Smart-RC eCCPM Upgrade

My thanks to www.smart-rc.com for the supply of the ccpm conversion kit.

The following is a short review of the build of this kit and some initial thoughts on how this conversion changes the inflight characteristics of the T-Rex. The review and pictures are of the G10 version of the kit, it is also available in carbon fiber.

The review content (pictures and words) are courtesy of my father (Eric Davis) who agreed to perform the conversion on his own T-Rex as I did not have the opportunity to do the review myself due to other test commitments. I will be flying the converted T-Rex shortly to give my own thoughts on the flight characteristics.

To provide some details for the review the converted machine is a standard T-Rex with Align servos, Align 400S motor and E-Tec 1700 pack. For detailed build instructions smart-rc provide ample detail on their own site. However, there is some extra detail and thoughts on the build in the following review.

Initially some build pictures then over to my father for the rest of the review ....

The modification of the Trex to ccpm was something that I was keen to do having flown large scale Vario models with this control system for many years. The modifications to the main frames and fitment of the kit are very simple as can be seen from the following pictures and the producers own web site Smart-rc.com.

I used the Align 9g servos, the loads on these will be reduced by switching to this method as all three servos now control all cyclic commands, this should improve the response. The one proviso to switching to this method of control is that you have a transmitter with swash plate mixing, in particular 120 degrees.

Once I had all servos moving in the correct way I found the pitch range was short but an adjustment to the atv on the transmitter to each servo cured this, it was then left to some minor adjustments of same atv to cure any swashplate interaction when moving from full negative pitch to full positive.

Whilst carrying out these adjustments it was noticed that the elevator servo was moving in the frame more than was desirable, this may not be a problem for those of you that fit this kit but this is how I got over it. The cause for me was the rubber grommets that the screws pass through to hold the servo to the frame. I removed the grommet and ferrel with the intention of screwing the servo to the frame without them (vibration not being so critical) but realized that the screw would spread the lugs apart. To cure this I superglued a piece of thin fiberglass on the underside of the lugs, drilled a hole through to match the frame and fitted the servo with no fear of the lugs spreading.

I did not use the bent end control rods preferring balls and if you look closely at the pictures it can be seen that the links have been made from left overs of my many years of helicopter flying. The Align links are now in place, they were not available at the time of modification.

Now to the part you have been waiting for, yes it fly's really well I have had no need to use exponential or dual rates the response being OK, not twitchy but there when you need it.

To make a comparison of the change to the servo response with the model unmodified put the model on the bench. Switch on the radio and plug in the flight pack, ENGAGE THROTTLE HOLD, now move from low to high pitch fairly quickly. You will see that the pitch change lags behind that of the movement of the transmitter stick, try this with the ccpm setup and you will find this is no longer the case (remember I am not using high speed high torque servos).

There are several other advantages to this modification apart from those already mentioned. There is the reduction in weight (I have not checked but a claimed 30 grams), additionally the number of ball links and control pivots each with its friction and slop have been significantly reduced. Also an increase in area where the servo tray was located has made securing the flight pack easier. A suggestion here, if you secure the flight pack on its edge it is possible for it to move back and come into contact with a hot motor, to alleviate this screw a piece of dowel or round plastic between the frames using the screw holes that had held the servo tray.

In conclusion I am really pleased with the change to the model, the kit is reasonably priced and easy to fit requiring the very basic of tools.

My thanks to my Dad for the review. I've been told that his T-Rex is staying CCPM converted, so I guess that speaks volumes.

Update : 08/05/2005

Flight Report

Well today I finally got to fly the eCCPM converted T-Rex. However it did have a couple more upgrades to it than I expected. Firstly my father had fitted the Align CNC mixer arms, a good upgrade and one of the few I consider to be a necessity. Also he had modified the elevator control such that the servo is connecting directly to the swashplate rather than using the original T-Rex control arm. I'll get some pictures of this to show the modification but the reason for doing this was to get rid of unwanted interaction. All servos connected directly to the swashplate makes for a much easier setup to fine tune. Lastly a set of SAB 305mm carbon blades had been fitted.

Update:: 12/05/2005

Following is the modifications my father made to get a much more linear movement on the elevator servo, plus the addition of an anti-rotation slider due to the removal of the elevator seesaw which acted as anti-rotation in the standard kit.This mod allows for much easier setup of the eCCPM servo movements as all servos are now acting directly with the swashplate where as before the elevator servo was still acting through a control horn. Also note the holes in the side frame opposite the servo to allow screwdriver access to the screws for servo horn and servo mounting. Making this small modification allowed my father to remove all interaction he had on the swashplate due to the elevator control horn introducing a non linear movement relative to the aileron and pitch servos.

Another change my father is now considering is to use the anti-rotation slider from the X400 instead of making one up out of plastic/carbon fibre. This should work just as well and is much less time consuming to make/fit.

The flight test was conducted in fairly windy conditions (10MPH+), so this was going to be a good test of the positivity of the cyclic and collective controls.

The model was placed on the ground, spooled up, switched into idle up and brought swiftly up into a waist high hover. The difference to a standard T-Rex was immediately obvious. The cyclic controls were superbly precise and I was able to hold an extremely stable hover despite the gusting wind. Collective response was similarly precise. Having flown various different incarnations of slop reducing bling and upgrades on my standard T-Rex I was very impressed with the level of control from the eCCPM config. It was easily as good if not better than any configuration I have tried so far, more importantly it's a lot cheaper. Fortunately I only have one more test to complete for a standard configuration T-Rex (the Align CNC swashplate). As soon as this is done I will be converting to eCCPM and not looking back. I will of course continue to run a separate stock T-Rex as it is always good to have a baseline to fly for comparison purposes but my main machine will be eCCPM.

Following the hovering I did some lazy eights and forward flight and the whole machine was very confidence inspiring despite the cross winds buffeting at the machine. Given the conditions it wasn't sensible to try anything further but this was enough for me to draw conclusions.

Conclusion

Given the extremely modest price of this eCCPM upgrade I would consider this ahead of any other performance part. The change in control responsiveness was obvious rather than subtle and the flight characteristics of the T-Rex were suddenly tamed to the point of inspiring confidence even in windy conditions. I expected an improvement in the flight characteristics but I didn't expect it to be as outwardly obvious or quite as good as it turned out to be. The build of this kit is simple and uneventful and the web based instructions are excellent. Based on this I can only thoroughly recommend this upgrade.

Performance

Number of ratings: 6

Rating: 4.33