Written by Ashley Davis Friday, 27 May 2005 00:00
The following is a review of the Heliup Carbon Fiber Frame.
Initially let's take a look at the parts ...
As this is quite a complex build it is very worthwhile taking a look at the very comprehensive build instructions provided by Heliup ---> build instructions.
These are some of the best build instructions I've seen for any upgrade part and Heliup deserves some recognition for making the effort to produce such quality documentation.
Running through the various parts the packaging is very neatly done. All screws are in a separate little pot which I found very useful during the build to stop screws rolling all over the place. The carbon fiber parts are very nicely cut and there are no rough edges or inaccuracies in the holes or cut outs. Similarly the CNC parts are very nicely presented in the usual Heliup blue. All holes were tapped correctly with threads and again no rough edges, bent bits or anything other than nice quality CNC machined parts. The CNC parts are made of 7075 Aluminium, so very tough and rigid.
When I built the frame I didn't have the instructions, but even so it was not overly difficult to work out how the frame goes together. The pictures showing the build do follow a slightly different pattern to the way it is shown in the instructions due to not having them to follow. Also I had to change some of the pictures once I got the instructions as a couple of items I had assembled slightly differently and had to change at a later point, notably the mount point of the anti-rotation slider. I usually take a 'from the ground up' type approach to building so the first step was building the under tray for the frames. The photos below show the fitting of the CNC cross members to the under tray, the side frames bolt through onto these cross members. Following this I'm mounting all of the CNC parts onto one side frame ready for it to be matched to the other side frame and bolted to the under tray. All of this is extremely straight forward and the instructions really only need reference when mounting the CNC parts that hold the main shaft and servos.
The next item to be mounted to the side frames was the holders for the tail pulley and gear. The T-Rex standard tail pulley has to be inserted into the holders and then held in place with a couple of screws and washers. Again a simple piece of assembly but take care to follow the instructions exactly. The top bearing should be held in place by a washer above and below the CNC bearing holder. So when assembling you screw one screw in from above and the other in from below. This way the washers stop the bearing from moving either up or down.
Once this part is build it can also be mounted to the side frame. Having done this the side frames can be brought together and bolted to the under tray. This then gives the solid frame onto which the rest of the T-Rex parts can be mounted. Don't forget to add the canopy mounting pins before bringing the two frames together, they can be mounted afterwards but it's a bit more difficult to get at the screws to do the mounting.
Heliup provide a small carbon fiber gyro mount platform. This can be mounted in one of two locations. It can be seated in the traditional place behind the main mast. Alternatively it can be mounted at the front of the machine above the motor mount. I opted for the second of these as the gyro is afforded far more protection in the forward position.
Please note on the two pictures below that the anti-rotation slider is positioned incorrectly and should be mounted to the front of the CNC mount not behind it. See the picture bottom right of the ones below for correct mounting.
Once built the frame is absolutely rigid and feels incredibly strong, Corrado of Heliup assures me he has crash tested the frame (on purpose?) and it has proved to be extremely resilient.
Completed weight of 81 grams.
As far as the actual frame goes that is the build completed. However, the Heliup frame introduces eCCPM to the stock T-Rex and therefore some more work is required to get the servos mounted correctly and setup. Here I must point out that the Heliup frame is designed for the Hitec HS56 servo and Heliup do not recommend trying to mount servos other than this particular one to their frame. The HS56 is a superb micro servo, so I certainly have no argument with this as a good choice, although if you are converting from a stock T-Rex and don't have this particular servo then you have some additional costs to consider in purchasing this upgrade frame. As a word of warning, I attempted to fit Futaba 3107 servos to this frame before trying the recommended HS56 servos and it was very much less than successful.
OK, so onwards to the servo installation. The servos our mounted with their horns inwards towards the center of the frames. In order to do this the HS56 servos need to be altered slightly, they come with the possibility to be mounted from the side using a plastic tab, this needs to be removed to allow the servos to sit flush against the frame. I removed this with a hobby knife without any difficulty. Be sure to mount the longer and thicker single servo horns to the servos and do this before you mount them into the frame as you won't be able to get at the servo horn center screws after the servos are mounted. In order to get the servo horns position correctly before mounting make sure that the servos are all at their mid position and then mount the servo horn at 90 degrees to the servo case (ie. midway through it's movement when mounted to the frame). Heliup don't provide any servo control rods with the frame, I acquired the necessary control rods by reusing the aileron control rods from a stock kit and a spare I had amongst my various bits and bobs.
Some pictures of the servos in their mounted positions :
Following servo installation care needs to be taken to tie wrap the servo wires to the frame such that they can't make contact with the main gear. Having installed the servos the tail boom and undercarriage can be mounted to the frames, the rotor head and main gear installed and the rest of the electronics installed. The only thing to mention in this phase of the build is the vice like grip the tail boom clamps have on the tail boom, far more capable than the stock clamping system.
The motor is very easy to install in to the motor mount, just remove the gyro tray and you have full and easy access to the motor mount screws. The mount is machined with slots that allow the movement of the motor back and forth to get a good gear mesh. The frame provides adequate space for all components to be installed far away from each other to not have to worry about electrical interference. For the build documented here I mounted the ESC and separate BEC underneath the battery tray, the receiver in the rear of the frames and the gyro up front on the provided tray. This leaves ample room for batteries to sit on top of the battery tray. Users of long packs like the TP2100 may want to mount the ESC above the battery tray and the lipo beneath to take advantage of the extra canopy length down into the nose of the T-Rex.
Just to finish up on the frame build here are some completed shots of the frame with all the T-Rex mechanics installed :
Having completed the build, installed the servos, gyro, ESC and receiver it was time to do the eCCPM setup. I'm not going to cover this in detail here and will produce an article on this at a later date. However, it is worth noting that the supplied servos and configuration allowed for a very easy eCCPM setup which provides plenty of throws for both aileron and collective. In fact on the collective I could get far more than +/- 10 degrees of pitch but decided to stick with the normal throws as I have never needed more than +10 or -10 of pitch. Also, due to the quality of the HS56 servos I did not have any interaction to try to tune out of the servo movements. So all indications are that this was going to be one very precise flying machine.
Having completed the build and setup it was time to try that first hover. I fitted Align carbon blades with the stretch boom as my configuration. I also installed the AON 3000kv motor but matched to a 5S configuration of Kokam 1250mAH 15C cells. I wanted this to be a hot setup and was rewarded with a headspeed of 2700RPM running off a 9T pinion. It wanted to go faster but I dialed this out on the throttle curve as vibration tends to occur in the region of 2800RPM+.
Lift off was very smooth and immediately I could feel the impact of the eCCPM configuration. The T-Rex was remarkably stable and just sat in the hover rock solid. Cyclic was very precise, far more so than on any non eCCPM configuration I have tried. Collective response and precision was awesome.
I spent some time just flying small circuits and lazy eights, some power climbouts and piros just to get a good feel for her new flight characteristics. This was the best my T-Rex has flown, ever, period! I should point out that the machine is not just sporting the carbon frame, other items installed were the Heliup tail case, pitch slider, flybar levers and CNC upgrades for the mixer arms and swashplate. However, the great flight characteristics are coming directly from the eCCPM servo configuration and the balance of the machine as a whole.
Next steps are to take the T-Rex out for some more advanced flying and see how she holds up. If you have seen the Heliup videos then no doubt you will have witnessed Corrado putting one of his machines with this frame through it's paces, so in many respects I don't feel the need to provide advanced flight commentary on this frames capability when you can see for yourself.
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