Cylinder Heads – 12/08/14
Building the Prototype AMD Series Engines
Cylinder Heads
The blanks for the cylinder heads were all cut from the bar stock and machined square and to size some time ago. The cylinder heads are the most complex components and the most difficult to machine, with little scope for error.
I am making SOHC and DOHC versions of both the 5cc and 10cc singles, but I am making two interchangeable cylinder heads for the 20cc in-line 4, one SOHC and one DOHC.
On completion of the blanks, the first job was to machine the underside of the cylinder heads and to drill the bolt holes, which I did using the coordinate method with the DRO. There was also a job for the lathe with machining the recess in the under side.
Machining the underside of one of the 10cc cylinder heads.
The main profile of the valve banks and other features was then machined on the mill. There was quite a bit of metal to remove and it got a bit tedious, but all went well.
To machine the angled features on the cylinder heads, a fixture was made up. The rotary table was mounted vertically on the mill, with an angle plate bolted to the rotary table to form a sort of shelf. The rotary table was zeroed and the angle plate set roughly horizontal in the Y axis before tightening the mounting bolts. A slab of aluminium was bolted to the angle plate and a strip of aluminium bolted to the slab, to form a fence aligned with the X axis. The aluminium slab was skimmed flat with an end mill and the fence skimmed to align with the X axis. Bolting the cylinder heads to this fixture then allowed the angles to be set accurately using the rotary table scale and handwheel dial.
As a reminder, I am building five prototype engines as follows, to test the design in its basic configurations:
Engine 1. AMD5S, air cooled SOHC, glow ignition, lubricated by oil mixed with fuel
- Engine 2. AMD5S, water cooled, DOHC, spark ignition, oil pump
- Engine 3. AMD10S, air cooled SOHC, glow ignition, lubricated by oil mixed with fuel
- Engine 4. AMD10S, water cooled, DOHC, spark ignition, oil pump
- Engine 5. AMD20IL4, water cooled, DOHC, ignition method TBD.
The part-machined SOHC 5cc and 10cc cyliner heads.
The part-machined DOHC 5cc and 10cc cyliner heads.
The fixture used to machine the angled features on the cylinder heads.
Machining the angled features on the DOHC version of the 5cc cylinder head.
The 20cc in-line four with part machined SOHC and DOHC cylinder heads.
Dear Sir,
I was impressed to see your nice handcrafted model engines.Hats down.Wonderful.Nice works, and pleased to visit your web site.
I am a first class machinist and retired now and i have made some model gas engines in my spare time.
I encounter much problems for diesel as i cannot build a sound injector .I will highly appreciate if you could help me for the design and having all necessary tools at my disposal i am a sad man.I must confess that i have made numerous trials but simply failed for i cannot achieve the tight tolerance needed for the plunger and body and the results was only pure dripping .
All advices from your you will be most welcome and make me smile again just to think at Diesel engines.
Looking forward to receiving a favourable reply.
Very respectfully,
Richard Patient
Richard,
Thank you for your comment. I must admit that I am new to model engine building and these engines are experimental. They are designed for glow fuel and petrol. In terms of injectors, they won’t have any, but I am planning to use commercially available model aircraft engine carburetors on my engines. This will give the best chance of success I think. Although these can be home-made, the barrels would need to be lapped into their bores and they are quite critical. I don’t know much about diesel engine injectors, but I would suggest that for parts requiring a very close tolerance, some form of lapping would be needed. Alternatively, commercial parts for these critical components may be best. Sorry I can’t provide better advice, but you might like to try the forums on model-engineer.co.uk or other model engine forums.
Best regards,
Alex