Wild West Aircraft

For general discussion of the Just Aircraft family of aircraft.
Includes: Highlander, Escapade, Summit and SuperSTOL.

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Re: Wild West Aircraft

Postby Gardlander » Wed Nov 02, 2016 4:30 am

What about this engine from Mohawk ? 150hp, just plug and play......or ?
http://mohawkaerocraft.com/mohawk-gt4-engine
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Re: Wild West Aircraft

Postby GT_Mills » Tue Nov 15, 2016 12:11 pm

Mohawk Aero provides the engine, PSRU adapter, and PSRU. You will need Steve to help with the FW engine mount and exhaust.

I see lots of questions and some misinformation here, so I joined the forum to help provide some answers and provide what I can in the way of technical information for the Yamaha engines and maintenance.

First, about weights: The YG4 NA (Normally Aspirated) weighs exactly 125# with the carb rack attached. This is the engine EVERYONE uses on their aircraft when going for the higher HP Yammies. The YG4 FI (Fuel Injected) weighs 118#. It is much more complicated to cheat the electrical system feedback loops to the ECU, so it has not been used on any aircraft that I am aware of with the exception of Rotor Flight Dynamics' tandem Dominator gyrocopter. Ernie spent well over a year installing the engine (2011), PSRU, and clutch, and wrestling with the wire loom. He was finally confident enough in the gyrocopter to sell it to a customer in 2014 or 2015.

I built the second YG4 aircraft, a tandem Air Command gyroplane, and completed the project in about 7 months in 2012. It was perfect right out of the gate, and I never had any problems flying with it whatsoever. Matter-of-fact, there is a little story about that.

The carbs have electric heat and liquid heat. The electric heat is primarily to get them pre-heated in sub-zero temps on the snowmobiles. I had cracked one of the carb wire terminals while the YG4 was on the bench, it tipped over. I repaired it with blue gasket maker silicone, not being too worried since the electric heat was useless anyway for flying what with the liquid heat being all that is needed. After about 20 hours, the lead went to ground while flying. It fried the voltage regulator. When the battery drained to 11.99V, the stock Yamaha multi-function display (MFD) went blank. The engine didn't burp, didn't lose even 1 RPM. I turned back to the airport and landed w/o any further trouble.

First thing I checked was the VR, and it was really hot so I knew at once it was fried.

I restarted the engine, and disco'ed the ECU. The engine kept running! So I disco'ed the battery lead. The engine kept running! I revved it up to 7500 RPM, just to check if there were any limiters in play. Nope. Finally, I disco-ed the two-wire connecter that feeds the mag to the spark plugs and their individual coils. The engine finally quit.

(I should add that I use the stock Yamaha pulse pumps, with an electric back up like a Cub system.)

I don't expect this with a YG4/3 FI, simply because once the ECU goes dead you will no longer get fuel, right? I'm not sure, tell you the truth. I will check it out when I start work on my first YG4 FI very soon.

We already have the adapter for the YG4 FI, just haven't bought an engine to work with yet.
--------------------------------------------------------

The YG4 makes more HP than the YG3 by turning smaller pistons faster and by breathing better - It has 5 valves/head rather than four like the YG3. The YG4 NA has no real redline, not on the stock tach. Someone told me the factory suggests 10,200, but everyone else I have spoken with says it is 10,700. I do know that sled racers spin these things up well over 11,000 RPM regularly without any issues (bent valves from piston rod stretch, e.g.). Myself, I haven't flown any of mine up past 9700 RPM, which is where you first see 140HP. Beyond that, you can squeeze another 3 HP out of the engine when you hit 10,000 RPM. I can't remember what Steve said he was climbing out at.

One last, VERY important note: The YG4 has a geared 1.19:1 internal countershaft. When the engine is turning 7200 RPM, for example, the output countershaft is turning 6050 RPM. Yamaha spent two full years developing this countershaft, it is no small engineering feat. It incorporates a highly specialized compound rubber harmonic damper, something the YG3 is missing. We all know how important prop-engine harmonics coupling and constructive wave formation is when it comes to aircraft power plants, since the engine is often, and typically, run at a constant speed for extended periods w/o change. If someone were to set the throttle at a speed that facilitates constructive wave formation of these two harmonic generators, the result is always catastrophic.

This cannot happen with a YG4, since the harmonic damper arrests/decouples harmonics between the prop and engine. This is WAY different than, say, a Lycoming, which attaches the prop to the crankshaft, and it is also completely unlike any Rotax product.

Feel free to contact me directly at

[email protected]

Join the new Yamaha Aircraft Engines Facebook page, https://www.facebook.com/groups/1251356 ... =bookmarks
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YG4 DYNO Chart 143 HP.jpg
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Re: Wild West Aircraft

Postby GT_Mills » Tue Nov 15, 2016 1:08 pm

About the discussion whether to use a Rotax C PSRU on the YG4, I understand that the rating on the gearbox is in regards to the mass you are swinging.

Rotax A is rated 3000kg/sq CM, and is CLEARLY not the right choice.

Rotax C is rated at 6000kg/sq.CM.

