A few weeks ago, I was approached by the guy who runs out local club second hand stall to advise him on a couple of kits he'd had passed over for sale.
One was a bit of a surprise - an original P Class tank engine. Just like the one I completed recently.
I think this is an original Wills production from the 1960's. While the body appears to be the same, underneath the modeller is expected to use a cast whitemetal chassis.
The theory is that it's a good idea to supply the scary bit of construction as a ready to use part. The fact that it looks a lot like the solid chassis found under contemporary RTR engines is a bonus in the "not scaring the modeller" stakes too.
On the face of it, this is good. Look, the axles holes are even ready-bushed with brass bearings. How fab is that?
Fabness depends on the lump of metal. Whitemetal shrinks as it cools and although an expert toolmaker can work out how much shrinkage will occur, (using a Shrink Rule) it's not easy. Nor is it an exact science as different thicknesses will change different amounts. To make things worse, even if you unpack a perfect chassis from the box of bits, being a soft metal, twisting during construction, through something as simple as over-tightening the body retaining screws, will turn a sweet runner into a bag of nails pretty much instantly.
All this explains why we now tend to find etched chassis. While they require construction and effort, the chances are the results will work properly.
The kit? Well, I understand it will be on the L&WMRS second hand stall for about £35, with room for negotiation.