I’ve finally got there. One post more than I thought I’d need, but the two engines are finally complete and a selection of photographs of them added to the galleries under the drop down menus at the top of the page.
There wasn’t much left to finish them really. The main activity required was the completion of the coolant hoses, and the installation of the exhaust studs.
As before the hoses were made up of three parts.
- A wire core to make sure they keep the right shape during heating.
- A polystyrene inner tube to give them the right diameter.
- An outer sheath of black heat shrink tubing to give a true rubber appearance and thin wall thickness at the ends.
Each hose was run to the model then measured up. A final version was then made from fresh materials, as I’ve found it is necessary to partially shrink the outer onto the assembly then bend it to shape. Once that’s complete you can remove any wrinkles in the outer by completing the shrinking operation. If you try to slide the heat shrink over a bent inner, like the one in the picture below, the inner wall of the curve wrinkles to an extent that can’t be remove entirely during the heat shrinking process.
The process is a bit laborious to be honest and caused me quite a bit of grief. In hindsight it would’ve been a much simpler option if I’d done it in conjunction with fitting the exhausts rather than after. As it was some choice epithets might have been uttered during the operation.
The hoses on the burgundy engine were by far the worst to do as the arrangement is more complex than on the black one because of the location of the water pump.
Other minor work included fitting the cylinder priming pipework on the top of the burgundy engine. For some reason this was quite difficult, which was a surprise as it was relatively straightforward on the black one and they are supposedly identical. Probably just an off day at the modelling desk.
The coolant hoses also required the making of several batches of faux jubilee clips. These are fairly simple but take time. An appropriately sized tube is cut into thin sections and some thin (0.8mm OD) tube soldered to the rim. The whole assemble is bright nickel plated. As a final flourish a brass pin which has had its head slotted and then been bright nickel plated is glued into the cross tube to look like the screw mechanism.
The very last operation was to add the exhaust mounting studs. These are just glued on and have no physical function. They were made from Some M1 threaded rod with M1.0 brass nuts glued in place. The whole affair was then burnished to make them dark. Tedious and unexciting work. 32 required per engine.
If I were make another of these models I’d approach the exhausts in quite a different way I think. I’d keep the flanges separate from the exhausts themselves, which I have seen on some engines. That would make getting everything aligned much, much easier and would allow the studs to be actually glued into the block.
That’s it for these engines then. A lot of fun to make, but much more involved than I thought it would be. I’d secretly envisaged it taking about half the time it has. I wasted a lot of time and effort though trying to master white metal casting of the aluminium parts before admitting defeat and using the cold casting technique. Now that I know what I’m doing and have all of the moulds to hand I think I could build another engine in 250 – 300 hours. I might even do that as I’d like to have an unmodified aviation version too. They’re not cheap though when you add up the costs of all the nuts and bolts.
Here are some pictures of the finished models. There are a few more in the gallery pages too.
There is a CAD version of the aviation engine ready to go. I just need to get the exhausts printed off…