Another PSRU for comparison purposes, the Air Trikes SPG4, is rated at 9000kg/sq.CM, so I am told.

The choice is up to you. Mohawk will put any PSRU you want on a YG4.

Mohawk Aero has 35 hours on a purpose-built Hy-Vo chain drive unit, called the Silent Drive, that allows the prop shaft to be positioned higher up, in the same place as a Rotax 912/914 installation. This PSRU bolts right up to the YG4, there are no changes made to the crankcase cover and there is no adapter. It is still a prototype model and is not yet in production. The Silent Drive has a prop strike protection clutch, much like the Rotax 912/914 offers at a cost of $1300 extra. We're playing with plate spring tensioning in an attempt to find a sweet spot that will allow for soft starting, like a centrifugal or sprag clutch does, and thus eliminate the need for those types of clutches in the YG4/3 conversions while also providing prop strike protection at a fraction of the cost that Rotax demands.
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Re: Wild West Aircraft

Postby taildrgfun » Tue Nov 15, 2016 5:06 pm

I am working with someone right now to mate an SPG4 gearbox to the Yamaha Apex injected engine. This gearbox is rated for 180 hp and is currently on quite a lot of different engines. The people I'm working with have done a lot of this and they are figuring out the whole attachment including coupling it to the power output shaft.

If any of you think you might want to use either one of these Yamaha engines please let me know because I can help you out with everything you need.

I went to balance my Rotax carburetors yesterday because I thought it seemed rough but they were in balance, it's just that I have gotten used to this super smooth Yamaha!
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(the Dead Stick Take-off Guy)
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Re: Wild West Aircraft

Postby moving2time » Wed Nov 16, 2016 11:44 am

Steve, that is a really cool anecdote. Sounds like a real pleasure to be flying behind a smooth running Yamaha. Has the noise improved with the new muffler? Vibration and sound are the two biggest comfort concerns inside an aircraft. Both can really tire the pilot out. The Mohawk Aero post is also very exciting. Between the two of you the Yamaha could really take off! Pun intended. Joe B
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Re: Wild West Aircraft

Postby taildrgfun » Thu Nov 17, 2016 9:25 am

Joe the noise level is not a problem anymore with the header/muffler I'm using now. Comparable to my Rotax. I get comments all the time from different people about how good it sounds from the outside.
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Re: Wild West Aircraft

Postby av8rps » Mon Dec 05, 2016 11:42 pm

Hi Steve,

I saw your Highlander for sale on Barnstormers and after reading the ad where you talk about the removable wing extensions it prompted me to ask you these questions;

- Did you ever compare its performance with and without the extensions (I know you previously said you didn't think you'd do it again... is your opinion still the same?)

- Did you have the extensions on when you competed at OSH version of Valdez?

-I didn't see anywhere how you built them to be removable. Is there anywhere that there are pictures of that for me to see?

I hope I'm not being a pain as I know you are a super busy guy. But I still contemplate whether or not to extend the wings on my Highlander project, as I've always felt another 8 or 10 sq feet of wing area would make the Highlander an even better float plane, maybe?

Paul S.

Ps, that is a real kick ass Highlander Steve has for sale for any of you that don't have the time build one.
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Re: Wild West Aircraft

Postby taildrgfun » Tue Dec 06, 2016 6:04 pm

Yes I did have the wing extensions on when I was at Oshkosh, and I would do it again. I made them permanent on my newest Yamaha powered Highlander . They make the plane able to fly about 2 miles an hour slower, so it just depends on how important that is to you whether or not it's worth the effort. I don't think I have any pictures of how I made the removable extensions.

If any of you are building a Highlander and especially if you don't have the wings painted yet you really should get a hold of me about the leading edge cuffs. It is a very very worthwhile thing to put on your wings. They are a bigger deal than making your wings longer and much easier to do. With the leading edge cuffs, longer wings and longer flaps my Highlanders will definitely outperform any stock Highlander. These are not hard tricky things to do, anyone can do it and make their airplane that much better.

I am still very much liking my Yamaha and if any of you are thinking about putting one in your Just Aircraft let me know. I realize they are not the engine for everyone but for some people they will be an amazing good engine choice.
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Re: Wild West Aircraft

Postby john2 » Tue Dec 06, 2016 11:54 pm

taildrgfun wrote: I am still very much liking my Yamaha and if any of you are thinking about putting one in your Just Aircraft let me know. I realize they are not the engine for everyone but for some people they will be an amazing good engine choice.


Hi Steve,
The Yamaha is very intriguing and something I am considering in the future. The Rotax "C" gearbox is made for maybe 90 hp maximum and I hear that there has been some failures with the "C" box on the Yamaha engines. Can you elaborate on this any? Are you still using "C" box and has there been any issues? How many hours do you have on the combo now?
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Re: Wild West Aircraft

Postby taildrgfun » Wed Dec 07, 2016 10:09 am

I did have a bearing go bad in my gearbox but I think it may have been something I caused by not having the shaft shimmed exactly right when I changed the gears in the gearbox. I was also running a centrifugal clutch at the time it went bad because the engine would not start worth a darn with my big two blade prince prop. I put a new gearbox on it and I am trying a couple different propellers that have a lower mass moment of inertia and I am able to start the engine without the clutch. The prop that I am trying out now is a three blade 74 inch Kool prop. I am really impressed so far, it seems to perform as well as my two blade prince only it is much smoother and lighter and it is ground adjustable. I also have a new two blade 78 inch ground adjustable Kool prop that I am trying on my Rotax. If I like it on the Rotax I will have some made for the Yamaha's which turn the prop the other direction.

