Former RC airplane pilots...need your help!

[blueskydriver]

Hey Everyone,

This posts is about RC airplane engines, which is a little outside the scope of the CB, but I know there are some former RC pilots that became sim pilots, as well as those that veered towards RC. I am one of the few who does both 100%, no the math doesn't add up, but it does when I am applying myself...lol!

Anyway, my question is regarding piston/sleeve pinch of a 2 stroke nitro airplane engines. I recently ordered two engines worth of parts from Just Engines in the UK. They are the Irvine .61 red and Irvine .72 red. Now, for anyone not knowing or who are curious, any Irvine reds were considered top of the line back in the day when Just Engines made them (a company started by a husband and wife team back in '91; see link here:

http://www.justengines.co.uk/acatalog/More_Info.html

Unfortunately, the Irvine reds are no longer available, but spare parts still exist. Therefore, if you can see this as something like re-building a muscle car engine or even a simulator, you'll know that you might replace 99% of the parts with scrouged, but new, OEM parts, or rebuilt parts or even aftermarket parts. So, in my case I purchased enough new OEM parts too build two engines or in the RC world, I am doing a "kit build". Which means there are occurrences that make no sense and there are very few people you can ask, hence my posting here.

The problem is with the non-ringed piston and the sleeve set. When I rotate the crank up to TDC without the head in place the sleeve slides up about 5-7mms out of the crankcase. Okay, so that would be fine because the pinch is tight in a new piston/sleeve set and that is why an engine must be broken in; however, in my case, once I put the head on with the head screws torqued down the piston cannot go beyond TDC either direction. If I force it the piston rod or wrist pin would likely break, so how do I resolve a too tight pinch of a piston/sleeve set?

I did send an email to Just Engines, but due to time zones, I might not get an answer until Monday or Tuesday next week. Plus, I did enough web surfing and YouTube watching to make me dizzy, but there is not much regarding it being to tight, it's more so about re-tightening or re-pinching a loose set. Still, I have everything "in the works" so to speak, all over the workbench and I really want too complete this project this weekend and before moving onto something else (you know how that is right?).

If any of you old school former/current RC pilots are able too help I would be very grateful...

John

[Trevor Hale]

John,


Not that this will help, but I run RC Boats in the summer, I use the K&B 3.5cc outboards. In any case when I blew the piston and connecting rod on one of my motors they came with a replacement sleeve. For inside the head. I remember having slop also like you said though when I placed the top of the head on, it held the top lip of the sleeve in place. When I turned the crank it was also tight, but it was a long time ago and I am trying to remember. I think what I ended up doing was putting a piece of gasket material on the top of the old cylinder head and then Fit the sleeve down on it. The sleeve is tapered for a reason. This raised the cylinder sleeve up about a thou or more and when the head tightened down I didn't crank it super tight. This raised the cylinder sleeve enough to allow me to go past TDC.

This is just what I did and it worked for me. It may not work for you.



As soon as the motor runs, the heat it generates will expand the sleeve and it will lock into position.


you should only need to raise it a tad and you should be able to go by TDC. If you need lots. Then something is wrong with the piston and sleeve set you got.


Trev

[blueskydriver]

Hi Trev,

Thank you for providing this information, it really does help a lot. I never thought about placing a gasket under the liner top rim like you said. This engine does have aluminum gaskets or called shims included and they go between the head and the top of the liner in a sandwich fashion (head, two gaskets and liner top). I will try adding a piece of gasket material and see what the outcome will be...

John

[blueskydriver]

Hey Trev,

Thanks again for the suggestion, I used the shims and a precut copper gasket. Placed them between the head and the liner top, which made the TDC much smoother. Started the engine and it purred like a Tiger, just waitng to rip up the meat of the sky...lol!

John

[Trevor Hale]

No problemo bud.  Glad I was able to help.


Trev