X400 Tuning - ARK Tail Case

The following is a review of the ARK tail case kit.

First some pictures of the kit contents :

Tail case kits		Contents

Included in this case is a new tail shaft as well as the CNC tail case. The tail case is made up of four main pieces, the unit that clamps onto the boom, the tail pitch bell crank mounting bracket and the two halves of the tail case with bearings that house the supplied tail shaft.

The tail case is nicely machined and anodised and the kit itself came with all the parts required for proper assembly. Included in the kit are some new bearings for the tail case. The supplied shaft is just a stock shaft and no different to the one supplied in the X-400 kit. Assembly of the tail case is relatively straightforward and aided by the provision of some very nice clear instructions showing how the various parts screw together. Be sure to use plenty of loctite as any of the tail case screws coming undone would be quite catastrophic. I used blue 243 loctite on my case. Also supplied in the kit are some spacers to make sure that the pulley has no lateral movement once mounted into the case. Below are some pictures of the assembly and the supplied instructions.

instructions		tail case sides

clamp and pitch slider mount		clamp

supplied screws, assembly items		tail shaft assembly

tail shaft assembly		tail shaft assembly

clamp assembly		belt tensioner fitment

belt tensioner		pitch slider

Having built the main part of the tail case the next job is to mount the tail rotor, tail pitch bell crank and then mount the entire unit onto the tail boom. Things to remember when building this tail case are that the belt must be on the pulley when you assemble the two tail case side frames together. You can't insert the tail belt later without taking the gearbox apart. It is also worth exploring why one would buy this particular upgrade. The first attraction for me is the open gearbox design which doesn't gather dust and therefore can reduce wear and tear on the pulley and belt. Secondly CNC tail cases make a good mounting point for the tail pitch slider. Without the benefit of an upgraded tail pitch slider most tail cases make very little difference to the performance of the helicopter. Below you can see pictures of the stock bell crank and tail pitch slider being fitted.

Full frame view		120 CCPM servo config

Having fitted the original stock unit I didn't particularly like the smoothness of movement that the stock unit provides. To really take advantage of the CNC tail case I would want to fit an upgrade bell crank and tail pitch slider. However as neither are available I refitted the stock items. Having completed the above it was time to mount the gearbox onto the tail boom. At the time of testing/building this tail case I was also looking at an extended carbon boom. The tail case was to be mounted onto this boom. This did not go well and a light sanding of the tail boom was required to get a good fit into the tail gearbox clamp. It is also worth noting that this gearbox will only function correctly and clamp onto the tail boom if it has been assembled correctly. If the tail boom clamp is the wrong way round it won't clamp at all. Only one side of the clamp is threaded, the screw should push through this and then thread into the opposite side of the clamp. This ensures that when you tighten up the screws the clamp does squeeze onto the boom Two brass spacers are included to make sure that the case fits and clamps without bending the vertical tail fin.

Full frame view		120 CCPM servo config

Conclusion

Overall this tail case is an improvement on the original stock units. The quality of the machining is very good and all the various parts screw and fit nicely together very nicely. The unit is made up of four separate parts which I'm not so keen on as I prefer a simpler construction with less screws to come undone. However, with adequate use of loctite this should not be a problem. The case does not have any locator to stop it spinning on the boom and so relies on a very tight clamp to make sure that no rotation occurs. The clamp system is adequate but not the best system I have come across.

In order to really take advantage of this tail case an upgrade tail pitch slider should be used but at this point I am not aware of such an item for the X-400.

Anyone wanting to improve the tail gearbox and add a very bling look to the X-400 should consider this upgrade. However, if you are looking for performance improvement then without also upgrading the tail pitch slider this unit does not offer any performance improvement. It can only offer reduced wear and tear on components that might occur with the stock enclosed tail case.