Straightening Bent Die Cast Metal

I certainly would be interested.

Time and patience.  I once had a 66 Ford Mustang. I purchased an export brace for it, but it wouldn't fit.  When I contacted the seller,, he assured me the brace was drilled correctly.  So, I jacked up the car, near the front seats, and let the car hang there for about six months.  When tried the brace the next time, it fit like a glove.  The frame, such as it was, had stretched back into it's original position and everything fit fine.  Time and patience.  Go slow and easy when attempting to straighten cast anything.

I fixed a bent cab roof like that shown this way, much as outlined.

a) Took a large pair of vice-grips.  Made small wood "cushions" for is jaws and clamped it on the very edge of the bent portion. 

b) set it upside down on a shelf so the vice-grip was hanging off providing leverage.

c) watching and measured each week

It took about six or more weeks.  It was not linear.  It hardly moved the first week or so and then steadily flowed with the vice-grip dropping a bit each week. But eventually it got straight.  What was left was not perfect: I had to sand and fill and then repaint (I stripped the entire loco and primed, etc.  But it came out looking perfect.

The key is slow.  Heat will accelerate the process, but not so fast that you can just bend it back into shape.  I tried this and I'd bring the heat gun around and warm it up a couple times a day.  I pretty bad bend was back in shape in about a week.  Like Lee says, you can get it close, but seldom perfect.

Yep. Patience in a virtue.

Even though it will almost never be perfect, files and filler (and paint) can correct visual problems. We're not talking collector-value, here. Just a presentable and usable machine.

Any day that you do not have to completely scratch build/rebuild a part is a good day. 

When successful, I've used a heat gun and formed the cab roof around the end of a baseball bat (old wood Duke Snider model ).

But it is not always successful. I think the big factor is whether there was any fracturing of the diecast in the original accident.

Sometimes it is just bent and can be re-formed. Other times, I think the metal has invisible cracks in the structure of the diecasting. Then, it will break no matter how much heat or how careful you are.

Jim

It depends how far it is bent. Slight bends, like 1/8 - 3/16" can be heated and straightened in a few minutes. I take a block of hardwood and cut a curve slightly straighter then what you want to end up with as it will spring back slightly when the pressure is released. Heat some, then clamp lightly, heat again, clamp harder. Do this a half dozen times until finished.

The one Spence pictured would take more time.

Pete

Interesting.  Next time I shall try that.

Note that the impact deforming your cab roof was more or less instantaneous, and no cracks.  In the 1970s I was restoring airplanes in a shop that made syrup dispenser handles.  The chief engineer was a live steamer, but that is another story.

They had discovered that the only way to bend the die cast handles to that graceful arc was all at once - wham!  Otherwise, they simply cracked.  You can still see these handles at older restaurants - they say "Dripcut" on them.  They are chrome plated die cast, made in the USA. Your thumb slides a little stainless tab out of the way to pour the syrup.

My scale Lionel B6 had a bent cab when I got it.  It now has a fiberglas extension.