New Approach to Yamaha RX-1 conversion

[teal]

Hello all, As a legal disclaimer I just would like to say that I do not have a business producing Yamaha adapters. I simply made one for myself in my hobbyist machine shop for my own craft, never with the intention of producing them to a market. A lot of interest from my friends came about after I started flying with the adapter. They eventually talked me into making more adapters for them. To recoup the cost of CNC machining and additional testing I made some more for sale. This is where the SKYTRAX adapter originated from. I love flying and hearing about individuals builds that's why I feel like I have continued to make these things. Teal Jenkins (623) 734-0185

 

[teal]

My latest RX1 install

 

[CLS447]

It really sux not being able to open those pics for a closer look !

 

[NoWingsAttached]

I got your adapter the other day and I really like it, and also like the improvements I see here on your exhaust over your earlier shorty design. Who makes this trike body? Very slick, very pretty.

 

[teal]

Here is a Sneek peek into the gear train on the new Skytrax integral gear box for fuel injected Apex engine.

 

[All_In]

Looks like you do quality work. Do you have a website PRA can forward people to or do you have contact info we can advertise for you?

 

[teal]

I don't have a web site. I just do this on the side and for now word of mouth advertising is good with me. My contact is 623 734-0185. I text message on this line too for simple questions.

 

[NoWingsAttached]

Here is a Sneek peek into the gear train on the new Skytrax integral gear box for fuel injected Apex engine.

Three gears, just like the Frenchman did on his YG3 a while back. After you texted a couple of weeks ago it sounded like you were going with an internal sprag clutch on the prop shaft, a-la Arrow gearbox. Still going with that, right? I know you aren't going to do it (we already talked about this), but I'd really like to see the clutch on the drive gear shaft. That way you could hang the clutch off the front of the gearbox. That would allow a separate clutch cover, and maintenance/ inspection would be a snap while saving an inch overall length to the prop flange. Also, the clutch must be able to handle 3 to 3.5 times more torque when on the prop shaft, meaning more weight.

 

[teal]

The benifit with using the prop. Shaft is i have a lot more room to use a larger diameter sprag and even though the torque is aprx. 3 times more there the RPM is 3 times less opening up the use of larger diam sprags. With torque arm strength going up exponentially with the larger diameter sprag I feel torque loads can be handled at the lower RPM better with a larger diam. Sprag.

 

[N447MR]

So I made it through the whole thread finally, but I don't think I saw any thrust numbers really. I recently did a static thrust on my stock 130 HP Subaru 2.2 on a hot day to adjust prop and get rpms up a bit.
I have a 68" Warp Drive and saw ~550#s. I'd have to believe that the YG4 would do better, right? I was thinking performance gross payload gain would come from increased horsepower, but I guess it would come from decreased weight instead?

 

[N447MR]

That's a big difference from the Viking Honda conversion site, their engine comparison figures I quoted. Thanks for the help in finding more accurate numbers for Rotax. I don't mind being corrected at any time, since I am not incorrect intentionally at any time.

So at around 120 pounds you can have
Rotax 912UL 81 HP
Rotax 912ULS 100 HP
Yamaha YG3 120 HP
YG3i 130 HP
YG4 142 HP
YG4i 150 HP

Add another 21 lbs and you can get a Rotax 914 100 HP, 115 HP for a few minutes.

Add the ancillaries to all of these engines and things shape up fairly equally in installed weights, while there is still no comparison in power.

How much does the Subaru 2.2 weigh? 300#s? Anyone know?

 

[NoWingsAttached]

How much does the Subaru 2.2 weigh? 300#s? Anyone know?

The only numbers I have are from Air Command in TX, Doug told me his was around 330 lbs. Not surprisingly you don't hear/see a lot of talk from Soobie guys when it comes to engine weights.

 

[NoWingsAttached]

So I made it through the whole thread finally, but I don't think I saw any thrust numbers really. I recently did a static thrust on my stock 130 HP Subaru 2.2 on a hot day to adjust prop and get rpms up a bit.
I have a 68" Warp Drive and saw ~550#s. I'd have to believe that the YG4 would do better, right? I was thinking performance gross payload gain would come from increased horsepower, but I guess it would come from decreased weight instead?

My YG4 using 2.58:1 PSRU at only 9000 ERPM (7560 SRPM @ ~90# torque) and 135 HP produced 530# with a 68" 3-blade Warp.

