how do you balance a prop ive seen the stand looking device that the prop fits into but how does it work and how often should it be done how important is it to do this

the heavy blade drops so you remove material from that blade till they stay horizontal (2 blades).ever drive a car with unbalanced front tires and have them wear funny and the steering wheel shake?that is what an unbalanced prop does to the airframe.

Some people don't balance props in the 40 size engine range and only on bigger stuff. I balance all mine, it helps reduce vibration and an unbalanced prop can actually cause alot of vibration.
To balance a prop you either add weight to the light side or remove weight from the heavy side or a combination of the two.
Remove weight by sanding lightly on the back side of the prop.
Add weight by painting the tips of the prop.
There are other methods and others will chime in.

they work by telling you what the heaver side of the prop is. it is very important to balance props, if not done it can ruin your motor and or plane. it should be done when ever you put a new one on

Here is a low budget balancer idea that is easy to build.
Buy a great planes finger balancer for less than 5 bucks. steal your kids stereo speaker magnets. (you deserve the peace and quiet!)
knock together a 3 piece wood frame that will hold the magnets 12 inches above the base of the wood stucture. It should also hold the magnets 1/32'' wider than the finger balancer... just use the TLAR method ...you know That Looks About Right. the magnetic field will hold the balancer up but one side will not touch the magnet you can also glue a piece of THIN plastic to the magnets for additional friction reduction. It worked for me until I bought a ready made one at a sale.

I have one of those balancers that you hold between your fingers. It seems to work well.

I was surprised to discover that most new props need balancing. It reduces vibration significantly.

Dave

If a prop need balancing, I will lightly sand the backside of the heavy blade to get the balance close. Then I lightly spray blue paint onto the backside of the light blade. It doesn't take a heavy coat to do the job, and if the backside of one blade of a prop is blue, I KNOW I balanced it. [8D]

yes you should balance all props before you put them on

Yup, it's worthwhile to check the balance of every new prop. If nothing more, you catch the few that actually are out of balance.

Most of the reinforced synthetics nowadays are going to be very good. You may never find one that is bad. But I have. So I check 'em all.

And all the wooden ones should be checked. More of them need balancing. And some, I simply take back to the LHS. They don't mind, 'cause they say you don't need to balance props nowadays.

ALWAYS check the balance of a new prop. When I'm buying props, I carry a Dubro teeter balancer in my pocket. I test each prop right there in the store. If the prop swings GENTLY to one side, I'll buy it. If it slams down on the counter, I reject it.

I NEVER sand a prop to balance it. Although this CAN be done with wood props, I'd NEVER recommend doing it to a composite prop. It may create strees scratches that may cause unexpected failure.

I spray a light mist of clear poly-u on the front of the light blade until it balances. A quick baking in the oven at 200 for 30 minutes dries it nicely.

Dr.1

I spray the back of the light side of the prop with thin coats of clear Lustercote. I let it dry in between each time I attempt to balance the prop so the part that evaporates is gone. This will give you a correct reading. I continue to do this until it's balanced.

Just my method,

Gibbs

Well, I guess I'm going to be the odd one out then. (At least until Minnflyer chimes in here, because I know that both of us do the same thing). I don't really balance props. I check them when I first get them to see if they are grossly out of balance. If they are then I discard them (actually will try to get my money back if possible). If they're not way out of balance I put them on the plane and fly it. I know that many are going to talk about the "massive" vibrations that will be produced and such. But in reality, as long as the props aren't way out of balance (which aren't used in the first place) the vibrations are going to be minimal at the level of of our engines. And for beginners in this forum it's my opinion that balancing props is a waste of time. Why? Because the very first time the tip of that prop touches the ground/runway it's going to be out of balance again anyway. And if you stop to think about how many times a training pilots does touch the prop to the ground you'll see what I mean about it not being worth the hassle. Heck, most beginners would be pulling the prop off and re-balancing it every flight. Small strikes are not big deal for props, but if a "chunk" of the prop is knocked out then the prop should be replaced immediately. Please don't get me wrong, if people want to balance props then there is nothing wrong with it. But at this level of flying I feel it's not worth the effort and I don't worry about it. And I don't feel it wears out engines or airframes either, as I have engines and planes with hundreds of flights on them with no problems at all. Anyway, that's my take on it.

Ken

I have to agree about new guys and props EXCEPT I teach them to balance to get them in the habit early on.. There front bearings will thank them later

If you can get 50 new guys out in tall grass and short nose gears you don't have to mow the field... well its not a PROVEN theory[sm=49_49.gif]

Hey, it wouldn't be normal for me to NOT argue with Ken and Minn, would it. [&:]

One problem with our judgement of model vibration is that we actually can see only the "slow" vibrations. And we often judge the balance of our props by what we see. And about all we'll see is the gross vibration. The difference in slow and fast is really frequency. The bad balance we see is low frequency. And it can obviously do bad things.

Bad thing is that the higher frequencies we don't see on the ground can bite the airplane in the air.
Bad thing is that there is a thing called damping. Why is it bad? Because when our airplane is running on the ground, we're holding it to the ground. Or holding it back. Whichever it is, the model has something that can absorb and damp.
And when the airplane is flying and all that damping has to shift out to other places, resonance and just plain "too little damping" can let the vibration change frequency.

