dragon_not_fly Heliman Location: US
| Calling all T.R.E.C users!I know I can't be the only one that flies this stupid little helicopter with a T.R.E.C(Tail Rotor Electronic Controller) tail motor ESC/mix system???? Well any way, the reason I went to separates in the first place was to try and eliminate the tail motor burn out problem. This was out of hand and was starting to get really annoying, besides my stock Walkera all-in-one, 4-in-1 controller fried and I had nothing to fly the helicopter with. If you are not familiar with TREC, I suggest you check it out here: http://www.dionysusdesign.com. The people at Dionysus Design are really great, they make a good product and are willing to support it, something I can not say for Walkera, may be they will change in the future. Now, the reason for TREC was simply this, its potential at running at a blazing 78.125 KHz output frequency, the typical output frequency for a brushed ESC is about 2.88 KHz which is way too low on small metal contacts inside the tail motors that run these helicopters. If you are going to fly this helicopter with stock main rotor blades, stock tail motor/rotor, you will be going through tail motors. TREC's high operating frequency and adjustable throttle curve/mix gain coupled with the Colco Thunderbird tail motor have made all the difference. At the time of this writing, I have documented a full 40 flights of TREC and a Colco Thunderbird tail motor where the Colco tail motor was brand new when first setup with TREC. The Colco tail motor is still going strong, I have never been able to duplicate this with the stock Walkera setup.
[For TREC users only]
NOTE: The reason I posted my helicopter's setup in the last post was to make known the physical setup of it; i.e., the stock high lift, high drag, high torque main rotor blades, basically stock tail motor and rotor etc... all of these and more play a significant part in determining the setup of TREC; mix gain(s), throttle curve, Start/End points etc...
[TREC setup]
*Throttle curve points, 17 of them from left to right; 0,0,0,107,131,152,169,184,197,208,217,225,232,239,245,250,255. You will notice that this is the default throttle curve for firmware versions 5 and up except for the third point, in the default throttle curve this is 65, I changed this to 0 to prevent the tail rotor from spinning before the main rotor starts spinning where the main rotor is under the control of: a GWS ICS-300 main motor ESC, a GWS Naro 4 Channel receiver and a GWS GWT-4A II 4 channel FM transmitter.
*TREC tail motor operating frequency: 78.125 KHz. I set this as high as possible to provide the smoothest voltages to those tiny little tail motor brushes so as to reduce the damaging effects of voltage spikes
*Start/End points: 1.100/1.900 ms Works just fine with my GWS radio gear believe it or not
*Input averaging: NONE. Do not enable this on a fixed pitch tail rotor setup since we need TREC to respond as fast as possible to main motor signal changes(throttle changes) since a fixed pitch is usually slower in responding to
main motor changes than a variable pitch one. Input averaging will reduce hunting if it exists though in theory.
*Falling Voltage compensation: Not enabled. This is a tricky one, according to TREC's help file this would be used on 75% throttle curves usually when a "high voltage" LiPO flight pack is used and the curve is too low when flight pack voltage runs down to maintain the correct revo-mix. The falling voltage compensation raises the throttle curve in increments over a period of time to compensate. I had this working somewhat on a 72% throttle curve that I was originally working with. The falling voltage compensation was just too much and would drift the nose to the RIGHT if facing the rear of the helicopter as the flight progressed.
*Mix gains: 1 cell LiPO count=104, 2 cell LiPO count=104 and 3 cell LiPO count=85, I ignored the 4 cell LiPO count.
*Version 6.1 firmware! In my personal experiences with TREC, I would avoid version 5 firmware, I do not believe that it is available for download anymore. Version 5 firmware would turn the tail motor off in flight for a few seconds or while on the ground and the heli would spin out of control. I tried version 3 firmware and it on occassion would "flip out" on me doing brief erradicate things. The other thing to note about version 3 firmware that I noticed on my setup was that the tail motor would hunt holding all other things constant which I initially thought was the GWS PG-03 gyro since it would react negatively to the hunting. Version 6.1 firmware is almost flawless, the tail motor does not hunt almost at all, it runs very smoothly and there is no detectable erradic behavior in the system.
