Yamaha RX1 Engines

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Posted

What is the oil temp like with the RX-1?

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Posted

It has an oil cooler integrated on the engine, and also a big external tank (dry sump system).

 I plan to mount the oil tank up front by the cowl Inlet holes so that it gets extra air flow. I have not yet heard of anyone who has had issues with high oil temp.

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Posted

I am running at 257F which is a little on the warm side.

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Posted (edited)

I am running at 257F which is a little on the warm side.

Sorry.. forgot who I was talking to (someome already running a yamaha!)

I plan to run full synthetic Mobil 1 0w40 which can tolerate higher temps and avoid thermal breakdown of the oil.  I wouldn't flinch at running 257F

 

Screenshot_2018-06-26-14-24-25.png

Edited by Yamma-Fox

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Posted

What's the consensus on the final weight of the Yamaha? 

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Posted

Any flight reports on the new gearbox yet?

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Posted

257 degrees is a lot hotter than Ive ever seen on my oil. If I remember currectly it runs 10 to 20 degrees hotter than the coolant. I would check your plumbing to your oil cooler. The yamaha oil cooler seems to do a pretty good job. No flight reports on the new Apex gearbox yet. I have switched gear manufactures and I awaiting another set of gears to test the clutch. The first set that the clutch was tested with showed no visual wear except on the sprag races. The hardness was no where near what I specified. The new gear shop, hardening shop and grinding shop are locally and I can check up on and control quality standards a lot easier. 

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Posted

Excellent! Thanks for the update.

Clark

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Posted

As far as the weight question. There are so many weight numbers. Like fire wall forward installed weight or engine and drive weight so im going to assume that when you say"final weight" your asking the weight with everything on it istalled on the plane. Mine come out to about 160 lbs. Thats with carbs exhaust bottles radiator ready to fly. So if your familiar with the weights of the 912 it is about 15 lbs heavier. 

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Posted

On the oil temp discussion,  i bet it also would make a huge difference where you measured it right?

In the tank or coming out the bottom must be a lot cooler than if you were taking it off a tapped sensor in the oil cooler bolt or at the oil test port above the #1 exhaust port. 

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Posted

True, im not sure how much cooler it would be at the oil cooler. I measured mine at the oil filter. 

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Posted (edited)

Teal contacted me today with a report that a pinion shaft bearing began to fail on a (appox 200 hr) Skytrax RX-1 running an RK-400 centrifugal clutch.  

This event is noteable because it is very similar to one other case where the same problem was encountered  (also a Skytrax RX-1 w/ RK400, but with approx 110 hrs).

Other noteable facts include:  

-  Both failures suffered NO powerloss.  The bearing began to give out but the rigidity of the RK-400 clutch (mounted on the PTO) helped keep the clutch drum and pinion shaft centered and the gears remained "meshed" and running.  It appears likely that at least one of these two gearboxes ran for a number of hours in the partially failed bearing condition.

The problem (in both cases) was detected during a subsequent preflight by noting some side to side play in the clutch drum.

-  Also noteable is that there are many other setups nearly identical to this one (centrifugal clutch with similar hrs of use) which have had NO problems, and also there have been no reported problems while running the rubber flex drive ("hardy disc").

******UPDATE****

Analysis is back from the Rotax service center on these two gearboxes.  It was determined that the latest gearbox was assembled incorrectly during a gear set change (see pic 2 posts down), and that both gearboxes had the pinion bolt come loose during operation.  (that bolt in the center of the pinion shaft, bolt head located in gearbox, going out through to the coupling that connects to the clutch drum / hary disk)

When that bolt came loose, the pinion shaft  apparently "rode up" the gear teeth and rammed against the outer pinion bearing (in outer case), loading it axially which in time caused the bearing to fail.  Also the gear wear pattern on the second (improperly assembled) gearbox had the large gear scraping the case cover and the pinion bearing race.  Wear marks showed that the two gears in that one only had about 50% tooth alignment.

So it looks like the problems here have been isolated to improper assembly and also more noteably from the pinion bolt coming loose, so a couple unofficial recommendations are suggested from the shop to users of the c gearbox:

The pinion shaft bolt should be cleaned thoroughly and red loctite used during final assembly. (torque is 212 in-lbs)

When you have the gearbox apart to that point, the axial clearance of the pinion shaft should be checked.  This clearance is critical to bearing life and gear engagement.  In the post below I'll reference the service manual excerpt on how to make this check.

Additionally anyone running the Rotax gearbox can also make an easy preflight check to determine that the pinion bearings are in good condition.  This is a simple procedure where you reach in the access / cooling hole and physically push on the drum / hardy disk.  There should be no detectable side to side movement.

 

Edited by Yamma-Fox
Edit for final analysis.

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Posted (edited)

Reference post above,  here is the axial clearance measurent screenshot from the manual, along with a description of how I found to do it in an easier way:

For anyone who wonders the procedure for checking Rotax C pinion shaft axial clearance, here is a copy, but I found it easier to simply add a number of shims (I put in like 4), install and torque pinion bolt, then set the case cover down (without gasket).  The proper gap IS the .4mm gasket, so I measured the case cover gap without the gasket and removed a number of shims that measured the same (or slightly more) than the gap.  

