While Top Flights' prop balancer, the "Precision Magnetic Balancer", is as easy to use as it is fun, I think it's as important to have as it is ailerons, elevators and a rudder.

Store bought propellers are not "balanced" and should be - prior to use. If not, you may cause permanant damage to your brand new engine, not to mention it's inefficientcy.

The task of balancing your propeller is as important as it is having one. The instuctions that come with the Top Flight balancer are good, but they're not complete. Their instructions do however get you close, but upon further investigation into the matter, I found that "close" is not "close enough".

Top Flights' instruction manual gets you about 50% there. If you have stopped at that point, you'll see that your propeller is balanced from left to right, but there's more!

In chapter 13, "Prop Talk", in a book published by Model Airplane News, "Getting Started In Radio Controlled Airplanes", Jim Newman further illustrates and explains the need(s) for a complete propeller balancing.

The Precision Magnetic Balancer™ balances the propeller, but Jim's section in the book says that that's only 50%. And to me, 50% is not enough!

The propeller should be divided in fourths, or A/B and C/D. The left side is A/C while the right side is B/D. Top Flight only covers the left and right, while Model Airplane News covers that, and top and bottom, and that's my point!

If you're new like I am to RC flying and want your first flights to be a success, then I would have to recommend you buy a prop balancer - any prop balancer - but I do like Top Flights!

I've been building my plane now for a week and short of connecting the servos to the pushrods and breaking in the engine - it's never seen the sky, but when it finally does, I'm sure that it'll be glorious!

Thanks.

Jon Lamont "MacAir"

And welcome to the world of R/C. This is a hobby that can stay with you many many years if you so desire. It can keep you challenged and is good therapy. In this case, you need to decide whether you are taking the purist point of view, or the realistic point of view. I've been at this since the early 70's and here is what I've resolved myself to on the prop issue. Let's keep this to props other that giant let's say. Anything under 26" I also remember reading the article you mention. It just seems impossible to get every prop exact, every time. This is where the realitly part comes in. I balance every prop the best I can. They are not all perfect, but they've all worked just fine. Although some personalities in this hobby need it to be an exact science, it doesn not have to be in every instance. Don't get me wrong, I'm not saying not to bo the best that you can, just to realize that there are limitations and to recognize what they are. Balance your props on the balancer in the best way you can and go fly them. Have fun and try to find that balance that keeps this enjoyable_bob

I'm in the 50% group and still flying some very well used engines.
Have a goodun,John.

I have to agree with both of you. there gets to be a point where it becomes over kill. balance them on the Top Flight balancer and go flying. I have a trainer with an OS 40 LA motor on it that has well over 200 flights on it. still purrs like a kitten and running fine, and I only went 50% on balancing it.

Don't get too wrapped around the axle worrying about the small stuff is what I say. Heck, if you're gonna worry that much, on touch of a prop on the runway is gonna put in the pits for hours re-balancing your prop.

just my 2 cents worth

Thanks guys for the "experienced perspective". I'll try to keep it real, I just wanna' have fun too, but want to keep the engine around for as long as I can.

I've learned alot in the last few weeks and tend to focus on the smallest details.

But I think it's all really interesting! And fun too! Maybe after my first hard landing - messing up my detailed prop - I won't be so concerned.

MacAir

Morning MacAir,few of my engines date back to the late 70's early 80's,thats balancing with the 50% method,proper break in,and proper cleaning and afterrun,with afterrun fluid arter each flying day will keep the engine running for the great grand kids.
Have a goodun,John.

A lot of my engines date back to the 70's and 80's also. I got my first prop balancer in the mid 90's and I think I've balanced maybe 3 or 4 props so far, mostly out of boredom, but there was at least once when I cut 1/4" off of each blade to shorten a prop at the field with a razor saw. I balanced the prop that evening after a days flying, and the next time I used it, you really couldn't tell a difference.

If you really want to keep your engines in good shape, avoid using them for landing gear.

*Amusing side note: At one point last Winter I had nothing to build and my shop is the only place in the house where I can smoke (wife's rules). So every time I would go for a smoke, I had this prop that I was balancing. I used to have to balance high-speed grinding wheels, so I am familiar with the Dynamic balancing technique. So just to pass the time, I balanced this prop until it was PERFECT (or at least a perfect as humanly possible) First flight last Spring, you guessed it, Hit a pothole and broke the prop on takeoff!

MinnFlyer,
But of course!!!!! Don't you know Murphy lives for our hobby!!!

but you gotta love it anyway

MinnFlyer,

That's a great story and sounds like the thoughts I've been having. Thanks for the reality check!

