End Play when hand turning prop

[vwglenn]

Sure thing. Still, adding shims when the end play is out of whack on a running engine is not fixing anything.

Can you explain further? Isn't adding shims the correct way to control end play? If you have an assembled engine that has too much end play how would you fix it other than adding shims? What else needs to be fixed?

The stress that excessive end play can put on the case/bearings/crank after a fair amount of use could cause some wear and adding shims would just hide a problem that will still be there. You could do it and it might solve the end play issue but the wear on those parts is already present and will probably get worse. It's much safer to get in there and see what's going on. Bearings are cheap. Cases, cranks, and engine failures cost a little more money.

I talked to my buddy (A&P and fellow VW geek) about this last night and he reminded me that the engine is designed to handle the horizontal loads of the spinning assembly of the engine. When you sling a prop on the front and 600+ pounds of plane behind it, you're putting a different kind of load on the engine then it was designed to handle. Adding a shim to the rear when the bearing saddles are already worn or the bearings themselves have had a hard fore/aft load put on them will just build more slop into the bottom end of the engine. It might run for 1000 hours like that but more likely it'll pull those shims into the case and, in a few hours, you'll have the same problem or much worse.

Now if this was a fresh rebuild on the engine I would consider just shiming it to get it right but I might still have a little concern from that voice in the back of my head that something wasn't right in there if it required excess shims.

[jfuerst]

I finally pulled the engine!

Leading up to this I went through the original build manual for the engine (which came with the aircraft) and noticed that every step in the manual had a check mark next to the step indicating that it had been completed, that is every step except the page on measuring the shims, including a blank space where the quick "computation" that would say how many shims I should expect... I had some hope!

It turns out there is a single shim for between .007" and .0085" (depending on how you measure it...)

As part of the engine pull I had to drained the oil. There was 9 hrs on this oil change and when checking from the dipstick it looked crystal clear. However when draining it I swear that there was a slight hot chocolate colored swirl in the oil. I tried fishing for metal shavings with a magnet but nothing stuck... Does anyone know what the bearings are made out of? Brass?

I learned a valuable lesson here. I need to have a dedicated oil drain pan for my airplane, and it needs to be CLEAN enough to eat off of before draining the oil. I have used this pan to change the oil in my tractor and because of that it has a dirty black perma-stain that may be contaminating the oil's color as it sits in the pan....Rookie mistake.....Lesson learned....

I imagine that at this point I need to pull the engine apart and investigate further. Not really prepared for that, but considering I can't pull over on the side of the road if things really go bad.... Well we all know the deal.

If a bearing has been chewed up is that something that is fixed by replacing bearings, or (as I'm assuming) what might be some of the contributing factors to start researching?

[MichaelFarley56]

So you're saying there was only one shim between your flywheel and crankshaft? Personally, I don't see how you would be able to achieve the 0.003-0.006" play as called for in the manual with less than 3 shims. If there was only one, that's probably where your issue lies.

Fixing things will ultimately be up to you, but a wise idea may very well be go ahead and split the case to inspect the case and crankshaft for excessive wear and/or damage. It's a little time consuming but this will give you the opportunity to do two things: first, you can replace all crankshaft and camshaft bearings with brand new ones, and second, you can accurately measure your crank end play to determine the correct number of shims you'll need during the rebuild.

I suppose you may be able to fix this by simply adding additional shims as needed for proper end play; given the heavy duty 'racing style' parts our engines use, you may very well be okay by simply adding shims and reinstalling your engine. If your engine has very little time on I would feel slightly more comfortable with this, but it's still a big roll of the dice. If you decide to go this route I believe you can purchase an inexpensive end play measuring tool from most online VW shops so you can determine needed shim thickness without splitting the case. If you do this however, I strongly recommend you at least keep an eye on the end play and make sure the play doesn't get any worse as you fly.

