Spot welding engine bay

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Zamani
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Spot welding engine bay

Post by Zamani » Sun Mar 06, 2011 1:51 pm

Guys,

I'm slowly trying to spot weld the seams in the engine bay. I figured, it can only help stiffen the front end. Especially the seams at the shock towers.

Finally found the correct heat setting for my MIG welder so that the beads would actually not be too big (not hot enough originally).

Has anyone done it? Felt the positive effects?
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Re: Spot welding engine bay

Post by la_strega_nera » Sun Mar 06, 2011 3:05 pm

Zamani wrote:Guys,

I'm slowly trying to spot weld the seams in the engine bay. I figured, it can only help stiffen the front end. Especially the seams at the shock towers.

Finally found the correct heat setting for my MIG welder so that the beads would actually not be too big (not hot enough originally).

Has anyone done it? Felt the positive effects?
I did it on the front of the Falcon race car I was building - reduction in the flex of the front end was notable when jacking the car up.
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Re: Spot welding engine bay

Post by Giuliettaevo2 » Sun Mar 06, 2011 3:14 pm

If your using a think AR-bar also weld the box-section where it mounts too... :wink: Much stress goes into those mounting points and they tend to tear at that spot.
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Re: Spot welding engine bay

Post by Zamani » Wed Mar 30, 2011 8:14 pm

Well I jacked up the front end of the car and place jack stands underneath. Much less flexing and the doors can open and close properly. I'm sure there is still quite a bit of flex but I may have reduced it. Remember I just spot welded many points, not seam weld, at the strut towers and the the other piece behind the tower close to the firewall.

Now I will add the reinforcement underneath the front fender as discussed with Maurizio a few months ago.

Last thing is to add a strut brace. Not so much to do what it does in a mcfearsome stut cars, but to stiffen the chassis. I already added a front bump brace, thoug I'm not sure if that will do anything noticeable.
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Re: Spot welding engine bay

Post by Duk » Wed Mar 30, 2011 10:27 pm

Zamani wrote:Well I jacked up the front end of the car and place jack stands underneath. Much less flexing and the doors can open and close properly. I'm sure there is still quite a bit of flex but I may have reduced it. Remember I just spot welded many points, not seam weld, at the strut towers and the the other piece behind the tower close to the firewall.

Now I will add the reinforcement underneath the front fender as discussed with Maurizio a few months ago.

Last thing is to add a strut brace. Not so much to do what it does in a mcfearsome stut cars, but to stiffen the chassis. I already added a front bump brace, thoug I'm not sure if that will do anything noticeable.
If you are adding a 'strut brace' ( :P ) I think it would be ideal/preferred to make it a 4 point design that joins the box sections that run from the A pillars down to the chassis rails and the box sections that have the top control arm bolts and shock absorber bolts.
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Re: Spot welding engine bay

Post by Zamani » Thu Mar 31, 2011 12:39 am

Hehe strut..... I was thinking of 3 points. Connect the shock towers to each other and also to a single point below the wiper motor on the engine firewall. So it becomes a triangle.
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Re: Spot welding engine bay

Post by Zamani » Sun Apr 03, 2011 10:49 am

Some updated pics of inner fender brace. I think a brace is a bad idea for a full time street car, you will compromise the crumple zone. But for a 80% track car, not too bad of an idea. But for a race car, don't wast time with this, go with a full cage which extends into the engine bay.

I intend to only put a few spot welds between the brace and the body of the car in case I don't like the idea and decide to take it off.

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Re: Spot welding engine bay

Post by Maurizio » Sun Apr 03, 2011 10:42 pm

ah I completely missed out on this one.

Z, hate to say it but your spot welding isn't really effective.
When you really want to add stiffness, you need connected the sheets together without a bend in the sheet. And make it look like a square section tube.
So weld as close as possible to the vertical sheets metal. Best would be, mill some small holes from the wheel side of the fender and weld from there, which is pretty difficult to do.

Easiest/practical to weld, melt though the upper sheet as close as possible to the bend, make sure the melt goes through the lower sheet.
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Re: Spot welding engine bay

Post by Zamani » Mon Apr 04, 2011 9:22 am

Point taken.

But as you said it is difficult to do and all the photos I see of is people seam welding the way I did (except I spot welded). I'm afraid to seam weld, might warp the sheet metal as it is very thin. If seam welding I should ask a better welder to do it, not me.

I think what I can do is from the wheel side is drill a few holes 1/2 way, till it hits the other sheet metal. Maybe 5-6 spots on each side of each shock tower should be ok? Then spot weld and melt the 2 sheet metals together.

But already I notice the added stiffness, especially when jacking the car up. Usually, when I open the door, it would not open without some resistance. Now no problems, and that was without the brace!


What do you think about the brace?
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Re: Spot welding engine bay

Post by Maurizio » Mon Apr 04, 2011 10:17 pm

The spot welding done by alfa is really bad, so everything you add helps :D
I think what I can do is from the wheel side is drill a few holes 1/2 way, till it hits the other sheet metal. Then spot weld and melt the 2 sheet metals together.
Actually this is what I meant, it is very easy to melt two sheet together like this. The hole drilling is the hard part. Warping isn't an issue if you take it easy.
What do you think about the brace?
First of all, same story as the seam welding. Try to let the (vertical) side wall of the square tube align with the vertical sheet of the a-pillar.
Best would be to let the tube protrude into the a-pillar. And weld it onto the sheet it hits, plus around the hole you make in the a-pillar. Also spot weld the tube to the side wall (red dots).

To save some weight you could make some holes (sort off like the green dots) in the vertical wall off the square tube.
Hole diameter ~ 60% of the inner square diameter of the tube and 3x hole diameter (hart to hart of the hole) pith. But make sure you don't have a hole underneath the sheets of the shock towers.
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