What limits the redline in a rotary engine?

Like usually in a reciprocating engine it's the valvetrain or the balance. What is it in the rotary?

 

e-shaft?

 

I don't know for sure, but I was once told a story by some allegedly knowledgeable parties (suspension & chassis engineers for another Japanese mfg) that shaft flex, not sure if it's something balance related or a harmonic(s) issue of somekind, will become an issue at some point. My understanding of their description of the problem is that flex begins to create a cummulative problem leading to seal and bearing failures. But all of this is hearsay on my part. I've no personal experience with any such failure ~ knock on wood.

There are probably also spark and/or injector timing issues some place along the line. Perhaps the rotary god or, if you're pagan :-), gods will descend and provide further illumination.

 

do a quick search if you're still wondering, it is the e-shaft though. i'm pretty sure another thread asking a similiar question was discussed in greater depth awhile ago.

 

In the past, the problem was both eccentric shaft flex and stationary/rotating gear design. The rotors have an internal toothed gear that meshes to a stationary gear on the housing. As it rotates, it moves around the stationary gear (think spirograph toy).

At higher rpms, if the shaft flexes, the gears can skip a tooth, and (taa daa) you have a rotor slapping into the sides of the case. Instant shrapnel.

In the old days, the fix was a stronger eccentric shaft, and a different cut of the stationary/rotating gears. With this combo, you could go from a top RPM of about 8500, up to a racing RPM of about 12000.

Problem is that the different cut of the stationary/rotating gears caused much quicker wear. Needed to be replaced after just a few hours of operation.

 

I always throught the transmission was part of the problem as well. Finding a unit that could take greater then 9k rpm on the input side was difficult...

 

now i thought the problem was lack of good power over a certain RPM

 

From what I've read, the limit is related to the e-shaft flexing since there is no center bearing. When the shaft flexes the rotors get skewed in the housing and the sides of the rotors can contact the end or center plate.

Of course, without massive porting the pumping capacity of the engine will also be a practical limit.

 

every RX I've seen damaged from "over rev" has been from clutch/pressure plate failure.. not engine failure.

 

For the engine by itself, its the eccentric shaft. Do a search, there was a good explanation posted on here a while ago.

Once you put it into a car, its accessories and tranny, although those could be overcome without much expensive modification, underdrive pulleys, beefier tranny. Redesigning the eccentric shaft gets to a point of diminishing returns very quickly.

 

It's mean ole inertia.

 

Sorry I had searched but turned up nothing. I had to search under eccentric shaft to find the thread - thanks.

 

I had an instance, or two, where I had my Renesis around 11,500 rpm and it is holding up fine. I wouldn't plan on hitting that rpm on a regular basis, though. Just know that at 9,750 for a fuel cut-off point the Renesis has plenty of headroom for mistakes.

CRH

 

Yes I don't think we have to worried about destroying th engine if we mis-shifted.

 

hey CRH how did u get ur renesis engine at 11,500 rpms did u down shift when u were near redlin n didnt realize it??? im just curious i get to about between 9k n i believe 9.5 k n fuel cut kicks in......what did u do??? pm me back if u want

 

A mistake from downshifting, you said it yourself, 9.5k is fuel cut, and i rmb his post about that too...

I've always wondered if we can slap a rotary engine to F1 transmission and make the engine internals out of exotic materials(super strong and resistant to flex) and rev the engine to 20+k rpm, if the pistons can do it, i believe the rotaries can do it too.

It'll be PPorted and only needs to last a few hours, like the F1 engines. Probably would be easier to go with a 2-rotor, any idea what the hp would be at like 20k rpm? haha, 500hp+ perhaps?
________
Arrya

 

Yeah, I accidentally shifted from 6th to 2nd at about 80 mph on the freeway. It's far easier to do with a light fly. Here in the Detroit area we have a freeway that if you don't drive like it's an F1 race you'll get knocked off the road. From what I have observed the fuel cut comes in at 9,750.

CRH