balancing spinners and props
 

Hi, my problem is balancing spinners and props. I have two balances: the Top Flite magnetic balance and the Du-Bro balance. I'm finding it very difficult to arrive at a good balance. Please, folks, will you look at my method and suggest better ways or improvements.

I find the Top Flite magnetic balance excellent; but too sensitive and unable to balance a spinner without drilling a hole in the spinner nose. So I am concentrating on the Du-Bro. In the configuration I have with all the weight hanging over one side, see photo, it is not very consistent. So I am using a very crude statistical method.

Since there is distortion of the spinner and its back plate when screwed together, the assembly, I think, should be balanced together. My object is to chase the lightest parts through repeated tests, adding small balls of plasticine to the backplate at the indicated point after each test. When and if I am satisfied with the balance, I will drill small holes in the backplate directly opposite to the plasticine balls and remove the plasticine.

The backplate is marked into 12 segments just like a clock. I spin the spinner gently clockwise or anti-clockwise with the 12 o'clock marker at 12:00. It will stop with this marker somewhere else; perhaps the 3 o'clock marker will now be at the 12:00 position. As a result the 3 o'clock marker show the lightest point in this spin. As my configuration gives inconsistent results, I need to repeat the spin 10 times clockwise and 10 times anti-clockwise.

In the chart image, the sequence 11, 8, 4, 1 ... says where it stopped after each spin. 11 means it stopped with the 11 o'clock marker at the 12:00 position.. In the chart, I draw a blob for each of the numbers from the 10 + 10 spins. The result in the chart suggests that the lightest point in this test is between 8 and 9 o'clock. So I will add a small ball of plasticine and run it all again to see what happens.

Any and all advice is very welcome.
Best wishes to all
Mike

RE: balancing spinners and props
 

You need to adjust the Dubro to get the spindle level

Also you need to be careful with your spindle cones because in many applications the points of the cones will touch and will not hold your prop or spinner firmly. In this situation you have to turn the movable cone around so it's flat side is against the part to be balanced.

I balanced several weed whacker and chainsaw flywheels on Dubro and High Point balancers and that presented problems

The TopFlite is not practical for anything over 11-6

RE: balancing spinners and props
 

Hi. An update on my balancing efforts.
What I wanted was an effective and systematic procedure to balance spinners and props both now and in the future. What I have done is probably good enough; although still miles away from what is possible with the equipment whether Du-Bro or Top Flite. I suppose I will get better with more time and experience of the tools.

Anyway, I enclose two images, one shows the chart of the spinner still unbalanced and the other the probably adequate balance.
Best wishes to all
Mike

RE: balancing spinners and props
 

PS the holes I drilled directly opposite the red marks (where I added weights to find the balance points) were 1/16".

RE: balancing spinners and props
 

Mike, I have a High Point balancer. Over time, I discovered that just getting the balance 'close' is good enough. Because the balancer is SO SENSITIVE it is an exercise in frustration to get the balance 'perfect'. You will be chasing the perfect balance for hours, always getting close, but not exact. I think the darned thing is sensitive enough to detect 1/100 of a gram!

RE: balancing spinners and props
 

The High Point balancer is available from B & B Specialties for $39.95. It is made along the lines of the Dubro balancer.
The older High Points have a steel base and are all metal. The newer High Points have a plastic base but the rest is all metal
The Dubro has a plastic base as well as other plastic parts

There's little difference in the ability of the newer High Points and newer Dubros. They are made on the same engineering principles and will perform the same.

There is also a Windsor mad by MAS but the spindle is made for a specific purpose. The balancer is not as useful as the others.

RE: balancing spinners and props
 

Many thanks for your kind replies
Mike

RE: balancing spinners and props
 

Hi. I've got my new (balanced!) spinner and prop running on the test bench. Yes, there does seem to be a significant reduction in vibration. Touching the needle valve before was unpleasant; now it doesn't seem to be so.

So, what can be done to reduce vibration still further?

Will putting some absorbent or damping material between the motor and its mount work? Any ideas?

Best wishes to all
Mike

RE: balancing spinners and props
 

Vibration dampening mounts are available that significantly reduce the vibration of the plane

However, these mounts often cause problems with the engine timing and operation.

the solution would be a stiff vibration absorption mount that is a compromise with being mounted almost rigid

RE: balancing spinners and props
 

wBye, thank you.

With my OS .65LA, what sort of engine timing or operations could I expect?

Mike

RE: balancing spinners and props
 

If the mount lets the engine jump around excessively expect mixture problems with you have it correct on the ground but it is vastly different in the air etc.

The engine you have is a pretty easy going one. I would just mount it and fly - enjoy yourself