prop balancing

[Caballo]

It was stored in my barn for many years, wrapped in plastic sheeting. I have recently located the Mod.III in my garage to begin the building process again.

I would have to park my aircraft in a carport style hanger at the very least, due to the intense sunlight here in southern New Mexico, however.

[SkyPirate]

what will matter is the position the prop was stored in ..layed down flat is best ,..wood props if nicked or not sealed well will attract moisture,..if the prop was standing up ..the moisture will change the balance making the lower blade heavier ..if it was standing up ..take a washable marker and mark the end that was lower ..now find a piece of tube that will fit thru the center hole tight ..set up 2 rails for this tube to set on that are perfectly level,...see if the prop stays or rotates on it's own one way or the other ..if it moves then good chances the prop is not balanced,..this method is a quick way to check ,,not as precise as mounting the prop on a balancer,..which most don't have handy,..there are more precise ways ,..it takes time to build it ,..checking this way first will tell you if a more precise way is needed..this way there is no drag on the tube going thru the prop,..it will rotate freely if the 2 planes it is resting on are perfectly level ,.only a heavier blade will rotate it.

Chase

[Slyfox]

I finally got this thing balanced. I got it down to 0 ISP. Can't get any better than that. How did I do it. Well, I went to the parts store and got me some Wheel weights, the flat ones with sticky on the back side. I ended up with a whole ounce of weights. I have a spinner and so I originally put them in the place it called for using 1/4 piece each time on the outside of the spinner. Finally I got it right down with 4 pieces. Than I removed one at a time and drilled an 1/8 inch hole and put a new weight on the back side and than used a stainless pull rivet and set it in place. All I see now is a rivet and the weight is on the inside. Flies nice and smooth now. I started with an ISP of 1.19, this is actually just under the recommended 1.20 and you need to get the prop worked on. So I was really just inside the allowable to dynamic balance this prop.

[TGio]

Steve,
Well done! Did you ream the hole you drilled in the spinner backing plate? Keep a real good eye on it. It will crack if the hole has a stress riser on it.

[Slyfox]

Actually the spinner cap, fiberglass, was the area that I put the weights to. But yes, I cleaned everything up real nice.

[akarmy]

Hey Steve, Can you give a bit more detail on how you attached the weights? Are you going into the back plate of the spinner with your rivets, or into the side flange of the back plate? Do you have to remove the spinner cap to install the weights? Etc? Any pictures?

Me and a buddy just got the Dynavibe and are going to balance the Kitfox and his RV.

[Slyfox]

On the kitfox I put the weights to the spinner. My spinner is the bigger fiberglass 9" spinner. I put them on the rear of the spinner with the weights to the inside. The rivets are stainless CS4-4 I think round head. The weights are the flat sticky on the back side, with a strip that is in 1/4 pieces. I got mine from Motion auto parts for about 30 dollars. I found that if you take the weight and smack it with a hammer and flatten it out the rivet works real nice and only one revit. On the RV I left the spinner on and balanced and put the weight right on the outer back side of the back plate for the spinner. After all was balanced I drilled a hole in the weight to the back plate with an angle drill and put a poppy in to hold it. worked great and got both down to near 0 on the ISP. And it was quick. Make sure and take the time to put the degrees on the flywheel (every 10 degrees) for the rv and the hub on the kitfox. Also make sure the degrees looking at the prob from the front goes in the direction of the prop, which would be counterclockwise.

Oh and the bracket I made works on both engines. The rv I work off the front bolt for the case half on top. The kitfox 912 I work off the top bolt hole on the left side of the gear case. I also leave the tape on the prop, the RV I can see when flying the kitfox I don't see. I'll be checking the balance every 100hrs and to do it is real quick, so no problem.

[Dorsal]

Steve, if you think of it please post again after the 100 hours, curious if you see much change.

[akarmy]

Ok on the Rv we got it to 0.01 ips using bolts and washers in the ring gear. Worked great. On the kitfox I can't seem to get it below 0.15 no matter what I try. I have the same mounting locations as you. I have been sticking the weight on the inside of the backplate flange so the centrifical force slings them against the fiberglass.

My initial no weight ips is 0.25

about how much weight are you ending up using? Also, are you able to balance with one weight location, or multiple?

For reference, I'm running an ivo medium 3 blade.

[akarmy]

Thanks Steve for the idea to pre-index the prop hub. That really makes it clear what you are doing and saves a ton of time.



After stepping back and starting over fresh on another day, I was able to quite quickly get it down from a starting point of 0.35 to 0.01 as a finished balance.

more pictures are on my site if you want to see the process.

http://flying.karmy.com/?p=344