Hello Forum,
Does anyone know of a safe way to repair the cab/hood on a postwar 736? I have a 736 that has hood/cab damage. The damage is not on the corners as could be expected, but in the middle. There is a flat spot,and I was hoping to have it “rounded” again. Is there anyone that does repairs of that nature that could be recommended or can this be safely be repaired? Thanks for any and all help.
Bernie
**Bernie…**guys are not avoiding you. The answer is heat, and that is where it gets tricky. This is a tough one because the metal snaps easily. You may want to read http://cs.trains.com/trccs/forums/p/131772/1481055.aspx#1481055.
There are a lot of us with a bent cab corner that decided to turn a blind eye to it. Somewhere in the archives I read where someone cut the entire overhang off the shell and replaced it with a straight one off a scavenged shell. If I recall correctly, they used glue and hidden bracing on the unseen underside of the cab roof. My 2046 has carried a bent cab corner for about 53 years due to the indiscretions and carelessness of a 5 year old, excessive throttle, and the unforgiving nature of a concrete floor. [swg].
Jack
Bernie, the information Jack references is very good. As Dennis H. posted, you need the heat. The way the original repair article read, you get a undamaged copy of that engine. Cut and shape a piece of hardwood to the inside arc of the roof of the cab. Then fasten the wood in a vise. With the damaged cab now placed with the hardwood top on the inside of the cab, heat the metal around the cab roof. Then, with a hammer, reshape the damaged cab to the form of the wood.
That is how they did it, but they also cautioned you that you should be familiar with using a torch as well as suggesting that you try on a locomotive that you dont care about first to get the hang of it. Also, the cab that was used in the article had the corners bent. For your situation, you may want to heat the whole top of the cab roof to prevent cracking when the center is straightened. Also, you will have to paint it when done.
Good luck. If you are going to tackle this, please take and post photos as this topic does come up from time to time. The information above is all from what others have said. While I have worked with torches and forming metals, I have not done repairs to cab roofs.
Dennis
It’s very difficult to make a recommendation without being able to see the damage. As has been noted, the usual damage involves the corners, and repairs can be tricky whether heat is involved or not. At first blush, your repair sounds a bit easier.
Unless the cab on your 736 is crushed to the point where the windows and sidewalls are deformed, I’d suggest using an auto-body filler.*
In any event, it is important that when cured the filler-patch is slightly softer than the die-cast metal itself, or shaping and feathering it will be virtually impossible.
You’re going to have to repaint anyway so make sure you remove all the old paint to ensure good adhesion by the filler.
You can attempt to make some kind of a shaped-form as mentioned above, but I think I would just “eye-ball it.” The repair might have to be done in stages.
Of course this method will do nothing for the underside** of the roof, but that may be of little consequence to you. Sometimes perfection can be the enemy of the good.
*Something like “Bondo” perhaps? Or maybe one of the putty-products from the Micro-Mark catalog, available online.
** If the underside is really bad, you might have to grind it off a bit and repaint.
For the filler method, sanding the paint off with 80 or 100 grit sandpaper down to clean metal will let the filler (Bondo should work) get a good grip. Keep your layers of filler to 1/8" thick or so. The sand with a sanding block, fill divots, sand, fill etc. until you are happy with the contour.
You might try something like Squadron Green putty for the final coat, as it is designed for use on models. The filler is ground finer than the auto body products and it will feather better.
Prime, sand (400 grit), fill divots again (Squardon Green), prime, sand, color coat.
Good luck.
You can have some fun with this. Get some old shells and practice. Place the dent in them first. If it is a small dent a little heat should work. A large one will need a relief cut to the edge using a cutting wheel. Cutting the divit releaves the stress and you can work on shaping. Without it, you could break the cab off Then you just backfill. I wonder if you could get solder to stick to the cast? With a little work you could cast the roof section and replace it. After reading this you may want to get another one first.[:)]
I have had good luck repairing bent cabs using heat. I would make one suggestion to those responders who suggest using a hardwood die on the underside of the cab. I make a hardwood die for both sides of the cab. Use a rectangular piece of oak hardwood and cut it thru with a band saw with the proper are of the roof you are trying to fix. When finished it will look like a square block with smile in it. I always heated the roof with propane torch and then apply the two hard wood pieces and put a clamp on the two pieces and attempt to close it. If it closes, fine, it not you need a little more heat. Careful trial and error here. Don’t heat more that necessary. I have used this method many times on bent corners and have had excellent results. I have never broken a corner. Mark the die for the loco type and you can reuse someday. Good luck.