VW Beetle engine 1/5 scale

[Arild]

Not to take you too far off into the weeds but how much pressure does it take to push the hot rubber into the mould and what kind of connector are you using for the top of the plug? Bob

I cut the rubber to fit into the mould. Not a precize cut at all, just making sure there is more rubber than actually needed. The add temperature and the rubber become very soft. There is not a high pressure needed. You could have done this in a vice if you had hot plate on each side of the mould. I guess some 100kilo for 100cm2 (I dont have a gauge on the vulcanize press.).

I had to use a 1kohm (1/4w) resistor in the rubber boot, if not my microcontroller chrash. I simply make some loops at the end of this resistor to touch the sparkplug. There is enough friction on the rubber, so it wont fall off.

 

[Arild]

It's going slowly, but I'm not in a hurry.
No customer is waiting for me! Last week I've been milling out holes in the crank case for the cylinders, and also turned the last cylinder! Then making studs x 16 (not cut to lenght). It's from Ø2.5mm 316, so pretty hard. The M2.5 die I got is of poor quality, so the threads does'nt looks very good. I have to purchase a better one on Monday. Ghuring or Swiss-tech, or..."Baer"(never heard about Baer, but expensive, is that good?

 

[Peter Twissell]

Nice work.
I'm not sure about 316 for the head studs. It's not easy to thread nicely, especially at small diameter with a die. Stainless threads have a tendency to gall in use.
I would have used EN16T. Higher strength and stiffness and easier to cut a nice thread.

 

[Tom-AMS]

Looks Great - NICE job!

head studs on 1300, 1500, 1600 cc VW air-cooled engine with single-port heads, were 240mm long for the lower row, and 202 - 204mm long for the upper row. M10 x 1.5 threads. In 73, VW switched to M8 x 1.25 threaded studs made of a better grade alloy, that acted more like a "spring". Performed significantly better.
Rocker ratio was 1.1 : 1

Have been thinking about how to make the corrugated pushrod tubes ... have you considered hydro forming thin tubing? ( maybe from 1100 or 3003 aluminum, may have to machine your own tubes from solid bar stock to get size & wall thickness to suit 1/5th scale) Machine a split die from alum or steel with rounded grooved to form the corrugations set back say, 5mm, from the ends. Plug the ends of the tube, with one plug fitted for a common pressure** washer hose connector. you can always cut off excess from ends, if threaded plugs are used.
** like the unit used in this video
Alternatively, a split block die just long enough for one end's corrugations could be clamped/bolted tightly around a one one of a tube held in a lathe chuck, make a tool with an appropriately sized/shaped smooth steel "roller" wheel, to fit inside the tube, and while spinning the tube/die assembly, "align the wheel with a groove to roll-form the corrugations. Dead soft annealed copper tube may work too, although you may have to roll in stages and anneal with a propane torch in between - to prevent work hardening. leave straid tube enough on the ends to fit o-ring seals. The VW are made of welded seam steel tube with approx 0.45 mm thickness.
One last thought: make a die for small rubber bellows to slip over a length of straight tube, with the tube being a couple of corugations shy in length.. make one end of the bellows a bit thicker, to act as a seal. The assembly will look similar to the original tube, flex into position and seal.