Posted: Wed Apr 20, 2016 3:25 pm Post subject: Tuck Shrinking Flange for Vitara Panel
Alright folks. I chopped a bit off my Vitara. I'll post more info on that at another time (also I'm waiting to see how well the overall job goes). I spent a good two days doing the first side of these panels. Fairly happy with the result considering this is my first go at anything like this. (note I did get it wrong 1 and a half times).
So if you move the rear bit of a hard top vitara cab towards closer to the front you end up with this kind of shape.... (unless you buy a soft top and remove the soft bit to make your pickup vitara ... which will save you a lot of time - probably thing to remember here is I'm doing it because it seemed like a fun thing to do at the time)
I didn't want to leave it like that. Idea was to bring it forwards to the back edge of the door and be as flush as I could get with it. Tricky bit is this bit of a vitara curves into towards center of vehicle as it goes up (a lot of vehicles do tbh). Really you need a flange to get the spacing out to where the door sits at the door end (right) and other end have it butting up to flush or overlapping the rear pillar (left). If overlapping I think you'd want to go right to the back of the pillar (far left). In hindsite that would have been easier. Especially as I got over enthusiastic and put the inner panel inside the cab first. This could have made it very tricky to get the panel to stay in the right place when tacking it on (it wasn't that bad). Anyway back to a flange bent into a sheet... makes it pretty hard to pend the sheet.
I considered a few options on how to do it, but my dad told me to google tuck shrinking / flange shrinking. I'll let you google it if you don't already know what it is. Anyway I thought I'd have a go...
This is my practice piece...
...as it seemed to give the me the profile I wanted pretty much straight away I decided this was the route forwards. I did manage to get the tucks a bit flatter on this piece. I used a chisel to put the tucks into the flange, and a pretty big hammer, while holding the piece over a vise on my bench with the jaws open wide enough to knock the tuck down. You can pretty much see the frequency at which I made the tucks. I bashed the tucks back out with same big hammer and a steel block (block made it easier for me to direct the hit pattern). I didn't use heat. The sheet is 1.2mm thick. This approach was pretty crude and was really hard work. I'm a complete amateur at this but I think you want to be using thinner material really as I really had to beat the tucks back down. If you see youtube videos of folks doing this they don't exactly strike the steel hard to get it to start moving. When knocking the tuck back I used
Seems some people put a flappy wheel over it to clean it up after... as this was the practice piece I did to see what I could get away with...
Convinced this was the right approach I cracked on with the real panel...
Bent in the flange...
My sheet bending equipment is crude and it's success depends mostly on how much I think about where I put the various bits of box/angle and clamps.
This time I overdid it as I'd got a feel for how much it would spring back when knocking the tucks out (I think this is a sign that I'm not really doing it right tbh - but I was managing to get enough profile for what I wanted)...
New piece next to the practice piece...
Anyone else running a calmini work bench?
SO THIS WENT WRONG
I could not for the life of me get it to stay curved when hitting out the tucks. It kept returning to a flat piece. I tried a lot of things. You might have spotted I put the tucks in a different direction initially. This was mostly because it was a lot easier to do it this way. I tried adding more tucks but didn't get it to shrink the flange.
Because I was 1 good, 1 bad at this point I figured I still had a decent change of making this work so I cut the flange off of the piece that was meant to be a real panel to use it as a second practice piece. I bent a flange into it again (making it too short for the end product) and had another go....
Dammit - so apparently I can only make practice pieces work?! No I was even more convinced that I could get this to work, I'm now on 2 good, 1 bad. My odds were improving?
The latest attempt is the most rear in this picture. Note the front is the flange I cut off that went badly wrong. It actually sprang back the opposite direction when I cut it away from the sheet. Suggests I was actually growing the flange rather than shrinking it. Bearing this in mind I decided to be more careful about how much work I put into getting the tucks flat (if you keep hitting them once they are flat on whatever you are hitting them on I think you are starting to spread the metal which is pretty much the opposite of what you want to do. Does make undoing an over-bend a lot easier that adding more though.
By now I'd spent two days at it! I think the reason for the botched attempt was due to a not so sharp bend on the flange - it's the only real variable that I can think of which changed but did didn't test out to see if it was having an effect (other than I made sure the final two pieces had a really sharp bend on them). I did switch to using a cross-pein hammer to put the tucks in but really that was easier. I don't think it fixed it. On the final panel I was even fairly aggressive about hitting the tucks. Only other thing I was thinking it could be was I did a fair bit of leaning on the panel to encourage it to stay curved - but I didn't do that on the original piece.
I did the other side in one evening. Pictures are better on this side...
I'm pretty happy with my result and now have a really healthy respect for anyone that can do this sort of thing properly. ( I already did to be honest, just now more so! )
Baileigh is the answer - you should be putting the flange on to the bend rather than tucking - you will get a wavey flange but nowhere near as bad as a tucked flange
Xpajun, I think I understand what you are saying. I should have bent the sheet to the profile I wanted, and then beat the flange over? I'm not sure if I would have managed that. Maybe on something thinner.
If not, not sure I understand still. The chap there is working on a cylinder so I guess the material in the flange is forced to stretch as it turns out - that or the drum moved out of shape. With what i did it's relying on the flange shrinkage to form the curved profile of the panel. To me that seems the opposite. I presume if he did an inside flange on that cylinder the drum would be caused the material in the flange to shrink - but still the profile of the "sheet" is already define before turning the flange - is that what you mean?
My backup plan was to slit the flange at regular intervals to allow the panel to curve - I don't know how that would have gone but I'd imagine would be a lot easier and less prone to going wrong. few mins with angle grinder and then a few more with the welder. I'm glad I had a go at this approach though.
My understanding of tucking shrinking done properly is that particles in the metal are actually moved around rearranging themselves (should be able to feel heat in it).
Got more pics of the overall job already - but I'm trying to finish it first before posting stuff. I've got a 128x speed video of me somewhere cutting the roof off!
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- you should be putting the flange on to the bend rather than tucking - you will get a wavey flange but nowhere near as bad as a tucked flange
