Homemade Prop Balancer

Hey there Robert. Didn't see you enter the room. WELCOME!
Big Homer Simpson "Doh" on this end. If I had known of your
balancer, I could have saved $$$ spent on balancers.
Regardless, thanks, and belated welcome to the forum.
  Bob

Nice. I have a commercial prop balancer, but it’s really meant for large props. It doesn’t work really well with 3-6” props. Looks like you may have the answer.

Ron

Great set up. Another possibility is to rest your music wire on 2 horizontal razor blades. That way, there is no need for making points that have to be well centered.

Hi Robert/rdw777. I like your prop-balancer. Did you "spin" the MW in a drill-chuck while forming the points with the Dremel-wheel?" I've made tapered-plungers (crude meterering-needles) in this way. Yours looks good!

Many years ago I copied (expanded-on..    ) a magnetic-balancer design from a major aero-hobby Co. that debuted back in the 90's? The principle uses magnetic-levitation to reduce friction in the balance-shaft. A pair of magnets are placed in a field where the metal (Ferrous) balance-shaft fits in-between. One shaft-point comes in contact with one magnet and the other end of the shaft levitates in an adjustable air-gap.

I bought a "Kavan" prop-balancer consisting of a 3mm (.118") diameter X 7cm long metal shaft with points ground on both ends and two tapered cones which are too big for most 1/2A prop hub-holes. Its 3mm shaft is .007" undersize.. for the .125" diameter hub-hole which the Cox .049/.051 engines use.. but it's a nice balancer for propellers having larger hub-holes.

I decided to build a simple wood frame for it..  with two upright "sticks" for lack of a better description.. and sourced a pair of tiny Samarium Cobalt/Rare-Earth magnets which I glued on the ends of a pair of 5/16" X 1-1/4" length hex-bolts which I tapped threads in the uprights for. When assembled with the base and top plywood panels, this design will accommodate a maximum balance shaft length of 3.5" a minimum length of 2" and a maximum propeller diameter of 16".

Some photos with the Kavan balance-shaft.. (I have some .125'" diameter MW and want to make another balance-shaft expressly for 1/8" diameter hub-holes.)



... note the mag-lev/air-gap..



I would say that it's a pretty sensitive/accurate method.. not to mention "fun and easy to make".

Thank you all for the warm reception, I like this group

Roddie, Your balancer is awesome! That’s minimal friction as you can get! I like the calibration method with screws.... My version can be a bit fiddly with getting the aluminum tabs tweaked just right..... Taking an idea from yours, Maybe a calibration screw on one side would help.....

I just spun the MW in my fingers but checked center (and flatness ) by rolling on a piece of glass using a strong light.... Fortunately the 1/16 id tube fits the bore of the .020 prop well.... A short length of tube that fits the primary tube od fits the counter bore on the drive plate side.... The cones on yours make a lot of sense though..... When adjusted properly a gentle tap will send the prop on a dozen or so revs.... A little mark on the base lets me watch tracking....Still need to fab tubes for .049 props...

bty.... I’ve really enjoyed your scratch builds in Modeling.... Inspiring me for a 1/2 A CL one of these days.... Enjoying rehabbing engines for now,

Thank you again,

Robert

Be sure to use small magnets and place the point of balancer on exactly the center of magnet. With large diameter magnets it will be inaccurate because of magnetic flux.