Yamaha RX1 Engines

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Posted (edited)

Teal's aftermarket crankcase cover replacement, which is his "SkyTrax" PSRU adapter, is machined for use exclusively with only the  Rotax "C" gearbox, a unit which was designed by Rotax for their 582 experimental aircraft motor, and also fits other Rotax engines like the 670.  Rotax over-engineered this equipment, so no one really knows what the upper limits of functionality are at this point.  We have read third-hand reports that it has been used on 160HP 2.5 Subaru engines w/o catastrophic failure.  It appears from this info to be robust and able to handle the 120 HP (estimated 7 HP mid-range reduction due to exhaust design) which is what Teal runs his engines at, he reported ~8500 ERPM (See Mohawk's dyno data chart, below).  The RX200 clutches are an unknown, though I have had extensive conversations with the original shop and people who sell them and the design engineer himself does not recommend them for anything more powerful than a 670 Rotax, ~90 HP. 

 

We run our engines with prop pitched to turn 9500 ERPM, 1000 ERPM faster than Teal, and just a hair under 140 HP.  We use the longest exhaust pipes possible for our gyroplane installations, and factory-tuned intake, so I know we are maximizing our HP and are losing very little if any power from what the dyno chart shows, above.  The chart is from the very first RX1 sled ever raced in the manufacturer's sled event in New England, a new sled, during initial 15 hour break-in, on the race-sanctioned dyno bench used for ALL snow machines for the manufacturers annual competition.  This stuff ain't no shade-tree fluff, folks, no smoke gettin blown up anyone's skirts I guarantee you.  We bought all of their Yamaha dyno charts available up to last year including tests for various exhaust and intake variations, so you can take what I tell you to the bank.  Using their data I produced my own Excel graphs.

This is extremely handy data to have, and one can easily extrapolate/ convert thrust test results since a prop is the same thing as a dyno brake - so long as you know what your baseline numbers are in relation to the dyno bench from square one. 

 

Dyno Chart RX1 Mohawk Aero.jpg

Edited by Mohawk Aero

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Posted

Greg mills, some of your information here is not true. I do appreciate you sharing some personal experience with the engine as it may be helpful to others. You kind of make me out like a copy cat and i dont appreciate it. Early on when i first started hearing about the yamaha snowmobile engine i did in fact inquire to you about your adapter kit and after i found out you were using the stock cover with a chain drive bolted on top of it I wasnt interested and came up with my own that completely replaces the stock cover and bolts a gearbox directly to the engine and my intentions were not to mass produce these or even make another but my friends wanted some so i got the cnc program and now i can make them as needed but i in no way have a business doing this as you. After i came up with a good adapter  with some reputation you in fact inquired to me about buying my adapters if i would modify them to accept your chain drives and i told you i wouldnt do that. Over last couple years i have been watching to see if you have completed kit ready to sell and not just acepting deposits. Are you now actually shiping out kits? Because some people on here might be interested in the chain since it brings the prop closer to the top of the engine where it could be easier cowled. I know I sold a adapter kit to Steve Henry of wild west aircraft and he told me he gave you deposit of $1500 for one and that you were still in development but that was about a year ago. Did you get steve out one yet? It would be interesting to see how it works in the highlander. He is currently flying with Skytrax adapter.

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Posted

We can get you a beefed up version of the RX 200 clutch for the YG3 120HP kits for ~$1000, and we have recently started seeing a completely different clutch which is identical on the drum end but which uses a more conventional design for the shoes than the RX 200 and is currently being used on a YG3 gyroplane.  It is ~$600.  

Sprag clutches, when kept properly lubricated, are what has always been used on helicopters, and are by far the most robust and successful in-line clutches ever designed for aircraft use.  They unfortunately got a bad rep when Arrow (Italy) used them on their aircraft/hovercraft 2-stroke engines and failed to engineer an oiler system to the sprag bones and their mating race surface.  They mistakenly thought that oil flinging about inside the gearbox was all that was needed, and completely disregarded mfg specs that called for 2-3 GALLONS of oil to be injected through holes on the race to the dog bone cam teeth.  Once they experienced sprag failure and then figured this problem out they built in an oil pump to take care of the issue.  From then on everything was fine, but the damage to the reputation of using a sprag was done and even to this day it seems difficult to reverse old fears and convince flyers that sprags are a great idea - in spite of the contrary info from all those happy helo manufacturers and their customers. 