Another thing that I am in the process of trying out is the Beringer Alaskan landing gear with Beringer brakes and wheels and everything. I just got it all installed on my Yamaha Highlander but I have not got to fly it yet.
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Re: Wild West Aircraft

Postby moving2time » Wed Dec 07, 2016 10:58 am

Steve, the guy from Mohawk posted on his web site that you are going to be using their reduction drive that is rated for much more HP. Have you used their reduction drive yet or are you planning on using it? I ask because you have not talked about trying that drive out. I did a bunch of research on these gear boxes/reduction drives but the information I was able to find is confusing. There appears to be two drives that are talked about on Mohawk's website. One I believe is a gearbox like the Rotax and one uses a belt which seems to be designed for the gyro copters. The text and description of the development of these drives is very confusing probably because the development seems to have been going on for several years. I don't know why this kind of information isn't clearer on their related web pages. I'm guessing that these kinds of items are constantly evolving and the people making them are reluctant to show pictures or diagrams or any real concrete information because they may change at any moment. It is a real blessing that we have you out there as a user willing to talk about the new options that you are giving a try. As you know I ask a lot of questions. I sent Mohawk a bunch a questions and they have been very gracious about answering my questions but when I have so many I feel like I am being a pain in the ass. I try to get answers from more than one source to fact check but it is hard and the information doesn't always line up. You are the most reliable guy I know because you fly the crap out of everything you talk about plus I have been able to sit next to you and discuss some of this at Oshkosh so I know you are sincere and passionate. I really want to get started on a Highlander build by next Fall and I will need to try to get it done over the Winter so I can fly again in the Spring or at least the Summer. Hopefully everything falls together for me because I can't wait to be flying a Highlander and I intend to put something other than a Rotax on it. Joe B :)
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Re: Wild West Aircraft

Postby taildrgfun » Thu Dec 08, 2016 11:17 am

At this point when using the carbureted RX1 motor what is available is the Rotax C box on the SkyTrax adapter which is what I have been running for the last 130 hours and I like it. I still don't know what gearbox set up we are going to wind up with on the injected motor.
I just got in a YPG-4 gear box that is rated for 180 hp but I'm not sure if it's going to work because I don't like how far forward it puts the propeller flange. I really don't have any answers yet for the injected motor but we are definitely working on getting a gearbox adapted to it.
I just bought a 2006 Yamaha apex snowmobile and it is just wild how much horsepower these things have! This thing is like brand-new with 325 miles on it in absolutely perfect condition. We will get something figured out to be able to use these motors in our airplanes and I am sure looking forward to it based on how much I like my carbureted Yamaha engine in my Highlander.
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Re: Wild West Aircraft

Postby av8rps » Fri Dec 09, 2016 9:18 pm

Thank you for that great info Steve. Looks like I should seriously do those mods on my project plane. Being that I will use it on floats a good share of the time I'm thinking it would just make it an even greater floatplane.

Have you ever considered adding the flap system used on the Super STOL? Troy told me that flap is so large on the SS that it essentially inreases wing area by another 25%. He didn't think it would be that hard to add to a stock Highlander wing, but since no one has done it yet maybe its harder than it sounds?

When I get done with the house I am working on and back on to my more fun airplane projects I will connect with you for some of those leading edge cuffs. Maybe even tanks, as my project has the small tanks and I'd like a bit more range.

Paul


taildrgfun wrote:Yes I did have the wing extensions on when I was at Oshkosh, and I would do it again. I made them permanent on my newest Yamaha powered Highlander . They make the plane able to fly about 2 miles an hour slower, so it just depends on how important that is to you whether or not it's worth the effort. I don't think I have any pictures of how I made the removable extensions.

If any of you are building a Highlander and especially if you don't have the wings painted yet you really should get a hold of me about the leading edge cuffs. It is a very very worthwhile thing to put on your wings. They are a bigger deal than making your wings longer and much easier to do. With the leading edge cuffs, longer wings and longer flaps my Highlanders will definitely outperform any stock Highlander. These are not hard tricky things to do, anyone can do it and make their airplane that much better.

I am still very much liking my Yamaha and if any of you are thinking about putting one in your Just Aircraft let me know. I realize they are not the engine for everyone but for some people they will be an amazing good engine choice.
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Flaps

Postby BDA » Sat Dec 10, 2016 5:26 pm

Regarding flaps: Has anyone made flaps that were deeper in chord (than the SS flaps)??

For more wing area?
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Re: Wild West Aircraft

Postby taildrgfun » Mon Dec 12, 2016 10:25 pm

I have thought about doing different things with the flaps but up to this point really the only thing I have done is made them longer end to end.
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