Rotaries, and a vent.

Is there a troll free forum where good dialog and information exists about rotaries? I am looking for specific wet weights FFW of the 13B packages.

Here's the vent part:

WARNING: if you are loosening up your typing fingers to reply with anything other than what I just asked... save your energy. I DON'T CARE how superior the traditional air cooled engine you prefer is. I also know what I am in for IF *I* DECIDE to choose an alternative.

I am NOT looking for cheaper, faster, lighter, higher resale, smoother and more efficient... Nor is anyone telling me an alternative engine will give me all these things. A winner in one or two of these categories may just be enough for me to CHOOSE an alternative.

This site is a Godsend of information on building a Vans aircraft and it is the ONLY reason I chose the RV7a over a Lancair Legacy FG, but I'm really tired of reading stuff like "Are liquid cooled Aircraft Engines Possible"?

I actually thought the author just might be ignorant (not meant as an insult) about liquid cooling (past and present), but it didn't take long to realize there was an agenda there.

I also initially thought that there was a forum for that junk --> "Never Ending Debates"... ???

Yeah, Yeah... I know the old guard will say they are just trying to ensure that newbs are fully informed about the potential "issues" with alternatives. Bull! Will the junk stop if there is a polite and neutral sticky up here warning us that alternative engines are for the more advanced builder who understands what they are getting into?? Then maybe the junk can be moved to the debate forum???

Anyhow, some great sources of information on alternative engines are being driven into silence because of constant banter from a few individuals... There are also some great sources who will not participate here anymore. What a shame.

I'm sorry to rant like this. I really learn from the things that Ross, Todd, DanH, and others post... but there are about 5 users who shall remain nameless that even a newbie like me can see right through. Their only goal is to stir the pot. Maybe they consider the propulsion that their BS and hot air could create as some form of alternative engine...

I mean no disrespect to anyone, but I am not going with a taildragger and may not go with a lycoming... That's 1 small strike and 1 BIG strike against me with a certain crowd here... That's why I prefer to lurk.

Now, if you still have the need to RESPECTFULLY question me or my desire to explore the option of an alternative engine, please do it with a civilized PM and we can chat.

Anyhow, where is the fountain of collective knowledge on rotaries that drive a non-metal prop via a PSRU??

Thanks!

DR

So, tell us how you really feel.

Well said, I also get tired of some of the childish backbiting and snide comments on here.

Occasionally I do something about it even.

Your comment about the knowledge gained from Ross, Todd, Dan and others is right on target. Another good source of info is George/GMCJET, and hopefully people find my contributions helpfull occasionally.

Personally, I love the Wankle/Mazda engine. I had a slightly heated up 13b in a old RX7, originally came with a 12a. I visited Lou Ross a couple of times to look at his PSRU for the engine, had thoughts of designing a plane behind one. I was thinking along the lines of up-scaling an aerobatic platform from the radio control world, with the small frontal profile of the Mazda/Ross, and composite construction, ----------------oh well, maybe in my next life.

Hopefully those who join in here will keep it to business.

I tried, really I tried...........

http://www.rotaryaviation.com/

Tracy has the most informative site out there as far as real world experience and a description of what to expect and how to accomplish what you want.

Very few rotary experts on this forum....a number of rotary advocates, but based on your opening post, I would suggest that RWS would be your best bet for real information.

Tracy is probably the best source for rotary knowledge. He is also the one who built my engine controller. He has been flying his plane for quite awhile now.

The Flyrotary list is the best place to go for the info you need. Tracy participate's regularly on that list.

http://www.flyrotary.com/

Subscribe here- http://lancaironline.net/lists/

The Flyrotary list is an email list, but very active. There's several different "schools" inside the rotary world as well...Paul Lamar, Dave Atkins, and Tracy Crook all have different views as to what works best. Paul has a list as well, but it's not as active as the Flyrotary list. http://www.rotaryeng.net/

Hope that helps, if you haven't already been to those sites...

Tracy Crook has had far more success and experience in this field than the others mentioned here and he is respected by almost everyone. Paul Lamar has never flown one of his creations so I consider his views theoretical at best and sometimes complete nonsense.

Another super savvy Wankel head is Paul Yaw- one of the smartest engine guys I know. http://www.yawpower.com/

Your concise summation of the alt engine debate had me smiling. Thanks.

Ross,
Thanks for the Yawpower site- it IS very good.

I agree with the earlier posts- the best basic data comes from Tracy Crook's site- it is a must read and is the best source for many parts that you will need. Be sure to buy Tracy's booklet "Aviators guide to Mazda Rotary conversion".

