Scratch-Building Motors --- 2 Jaguar Radials to start off

[Old Man]

I am starting on some scratch-build projects in 1/72 scale. All of them feature un-cowled motors. So I am treating the motors as a sort of stand-alone sub-project, and mean to get them done and out of the way first.

 

I am starting off with preparing two Armstrong-Siddeley Jaguar radials. I have done radials in the past, but it has been a while, and only one had seven cylinders. I have never done a full twin-row radial. Nine cylinder radials are a bit easier on the eyes than seven cylinder ones, it is easier to comprehend the alignments of nine cylinders than of seven. After some false starts, this is what I have finally set to....

 

 

This is greatly enlarged, obviously. The 'crankcase' is made from two circles of 2mm sheet, and measures a hair over 6mm in diameter. Sections of 2.4mm tube have been applied to represent the rings into which the cylinders were screwed down, and will serve as the seat for the cylinders themselves. Because of the over-lap in the rings, the alignment of just one run of rings on each crankcase effectively dictates the placement of the second run of rings, and ensures it will be in pretty good relation to the first. To get the initial alignments, I prepared a pattern with a protractor and straight edge (51.4 degrees between each cylinder is the goal), and made a simple template in plastic from this, with which to mark where the cylinders should go.

 

 

Here are the crankcases with the 'rings' sanded down, ready to receive the cylinders. I smudged them up with a pencil to make things a little clearer.

 

 

Here is the early going on assembling cylinders to the crankcases. This one has seven of its fourteen attached. The cylinders are cut from tube approximately 2.75mm in diameter. The 2.4mm was too thin, the 3.1mm was too thick, so I took a good length of the 3.1mm and sanded it down till it looked about midway between the two stock sizes.

 

Each cylinder was made as follows. At the current end of the tube, a line 1/16" was marked back from the end. Taper was sanded in to this line. A line was marked a bit over 1/8" back from the end. Everything was scored around the tube with a needle in a pin-vise (to represent finning), and then the cylinder piece cut from the tube with an Exacto knife, on or about the 1/8" line. This was repeated for each cylinder as the business proceeded.

 

 

Here are the two motors with all cylinders attached. The one on the left has been sanded down to final measurement, the one on the right is 'raw', just as the cylinders came from the knife.

 

 

This is the 'raw' piece above, with just a little sanding, fitting roughly into a circle template. The actual diameter of the hole is about 1/64 or so greater than the stated diameter; these are designed as drawing aids, and make some allowance for the thickness of the pencil or pen drawing the circle.

 

 

Here is the finished piece above, fitting tightly into a circle almost a sixteenth of an inch smaller than when it began. This circle accords well with the diameter of the motor (excluding valves and lifters) in a Grainger drawing I am using as a guide.

 

Once both motors fit tightly into the 9/16ths hole, I put some shape to the cylinder heads.

 

 

There is some fine-tuning to be done, but not much of it. In the course of finishing these, I had to shift the position of a cylinder or two on each, and had to replace one cylinder that I damaged in shaping the head.

 

Next step on these will be adding the crankcase fronts, after which valves, etc., can be put on....

Edited April 8, 2017 by Old Man

[Brandy]

Very nice work! What will they go on?

 

Ian

[Old Man]

24 minutes ago, limeypilot said:

Very nice work! What will they go on?

 

Ian

 

Thanks.

 

They will be going on a pair of Flycatchers, one on floats and one on wheels.

[Ozzyman69]

At one day I decided do the same by resin (2xBristol Pegasus for PZL.37). Normally it has turned out as I remember. Your idea very interesting and good result also!

[Beard]

That's impressive work there and a useful 'how to'.

[pheonix]

Great to see you back and scratch-building again OM. Also a most interesting and informative tutorial on the engines - and to the very high standards that we expect from you.

 

P