Cad models

Pattern design

The pattern

Barrel Pattern

Rough castings

Rough Machining

Awaiting Milling

CNC Machining

The machine

Almost done

Last set-up

Looking up your skirt

JE pistons

Bellissimo!

It all starts by 3D modeling the components. It's much easier to fix a computer model than modify a casting or pattern. 3D models are also good for other interesting information like "volume", "mass" and even "centre of gravity".

The model has to be broken down into pieces so as that it can be successfully made into a functional pattern.

In the end you need to have a sand mould which is made from "sand bricks". Just like a big jigsaw puzzel.

This is a pattern for one segment of a barrel. There are 4 different segments to each barrel, 8 segments altogether. The foundry guys are good at jigsaws.

Here we have the rough castings after heat treatment. Next is the machining and then nickasil plating. Nikasil is a very expensive process but well worth it. The nominated piston size for the first 3 motors is 92mm, being restricted by the crank cases, could probably have gone to 94mm.

Here the top faces are finished leaving stock in the bores. Porosity is not a good thing to find in the castings, so far so good. If there is any in the bores after finishing it will have to have an alloy sleeve. The alloy is heat treated to T7 and machines beautifully, no need for coolant.

The next step will be in the CNC maching to put in the stud holes and oil galleries. One set of these barrels will have a 94mm bore with a wider stud pattern and hopefully some special heads.

The barrels are set up on a "tombstone" in the NC. This is a horizontal machine which is quite good for small work as the swarf tends to just drop out. It's an old, slow machine but still very accurate.

The programs run from a PC intergrated into the machine control. In it's day this machine ran programs that were hand typed onto paper tape probably only a few hundred lines long. Now it can run consecutive programs all day long.

Next setup is the oil return holes as they're on an angle.

This is the last set-up, machining the bore to final size before plating and also the skirt and barrel height. I made this fixture to hold the barrel without distrtion at all from the chuck jaws.

The maximum size you can bore a set of bevel twin cases is about 98mm before you hit the engine clamping bolts. That leaves a skirt wall section of 3mm which doesn't sould like much but really all it does is guide the piston skirt.

Some of the barrels will have these JE HC pistons fitted, the 94mm ones will be Pistals.

Machining is finished for this pair of barrels, next is the Nikasil plating.