T-Rex 600 - Align Torque Tube Upgrade

 

The following is a review of the Align T-Rex 600 torque tube tail drive.

First some pictures of what's in the upgrade kit:

 

Build Review

Although it looks quite complicated and there appear to be quite a few parts the build and installation of the torque drive is actually very straightforward. The first job is to build up the new tail boom clamp and the gearing required to take its power off of the lower main gear. Some of the parts for this come preassembled. Specifically the bevel gear which just slots into the tail boom clamp. This can only be installed one way up and it is obvious from the moulding which way it should be. There are two loose bearings supplied in kit and these go at either end of the tail output pulley. The pulley is then installed into the tail boom clamp and the two halves of the tail boom clamp pushed together. Before doing this you must insert the six plastic rods into the tail boom clamp. The whole thing is then just a push together fit. Once it is all together you can insert the supplied screws and bolt it into the back of the main frames.

The next task is to install the tail shaft into the tail gearbox. The tail shaft comes with a new pitch slider bushing (as seen in the picture above). This bushing should be removed from the tail shaft and installed into the tail pitch slider. The three screws that hold one side of the tail gearbox in place can then be removed and the tail shaft inserted into the tail shaft rear bearing. The removed side of the tail gearbox can then be reinserted onto the tail shaft and bolted into place. This secures the bevel gear on the tail shaft at the required mesh. Don't forget to go round the whole of the tail gearbox checking all of the screws for loctite.

The next j ob is to insert the torque tube into the tail boom. The torque tube comes with a central bearing enclosed in a rubber outer casing. This bearing should be glued to the torque tube right in the middle. Use a bearing weld (green loctite) to hold it in place. Once the bearing weld has set the torque tube can be pushed down into the tail boom without the bearing sliding out of position.

With the torque tube installed into the boom and located into the gearbox 'cross drive' the whole tail boom can be inserted into the tail boom clamps and bolted into place.

The tail gearbox has a single screw that is used to bolt and clamp the tail gearbox onto the tail boom. You will probably also find that the horizontal stabiliser is no longer in the correct place and needs to move slightly on the boom.

Whilst putting all of this together I was quite impressed with the quality of the parts and also the design used to keep the bevel gears at the correct mesh.

 

Flight Review

The thing you notice when spooling up for the first time is that the machine is now making a different noise. The belt drive was extremely quiet and only an occasional slap of the belt against the tail boom could be heard. The torque tube is a different story, you can hear the bevel gears whirring with the motor and pinion. It is not an unpleasant sound and adds to the turbine like sound that the T-Rex 600 makes.

I did not need to adjust my gyro having installed this upgrade. I also did not need to adjust the tail servo as the linkage lengths were almost identical.

The difference the torque tube makes is quite noticeable in terms of how the tail rotor behaves. The tail holds much better in tic tocs and the overall feel is much more solid and predictable. With the belt some slight wag could be seen due to the belt stretching slightly under load. In many respects the tail inspires more confidence when using the torque tube and the immediacy of the tail is much improved.

I did not notice any significant change in the available power, although the torque tube probably is more efficient than the belt. The efficiency gain is not really noticeable under power. However, in an autorotation the efficiency of the torque tube is noticeable in that there is more available power at the end of the autorotation.

 

 

 

 

Conclusion

Align have produced a significant number of upgrades for the T-Rex 600. The majority of them I have found to make very little difference to the flight characteristics of the machine. The stock T-Rex 600 is such a good flying machine that improving upon it with identical parts that are just made out of metal isn't really going to work.

The torque tube is a complete departure from this creation of identical metal parts. In fact it is the first upgrade to the T-Rex 600 that I have really liked. This upgrade makes a significant improvement to the T-Rex tail and produces an altogether smoother running machine. I have always felt that the tail rotor on the T-Rex 600 was one of its weaker points and this upgrade goes a long way to addressing this. The only downside I could think of with a torque tube tail drive is durability, if you ground the tail under power then it's very easy to strip gears. Align has thought of this and the various gears can be bought separately and cheaply.

If you are looking to upgrade your T-Rex then in my opinion this is one of the few upgrades that is really worth while doing. The build quality is superb, it looks fantastic and the performance is significantly improved. Definitely highly recommended.

 

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