MooneyMitch Posted January 12, 2012 Report Posted January 12, 2012 Unless I've missed this in the forum search, there hasn't been any discussion on this topic. So, any opinions or experiences would be most welcome please. Quote
N33GG Posted January 12, 2012 Report Posted January 12, 2012 Ditto... especially if anyone has had success with 3 blade props. Quote
lamont337 Posted January 12, 2012 Report Posted January 12, 2012 No experience with a 3 blade, but a bunch of us from my local EAA chapter (1300 in Henderson, NV) pitched in to buy a dynamic prop balancer. Those of us that pitched in get free use of it for life - $50 for anyone else I think. One of the guys made a bracket that works for all of the Lycomings (360 series) that we've tried so far, and also one for the rotax guys. My initial vibration level started off much higher than normal so I'm going to have my prop statically balanced before I do any more adjusting, but I was still able to cut my IPS (inches per second) by about 40 percent. Noticable at all RPMs. Pics below are from a members RV7A, which was easier because he could but the weights on his starter ring. My spinner had to come off to add hardware. Didn't take pics of my own unfortunately. Vid below explanes the process much better than I can in a paragraph: http://www.rpxtech.com/rpxweb/Dynavibe.asp Quote
gregwatts Posted January 12, 2012 Report Posted January 12, 2012 Just had my 2 blade done at Palm Beach Propeller and I can tell the difference. The airplane probably notices it even more. I recommend it! Quote
jrwilson Posted January 13, 2012 Report Posted January 13, 2012 I'm having my 3 blade done on my 63 C right now. The shop said there was a large improvement according to the machine, but they were at the limit of the weight they could add. Still waiting for the fuel/manifold gauge overhaul, so haven't been able to test fly it yet to see if the difference is noticable. I'll let you guys know next week when I fly it. Quote
PTK Posted January 13, 2012 Report Posted January 13, 2012 Is there a recommended frequency to rebalance the prop? Does anyone know? I had mine balanced a few years ago at 2400 RPM. Do I need to do it again? Thanks. Quote
Jeff_S Posted January 13, 2012 Report Posted January 13, 2012 I had my 3-blade balanced, although once we got started the tech indicated that it was already pretty good. As I recall, his initial reading showed the IPS number to be ~.1, which he said was pretty close to turboprop standards. But since I was paying him anyway he worked to get it down to .07 by adding a screw and washer set to the the bulkhead. It was a little disconcerting watching him drill into a perfectly good piece of metal but I just put my trust in his experience and so far all has worked out well. BTW...no idea what "IPS" stands for but it's some measure of vibration. Quote
1964-M20E Posted January 13, 2012 Report Posted January 13, 2012 IPS is inches per second. You are looking at acceleration to determine vibration. The other way to measure vibration is to use proximity probes on the bearings which measure the displacement of the shaft that is turning with respect to the bearing. Proximity probes are more expensive and require a port to be drilled and taped on the bearing with the probe inserted and carefully positioned within thousandths of an inch to the shaft not practical for us. This process is generally used on large industrial equipment. Side topic the EI G3 has the capability to mount an acceleration type vibration probe on the engine permanently. Quote
PTK Posted January 13, 2012 Report Posted January 13, 2012 IPS stands for inches/second which technically is a velocity vector. A vector has magnitude and direction. In contrast to inches/ second ^2 (i.e. inches per second squared or per second x second) which is an acceleration unit. This velocity is the speed (magnitude) the prop reaches as it passes through (vector) the center of the range of its displacement as it rotates. Velocity is the quantity measured because it measures vibration independent of RPM. The perfectly dynamically balanced prop will have zero IPS or zero velocity through the center of the range of its displacement and 100% of its rotational velocity in the direction of rotation. In other words the velocity vector for displacement is zero in a perfectly dynamically balanced prop. We never of course attain this ideal level of zero IPS but they do come very close! Quote
N601RX Posted January 13, 2012 Report Posted January 13, 2012 I had my internal engine parts dynamically balanced while they were being overhauled. The crankshaft was off by about 10 grams. When they finished it was less than .5 grams. Quote
jetdriven Posted January 13, 2012 Report Posted January 13, 2012 OUrs was just balance by Walt Aronow in Dallas. Top notch work. 200$. Our IPS started at 0.395 and ended at 0.053. Huge difference in noise, vibration, and harshness. We just flew it back from Key West to Houston in 8 hours, and arrived fresh enough to go out that night. The vibration and noise is a lot less at 2500 RPM now. Worth it for sure Walt@expaircraft.com www.expaircraft.com Quote
jrwilson Posted February 15, 2012 Report Posted February 15, 2012 Quote: jrwilson I'm having my 3 blade done on my 63 C right now. The shop said there was a large improvement according to the machine, but they were at the limit of the weight they could add. Still waiting for the fuel/manifold gauge overhaul, so haven't been able to test fly it yet to see if the difference is noticable. I'll let you guys know next week when I fly it. Quote
MooneyMitch Posted February 15, 2012 Author Report Posted February 15, 2012 We're on the schedule for this procedure for the E model. Looking forward to the results. Thank you all for posting your information, thoughts and results. Quote
bd32322 Posted February 15, 2012 Report Posted February 15, 2012 when did you guys realize that you need to balance your prop? Gauges vibrating and not readable? Any indications you used? Or there is no way to tell unless I take it to the prop shop? I just generally accept that a piston engined airplane will vibrate like crazy. What I think is smooth enough may not be smooth however Quote
MooneyMitch Posted February 15, 2012 Author Report Posted February 15, 2012 I've known about the procedure for many years, just never followed through with having it done. It appears to be a relatively inexpensive way to improve the aircraft so why not. Quote
lamont337 Posted February 15, 2012 Report Posted February 15, 2012 Quote: bd32322 when did you guys realize that you need to balance your prop? Gauges vibrating and not readable? Any indications you used? Or there is no way to tell unless I take it to the prop shop? I just generally accept that a piston engined airplane will vibrate like crazy. What I think is smooth enough may not be smooth however Quote
MooneyMitch Posted February 15, 2012 Author Report Posted February 15, 2012 lamont337 Your Mooney is gorgeous! Quote
Vref Posted February 16, 2012 Report Posted February 16, 2012 This is on my list also, I found a service company using a ACES Pro balancer... Quote
bd32322 Posted February 16, 2012 Report Posted February 16, 2012 Quote: lamont337 If you have an Iphone and $5 to burn, there's an app that uses the phones internal accelerometer to record and plot vibrations.See link below. One of our guys set it on his dash to record the before and after results during flight. Surprisingly accurate and I can only assume you can find a similar app for android phones. http://www.macworld.com/appguide/app.html?id=67886&expand=false Quote
John Pleisse Posted February 16, 2012 Report Posted February 16, 2012 Quote: bd32322 when did you guys realize that you need to balance your prop? Gauges vibrating and not readable? Any indications you used? Or there is no way to tell unless I take it to the prop shop? I just generally accept that a piston engined airplane will vibrate like crazy. What I think is smooth enough may not be smooth however Quote
lamont337 Posted February 17, 2012 Report Posted February 17, 2012 Mitch: Thanks! But don't get too close or you'll see how bad the paint is faded... bd32322: Wish I did, but I never actually used the app myself. I'll go ahead and add it though since I'm still curious. Unfortunately I don't think I'll be back in the air until at least the middle of next week. Quote
n6773v Posted February 17, 2012 Report Posted February 17, 2012 I just added the "vibration" app to my ipad - will give it a try this weekend and see what kind of information it provides. Quote
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