first time welding outer rocker on unibody car. help?

[mignoob]

I am fairly new to welding and have never welded on a vehicle before but I can get by with my mig welding. I never took a class, learned how at a job I had.

I have a 1986 mazda rx7 which is a unibody car. I am having outer rocker panels made as they need to be replaced and the rear section of the inner rocker/sill is needing a small patch on both sides of the car. I am using a friends mig welder to do this myself. I have been reading on this site and have found lots of useful info so heres my plan so far:

-weld a peice of tube/pipe between the bottom of the door jam to help keep structure flex down and door gaps in check.

-drill some holes in new rocker for plug welding on the pinch weld on the bottom of the car (planning on welding that seem on the pinch weld as well after)

-doing a butt weld for the top of the outer rocker. having the rocker made so it goes up to the edge of the door. tacking it and stitch welding, leaving plenty of time to cool down and reduce distortion.

-with old rocker off, wire brushing and using some rust converter on the inside to get rid of most rust inside. then spraying weld through primer in there and on the new panel before welding.

now, I was going to cut the old rocker at the angle of the pinch weld and leave that little section on the pinch weld there so I don't have to deal with the spot welds. is that a good approach since I am seem welding and plug welding on the pinch weld anyway? I only have access to a cutting wheel to get the outer rocker off. any tips you guys can give and advice on my plan?

 

[grandads_shed]

may be wrong here but are u on about the sill of the car?? it go from front wheel to bk wheel under the doors ????

 

[mignoob]

yes, the sills. sorry, we call them rocker panels in my area.

also wondering, would the weld through primer be ok after welding? I am wondering about the backside of the sill/rocker after its welded on.

 

[shenion]

Plan sounds fine. It is probably rotted back farther than you think

Spot welds are not too bad. You can use a special drill to drill them out. I have used the "bullet' type that have flat cutting edge with a smaller pilot bit. An air hammmer will work also.

Pictures will help to better judge.

What welder do you have? Gas or gasless?

 

[Chickenjohn]

Hi Mignoob and welcome to the forum! My answers are bold!

I am fairly new to welding and have never welded on a vehicle before but I can get by with my mig welding. I never took a class, learned how at a job I had.

Good, sounds like you have the technique down already.

I have a 1986 mazda rx7 which is a unibody car. I am having outer rocker panels made as they need to be replaced and the rear section of the inner rocker/sill is needing a small patch on both sides of the car. I am using a friends mig welder to do this myself. I have been reading on this site and have found lots of useful info so heres my plan so far:

Can you not buy ready pressed outer rocker (sill in the UK) panels from a panel supplier? Will be a lot cheaper than having them made.

-weld a peice of tube/pipe between the bottom of the door jam to help keep structure flex down and door gaps in check.

Good idea to brace the door gap, but try and weld it in such a place that you can still close the door to check the door gap if you can! (after tacking the sill in place). Things can still move on a car after welding.

-drill some holes in new rocker for plug welding on the pinch weld on the bottom of the car (planning on welding that seem on the pinch weld as well after)

^^^^I would do this! ^^^^^ but no need to weld the very bottom lip of the seam if the new section is plug welded to the bottom. just paint and seam seal the lip (making sure you leave provision for drainage!)

-doing a butt weld for the top of the outer rocker. having the rocker made so it goes up to the edge of the door. tacking it and stitch welding, leaving plenty of time to cool down and reduce distortion.

If you are using weld thru primer, another idea is to joddle the remains of the top of the sill and plug weld the new sill to that. This will minimise the danger of distortion.

-with old rocker off, wire brushing and using some rust converter on the inside to get rid of most rust inside. then spraying weld through primer in there and on the new panel before welding.

Use a wire cup brush on a grinder- this will remove any unsound metal/ rust, another idea is to use a spot blaster if you have access to a compressor to de-rust any awkward corners etc.

now, I was going to cut the old rocker at the angle of the pinch weld and leave that little section on the pinch weld there so I don't have to deal with the spot welds. is that a good approach since I am seem welding and plug welding on the pinch weld anyway? I only have access to a cutting wheel to get the outer rocker off. any tips you guys can give and advice on my plan?

