I am getting back to some repainting, kitbashing and detailing projects on N scale freight cars. I have some USRA designed underframe replacements made years ago by ACCUMATE N SCALE in resin, primarily for Arnold Rapido freight cars. Those Rapido cars are hard to convert to MicroTrains trucks and the replacement USRA allows a drop-in conversion. I wanted to use them to detail some Concor steel reefers as USRA rebuilds, which were a majority of the Santa Fe transition era reefer fleet. Problem is the replacement underframes are WARPED. [:(] They are bowed up at the center, the way prototype truss-rod cars sometimes got when too much tension was applied to the truss rods.
I have a similar problem with some Fine N Scale Santa Fe Caswell drop-bottom gondolas, except these sag in the middle as if they had been overloaded.
Has anyone had any successful experience with straightening resin castings like these. I have heard of straightening out “plastic” (styrene?) cars and parts that had warped due to heat, etc. But resin? I can think of putting the parts in boiling or near boiling water. Would I need to put them under some of pressure, like heavy weight to force them back into shape while soft. IF they get soft. Do resin casting get soft when heated? Anybody know?
Enquiring minds want to know.
Chicken carbashers want to know before experimenting on no-longer-available parts and kits.
Many years ago I had a resin structure kit the walls of which had warped in the box. I placed them detail side up on waxed paper on a cookie sheetand put them in the oven at about 250 for fifteen minutes or so.
Also have placed resin kits in the oven. One thing. Like said above it will surely work nice. But you have to watch them very close. Once they get to the bend point take them out and place them onto a flat surface to cool. If you let them get PAST the melting point what happens is that they will bend into a shape and harden, then forget it.They will be like iron then. It’s almost like steel. If you temper it it will become harder then it was to start with. But it takes a lot to melt resin.
I see potential for disaster here. I wouldn’t dare to do this without testing some sacrificial material first. First of all, do we have a flat surface to place in the oven that won’t warp when heated? How much heat and time in the oven will the material withstand? …
Mark (one who has warped beyond repair a plastic structure at low heat in an oven to speed up paint drying)
It’s simple. You DO NOT need a flat surface to place the resin kit on. Just one to place it on when you remove it. And that’s not a given. Turn the oven to 350. Place the resin kit directly on the rack. Keep opening the oven to test the piece. You can remove it and actually bend it when it is ready to remove. Just keep watching it. Don’t place it in the oven and go wash the car. Anyone with some common sence will be able to do this right.
You don’t have to heat resin to 350’! and shouldn’t. 200-250 is plenty. The trick is to remove the part and get it weighted down quickly.
An alternative is to put the part on a piece of glass (or anything flat that won’t be affected by heat) and weight it down, (it doesn’t have to be a lot of weight and it doesn’t have to flatten the piece while it’s still cold), put it in the oven, turn the heat on to 200’ and leave it there for about 30 minutes, turn the heat off and let cool completely before removing the weight. I do this from time to time with great success in my paint drying oven (go to my pics in my sig below), which only reaches 185’.
I just put the warped part in a pot with boiling water, take it out after a few minutes, put it on a flat surface cover it with a sheet of paper and weigh it down with a book etc. After the part has cooled down, it is straight.
Thanks for the many suggestions. I have an old electric toaster oven out in the garage gathering dust. Too yucky to use in ther kitchen, has been replaced. But too good to throw away. I will experiment and report back how it works. Thanks again.
Before I used a toaster oven or even a regular oven, I think I’d be inclined to get one of those hanging oven thermometers and see exactly what the oven temperature was for various dial settings of the appliance before I put any parts in. Unless your oven has some sort of digital temperature readout, I’d question the accuracy of the temperature setting dial.
I tried the boiling water and it seems to have worked well, both for my USRA underframe part and my Caswell gondolas. I will wait a couple mof days and see if the straightened castings STAY straightened.
I had good luck using a hairdryer to straighten out the warped sides of a Westerfield kit a while back. But since boiling water seems to have worked for you, I’d say it’s all good. [:)]