Balance Master

[Shadowrider]

Joe on the NR prop I got better results with balance master. Others have got better results with a dynamic balance. Dynamic balancing is mostly science and partially an art form. If you have never dynamic balanced a prop and will be doing it by yourself, I say just run the balance master. Maybe John will sell you his?

[jrevens]

With the early dynamic balance equipment that was available 30 years ago, i.e. from Chadwick-Helmuth, there was some “art” involved in my experience. With modern technology, not so much. I don’t have any Dyna-Vibe experience, but with my 20 year old ACES machine it’s all science. I’ve given my Balance Master to a friend to try on his Mod. IV. If he doesn’t like it I’d be happy to sell it.

[Av8r3400]

Having done both on my plane, I now have a Balance Master ring on it.

I can not quantify anything scientifically the way John did, but my "seat-o-the-pants" meter sure liked the results of the ring better.

[Frontier Fox]

I appreciate the responses from everyone.

With a new Rotax 912iS it makes no sense to me to install a Balance Master on the flywheel. It would void the warranty and it seems that the engine should be balanced to begin with. However, I would expect some imbalance within the prop hub and blades. That’s a lot of mass spinning a 70”+ circumstance. So I’m leaning towards the Balance Master for its simplicity.

I’m probably about three or four weeks from my first start so I’ve got some time to make a decision.

John, if your friend does not want your Balance Master let me know, I may want it.

Joe

[jiott]

I don't have any problem with the idea of a balance ring that automatically distributes its balance weights AS IT IS SPINNING. What bothers me a whole lot is the initial start-up when the weight has all fallen to the bottom overnight and it must be redistributed on start-up. Even if it only takes a couple of seconds (some reports on this thread indicate it may take 30 seconds) that is too much time to have what may be a very out-of-balance condition on EVERY start-up. If your engine rubber, especially the carb sockets, is getting older and approaching replacement time, a couple of hard shakes on each start-up could easily cause a crack. We also know that hard shaking or pulses is bad for the gearbox/clutches. I personally feel much better with a good dynamic balance; its not that hard to do or that expensive to have it done. Just my opinion.

[Shadowrider]

I think these rotax engines experience more force on the rubber mounts when they are shutdown than starting up. Still can’t get used to the prop just stopping.

[jrevens]

I think these rotax engines experience more force on the rubber mounts when they are shutdown than starting up. Still can’t get used to the prop just stopping.

Dustin,

I think it was DesertFox4 who turned me on to the technique I use to shut-down - from 2500 RPM, simultaneously pull throttle smoothly to full idle while turning off ignition (in my case, 2 toggle switches). The result for me is a rather smooth shut-down... not at all bad. Not like an engine without a PSRU, but still pretty good.

[Av8r3400]

I don't have any problem with the idea of a balance ring that automatically distributes its balance weights AS IT IS SPINNING. What bothers me a whole lot is the initial start-up when the weight has all fallen to the bottom overnight and it must be redistributed on start-up. Even if it only takes a couple of seconds (some reports on this thread indicate it may take 30 seconds) that is too much time to have what may be a very out-of-balance condition on EVERY start-up. If your engine rubber, especially the carb sockets, is getting older and approaching replacement time, a couple of hard shakes on each start-up could easily cause a crack. We also know that hard shaking or pulses is bad for the gearbox/clutches. I personally feel much better with a good dynamic balance; its not that hard to do or that expensive to have it done. Just my opinion.

I don't know where the 30 seconds indication came from but I can observe my engine is running smooth before the CDI modules kick the timing to the "run" position. That may be 3 seconds.

[jiott]

The 30 second reference was from John Evans post #18:
"I allowed time for things to "settle down" before each reading, and observed that with the BM it took a minimum of 30 sec. to 1 min. (sometimes considerably longer) to reach the best balance condition. There was no delay without the BM."

Very likely John was saying it took that long to reach a very fine balance condition. I doubt he meant that there was major shaking for that long. I will bow out of this discussion at this point because I have no actual experience with the Balance Master. I was just expressing my opinion after reading what others have posted and my own thinking on the subject.

[Shadowrider]

Thanks John. I have been doing 2000rpm. I will try 2500rpm to see if it’s any better. It’s like a main bearing is dragging and on its way out. Kind of comical how a rotax stops. Still getting used to it.

As far as the BM being out of balance on startup... I bet the mercury is spun out on the crank before the engine is idling smooth.