Ok,

I had to install a new prop on my Alpha Trainer.

My question is should I balance the prop or just leave it the way I bought it?


If I should balance the prop, how do I go about doing this?


Also, the engine mounting bolts have worked themselves loose a little bit. I don't want to take out the whole engine, is there some kind of tool that I can make/buy that would turn in those bolts with out taking out the whole engine?


One last thing, I know that this has been asked alot, but can someone please tell me how to set the low/high idle needle settings to get the engine to run? I can't even get the engiine to cought!



king K

As far as balancing the prop goes, don't worry about it.
I have never balanced one yet and believe me I've been through alot of em. Just twist her on and go for it.
I think that the prop manufacturers have got them about as close as 99% will ever need.

As for question 2. Which bolts?
Firewall or engine flange???
If it's firewall just take off the muffler (to access that side) take one out at a time/ clean it off apply a little locktite and screw it back in.
Another trick that I've done is to lightly damage the threads. Take the bolt out and squeeze the threads with a pair of pliers to LIGHTLY damage the threads. (stay about a 1/16" to 1/8" back from point so it starts good) screw it back in and your done. (you'll feel the added torque putting it back in)(that's what ya want)

If it's the engine to mount bolts go with longer bolts and NYLOCK nuts.

Question 3.. Alpha engine
Aren't those preset from factory/ already broken in.
(I need more info)

Never ballanced a prop? and no problems from it? You got very lucky.

APC Grey props rearely need any ballance adjustment. Every other brand and type prop I have tried... almost always is out of ballance.

A slightly imballanced prop puts an added vibration load on the aircraft if nothing else. That can lead to glue joint fialures. More imballanced and you get fuel foaming problems, which can lead to unexplained dead-sticks anywhere from 7/8 full tank to 1/3 tank. If the imballance is severe enough it will just rip the engine off the firewall.

One method for ballancing is to paint the light tip. First paint both tips some bright color to help make the prop arc visible. When that drys, balance check and add another coat to the front of the heavy blade (just at the tip, not the whole blade)

Another is to lightly sand the front of the heavy blade. Avoid sanding the back (flat) side as that has a larger chance of changing the pitch in the area sanded.

You can lightly sand the leading edge to remove mold flashing. Its a bad idea to sand the trailing edge, especially with APC grey props. (yes those are the ones that are the sharpest at the TE...) The trailing edge of the APC is sharp for a purpose. It helps reduce the load of the prop on the engine and helps reduce prop noise.

DEFINATELY balance your props.(typo somewhere there!)

One member of my club had a bit of prop penetrate his jeans and skin. Bad look.

I spent a bit on a prop balancer and am really pleased. it was a dubro one that can balance impellers, spinners, chopper blades etc as well.

Remember Fly safe!!

I Agree defenitly balance the props, i never did until someone suggested i did, and belive me every prop i had was quite a bit out of balance, just buy a simple prop balancer its amazing what you can do with the right tools

HMMM...
Seems I'm sorta out voted here..
Ya better go with the masses on the balance issue.
Evidently I'm not doing something I should. Guess I'll look into this.

Count me as one of those who DOESN'T balance props. I have a balancer, only because it was a gift. I got it over 10 years ago and I have used it twice (The last time was just a year or two ago because I can only smoke in my workshop, and one winter I had nothing to build, so every time I went down for a smoke, I played with the prop a little more till it was PERFECT.... Broke it on the first takeoff with it! LOL)

In any case, One of the trade magazines did an article on it recently and their conclusion was that in MOST cases on glow engines it really wasn't necessary. Think about it, the reason to balance a prop it to reduce vibration. The piston going up and down at 11,000 RPM is creating WAY MORE vibration than a prop ever will.

So this is one of those "Some people swear that you HAVE to do it, and others swear you DON'T. You decide.

PS If you are using anything other than a wooden prop, make sure to scrape the edges with a knife or razor blade to remove the sharp edges!.

I agree with Mike and aim on this one. What I will say, though I've never done it, is the best way to resolve an imbalanced prop would be to put the heavy blade opposite the piston when it's top dead center, that way the imbalanced prop offsets some of the piston weight. That will give you less vibration than a balanced prop.
Dennis-

I have a balancer as well, and although I balance all my props, I wouldn't stop flying because one isn't balanced. Some props are better balanced than others. MAS seems like always needing tweeking. But in all reality on small engines, unless the prop is really bad, it's not needed. On the bigger props I think an unbalanced prop could add undo vibration to the firewall, fuel tank and airframe. All boat, and airplanes props are balanced.

I really think the counter weight on the crank shaft takes care of the piston,as long as the MFG has done a reasonable job of balancing the rotating assembly, one should never have to mess that headache.

My opinion on prob balancing thats it not AS necessary as it once was, prop MFG also benefited for the computer controlled CNC machine process and if you really wanted a perfectly balanced prop you would have to do it under a glass box as you breath, AC/Furnace and natural convection currents in a room would influence your results.

If you use wood props you will need to balance as wood densities will affect balance. The compsite props are a lot more consistant out of the package. APC's are particularly good. Although once in a while you'll find one way out of wack.
It's important to at least check the balance. If you have a prop that is way out of balance at 10,000 rpm the vibration from it is transfered to the airframe and radio. And that's not good. The smoother everthing runs the longer it will last.
[&:]

I would not balance propellers under 20 inches.

Okay... After doin some searching and reading I've come to the conclusion That (I) will not worry about balancing props.
So my definate recomendation is to definately balance your prop if ya think ya MIGHT want to because it definately MIGHT be important.

YOU might definately be correct!

I just MIGHT agree with that