56a London Trolleybus - unlisted variations

[GHOSTHUNTER]

Yes it does...are the moulds coated with a release agent first, which is intended to help the castings release, but does not always work, some castings still adhere to the mould!

Ghosty.

[Idris]

Yes it does...are the moulds coated with a release agent first, which is intended to help the castings release, but does not always work, some castings still adhere to the mould!

Are you sure about that? Surely the temperature of molten mazac/zamac (about 385 degC/720 degF according to Mr. Google) would preclude the use of any hydrocarbon-based release agent? That being so, what is the release agent used? Google points me in the direction of solids such as boron nitride aka white graphite.(Up until now, I had always assumed that the casting simply contracted away from the tooling on solidification/cooling and that this was how it was able to be released (together with a bit of help from ejectors).)

Addendum: further reading leads me to believe that the release agents used consist of high concentrations of finely-divided solids in a liquid (either water or a solvent) which flashes off during the casting process leaving the solids behind.

[GHOSTHUNTER]

Yes, essentially it is 'Oil in Water' that is used which coats the mould surfaces (inside the cavity areas more specifically), the moulten 'Mazac' evaporates the water leaving a film of oil, intended to help the release of the castings.

GHOSTHUNTER.

[mike]

Hello Antonin.
A very interesting contribution.
I checked my models 56 models
I found this difference: the black wheels are smaller
as the gray and metal wheels.

I hope it's not an optical illusion.
But I heard already of trolley bus with smaller black wheels.

Greetings Mike

[mike]

....... Interesting also the color difference in the
gray plastic wheels.

[Diecast]

Hi Mike
by your nice photos the wheels look like that they have a different diameter, it is partly due to an optical illusion and partly due to the metal and plastic wheels wheels have indeed slightly different diameters. Typically the metal wheels have approx. ø7,6mm and the plastic wheels approx. ø7,3-ø7,4mm. Interesting would be to find 56a Trolleybus with BPW ø8x18 (as Nick has predicted it by 35a and then it was confirmed).
Antonin