Using 3:1 PSRU (3.57: final drive ratio) every YG4 will always get 600# thrust. Example: tests on Kurt Carleson's Air Command single YG4 with a little 66" 3-blade Warp Drive produced 600# in fairly ideal conditions @ 1200 MSL, partly cloudy and 70 degrees.

Some of my customers are comfortable now going to the 3.47 gearing (4.13:1 final drive on YG4 and 4.27:1 final on YG4i) but we don't have thrust data back yet. I'll get back later when I have something to report. I expect we will blow past 600# quite easily, especially since we are testing with the YG4i as well as the YG4 these days.

Working in baby steps toward that goal I have always had in mind: Yamaha boosted power for aircraft, easily 200-250 HP. The day is coming, folks.

 

[NoWingsAttached]

So I made it through the whole thread finally, but I don't think I saw any thrust numbers really. I recently did a static thrust on my stock 130 HP Subaru 2.2 on a hot day to adjust prop and get rpms up a bit.
I have a 68" Warp Drive and saw ~550#s. I'd have to believe that the YG4 would do better, right? I was thinking performance gross payload gain would come from increased horsepower, but I guess it would come from decreased weight instead?

I just realized after going back thru this thread that Teal did post thrust numbers significantly lower than we are getting, but my post above said everyone should be getting the same thing. I don't understand the difference, maybe intake and exhaust? Hard to say.

I think he was trying to figure out if different exhaust headers made an impact on top WOT thrust. He didn't make mention of any thrust numbers in the midrange, which is where the advantage of longer headers is.

1-25-2016

Header testing

I spent the last couple days doing some header testing. I tested 3 headers. The first was a tri y or what's commonly called a 4-2-1. The next was a short a 4-1 I use on the trikes and the last was a basically the same as the 2nd except with 7 inches added to the primarys. I was using clamp on K&N filters with 170 main jets at 1000 ft msl. (Do not try to run stock jets without the airbox). The prop was a prince p-tip 74 inch dia. 37 inch pitch. The first set of pulls was done with a 3.47:1 ratio gear box and I pulled 550 to 570 lbs with all 3 headers. The long 4-2-1 header seemed a little smoother as it came up to full power so I image the torque was probably Better in the low end. It may have pulled a bit more at wot. Prop rpm went to a little over 2500 and engine rpm went to around 10,300. The next set of pulls was with a 3:1 ratio box, it pulled 510-530 lbs. The prop went to about 2400 and engine was around 8500 rpm. Same results with the 4-2-1 sounding the smoothest it came up on the power but the top end was almost the same.

Before I get to discussing the results from Jenkins test let’s start out by first comparing apples-to-apples.

Jenkins: Prince P-tip (3 blade?) 74" 3.47:1 10,300 ERPM/ 2500 PRPM 560 lbf +/- 10

Mills: Warp Drive 3-blade 66" 3.0:1 10,300 ERPM/ 2885 PRPM 600 lbf +/- 10


Jenkins: Prince P-tip (3 blade?) 74" 3.0:1 8500 ERPM/ 2400 PRPM 520 lbf +/- 10

Mills: Warp Drive 3-blade 68" 2.58:1 8700 ERPM/ 2835 PRPM 530 lbf +/- 10

Mills: Warp Drive 3-blade 68" 2.72:1 9200 ERPM/ 2840PRPM 560 lbf +/- 10


My setup with smaller, cheaper prop, lower gear ratios, higher humidity, higher prop speeds produced significantly higher thrust/ power. It wasn’t a fluke.

Some of the Georgia results were repeated to within 1 lbf at different times, different airports, done by different people using different measuring instruments at comparable air density.

The Georgia tests were done at same altitude as Arizona test, 1100 MSL, and though probably similar temps (Jenkins’ test was done in January ‘16) the GA humidity is much higher than AZ.

A Prince P Tip Prop costs at least three times as much as a Warp Drive, with the selling point to justify cost being that it produces more thrust. Or so I would imagine.

Next, a bigger prop turning a slower speed is far more efficient than a small one turning a faster speed.

Let talk a little bit about the exhaust, and start out by clarifying terminology so we don't get mixed up down the road:

1. "Header(s)" is the section of the exhaust system that includes everything from the head (hence the word "headers") to the first collector.
2. "Collector" is the junction of two or more pipes, reducing the number of pipes downstream.
3. "Exhaust pipes" is the second section of pipes after the first collector, even if it includes another collector, X crossover, etc.
4. "Muffler" is the last thing added to quiet things down so we don't all wind up with tinnitus.
5. "Exhaust system", more often called just "the exhaust", is the whole she-bang.
6. "WOT" = wide open throttle, and for this discussion only I use it to indicate the engine's peak power RPM, not prop-pitch-limited RPM as it is used to mean in virtually every other discussion regarding aircraft power plants. This is important later on in the discussion so keep this difference in mind.

