Originally Posted by
ken seeber
Ringless pistons. Of course rings add friction, but the trade-off is that they also provide the proportional sealing of pressures, up to around 90 bar (1300 - 1400 psi) at all sorts of rubbing speeds and high temperatures, not a trivial task. Should they fail, as we’ve all seen with a stuck ring; blowby, loss of lubrication and death.
In a small engine, say a glow plug, one seemingly can get away with it, mainly due to viscous sealing because of the typically 20% oil quantity in methanol &/or nitro fuels, and possibly lower overall temperatures inherent in small engines due to the surface area to volume ratio effect providing a much greater heat transfer rate, at the expense of inherent lower overall thermal efficiencies.
Another thing that has been demonstrated, is that the crevice volume, formed between the bore and the top land above the ring, can result in trapped mixture, leading to unburnt HC emissions. This is why rings have been become higher up the piston. This is not so critical in a stratified charge running condition where, hopefully, only air or burnt gases enter and leave the crevice volume.
I am personally of the belief that a large percentage of the heat from the piston is transferred via the ring and rubbing contact of the ring land (the hottest part of the piston) against the bore. This effect is greatest at the TDC and BDC, where the piston land and ring area have the greatest residency time over the cycle. It is for this reason that cooling of the cylinder is best directed at the very top and also adjacent to the BDC area, usually within the transfer passage cup handles.
If Harry is chucking out all that extra power, relative to current levels, then he will have to provide great attention to the piston cooling, does he have a piston?
As to bearing life, things are going to get tough. 100cc rotary / reeds used to rev to 21k, but there were issues.
Sometimes big ends, but with the older vertical reeds aiming between the crankwebs, the big end got much better cooling and lubrication that the now current horizontal reed blocks.
Mostly though, it was piston failure, leading to a rod, then unconstrained, scything its way through the crankcases, ignoring all the M6 screws on its way. A 90 mm rod, over the standard VM rod of 110 mm, is going to place more side thrust load on the piston boss area.
Maybe if it is a wet sump, using the Honda aerated oil lubrication system and retaining the roller bearings, then this could help, bearing in mind that, with the 25 mm spacer plate, the crank/big end will be more remote from the heat source. If it uses plain bearings, then this pretty much implies some sort of high oil pressure system. Maybe there is no big end at all, but some other clever gizmo.
Back to the piston or whatever it is that goes up and down, it will have to be strong to take 30k, but maybe its motion and forces were opposed or dampened, then strength might not be so paramount.
Many a maybe.
He might have done all this and the thing is a real goer with all the claims we have seen. Good on him if this is the case and maybe the world will be a better place. It will inevitably mean change and change means winners and losers. That’s life.
But the good thing is that no matter what improvements have been made, things can always be improved. That’s what you bucketeers are all about.
... and the Leaning Tower of Pisa
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) says to "remove the spring sheet, then slowly pull out the spring". How is this done with out breaking down the damper rod setup? i.e. The spring does not fit over the top of the damper rod.
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