Eggenfellner

[Mike S]

Originally Posted by prkaye

Naive question here - these engines are often under-powered and need a CS prop. ?

Phil, sorry for the editing job, but you seem to have a bit of a misunderstanding going on here. C/S props are not a band aid for underpowered/low powered engines, in fact you dont even find them on most low HP certified engines. C/S props are a way of expanding the range of optimum efficiency points (from the one that is available) of a fixed prop, to a larger range.

To put it into a form that is easier to understand, imagine driving a car, standard trans, only in first gear. Speed control is by throttle only. Sthis is like a climb prop in an A/C. Now, same car, but use high gear only-----Cruise prop. O.K., now same car, only with a 6 speed auto trans----------constant speed prop. Over simplified to be sure, but the best explination I can come up with.

There is another Subie guy out there, in your neck of the woods, might be worth lookin into http://homepage.mac.com/airryder/Menu11.html My only knowledge of his work is back in my Dragonfly days, but he had the best of the Subie bunch for that application.

Good Luck.
Mike

[prkaye]

Now I get it So you want a PSRU with a high ratio, so the engine is turning as fast as possible while keeping the prop speed down to a reasonable level.
So why not just use as aggressive a PSRU as possible (i.e. with a really high ratio)? Is it because of the stresses imposed on a PSRU with a really high ratio?

[prkaye]

Thanks Mike!
It looks like that guy is in Alberta... not exactly my neck of the woods... actually probably not much farther from the than California is

[cjensen]

Originally Posted by prkaye

Now I get it So you want a PSRU with a high ratio, so the engine is turning as fast as possible while keeping the prop speed down to a reasonable level.
So why not just use as aggressive a PSRU as possible (i.e. with a really high ratio)? Is it because of the stresses imposed on a PSRU with a really high ratio?

It depends on the engine, and where the max power is being generated. For the H-6, 200hp comes at 5400rpm, so the reduction of 2.02:1 brings just under 2700 to the prop.

For a rotary like the Powersport, they use 2.29:1 because their max power of 215hp comes at 6000 engine rpm to give 2620 at the prop.

[Rotary10-RV]

Originally Posted by cjensen

It depends on the engine, and where the max power is being generated. For the H-6, 200hp comes at 5400rpm, so the reduction of 2.02:1 brings just under 2700 to the prop.

For a rotary like the Powersport, they use 2.29:1 because their max power of 215hp comes at 6000 engine rpm to give 2620 at the prop.

Quite correct Chad,
Also many of the auto conversions are lacking because the engine doesn't like to "live" at the highest RPMs. Some will run high RPMs very well though. If your engine will survive a high continous RPM, then a larger gear reduction is a good idea. In fact the rotaries have been going to a higher reduction ratio, usually around 2.83:1. This allows higher engine rpms and more power. The rotary is tolerant of continious high-RPM use, in fact 6000 RPM may be its best operating RPM. I won't bore you with the details here. Tracy Crook has had great success running a fixed pitch prop. Winning the Sun 'n Fun 100 in his displacement catagory on several occasions. You need to match your reduction to the intended RPMs. If your engine produces the design HP at that RPM a geared reduction drive wouldn't lose more than a max of 5%. Many are better than that. Fixed pitch has the same difficulties on the geared drive as it does on a direct drive. Cruise or speed or climb take your pick. Many systems are going to slightly larger prop at a lower speed for efficiency. This would make a higher reduction a good idea also.
Bill Jepson

[Deuskid]

Originally Posted by Rotary10-RV

Quite correct Chad,
Also many of the auto conversions are lacking because the engine doesn't like to "live" at the highest RPMs. Some will run high RPMs very well though. If your engine will survive a high continous RPM, then a larger gear reduction is a good idea. In fact the rotaries have been going to a higher reduction ratio, usually around 2.83:1. This allows higher engine rpms and more power. The rotary is tolerant of continious high-RPM use, in fact 6000 RPM may be its best operating RPM. I won't bore you with the details here. Tracy Crook has had great success running a fixed pitch prop. Winning the Sun 'n Fun 100 in his displacement catagory on several occasions. You need to match your reduction to the intended RPMs. If your engine produces the design HP at that RPM a geared reduction drive wouldn't lose more than a max of 5%. Many are better than that. Fixed pitch has the same difficulties on the geared drive as it does on a direct drive. Cruise or speed or climb take your pick. Many systems are going to slightly larger prop at a lower speed for efficiency. This would make a higher reduction a good idea also.
Bill Jepson

I hope this isn't perceived as a hyjack or flamable event but if torque is a critical element and if rpms are a critical element wouldn't an auto turbo-diesel be ideal? Peak torque at about 2700 rpms, burns jet-A, can be used as direct drive... I know there are aviation diesels that so far most fall on their face but it seems that a couple of european diesels [toyota d4d or the mitusbushi] would lend themselves to conversion without a PRSU and allow for single lever engine control. I've owned several VW turbo auto diesels and am impressed with them.

Unfortunately I lack the background to do a conversion [and the small diesels in the states suck for the time being because of EPA foolishness and high sulpher has only recently been eleminated on our roads].

I know diesels weigh a bit more but with increase fuel saving and no PRSU needed some of that weight can be 'made up'.

tho if I f I build/buy I'll probably go Lyco or jabru... tried and true technology...

I don't have the skill set or time to experiment

John

[DGlaeser]

The folks at Delta Hawk agree with you (that diesels are the ideal solution) Diesels have come a long way in cars, so one of these days someone will put one in a plane I'm sure. In fact Subaru is apparently coming out with a diesel, so the Eggenfeller Yahoo forum is speculating that Jan will have a diesel offering someday...

[pierre smith]

Originally Posted by Deuskid

I know diesels weigh a bit more but with increase fuel saving and no PRSU needed some of that weight can be 'made up'.



I don't have the skill set or time to experiment

John

John,
Diesels have tremendously hard power pulses because of their very high compression ratios, some well over 20:1. These power strokes raise holy h*** with prop bolts, laminations (on composites), etc.

Therefore, a PSRU connected to an energy absorbing, cushioned elastomeric drive seems an almost must. MHO
Regards,

[Rotary10-RV]

Originally Posted by pierre smith

John,
Diesels have tremendously hard power pulses because of their very high compression ratios, some well over 20:1. These power strokes raise holy h*** with prop bolts, laminations (on composites), etc.

Therefore, a PSRU connected to an energy absorbing, cushioned elastomeric drive seems an almost must. MHO
Regards,

Pierre,
That hardly seems a bad idea with any engine. That aside most of the diesels being developed for aircraft are 2 cycles. (deltahawk, Whilch) which have twice as many, but smaller power impulses. For the car questions, the Thilert certified engine is converted from a Benz auto diesel.
Bill Jepson

[rv6ejguy]

Robert Paisley thrilled the crowd with the sights and sounds of his Eggenfellner H6 powered RV7 last weekend at Copperstate with some high powered fly bys. Jan was on hand as well to answer questions from hundreds of interested people gathered around. Robert is testing some new spec parts now and is seeing 8.5 gallons/ hr. at 185 mph cruise. He does not yet have the new redrive or the carbon fiber prop so even better performance and lower weight seems to be in the future for these engines. Jan padded his order book some more at the event.

Jan is currently testing the new redrive in his -6 in Florida.