Considering the Rotax 915

C. Beaty

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Back in the good old days when Rotax was a small, struggling, hole in the wall Austrian engine builder, I purchased my first Rotax engine, a 2-stroke with propeller redrive for ~$500.

Then, along comes Canadian mega conglomerate Bombardier, purchasing Rotax lock, stock and barrel and the rest is history.
 

NoWingsAttached

Unobtainium Member
Joined
May 21, 2006
Messages
4,776
Location
Columbia, SC
Aircraft
Air Command Tandem w/ Arrow 100hp; GyroBee w/ Hirth 65hp; Air Command Tandem w/ Yamaha 150hp
Total Flight Time
>350
2014 Yamaha Motor Co. Sales
Yen
$1,521,000,000,000​
USD
$14,349,056,603.77​
Units Sold, @ $14k ea
1,024,933​
Daily Production
2,808​
hourly prod
117​
per min
2​
Gerg dropped a decimal, and pulled Bavaria out of his butt. Thanks for keeping me honest, politely.

Another correction: https://global.yamaha-motor.com/about/history/timeline/ First Yamaha motorcycle mounted 4-stroke was 1970, 19 years before Rotax's first 4-stroke. I seem to have juxtaposed diesel introduction in 1976, and then typo'd 9 for 6 while using the math for '76.

Keeping in mind that list price on a 2019 4-stroke Yamaha Zuma is only $3000, and I was using the price based on a top-of the line R1 or sled, it would be fair to say the average price is more like $8000 per unit.

Units Sold, @ $8k ea ave.
1,793,632​
Daily Production
4,914​
hourly prod
205​
per min
3​

Someone posted that Rotax sold 9,000,000 engines as of 2018. The company was founded in 1920, so it took 98 years to accomplish this. Yamaha does it about every 4.5 yrs.

Speaking again to reliability of Yamaha conversions, an in-flight problem is not the same as a forced landing. The challenges for putting power to the prop as addressed by Ernie, first, to me, and others, have been minor and ALL failures in gearboxes have been limited 100% to Rotax equipment failures - bearings going bad. So far as we can tell these failures were likely due to contamination or assembly/installation error.

Using the Russian gearboxes which do not require pulling the cases apart just to install them, we know of zero problems of any sort. MAC and Tango Gyro sell variants of the PSRU distributed by Air Trikes as the SPG4. Tango's PSRU is listed as SPG, MAC's is AK7.

I have built, flown and sold dozens of YG4 aircraft conversions, using Rotax C, Arrow, Airgear, and even my own prototype silent chain PSRU.

Not a single in-flight issue has been experienced by myself, nor reported to me by anyone.

As for clutches, we used to think that a clutch was necessary to start all Yamaha Genesis engines. This is not true. The engine needs to be in good tune condition, and if hard starting is experienced we have found that adjusting the valves is all that is required for excellent cold starting characteristics with a direct-coupled (no clutch) rubber flex shaft coupling.

One vendor tried using the Rotax C type rubber donuts and these failed almost immediately. MAC uses heavier-duty BMW style flex shaft couplings, and there have been no signs of wear of failure.

RK400 clutches and other centrifugal clutches are popular for smooth starting. These all have their own set of issues and maintenance requirements.

I decided to get around centrifugal clutches with one-way roller ramp clutches. The first design was faulty and allowed the clutch's hub to shift in relation to the outer race, resulting in overrunning failure when shutting down the engine. After a redesign in 2017, the clutches have not shown any indications of failure.

I did have an electrical short to ground in 2013 after my first 20 hours. It was connection that had broken on the bench prior to installation when the motor tipped over during work, and my repair job failed. The regulator fried, and the engine ran off the battery until the display went dead. After that I continued on to fly back to base w/o any loss of engine power, a distance of about 7 miles.

This is about as honest and straight forward as I can be.

I am very proud and quite pleased to announce that I successfully built and sold the first reproducible, commercially available, Yamaha Phazer 80 HP, 4-stroke, 130# engine conversion kit this year.

Put side-by-side in comparison as an alternative (about same price) replacement for the popular Rotax 582, 2-stroke, 65 hp, ~123 lbs 12 years of Yamaha gyroplane (oh, yeah, and FW came later, too) history proves this is the engine for the future.




