Thorp Air Command - T18.net

My airplane, not flying yet, has a Catto three blade prop' and a Lycoming iO-360-A1A engine. I read in the newsletters that the power pulses on the IO-360 are not good for prop's and some folks have added a damper of some sort??
Any advice appreciated, and also where do you get such a thing??
Speedbird 1.

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N872DD
200hp Lycoming

You'd be keeping your eye out for a "Landroll Dynamic Balancer". I had one on 66WT. Also had another that was just a steel ring that weighed 11.4 lbs and bolted to the flywheel.
They occasionally show up for sale on the Van's Classified site. As far as I know they are no longer being produced. I'm not sure if Cubes has any in his stockpile of parts, but it's worth a call.

T

Many thanks,
I have been looking on the RV site and see that a few of them use these devices with the bigger engines.
Having done my research and not finding too many on Thorps and Catto saying they are not necessary I think I will hold off until the first flight and see if is even necessary.
Speedbird 1.

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N872DD
200hp Lycoming

I would love to have them. The harmonic balancer I had on the Tigress did not work well. But the steel ring type works great. I got about +150rpm static on take off and the engine seemed to run smoother. I’ve tried several places to get them to make the steel ring type. So far, no luck. I recently found a new machine shop. They did some shearing for me. Turns out the owner is a big GA fan. Might give him a try.
Cubes

And it was manufactured by Mark Landoll. He is no longer in business.
Cubes

Thanks Cubes,
Looks like I am a dollar short and at least a day too late!!
Speedbird 1.

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N872DD
200hp Lycoming

Mark Landoll's device was described by Mark himself as primarily a dampener, and less a balancer. In fact, when I have dynamically balanced props with one of them installed the results were mixed, and frequently I would be able to balance the prop assembly better without a dampener installed than with one. I would typically actually see a greater amount of vibration on startup that sometimes took 30 or 45 seconds or more to "settle down", and the vibration level was sometimes unstable with throttle changes. I'm not a big fan of them, but for some larger engines especially, they may give some suppression of the strong power "pulses". In my opinion, a better choice for those of us with lightweight wood or composite props especially, is a simple steel ring bolted to the ring gear. I had one on my O-320 with a wood prop that weighed only 11 lbs. I think the ring weighed somewhere around 13 lbs. As others have mentioned, I too measured a greater RPM at any particular throttle setting, which resulted in greater speed. In my case, the increase was approximately 50 rpm at full-throttle. I think that if you used a high-speed camera you could see that there is acceleration of the propeller assembly with every power pulse, and deceleration in between pulses. The extra mass of the ring gives greater rotational inertia, minimizing those events and resulting in slightly greater rpm. I also noted a smoother idle at a lower rpm. That, if you have a wood prop, along with dynamically balancing the whole assembly is the way to go, IMHO.

There is a somewhat similar, and simpler device that you can buy today from a company called Balance Masters. They consist of a steel disk with a formed cavity around the perimeter that contains a plastic tube with mercury inside. I've done some careful tests with one on Rotax engines, and again I'm not a big fan. There is definitely potential improvement with badly out-of-balance propellers, but I've obtained much better results with a good dynamic balance job alone. Interestingly, the propeller couldn't be balanced as well when done along with the Balance Master device installed. Similar "out-of-balance" was noted on initial engine start, for approximately 30 seconds to a minute before things stabilized.

So again, FWIW, my advice is to spend the money on a good dynamic balancing job if possible.

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John Evens
Arvada, Colorado
T-18 N71JE (sold)
Kitfox 7 SS N27JE

Thanks John,
Having read all the good advice both here and on the RV site I think I will wait and see how it works when I fly, then maybe look for a solid ring version.
Speedbird 1.

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N872DD
200hp Lycoming

My specialty was dynamic balancing for over 20 years. I've had more customers apply then remove those ring balancers than keep them. I think John is giving good advice here. If you have any balancing questions sock it to me. John, you and I have met many years back, and I bought one of your cabin heat valves. I didn't get around to installing it, but when I see it in my shop I always think that thing is beautiful. Don

Thank you, Don... I appreciate it.

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John Evens
Arvada, Colorado
T-18 N71JE (sold)
Kitfox 7 SS N27JE