Tracy's strength is that he is practical and experienced, but that practicality is possibly also his weakness. My concern with Tracy's approach is that he is a cheapskate! He has documented a bunch of triumphs and a few missteps over time, but, he presents his experiences "right from the hip" that we can all learn from. He and Laura are really nice people and great to work with- a lot like Van. Tracy has advanced the Rotary aircraft knowledge base more than anyone else to date.

I personally think that Paul Lamar has a better technical grip on cooling, intake, and engine mount design than Tracy- you should at least be familiar with both sources before you make choices. PL's site is particularly good for historical and test data concerning rotaries, but he does occasionally get sidetracked into interesting theory not applicable to our needs. Paul has not personally flown with a rotary, but many others have who contribute regularly to his newsletter daily. From what Ive seen, PL's list is a bit more active than Tracy's, but not always as applicable. PL knows rotaries and aerodynamics- he references and relies heavily on technical test data, often from Mazda and NASA, far more than Tracy does.

There are a lot of information sources from various RX7/8 auto enthusiasts that pertain largely to racing. Id also recommend checking out the Mazdatrix website.

ANOTHER GOOD SOURCE

DR,
You might want to check the Mistral site. www.mistralengines.com You might have to poke around a bit but they have a good (and very honest) graph of the WT/HP of various rotaries and Lyc or Conti weights. Their numbers include the weight of their own PSRU (an excellent one BTW) at 47 pounds. The 13B compares well with an IO-360. At or around 200 HP. The Mistral rotary uses the standard iron housings in the comparisons. Future rotaries using aluminum side plates and housings will be about 20 pounds lighter. The 20B compares very favorably with the O and IO-540's coming in about 20-40 pounds lighter for the same HP. If you want to know for sure I've got a 20B sitting on a stand in my shop.
Bill Jepson
PS. the weights chart in under general info on the site. Click on "technology" then click on the picture of the G190 engine headed "general overview" The chart is about 1/2 way down on the right.

There is some stuff of interest on PL's site but when it comes to talking about this subject and doing it, these two aspects are worlds apart.

PL's abrasive personality and closed minded, know it all attitude turned me off him years ago as it has many others flying Wankels.

By all means look at any info out there you can but take the theoretical stuff with a grain of salt. The stuff that is flying successfully is far more useful and important IMO.

Holy Cow

Wow, I give it a little time... and whaddayaknow!

Excellent posts! I have found a couple of those sites about the rotaries, but there were I few that I had not stumbled across.. I will spend some time soaking them in!

Also, you have no idea how nice it is to NOT see posts lambasting my search for info.... I truly appreciate that.

RotaryRV10 - Do you have the Mistral product??

Also, why don't some of you really smart guys design us a bulletproof PSRU??? I'll sign a release of liability and pitch in some cash... (you listening Ross and DanH??)

Thanks!

DR

Roddzilla said:

Also, why don't some of you really smart guys design us a bulletproof PSRU??? I'll sign a release of liability and pitch in some cash... (you listening Ross and DanH??)

Thanks!

DR

Click to expand...

I'd love to but I'm too busy with other aviation projects currently plus the RV10 and of course posting here.

Roddzilla said:

Also, why don't some of you really smart guys design us a bulletproof PSRU??? I'll sign a release of liability and pitch in some cash... (you listening Ross and DanH??)

Thanks!

DR

Click to expand...

Molt Taylor used a device in the drive of some of his designs, used a wavy disc in a toroid full of steel balls, IIRC. Absorbed the TV and allowed him to use long driveshaft to a rear prop.

Unfortunatly, I dont remember the name of it.

BUT, I'll bet someone out there in VAF land will.

I wonder if a similar device would help with the PSRU TV issue???

Flexidyne

Molt used the Flexidyne dry fluid coupling concept.

http://www.dodge-pt.com/pdf/brochures/pt_components/dmr_1513.pdf

Bill, thanks, yes that is what I was thinking of.

From the things I have read/observed both on this forum, and elsewhere, it sounds like one of these units could be helpful in controlling unwanted vibrations in a PSRU.

Hopefully Dan Horton will jump in here--------------he seems to be the resident expert in the field of TV.

Unless I missed something, Tracy's PSRU IS bulletproof and represents the state of the art as far as affordable units are concerned- it has not failed to date and it is designed specifically for the Rotary engine. Why is another design needed?

I'm gonna jump in here a moment and then go away.

I appreciate all the nice comments about my writing on torsional issues, but I am not an expert.

I'm just a homebuilder like most of you. Back in 1998 I found myself with a Gold Lindy for an airplane I was afraid to fly (or at least too nervous to have fun). The purchased redrive I was using was a torsional and mechanical disaster. Those of you who frequented the old Airsoob group will remember.

