one way bearing (sprag) lubricant (again)

[rhodesengr]

I thought I understood the OWB (aka sprag) lubrication issue but now I am not so sure.

I have a 700N DFC converted to gasser. I experienced a powertrain slip after just a few flights. The engine revved up suddenly while I lost blade power. The clutch looks ok so that leaves the OWB. I have searched and read just about everything I can find on this issue. Plus, I was also involved in considerable discussion about OWB issues in the gasser area related to the Whiplash I had before this DFC. Most of the newer threads suggest geting the KDE OWB housing and I have one on order. However, after opening up my OWB last night, it is not obvious that the Align outer race sleeve slipped. It may have slipped but it is not hand loose at this point. So I can't entirely rule out lube issues. I had followed a common bit of advice and had lubed the OWB (after cleaning) with ATF since numerous threads and even the sprag manufacturer (GMN) suggest ATF. On inpsection, i found that the lube in the OWB area had turned grey and was no longer the light red color of ATF. I am thinking that grease from the upper and lower radial bearings leaks out and mixes with the ATF resulting in the grey stuff. I am just wondering if this mixture no longer works properly for the sprag. On top of that, I found a thread on HF last night where the OP tried ATF and claims that it caused slipping that he didn't have before. So now I am not so sure what to use.

So, I'd like to hear from anyone that has cleaned out their Trex 700 OWB sprag, did it look all grey, what you used to re-lube, and what if any problems or success you had since cleaning. I am also curious if anyone knows what lube Align uses when they assemble their OWB. It seems like some sort of clear grease (like Tri Flow synthetic).

Note I plan to cross post this in the 700E area so I can get as much input as possible so hopefully that won't bother anyone.

[jiminator]

I've been using Tri-Flow grease in all my OWB's except the Whip gasser. I also just installed the KDE unit in my 700n. I think I had between 15 to 20 gallons thru my ship since the last maintenance on the OWB and it was fine albeit pretty dirty. Cleaned it all up and applied some more TF, a light coating. I just coat my finger with it and roll the bearing around until everything looks nicely covered.

I'm not a very hard flyer but I did experience slippage with the stock bearing housing. Only have flown 4 flights with the KDE in place, so far its been good. Jim

[rhodesengr]

Originally Posted by jiminator

I'm not a very hard flyer but I did experience slippage with the stock bearing housing. Only have flown 4 flights with the KDE in place, so far its been good. Jim

Thanks for the reply Jim. So just to be clear, you now have Tri Flow Grease in your 700N sprag housing? This stuff
http://www.triflowlubricants.com/Tri...ic_Grease.html
and not the oil.

I was not doing anything drastic when I had my slip. I was just doing some mild pitch pumps and suddenly the engine revved way up and I lost blade power.

I'll be very interested how your power train holds up now that you have the KDE housing in there. I should have mine running again with that setup by this weekend.

[jiminator]

Yep. That's the stuff. Hopefully I'll get out this week and put a few tanks thru it. I was surprised when I had slippage. Didn't know what was happening until another local flyer clued me in. Found more info on HF and since my bird was due for maintenance popped the KDE in. My last tank I flew a few full collective figure 8's with big banked turns and some full power loops. Not a trace of slipping. My tune was way rich which was weird because before I replaced the bearing housing I thought it was better than it was.

I also replaced the straight cut gears with the slant versions maybe that had something to do with it.

Maybe the torque of the gas motor has something to do with the slippage too.

I've also been using TF on my Fury 55's owb with no issues for 2 years.

[rhodesengr]

Originally Posted by jiminator

Didn't know what was happening until another local flyer clued me in.

So what was happening, i.e. how did you know it was slipping? As for me, I heard a sharp increase in RPM. I had that happen once before on my other gasser but it turned out that clutch had failed. So I thought the clutch had failed on my DFC gasser. The clutch looks ok though. Since repairing the clutch on my much older 700N gasser, I have not had any slips in the power train. My DFC gasser failed after just a few flights.

When you opened the sprag housing, was it obvious that the outer sleeve was loose?

[jiminator]

Pretty much what you described, an increase in rpm. Maybe not as sharp as yours but you could definitely hear it. I couldn't physically make it slip when I pulled it apart. it wasn't something obvious when I inspected it.

Have you tried the Lynx gas clutch in any of your gassers?

[rhodesengr]

Originally Posted by jiminator

Have you tried the Lynx gas clutch in any of your gassers?

Yes, both my 700N and 700N DFC gassers have the Lynx clutch. It has a bigger OD than the Align clutch and is way too tight in a new bell. There are claims that you can "just run it in" but I claim you can't. When I bought my 700N gasser used and the clutch soon failed, I bought the Lynx clutch, a new lined bell, discovered the fit issue and sanded it. Its worked fine ever since.

When I built my 700 N DFC from all new parts, I tried the run-in approach using a drill motor to turn the assembly first on the bench and then mounted to the model. It never got loose enough so I ended up going back and sanding it anyway. I am wondering if I may have damaged the OWB assembly during my attempts to run-in the clutch by using the drill motor to turn the main shaft as this couple back to the clutch via the OWB.

This whole clutch business is why I went towards to the Whiplash which used the Zenoah clutch only to discover that they has mis-designed their OWB by putting it on the pinion size and using a sprag with too low an RPM rating. This is all posted in gory detail in the gasser forum.

I am trying to fix my DFC gasser which I bought to replace my Whiplash but I am eyeing the Goblin gasser which has been around for a bit now and seems to be establishing a track record.

[jiminator]

I've fortunately had no issues yet with my Whip but last flight I noticed a little bobble kind of like a cyclic shake, so maybe I'm going to just buy that sprag and replace it before the "nah-nahs" start. Ounce of prevention....

[rhodesengr]

The standard oem part for the Whiplash was the FE422Z. You'll see back in the gasser forum that GMN suggested I try the FE422M. After ordering an FE422M, I could not get some other parts I needed so that's when i switched over to the Align DFC conversion.

I sold my 422M to one of the other Whiplash guys and a few others have bought them and there has been nothing but good feedback about switching to the FE422M. So Hopefully that is the part you plan to get.

So the Align 700's use something equivalent to an FE423Z. It may in fact be the 423Z but I don't see the numbers marked on it. That means us Align 700 guys might benefit from an FE423M. Just something I realized in the last few days.

The GMN parts can be ordered from Motion Industries.

[jiminator]

Thanks for the info. The part # you posted for the Whip is the direction I'm going.

[rhodesengr]

My parts came in last night including a new Align OWB so I could get a new sprag and the KDE housing. The Align sprag comes in the housing with a clear grease which is probably the same stuff they sell in the little tubes. I cleaned it off and put it in the KDE housing with some ATF. I don't have any firm basis for choosing the ATF over the Align clear grease. I was hoping to have had more feedback through these threads.

One thing I noticed is the sprag seemed too tight in the KDE housing if I also used the thin washer that comes in the Align housing. KDE shows it as optional but it seemed to make the sprag bind. Even with out the washer it seems a little tight.

Well a little more work before I can flight test but for now the sprag, gears and shaft are assembled and installed.