I agree with the above poster who suggested drilling out all the spot welds at the bottom of the sill (rocker panel) using a spot weld drill- much neater and you will have got rid of all the rust in the bottom of the outer sill - sills tend to rust more at the bottom due to collection of water before it drains out.

Another point or two- be prepared for more rust damage to be revealed inside the inner sill/rocker and central membrane (if the structure has one). best to cut it all out while you are in there.

Before welding in the new sill/ rocker consider painting inside the de-rusted sill and new panel some paint (such as chassis black) on top of the zinc primer.

I hope whoever made the new sill left some indentations at the bottom for drainage, if not consider adding some.

After the outer sill is painted, inject cavity wax inside the freshly repaired sills, you want to protect all your hard work!

Good luck with your project and please post some pictures as work progresses.

 

[pedrobedro]

Cut off everything you can that is going to be replaced. I use a larger drill to weaken the top layer of the spot welds then break the metal between two welds and grip the end with long nose vice grip and turn it back like a sardine tin lid. Grind any bumps off after to get the new panel as flush as you can.

 

[mignoob]

a lot to respond to! thanks guys.

on the passenger side I can see right up into the inner rocker/sill to see and I have already sprayed some rust bullet and regular body primer from rattle cans up in there. the passenger is almost all gone on the bottom side but the inner rocker is still plenty strong as well as the floor pan area and frame pieces that go to the inner rocker sill. the drivers side might be as bad but is more closed off. I don't think its too far gone though, we'll see.

I am not really familiar with a lot of welding or cutting terms. what does "joddle" mean?lol.

the rockers are being made at a local metal fab shop here as I have found none available for a decent price. its not really old or sought after enough to have parts like old '57 chevys have I guess. brought the car in today, $30-40 usd a side. reasonable if you ask me.

can anyone explain how the cavity wax works and specific name for the stuff or brand? do I put it on before I weld to the car or after? I have some holes in my door jam area with rubber plugs that look like they go right down to the rocker area so I can have some access with a hose through there.

I mostly have access to regular hand tools. I don't know if I have access to any high end air tools as this is not a pro garage, just someone who fixes up auction cars to sell here and there. I'll figure out if I can get the spot welds off though with regular drills. I'm kinda on a budget. also, don't know what welder the guy has yet but I think it is gasless if I recall. I have to go check it out soon when the rockers are done so will update as I find out more. should be within the week will get this done. It's my girlfriends dad's welder but he also has a torch or arc welder that uses gas so I am wondering if the mig is gas or not. her step brother is borrowing it and is who I will be going to to do this as her dad is overseas right now for national guard.

and won't paint run off during welding if I through some chassis black paint on there? I have some more questions but will let these be answered/discussed first. really apreciate the help as I can't afford for a shop to do it. thinking of getting into bodywork for a career,taking classes and what not.

 

[shenion]

I think you mean joggle. That is putting a Z-bend in the edge so the edge is stepped back the thickness of the metal. That way the next piece can lay flat on top of it and be flush with the rest of the sheet.

Don't know the cavity wax here in the US. I'd find an auto paint supplier and ask. I found places like auto parts stores had some crap auto body stuff.

An arc welder would be too hot (minimum metal is about 1/16".) Gasless MIG is about the same. A gas torch can be used but not real easy to do. See if it can be used with gas. It can be done with gasless using the thin metal technique but is messy and you will fight blowing holes.

 

[mignoob]

ya, I am versed in gas mig so if it is gasless I might try and see if I can find a gas mig from one of my friends. a buddy rents half a shop for his graphics business but the guy he shares the shop with might have a gas mig I can borrow there maybe. I figured that arc would be too hot too. I think I can rent a gas mig around here too so thats an option. I need to buy my own soon here.

heres a pic of the car. pics of the rocker will be up as soon as I get the car jacked up.

 

[shenion]

I bought a Clarke to start with and I found it one of the best investments ever. I used it far more than I thought I would. Too bar Clarke's are now harder to get.