I was lucky enough to find an excellent mentor (and great friend to this day); Steve Crow, Caltech PhD, former professor and dean, and all-round very smart guy. Steve had a project of his own, our interests were complimentary, so we worked together on both. He got data and I got an education. More important, I got a whole new perspective. I'd been a mechanical crazy all my life, but too much was based on the classic TLAR approach. Steve showed me I was capable of real engineering, despite the limitations of an Alabama high school diploma. No more TLAR for me. For someone as deeply wrapped in experimental airplanes as I am, it was a life-changing experience. Still, I'm not a pro, and I try to keep my limitations in mind. You should too.

Torsional vibration is a tough subject when taken in depth. The most complete work on the subject was published in 1940, Ker Wilson's "Practical Solutions to Torsional Vibration Problems". Practical Solutions is a three-volume set that stacks up about 9 inches high. I'd love to have a set of my own, if anyone knows of one for sale. Then maybe I'd be an expert after a few years to digest it all. <g>

The advantage that Tracy has with most of his drives is that they are used primarily on one engine- 13B Mazda and with props generally in the same range with regards to moments of inertia. The fact that many are flying and have accumulated many thousands of hours collectively PROBABLY means that there are no serious torsional vibration concerns with this package.

However putting the same drive on say a 4 or 6 cylinder Subaru throws that premise out the window as these are very different engines. There may be no issues again with the Subaru or there may be. There is not enough time on this combo to draw any conclusions. If Tracy has run the calcs or done actual instrumented TV testing, then we'd have more confidence that his drive would also be safe on various Subaru engines.

What we are saying here is not to assume that there are no hidden TV issues on any drive that has not been tested for TV. We are not singling out any one drive. TV is insidious and can cause both slow and instantaneous failures to engines, PSRUs and propeller systems. Many people have never heard of torsional vibration and have little appreciation of it.

If you are looking for a good track record on Wankel PSRUs, Tracy is at the top of the list along with Powersport. Tracy's drives have a lot more flight time, Powersport's has had detailed TV testing done. I'd feel pretty confident using either design on a 13B powered aircraft.

Drives that are fitted to a variety of different engines like the Marcotte that I use are more of an unknown quantity.

My apologies.

Wow Dan, thanks for the honesty. I have been reading your posts on the TV subject for quite a while, and just assumed-----yes, I know what the word breaks down to-------you worked in the field.

Sorry to have put you on the spot like I did.

Ross,
What you say is true (also applies to the Eggenfellner drive, doesn't it?) but in addition, I believe there is an inherent strength and weight advantage with a planetary gear set over spur gears or belts- they have a lot more contact surface between the 6 driven/drive gears and torque is distributed concentrically around the shafts which likely reduces some of the torsional vibration.

You might be interested in the following from Tracy's website:

"Looking for a redrive for an alternative engine but NOT a rotary? We also sell the drive WITHOUT the adaptor plate. Several builders have fabricated their own plate to allow them to use the RWS drive on a non-rotary powered plane. Here is a photo of Troy Wright's RD-1C drive installed on his Ford V-6 engine for a Fokker DVii plane. Contact us if you want a quotation for a drive minus the adaptor plate."

It's probably relatively easy to match up the flywheel to the PRSU input drive as long as it is centered, and, because it uses steel plates instead of a bell housing, you can likely drill your own mounting holes to match your engine.

Mike S said:

Molt Taylor used a device in the drive of some of his designs, used a wavy disc in a toroid full of steel balls, IIRC. Absorbed the TV and allowed him to use long driveshaft to a rear prop.

Unfortunatly, I dont remember the name of it.

BUT, I'll bet someone out there in VAF land will.

I wonder if a similar device would help with the PSRU TV issue???

Click to expand...

Mike,

The ramp and ball system you're talking about is a impact protection cam. It's used in lots of motorcycles with shaft drive as a shock absorber. It isn't as good with TV though. The truth is that because this device is not a damper it can actually make the tortional vibration worse. It is another spring device designed to lessen impact on the gears. The link to the device used by Molt Taylor is an example of a true dampening device, and it looks good. The engineering problem is always to find the smallest, lightest and cheapest way to do it. You also have to design within the dampeners capacity, and as we slide up the HP scale it gets harder and harder not to just blow things up!
Several people are using the final drive for a helicopter (Bell 47) designed to handle over 1000HP. The only problem there is cost!
I'm not a Mistral customer at present, but they will sell some parts and I may eventually buy their PSRU. The Mistral PSRU is a purpose built design. It uses straight cut (spur) gears throughout. The biggest advantage is that the PRSU is designed to handle a CS prop from the start. It isn't cheap at around $6800 last time I checked, but the ability to use a standard CS instead of a super-expensive electric may make it worth it.
Bill Jepson

PS... DODGE® FLEXIDYNE® is a dry fluid drive that provides smooth, controlled
acceleration with a reduced current draw. Because of its unique concept in
principle and design, it can handle difficult drive problems and is compatible
with standard NEMA Design B motors commonly used in industry. It is not,
however, recommended for use with variable-speed drives, internal combustion
engines, or multiple-speed electric motors.
I've included this from the Dodge PDF on the Flexidyne coupling as an FYI. These manufacturers understand how tough a job this can be.
Bill

rtry9a said:

Ross,
What you say is true (also applies to the Eggenfellner drive, doesn't it?) but in addition, I believe there is an inherent strength and weight advantage with a planetary gear set over spur gears or belts- they have a lot more contact surface between the 6 driven/drive gears and torque is distributed concentrically around the shafts which likely reduces some of the torsional vibration.

