RE: Problems balancing wood props??
 

I was looking at that too. He certainly took off a lot of material. I think that he had the same issue that started me thinking about the Windsor balancer - the prop shaft hole was drilled off center.

Also, if you watched W8YE's video in Post 9, in the first 20 seconds you can see where the prop tips don't track when you rotate it - that tells me that the drilled prop shaft hole is off center.

Presuming that the wood or composite is relatively homogeneous throughout the prop, re-drilling a trued-up prop shaft hole would cure these problems. Of course, this presumes that you're using a drill press with the table square to the drill bit, a flat-bottomed drill (or a mill) and the prop is anchored so that it doesn't wander.

I wonder if something like the jigs for that Windsor balancer could be duplicated?

Bob

RE: Problems balancing wood props??
 

surely if you have 1 Blade thicker than the other one Blades will pull more Air than the other

RE: Problems balancing wood props??
 

This is not that the hole is off center, it is not perpendicular(square) to the back face of the mounting area of the prop.

"surely if you have 1 Blade thicker than the other one Blades will pull more Air than the other "

Thickness has little to do with it, the airfoil is on the front of the prop and the backside is flat.
If the prop were to have a symetrical or semi symetrical airfoil it would make a difference.
The airfoil does the work.
Read up on your aerodynamics.

And don't call me surely http://www.rcuniverse.com/forum/js/f...wink_smile.gif

Happy flying, Oscar

RE: Problems balancing wood props??
 

I currently use a DuBro prop balancer for simple balancing and a home made jig andset ofdrill bushings for props that have the hole off center.
Ihave considered making a drill/mill jig like the Windsor to sell.
But looking at the price of a DuBro balancer ($26.00) a device like the Windsor is going to cost $60.00 or more.
It's not suprising that Windsor discontinued it probably due to poor sales.

Happy flying, Oscar

RE: Problems balancing wood props??
 

A few years ago you could buy just the windsor offset jig with your choice of bushings/drills

They may still have some if you call and ask?

RE: Problems balancing wood props??
 

Oscar, is correct about the tracking. I always check the tracking AFTER the blade has been installed onto the prop shaft of the engine. True, a prop with an out of alignment hole will not track properly, but the tracking will be most affected by the faces of the prop hub. I always balance the my props first, then mount on an engine (can be in a plane or on a test stand) to check the tracking. The force of the prop nut will alighn the blades in relationship to the hub faces and override the fit of the prop hole. Even with a tight fitting prop hole the prop nut and washers will force the blades to be pushed into alighnment with the hub. Try tracking your prop on a prop balancer, and when you are satisfied it is tracking true, put it on an engine and check again. You will be suprised to find that many times the tracking changes.

Tom

RE: Problems balancing wood props??
 

Jim and Tom,

Both good points... I'll check that out at Windsor and that's a good point about the prop face...

Bob

RE: Problems balancing wood props??
 

Tom is right. The final engine installation is what counts. Does this mean more work? Of course it does, but if you are the kind of person who cares about blade tracking and balance it is worth it to you.

RE: Problems balancing wood props??
 

...and it all starts with a straight hole drilled in the center of the prop.. :)

RE: Problems balancing wood props??
 

Rarely!
That is why you need a good pitch gage and prop balancer no matter what the props material is. Remember to true the blade pitch on each blade by sanding the back of the hub, Then make the front of the hub parallel to the back of the hub. Balance the prop as if it was a disk not just a beam. A balanced prop will stop in the balancer at any position, 360°. If it always stops with the blade horizontal you have a heavy hub! The prop is out of balance.

As for dynamic balancing (dual plane) it is not an issue as both planes (front and back) of the prop are relatively close to each other.

With the magic of todays smart cell phone one can find an App that uses the phone's accelerometers to measure the vibration of your running setup. With a little experimentation (changing the prop location relative to the piston or spinner) you can lower the vibration even more. The result is more power to the prop and a longer airframe life.

Just some ideas.

All the best,
Konrad

1st picture are the tools of the trade, 2nd is a balanced hand made prop, 3rd is an out of balance prop just put on the balancer, 4th is showing an APC prop after balancing the hub.

RE: Problems balancing wood props??
 

Konrad, the issue that we've been discussing is how to balance a prop with an off-center of angled hole. That has to be fixed first before anything else.

The thrust of this thread is to find a Windsor Prop Balancer which will let you re-center the hole.

Have you seen any in your travels???

Bob

RE: Problems balancing wood props??
 

That wasn't the scope of your first post. You were concerned about wood props.

The hole (Axis) position thing is applicable to any rotating disk, wood, steel or composite. It can be dealt with by moving the hole and subsequent bushing the bore back to size. Another just as viable method is balancing the disk. You would still need to do this even if moving the bore.
The drilled holes in the APC composite prop are notorious for being out of position. See earlier photo. That Top Flight wood pylon prop has a heavy hub 90° to the blade axis. Is this from a miss positioned hole or a variation in the woods density? The engine's crankshaft wouldn't know.

If the back side surface favors one blade more than the other a pitch gage like what I have shown will show this by bringing to light that one blade has more pitch than the other and/or that one tip is above the table higher than the other. As most prop bores have a clearance of about 0.10 mm the squareness of the bore to the prop clamping surfaces can be off a bit as the hubs aren't very thick. Yes, the squarer the better but the primary surfaces to datum the props pitch and tip tracking are the hub faces.

The main point of my post is to treat the prop as a disk and not a beam when balancing them.

All the best,
Konrad

RE: Problems balancing wood props??
 

[quote]ORIGINAL: Konrad

"That wasn't the scope of your first post. You were concerned about wood props. "






By all means, let's be sure that the language of each post ts perfectly clear before moving to the search for a Windsor Balancer or similar device.

Are we quite sure there are no spelling issues in the last dozen or so posts that need to be cleared up before we move on? Any of Newton's principles in dispute?

jess

RE: Problems balancing wood props??
 

Thanks JessieJ. :D :) :D

Next time I'll use the spellchecker too... :) Do they have a Grammar Organizer on here as well?

I just don't want to let the discussion get derailed.

Bob

RE: Problems balancing wood props??
 

Somebody will peek in and de-derail things if we need it.

RE: Problems balancing wood props??
 

I bet somebody will peek in and de-derail things if we need it.

RE: Problems balancing wood props??
 

Yup, blw, that's for sure.

If we can't find one of those Windsor prop setups, I am contemplating building a hub setup. I have a small machine shop at my disposal. Parts could be lathe-turned, so it wouldn't be something that could be made by the average modeler. With everything symmetrical, the hub design would (should?) be balanced... at least in theory :D but we all know how that goes.

Even with buying the drill bushings and precision axle, it would be cheaper than the original cost of the Windsor balancer, though a lot more trouble to make. It could be mounted on my Dubro balancer...

Oskartek, back in post 28 you made a comment about my my mis-statement of the hole being off-center, you said that it was not perpendicular. I meant to comment before that yes, you were correct. That's what I meant to say - I should have edited my post better before hitting the Send button. This is a belated Thanks for stating that.

Bob

RE: Problems balancing wood props??
 

[quote]ORIGINAL: jessiej


I'd be the last person to comment about english spelling and grammar! [X(]:eek:

All the best,

Konrad or should it be Conrad?

RE: Problems balancing wood props??
 

Regarding the SIG balancer, the plane balancing part is very nice, but I prefer the Dubro for balancing props because it is more adaptable to larger props and there seems to be less friction in the bearings.