 
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fara

AR-1 gyro manufacturer
Joined
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Messages
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..

I haven't heard of a single forced landing by any of the 150 Yamaha conversions built and flying in the last 12 years.

A guy flying to the STOL competition at Oshkosh this year broke his 912 series motor en route.

Hey that is not true. I know of at least 2 Yamaha conversion engine outs in trikes alone. I think they were 130 HP (claimed but never materialized).

The STOL guy who broke his 914 enroute and documented it on youtube, had a bastard 914 on his plane. It was his 914 assembled from used parts from parts from various sources and aftermarket parts. Devil is in the details. Its not that 91x series never have engine outs. Its that people in conversion market make claims that are not verifiable or complete fabrications and the fleet size is low.
Can I ask what is the fleet size of your Yamaha based conversions right now and how many hours have the top 5 conversions flown? 100, 200, 500 etc.?

I absolutely hate the fact that some of the Yamaha conversions require a clutch because they shake the hell out of themselves with load at idle.
 
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fara

AR-1 gyro manufacturer
Joined
Oct 31, 2011
Messages
3,290
Location
Tampa, FL
Aircraft
AR-1
Total Flight Time
3600+ .. New to gyroplanes
Using the Russian gearboxes which do not require pulling the cases apart just to install them, we know of zero problems of any sort. MAC and Tango Gyro sell variants of the PSRU distributed by Air Trikes as the SPG4. Tango's PSRU is listed as SPG, MAC's is AK7.

I have built, flown and sold dozens of YG4 aircraft conversions, using Rotax C, Arrow, Airgear, and even my own prototype silent chain PSRU.

Not a single in-flight issue has been experienced by myself, nor reported to me by anyone.

As for clutches, we used to think that a clutch was necessary to start all Yamaha Genesis engines. This is not true. The engine needs to be in good tune condition, and if hard starting is experienced we have found that adjusting the valves is all that is required for excellent cold starting characteristics with a direct-coupled (no clutch) rubber flex shaft coupling.

One vendor tried using the Rotax C type rubber donuts and these failed almost immediately. MAC uses heavier-duty BMW style flex shaft couplings, and there have been no signs of wear of failure.

RK400 clutches and other centrifugal clutches are popular for smooth starting. These all have their own set of issues and maintenance requirements.

I decided to get around centrifugal clutches with one-way roller ramp clutches. The first design was faulty and allowed the clutch's hub to shift in relation to the outer race, resulting in overrunning failure when shutting down the engine. After a redesign in 2017, the clutches have not shown any indications of failure.

I did have an electrical short to ground in 2013 after my first 20 hours. It was connection that had broken on the bench prior to installation when the motor tipped over during work, and my repair job failed. The regulator fried, and the engine ran off the battery until the display went dead. After that I continued on to fly back to base w/o any loss of engine power, a distance of about 7 miles.

This is about as honest and straight forward as I can be.

I am very proud and quite pleased to announce that I successfully built and sold the first reproducible, commercially available, Yamaha Phazer 80 HP, 4-stroke, 130# engine conversion kit this year.

Put side-by-side in comparison as an alternative (about same price) replacement for the popular Rotax 582, 2-stroke, 65 hp, ~123 lbs 12 years of Yamaha gyroplane (oh, yeah, and FW came later, too) history proves this is the engine for the future.




Ok so if you are buying SPG-2 or SPG-3 from Vassili Tarakanov in Canada, you should know you are paying more than double. These are built in Bella Roos and originally cost like $500 or less. I would not buy anything from Vassili or have a business relationship with him. I dealt with him for over 4 years. That was more than enough for a lifetime. There is German company manufacturing an improved version of these gearboxes for Chinese military drones in China also.

What is the longest a single Yamaha conversion for aircraft of yours (current configuration with gearbox) has gone in terms of number of hours without any major change/maintenance. Years do not mean anything in this ... hours do.

