RXSevenSymphonies

iTrader: (2)

so the gears won't separate themselves from the rotor

I'm not sure if he experienced chatter marks or not, I can ask him about it and find out more details.

ddub

I'm sure it created some chatter. When I was talking to him he said the engines he ran were only used for a short while, or a few long endurance races at most.

But slight overrevving doesn't seem like that big of a deal to me on stock balance. His races were done at constant high rpm use, 13k-17k range, so obviously the wear is a lot faster and a lot worse. With a 7k redline going to 7500 or 8k or even slightly higher doesn't seem bad to me. I believe Mazdapseed7 built his engine and went to 9 and 10k easily with stock balance, no sustained use at those rpms but just hitting them sometimes. He did have hardened gears and plenty of oil mods, though, but that still doesn't really change the chatter factor much since the balance was stock. He tore the engines down regularly and never really experienced too many problems from what I could tell in his pictures and posts on nopistons.com

mwatson184

My clutch exploded at 9000 rpm.

Just because you "can" rev to 17000 rpm doesn't mean it makes sense to. What kind of port can flow that much air? Full on PP cars rev to about 13k at the most from what I've seen.

mcnannay

^ and im just guessing that your clutch was stock, which is obviously why it exploded.

and i agree with the flow issue, the ports would have to be pretty massive to make power up to 17k

pengarufoo

The balancing is overrated, the whole system gets out of balance during operation anyways, theres oil being squirted into the rotors, add in the outside forces of the car moving around and the balance will be always changing depending on where the oil is concentrating at. Think about why you need an oil pan baffle or dry sump, the same forces that cause these to be needed are acting on the oil inside the rotors. It can't hurt to rebalance the assembly, but as long as it's close I don't see it being a problem.

The stationary gears take most the beating of high revs, and the 12A's I suspect can rev higher because the rotors are narrower than 13B rotors. The engine has no bearing support in the intermediate housing, with the 12A setup there is less distance between the stationary gears thanks to the narrower rotors. Narrower rotors will have a center of gravity closer to the stationary gear causing the eccetric shaft to flex less, this combined with the shorter shaft length between the stat gears makes a significant difference with regard to high revs and the effects it has on the eccentrif shaft (flexing) and how high you can go before the rotors start hitting the side housings.

just my $.02, but 13B rotors are 80mm thick and 12A 70mm IIRC, 1cm is a pretty sizable difference, if you apply that to the shaft for both rotors thats 2cm lengh difference between the two stationary gears (where the bearings are), that eccentric shaft is going to be more rigid than the 13B shaft being shorter, I'm not sure if theres a signficant diffference in length in the section between the rotor lobes as I don't have a 12A shaft on hand to pull some measurements off of, but I imagine it could be more than 2 cm shorter.