Engines > Restoration of Model Engines
Fitting a piston for F2C engine
Ramon Wilson:
Ken, I should indeed have said – welcome to our forum :hi:, Re-reading my post it could be misconstrued as unwelcoming - there was no offence intended I assure you.
Your background in model engine making will readily find a place here :ThumbsUp:
However, in the past I was asked, and encouraged, by Jo and other members to describe the lapping and honing of small pistons and liners for the benefit of the Forum. As stated at the time it was not the way but my way based on the teachings of George Aldrich. As such it was in direct opposition to your statement - I felt there was no option but rebut your inference that this method was seemingly not acceptable at any cost. I’m certain you would agree that there many ways to skin cats - we all have different approaches, this is one of those situations.
Looking forwards to your input on small engines and other matters over coming months :)
Regards - Tug
Neil-Lickfold:
Model engines are very interesting beasts. In my case if a lapped finish was the ultimate, I would be doing that. Instead I spent considerable time getting my lathe in good enough condition to be able to turn the piston to size. If the engine was a sport engine the effort would be hardly worth it. Like people have said, many ways to achieve the same end result. Some use sunnen type external hone's.
Ramon Wilson:
Sometime ago Neil I bought a Delapena internal honing machine and shortly after, two totally unused sets of external hones. I have never used the internal - it still sits in a state of re-build, and though I have used the external ones I find a home made brass external lap to be a better and very effective and accurate method of controlling piston size.
The internal laps described elsewhere on here have also provided sterling service over the years giving a high control over the operation but without accurate measuring kit lapping the piston to the bore has been the final operation. The proof is in the pudding so to speak and I can only say that I have had very good success with this method in the engines made so far. The technique used was described sometime ago here http://www.modelenginemaker.com/index.php/topic,1908.0.html. I prefer to lap for all the reasons stated but your method is one I intend to attempt on this next build - begins today BTW ;)
Tug
b.lindsey:
Thanks Ken, and welcome to the forum.
Bill
Rick Doane:
Hello Ramon and Neil:
This is still a great subject that never goes away with time. I have not had the ability to machine to the extent that most here have but, using the engines available to the public generates an opportunity to improve on certain details. Specifically the piston and liner fit. I have used billet pistons made from 4032 Al (~12% Si) to what I believe is ~20 % vendor cast pistons with vendor supplied liners, ABC type. I do not have any experience with 30% Si products. My approach was to heat treat the cast piston and make it grow. Then I used 3 micron diamond compound to fit the piston to the liner. Learning when and where to stop was the trick(?). These motors use 65% nitromethane lasted approx. 14 gallon for fuel turning 28,000 RPM in a 6 pound hydroplane. Top speed was approx. 87 MPH in heat racing trim.
The attached photo is from the left, a 4032-12% piston that you can see the lead screw imprint, not good, then, center, a new properly lapped piston, and far right a piston that lasted 14 gallons on 65% nitro with a seal that was amazing.
I will post a photo of these pistons later when I figure how to reduce the size. Thank you for your patience.
Rick
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