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Old 12-02-2008, 03:51 PM   #1 (permalink)
Bert Kammerer
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Posts: 1,265

Join Date: May 2005
Default T-Rex 250 Tail Issue - Official Statement from Align

Align in Taiwan has determined that the issue that is currently affecting some 250's is attributed to the tail blade grips rubbing on the shoulder of the tail hub. Due to manufacturing tolerances, apparently there are some tail hubs that have more material in the shoulder, which is allowing the grip to rub against it during side loads when the tail is spooled up causing excessive binding. There have also been some inconsistencies with the hub thread depths and the bearings are preloaded too much to the point where they can't handle the side loads induced either.

New hubs are currently being made that address this issue, the new hubs will include a single bearing instead of two on each grip. The new bearings handle side loads better also. In addition, all kits manufactured as of this week are already going to include the new hub and bearings.

There are a couple of ways to fix this problem for those of you having issues:

---------- Fix 1 ----------

Remove your tail blades, then remove the bolts that hold the tail blade grips to the hub and replace them with the bolts that are holding your blades to the grips. In other words, replace the bolts that are holding the blade grips to the hub with 1mm longer bolts. There should be a couple of extra bolts in the spare parts bag that comes with the kit too. This will allow the bolt to bottom out against the hub without excessively preloading the bearings, it will also increase the clearance between the tip of the blade grip and the shoulder on the hub.

---------- Fix 2 ----------

Remove the tail hub / tail blade grip assembly from the helicopter. Then remove the blade grips from the hub. Use sand paper or even a dremel tool and try and remove some material from the hub shoulder. You'll need to remove enough to prevent the grips from rubbing against it. Re-assemble your tail and install back on the helicopter.


How do you know if your 250 is OK? Well, of course if you are flying it and your tail is holding then you don't have the problem, but basically when you spool up the helicopter at about 60 to 70% throttle without your main blades you should be able to move the tail push rod back and forward and the tail pitch slider should move all the way to both ends. It will require some force (about 10 oz approx is normal), but the slider should move both ways without bending any tail parts, including the tail pitch arm or the push rod itself.

There are many threads out there where people are recommending beefing up the tail pitch linkage arm or changing the tail push rod to a carbon rod, etc. These are simply fixing symptoms of the main issue, they are not correcting the actual problem, but masking the symptom itself! The tail pitch linkage arm as well as the tail push rod are more than adequate and strong enough to handle the forces required to move the tail on this helicopter provided there are no binding issues.


Assurance R/C (the US Align distributor) will replace your defective hub if you are experiencing issues with the tail. Simply contact them at [email protected].

Please allow a few weeks for delivery, the factory has corrected the issue already, but it will take a little while to make enough of these and have them shipped over.

Not all dealers in the US purchase their Align helicopters from Assurance R/C. If Assurance R/C cannot find your serial number when you email them, then please contact the dealer that sold you your 250 as they will be able to get a replacement from their distributor.

Also, if you are outside the US, please contact your local Align dealer or distributor for a replacement as Assurance R/C will NOT be able to replace it for you.
Bert Kammerer

Last edited by Bert Kammerer; 12-10-2008 at 09:09 AM..
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