RC Prop Balancing Made Easy.
I have been often asked, “Do I need to balance my prop?” and the quick answer is always “Yes!” A properly balanced prop will give you more rpm from gas, glow and electric engines. A balanced prop will reduce the wear and tear on your aircraft by greatly reducing vibration, which leads to reducing premature failure to all the components and thereby giving your aircraft a longer life. You need to do it on every prop, every single one. There are several types of balancers on the market today that will do a great job of getting different size props balanced. No matter which you use, the balancing procedure will be the same for all.
1: HOLE SIZING
The first step is to enlarge the shaft hole to a size that fits your engine. If you balance the prop first, then enlarge the hole, you will have to come back and balance the prop again, so save some time by balancing afterward. The best way to do this is by using a good prop hand reamer because this will keep the hole concentric.
Next you have to have a prop balancer, and the best one out there is the Tru-Spin Prop Balancer from Du-Bro Products. Reasonably priced you need to assemble it properly following the instructions, and then make sure to set it up so the balancing mandrel is level.
2: FINDING THE HEAVY BLADE
The second step is to place the prop on the balancer in the horizontal position to find out which side has the heavy blade.
3: REMOVING MATERIAL
Two methods are commonly used to balance the propeller. The first involves lightening the heavy blade until the propeller balances close to the horizontal position. Use a razor blade or sand paper to remove small amounts of material while rechecking the balance. Don’t forget to wipe off any dust or shavings before re-checking the balance.
4: ADDING MATERIAL
The second requires adding material, generally clear spray paint or thin CA glue with a little kicker to the lighter side of the blade until it balances in the horizontal position. You want to use a fast drying paint and wait until it is dry, because it will be a little lighter when dry. To speed up this drying process I use a blow dryer. Both ways will work well; I generally will remove material from fiberglass/nylon and carbon fiber blades, while using the addition method to the wood blades.
5: PRELIMINARY BALANCE
Once the heavy blade is identified and the prop balanced level or within five to 10 degrees in the horizontal plane you can move to the next step.
6: HUB BALANCING
Place the heavy blade down so the prop is sitting in a vertical position. Check to see which way the prop wants to drop towards horizontal, whichever way it drops, you will need to add some thick CA and kicker to the opposite side so that the prop can balance in the vertical position.
7: FINAL BALANCE
Now move the prop to any position and see if it stays there, if it does then you have a balanced prop. If not keep adjust the amount of CA on the hub by adding or sanding off (in case you over did it) until it does. You may also have to adjust the blade weight to fine-tune the balance.
8: MARKING THE BALANCED PROP
After the prop is balanced, put some type of mark on it so you know it is ready for flight. I use a felt-tip marker to write a “B” on the hub for balance.
For more information on the Du-Bro Propeller Balancer, Click Here
About a million years ago (I’m 86) I was in an Aircraft and Engine program where balancing a full scale prop was covered. An important step was Swinging the prop, where checking the length against a fixed item. Some times one blade might be longer. An article in one of the RC magazines suggested that this step might be as critical as weight balance.
I am familiar with the need to balance but never thought about the hub. Derr…never thought of marking the balanced props though!!
Another thing to consider that will not only help the balancing procedure but will add safety as well is to paint the tips.
Another method to bring a prop into balance is to paint the tips, which also provides a measure of safety.
Great Prop Balancing article.
It would be helpful to discuss removing material from the heavy blade in more detail, so that it maintains the blade pitch and performance and that it matches the opposite blade.
Check the tip path each blade once it is installed on the engine this can be a tremendous benefit to reduce vibration. Adjust tip path for tracking bye carefully scraping the rear center hub that contacts the engines crankshaft Drive plate.
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