So I've always felt it worth the effort to check prop balance, reject the bad ones, and balance the ok ones. That way, ain't no bad old vibrations gonna sneak by.

Also, one reason a number of people feel strongly that props don't need balancing nowadays can be that they don't see any out of balance when they do check. How many brands of props are there? Do we all use them all? And do some guys only use one brand? Or only use one type, like reinforced nylon? You know anyone who won't use wood because they break too easily?

Recently, I ran into a number of APCs that came to rest at 3-9oclock INSTANTLY. Why? Hole off center toward 6oclock? Lead slug hidden in the hub at 12oclock? Lord, I don't know but those puppies made me pull out my old razor blade balancer and check to see if the newer balancer was messed up. The props were messed up, not my balancers. I took 'em back and went to the other LHS and bought the same sizes and found another APC out the same way. I took that back and avoided buying APCs for awhile. Recently purchased ones haven't done that trick again.

In the last year I've been keeping a rough count of how many of each type and brand show badly on the balancer. Not a hard study, just making a mental count. And I'd guess about half the wood props I've bought get thrown into the pile to be balanced. And maybe one or two out of 10 synthetics get set aside. And I haven't needed to take back a synthetic since that run of APCs. And have seen no real difference in counts by brand.

How off can a prop be to make me work on it? If it is very SLOOOWwww to move, it's ok as is. If it WHACKS around, it goes back into the bag to go back to the LHS. In between gets worked on.

............................. If you're a beginner, it would be to your advantage to buy a good balancer when you can afford it. And your own testing will do you a world of good in making your own decision on this. It will also help you get a handle on the advice you get on the internet.

DaRock, exactly how do I use the balancer? I have the one with the magnets on each tower. Do I slowly rotate the prop and see where it stops. Cripes!!! here I am asking how do you use it then I start offering answers. Sorry--Keep my fingers still.

This discussion is one that we see a lot here at RCU (as well as at other RC forums and at the field as well) and it boils down to this:

There are different kinds of people in the world.

Some people will tell you that if you're going to paint the walls in your house, the proper way to do it is to sand off all of the old paint, then apply a sealer and wait two weeks for it to dry. Then apply a primer coat, and let it dry for two days. Then apply two coats of the paint of your choice - allowing drying time in between.

When you wash your car, do you hand-wash it using a mild detergent and then dry it with a chamois cloth and wax it? Or do you run it through the local car wash?

Do you go out of your way to go to a name-brand gas station and fill your tank with their super-special premium gasoline that cleans your engine and reduces friction, or do you go to the local "Stop 'n' Go" on the corner and fill up with the cheap stuff?

It is painfully obvious that going out of your way to fill your car with better gas will keep your engine running better, smoother and longer, but I don't do it.

Now if I were flying extreme-speed planes, or serious competition Pattern flying, I would balance my props.

But I'm a sport flier, Most of the things I fly are in the 46 2-stroke range up to small gassers with most of them falling in the 91 - 120 4-stroke range. And I don't balance my props.

I'm not saying that balancing props is a bad idea, it's a good idea. But I don't do it.

Neither do I buy the $15-a-bottle shampoo that the girl who cuts my hair says I "really SHOULD use"

Stick the sucker in there any old way. It actually doesn't matter a whole lot. An out of balanced prop is going to start moving no matter how it's "loaded" into that balancer.

Now, that said, to make the prop show its balance quicker, put it in horizontal. That way the heavy blade will have the most leverage to start heading downward, and you'll see it start sooner.

Also, after you start to gain experience, if you've always loaded the prop the same way every time, you'll be judging from the same starting point all the time.

BTW, if you're new at this, try to balance the worst prop first.

A prop that is perfectly balanced will not move from any load orientation. No heavy parts to start the movement.

And don't worry about bringing that out of balanced prop to that "no move" state. It's not worth the effort. It's a great learning experience, but not that important in practice.

Thanks I will give it a try right now. Got lots of props to play with.

One other question. It is better to scrape the heavy blade or add paint to the lite blade?

With most of the reinforced synthetic props nowadays, you're not going to see many (maybe any) badly out of balance. If you do, you need to check your balancing setup. If it checks out and you have found badly balanced synthetics, you need to avoid that manufacturer for awhile. He's got a bad die, or his hole reamer is out of specs or something. And his QA is not to be trusted.

I found a few APCs awhile back that all went INSTANTLY to horizontal. They didn't show when I loaded the first one, because I load horizontal. But the 2nd one instantly fell over. And when I saw it do the horizontal return with VENGANCE, I went back a checked the 1st one. When those were loaded at an angle, they went to horizontal QUICKLY and stayed. That isn't balanced. Why they went perfectly horizontal? They were perfectly out of balance is the simple reason. I'm guessing the hole reamer moves in two axis and the vertical was off. For sure the QA was off.

I've come to the belief that when a prop very lazily moves, I've got the balance within reason. And truthfully, nowadays, most systhetics are going to be that good. The woods I've seen in the last year, probably about half are good to go. Some of the others wind up being returned to the LHS.