jig I was thinking of making. I'd just run my half-round router bit along a bit of hard maple or oak I've got lying around, and clamp everything to prevent moving around. The 3/4" x 1/8" bar would ensure their remaining parallel in one plane, but it's also critical for alternator belt alignment that they are parallel in the other, too. Does this sound like a reasonable of ensuring consistency with the mounts?

Below those renderings is another option for accomplishing the same end: keeping the two long 5/16" alternator mounting bolts parallel in both planes. I was initially thinking of welding the ends of the tubes to this alternate bracket, but in looking at it wonder whether it even needs tubes...? That is, 1/8" plate (in this case, 2" wide) is fairly resistant to torsion, and there wouldn't be a ton of it exerted by the serpentine belt.

I am thinking that I need to pull the engine to work out these last few fine details. I now know where the blower needs to end up in 3D space to clear the right-hand inner fender and wiring loom running along it. The rear mount is sufficient to hold the blower in position while I work on an engine stand, and it's difficult to run a big straight edge along the various pulleys with the engine installed.

Joel


Member Services:
Innovative DIY performance and reliability upgrades.

Attachments:
alternator spacer bracket(1).jpg    39.4 KB
alternator spacer bracket(1).jpg

trevorwj Avatar
trevorwj Trevor Jessie
Louisville, KY, USA   USA
OK, I was just thinking that you would risk ripping the the tubing or deforming it if you tried to resquare it after the first tack without "presetting" it. (I learned a new term today)

. Hide banner ads & support this website by becoming a > Gold Supporting Member <
Yankeedriver Avatar
Yankeedriver Platinum AdvertiserAdvertiser Joel Young
Albuquerque, NM, USA   USA
In reply to # 3695700 by S1 Elan As thin of material as he is welding to I wouldn't expect that realigning after the first tack to really be a problem. Best to do it while the tack is still hot.Yes to a fillet on both sides and personally I would TIG it. Just me but I have no fear of burn through on thin stuff when I TIG.

Kurt

Kurt,

Thank you for this. I invested in a MIG setup rather than TIG, because it suits my various needs better. But I agree TIG would have been a great way to go.

Joel


Member Services:
Innovative DIY performance and reliability upgrades.
humbucker Avatar
humbucker Silver Member Paul Whitworth
Toronto, NSW, Australia   AUS
In reply to # 3695764 by Yankeedriver Dear Paul (and everyone),

This is very helpful and much appreciated.

Paul, I'm sorry that my description of the bracket wasn't clear. Here is a sketch of what I intended to describe.

Immediately below what I'll call Design #1 is a simple alignment jig I was thinking of making. I'd just run my half-round router bit along a bit of hard maple or oak I've got lying around, and clamp everything to prevent moving around. The 3/4" x 1/8" bar would ensure their remaining parallel in one plane, but it's also critical for alternator belt alignment that they are parallel in the other, too. Does this sound like a reasonable of ensuring consistency with the mounts?

Below those renderings is another option for accomplishing the same end: keeping the two long 5/16" alternator mounting bolts parallel in both planes. I was initially thinking of welding the ends of the tubes to this alternate bracket, but in looking at it wonder whether it even needs tubes...? That is, 1/8" plate (in this case, 2" wide) is fairly resistant to torsion, and there wouldn't be a ton of it exerted by the serpentine belt.

I am thinking that I need to pull the engine to work out these last few fine details. I now know where the blower needs to end up in 3D space to clear the right-hand inner fender and wiring loom running along it. The rear mount is sufficient to hold the blower in position while I work on an engine stand, and it's difficult to run a big straight edge along the various pulleys with the engine installed.

Joel
Hi Joel.

Are you the guy doing the blow through supercharger?

Making a jig and clamping every thing is the ultimate way to ensure everything stays aligned.

You should still tack the four corners of the flat bar and when cool, remove from jig, turn over and tack weld the other four corners. Check that everything is still in line then weld about 1" and turn over. Weld another inch then turn over etc. This should help prevent distortion of the tubes and spread the heat more evenly.

Cheers, Paul.

PS here's my supercharger set-up - draw through Toyota SC14 (1400cc) supercharger fed by one 2"SU. I didn't bother with a serpentine belt. Just made the charger pulley to suit an A section vee belt with a spring loaded belt tensioner.


Attachments:
20180313_175401.jpg    39.9 KB
20180313_175401.jpg

. Hide banner ads & support this website by becoming a > Gold Supporting Member <

To add your reply, or post your own questions




Registration is FREE and takes less than a minute!


Having trouble posting or changing forum settings?
Read the Forum Help (FAQ) or contact the webmaster