DaveMarles

Patrik, I read with interest your technical breakdown of the forces involved and of course your discussion elsewhere on propeller rake. Surely in the case of a reciprocating mass, is it not true that mass is load because of the inertia effects? This is the way that I see it. More simply it takes energy to stop and start the piston at each end of the stroke and the heavier the piston the more energy is required. Exactly as Mike Gilman used in his analogy. Perhaps I am misunderstanding what you mean by load.
In practice I see that in my gas engines and my high revving nitro engines that the efforts I make to reduce reciprocating mass have a direct effect on the performance and reliability of my engines compared to others. As far as I can see, reducing reciprocating mass has no downside apart from the time spent doing it and assessing what is safe.

patriktegelberg

Thank you, I also enjoy this kind of more scientifically rigid reasoning. I do not dispute that reducing reciprocating mass have a direct effect on the performance and reliability. I am here merely looking for the theoretical understanding behind, without which I find myths can sometimes be passed off as knowledge. Being aware of your merits and education I am convinced that you know what you are talking about and that our disagreements are most likely because of misunderstandings on a linguistic level.

Since we seem to agree on most of this subject and have had a healthy and elucidative discussion on its workings I feel no particular need to take this to absurd lengths. I will though, point out that in the acceleration of the piston it gains energy as the flywheel looses the same amount. In the subsequent retardation of the piston this energy is given back to the flywheel so that the total energy (Hamiltonian) of the system has been conserved at all times.

MrMikeG

Thanks Dave for translating for me!
45DV, Balancing the rotational mass and balancing the piston are two different things. Balancing the rotational mass is very important, benefits multi cylinder engines more than single cylinder engines though. If you go to Dave Marles website he has a great article on balancing the single cylinder engines (or lack of)

http://www.prestwich.ndirect.co.uk/t..._balancing.htm

Tidnab

My Feedback: (51)

strong,I also have a Sikk 25.4 engine and wondered if I could get a little more out of it and thought of a modded piston.I don't like to start cutting into something unless I know a little about what I'm doing,so I might practice on a couple old weedeater pistons to get the feel of how fast and how much the cutter takes off on a pass.I then contacted Mike at Redline Motors and asked if his modded Zen 260 piston would work in a Sikk and after checking he got back to me and said it should be fine to use.Has anyone used one in their Sikk and how did it run?I may consider getting one until I'm sure I can do my own piston work.Good luck in your mod job.

strong

Well being that the zen piston is lighter already .........................Im just going to use one of them I have and try to lighten it some more...............As far as grinding...........I'm using a tungsten carbinde cutter which is not going to take off to much at one time....................I'm more concern with the little clip than the grinding part.[]

MrMikeG

Just make sure you re-install it with the opening pointing up and both ends are securely in the grove!

strong

Well...............Got to try my sikk with the lighten piston today..............It didn't seen to give a whole lot more on the top end...... But did excelerate much better.....I Think I could have remove more metal from the piston but why chance it.....But it feels good to know that I can do this one mod...........Can someone tell me If port timing wiil give me some more RPM's

MrMikeG

What RPM are you doing now?
What pipe are you running?
What prop?

strong

Running the hanson cone to cone pipe.....................The prop is a modified one........I forget what size he said it was.................have not really tact the RPM's.........Just been using the GPS to find what speed it runs..............Don't get me wrong......The engine runs good,with speed right around 60.........Just want to get all I can out of it so as to keep up with the Quick draw and moded Zen at the pond.[>:]

MrMikeG

The Hanson cone to cone pipe is holding you back (in my opinion they are my least favorite) I have 2 or 3 of them and they just aren't as good as the band pipes or steel pipes.

strong

what's the best band to get................Don't like the way the steel rust

MrMikeG

I would get one of these new 2" band pipes with the 1" header like in the bottom pic on this post.

http://p086.ezboard.com/fjimsrcboatd...cID=6127.topic