SonexBuilders.net

Hello everyone - I am a new Sonex legacy owner as of 3 weeks ago. It has an Aerovee 2.1 (non-turbo) with 40 hours since new - the previous owner had this new engine built by an A&P. There have been a few minor issues that I have worked through but I believe I have come upon a larger one that I would appreciate some guidance on.

Last week I noticed some play in the drive shaft when I was repositioning the plane. I took a video https://youtube.com/shorts/yJZBBHb3Fj0?si=xlhzZVbRmB4PEpBH and sent it to tech support at Sonex. The response was this:

The link below is a video that deals with setting crankshaft end play along with page 17 in the manual. What I see in your video appears to be excessive.
The AeroVee manual calls out .006" as the maximum end play.
Normal end play is within .003 to .006 inches. End play is set by the number and thickness
of shims that are placed between the thrust bearing and flywheel. Three shims maximum.

I assume he meant three shims minimum.

I did find this thread on the forum https://sonexbuilders.net/viewtopic.php?f=7&t=1556&hilit=shaft+end+play&start=30 from several years ago but none of the links are working any longer.

The engine has 40 hours on it. From what I have read in the above link and what I have been told from Sonex I believe my plan of action will be as follows.

1. Use a dial gauge to measure the current end play. Subtract .003" from that to determine how much more thickness in shims I will need to add.
2. Pull the engine off of the accessory plate.
3. Remove the gland nut. It sounds like this will take a considerable about of force. Should I remove the prop and attach a 2x4 so that I will have the leverage I need?
4. Measure the shims that are currently installed. Swap them for the correct combination of 3-5 shims for what I need.
5. Reverse the process.

Is there anything that I should watch out for that isn't in the installation manual?

How much time would you expect this to take a novice to complete? I do have decent mechanical sense and was able to successfully rebuild the font suspension of my 1980 MGB after watching numerous Youtube videos. That said - working on engines is all new to me.

Thank you for any help!

Hey Rodger,
Welcome to the forum! KBUU is really close to C77.

Check out my thread on torquing the gland nut:
viewtopic.php?f=7&t=7577

I would recommend a 2x4 in place of the prop, and a setup similar to what we used. You will need a 250 ft-lb torque wrench from somewhere, either borrow or go to Harbor freight. Leave the accessory plate on the engine mount and remove the 4 bolts that hold the case to the mount. The worst part of the job will be the R&R of the engine.

You don't need to take the prop off. Secure the motor to your bench in any way that you like and use this tool,

https://www.amazon.com/Universal-Flywhe ... hdGY&psc=1

to immobilize the flywheel while removing the gland nut. It only fits one way on our flywheels. I always used an impact driver to remove the gland nut and it came off with no problem. But you do need a BIG torque wrench to get the required install spec. I never removed the prop for this job. You will use the same technique if you replace the main seal in the future. (I hear they leak sometimes)

You will need to pull the flywheel off after removing the gland nut. When you go to put it back on make sure you use the absolute minimum amount of sealant you can. Too much and it will screw up your endplay again. Now that I think of it the rear main seal has to come out as well to put the new shims in. You will want a new one as they are cheap and difficult to remove without damaging.

Keith
#554

I measured the end play between the engine and prop with a dial gauge: .0188" so I'll need .015-.012" more in shims. I'm going to strive for .014" in additional shims. Too bad the shim pack doesn't come with that thin of shim - I'll have to measure what is currently in there once I pull the engine off.

I'll have the torque wrench and nut tomorrow so today I'll just be taking everything apart.

Thanks for the tips so far. I ordered the flywheel immobilizer that Pappas suggested.

Bryan - what do you mean by R&R? I like the 2x4 on the fly wheel to counter the force - being able to keep the engine on the hoist instead of setting it on the ground solves one problem.

Remove and replace. We had one 2x4 bolted to the case and one on the prop hub. With 2 people easy to do on the hoist that way.

Hi Rodger,

I am at 57C, I have a 250 LB torque wrench that you can borrow. I also recall using a 2X4 on the prop hub when tightening the gland nut. I am on the road quite often for work but I can assist when I am available if you desire.

Update

I was able to get everything taken apart and discovered there were four shims in place - just as builder's assembly notes had stated.

Shockingly, two of the shims were deformed and mangled. The shim closest to the flywheel looks as if it has been crushed in a hydraulic press and worn to be egg-shaped. The fourth shim looks like a hydraulic hammer came down on it multiple times. The middle two shms were stuck together (I thought it was just one shim until closer inspection) but mostly in good condition.

I believe the engine was constructed properly but something happened to define the shims after installation. I've sent photos and video to Sonex if they have seen something like this before. I met a guy at my airport that had constructed an aerovee and worked on several others before - he was gobsmacked to see the condition of the shims. The contact area of both the flywheel and case look normal to both of us.

I would much rather figure out what caused this rather than replacing the shims and hoping it all turns out ok!

Pictures and videos didn't truly show the extent of the deformation but here they are.

Shim 1- closest to flywheel
https://youtu.be/-dx72TUndXE?si=fdjC2qAF3K2nInWh

Shim 2 - closest to case
https://youtu.be/P50_7W7QnWU?si=gX-2qk_iOr6CmQMW

Wow, interested to hear what Sonex says. Thanks for posting.

The tech at Sonex has no idea how this could have happened to the shims. Not really the kind of thing I want to hear.

I was given the contact for Joe Norris a while ago so I reached out to him (the guy in the assembly videos for anyone who doesn't recognize the name). Really nice and helpful guy by the way. He has never seen this situation before. His best guess was that there was oil starvation early on which led to high friction -> heat -> deformation. Emphasis on guess as he doesn't know the history of the engine.

I don't see how a bearing inside the case could cause this.

My only other plausible hypothesis is that there is some runout on the bearing surface of the flywheel. I'm going to have the metals teacher at my school (where I work) stick the flywheel on a lathe and check with a dial indicator on Friday.

When it's said and done I might replace the shims and watch very closely to see what happens. Possibly to the extent of pulling the engine and pulling off the flywheel in 10 more hours to visually inspect the new shim's condition. Too bad I can't get a borescope in there!