Three things affect power output when it comes to the exhaust: back-pressure, turbulence, and length of pipe.

First, a little back-pressure is a good thing for fuel consumption, valve and valve seat life, and even maximizing HP. Too much back-pressure results in poor air flow and loss of power.

Second, turbulence reduces air flow. Think of a ball of cotton in a plastic tube. You can blow slowly through it just fine, but when you suddenly try to blow hard it seems like you just plugged it up completely. That's what happens with turbulent air flow.

Third, surface friction and thus turbulence of air flow through the pipe is obviously increased by length of pipe.

Length of header affects midrange power greatly. A very short header can reduce back-pressure, resulting in some top-end WOT gains. In an engine that is meant to run WOT only like a dragster this is the best way to go. In an engine that is run most of the time at midrange power below WOT this is not such a good thing, because the 10-20% power loss due to improper free length of headers results in excessive fuel consumption due to a need to turn up the wick unnecessarily, and excessive engine wear due to running at higher RPM than should be necessary. It also results in a frustrating "peaky" throttle, where you smoothly continue to add throttle and there is no response, until you hit WOT and the engine jumps to full power suddenly.

Resistance to airflow and expanding gases is a function of pipe ID and length, resulting in back-pressure. In some cases of a long header it helps to gradually increase pipe ID as you progress downstream to the collector, to decrease back-pressure. In some well-tuned headers these stepped systems can wind up at very near to top-end power seen with the shorty "dragster" style pipes.

Length of exhaust pipe AFTER the first collector affects overall power as backpressure is increased due to longer pipe length. This can affect power across the power band, not just midrange or WOT.

So why is a long header better for midrange power than a shorty? That goes to turbulent back-pressure created by adjoining a second flow to the first. The piston needs to be able to smoothly push out all of its expanding gases from its cylinder through one full stroke w/o interference. The length of pipe required before any such turbulent junction, or collector, should come as close as possible to a volume equal to that of one piston stroke of the one engine cylinder. You can cheat a lit at the end of the stroke, but the more you cheat the more loss of power you will see.

a 1000cc 4-cyl is 250 cc per stroke, so you can calculate ideal length of header from

250cc = pi x R[SUP]2[/SUP] X L.

Our pipe is D = 3.28 cm, R = 1.64. We find that the ideal header length is then 250/2.67 = 93.63 cm = 36.8", less the length of space in the head after the valve.

Like I said, you can cheat. The tuned headers I have built are usually about 21” long, and the length after to the muffler is 7-8”.
It would be a great idea to check midrange thrust numbers as a way to tell what is going on with the power lost due to length there. The trouble is, no one ever does that. Funny, since 90% of everyday flying is done at 75% power setting…

According to my numbers, 1 HP converts to ~4.25 lbf thrust. It is easy enough to interpolate HP given RPM and thrust number, and that tells the tale of lost HP due to insignificant length of headers.

 

[Vance]

If someone wants to learn about exhaust systems I recommend The Scientific Design of Exhaust and Inlet Systems by Smith.


Much of the content is substantially divergent from Greg’s post.

 

[NoWingsAttached]

If someone wants to learn about exhaust systems I recommend The Scientific Design of Exhaust and Inlet Systems by Smith.


Much of the content is substantially divergent from Greg’s post.

I never read up on this stuff, some of it came from what Jake told me while we were discussing designing some headers for the YG4 together since he does all of my welding, other stuff is what I've read casually. Thanks much for the references, I'd like to read up on it more!

 

[NoWingsAttached]

The Mohawk GTI [Yamaha YG4i (Apex 150HP fuel injected engine)] adapter sales really took off since I introduced them January 2017 :smile: Some folks flying tractor FW wanted a shorter power plant right away, without waiting for my 2015 Silent Drive to be a production PSRU, so I offered them Rotax C (RXC) gearbox adapters as well as Mohawk AK7 (Air Trikes' SPG4 first cousin). If ya give a mouse a cookie...I searched and searched but couldn't find any updates or maintenance info anywhere on RF provided by the YG4-RXC experts who have been flying and selling this equipment for 3-1/2 years. I finally started a thread here in spring 2017 after I learned of a RXC bearing failure at 110 hrs. It turns out that failure actually had occurred October 2016, 4 months before I learned of it and posted about it on RF, for you guys, and so I could learn from it and determine what I needed to tell my new Apex RXC customers what to look out for and how to avoid known problems. There was a response on that thread that referred to a shimming problem. Since that thread was started, I have had a chance to inspect an RXC in my shop, and I am stymied by the explanation given.