Bodywork takes along time, having your own MIG will be easier as you don't need to keep borrowing one.

 

[mignoob]

update: I talked to the person about the welder and it is gas but only 110, the rockers/sills are going to be 22 gauge. Do I have a problem or can I use the 110 and go a little slower with the power cranked up to get the penetration I need? I thought I needed a little more power for this job but really am not sure. thanks.

 

[Country Joe]

Hi there,
You'll probably find you need about as little power as you can. (ususally around the lowest setting, say 25/30 amps?)
Bodywork is thin, so blowing holes will be more of a problem than not enough power.
All the Best,
CJ

 

[shenion]

You will be fine on 110.

The welder is probably 130 amps or so. That is max you can get on 110 on a 20A circuit.

Most bodywork is 30 amps or so, so should be no problem.

If you use and extension cord, use a short and heavy one, the welder will be more consistent.

 

[mignoob]

thanks for the tips on the welder. the guys that made the rockers gave my some scrap to practice on and fill in a couple other small trouble spots and to set the welder up with so I will get it dialed in right and work on technique before I start. all of you are definitely making me feel more prepared for this job.

how would I apply seam sealer to the inside part of the weld area when it will be inaccessible? I don't want this to start rusting from the inside after so checking up on that. I am going to put the weld through primer on and paint over that as someone said so would I need the seem sealer on the inside too?

 

[boatbuilder]

Its usually not possible to get seam sealer inside a sill section as far as I know.
Weld through primer is really only for inaccessible areas and areas where ordinary paint would be burnt off by the welding heat.
On mine, I give a good coating of weld through primer before welding, then spray in some waxoyl or similar afterwards.

 

[mignoob]

ok, I will have to look for some waxoyl then. thank you for the info. someone earlier told me I should use seam sealer but I have no way to get it on the inside so I guess he meant to put it on the outside.

 

[mignoob]

UPDATE: need some help here. I got in way over my head and now things aren't looking so good. I ended up cutting out a bunch of small sections under the car in front of the rocker section I had made as they were rusty, small holes, and weak areas. I have begun welding in new sections but I find myself basically tack welding the entire seam as I blow holes otherwise. (I have the welder on lowest power and the wire feed as low as I can with continuous contact, have tried lower feed but even worse). Now, I am getting good penetration and strong welds but I am developing a few small pinholes here and there and I am sick of going through grinding disks and re welding 4-5 times to eliminate any spot were water or moisture can get into.

Can I use seam sealer to put over my welds to take care of those pinholes? Or perhaps some J.B. weld or other liquid steel? I'm looking for a short cut that I can just smear on and fill/cover pinholes and most of the welds are not completely ground down due to where they are located.

The passenger side was much worse then I thought it would be but most of the problems are with thin metal sections and aren't very large so the chassis is still strong. I'd just rather fix these spots and make it stronger. I've been working 5 8 hour days total now and am still just finishing up the front corner area, I still need to put the new rocker on (the easiest part I think) and then tackle the back corner watch has a lot gone but is a boxeir section so easier to fix. I'm working by myself making templates, cutting new panels, painting with weld through primer, welding them in, etc which is why its taking so long I think. my brother is helping this weekend so I hope I can finish this side at least. the car needs to be out of this borrowed work space by december 1st!

 

[mignoob]

anyone? there a just a pinhole here and there. I would think seam sealer would work fine as the section is under neath the front fender and I don't know how well J.B. weld or liquid steel would work.

 

[Chickenjohn]

If it is literally just a pinhole here and there, just mig it up in those spots and grind it down. Then prime with zinc primer and then apply the seam sealer.

Don't rely on seam sealer on its own, make sure you have welded up all holes.

 

[mignoob]

(sigh) ya, I was just looking for a shortcut. grinding discs are expensive and I find myself building up the welds a little so there is a bit to grind off after. I'm guessing the metal on the car is either weak from age or is actually thinner metal then what I'm using because its the metal on the car thats blowing through, the new metal is fine (24 gauge). the only way I know there is a pinhole is I shine the light on the back and see if there are any spots showing through. I wish I could just stitch weld beads, would be so much easier.