It's probably relatively easy to match up the flywheel to the PRSU input drive as long as it is centered, and, because it uses steel plates instead of a bell housing, you can likely drill your own mounting holes to match your engine.

Click to expand...

Yes, this reasoning also applies to Eggenfellner's gearboxes and we have a massive thread now on that. Egg does not sell to anyone not using his engines however.

The planetary drive can be made very strong if enough pinions are used. The newer Ford 6 pinion carrier is much stronger than the 4 pinion one. Any drive system can be made to handle a lot of power. Aero engines in the 4000hp range have used both planetary and spur type gearboxes successfully in racing. The planetary setup is small and light but has two two things against it as used with the Ford gears- it offers zero thrust line offset so limits which engines fit under the cowling of which aircraft, especially those with top induction. Secondly is reverses prop direction possibly limiting prop choices in the higher hp ranges.

The Ross drives used the same early planetary gear set and were not good boxes by any measure with several design and machining problems. Once corrected, many people have reported good service with them. Any box design needs to be right irregardless of gear type or it can fail.

I know that one of Tracy's gearboxes has been applied to a gas turbine engine and despite no TV, it did not last even one hour (bearing issues). Testing on different applications is always prudent.

Good point on the thrust line- I'd never thought much about that "problem" since it is not relevant to rotary engines (intakes on the side, though it is common to wrap intake tubes over the top of the engine).

"Secondly is reverses prop direction possibly limiting prop choices in the higher hp ranges"

Not necessarily true- depends on how you set up the planetary gearset. Tracys RD-1C has normal rotation w/ 2.85 ratio and the -1B has 2.187 ratio w/reverse rotation. Both use the same 6-gear planetary set from Ford.

rtry9a said:

"Secondly is reverses prop direction possibly limiting prop choices in the higher hp ranges"

Not necessarily true- depends on how you set up the planetary gearset. Tracys RD-1C has normal rotation w/ 2.85 ratio and the -1B has 2.187 ratio w/reverse rotation. Both use the same 6-gear planetary set from Ford.

Click to expand...

Aha. I did not know that. I stand corrected.

The thrust line thing is a big deal on most piston engines including Subarus on airframes designed for opposed engines. Eggenfellner has to change the water manifold and fab a lower profile intake to get his non-offset drive setups to fit under most cowlings and many other Sube guys have had to do similar things with other planetary drives like Ross, RWS and the Geared Air Power units.

This can be a lot of work for non-fabricator types. Offset drives like RFI, Marcotte, Auto Flight and EPI give these users other options.

rv6ejguy said:

Aha. I did not know that. I stand corrected.

The thrust line thing is a big deal on most piston engines including Subarus on airframes designed for opposed engines. Eggenfellner has to change the water manifold and fab a lower profile intake to get his non-offset drive setups to fit under most cowlings and many other Sube guys have had to do similar things with other planetary drives like Ross, RWS and the Geared Air Power units.

This can be a lot of work for non-fabricator types. Offset drives like RFI, Marcotte, Auto Flight and EPI give these users other options.

Click to expand...

Ross,
The zero thrust line offset can be a problem for rotaries too. Most of the guys like to wrap the intakes over the top of the engine. This puts the intakes away from the exhaust in a cooler area. You must design very carefully to fit the tubes in on a "over the top" intake. You can do it, since you need only pass the actual intake tubes over. The max area allows only about 2-1/2" though. The Powersport engine used a internal gear set-up just like the Marcotte, but straight cut rather than helical. Properly done this is a very good way to do things. I like the small offset offered and the rotation comes out "right". The way the planetary gearset works is that in the higher gear ratio (lower numerically) the power is taken from the ring gear and the planets are fixed. In the 2.83:1 ratio box the same gears are used but the power is taken from the planet carrier and the ring gear is fixed. This setup allows the standard rotation, and has really started to takeover on the rotary since they love to rev. Both Tracy's RD-1C and the Mistral planetary hold the ring gear and take power from the planet carrier giving standard rotation from the rotary. Both of these planetaries have zero thrustline offset though. Not impossible, but you must plan carefully.
Bill Jepson