Mohawk used the Arrow PSRU with it's internal sprag - a gearbox originally engineered for 200+ HP - with great success and silky smooth engine starts.  That’s what you see in our photos, above.  Unfortunately, that is not a viable option for mass production until we have the time & money to reverse engineer the unit and start fabricating them ourselves, and this is still a ways off, yet.  So we are really happy Teal was able to get the SkyTrax adapter on the market quickly, and get the Yamaha aircraft conversion numbers up and prove the engines in flight. 

What is so different with the Mohawk PSRU adapter is that it is universal and can be used with literally any PSRU while being quite a bit cheaper.  This opens up options for clutches, and we have started working with two different groups who import a gearbox from Belarus (Air Trikes being one) which can be used with a BMW conversion clutch rated at 160HP - which is already far more beefy than the RX200 and yet still only costs roughly the same as the standard RX200. 

We set about, just after completing our first YG4 conversion, designing and fabricating our own YG4 purpose-built PSRU, photos below.  It was intended for FW use where tractor installations would be a direct swap for any Rotax 912/914 build.  Same prop clearances, same cowl dimensions.  As you may notice on Steve's Highlander, he had to sacrifice prop clearance when using a conventional gearbox.  I was working with Steve (Wild West) initially, before Teal eventually sold him an adapter, but he didn't have the seed money and the time to wait for us to complete one of these PSRU's for him.  

I was able to complete one for my own gyroplane, and it has an internal break-away clutch (Same technology as Rotax's break away clutch for their 912/914 gearbox).  This is the only stand-alone PSRU ever built that I am aware of that has this.  (Rotax's 912/914 PSRU is part of the engine, not a stand-alone unit.)

I have successfully flown and tested this PSRU for 30 hours to date.  It is a prototype, and I hope to get it into a production shell in 2017.  It eliminates the need for any expensive (and added weight) adapter, it bolts right up to the stock crankcase cover.  You don't need to remove anything from the end of the motor and thus replace gaskets and seals, and wind up with the potential for oil breather gushers.  I am working on a soft-start sprung system which is aimed at eliminating the hard-banging engine starts which weaken headers and other engine and airframe attachments over time.  This means no clutch, and that is a plus for anyone using a YG4.

YG4's have an internal harmonic damper which Yamaha spent two full years developing.  This damps prop-engine harmonics effectively, so the YG4 is far superior in this respect to any YG3. 

Mohawk also offers PSRU adapters ready to order which bolt up to the YG4 EFI engines, 2006 - present.  As YG4 NA's become scarcer, this is an important niche we fill.   

I saw this at a shop I went to years ago, and I find it applies in any case. 

"There is cheap, fast, and good quality.  We do any two.  You can have cheap and fast, but it won't be good.  You can have cheap and good, but it won't be fast.  You can have fast and good, but it won't be cheap."  

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Posted

This is the Mohawk Silent Drive PSRU, direct bolt-on, no changes to factory crankcase cover, no adapter.  It is a bench-built unit using Hy-Vo chain technology and comes in 2.72:1 with break-away prop strike protection clutch, and 2.83:1 with conventional gear.  The ears on top are for the rotor pre-rotator which is gyroplane specific and is eliminated on other applications.   

There are some exciting things being done with Yamaha engines these days, and other options available. 

For the inside poop, tuning tips and tricks, and updates to what's happenin', feel free to hit me up any time. 

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Posted (edited)

Greg mills, some of your information here is not true. I do appreciate you sharing some personal experience with the engine as it may be helpful to others. You kind of make me out like a copy cat and i dont appreciate it. Early on when i first started hearing about the yamaha snowmobile engine i did in fact inquire to you about your adapter kit and after i found out you were using the stock cover with a chain drive bolted on top of it I wasnt interested and came up with my own that completely replaces the stock cover and bolts a gearbox directly to the engine and my intentions were not to mass produce these or even make another but my friends wanted some so i got the cnc program and now i can make them as needed but i in no way have a business doing this as you. After i came up with a good adapter  with some reputation you in fact inquired to me about buying my adapters if i would modify them to accept your chain drives and i told you i wouldnt do that. Over last couple years i have been watching to see if you have completed kit ready to sell and not just acepting deposits. Are you now actually shiping out kits? Because some people on here might be interested in the chain since it brings the prop closer to the top of the engine where it could be easier cowled. I know I sold a adapter kit to Steve Henry of wild west aircraft and he told me he gave you deposit of $1500 for one and that you were still in development but that was about a year ago. Did you get steve out one yet? It would be interesting to see how it works in the highlander. He is currently flying with Skytrax adapter.

