Whittle V8

John Roberts · Dec 22, 2018

Please find attached photo of my completed 10.6 cc v8 aero engine. About 600 parts in total. Still have not got it to run yet due to lack of compression. I suspect the valve springs to be too light. Will change these some time. If that dues not work I will remake the pistons with more metal on top to raise the compression.
Enjoyable to make but too small for me!
Started now making a 1/4 scale Rotary BR2 to the Blackmore design. Which is a better size.

kadora · Dec 23, 2018

Hello John
Beautiful engine real masterpiece .
10.6 cc/8= 1.3 cc per cylinder. My rough guess The cylinder bore is 10 -12mm ?
In such small combustion chamber are two valves and spark plug - it is clockwork .
I have similar problem . I have built 1.1 ccm single four stroke glow engine but for lack of space
in combustion chamber (bore 10.1 mm) I designed side valve train.
As you I have the same problem to start engine.
My engine has perfect compression when is cold . During starting engine /by electric starter /
engine is slightly worm and partially lose compression.
I will try to rebuild engine for spark ignition and hopefully it will run.
BTW how did you machine piston rings ?
I wish you merry Christmas.

John Roberts · Dec 23, 2018

Yes the bore is 11.7 mm dia. It has glow plugs which are machined down in size.
8 plugs takes a lot of power. My Brother made a power supply, so it delivered the correct power to the plugs. So in my case I can discount that. The rings were machined to size then cut with good side cutters. Then they were mounted on a fixture that opened them slightly then the rings were annealed which allowed them to spring down to bore size.
One needs to understand where lost compression is coming from. Valve leakage can be checked by attaching a tube and blowing whilst the head in under water.