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T-REX 700 › 700E DFC tail vibrations
10-29-2012 12:00 AM  5 years agoPost 1
CBell

rrApprentice

Nova Scotia, Canada

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Hi Everyone,

I understand that some of you are experiencing tail rotor vibrations with the new 700 DFC model. Unfortunately I have not personally had the problem, so I am unable to provide a definite solution. All of the pre-production helis were smooth, as is my personal production model. We'd like to figure out if there is an issue, and if there is, provide a solution.

All of us with Align have been brainstorming to help rectify the issue some of you have had. Anyone that's currently having a tail buzz problem and is willing to work with me via PM to eliminate it, please send me a message. The more info you provide the better.

Thanks,

Colin

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OS Engines
Castle Creations
Futaba

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10-29-2012 02:03 AM  5 years agoPost 2
jschenck

rrProfessor

La Vista, NE.

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just a thought but many tail blades I check are not exactly balanced. I have to add a bit of scotch tape to get them to balance.

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10-29-2012 03:36 PM  5 years agoPost 3
CBell

rrApprentice

Nova Scotia, Canada

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Yes, agreed. The higher tail rpm makes the model more sensitive to vibs produced by out of balance blades. Please check them with a high-point type balancer, or a sensitive scale. Also remember to check the span-wise balance if you're using a scale.

Thanks for the input jschenck.

Colin

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OS Engines
Castle Creations
Futaba

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10-31-2012 03:41 AM  5 years agoPost 4
gator

rrNovice

Albuquerque, NM

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I've had the same problems with an X7 and my Trex 700DFC and the solution was changing out the tail blades to Edge 105s. I would not have believed it had I not seen it for myself, but the tail vibrations are gone!

When rotating the Edge blades in the blade grips, they move smoothly through their ark. Other blades don't move smoothly through the ark; they kind of catch when centered up. I think it may be the brass sleeve that the bolt goes through; it's slightly wider than the base of the blade.

Scott

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10-31-2012 07:04 PM  5 years agoPost 5
Dino Spadaccini

rrElite Veteran

USA

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a solution
Ok so you all know my self and a few team guys have been working on this issue what I have seen is some have it and some don’t, One of my Dfc does so that being said now let me tell you what I have come up with

On the heli that is good no Vib in the tail its a stock heli now on to the other one which is stock also here is what I have tried to find a solution

I want I found the difference is between the two helis was how I shimmed the main shaft, On the good heli I used the med shim that allowed the Jesus bolt to slide in easy with out any force or having to kinda screw it in. there is a slight amount of play in the main shaft up/down like a tick of play,

On the heli that had the vib I change everything out from the good heli to the one with the vib and could for the life figure out what could be causing this Until I swapped out the heads which included the shim and vib was gone, put the other head back on and vib back, I ripped the head apart and swap everything out still there until I just happen to pick the heli up and felt the small tick and it hit me, I put all the part back to the helis and shimmed the main shaft with a med shim and the vib was gone put the thick one back and it was there so now I swapped out tails and it seems no matter what tails I used the vib was there once I put the med shim in gone, now I put the lower bearing block in and did the test again with thick shim vib was there with the med shim gone.

So with all this being stated by me, here is what I am asking the ones with the vib check your shimming on the main shaft and see if you are using the thick one try the med one and let me know if that fixes the problem if so what I did to remove as much of the little play in the main shaft was to sand down the thick shim on a flat surface and keep fitting it until the jesus bolt went easy there is barley any play the reason I did this was I did have any of the thin shim to work with.

In closing play try and see what happens when you try this and please post here is I can see what some of you come up with

Thanks Dino Spadaccini

RIP Roman JR
Capt USA Align Factory Team Align - Conquer Your heart
Team Futaba

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10-31-2012 09:06 PM  5 years agoPost 6
raptormandan

rrApprentice

springhill florida

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tail vibe
for me....it was tail blades...bad umbrella gears front and back.changed all 3.......vibe........gone....25 flights later ......still smooth....rmd

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11-01-2012 04:58 AM  5 years agoPost 7
HUTCH964

rrKey Veteran

Taylor,Texas 76574 local airport T74

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Thanks for all the replies Amigos as I getting ready to setup my 700e DFC next week and will let y'all know what happens & what is found...

Keep it coming gang!

.

Tim

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11-01-2012 01:17 PM  5 years agoPost 8
Dino Spadaccini

rrElite Veteran

USA

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ok great

RIP Roman JR
Capt USA Align Factory Team Align - Conquer Your heart
Team Futaba

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11-04-2012 09:33 PM  5 years agoPost 9
TSK UK

rrNovice

UK

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Have a read, this may help

http://www.rcheliaddict.co.uk/t-rex...ause-found.html

Authorised UK Agent for TSK Helicopters

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11-04-2012 11:41 PM  5 years agoPost 10
CBell

rrApprentice

Nova Scotia, Canada

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Hi TSK UK,

Thanks for the link. This is something I've noticed with all of my Align models from day one. I usually have to shim the vertical bevel gear shaft to accommodate for how the gearbox sits in the frame. I've actually had to do this with every gear driven heli I've owned.

