Trex 450 Sport - Second crash - two servos out

[James A]

I'm starting to get frustrated with my Trex 450 Sport now.

Having had a first crash in my opinion due to a servo failure (of course I may be wrong but...) I received a replacement DS410M which I fitted a few weeks ago. Having flown about half a dozen times since then I've now just had another damaging crash and it appears that two of my cyclic servos are now no longer responding. The worrying part is that both crashes resulted from the same erratic behaviour of the heli. Basically on both occasions the heli just started to go upwards at a high rate and somewhat backwards, dropping the throttle didn't appear to have too much affect. Given I was just doing hovering practice in my garden and had to react quickly, the only course of action to prevent it flying into my neighbours house was to drop the nose down and ..... smash, I didn't manage to pull it out of the dive before it hit the ground although I'm not sure if it was really responding to me at that point, these things all happen so fast.

Anyway, after picking it up I reattached the battery only to find that neither the pitch or aileron servos were working. Unlike my first crash where it was only the aileron servo that didn't work and was completely dead this time when powered neither servo would respond to stick inputs although they were resisting movements by hand. When I rotate them with the power off one sounds fine and the other sounds as though it may now have gear issues as it's somewhat noisier than before when moving down.

When this happened the first time I questioned the servo's and did wonder if I should swap them all given peoples opinion on the DS410M but I was give a replacement at a discounted rate so I stuck with it. Now I'm really questioning what to do as I'm losing faith in the Heli given this tendency to suddenly start climbing rapidly (and no it wasn't wind doing that). What's the likely hood it's a servo issue given on both occasions they aren't working after the inevitable crash. Alternatively the radio / receiver I'm using are also new, Spektrum DX8 set, so should I be questioning that lot?

Are there any test's I should carry out to try and identify what I can only class as this intermittent problem.

All help is greatly appreciated

[wayne123]

I think you need to check you have no pushrods binding at full movement, but unplug 2 of the motor wires before you try this, also check that each servo lead is plugged into the receiver I know that these can be tight to push in but check you have them pushed all the way in.

[del19_82]

There has been a few documented failures on the 410 servo's, my 450 has Hitec servo's in it that were added by the guy i bought it from due to the failures of the Align servos. I know that some people have used them without issue but for my peace of mind i would change them anyway

[PeteStewardson]

Surely if it was servos you wouldn't have the heli climbing when you're dropping the throttle? Which servos are failing? Same position each time? Or is this the servos you didn't replace that have fialed as they were damaged in the first crash and you didn't know?

[Lynx.1677]

Many new pilots overtighten the DS410;s which leads them to overheat and fail. Check they are not too tight. They literally just need to be screwed in until you feel a little resistance. It could also be an Rx issue. I have heard of many failures caused by dodgy Rx in the past. I guess if it happens again you will know. Personally, never had any issues with the DS410's once I knew not to overtighten them. I also use the Savox SH0257MG which is the same servo but about a tenner cheaper.

[PeteStewardson]

I use the same Savox servos and have had no issues so far.

[amh]

Many new pilots overtighten the DS410;s which leads them to overheat and fail. Check they are not too tight. They literally just need to be screwed in until you feel a little resistance.

Thanks - I was not aware of this.

I had the same issues with my ds410m's and replaced them all quickly after I had 2 consecutive Pitch Servo's fail causing crash damage.

I am also now running Hitecs in my 450 sport as suggested above.

I just lost all faith in the 410's and from having read reviews on here I was not the only one and appears still not.

[Lynx.1677]

Yeah, I understand why people lose faith in them. There is lots of bad press but I personally think it's a bit unfair. I too had a dud on my very first 450 pro kit, I screwed it in way too tight and it failed within minutes. I think they should have a warning in the manual or on the box. Afterall, a lot of new pilots buy the 450/250 heli's which use these servo's. For the record, I've had way more Hitec failures than Align but just one of those things I guess.

[James A]

Thanks for the suggestions. The two servos that had failed post crash were the pitch and aileron ie the ones controlling the whole front of the swashplate. Whilst I don't know exactly what happened my only explanation would be that these two servos started to rise at which point I'd push forward on the collective to keep the heli from coming backwards towards me. This would then raise the back of the swash causing the heli to rise.

Once again everything is calm and controlled when it's going your way but when it's not you're hitting the fast forward and the blur comes in. All I know is that I had the heli in a nice hover and then next thing it's going way to high and I'm struggling to bring it down.

I checked all potential binding issues after my last servo issue, so I don't believe it's that especially as I'm doing tame flying.

On the over tightening, I presume you mean the mount screws at the side, in which case I also checked that based on your comment last time.

Guess my main concern is having the DS410m servos runing at 6 volts, which appears to have been commented on alot.

One thing I had done only the other day was put an earth wire from the tailboom to the battery negative as I was sufferring from tail twitch due, I believe, to static build up. It did appear to remove the twitch but I wonder if this may have caused the issue.

Final thing, having never broken servos on my slightly smaller heli (and I have crashed loads) before how common is it to break them as the result of a crash. I would have thought it would simply be the gears that went if anything. I guess that may be the case with mine and if I opened them up they might be repairable but I don't feel like taking the chance.

By the way, what is the preferred model of Hitec, I'm just a basic flyer at the moment.

[amh]

By the way, what is the preferred model of Hitec, I'm just a basic flyer at the moment.

Either 65's or 5065's.

[James A]

So I just chatted to the main dealer who supplies the Guys I got the heli from to ask if they have come across any similar sort of failures / crashes and therefore have any ideas as to where the problem might be. At the end of it they're suggesting that it is most likely an issue with my DX8 as opposed to a servo failure cause. This may well be true as unfortunately both bits of kit are new to me so it could be the DX8 or its receiver. As always everyone remembers the issues with bits of kit so they were very keen to point out that the DX8 had had a number of major problems. I was also informed by the Guys that the DS410Ms are now much improved as they fixed the core issue with not being able to take over 6V and can allegedly now run up to 7. Well I guess I may just go down the line of having the DX8 checked out as well as fixing the Trex, but one things for sure, I won't be flying it this weekend.

[James A]

Just opened the damaged servos to check the gears and everything looks fine. After taking the gears out and connecting the servos to the receiver I can get it to respond to stick input although I have to coax the servos motor into life whenever it stops. So the issue with both servos is a lack of torque to get them to start spinning when required, other than that they respond to changes in the pot and do spin without gears in and to some extent with the gears in. I think the extra friction from the gear even though it's small is enough to stop the servo from kicking in as it currently has so little torque.

I guess the question is does this point to a servo failure that should be covered by the manufacturer or one down to the crash. I was expecting to see at least a little gear damage but there was nothing. The Trex was bought as a super combo so the only non Align element I have introduced is the receiver, I guess that's why I feel a bit miffed that I should have to stump up for a set of new servos. Even if I just get these replaced and ebay them it would be something towards covering my costs.