Anything new on Yamaha conversions?

NoWingsAttached

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The mating surface area of the stock YG4 taper shaft is 30mm dia X 34mm L x 1:10 taper = 3022 sq mm

The depth of the bore and therefore the mating surface of the Arrow gear bore is identical, as is the primary clutch on the Yamaha snowmobile.

On my first "Silent Drive" drive gear, which was intentionally jury rigged to get it into the air quickly for testing, the drive gear bore depth was only 26mm, so the end of the shaft had to be ground down so it wouldn't bottom out. Apparently there is a need to similarly clearance and cut down the Yamaha shaft from 34mm to 26mm to accommodate the installation of a Rotax C Box ( although I have no experience using this PSRU so I can't really speak to why it is necessary to do so) either with or without the RK400 clutch. I think it has something to do with a lack of clearance for the head of the shaft bolt which holds the shaft coupling in place.
 

Jason O

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Jun 13, 2007
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Hello,

From what you are saying below, it was full length, it was a perfect taper, it was torqued. It was perfect, and still slipped so the only conclusion I can draw from that is that it would not be possible to stop the shaft from slipping.

I have no idea what you are saying about rotor blades, we have never met, you have never looked at a gyro I have flown. Its just one of the many made up stories in your head you use to keep the bluster up.

FWIW
Jason


Jason:


1. The shaft on the engine discussed was FULL LENGTH

2. The drive gear was a perfect fit on the 1:10 taper shaft

3. The drive gear was torqued to spec

4. The gear slipped on the full length shaft

5. By simple math, shortening the shaft 25% (~5/16") makes this type of slipping more likely to happen on any installation, by any builder. (Recall I said I cut down my own shaft on the prototype Silent Drive installation, and was happily reporting here that I had finally received the correct drive gear which would not require cutting the shaft down.)

6. Resonance has nothing to do with it. Unlike the YG3, which delivers crankshaft harmonics to the PSRU coupling, the YG4 engineers at Yamaha spent two full years developing the internal countershaft damper (I have already posted photos of it elsewhere on this thread) which arrests all engine harmonics before they can reach the taper coupling we are talking about. Additionally, the Arrow PSRU has an internal one-way clutch which arrests constructive wave formation of prop harmonic vibration.


One has to wonder: If I discovered cracks on a particular rotor blade - which you also happened to be flying on your gyrocopter - and I reported it here, would you be responding to my posts in the same manner as you have above?
 

teal

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As far as cutting the shaft shorter, I am using the full contact area that Rotax designed for their flywheel. Now There maybe a debate on what horsepower Rotax designed that flywheel to handle with that contact area. But there are plenty of examples out there of Rotax C gearbox's running many hours with 100+HP engines. In fact I have one currently on my Long EZ for over 400 hours with a Honda engine. I have at least 7 adapters on the RX-1 engines out out there running this configuration with no issue's. How many successful installations do you have out there Mr. Mills? I'm not saying you wont have a successful adapter kit some day and I wish you the best after all we all succeed when one of us has success. Lets just work together to help each other out instead of talking down on others products by saying that they are "jury Rigging". In your definition of Jury rigging we are all jury rigging because we are changing or modifying a original design that the original engineers did not intend on.
 

NoWingsAttached

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As far as cutting the shaft shorter, I am using the full contact area that Rotax designed for their flywheel. Now There maybe a debate on what horsepower Rotax designed that flywheel to handle with that contact area. But there are plenty of examples out there of Rotax C gearbox's running many hours with 100+HP engines. In fact I have one currently on my Long EZ for over 400 hours with a Honda engine. I have at least 7 adapters on the RX-1 engines out out there running this configuration with no issue's. How many successful installations do you have out there Mr. Mills? I'm not saying you wont have a successful adapter kit some day and I wish you the best after all we all succeed when one of us has success. Lets just work together to help each other out instead of talking down on others products by saying that they are "jury Rigging". In your definition of Jury rigging we are all jury rigging because we are changing or modifying a original design that the original engineers did not intend on.

Thanks, Teal, and nothing personal, I assure you. What seems to be getting totally ignored in this exchange is that I was reporting that I took delivery of a new drive gear for a bolt-on YG4 PSRU - which eliminates the need to cut down the shaft 25%, to accommodate the jury-rigged and welded gear I was using temporarily, which is something I've decided for very good reason isn't such a great idea. As an aside, I mentioned that other engine conversion designers are grinding down the engine shafts like this. Take away from it what you will.