*Motor shutdown: Not enabled This should be obvious, you do not want the tail motor shutting down before the main rotor does
*Cutoff voltage: Cut off voltage is enabled at 5.22 volts The 5.22 volts seems to be a "sweet spot" in the setup where the main rotor will shut down before the tail rotor does when the battery pack dies and then the tail motor soon afterwards.
*Safe Start: Enabled I have this enabled since I do not want the tail motor and the rest of the system from starting when I first plug in the flight pack battery. Holding the rudder transmitter stick full left for over 1 second will disable Safe Start effectively "arming" the system.
*Auto adjust on the number of LiPO cells for voltage monitoring: Not enabled I am currently not flying with LiPO battery packs since I do not want to burn my house down yet...
*LED light: Enabled Nice visual queues feature if you are not flying with a LiPO alarm/speaker
TREC NOTES: It seems that I have to fly the Default Throttle curve on my stock heli, the 72% high throttle curve would work at up to a thigh high hover; that is, it would keep the nose straight, applying more main motor throttle would turn the nose left as the heli rose to head high, not even FULL right rudder would compensate and as such the revo-mix was too low. As a side note, this "low" throttle curve really ran the Colco tail motor cool, it was basically room temperature after flight not even being heat sinked. With the stock, plastic, Walkera, high-drag, high-lift rotor blades and the "weak" geared Colco Thunderbird tail motor, the 72% throttle curve just could not combat the ridiculous amount of torque generated by the stock main blades coupled with the relatively week tail motor/gear combination. Another interesting thing that I noticed with the stock, 7 cell, 8.4 volt, 700 MAh, NiMH flight battery packs is that TREC will see the voltage as 10.12 volts with a fully charged pack! Hmmmm...so much for 8.4 volts. What this does is somewhat tricky in the implementation. When TREC is first fired up on one of these fully charged stock packs, TREC will see the LiPO cell count as 3, NOT 2, this means that the mix gains have to be properly set for a 3 cell count as well as a 2 cell count. When TREC disables the Safe Start, the red LED light will flash 3 times indicating a 3 cell LiPO count, TREC automatically determines this. After I takeoff and maintain a waist high hover for about 45 seconds, the LiPO cell count will be deduced by TREC as 2 from the initial value of 3. So, there is a "transition" in flight.
*PG-03 gyro setup: Red/Green lights both on if the helicopter is completely stationary with FULL gain set. The Walkera's stock blades generate so much torque with sudden throttle changes that I decided to go from my initial setup value of the 12 O'clock position to the 2 O'clock or maximum gain setting. This really helps big time in keeping the nose straight even with sudden throttle changes, where before, the nose would swing left at up to a 45 degree angle where I would need to correct for this. The noticeable downside though is reduced yaw rates for 360's.
*Rudder trim tab on transmitter: DEAD center With all of the above settings on my helicopter and accounting for the physical setup of it, this will keep the nose straight almost all of the way down until the heli is stuck deep within GE.
*Placed the GWS ICS-300 main motor ESC inside the Walkera box that housed the old 4-in-1 controller
*Placed the GWS PG-03 gyro on the left side of the Walkera 4-in-1 box
*Placed TREC on the right side of the Walkera 4-in-1 box
*Placed the GWS receiver on the right side of the heli right behind one of the
cyclic control servos
Left/right are viewed as from the tail of the helicopter
[Thoughts]
If you guys fly with a TREC, let me know what you use in settings since TREC was the most difficult part of the system to get working. It is a very powerful device with many advanced features and is really not for a complete beginner unless you can get some help with it. I am sure that there could be more fine tuning to TREC with my current flying setup... |