Mills 1.3 cc Drawings

[KEITH BEAUMONTParticipant @keithbeaumont45476]

[KEITH BEAUMONTParticipant @keithbeaumont45476]

In searching for something else, I have rediscovered parts of a Mills 1.3 left over from my teen years. Missing are the piston, cylinder, contra-piston and finned head.Clearly, a project to make the missing bits is called for ,but I need the drawings. The late Ron Chernich published these in 2002, on his website. I understand, and I wonder if anyone out there has access to them ,or can point me in the right direction.

Keith

[JasonBModerator @jasonb]

Ron did a build article which was published along with the drawings in the first issue of Model Engine Builder Magazine. You can buy digital back issues quite reasonably.

Go into "subscribe" and "subscribe online now" then select paymment method and finally you will get the screen with all the back issues listed.

J

[KEITH BEAUMONTParticipant @keithbeaumont45476]

Thank Jason, I will do that. I had been searching for that link, without success.

Keith

[KEITH BEAUMONTParticipant @keithbeaumont45476]

Hi,

I have recently completed making the missing parts for the Mills 1.3cc and wonder if anyone else has made one from the late Ron Churnich drawings? It is always very satisfying to hear an engines first start up after completion and this one starts first flick after a prime and I suppose I should be happy with that, but after about an hours total running, it still will not run much over 6000 RPM,what ever prop is tried. The spec says 10,000 RPM.Compression is perfect and that nice "bouncy" feel when turned over.

I have a great respect for the contribution Ron made to our hobby, but in making this to his drawings and notes I had some doubts about a few things, but nevertheless followed his notes.He does say in the preamble to them that he has not copied the original engine exactly,thinking it would be unethical to do so with what has become a collectors item.He does not say what the difference is.

I think I found out the hard way,as I had an original crankcase and con-rod. When completed it would just about run on a prime, but was clearly not right,so after a strip down and a critical check on everything I realised that the datum top face to crankshaft centreline on the drawing was 0.100"lower than my crankcase and ditto with the con-rod. Clearly this had totally altered the timing and it was a wonder It ran at all.

Two other instructionsI I followed that seemed odd is he advised not to make the liner a tight fit in the crankcase"only an easy sliding fit as differential expansion will tighten thing up" A look at the section G/A shows that a leak path between ports is then a possibility. I compromised by having a push fit.The other query is with lapping the liner/piston fit, advising a taper of 0.0015" to TDC.For a piston under 0.5" diameter this seemed excessive and wasRemachining the crankcase was no problem, but the new con-rod made to the drawing was nothing like the original and is straight sided with no "dogbone" shape and would only just push in the piston with no room for movement. It also touched the crankcase. I re-made it in the same shape as the original. I also re-lapped the liner to give 0.0005" taper at TDC and"grew" the Meehanite piston by over 0.001" on diameter to allow re-lapping to that perfect ffit we strive for

[Andrew TinsleyParticipant @andrewtinsley63637]

Mills dimensions could be somewhat variable, so don't be too surprised if things don't go quite right. My 0.75s do have a variation in conrod length. Also I could never understand why the two inlet ports (read drilled holes) were never at the same height. This staggering also varied.

The "solid" crankcase Mills 1.3 was never as powerful as the Mk2, This caused Mills brothers to revise the timing for the Mk2.

A very nice looking job too, better than my Mills Mk1 restos. I shall have to revisit them I can see!

Andrew.

[KEITH BEAUMONTParticipant @keithbeaumont45476]

Hi Andrew, Thanks for your comments. Thei Chernich drawings show both Mk1 and Mk2 and the liners are the same. Ron says the timing for both is the latest adopted by Mills.The transfer ports are two holes drilled radialy but on the same level

Keith

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