AMA# (coming soon)

Hi there,

For all you AMA memebers there is actually an article at the AMA website that says prop balancing is completely REDUNDANT.

The link is here AMA article for propreller balancing

So it looks like it is wasted money...make up your own mind but thinking about it I beleive it is better to put the heavier side of the prop oppositre TDC.

Iain

I have read similar articles over the years, and my procedure is as such:
1). Remove the sharp leading and trailing edges of the prop using fine sandpaper (saftey first).
2). Balance prop with a "fingertip" field balancer and a little sandpaper.
3). Mount the prop on the engine so that the blades are approximately horizontal at the start of compression. In the event of a dead engine, the prop will rotate to this position, and be least likely to strike the ground.
4). Go fly! - That's what we're here for... right?

The act of placing the heavy blade opposite the piston is somewhat redundant. If you take your engines apart, you will see that the piston already has a counterbalance on the crankshaft. If the counterbalance is to light, the heavy prop blade could help, but if the counterbalance is to heavy, the heavy prop just makes it worse.

"Don't sweat the petty things, and don't pet the sweaty things"
{author unknown to me}

Well guys, I just can't resist throwing my $.02 out there. I got in a discussion on the forums a while back that wore out my fingers replying back and forth. After all is said and done..... I will still balance my props. I use a Top Flight and do the best I can with left and right balance. The one guy that disagreed with balancing, (for anything smaller than 18inch props if I remember correctly), was VERY knowledgeable. He spoke in terms that I didn't understand, and I figured he probably had an engineering degree or ??. Technically I am SURE he was correct. BUT... me being an old bull-headed Dutchman, can't get the visions of an out of balance front wheel on cars I have seen while driving next to them. Even if it is redundant, and/or not necessary, I, myself, FEEL BETTER balancing my props...
MacAir..... This is a very cool hobby. You do what your common sense and time allows you to do.
I actually enjoy the balancing process...lownslo

Bob

I flew for 3 years before I even owned a balancer. In theory, if the engine manufacturer does their job propperly, the engine SHOULD be perfectly balanced (static & dynamic) without a prop on it. Therefore, I'll keep balancing my props.

In theory, the smaller the prop, the closer any imbalance will be to the center of rotation. The closer to center the weight is, the less impact it will have on the balance.

I feel better knowing I have taken REASONABLE measures to reduce vibration.

Prop Balancer of prop's less than 18" is not a balancer but a money machine for the company selling them.

I have a new Saito 150 that has not even been fired yet. It is going on my winter project. I bought a 16-6 prop as a starting point. It was "out of balance" more than the perverbial ****- hair!!!.. Just because this prop is under the "magical 18 inch.. it's OK rule", I, along with MANY others, would at least rough in this 16 inch prop. I just don't think the reasoning for not balancing, out weighs the reason we should. ....lownslo...

Bob

Something else to consider about an unbalanced prop is this: it is not going to cause constant vibration. It will only cause vibrations at a few certain RPM.

Have you ever had a car with a wheel that was out of balance? I have, several times. It always seemed that thw car would shake a little at a certain speed. Like it would start happening at 55 MPH and then stop at about 60.

So even if a prop were so badly out of balance that it DID cause vibrations, the chances that it would vibrate in a speed range that you are using is slim.

I beg to differ MinnFlyer - If the wheel / prop is out of balance, it is causing continuous vibrations while spinning. However, at certain speeds it will cause a harmonic vibration, increasing the effect tenfold (or more).

My sister blew a head gasket twice in one week because the transmision had a "faint shimmey" around 55 Mph. When she overpowered it and drove 65 Mph, the shimmey "went away". The extra load and vibration this was putting on the engine caused the gasket to degrade so fast, that it only took 4 days between head gasket repairs and the next failure.

A slight imballance is unlikely to cause significant problems, but a gross imballance will reduce the life of the engine or it's internal components (bearings). Most new props are pretty close to ballanced, but I have had a few which were grossly imballanced.

How much of a "faint shimmey" do you think that piston is creating by moving up and down at 11,000 times per minute?

MinnFlyer said: We can't do anything about that piston going up and down at 9K to 11K rpm's. We CAN eliminate that small window of un-balance that MinnFlyer refers to. (although I don't agree with that small window of unbalance) If it is out of balance on the balancer.....it is out of balance at any rpm on that engine.
This is my quote from earlier in this thread.
This subject is just like the "which is the best fuel?", or "how much oil content?"..... Everyone seems to be dug in on their views and will never be convinced otherwise. The bottom line is....we have do what WE feel is best and that we have made an educated decision.
MAN...... I wish it would warm up!!! I am ready for spring!!!!.....lownslo