Hi,
After having a prop strike while taxiing I choose a Hartzell Scimitar Voyager prop to go on my newly iraned IO-520 on my 185.

I asked the mechanic if he had the equipment to balance the new prop. He contacted me sever days later and sent a picture of the spinner.
I did not want him to balance it till I had put a few hours on the engine to begin the break-in process, but he did.
He sent a picture and I was very surprised on what he did. He mounted the balancing washers outside the spinner on two of the attach screws. When I questioned him about it he said he did not want to drill holes in the spinner backup plate.
As its the weekend I'll waite till Monday to call Hartzel but wanted some input from the group here first.
This certainly does not look like the proper way to attach weights.

I've balanced a number of props using the DynaVibe Classic but only on experimental aircraft. The tricky part is getting the correct weight in the correct location and that part has been done. The next step is to move the weights to the backplate which you do by increasing the weight proportionally to the decrease in radius but keeping the angle the same and then retesting.

The manual for my balancer states:
6.9 Move Final Weights to Permanent Mount
FAA or manufacturer procedures may require dynamic balance weights to be mounted in specific locations (generally not on external spinner bolts). If the permanent mounts differ in distance from the hub center compared to the mounting locations used during the dynamic balance process, then a simple calculation to determine the adjusted mass of the dynamic balance weights may be necessary.

I have attached a copy of the DynaVibe Classic balancer manual.

Harold,

Thank you for the reply and the manual.
As far as I know spinner washers are not a legal fix if on the outside.
I have done research and cannot get a definite answer for the Voyager but bet it is not allowed.
I am just very surprised he did it that way.

Tom

Several years ago, an IA buddy had recently bought a DynaVibe & he offered to balance my prop.
I didn't feel a huge improvement but the gizmo said he got it from .48 IPS down to .06.
(not sure just what IPS stands for?)
He replaced the spinner screws with longer ones where the weight needed to go,
and added some washers & locknuts on the inside diameter of the spinner backing plate.
Kind of a cobbled up mess IMHO,
and taking that assorted stuff off & reinstalling it all at the correct hole is a PITA when removing the spinner at annual time.
I don't like the idea of drilling holes in the backing plate, but as I recall that's how a buddy of mine's 180 was done.
It would sure be a lot cleaner installation, as well as less hassle at annual.

IPS = inches per second

The fact that he took a photo of that like he was proud of his work

You don’t need a manual to know that ain’t right


I would not be happy with that, but it seems the easy way to get er’ done

Reminds me of taking wheels and tires in to have it balanced and mounted, it was off a vintage car, I emailed the place prior to see if they could use coated weights on the INSIDE of the wheel, yes 100%. I drop off, come back and there are my wheels with the tires mounted, non coated weights right on the outside….sigh

Thankfully it was in emails and they fixed it, and only by dumb luck did they not scratch the wheels up

This is one of those “disappointed, but not surprised” type deals

Thank you all for the follow ups.
Monday I will give Hartzell a call. Up to this point I have been very pleased with his work.

Tom

FWIW here's a pic of a prop balancing weight on my buddy's 180.
And a clip from a discussion on the cessnaflyer.org website about attaching weights.

Thanks everyone for the help and advice.

I called Hartzell yesterday and talked to a tech on the issue. As I was explaining what was done, he interrupted my in mid sentence and said
"He did what" The tech said NO that is not the way to do it, period.
Tom

Putting the washers on the exterior of the spinner is something you do just to confirm that the weight in that location gives the machine desired results, before you go turning the spinner bulkhead into swiss cheese.

That said, balancing a new prop before flying a bit is kind of a waste of time. It takes some flying to break it in and let the centrifugal force push all the goo to its final location.

I often balance propellers when I annual airplanes. That is how we get the weights correct, for the final (permanent) install a hole, or holes, are drilled in the backplate; some backplates have holes already there. As previous posters have stated as the radius decreases the weight must increase. All of this information is in the manual.