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- Sep 7, 2011
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Being completely new to RC GASSER boat's and engines, I am curious- do all the popular GAS engines employ piston rings? Or are there non-ringed types as well? (like ABC construction?)
DavidBeing completely new to RC GASSER boat's and engines, I am curious- do all the popular GAS engines employ piston rings? Or are there non-ringed types as well? (like ABC construction?)
Cheers Mark,,I think it was a Lohring Miller article on testing the CMB when it first came out,that I found on the net somewhere,,I suppose only 1 ring cuts down on friction in racing 2 strokes,and be thin enough to prevent ring flutterRod, you are correct on the CMB, it has a single piston ring shown on the IPB. It's listed as part 11 but also shown as part of assembly 9(piston and ring)
Oh nice,,that would look good just sitting on your shelf at home or wherever,,lol,,its a nice looking unit, and with a zimmerman disc intakeTo be honest, when you mentioned the CMB, you got me curious as I have the 27cc gas engine at home(unfortunately, I'm presently at work). I figured it would be an easy one to look up so......
Great article you wrote on that test Lohring,,on Modelgasboats.,,you really pushed the limits on that poor little engine ,till the crank flexed and flogged out the wrist pin holes at 23-25,000 and around 11hp,,quite impressive,,was the spark timing static/constant or did it have some sort of advancing system?We were one of the early users of the ringless CMB 35. We never could get it to run without seizing. We even seized one of the ringed pistons. The sleeve was out of round above the exhaust port. I don't know of any large ABC or AAC gas engines. Gasoline burns a lot hotter and there are thermal expansion issues.
An early modification to the old two ring Zenoahs was to remove the lower ring.
Lohring Miller
Lohring,We were one of the early users of the ringless CMB 35. We never could get it to run without seizing. We even seized one of the ringed pistons. The sleeve was out of round above the exhaust port. I don't know of any large ABC or AAC gas engines. Gasoline burns a lot hotter and there are thermal expansion issues.
An early modification to the old two ring Zenoahs was to remove the lower ring.
Lohring Miller
thanks LohringI don't know of any large ABC or AAC gas engines. Gasoline burns a lot hotter and there are thermal expansion issues.
you're saying the Zenoah had fixed timing?Thanks. That was one of our more organized test series. We ran a Quickdraw electronic ignition system on the CMB. We tested it on Zenoahs as well. It had fixed timing that we set the same as the magneto timing. It's main advantage was compactness and light weight
I am interested in how the motor ranThanks. I have the latest CMB 27.0cc Alpha-EVO2 engine. Going into a "Kraken 52" (50in) mono.
I will post once I run itI am interested in how the motor ran
interesting. They are ringed pistons without the ring's installed? Or regular pistons with no groove for a ring?Have a pair of CMB35s that did a few short runs with no rings without issue. I know the instructions were pretty explicit about what size water fitting to use etc and remember hearing of a few seizures at the time. CMB sent through new ringed pistons to retrofit it. Have only bench run since.
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