BMW coupler is a bit stronger but it should also be changed every 500 hours on SPG gearboxes.
 

jm-urbani

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Dec 21, 2010
Messages
476
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French Riviera
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home built mono seat
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165HP comes on with maximum cam timing on this version of the Genesis 4-stroke around 10,500 ERPM. That sounds like a lot, but let's put that in its proper perspective. The engine is the tried and true Yamaha R1 1000cc motorcycle engine that has been run on street and track for two decades with a redline at 15,000 ERPM, and often gets raced much higher.

So at about 2/3 of the red line rev limits of the engine it produces 165HP.

Let me add the following narrative to put Rotax in perspective. It used to be you only really had two choices: Rotax, or a very heavy, somewhat unreliable automotive conversion. Then we were presented with Yamaha Genesis power plants in 2007. Nothing has been the same since in the EAB world.

Rotax built their first 4-cycle 912 series motor in 1989. Yamaha was already building 4-strokes 15 years earlier in 1979.

Rotax sold 50,000 4-strokes from 1989 to 2014, $1 billion in sales.

Yamaha did $1.5 TRILLION in sales in 2014 alone. Dividing by $14,000 average per unit (this is a very high, very conservative number) sold we get 100 MILLION engines for motorcycles, boats, snowmobiles and ATVs. Granted that includes both 2- and 4-stroke engines, but there are no figures that are available that break it down and they sell more 4-strokes than 2. Let's call it 50,000,000 4-strokes sold in 2014.

That means that during 2014 Yamaha sold 50,000 4-stroke engines in about 9 hours.

Nine hours.

In the motorcycle racing world there has been no doubt about Yamaha's dominance since the late 1960's, but the Formula 1 auto racing venue is the coup de gras for any engine manufacturer's R&D, the undisputed pinnacle of piston motor engineering. Yamaha participated in F1 1990-1997, with 16 points finishes placing as high as 2nd.

I haven't heard of a single forced landing by any of the 150 Yamaha conversions built and flying in the last 12 years.

A guy flying to the STOL competition at Oshkosh this year broke his 912 series motor en route.
Hey ! it is not because I am asking @ what rpm you get your 165 hp and your 80 hp ( on this point you did not reply) that I am thinking that your engines are running too fast making them prone to failures !!!
I am not seeling engines of any sort, I am not selling gyros, and I am not belonging to the sort of people who spend their time criticizing those who do things in the realy life
I just needed a piece of info that's it
 
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loftus

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Mar 17, 2013
Messages
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Ponce Inlet, Florida
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Aircam
Total Flight Time
500 hours
I don't think this ought to be a Yamaha vs Rotax discussion. Rotax are great, reliable engines with all the factory support, service advisories etc that go with certified aircraft engines. Fortunately the non-certified engines get pretty much the same benefits in this regard as the certified engines. True Rotax are expensive, technology possibly a little dated and conservative - but again probably related to the logistics of being certified engines.
Lycoming and Continental are the most dated of them all, but still the go to standard in civilian aviation. The more conservative approach suits most of those like myself who are either not homebuilders, or people who would rather use 'stock' aircraft engines in their aircraft and for whom guaranteed factory and dealer support are essential. (Worldwide)
Yamaha not being part of the certified family will appeal to those who are ready to step out of the envelope in order to benefit from things like price, more power etc. But remember that option is available for all engines, including Rotax, Lycoming (clones particularly) etc. Rotax 914 mods for example can provide upwards of 160HP with some racing mods being even higher.
I think if Yamaha were to enter the aircraft market they would definitely be competitive, but are hardly likely to be sold anywhere near to their current prices. Same goes for all the car mods like Suzuki and Aeromomentum out there.
 

Resasi

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if they ever decide to get into the same aero market niche occupied by Rotax it would spell disaster for the comparatively tiny Bavarian engine builder.
...but they haven’t???
 

ultracruiser41

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Building an outback version of a naked Tango.....was going to give the Yamahaha a try.....but decided to go with the Honda Viking Engine.....new.....factory fresh engine with a tried and true, heavy duty gearbox. Mounting area for the gearbox on the Yamahaha just not very beefy. Besides.....the Yamahaha is used....no idea how many hours or how it was ran.....old sled harness and lots of unnecessary wires. Looking forward to the Honda.
 
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