Torsion bend, what to do?

[BarleyBop]

Hi, while building a BEEP WC51 (weapons carrier) from Skybow, I ran into an issue isn't repeated when I get around to the M6 GMC WC-55 (gun motor carriage) from Italeri.
Basically, despite my best efforts, the frame twisted longitudinally after a few weeks sitting on the bench.
I tried weighted clamps to twist it in the other direction, which did help somewhat, then 'adjusted' wheel placement so they'd all sit on the ground.
I still had minor alignment issues building up from the frame, which I'm certain keen eyed veteran builders will spot.
How can I avoid or correct this issue in the future?
I await your pronouncements, oh wise ones!

 

[urumomo]

heat the frame to true it .
I guess that's what you're asking .
resin or polystyrene ?

 

[BarleyBop]

Poly, I did try immersing in hot water, probably not long enough. Scaredycat should be my handle!

 

[BarleyBop]

And how to avoid the issue while I build?

 

[urumomo]

need boiling water to get it close to it's transition temp .
usually around 180-195 F is enough but the glass trabsition temp of polystyrene is 212 / 100C

avoid what issue while you build ?
The plastic will remain where you put it when it cools .

 

[BarleyBop]

Nice. Need to get out the kitchen thermometer.

With these ladder frames, how do you keep it true during assembly, especially as you typically start at one end...

 

[urumomo]

" how do you keep it true during assembly "

I don't understand , can you post a photo of this issue ?

 

[BarleyBop]

Sadly, didn't capture pic at the time...
Imagine you are building a ladder, the two rails lying side by side.
You start at one end adding the rungs, then when you get to the last one you realize that the rails are no longer parallel, and that you've somehow introduced a helical twist!

 

[urumomo]

You need to conjur up a jig of some kind to keep the longitudinal elements in plane and square corner to corner .
like a block of wood ?
without seeing the geometry of the frame I have no idea , but something simple .
or just keep checking it stays square during assembly

 

[urumomo]

If you dip that thing into boiling water just keep in mind it won't take long to heat that thin plastic up .
15 seconds ?
16 ?

 

[BarleyBop]

kk thanks for the pointers!