Here is a drawing showing the drive gear, shaft, flange, bearings and the 0.020" shim (purple). I can't understand how shim placement, one side or the other, can possibly cause bearing failure: The spacing and axial load distribution remains identical as far as I can see, regardless where the shim is inserted left side or right. IF the shim is left out entirely then that would cause unbalanced axial loading on the left side bearing. If the RXC is attached to a motor that instead turns CW, then only the left (inner) side bearing is ever axial loaded since the shaft is a slip fit into the bearing IDs. This means Subaru (which turn CW, YG4 turns CCW) EJ2.5 and even 2.2 engines could be expected to tear things up quickly, according to my latest bearing life calculations. But Ron Awad (and perhaps some others as well) is convinced that these PSRUs are reliable with Soobie 2.5 & 2.2 engines. Go figure.

So I am at a loss, still searching for enlightenment for myself and my Mohawk customers wanting RXC's.

See drawing. Maybe you can help us understand this thing? I thought it might be contamination, but given that I am to understand that the gearbox had been running fine for 110 hrs, this doesn't seem all that likely.

The other gearboxes I have seen all load only one bearing axially, anyway. Many PSRUs only have one deep-groove bearing for axial loads, with the other (outside) set being needle or cylinder bearings.

 

[NoWingsAttached]

It has just come to the attention of many of us on FB last week that Teal had a Rotax hardy disk fail on his first (Honda) conversion, predating the 2014 Yamaha RX1 adapters he fabricated and sells here. And although I became aware of a Yamaha RX1 Skytrax RXC hardy disk failure last April 2017 I found no information about any of these incidents anywhere on this thread or elsewhere on RF - so I posted my own thread in hopes of learning and understanding the cause and effects of this type failure, but last time I checked that thread it had 120 looks and not a single response. I still don't see any info about it in this thread, or anywhere else on RF, so we are all pretty much still in the dark on this.

Many of you don't use Facebook, and even though you can view stuff on it w/o signing up you don't care to. There is a blog on FB now where Teal has just started posting this type of info for open discussion. Hopefully some of that info will find its way here at long last w/o me having to keep bringing this stuff up all over the internet - here, Avidfoxfliers and FB. It makes me look like Mr. Sour Grapes, and frankly I have a character such that once I get started in on a particular matter I tend to over-emphasize, scrutinize, and get myself into trouble by becoming a real jerk once I start writing w/o a publicity editor to reign me in. My humble apologies.

 

[NoWingsAttached]

In closing, this is disturbing on many levels:

Post #1
New Approach to Yamaha RX-1 conversion
04-23-2014, 10:16 AM
Hello all, I am new to the forum...I am using this forum to find out who may be interested in purchasing a adapter or possibly a complete set up ready to fly.

#43
11-25-2014, 10:41 PM Accepting orders now! call me back if you all ready spoke to me and I put you on hold until I had the finished product. I will be trying to contact you guys in the coming days but I suggest if you want your adapters now to call. The price once again is $1500 + shipping no negotiating no trading for anything.

#94
04-24-2015, 02:52 PM
Skytrax Adapter
Hello all, Its been a while since I've been on here but I wanted to put the message out again since I got a few personal messages asking for the price and what is included in the Adapter Kit. So here it is...Teal PRICE: 1500.00 plus shipping

#104
12-19-2015, 10:40 PM
No lead time
I have them on the shelf and ready to ship. I make a batch of them at a time. I ship them as soon as someone pays for them.

#106
12-24-2015, 09:27 AM
C gearbox
I have new rotax c gear box's with 3:1 ratio. they are $1550.00 a piece.

******

#161
Page 11
02-16-2017, 02:06 PM
Hello all, As a legal disclaimer I just would like to say that I do not have a business producing Yamaha adapters. I simply made one for myself...Teal Jenkins (623) 734-0185


I leave this to speak for itself.

 

[teal]

I invite everybody to read my complete post on me not having a business doing this. not just a portion that Mr. Mills copied and posted to try to make me look like a bad guy. Im really unclear what your trying to do or what your motives are but I really dont appreciate you attacking my character.