So, in other words, the bolt-on YG4 PSRU I am developing is just like the Yamaha adapter I designed and quite successfully installed on the RX1 YG4 back in 2012 in that neither one requires grinding the shaft down.

Your mention of the EZ Honda is apples to oranges and is only 100 HP.

The Rotax flywheel and surface area is not in my wheelhouse, but I do know that the RK400 clutch which is an aftermarket product originally designed for use on the low-power (70 HP max) Rotax 2-cycle engines is 34mm wide - the same length as the stock YG4 shaft, and much wider than the 26mm you are grinding your shafts down to on the 140-150HP Yamaha RX1 (YG4).

There's a big difference between 34mm and 26mm, and it certainly doesn't matter how many adapters you've sold to date. What does matter is how many have been flown extensively and removed for inspection?

I'm not sure what the worst thing that can happen here is, other than the shaft will gall in the bore and then you won't be able to remove the shaft coupling, which would be a big maintenance headache down the road.

Either way, what I design and build for use on the YG4 does not require grinding down the output shaft (aside from the jury-rigged temporary fix described here for test purposes only - I would never sell this to a customer!) and will therefore never risk compromise due to this poor design practice.

Since you want to discuss your adapter here, while we're on the subject: Your adapter is missing the oil separator found inside the OEM crankcase which keeps the oil from flooding the breather tube on steep climbs. It would be a very simple thing to fix your adapter design so that you can reuse the separator that is in the stock cover.

I can't understand why you don't update your adapter design for this simple thing, and then also to fit a PSRU such that you don't have to grind down the shaft? I'm not being mean, I'm just asking the question.
 

teal

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Greg,
The Oil baffle/separator can be installed in my adaptors, my first few adapters need to be notched for the baffle ear but they can be used but I personally have had steep climb testing without the baffles not installed and had no oil carry over into the air box. Now on my first adapter that I manually machined I had a little oil carry over but that cover did not copy the exact oil deflection webs like the new adapters do. As far as using the Rotax "c" gearbox and grinding the shaft I think you need to understand the flywheel mounting better to see what Todd and I are doing. I really like the Rotax gearbox for its availability and proven design is the reason why I use it. I appreciate your questions. Teal
 

GyroRon

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for some reason greg can't understand that your not cutting down the output shaft shorter than the distance of the flywheel. In other words the flywheel's full tapered surface is fully filled with tapered output shaft.
 

Trackwelder

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Nowingsatttatched, how is the redrive for fixed wings coming along, I have my Avid Built and ready to build the motor mount for the Yamaha 4 cylinder, I have been looking for a C box since I only have an A and a E box, I could probably mount the E box but I would rather have the taller redrive. I had the rest of my lumbar spine fused so I have not been real active this year on building, and now we have all this white stuff on the3 ground so it would be nice to get the engine built this winter, I will probably have to build a new cowling no matter what I do but I still like the idea of your silent drive, you just need to get one built and tested so I can buy the next one, keep us informed I really would prefer the Yamaha over another 582 Rotax.
 

teal

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fixed wing engine install

fixed wing engine install

I recently purchased a Kitfox with a 912ul in it. It flies great for what it is but a lot of guys have been asking me about installing a Yamaha in these aircraft so with out doing it myself I cant answer those questions. So after a couple of other Yamaha installs I need to do for a few trike guys I will be removing the 912 from my Kitfox and replacing it with the Yamaha. The avid from what I understand is very similar to the kitfox.
 

Trackwelder

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I am waiting to see one with the Yamaha, I have the engine, but was hoping someone could come up with a redrive that was taller or maybe lay th engine over a bit more so the Redrive ideally would be the tallest part of the eengine.
 

NoWingsAttached

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for some reason greg can't understand that your not cutting down the output shaft shorter than the distance of the flywheel. In other words the flywheel's full tapered surface is fully filled with tapered output shaft.

This is what I have, courtesy Air Tech, the folks who make the Rotax RK 400 Clutch.

What you're saying does not jive with what I understand from the PDF our friends at Air Tech have provided Mohawk Aero.

