Twin rotor Peripheral port

[Grizzly]

Can I ask, why can piston cranks rev to 20k and much shorter shafts in rotaries go to 12k, there must be less whip or is it the centrifugal forces that make the difference?

One word...... MONEY!!!

But Rotarys have a problem, The faster the Rotor spins the harder the apex seal pushes on the Housing and the harder it pushes the more friction it casues until it Burns out and looses Compression, You could make it rev realy High but you\'d need some real Light Apex\'s (carbon are the wepons of choice)

[Grizzly]

Is there a optimum compression for turbos.
ie low comp with x psi boost making the same power as high comp on low boost, is there a benefit one over other if same power, or is it not possible to create same power?

The Compression being lower on a Turbo makes it more stable to tune at higher Boost levels. So effectivly able to run more Boost safely but the down side is it will spool slower and feel less responcive.

The higher the Comp the more likly it is to Det, but the higher the Compresion the more Hp per PSI you get.

NA\'s are basicly the same, If you have a higher Comp you will find it harder to set up but you will gain more HP at the end. NA\'s are all about getting the Compression as good as you can.

[banned advertiser]

One word...... MONEY!!!

But Rotarys have a problem, The faster the Rotor spins the harder the apex seal pushes on the Housing and the harder it pushes the more friction it casues until it Burns out and looses Compression, You could make it rev realy High but you\'d need some real Light Apex\'s (carbon are the wepons of choice)

Perhaps one for Stu, as you are experimenting/building now.
Please forgive my ignorence.
If it pushes harder the faster it spins, whats to stop a slot to be cut in to the seal and some sort of stop or pin to stop it raising above a given height, so no matter how hard it spins, the seal stays at max height.
Sorry for over simplifying things.

[shaunwil]

Thats an interesting question what stops you from milling a t-slot in the end of the rotor and having a t-shapped apex ?

Shaun

[banned advertiser]

thinking about it, you could not do it on 2 piece, and one piece dont seal as well, would like to know though if its possible?

[shaunwil]

how exactley do the two peice work If they where next to each other you could have a t-slot and 2 opposing l shaped apex\'s !

Shaun

[Glenn Butcher]

Gary and all - have a read through this thread (long thread though!): http://ausrotary.dntinternet.com/forums/viewtopic.php?t=74605&highlight=thought

[stuart wizy]

good idea gary about the seals, but dont the seals wear down like brushes in a motor with springs behind  pushing the seal out more and more as the seal wears down?
when i took the old fc apex seals out, they are 3mm shorter than new atkins seals in height.
if u stopped the seal from being pushed out so far it would eventually loose compression.

[stuart wizy]

how exactley do the two peice work If they where next to each other you could have a t-slot and 2 opposing l shaped apex\'s !

Shaun

the 2 piece seals are both angled of at 45deg on one end , the spring goes under both seals with the angles crossing each other on ends of 2 seals.
when the longer seal is pushed up by the spring, it pushes the shorter seal up to.

[banned advertiser]

good idea gary about the seals, but dont the seals wear down like brushes in a motor with springs behind  pushing the seal out more and more as the seal wears down?
when i took the old fc apex seals out, they are 3mm shorter than new atkins seals in height.
if u stopped the seal from being pushed out so far it would eventually loose compression.

Yes they do, but if the springs had say 1-3mm of play before hitting stop that might be better then not being able to run 18-20k rpm.
Also this would undoubtedly be a race car, so would be stripped and seals only replaced, dont know how much wear you would get from 1 race, maybe a whole season would be equivelent to the 3mm wear. Just ideas mulin round to get the high reving race engine. See a problem and look for a cure. Sorry I do over simplify things as Im not an engineer and dont appreciate what you need to over come

[Grizzly]

Perhaps one for Stu, as you are experimenting/building now.
Please forgive my ignorence.
If it pushes harder the faster it spins, whats to stop a slot to be cut in to the seal and some sort of stop or pin to stop it raising above a given height, so no matter how hard it spins, the seal stays at max height.
Sorry for over simplifying things.

Urm, a few things, The first if you cut the seal it will create a weak point, the seal has to move in and out or it would brake off so you can\'t hold it back.

To simplify things, the weight + Centrifugal force. If you add more weight the force will get greater for a given RPM, so there is two things you can do to reduce this the first is less rpm the second is to make the seal ligher.

[Grizzly]

Yes they do, but if the springs had say 1-3mm of play before hitting stop that might be better then not being able to run 18-20k rpm.
Also this would undoubtedly be a race car,

This would mean it still is being pushed against the housing with its own weight so would still be subject to the extra load.

[Grizzly]

As far as i can see there are Three big problems with running very high RPM, the first is the apex seals, the second is the E-shaft flex and the third is the harmonic vibration. this alone can cause some serious problems with the Bolts holding the engine together (tends to ither snap them or loosen them)

The first on a race engine that see\'s 10.000rpm and gets rebuilt alot will use Carbon seals, There usless for road or high hp use but there is not better seal for Big RPM runs.

The second is the most easy to put right, you can Lighten the Rotors, Clearance to suit or Fit a E-shaft with a center bearing.

The Third Can be a royal pain in the Rear, as i\'ve never build a high Rpm NA i\'ve not looked into it too much but i\'m told oversized Bolts that are matched to the Housings/Plates is the best way but people put rubber tube over the stock bolts to dampen the Vibrations (i\'m not sure if this works though??)

O yeh the one i forgot, Flywheels exploding at High RPM and with a good amount of power.

[stuart wizy]

this is no bull now, but when i was 2nd year aprentice at holroyds there was a pair of billet machined mazda type rotors on a pallet in  inspection dept for months!
my foreman at the time said they where mazda car engine rotors that we were machining for holroyds jap rotor sales guy- sanechi terasoa.
im going back 10 years but always remeberd the jap guys name going over tannoy!
I think this guy had something to do with mazda and the rotary.
glen u might no something about this guy.
as long as i was there, the rotors never got finished and stayed on the pallet gathering dust! so nothing ever come of it.
at the time i knew nothing about rotary engines so didnt take much notice!!
they were turned and milled to shape with billet pieces left on both faces of the rotors to grip on but  side seal grooves where never cut.
all the rotors that holroyds make are screw type rotors for compressors, aircraft, fridges, fuel pumps etc etc,

[stuart wizy]

for really high revs you need different bearings than white metal.
workheads on grinding machines have main drive spindle normally using phosphur bronze bearings with oil grooves in the inside bores for good lubrication, some spidles can spin well over 30 000rpm,
just think of a turbo , main shaft on a loose fit (sloppy) phosphur bronze bearing, these will spin at 150 000 rpm but need the oil big time/