In the end, it's up to you. I can tell you that, if you decide on a complete tear down and rebuild, it really doesn't take long at all. You could easily tear it down, inspect parts, and rebuild in a short amount of time.

Sorry I can't give you a specific answer, but ultimately it will be your call. Good luck and let us know what you decide!

[rizzz]

If a bearing has been chewed up is that something that is fixed by replacing bearings, or (as I'm assuming) what might be some of the contributing factors to start researching?

Unfortunately, if indeed a bearing has spun, the damage is likely to extend to the case.
If that has indeed happened all is not lost, the case can probably machined to accept a bearing with a larger outer diameter, this not uncommon on these cases.

[Gripdana]

If it is any help. I just finished building my Aerovee and it was easy to do following the manual. It has been 35 years since I rebuilt a VW engine.

[kmacht]

The risk of running with excessive end play isn't a spun bearing. It is damage to the forward and aft thrust faces on the case. The get beat on from the crank constantly moving forward and aft. Before you pull the case apart I would recommend measuring the end play without any shims and see if it is even possible to get to under .006 with three shims. This will give you a better idea as to what kind of damage if any there is to the thrust surfaces of the case.

Keith
#554

[Gripdana]

I just had a thought. Your engine may have had the end play section of the build done incorrectly. When I set my end play I was very careful make sure the crank was pushed back when measured. If there is only one shim in there I would suspect that that was not done.

[maishathelion]

Extremely common when rebuilding a VW is Aline boring the case,We used to ro on new cases just to have a heavier bearing[Fvee racing] and on even older cases that did not have cam bearings so cam bearings could be installed.Any good VW shop should should be able to A L I G N
bore most commonly [and incorrectly]called line boring.

[vwglenn]

So there was only one shim in there? I recommend, like before, you break down the engine and have a look at the bearings in there. As stated previously, the case can be machined to accept larger crank bearings at minimal cost. Best case scenario is you have no wear issues and you can just put the engine back together and do the end play properly. Then you'll have piece of mind knowing it was done right.

The reason there are supposed to be three shims in there and the end play is set the way it is is because the shims act like bearings. The slight amount of end play allows an oil film to build up between them and reduce friction as well as act like a cushion to reduce wear. With any less than three shims installed, that film wont build up and the fore/aft load on the crank will be excessive and everything will wear prematurely.

[jfuerst]

Finished pulling the engine apart and there are a few things I am worried about:

1) The crank has some wear at the bearing by the prop hub and some grooves on the actual prop hub presumably due to some extra slop in the bearing (next issue), though I am unsure what the hub must have rubbed on as the cowling is in good shape and being fiberglass should be softer than the hub is...


Better detail of the groove on the crank. The high and lows match the bearing inside surfaces:


2) There is excessive play (of course) in the bearing fit of something like .006"-.010" as detailed in this video:
http://jordanfuerst.com/Waiex/bearingPlay.mp4

Surprisingly I do not believe that the case needs to be align bored, but I have found a shop about 30 minutes from my home that will do that for me. What is the appropriate measure to be taken with the crank?

3) I have a few burned valves as detailed here:

Obviously I will need to replace them but I am worried that there seems to be cracks between the valve seats:

and here:


For the record Sonex has been very responsive and I will assemble another email to them requesting advice. That being said, I have received a number of PMs for people wanting to know the final outcome and some that worry they are in the same boat, while I think the valve issue is separate from the end-play issue I figure I may as well keep the document going for the next Sonex owner that is doing his 1am search to see how much work he has ahead :lol:

I'm interested in suggestions for:
1) Fixing the crank (or must I replace it?) - Ideas on why this is the only bearing with issues? Oil supply problem?
2) Valves - Well, anything I should know?
3) Cracked valve seats? - The web seems split on if it's that big of a deal, with many saying to continue on as normal, or fix it, or replace it.... Personally I have never heard of a crack being acceptable till I looked into the VW websites.
4) Align bore even if the case seems to measure okay?
5) Anything else?