SonexBuilders.net

It took me some days to find the courage to post this, it still hurts looking back, but here goes.

I’ve had another serious problem with my VW engine, this weekend I started the thing for the first time and it ran really rough.
I was not able to get any power at all out of it so I took the plane back into my garage to investigate. Anyway, here’s a short video:

https://www.dropbox.com/s/1jsdsm4f0d6qy ... 0.mp4?dl=0
(This is a link to my dropbox so this won’t be on there forever, download a copy if you want to keep it for reference).

Sounds like a timing issue?

Unfortunately, that was the good news.
The bad news however is that after this I had damage, my Force One prop hub bearing had spun. It was moving along with the crank.
I couldn’t believe it, I have to rebuild this engine a second time now (others may have followed my previous incident on the VW aircraft forum).
Nothing I can do about, I took the engine off the plane and opened it up, dreading to find out what damage was done inside.
Anyway, here’s what it looks like, the F1 hub & bearing are toast, the case also took damage at the dowel pin insert. Everything else appears to be intact.




How could this have happened, was the rough running (possible timing issue) the cause? Did the bearing get such a nasty kick it got smashed out of its seating?
I contacted Scott at Hummel engines and he seems to think it would rather be either an oil delivery problem to the F1 bearing or the bearing was just too tight, I’ll need to investigate.

I’m also talking Marty at Great Plains.

Again I must say, both Scott at Hummel and Marty at GP are great guys. Excellent customer service.
Even though my engine is a bit of a mixture of both their products they are both keen to help me just resolve the issue rather than try to sell me stuff (which is what commonly would happen here in Australia).

Scott seems to think the case could perhaps be salvaged by machining out the dowel pin hole and use a “stepped” dowel pin (larger on one side) instead. A machine shop can make one if necessary.
I’m not quite convinced yet I’m comfortable with that idea but I’ll take it to a machine shop and see what they say about this. Worst case I might throw away the case and get a new one altogether as well (again!).
As said the F1 hub and bearing are going into the bin as well but the crank should be good, I’ve taken that to the local engineering shop to get the hub pressed off, I’ll know for sure if it’s good once I get it back.

Painful, very, very, very painful…
I was so close to moving my plane to the airport, this was the last thing that had to be done…
Luckily my wife and I are going on a nice tropical holiday next week to celebrate our 10Y marriage anniversary so I can take some time to away from this as my head is not in a good place for the moment.

Sorry to hear that. Not helpful, but on a positive note, the paint scheme looks great.

-Brett

ouch. Thank you for posting this!

Sorry to hear that Michael. I wouldn't have thought oil would be the problem. The assembly lube would have lasted more then 45 seconds. Could the dowel have been too short.

Hi Michael.

What a bummer. I hope you get this is sorted and get it in the air soon. Also that paint job looks great.

Sorry, I cant help with the engine problem.

Steve
Sonex 892

Michael,

I am very sorry to hear about your engine troubles.

Did you prime your oil pressure before your first start? This would be taking out the spark plugs and turning the engine with the starter for several seconds to develop oil pressure.

I think Great Plane's suggestion to use the stepped dowel pin would be a solid fix for the dowel pin case issue. The dowel pins are just there to hold the bearing in place. They should not normally have much load on them as the oil provides the low friction barrier required for the spinning crank.

After I built my engine I immediately started it after mounting it on the airplane. I then started it every other month or so. I wanted to make sure it would run properly before I went too far. Plus it was motivating to see and hear it run.

Jake

Shoot Michael, I'm really sorry to hear this. I'm also surprised to see this on a freshly rebuilt engine.

Best of luck getting it fixed and back together in short order! Keep us up to date.

Good luck!

Listening to the engine run on your video, I would suspect a fuel issue rather than timing or spark. Timing and spark are almost always yes or no, go or no go, whereas fuel supply issues are usually haphazard at best. Based on my far too many years experience with gas engines of all types and sizes, I can't see where the poorly running engine would contribute to the crank problems. I would look closely at the bearing tolerance/clearances and oil supply. As someone suggested, you must have oil pressure within a few seconds of firing it up. If not, cooked bearings will follow very quickly.
Please keep up posted as you work through this. Jerry Loeffelbein, Sonex N1320X, AeroVe.

The pump was primed and I was getting good oil pressure. So I'm not sure what has happened.
The #4 restrictor plug was removed as well from the case so I should have been getting plenty of oil to the bearing and after opening up the case it did look like oil did make it to the bearing so I'm not totally sold on the "no oil" theory either.

Here's another theory:
As mentioned before the engine was rebuilt once already even before it first ran because I had a crack in the original case (very sad story as the original case was a rare AS21 single relief Panzer case).
Anyway, I bought a new case already pre-machined for an F1 prop hub, however, reading the installation instructions now here http://www.greatplainsas.com/if1brg.html it would suggest the case has to be machined to each F1 prop hub bearing individually? The instructions tell you to measure the bearing and machine accordingly rather than giving you exact dimensions for the machining.
If this is indeed the case then that would almost certainly explain what has happened, the case was just not exactly the right fit for the F1 bearing.

I’ll talk to Marty at GP about this.

Ok, I found out what made the bearing seize.
This is very embarrassing but perhaps others will learn from this so I'll share this anyway.

You can actually see the problem if you look closely at the first picture.
For those who want a challenge see if you can spot the problem before reading on.

Did you spot it?
No?
Well, here's a hint: what hole got elongated? Is that the dowel pin hole?

Nope, that's the oil feed hole!!!!!!!!!!
My dowel pin was in the wrong hole, blocking oil to the bearing.
That would do it!

When I dropped the crank shaft assembly into the case, the bearing must have rotated out of alignment and the wrong hole lined up with the dowel pin so no oil was making it to the bearing.
I can see that this mistake would be easier to make with the F1 hub/bearing than it would be when using the original bearing like on the AeroVee, because there is also a forward-backward misalignment that would be noticed on the original bearing.
The F1 bearing overhangs this part of the case on both sides so it's a bit harder to spot.
Still, a rookie mistake, very embarrassing and also very costly.

At least I know what happened.