Rivets v Welding v Epoxy

bowie

1000+ Posts
Do I dare?

So I've discovered some patches in the floor of my car that will need sorting. Picture where the heal of your left foot lands, somewhere around there the steel has weakened, and is now open to the elements. So I'll have to sand it all back and have a proper look at how good / bad this is and then add some kind of material back. Bare in mind not for a road rego'd car so less rules to worry about.

Now being around race cars I've seen all sorts of weird and wonderful things. I have seen chaps whom have cut the complete floor plat out, and epoxy / fiberglassed directly to the left over bits of floor, perhaps overlapping an inch at most. Then steel / alloy brackets, perhaps 50mm wide in alloy with captive nuts from the bottom to allow a seat from the top and off they go.

I've seen folks run of to Bunnings to get some checker board, bend and cut to shape, cutting the rusty section out of the floor and simply riveting over the top, (after laying some wicked thick beads of poly-something around the opening) in a patch of various sizes.

Then of course the chaps that buy the correct width sheet metal, add some dimples via a press, cut flush, and stitch welds back into the floor.

When it comes to sh1t race car, are any of these necessarily "wrong"?

What do I mean by wrong? Well I'm expecting 10yrs worth of fun left at most from this thing, and even then that's probably a bit optimistic.

I've checked some of the sporting rules again (3D Sports Sedan) turns out I can remove ~49% of my floor and replace it as necessary. This sounds crazy initially, but with a cage in holding the corners together, I don't suppose the floor does anything other then giving you somewhere to bolt a seat to along with a bit of protection from the elements, ie, with a cage it really isn't a monocoque chassis anymore?

Thinking about how these things are made from la factory, I also note that most of the panels are only tacked together anyway, so as silly as riveting chequer plate as a patch into the floor, perhaps it's not that stupid (when used with a cage in place eventually).

This would be a different conversation if I had a welder, actually it probably wouldn't :D
 

COL

Alpine A110
I would be welding in a patch to replace the damaged bit of steel. For a quick fix you could patch with fibre glass and this would be pretty strong if you clean up the steel and also rough it up with a grinding wheel so that the epoxy has something to key to.

Cars from the R12 era were spot welded together, when they were turned into serious race cars they were then seem welded where every panel joins to make the car more rigid.
 

schlitzaugen

1000+ Posts
I feel your pain, Bowie. Welding is another one of those rabbit holes (along with painting/bodywork) I just want to keep as far away from as possible. Would be wonderful if someone would put together a short list of what is needed to weld thin metal so I don't have to experiment with my own money.

Anyhoo.

Your options are as you said, but there is another one even manufacturers use today.

Get some body polyurethane Sikaflex and glue the panels/patches together. That stuff is tougher than welding and it is used to hold panels together in brand new cars. Plus water tight. Not structural, but tough enough that thin metals like body panels will rip before it lets go. I think it is similar to the stuff used on bonded windscreens. Run a bead to your needs/specs along the edge, press together gently (don't go apeshit on it) to reduce the gap to say under 1mm, leave to cure, done.

Funny story, I was trying to save the outer skin on a boot lid and thought meh, I'll just cut the rusty inner frame on the underside in small sections and rip them off one by one, leaving the skin clean. The first one I tried was only about 20cm long and about 1cm width contact with the skin but it buckled the top skin and refused to come off. This was on a 1967 car (BMW) and it was the original factory bonding. I imagine they got even better since.

I think you may still have to form the repair panels somehow, so you have a nice fit with a consistent gap all the way round.

No rivets, etc needed.

Epoxy, bog, glassfibre is all rigid and will most likely crack, but this stuff is flexible and stays put if you leave a small gap so joined panels don't touch to rub against each other and shear it off.
 

jo proffi

1000+ Posts
Riveting is a neat easy and very strong way to join bits of metal.
I've cant remember doing bodgey repairs on cars, but in the past, my fave way to repair a hole in an aluminium boat was to pop rivet a patch onto the damage.

I'd be doing exactly the same in your position.
Make the new steel floor bit, goop around the edges with a product...urathane probably, then pop rivet it on, paint underside with underfloor goop and job done. The good thing with rivets is it forces the two surfaces together whilst the urethane dries so your fabrication skills don't need to be top shelf.
Jo
 

shibuichi

Member
We used Sikaflex as sealant with rivets to hold panel seams in place to raise the roof on a Ford Transit using a second Transit roof harvested from a wreck. Bolted aluminium profile joined the structural beams. Passed the engineering inspection.
 

bowie

1000+ Posts
And here I was reading up on flux cored welding and eyeing off small 10amp welders.

Once the Reno gets here, I no longer have daily access to a race track so I owe it to myself to have a proper look at the thing. I'll take the paint off properly and decide just how bad things are in those areas I've been neglecting... ..
 

Bustamif

Member
Don't take the paint off, it will only scare you and sit around the yard for the next 5 years. It's just a fun track car, not a restoration project.

