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Since you mentioned welding, this is actually a covert welding related question!
I have to do some rust repairs and I'm trying to find out what steel was used in the chassis so I can get a suitable steel to make my patch panels with.
If it makes you feel better, if it's some special grade of steel, you probably won't be able to buy it since that sort of thing is something the automakers contract with from their steel supplier.
They also have production abilities to stamp the panels out with big honking presses, a consumer grade steel is.nice to work with because it generally can be formed by us peons with hand tools I wouldn't discount that quality, either, as being able to make the shapes you want is probably more important. Of course the easy method is a pieces cut from an existing car.... but they all seem to rust in the same places... hmm, small problem here!
Most of the car seems to be 22 gauge, or obvs the Metric equivalent.
That's a fair point. My hope is to get the closest equilivent steel I can, but of course to do that I need a vague idea of what steel is in the chassis already. I know I'm probably overthinking this but it's just the way I am!
I found some information on the chassis material in the following manual:
Mazda 929, 626, 323/GLC,RX-7, E-Series Bodyshop Manual - High Strength Steel and Plastic parts
It states that "high-strength steel has begun to be used for the vehicle body":
It explains which components of the chassis use high strength steel, but, only for the 323 and 626, not the Rx7:
So while this does provide some information, it doesn't confirm if the Rx7 chassis utilises high strength steel or not!
I will keep searching for more information on this and see what I can find, but if anyone has any further information to add I'd really appreciate it.
Thanks.
From experience welding on these cars, getting through the coating is key. So just using a wire wheel to clean off paint and primer doesn't leave a clean welding surface. Light used of a flap wheel helped allot. The biggest issue was that the car is made out of really thin material in places. So matching the thickness of the patch panel to the OE material was important unless I was just trying to add structure. I always used what ever my local metal store had in stock and it worked well.
I talked to guy that put roll cages in domestic unibody cars. His technique for getting a good weld on OE stamped steal was to clean it with a flap wheel and then heat the base metal with a torch before making the weld. Never tried on my RX7 but will if I ever put a cage in another unibody car.
Hi mustamghammer, good advice on the flap discs, I would have assumed that the wirebrush would have been good enough, thanks!
Do you have any experience welding structural parts of the chassis?
From the little research I have done my understanding is that heating, or preheating, high strength steel before welding is supposed to minimise the risk of the steel becoming brittle. Maybe someone can correct me if I am wrong on this.
That sounds like a strategy for dealing with chrome-moly tubing (like 4130 bike tubing).
Next time I have to weld on the Mazda I'll try that. A lot of my welding issues are because I learned from an old fart who was a master with a TIG, who would say to just burn out the impurities with welding heat, don't waste time cleaning.
Try THAT on a BMW where I swear they spot welded the panels together through seam sealer. Such mess.
Hi peejay,
So I suppose the safest thing to do is too assume all chassis parts are high strength steel and preheat before and after welding as you would with Chrome-Moly.
I recently did an online TIG course and there was a topic about welding chrome-moly tubing. I must watch that video again to refresh myself!
Your "master" wouldn't have been a fan of the course as the recurring message was material prep and cleanliness
Hi mustamghammer, good advice on the flap discs, I would have assumed that the wirebrush would have been good enough, thanks!
Do you have any experience welding structural parts of the chassis?
From the little research I have done my understanding is that heating, or preheating, high strength steel before welding is supposed to minimise the risk of the steel becoming brittle. Maybe someone can correct me if I am wrong on this.
All of the cage pads or critical structures (strut tower tops, etc) on my car are either 11 gauge or .125" mild steel. Other items range in gauge thickness from 14 to 18 gauge but I really don't like working with the thin stuff. Burn though was mitigated by using lap joints and not butt welds. Cage tubing is all DOM mild steel in either .095 or ,063 depending on location of the tube. I didn't know about heating up the chassis before welding so that was never employed for this build. All of the welding i performed used a Millermatic 185 running ,030 wire with 75% argon 25% CO2. I am now using a Lincoln 180 Weld Pak/Easy Mig with .025 wire using the same gas and it works better on thin material than the Miller did. It is a newer generation unit and I like it better overall.
Aside from prepping the car before a weld, getting the mill scale off of the metal being attached to the car really helps too, So again, take the time to use a wire wheel. a flap wheel or even a sand blaster to get the metal cleaned up,
Hi mustanghammer,
You sure do have experience welding structural parts of the chassis! That's some really impressive work!! I like the idea of the additional cage members from the firewall to the struct tower (I might be taking inspiration from that one).
I have a mig and I'm running 0.031" (0.8mm) wire for patching up a wheel arch and it's burning holes all over the place. I'm managing to work around it by using a custom copper heat sink (Basically I hammered flat a piece of copper pipe). I'll try using some 0.023" (0.6mm) wire and see how it goes!
I wouldn't discount that quality, either, as being able to make the shapes you want is probably more important. Of course the easy method is a pieces cut from an existing car.... but they all seem to rust in the same places... hmm, small problem here!
).
). I'll try using some 0.023" (0.6mm) wire and see how it goes!