New Behotec e-Tract gear line.

Behotec is now offering a new line of electric retacts called e-Tract.

This line is based on the world renowned pneumatic gears and is updated with a few interesting upgrades as you will see later.

The full range of Behotec gear is now available as the e-Tract version, and I have ordered the Scorpion Mk2 version to compare it with the same pneumatic set.

In the following lines I will show you the new electric set side by side with the pneumatic one.

First of all the modifications:

1. Obviously, the pneumatic actuator has been swapped with an electric motor, driving a screw jack.

Here is the pneumatic version:


 and here the electric version:



2. The trunion shape has been slightly altered to cater for the bigger diameter of the screw compared to the pneumatic pushrod.

3. The screw goes all the way to the retract wall and is therefore very rigid, enabling a very precise position of the trunion. This is important due to the next feature.

4. The motors used are stepped motors. This means that the control unit has got a position feedback of the trunion, enabling a very precise positioning in the stops. The fact that the screw is rigidly fixed on both sides helps in achieving a very high precision in the steps resolution. A typical travel on the C36 model is 7600 steps.

5. On the Scorpion set, the struts are square instead of round. This gives a little bit more drag on the gear, which is welcome on this model, as well as a better lateral rigidity.


The gear overall looks very nice and high tech:

The pneumatic version:



vs the electric version:



The weight difference on this gear is 100 grs/ 3.5 oz

The complete e-Tract gear without battery is 1125 grs/ 40 oz whereas the the pneumatic version with the valves is 1025 grs/ 36.5 oz.


6. The gear Control Unit is very advanced. 



It features the following inputs:

Battery ( 2S, 3S Lipo and 2S, 3S A123 accepted )

RC rudder, RC brake, RC gear

and the following output:

Rudder servo

brake 1, brake 2, mot 1, mot 2, mot 3.


The controller menu is also very advanced and can be accessed through the optional ProJet GCU ( the same used for Behotec and BF-Turbines ).

It features the following screens on the main menu::

Reason for stop on the 3 gears.

On the picture below, gear 1 and 3 have stopped into their final step position, gear 2 due to timeout.


The status of the control signal:



The actual current consumption and battery voltage:



The step count for each motor ( ie position of the trunion ):



The gear, brake and rudder signal position in %:



The setup menu ( called master mode ) gives you the possibility to change the following:


Start delay

Max motoring time

Max current before tripoff

Travel steps for the trunion


Brake stops and anti lock setup.

Finally every gear is setup and tested at the factory before shipping.

You just need to plug it in and verify that no friction will occur on the airframe during travel.


Here is a video of the gear system setup in my Scorpion Mk2:

New Behotec e-Tract gear. from Oli Ni on Vimeo.


The retract travel is programmed with a start step and end step.
The resolution Behotec is working at on the C36 is 35mm/7600= 0,0046 mm per step or 4,6 thousands of a mm. Thanks to the very accurate trunion machining, the position can be acquired very precisely. This is working extremely well and the positioning of the trunion assembly is very consistent and extremely stable.
The electronics has a current tripoff and timeout function as an additional safety feature. The main stop function is the step position.
In practice the gear always stops at the stop step ( positioning stop ) and not from current tripoff with the trunion right into the end of the groove. The menu on the GSU allows to see that.


All together, this upgrade is offered at a price increase of 40%. I think that it is quite fair considering the setup ease, everyday dependability, the quality of the electronics and control system and the software ergonomics.