450 Pro tail locking at full head speed - RC Groups
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Aug 20, 2012, 10:42 AM
Registered User

450 Pro tail locking at full head speed

Hi, I have a EXI 450, and have had lots of problems with it, but after replacing parts with align I have almost got a working heli... the problem I have now is that the tail is locking at 0 when at full head speed.

I was using the EXI tail, but could not lock it down after trying different gyros and tail servos. I finally got it somewhat locked down using a 401 and Henge servo, but still had some wierd drifting...after removing the tail I found that one of the grips bearings were gritty. I replaced the entire tail with the align until. But now the tail is locked a 0 when I get to full head speed. If I spool up in rate more I can move the tail, but this movement decreases as head speed increases until at 80% I lose all tail movement.

The tail is the Pro tail with the counter weights on the blade grips so I dont't believe I need to chinese tail mod. The tail is set to 90 on servo, and tail slider, the tail is very smooth on the bench without any binding. I have tried both leading and trailing control but have the same problem with both. I have checked the bearing and both grips run smooth without and roughness...

Can some help this has been going on for weeks and I am ready to throw the thing in the garbage...

I also have HK 500 and HK 600 both fly perfectly... I am using the same setup approach to the 450 but cannot get the tail working...

I have also read everything I can find about 450 tails, including the bearing problems, chinese mod etc...

Thanks in advance...
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Aug 20, 2012, 11:37 AM
Registered User
minbari's Avatar
maybe the servo doesnt have enough power to move it once it gets to full power.

have you tried moving the ball on the horn closer to the shaft on the servo. this will give the servo more effective power.
Aug 20, 2012, 12:37 PM
Closed Account
I believe there was a known issue with the 450 and 500 Pro tail, where there is a missing washer that allows the bearings to be pressed on from the side when spun up. The spinning force will lock the bearing down and the tail will lock up. If I remember correctly, Align came out with a V2 tail spindle that was just a bit longer to allow for the proper washer to be placed in the tail. It sounds like you may still have the V1 tail hub without the proper spacer installed. The bearings may act and feel perfectly fine by hand. It's only when spinning when you will have enough force to lock it up.

There are a few discussions here and on Heli Freak, and you can see this users tail would lock up to the point the tail rod would just bend. https://www.rcgroups.com/forums/show....php?t=1649318
Last edited by Xrayted; Aug 20, 2012 at 03:39 PM.
Aug 20, 2012, 03:14 PM
Registered User
thanks, I noticed that the EXI tail had 2 shims, the tail I got was from Helidirect was this one...


I thought this would be the latest version, the bearings are held in place so I cannot check for shims...

Is there a way to fix this?
Aug 20, 2012, 03:37 PM
Closed Account
Originally Posted by Chiblue
thanks, I noticed that the EXI tail had 2 shims, the tail I got was from Helidirect was this one...


I thought this would be the latest version, the bearings are held in place so I cannot check for shims...

Is there a way to fix this?
It appears the only fix for the 450 is better bearings. I was originally thinking there was an updated hub, but that is for the 500Pro. I have the 500 Pro and there was a similar issue where the V1 model was shipped missing the washers which caused the same issue. Align corrected it in later models. It appears after reading about it for a bit that the design of the 450 is what it is and those with the issue have just been replacing the bearings with better ones.

Read through the link I posted to others with the issue as well as the HF link posted, and they discuss the fix there.
Dec 11, 2012, 04:33 PM
Software always has bugs
Replace your gyro pad first with a thicker one to see if that helps.

I experienced the same issue with the EXI-450Pro tail, but my gyro is an Align GP750, tail servo is an Fut S9650, and the gyro pad was a double sided gel pad. My problem was with the gyro gel pad, and I replaced it with a 3mm foam pad. Everything went smooth after that. Read on if you want to see my approach to get a solution.

- First, using gel pad, I Loctite all screws in the tail, and my tail wagged randomly. In this case, I had a lot of plays between parts such as grips, slider, and L-shape control arm.
- Second, still using gel pad, I replaced the whole tail with my Trex-450ro tail which has very little plays between parts, and the tail went nut at half of the throttle.
- Third, without know the cause, gel pad in place, I took my EXI 450ro back and started to disassembly the whole thing. I replaced the tail shaft (EXI gear was very bad) with a Tarot part. Put a couple shims in the tail shaft to lock it in the tail case. Add a thin layer of super glue to L-shape control arm to eliminate the play (careful not to lock it.) Remove all shims, and Loctite all radial bearings in the grip. At this time, the tail grips are smooth, but the tail was not locked in at all.
- Fourth, gel pad still with the gyro. Even the EXI slider was very smooth; I replaced the tail slider with the Align part. Tail still did not lock, but vibration was reduced to a level that I can hover the heli.
- Fifth, I replaced the gal pad with a 3mm pad, and the tail was solid and locked in even at very low gain.
- Finally, I put all EXI tail back together except the shaft, and the tail was rock solid. I am still flying my EXI-450Pro occasionally after work, and it's been working very well.

My conclusion is using the closest hole on the servo arm for the 450Pro. Eliminate the play on the tail with Loctite or replace with better quality parts. There are a few site selling the upgraded tail with thrust bearings, but I don't think we need that. 450Pro heli runs at very high HS. Therefore, it has more high frequency vibration than a larger one, so use a thicker double sided foam tape for the gyro to eliminate the vibration issue. Hope that helps.
Dec 12, 2012, 02:32 PM
Zippy Puffer
2Doggs's Avatar
I suggest you run the heli on the bench, with the main blades removed, and with the tail control rod disconnected from the tail servo. Then see how much force you need to move the tail rod with the heli spooled up.

I presume you aren't using anything out of the normal range for motor kv and pinion.
Dec 12, 2012, 03:14 PM
Need More PURPLE !!
Dejavu*Xion's Avatar
I had the same problem with one of my 450's a couple months back chiblue....Xrayted is spot on with his advice. +1

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