AD Diamond gear assembly and fitting.

Here is a quick review of the gear fitting.

Assembling the gear is fairly straightforward.

I will show the steps required to assemble the Behotec e-Tract gear.


Kit content:


3 e-Tract retract units

3 struts ( trailing link type )

3 tyres

One controller/ cables bag ( e-tract controller, display unit, male-male cables )

One direct steering servo mount bag ( optional )

One main wheel rims and e-brakes bag ( including 2 friction plates and 10 socket head screws )

One front wheel rim bag ( including 5 countersink philips head screws and the strut shear pin)

One bag with 2 main struts shear pins and 2 main wheels screw type axles/ nuts.


General considerations:


Use thread lock on all screw assemblies.


Wheels assembly:


Locate the wheel component and unpack.

Place the wheel rims on each side of the tire and align the 5 fasteners holes.



Insert the socket head screws ( main wheels ) and countersink screws ( nose wheel ) in the countersink holes and fasten.

Note that the socket head screws are protruding on purpose to hold the e-brakes friction plate in position.

Fasten the screws in a star pattern to ensure that the rims are being pressed face to face flat.



Assembling the wheels on the struts will require to assemble the e-brake system for the main wheels.

Locate the e-brake components and unpack. Remove the two friction plates from the paper protective bag. Degrease before assembling.



Place the friction plate in position through the 5 protruding socket head holes.



Insert the wheel axle socket head screw through the rim and place the brake assembly hub against the friction plate.

ATTENTION: from this point on, always ensure that the friction plate stays seated against the wheel rim when you move the wheel.


Place the wheel against the strut and fasten, ensuring that the electric cable is exiting rearwards as per the picture below.

When tightening, verify that the wheel can still rotate freely. Clearance vs friction ratio must be setup at this stage. A slight play is normal and helps the friction plate to release after braking action is finished.

Once appropriate clearance is achieved, place the counter nut in position as per the picture below and secure tightly. Do not forget to add thread lock on this nut!


The nose wheel will be place into the nose fork of the front strut. Note that as the rim has a slight recess on one side, two tube sections of different length are supplied to center the wheel. The short tube section goes on the recessed side of the rim as per the picture below.


Once the short section of tube is placed on the wheel, take the axle and insert on the non thread side of the fork, facing upwards. Leave only a short section of the screw extending through the fork side. Insert the long section of the tube into that short section, then place the wheel with the short tube on top through the fork, holding the assembly with one hand from the top ( refer to picture below ). Center the tubes and push the axle all the way though to the threaded side of the fork. Fasten with thread lock fluid. Once again, the ration clearance vs friction will be set while securing the screw.




Insert the set screws on the trunion and on the strut. Insert the shear pins all the way in. Fasten moderately as the toe will be adjusted later on, when set on the plane.

Note that the nose strut is secured by a collar that mounts on top of the trunion. Ensure that the 45 degree routing on the collar is facing outwards as it is designed to clear the wall area. Also ensure that the top of the shear pin does not extend through the collar at all as it might bind against the screw jack otherwise. Even a small amount of protruding pin could jam the nose retract. Ensure that the set screws of this collar are firmly tighten and thread lock is applied.


Servo direct steering:


Locate the steering servo mount accessories bag and open.

Install the servo bracket on the side of the trunion as shown on the picture below. The two socket head screws will require firm fastening to ensure that the bracket does not move when the servo is operating.


Install the brass ball on up most the set screws holes of the strut and insert the strut into the shear pin.

Fasten with thread lock and install the other set screws to secure the strut.



The servo bracket is set for standard JR servo size of 39.8 mm. For Futaba standard servo, you will have to trim the bracket by 0.2 mm. Use an electric file or a tungsten carbide rotary file for this job.

Once the servo is installed, setup the pushrod by installing the two ball links on the threaded rod and trimming it to the appropriate length.


The servo arm ball link should be set at the second hole from the center. Check the arm travel does not push any of the two ball links out of their respective balls. Also make sure that the link stays flat on its ball.


Fitting the gear in the plane.


The gear is supplied with the trunion in the retracted position. Before mounting the gear, you'll need to extend the struts. To do so, plug each retract unit onto the e-controller on the MOT 1-3 position. All the plugs should be facing the same way. MOT 3 is for the nose gear retract. Plug the gear battery ( a Lipo 2S or A123 3S unit is sufficient ) and a servo tester control unit along with a Rx battery. Move the control switch from down, which should give a servo output of -100% to up with a servo output of+ 100%. The gear should now drive into the extended position. If not, invert all the plugs and try again.

Mount your extended gear using the socket head screws supplied.

Install the retract and e-brakes harness so that it never gets pulled when the gear is moving.

Once the gear is mounted, inspect the retraction path and the gear bay opening. You must ensure that the bay opening is wide enough and nothing will obstruct the retraction motion. Check the trunion, struts and wheels. The do a first test one strut at a time: retract one strut and be ready to disconnect the gear battery when it approaches the bay opening. Once this is done, check for clearance and trim if necessary. Then re-plug the gear battery and let the gear retract further till the next low clearance point. Apply the same procedure again till the gear is fully retracted. Pay a special attention about the wing/ fuselage internal ribs/ bulkheads at the end of the travel. We recommend to ensure a minimum of 2,5 mm / 1/10" clearance from the airframe at all times.

Proceed the same for every strut till you are 100% satisfied that the appropriate clearance is ensured all around. Also check the harness clearance and tension during this process.

Then extend the gear again and check for the main wheels toe. Adjust if necessary. To lock the toe angle, we recommend the following:

    1. Cut two slots on the trunion part of the shear pin at the set screw location with a dremel cutting wheel. Fasten the pin in the trunion.

    2. Degrease the shear pin part that goes into the strut. Put one drop of low strength thread lock on this part. Insert into the strut and adjust the toe. Fasten the strut set screws firmly without overstressing the thread. Let the thread lock dry before use.



        Retracts setup:


        The gear setup is fairly easy.


          1. Make sure that the channel you are going to use is set at +- 100%

          2. Plug the gear output and brake output on the controller

          3. Power up the receiver and plug the gear battery

          4. Activate the gear switch both way wait 2 seconds between each switching. If the gear does not move, invert the gear output plugs from the controller unit. If the switch is inverted, change the travel from the transmitter. If the gear stops before it is fully extended/ retracted, have a look at the display. If it shows a lightning symbol, then the gear is binding. Check for hard point/ rubbing/ binding. If the display shows a T, then the gear stopped due to timeout. Increase the timeout delay.

          5. Setup your brakes. Plug the left brake on output 1 and the rigth brake on output 2. The middle cable of the 3 way plug SHOULD NOT BE CONNECTED. Enter the brake setup menu to learn RC and set the no brake position as well as max brake position.

          6.Now check the braking power. Activate the brakes from your transmitter to full position. Move the model on a surface representative of your runway ( concrete or grass ). The braking power should be so that the wheel are about to lock. If they are locking when you push the model hard, decrease each brake setting ( brake 1 is usually for the left main wheel and brake 2 for the right main wheel ) slowly till satisfactory. On concrete, the Diamond will require about 60% braking power on each wheel.