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BALANCING / TRACKING

 

 

 

 

 

1 - BALANCING

 

The E-PROPS propellers are precisely balanced at workshop. The team is using an electronic bench to balance the propellers, with two oscilloscopes, and all the data are registreted in the computer system of the company.

 

Be careful : the blades have not necessarily the same weight.

If you have received 2 blades with different weights, it doesn't matter.

To balance a propeller, the weight of both blades is important, of course, but what is critical is the weight distribution all along the blade, called STATIC MOMENT.

 

eprops equilibrage balancing

 

 

 

The weights P1 et P2 of each blade apply respectively to centre of gravity G1 and G2, which are not at an equal distance on the center of rotation O of the propeller.

The balancing must be realized to obtain : P1 x d1 = P2 x d2

 

The E-PROPS maximum static moment tolerance is 0,4 gr/m

 

 

Example : report of weight and static moment measures (coming from E-PROPS software) :

 

equilibrage balacing eprops

 

This propeller is a 2-blade for Polini Thor 250, or 250, diamètre 150 cm.

- blade 1 weights 348,58 gr and has a static moment of 83,43 gr/m

- blade 2 weights 350,43 gr and has a static moment of 83,53 gr/m

By E-PROPS, the static moment tolerance is 0,4 gr/m

=> here : the weights of the blades are different (gap 1,85 gr), and the gap between the 2 static moments is 0,1 gr/m. In the tolerance.

This propeller is perfectly balanced.

 

Each E-PROPS blade is identified with a serial number (example above 43806, 48875). This number is written on the blade, and also in the RFID chip which is in every blade (readable with a RFID reader).

Each blade is balanced with an other blade (or other blades, if the propeller has more than 2 blades). The obtained propeller is well-balanced. If you assemble non-paired blades, they would not be balanced together.

 

Please verify that the E-PROPS blades serial numbers are provided to go together

 

 

This data is on your invoice, or delivery note, and if you do not have those documents, we can give this information to you. Please contact us by email: helices@e-props.fr

In case of doubts, il is possible to returm the propeller to E-Props for balancing verification.

 

Never fly with an E-PROPS propeller if the blades are not paired

 

 

If you want to verify the balancing of your propeller, make sure the assembly is correct : blades on the right side, align the holes. It is possible that the propeller lean a litlle : it is due to the 0,4 gr/m tolerance. This tolerance has been calculated then deeply tested.

=> Please note : those tests have been made on many motors; there are no vibrations up to 0,6 gr/m.

 

It is strongly FORBIDDEN to add weight to one blade, in order to have the same weight for all blades. The propeller would be then unbalanced, and can cause some vibrations

 

The E-PROPS propellers are very light and very well balanced, and they generate very few vibrations.

 

 

 

 

2 - TRACKING

 

Propeller track is the path followed by a blade segment in one rotation.

There is often a traking gap on the wooden propellers, made and/or finished by hand.

On large scale composite productions, when blades are made in the same molds (non adjustable), this phenomenon doesn't exist.

 

tracking helice

 

 

The blades of the same E-PROPS models are coming out of the same molds. They have exactly the same geometry. Then the finish is made with CNC machines (see page MANUFACTURING). The E-PROPS propellers coming from the same mold do not have tracking.

 

And on E-PROPS propellers, the maximum tracking can be about 20-25 mm, even more.

 

The tracking measured at propeller can also come from other places : reducer plate not parallel, dissymmetrical engine fasteners, tightening without torque wrench...

 

Do not put a rubber washer between the propeller and the reducer flange to reduce the tracking. It is dangereous because the loads are transferred to the propellers screws and those screws can suddenly break.

 

If you have no vibrations, tracking is absolutely not important.

 

 

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