Hi Steve Have read the posts about possible causes to the vibration on your engine. I would like to do a bit of speculation and make some suggestions if I may. Must stress that I do not have any experience with airplane component balancing but do have lots of industrial experience on especially things like fans and other rotors.
If no obvious defects in the engine can be found please check the prop flange and bolts. Have a mag-particle test (or any other NDT) done on the hub/flange. Special attention to the key-way if you have one. It is usually the first place to fail under load but has the uncanny way of closing up again as soon as the load is removed. Can be checked using a strobe with the engine running without the spinner and cowl in place so as to see the actual prop-hub in motion. Not sure about your setup, N/A if you have a taper mount on the crank, as it would have departed long ago if that was the case! Do you have a retaining bolt for the flange at the front of the crank? You would possibly have seen fretting and/or wear on the crank under the hub/flange if it was loose! Did you remove the prop-flange? I take it there were no indications on the flange, bolts and/or prop of chafing, indicating looseness?! Is the prop a plain laminated wood with a clear see-through finish or has it got some kind of reinforcing cover that can not be seen through? The reason asking is that there could be a lamination problem that also only shows under load. I suggest that you borrow a prop that is known to run smoothly and install it on your plane if the roughness continues after the engine rebuild and all other things have been checked. Please do all the testing on the ground and don't go flying until 100% sure that all is ok. Would hate not to see the interesting flight reports any more!! Best regards and good-luck with the fault finding. Wanna-bee Ivan Miller ----- Original Message ----- From: "Steve Glover" <[email protected]> To: "KRnet" <[email protected]> Sent: Friday, April 15, 2005 4:17 AM Subject: KR> Correction on Crank > Hi Netter's, > > Well, It appears I had spoken too soon. All initial indications pointed to > a broken crank on the VW. We pulled the engine down and did not see > anything unusual. I took the crank over to a well known machine shop in the > area and had it magnafluxed and dye glowed. Zip, zilch, nada.... No cracks > anywhere. Now we are at a total loss for any explanation of the vibration. > We will recheck the prop for balance but I think it was too severe of > vibration for that. Besides, once it was repaired, refinished, and > balanced, it ran really smooth. > > I apologize for the false info. Now I have no idea what could have caused > the problem. Both ignitions were checked with the same results on both. > The heads and valves looked fine after disassembly. Carb functioned properly > as far as acceleration. I am using a Revflow which has not given me any > trouble in 200 hours. If anyone has any ides, I'm listening. We are > putting the engine back together and I will fly it until the Corvair is > ready. Hopefully whatever the anomaly was, with the rebuild (Again), it > will be gone. > > Steve Glover > KR-2 N902G > AJO, Ca > <[email protected]> > > > > _______________________________________ > Search the KRnet Archives at http://www.maddyhome.com/krsrch/index.jsp > to UNsubscribe from KRnet, send a message to [email protected] > please see other KRnet info at http://www.krnet.org/info.html
