ESE's works engine tuner

[lohring]

Really high power two strokes were investigated starting in the 1930s by Sir Harry Ricardo. His testing resulted in the Rolls Royce Crecy. However, gas turbines were going to be the obvious choice for all but the smallest aircraft engines, so development stopped. In the end he got a BMEP of 325 psi with an intake pressure of 36 psi and an exhaust back pressure of 12 psi. That was more than enough exhaust pressure to power a compressor. Napier took the concept even farther with the Napier Nomad. There a significant amount of turbine power could be fed back into the crankshaft.

Lohring Miller

[F5 Dave]

I'm confused. What are suspenders for?

Also why not just make a 250? Light weight, small size and fuel frugality seem to have been jettisoned, so. . . ..?

[Flettner]

Forget all this nonsense, just go Uniflow. 175cc

[yatasaki]

Forget all this nonsense, just go Uniflow. 175cc

Transfers tangentialy directed or other options?

[Flettner]

Transfers tangentialy directed or other options?

This one in the video, two tangental, four central collision, each cylinder. Transfer pistons 56 dia, exhaust pistons at 50 dia. So a little squish.
https://youtu.be/BPr694nlUKE

[Flettner]

Transfers tangentialy directed or other options?

This one in the picture, other.

[wobbly]

But Flettner , the desire was to make the most powerfull 2T /cc on the planet , not a tractor engine.

[TZ350]

But Flettner , the desire was to make the most powerfull 2T /cc on the planet.

That would be best done with a super or turbo charged Creasy style two stroke sleeve valve engine.

Sleeve valve arrangement Flettner made a while back.

[Flettner]

Cant argue with 325 BMEP.
https://youtu.be/6keqpL3rmwk

[wobbly]

So using the usual formulae , starting with BMEP = 150.8 x Torque ( ft lbs ) / Cubic inches and transposing Hp = T x rpm/5252 into this for a 50cc engine pulling 17,000 rpm
we end up with ( 50cc = 3.05 cu in )
bmep ( 325 ) x 3.05 x 17,000 /150.8 x 5252 = 21.28 Hp.
This would give us something worthwhile - making the assumption of course that the sleeve and its associated mechanism can survive at 17,000 rpm.
This is a modest 22M/sec piston speed for a square 50cc engine.
Achievable , dunno , you tell me.

[Flettner]

No, Harry Ricardos supercharged sleeve valve twostroke engine running in his back yard for 1000 hours. 325 BMEP, Id be happy with that. Open ended sleeve, no sealing ring.
Not my one, dont know what BMEP it is. Probably 5.

[andreas]

So using the usual formulae , starting with BMEP = 150.8 x Torque ( ft lbs ) / Cubic inches and transposing Hp = T x rpm/5252 into this for a 50cc engine pulling 17,000 rpm
we end up with ( 50cc = 3.05 cu in )
bmep ( 325 ) x 3.05 x 17,000 /150.8 x 5252 = 21.28 Hp.
This would give us something worthwhile - making the assumption of course that the sleeve and its associated mechanism can survive at 17,000 rpm.
This is a modest 22M/sec piston speed for a square 50cc engine.
Achievable , dunno , you tell me.

Is this still the two stroke forum? 75.4 ~42.6 hp

[Frits Overmars]

So using the usual formulae , starting with BMEP = 150.8 x Torque ( ft lbs ) / Cubic inches and transposing Hp = T x rpm/5252 into this for a 50cc engine pulling 17,000 rpm
we end up with ( 50cc = 3.05 cu in )
bmep ( 325 ) x 3.05 x 17,000 /150.8 x 5252 = 21.28 Hp.
This would give us something worthwhile - making the assumption of course that the sleeve and its associated mechanism can survive at 17,000 rpm.
This is a modest 22M/sec piston speed for a square 50cc engine.
Achievable , dunno , you tell me.

Wob, good news: lately we have a wonderful system of units available: the kilogram-meter-second system. It functions in the same way as your trusted hundredweight-furlong-fortnight system, but without your precious constants. It may also save a few cubic feet of aspirin.
By the way, if your desire is to make the most powerful 2T /cc on the planet, the bad news is that 21,28 hp out of a 50cc engine won't cut it. In the Netherlands alone, there are already various 50cc machines with 24 hp on board, not at 17,000 rpm but well below 16,000 rpm. And looking a bit further, there was an Aprilia engine you may have heard of, called the RSA, with 54 hp at 13.000 rpm from 125 cc. A 50 cc engine with the same BMEP ought to deliver 29,6 hp at 17.800 rpm, so our 24 hp bikes are not really that special; they still have some way to go.

Either way, 'most hp per cc' is a pointless endeavor. I have a 6,5 cc engine lying here that produces 5 hp without supercharging, without nitro, without nitrous oxide, simply with 80% methanol and 20% oil (which is far too greasy for good power), and with glow plug ignition. With spark ignition it would probably reach 1000 horsepower per liter.
Hp per cc per 1000 rpm would be a better yardstick (or should that be meterstick nowadays)?

[ken seeber]

Frits, just saw your post....your proposed specific power index looks more meaningful and relevant.

Still, I'll post what I was going to post

Below, as a refresher, is link to explain BMEP:

http://www.epi-eng.com/piston_engine..._yardstick.htm

Not sure if this below covers the full history:

https://en.wikipedia.org/wiki/Rolls-Royce_Crecy

However, if it was going to seize, I’d take it in a tractor rather than 25,000 feet in the air…just a simple pain avoidance preference though…

[Frits Overmars]

Frits, just saw your post....your proposed specific power index looks more meaningful and relevant.
Still, I'll post what I was going to post
Below, as a refresher, is link to explain BMEP:
http://www.epi-eng.com/piston_engine..._yardstick.htm
Not sure if this below covers the full history:
https://en.wikipedia.org/wiki/Rolls-Royce_Crecy
However, if it was going to seize, I’d take it in a tractor rather than 25,000 feet in the air…just a simple pain avoidance preference though…

Ken, my proposal is no better than the BMEP-approach. I only left out the constants, so everybody should be able to do the math.
Speaking of which, I translated the Crecy's 5.1" bore x 6.5" stroke into 129,54 x 165,1 mm, giving 2175,93 cc per cylinder and 26.111 cc altogether.
I could not discover at what rpm the Crecy produced its maximum of 2729 hp, so I assumed it to be at the 2500 rpm that was quoted for its fuel consumption.
This would give 0,0418 hp per cc per 1000 rpm, 26% better than the 0,0332 hp/cc/1000rpm of the (unblown) RSA.
Makes me wonder what the RSA would do at the 100 kPa supercharger boost of the Crecy....
https://ww2aircraft.net/forum/thread...e-crecy.50534/