We spend so much time ensuring that the props we use are properly balanced, then we cut and carve the plactic or metal spinner cap to fit the prop.

Does this in any way contribute to making the balanced prop unbalanced.

In a word, yes.

Balance the spinner too.

yes but since the spinner is so small in diameter the effect is minimal and not such a big problem on the average sport engine. go up in RPM like pylon racers or ducted fans and it becomes important.



dave

Curious - How do you balance your spinner?

One of my 2 1/2 inch Alum spiiners was off put it on my magnetic prop balancer ( great planes)I just drilled a series of small holes
in the back plate on the heavy side till I got it to balance

Enlarging the prop cutout can either take it further out of balance or help balance it. As you know you don't want the prop to touch the spinner in the cutout. How much clearance that you have is a little more ambigous. If the spinner isn't far out a little off all around the cutout may fix it.
If you drill holes in the back plate to balance it be sure that the cone attaches to the backing plate the same direction each time.

First you balance the backplate alone. It should require very little if any balancing, especially on alu spinners with machined backplates. If you have to drill a "series" of holes something is really out of whack. Check if the shaft hole is properly centered. I wouldn't use a spinner that has visual runout.
After the backplate is balanced properly, put on the cone, and rebalance the assembly. You can do this by removing material, or by adding material, or both. Adding material can be as little as a couple of drops of CA inside the cone, one the light side.

All:

[link=http://www.rcuniverse.com/forum/m_1115188/anchors_2357187/mpage_1/key_/anchor/tm.htm#2357187]Here's[/link] a good thread on balancing spinners.

Bill.

Yes, and after you've spent hours doing this, go out and get some rubber build up or a small chip on one side of the prop from your chicken stick or what ever and you'll need to start again. Yeah, like we all do that!

Bill,

Thanks for pointing me to that thread on spinner balancing.

I had never really given doing it much thought until yesterday, as having spent quite some time balancing a 12" new prop and then carving a plastic spinner cone to fit the prop, that the thought of it hit me.

Flyboy Dave's comments and picture illustrations in that thread takes all the mystery out of balancing spinners, and are very clear and straight forward.

The high point balancer from Bennet Built will hold a spinner in the outboard position for balancing. Works nice.

Enjoy,

Jim

Thanks!!!! I haven't been balancing them, but I have been kinda wondering about it. All questions answered!

And I don't plan to spend HOURS doing this either!

Here's a shot of a Tru-Turn spinner mounted in the over hang mode, plastic cones are done the same.

Regarding aluminum spinners and their near perfect balance out of the box, gentlemen, that's a lot of hooey.

I've never had a Tru-Turn that needed any attention, but on the other hand I've never had a "Spin-Rite" that didn't need a lot of attention. Haven't used the DB (Vortech) spinners so I can't say about them.

The 3 1/2" Spin-Rite on my US 120 had to have a lot of metal cut out of the back plate just to balance it, then the cone was way out also.

Ironically, the Du-Bro plastic spinners seem about the best, next to Tru-Turn. The Du-Bros I've checked have been close enough to run, but no others have been. All moderately to terribly out of balance.

Bill.