I think that I was as close as I ever will be to putting a drill bit into my forehead tonight trying to balance an aluminum prop spinner! Have an aluminum spinner that I trimmed for a 15x6 prop for a Saito 125.. Anyway, during the first part of the break in process I noticed that after leaning the top end out some, it would hit 10K rpm without much trouble.. So I went today and picked up a 16x6 to slow the motor down a bit. Anyway, now I have to retrim the spinner to get this larger prop in.. Not too much trouble here, but when I put the dang thing back on my top flight magnetic balancer I thought I was going to loose my mind.. I spent almost 2 hours trying to get that thing so that it wouldn't rotate at all.. I was drilling away a few metal filings at a time.. seemed like it would never just right! I did get it pretty close, but I wonder if that balancer is a bit overkill for these engines.. Seems like a piece of dust is almost enough to throw something off balance.. I guess I better steer away from bugs this year..

Anyway, question about spinners, props and washers.. On this 16.6 I put the backplate on first, then the prop, then a set of two washers, then the prop nut/ adapter nut.. It seems like the back of the prop is VERY close to touching the front face of my spinner backplate.. This wasn't such a close fit with the 15.6.. Can I put another washer behind my prop between the prop and the backplate to get a little more space? Not sure if the prop is supposed to be in contact with the backplate or not..

Thanks again!!

Use this balancer to balance spinners outboard the balancer. That is not between the stands. The Unique Over/Under Set-Up Option allows this. Also you can balance the 16-6 props outboard like this.
http://www3.towerhobbies.com/cgi-bin...&I=LXD712&P=ML

As long as the back of the propeller is not pressed against the back plate - it will be OK

If there is ANY clearance between the prop and the backing plate you will be fine. Washer? No. I'd use a layer of sandpaper or 2.

Ok.. I'll just leave it alone then, there is a tiny amount of clearance between the back of the prop and the spinner plate.. maybe 1mm.. I guess if things are going to "move" at all in flight the tendency would be for the prop to flex away from the spinner under an air load anyway.. Thanks for the replys guys..

For props and spinners on a 4-stroke (Or, for that matter, any engine that is not used for extreme speed) if it's close, it's good enough.

Especially since the spinner is very close to the center, it has little affect on vibration even if it is out of wack

Austin

that's good to hear... You can drive yourself nuts trying to get a spinner in "perfect" balance on one of those magnetic balancers.. I got it to the point that it would rotate on it's own VERY slowly.. started off falling to the heavy side quickly.. Finally said "well, this is gonna have to be good enough!"!

That's about right.

Even the metal prop/spinner retainers have a tendancy of shifting slightly each time you re-insert the spinner or you rotate them.

This lateral shift will throw off your attempts at balancing the spinner. It is not as dramatic with props which have a longer effective lever moment.

Check the spinner balance, then without removing it, rotate the metal retainer and check again. Frequently you'll find that the balance will shift this way.

Why can't the prop touch the spinner backplate?

It could over time cause the prop to split (shatter).

Austin

I guess I'm missing something or I've been doing it wrong I always put the spinner backplate against the engine thrust washer, then the prop and then the locknut(s), then any applicable adapter, then the cone.

I've never balanced a spinner, in fact Tru-turn states its not necessary.

While we are on the subject, I've never balanced a prop either, but don't ban me

Hill,

I probably didn't describe what I was talking about well enough.. My concern was that the actual back of the blades of the prop are almost touching the front face of the spinner backplate.. Obviously the back facing of the prop hub touches the backplate, but it actual blade is very close to it as well..

thanks fellas..

That's exactly what I always thought you meant.

I see, thanks for clarifying for me.