Steve saw your post, quoted, and called me this afternoon to say he has never said anything derogatory about me nor our business dealings together in any public forum, nor would he ever.  Steve and I have always had an understanding, a friendly relationship, and we continue to work together to develop both Wild West's program and Mohawk Aero's.  He kindly understands the many obstacles and hurdles I have encountered and faced down both personally and professionally since we first started down the path of developing a purpose-built PSRU for the YG4, and we continue, to this very day, to work together to put more Yamaha YG4's in the air. 

(Let's hope this momentary lapse of judgement in what is fair and what is dirty laundry doesn't spoil the thread.  Anyone who wants to chat with Steve on this, please feel free to hit him up.) 

As mentioned, I joined this thread to answer those questions asked here that had thus far gone unanswered related to YG4 electronics and reliability.  It seemed to me that no one had the answers but me, and it also seemed obvious to me that a proper accounting of the history of the YG4 aircraft conversions was in order.  Perhaps my narrative didn't come off in an entirely flattering way to Teal, but that can happen when you leave the door open for someone else to fill in the gaps.  I continued and expanded on that, and provided other fun stuff, photos and facts related to flying with Yamaha power. 

I've been getting an uptick on inquiries on my products lately, and most guys mention Teal's equipment at some point.  I look on all of this like shoe stores in a mall.  If there is only one shoe store, no one is going shoe shopping at that mall.  If there are five shoe stores at another mall, all the girls are going to go shopping there and all the stores will benefit from the increased traffic in the end.  

Teal's got a great strategy which is working well.  I have another one which is also provides a great product for those who wish to (A) use something other than a Rotax PSRU and RX200 clutch, or (B) install a YG4 FI instead of a YG4 NA. 

Steve's YG4 FI adapter will be shipped just as soon as we can decide on which PSRU to use next.  SO many choices.  Compact Radial's internally clutched MZ202?  Tango's external clutch on a Belarus shorty shaft?  Rotax's C box with an RX200 shaft clutch?  Air Trike's SPG4 with a BMW conversion clutch?  Auto Power's PSRU with an external sprag clutch?  How about a reconditioned Arrow PSRU with an internal sprag? 

Anyone have any other suggestions?  We're open to other options and suggestions as to where to look for gearboxes. 

Onwards and upwards :) 

 

 

   

 

 

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Silent Drive (768x1024).jpg

Edited by Mohawk Aero

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Posted

just some more photos to look at...compare the Mohawk Silent Drive to the Arrow gearbox with the Mohawk Universal Adapter.  The Silent Drive saves 3-4 inches in length, and allows more flexibility in designing how high up you place the prop for clearances. 

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Posted

Greg, thanks for posting im sure everyone loves the pics and the info. I cant wait to see steve's apex engine adapter he gets from you. Heck i might buy one from you if steves works out. i dont currently have plans to build one for the apex engine if your works good.

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Posted (edited)

Thanks so much to both of you guys for all the info you have put up here... and for all the WORK you have done to bring this power option to fruition! 

I recently picked up both a Kitfox 5 (subaru powered) and a 2005 Yamaha RX-1.  My plan is to ride the yamaha as a snowmobile this winter to gain some familiarity and confidence in the motor, and also to fly the airplane with the e81 in order to asses it's viability. 

Every post you guys put up, and every example of another successful conversion helps motivate me to make the switch! 

The info that you post on obstacles that you and others encounter. .. and the solutions that are found to overcome them are equally important because we all know that those are a natural part of the process.

Confidence is gained when we see these "teething" issues ironed out. 

And on that note, It would be of great benefit to all if there could be a blog page out there for the Yamaha Aero conversion.  A "one stop" headquarters with links to every outlet of information:  Conversion vendors,  individual's build and flying pages (Steve Henry, marshawk, and others), and threads like this.

Thanks again!

Brett

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Edited by MN Kitfox 2
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Posted (edited)

Brett

On your suggestion, I have started the "Yamaha Aircraft Engines" blog on Facebook, https://www.facebook.com/groups/1251356951570824/

please join.  I have started adding photos from own files, including the only ones I have of Teal's first YG4 project, his trike. 

