# Dynamic prop balancer accelerometer

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#### WurlyBird

##### Well-Known Member
I have been collecting parts in order to make some Arduino based accessories for my plane and a couple days a new idea popped into my head, here is the sequence of events. As I mentioned I am collecting sensors to attempt to make a glass panel for my plane. Before anyone gets upset about the safety aspect or the reliability of such a set up, I am doing it to learn more about Arduino, sensors, programming, and I just want to see if I can. My plane is VFR only and such a panel would be for entertainment only (I want to make a panel that resembles the glass panel in my helicopter :nervous and all instruments installed already will stay that way. On another website guys have been talking about Dyna Vibe prop balancers which I have seen mentioned before but never paid any attention to based solely on sticker shock. I watched a video of how they work and it is pretty **** simple. Light bulb. All you need is an accelerometer and a means of tracking and timing the prop, light, hall sensor, etc. The hard part would be the software, a.k.a. a new challenge. It would not be hard to permanently mount both of these devices which could give you the ability to monitor the health of the prop as well as get balance information while actually at cruise and not just at cruise RPM which would give you a little more accurate results.

So here is the question, what range accelerometer would be needed for this application?

I made a quick calculation using some arbitrary and excessive numbers and came up with about 7g which seems kinda low. This is probably an over simplified estimate and here is how I came up with it. If the engine vibrates 5mm (like I said excessive) at 2500 rpm and it is accelerating at a continuous rate, where d=(1/2)at^2, then a=2(d/t^2), so a=2(.005m/(.012s)^2)=69.4m/s^2. Anyone have any experience or knowledge about a setup like this?

#### TFF

##### Well-Known Member
Making an panel is cool; why would someone care? Making a balancer is cool too. I have a DSS box at work for the helicopters and I put it on props sometimes. Props dont go out of balance unless you do something to them. Carrying all the time might not be needed. but to see the trends would be good.

#### WurlyBird

##### Well-Known Member
Making an panel is cool; why would someone care?
Some people are safety gurus, and I could see where a post like this could look like one of those many posts we have all read where someone is trying to make a fully digital, super high tech, jet fighter, VTOL, vehicle of the future, but doing it with zero background, on a milk money budget and for all the wrong reasons. And those kinds of ideas need to be waved off. So I just wanted to preface the idea.

As far as having it permanently mounted, if it looks like I could actually get this to work it is going to cost me about \$30 in sensors and a couple of ounces of weight. There is a spot on my mimic panel where rotor rpm would normally be displayed so I could always fill the spot with prop rpm, maybe displayed in a percentage, he he cool. The IPS and position of the vibe could be displayed only on a discrete page when desired. From smoothing rotor blades I know that aerodynamic imbalances and inertial imbalances can affect one another and even manifest as the other so having it permanently mounted would give me that added benefit of seeing the vibrations in more then just a static thrust/cruise power setting.

#### TFF

##### Well-Known Member
I would build a heatsink collar for the transducer. I dont like how hot they get when mounted to an engine.