The hub depth here matches the length of the taper on the YG3/4, give or take a millimeter or two. I still don't see why you have to grind 8mm of the shaft off, Ron.
 

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NoWingsAttached

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The issue with using the YG3/4 with a tractor FW is the height of the prop shaft. Unlike simply attaching a standard gearbox to the output end of an engine, the Mohawk YG4 Silent Drive was engineered from the ground up such that the YG4 is a direct swap for any FW using or designed for use with a Rotax 912/914.

Those kits are designed with the prop at the top of the engine, a-la Rotax 912, not somewhere in the middle of it like the pusher gyros we all are so familiar with that have in-line (cylinders) engines.

The only other solution is a three-gear PSRU like our buddy in France fabricated as a one-off for his YG3 conversion.

But three shafts, three gears, three sets of bearings = more vibration, more noise, more weight, more wasted power.

I went in another direction entirely, (and discovered that I could actually soften the hard start shocks typical of the YG3/4 at the same time by) using Hy-Vo chain technology much the same way Mr. Geschwender did back in the 80's when he was building PSRU's for big block Ford and Chevy aircraft power plant conversions. I only discovered Mr. G's work long after I'd already embarked down the path of building my Hy-Vo Silent Chain PSRUs.

The pusher PSRU is working great and it only sticks out 1/2 the distance of a Rotax gearbox arrangement, which allows a bigger prop of 2" more diameter. You don't grind down the output shaft, you leave it the length Yamaha intended it to be and it mates to that entire length inside the drive gear hub.

I've been flying with it since last summer and I am going to have the tractor (FW) PSRU ready just as soon as I finish up the last details left on a customer's gyro YG4 installation.
 
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NoWingsAttached

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My Mohawk GTI Apex adapters are selling well. Until I get more hours on the Silent Drive the gearboxes I am encouraging my customers to use at this time are Mohawk AK7 - a cousin of the Air Trikes SPG4 with several design changes specific to my adapters. Gears and bearings are the same, but the drive shaft is a different length and the rear housing has been machined to accept a ring collar to center it on my adapter. With 40 mm dia shaft and bearings, these gearboxes have been calculated to be expected to last 3-5x longer than the Rotax C. Rotax shaft and bearings are 25 mm. The other big hit on Rotax C life is the radius of the drive gear, which I think is 0.77", compared to 1" on the AK7.

I've sold some Rotax C adapters, so must keep a watchful eye on news from the field of any maintenance notices or issues. I have searched this forum for news of any known issues with Rotax C gearboxes and their related shaft couplings: RK400 clutches and Rotax Hardy disks. All I can find is what I had to post myself, first. I am having difficulty at this time discovering anything else that could help everyone out here, including myself, so far as it goes.
 
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B Hawley

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N954BH, Yamaha 130FI in Little Wing 5, Belt PSRU, 12 hrs on engine, in Northern California.

Has anyone had experiences with small mufflers, for 2" dia pipes, such as the Super Trap Brands?
[h=2]Such as the 443-2010, or the 422-20000?[/h] [h=2]I am looking for one that can be removed quickly. I have straight header exiting out of the bottom of the lower cowl section. Muffler must be removed to remove the lower cowl.[/h]
 

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NoWingsAttached

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The original engine was sold several years ago after I damaged the rotors, tail and mast following a blade strike while attempting an ill-fated take-off from a deserted tidal island, known as Pelican Island to locals in Savannah, and on the main public beach's location of Tybee Island.

The prop-protection break-away clutch in the prototype Silent Drive that I'd built and was using at the time saved the Hy-Vo chain drive and engine from prop strike damage.

I installed another RX1 2003 engine and was using it to test my MAC GT4 roller clutches when I inadvertently forgot to switch on the cooling fan on the radiator and burned up the motor last year.

A new, 2003 RX1 engine with only 300 miles on it was located, purchased and installed this year, and the gyro is undergoing a complete restoration with many new upgrades. I will post photos soon. It was not ready in time for Mentone 2020 so I didn't bother to drag it 12 hours up north, and my other two Yamaha Air Command builds, for customers, decided they would not go either.

The Wicked will fly again very soon, and I expect to take it to WRENS 2020 in September and Barry Days following in October.

UCFN8819 (640x640).jpg
 
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