Then I double checked my measurement by doing it the way described in the manual.  For my box I had a .44mm clearance with zero shims. 

I also think it is important, during reassembly,  to triple check that you don't have too many shims in by checking that the case cover actually still will contact (without the gasket) the case.  This ensures that you didn't add too many shims and have a binding problem when you bolt the cover on.

I'll re-check that at about 30 hours after break-in and predict that I may need to add one shim at that time.

FB_IMG_1530546670112.jpg

Edited by Yamma-Fox

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Posted (edited)

For anyone who might be following, I did an update 2 posts up on the c box that had a problem.

And here's a pic of what was meant by "improperly assembled".  Absolutely amazing that the gears and gearbox held up to 140 hp for 200+ hours with the gears barely even meshing like that!!

 

FB_IMG_1531073664799.jpg

Edited by Yamma-Fox
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Posted

I had a similar situation were the pinion screw came undone.It came to my attention when doing an oil change as there was a lot of metal on the plug.The shim(shims?) had failed due to the hammering at idle,it had been loose for so long the screw had a flat spot worn in the threads from rattling around.We cleaned it up and had a few extra eyes look it over.there was no gear or bearing damage visible.An oil change was done at 10 and 20 hrs with no metal visable on the plug.These boxes are tough!      The only giveaway the problem in hind site was a rough idle below 2000rpm and the start was a little slower.

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Posted (edited)

Just incase any one is following this thread, and not the rest of them, I have a C gearbox, 3-1 ratio with about 200 hrs on it that I might sell.  Send me a PM if interested. JImChuk

Edited by 1avidflyer

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Posted

Easiest way is the "water trick".  Essentially you fill the clutch bolt hole with water, then find another bolt that has threads that match the larger threads in the center of the clutch (get a flashlight and you'll see them), wrap teflon tape on those threads, and thread it in....  the hydro pressure forces off clutch.

Here is a vid of one way to do it using a bolt from the sled.  I would weld the hole on the end of the bolt closed if I used that bolt, wrap teflon, tip engine up, fill water, thread bolt in, pressurize water... off comes clutch.

(And no that's not me in the video...  I'm a hell of a lot uglier than that)  :) 

 

OR you can just ask me for the tool.  I sell it to you, you use it, and then you send it back to me and I refund your money.  

 

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Posted

I am running at 257F which is a little on the warm side.

Sorry.. forgot who I was talking to (someome already running a yamaha!)

I plan to run full synthetic Mobil 1 0w40 which can tolerate higher temps and avoid thermal breakdown of the oil.  I wouldn't flinch at running 257F

 

Screenshot_2018-06-26-14-24-25.png

Hmm.  Ya know, NASCAR crews run 20w synth for time trial laps, then replace with 50w synth for the race.  I always ran 50w Mobil 1 in my GT1 turbo porsche when I was racing.  In the Yamaha motors I have never run anything but 5w-20 Mobil 1, changing oil every 25-30 hrs, and changing K&N oil filters every other oil change.  I have noticed that as the oil ages it does tend to disappear a bit more toward the end of that oil change cycle I use, perhaps using heavier oil would slow that down?  It isn't but an ounce here and there though, maybe 1/2 cup at most after 20 hrs.  

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Posted (edited)

But then, that motor was oil cooled, and racing temps hit 300°.  No Yamaha aircraft conversion should ever see those kind of grueling conditions, unless something is wrong.  I asked Steve Henry about his operating temps, water side, and he said he's never seen anything over 170-180°.  I use the idiot lights on the stock multi-function display, the only time it ever gets hot is sitting still doing tune ups.  So I started putting an electric fan over the radiators when I tune the motors.  All of the new cars run 20 weight synth.  I don't think running 50 weight synthetic is such a great idea for any Yamaha engine, in any temperature, so long as it has less than 1000 flight time hours on it.  Unless you plan on running it flat out all the time.  I guess then it might make sense.  I know of a couple of guys who run YG3s with shorty exhausts 3-into-1 into a can, no mid-range power to speak of, so they run WOT all the time.  Seems strange to me, but that's what they do.  Some people won't listen to reason when told the exhaust is a poor design and needs to be lengthened.  

Edited by Mohawk Aero

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Posted

Does anyone make an rx1 motor mount for mk iv to sell? 

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Posted

There's a guy in ND that could help with that.  Not sure where you are located?

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Posted

I'm in louisville ky. 

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Posted

I'm in louisville ky. 

The fella in ND is William Langford.  He has made up some FWF components for the Yamaha that fit the KF 4-7 and has offered to help with custom engine mounts.

Problem there for you obviously is about 1000 miles!

But dont be too intimidated with making your own custom mount.  I had not done it before and (with some help and a lot of time) was able to tackle it:

http://www.avidfoxflyers.com/index.php?/topic/5345-yamaha-genesis-rx-1-install-in-kitfox-5/&page=2

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