The day out at Shoreham was a bit of a learning curve, I was asked to Balance both Peter & Rami’s aircraft.
It’s the first time I have worked off site and not had everything set up in the hangar before we started, it became apparent that working on the top of the wing was not a good idea as it set up errors in the weighting of the balance weights and probably resulted in an extra run before we got the optimum balance solution.
The one thing that both Peter & Rami have noticed is a marked reduction in vibration, the next aircraft I am going to look at is a DA42 that is regularly cracking exhaust pipes. If the exhaust cracking is a vibration issue this could save the owner a considerable amount of money.
Using the Dynavibe Classic, I have found the android app “Triangle Calculator” a useful aid instead having to plot accurately on a polar chart.
The box which A&C used just tells you where to put the weights (angle relative to the “top” prop blade – the one which had the optical reflector tape on it) and how many grams each should be.
You also first tell it the angles at which there are existing holes (from previous balancing attempts) in the prop flange, so one doesn’t end up with a flange full of holes.
There is no reason to fit stuff different to what the machine says it should be, but for some reason one often needs 1 more iteration.
The big thing I found was that the prop had to have oil in it, as if for going flying. Also the little scale which comes with the balancer kit (for weighing the bolts and washers) must be on an accurately horizontal surface (not on a wing, which is where everybody puts it) 
Reducing down to sub 0.1ips will be noticeable, especially if the previous reading is above 0.2. My new whirlwind prop started at 0.28ips and I got it down to 0.08 with a Dynavibe classic – I need to spend some more time on it to improve this further but it’s already nice and smooth in flight.
I chatted with the designer of the Dynavibe at Aero Friedrichshafen this year and he gave me some tips, a useful one being to start with 50 grams per IPS. This got me down to a good reading on the first attempt at adding weight and only another couple of weights were required after that.
My Dynavibe is available to anyone who cares to visit.. it’s important to have a good sensor securing point in the front of the engine, preferably just behind the front bearing. A longer crankcase bolt sometimes helps.
Or, if visiting Jockistan with a capable aircraft, come to Glenswinton.
We have a couple of Dynavibe kits here. The improvement on small helicopters and Lyc 4-cylinder airplanes is well worth an hour or so of owner/mechanic time.
There were persistent vibration issues with 3B props – in the TB20 context it was the Hartzell one. So I insisted on getting dynamic prop balancing done on my TB20 when it was brand new. They started with 1.5ips (which is pretty bad) and got it down to some fraction of that. It was a firm in Exeter – no doubt long gone. I handed over the bank draft for the second 50% of the payment for the plane on the return flight
Anyone interested in getting this done – contact A_and_C.
YAK_18_Propeller_Analysis_ms_pdf
Yes, I bought a prop balancer, they give a meaningful improvement!