If any vendor wants to add a company logo to the top banner, please send your artwork to INFO@MohawkAeroCraft.com

 

Edited by Mohawk Aero

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Posted

Brett or Teal,we are just working on the motor mount for the RX1 and just wondering how to get the right angle on the engine since it sits tilted. We are thinking  we need to set  the float bowls level but would like to here from one of you guys before we go too far,

 

Thanks Willis

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Posted

I would aim for level on the float bowl mounting surface but if you wanted to lean it either way within 15 degrees to optain a particular engine position or thrust line you wouldnt affect anything. I have ran the engine on the run stand in all kinds of positions to see if it affected fuel flow or overflowage and it didnt miss a lick or drain fuel. On the snow machines I would imagine they are put in more extreme positions than most of us would.

 

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Posted (edited)

There is a RX1 with 2500 miles on craigslist in mass. For $1295 obo.

Edited by Teal
Fix grammar

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Posted (edited)

Brett or Teal,we are just working on the motor mount for the RX1 and just wondering how to get the right angle on the engine since it sits tilted. We are thinking  we need to set  the float bowls level but would like to here from one of you guys before we go too far,

 

Thanks Willis

After takimg a closer look at the snowmobile, l noticed that the carbs are set in there at an angle, tilted back approx 15 or 20 degrees ("back" meaning - if your mouth is the carb intake, tilt your head back 15 or 20 deg).  You can kinda see it in the pic of a turboed snowmo below.

So it might be best to match that angle as a target, but you should have some room to play with (+/- 15 degrees for sure).

And if you get a chance, PLEASE do start a "build" thread here with lots of pictures of the yamaha install!  So far, all that us fixed wing tractor guys have is a few shots of Steve's Highlander.

Looking forward to seeing your progress! 

yamaha-img17.jpg

Edited by MN Kitfox 2
Closer inspection of snowmobile
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Posted

Oh, and Teal, did you buy a kitfox earlier this year to convert to and test the Yamaha?

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Im not to sure I can do a build thread but will post pictures and try and answer any questions you have ,im sure Teal or Brett will be away more qualified . Im not sure how much my motor mount will help , the fat avid has 10 firewall attach points , what we did so far is run 1 1/2" 4130 pipe around the engine for the main mount and its bolted to two center motor mounts . We making 4 secondary braces to hold the engine in place then do the exhaust and air box etc and then see were we can run the last braces, thats are plan subject to change at the drop of a beer :BC:

We just  got started but heres what we have so far

RX1.JPG

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Posted

Looking good Willis!  What is the rough measurement of your firewall?  It looks like you have a bit more room to work with than my kitfox 5 does.

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I am using a kitfox 5 cowl so you will have the same amount of room, its a tiny beast of a motor.

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Oh, and Teal, did you buy a kitfox earlier this year to convert to and test the Yamaha?

yes, I did but soon after a purchased the kitfox a Avid came up for sale that needed an engine. So I decided to do the engine install in the Avid. The kitfox does prrtty good with 80hp 912 thats in it so im considering selling the kitfox now and focusing my efforts on the avid

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Posted

Oh, and Teal, did you buy a kitfox earlier this year to convert to and test the Yamaha?

yes, I did but soon after a purchased the kitfox a Avid came up for sale that needed an engine. So I decided to do the engine install in the Avid. The kitfox does prrtty good with 80hp 912 thats in it so im considering selling the kitfox now and focusing my efforts on the avid

Sounds like a good choice.  And i will be in AZ all of Jan 2017.  Hope to meet up with you sometime.  Will PM you when it gets closer.

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Posted

Steve Henry won the STOL drags competition  with his RX1 highlander this weekend. beating out a carbon cub in the final round.

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Posted

without pics it didn't happen damnit!  :lol:  I heard the news a couple hours ago.  Joey spent a couple hours talking to Steve and he really seems to like this engine!

 

:BC:

 

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Posted

I am really starting to think this may be a great engine for the Amphib project...

:BC:

 

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Posted (edited)

I watched Steve Henry fly quite a bit this weekend at the High Sierra Fly-in. He flew it all the way down from Idaho. He recently regeared to a 3:1 and he lost some static RPM with prince prop he was running so he was down about 15hp. By far the most impressive LSA I've seen. He was spanking Carbon Cubs on takeoff yesterday and he can climb sustained at about a 60 degree angle without doing a zoom climb. Thing pulls REALLY hard. He's flying it all the way to Copperstate from Idaho next weekend.

Edited by C5Engineer

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Posted

Akflyer sold more people on lotus floats (with his videos) than the sales department probably ever did!

Might be the same for Steve Henry with the Yamaha Genesis conversion :)

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Joey,  do you know if there are any videos of Steve Henry's flying this weekend?  JImChuk

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