Any suggestions as to where to put the weights on the PA30 spinner back plate assy ?
Thanks Tom c.

Tom,

I'm real sensitive about this because folks just want to drill into the backplate or the starter wheel and these parts are expensive and difficult to replace. Back plates used to fail a lot on twins ... Hartzell makes locations designed to add weights at the hub - however, prop balancers might have to interpolate to figure out the weight and location. I check to make sure the prop balancer has the Hartzell style weights

It is simply a no-go for me to have them installed at the balancer's convenience at the expense of my twin's parts.

You will likely get other opinions.

The balancing weights should be mounted on the prop hub not the backing plate. You won't like the cost, up to $800, to replace the backing plate when it cracks because of the balance weights.

Tom,

Before you balance - be sure to check the lord mounts for flexibility and tight to spec 450-500 inch pounds

Balance using the holes in the ring gear. Don't throuw weight on the backing plate, like others said, they will crack, as will the spinners.
-Zach

Pat,Bernard,Zach,
Thanks again for your input,Pat a mechanic put new Barry mounts on my PA30C 30 hours ago some of the vibration went away but I still get what I consider unusual vibrations in the climb or the decent with the correct power settings bill Turley has the plane we're going to check the torque on the mounts Bills experience with the Barry mounts is they are to hard & do not dampen out the vibration enough, Zach the props have 60 hrs on them overhauled by sensenich propeller Bill knows to put the weights on the ring gear as I did on my last PA30 (took three trys to get it right)so I know what a smooth 320 feels like, after reading about & experienceing screw up mechanics Now I'm wondering if its "possible" to put the props on wrong or what to check for? we'll be going over everything the props were balanced by sensenich but NOTon the airplane since they were installed.

Thanks Tom C

Tom,

Yes, Props can be put on wrong. A past ICS officer's twin had q-tips put on incorrectly - took a long time to figure it out.

I found the Hartzell prop manual fascinating for its many permutations of how to put which prop on. As an example the K2U prop takes different torques on some of the bolts. The offsets on the spinners were interesting too.

BTW a prop balancer can put a probe on the back end of the engine to check its vibration also - that's how the vastly out of torque spec Lord mounts were found on my twin - long story which I have told before ... now at each annual I have the torques checked on the mounts. As I've said before - I'm no mechanic but I do learn by checkbook and the expereince has a tendency to stick with me.

I also ask shops to provide me with a printout of the before and after vibration numbers.

Pat
I'll keep you posted on the mounts & props in about ten days I wonder what our check books would look like without ICS?

Tom c.

Tom,

Mine would be much flatter without the help of ICS and our members