The Duke Axial Engine

[Garfly]

Bertorelli's take on the subject:

 

 

[facthunter]

yeah.. He's OK. Nev

[F10]

Very interesting Utube clip!...Have some hours on the Da40, diesel was neat, oil just would go very black very quickly after an oil change....at least you could see it easily on the dipstick! FADEC was cool, press one button and hold, the engine automatically runs through a complete power check....Always wondered why motorcycle engines haven’t worked out in RA aircraft...take a Yamaha R1 sport bike engine, 1 litre, pumping out around 140 Hp, will rev for hours at 10 000 RPM, so you should be able to run it a lot longer at a much less stressful RPM? It’s light, small, pretty good on fuel, it seems to be all there.....? Another thing, RPM apparently is a bit of a mystery, to me anyway. Cruise power setting in a Harvard was 20" MAP, 1850 RPM....not much faster than idling RPM! On that radial, it must have been very low stress, that’s why I guess they are still running after 70 odd years? However, some engines don’t like low revs, it’s to do with harmonics, piston weights, crank counter balances, the bottom line, it can be quite complex. So, don’t think running at low RPM is always good....., read what the power tables say in your owners manual! Would be good to hear any other views?

[facthunter]

Radials often have about 3 or more cruise RPMs the low HP ones are at lower revs long range and full throttle position is more efficient with a blower. Fly at full throttle height at low (er) rpms is best. Low rpms less friction.  There are also about 3 NEVER USE rpm ranges due harmonics. Those 4 row corncob motors would be a nightmare that way, They weren't very reliable. Nev

[F10]

On 16/05/2021 at 5:41 PM, spacesailor said:

 

l hear those electric model planes Three blocks away from their flying field.

No sound from the motor, but the scream of the propeller,

& they,r tiny compared to a full size plane,s motor.

 

It's amazing how much noise a propeller makes, when tip speeds approach speed of sound. The buzz you typically hear from a Cessna Centurion on take off for example. I reckon about 70% of the noise generated by a Jetranger helicopter, is from the tail rotor.  

[Garfly]

Some folks are still working to improve - and explain - the rotary: 

 

 

[walrus]

Gadfly, I’ve seen that engine too, but the problem is going to be cooling that rotor when it’s generating 100

+ hp! ….and remember we are talking continuous power here, not an automotive duty cycle.

 

‘’For example a commodore requires just 19hp to keep it rolling at 60mph. The engine is not designed to produce 100

+ hp for most of its life, unlike an aircraft.

 

‘’Marine motors are closest to aircraft duty cycles.

 

 

The Duke and similar variable displacement engines are called “swash plate “ engines that rely on changing the angle of the plate to vary compression and/or displacement.

 

‘’NO ONE has solved the problem of bearing loads and vibration on a swashplate  engine. The main bearing has to support the entire swashplate and piston assembly and ALL the combustion loads - and due to geometry the loads are not spread evenly about the bearing. You can fit the biggest fattest roller or plain bearing you like and it will be pounded into bits in a few hours.

Edited June 10, 2021 by walrus

[danny_galaga]

Yep, no one is probably EVER going to solve problems like that because there's no incentive now for new engine designs. There's no money in it, and there won't bE a sizable advantage over the extra cost of a limited run manufactured engine.

 

Innovation makes us human, but innovating in ICE technology now seems a little futile if for a business proposition. If people innovate for just as a hobby, then that's different. For instance, I'm a bit of a retro games nut. There are people still making games for the Commodore 64 and Atari 2600! Even cartridges. I have a few myself. Some of the games are using new techniques never used back in the day. But in the end it's still old tech. 

Edited June 10, 2021 by danny_galaga

[skippydiesel]

Unfortunately (for me) the future of internal combustion engines looks to be bleak. Limited by the rise of electric motors and battery technology.

[RossK]

19 minutes ago, skippydiesel said:

Unfortunately (for me) the future of internal combustion engines looks to be bleak. Limited by the rise of electric motors and battery technology.

There is some hope Skippy,

Radial

[Garfly]

1 hour ago, skippydiesel said:

Unfortunately (for me) the future of internal combustion engines looks to be bleak. Limited by the rise of electric motors and battery technology.

Anyway, skippytesla also has a nice ring to it.   ;- )