My motto with race cars has always been (apart from safety issues) if it wont make the car handle better, accelerate faster or brake better don't worry about it.
 

DoubleChevron

Real cars have hydraulics
if your asking this question ..... your not confident in welding a patch in (simple enough, but very time consuming). Just sikaflex a patch in. clean (and prime) both layers of metal if required... remember to leave plenty of overlap for the urethane to take too. Use plenty of urethane and "squeeze" the layers together so you remove any air bubbles...... It'll be stronger than new :) If you google it there has been plenty of testing done. A well glued join is generally better than most other repairs.

Having said that .... . I weld everything :clown: ....... well I have a welder here, and every tube of urethane you open is generally wasted once opened. If you get a urethane adhesive, make sure you buy a decent silicon gun (the battery powered ones seem best). I've broken pretty much every silicon gun I've ever bought with the urethane glue/sealers. They are very thick when cold and almost impossible to tool to a nice finish :(
seeya
Shane L.
 

Kim Luck

1000+ Posts
if your asking this question ..... your not confident in welding a patch in (simple enough, but very time consuming). Just sikaflex a patch in. clean (and prime) both layers of metal if required... remember to leave plenty of overlap for the urethane to take too. Use plenty of urethane and "squeeze" the layers together so you remove any air bubbles...... It'll be stronger than new :) If you google it there has been plenty of testing done. A well glued join is generally better than most other repairs.

Having said that .... . I weld everything :clown: ....... well I have a welder here, and every tube of urethane you open is generally wasted once opened. If you get a urethane adhesive, make sure you buy a decent silicon gun (the battery powered ones seem best). I've broken pretty much every silicon gun I've ever bought with the urethane glue/sealers. They are very thick when cold and almost impossible to tool to a nice finish :(
seeya
Shane L.

An old trick from the transport industry to save you breaking your gun on a cold morning: drop the tube of Sika/3M urethane into a bucket full of hot water for a while before you start. Repeat if the urethane cools down too much before you finish.
 

bowie

1000+ Posts
Thanks everyone, that was a push in a direction I'm certainly comfortable with.

I am concerned mostly with the floor area, so I may just go ahead with a new piece of checker plate, cut the crap out of the floor, and well I kinda like the idea of rivets and sikaflex, ah I'll see when I get to spend some time with it. Going to try and pick it Wednesday if new job will allow. :)

I still think I'll get silly at some point and splurge with a small TIG / MIG and start playing because I missed out in high school. Gluing things with electricity appears like magic, and toys that are like magic are fun.
 

schlitzaugen

1000+ Posts
I think most people would advise you to stick to MIG, it is easier hence cheaper. TIG is quite a learning curve and this will cost serious money. Plus you're looking at sheet metal, which is the most difficult to get right. On the other hand, a car you don't really care about is the best target practice.
 

PeterT

1000+ Posts
Welding ferrous sheet metal is far easier with TIG than MIG. The price of AC/DC TIGs had dropped enormously recently. As a car buff, you’ll get far more use out of TIG.
 

DoubleChevron

Real cars have hydraulics
Welding ferrous sheet metal is far easier with TIG than MIG. The price of AC/DC TIGs had dropped enormously recently. As a car buff, you’ll get far more use out of TIG.
Do you have a TIG? I'd love to try one. Everything I've ever read says you need your patch panels perfect (TIGs don't fill hole/gaps like MIGS) ..... and its incredibly slow. Nothing looks like a nicely done TIG welded join though :dance:
 

PeterT

1000+ Posts
Do you have a TIG? I'd love to try one. Everything I've ever read says you need your patch panels perfect (TIGs don't fill hole/gaps like MIGS) ..... and its incredibly slow. Nothing looks like a nicely done TIG welded join though :dance:
Yes, I teach welding for a living. You can fill holes with TIG quite easily. Sure, it’s slower but less heat affected zone and looks better. The new kid on the block is pulse MIG. Sort of the best of both worlds.
 

DoubleChevron

Real cars have hydraulics
Yes, I teach welding for a living. You can fill holes with TIG quite easily. Sure, it’s slower but less heat affected zone and looks better. The new kid on the block is pulse MIG. Sort of the best of both worlds.

Maybe oneday I'll get a TIG welder .... Now we can own the bottles its not yet another big expense. I watch finnegans garages a bit. Its fascinating to see the effort that goes into TIG welding. With exhausts (especially turbo intakes), they fit big bungs to the pipe and purge it first with welding gas. Then using a mega sized TIG cup, weld each individual joint. The inside of the weld zone then looks like the outside.... So there is no welding slag to break away and go through the turbos.
 

schlitzaugen

1000+ Posts
TIG is amazing, but it is misleading to watch videos of people who do it for a living and make it look easy like a professional piano player. You're not going to get there until you put some serious hours into it. Watch This Old Tony, he goes from zero to well, very good in a number of videos explaining along what he spent money on and what happens. The journey is not straightforward.
 
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