Being in the hobby for 15 years, I'm used to having to shim shafts and gears to get proper mesh. Thankfully the 700 gears are large enough that the gear backlash is not overly critical. I've built models like this for a long time, and sometimes forget that what used to be common practice may not be anymore, as our models get better and better.

On that note - I have flown with the play there, and with it removed. I can tell no difference, other than knowing in my mind it's not "perfect".

Cheers,

Colin

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Align
Thunder Power
OS Engines
Castle Creations
Futaba

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11-05-2012 04:14 AM  5 years agoPost 11
Snake007

rrNovice

Mayfield, KY, US

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I had the Buzz on the 700E DFC. About the third flight the tail shaft snapped and the tail went flyiing off. Mostly saved the heli. Back to the bench replaced every part of the tail and replaced the torque tube. Buzz still there. Went through it again and on test flight as soon as I hit stunt 1 the tail shaft snapped off again. Again I mostly saved the heli. This time I replaced tail boom torque tube all gears in the tail housing and blades. I also went through the head and for something to try I replaced main shaft and spindle. Test flight no buzz. Put about 10 flights on it and all of a sudden buzz came back and the heli started a fast piro. This time I was not so lucky. The heli was on its side when the tail let go and low. It smashed into the ground and broke everything. The only thing I saved from the crash was the motor esc and 2 servos, everything else was bent or broke. I threw that one in the trash.

I have a bunch of Trex helis with no issues so Im thinking I had to have done something wrong so I purchased a new kit and did the first test flight today. I have the same buzz in the tail. I will try some of the things listed sbove and I hope one of them corrects the problem

On another note, when I built the first kit I put two of them together. The second one was for a friend and he has no issues.

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11-05-2012 10:06 AM  5 years agoPost 12
Racedrvr

rrNovice

Kentucky Lake/Chicago Burbs

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The torque tube can be bent quite easily during installation. It can be difficult to push into the boom if you don't know the technique. I have checked new tubes and they aren't perfectly straight either. You don't even need a dial indicator as you can see the "wobble" just by laying the tube/bearing assembly on the workbench and spinning it slowly. We checked a new 700E at the field yesterday by pulling the tail gearbox off and rotating the head. There was visible runout of the TT at the tail. His machine had visible and audible vibrations. He hasn't yet checked his tail blades for balance yet though.
I put the bearings in the rubber grommet and pushed them into the tail boom using the plastic tube they came in to position them properly, and then put the TT through the bearings. It only takes a gentle push/wiggle. As difficult as it is to push the rubber bearing holders through the boom I am thinking they aren't going to "walk" up and down the length of the boom even though they aren't glued to the TT. I did also check the stock tail blades and mine were fine balance wise. My tail is absolutetly dead still with no visible or audible vibration.
I have been looking for a carbon clad aluminum arrow shaft that could replace the soft aluminum torque tube. I would think the stiffer spine may reduce "whipping" of the torque tube in the boom. It may be something to look at.

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11-06-2012 07:33 PM  5 years agoPost 13
Snake007

rrNovice

Mayfield, KY, US

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update,
After seeing that the TT had some wobble when the tail box was off I installed a new TT. Spun the rotor with the tail box off and had the same thing. I was very carefull while installing the TT and I know I did not bend it. I then removed the TT and removed the bearing and checked, The TT was not bent. I then put the bearings into the boom and installed the TT with no glue. The TT turns true and has no wobble at all. I do not know that this will fix the problem but it is better. Will post the results after test flight.

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11-06-2012 08:14 PM  5 years agoPost 14
TSK UK

rrNovice

UK

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Snake007,

I think you need to get somebody else to check your model .... maybe chat through how you are building. It is possible you are over tightening something or indeed install something incorrectly. To have such a severe failures of the tail more than once is very unusual.

Authorised UK Agent for TSK Helicopters

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11-06-2012 10:35 PM  5 years agoPost 15
Snake007

rrNovice

Mayfield, KY, US

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This is not my first heli and it is not my first Trex 700, Also there are a number of people having the same issue so I do not think it is something that I am doing. I have been building and flying helis for over 10 years and many different brands. Point is I am not a newbie.
That being said it is possible that I did something wrong but I dont think so. I have now put 3 of the 700E DFC HV together and 2 had o has problems and the other one has no issues at all. Neither of my 2 nitro 700s have any issues at all.
I think there are a few factors to consider, On this model they increased the tail speed which will make any problem worse. If I had the same run out on tht TT with the nitro I do not think it would be an issue, However on this model I am running a higher head speed and the higher gearing on the tail could cause problems. I am still testing to find the problem. The Heli is all assembled and ready to test. It is rainning here so maybe tomorrow.

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11-07-2012 07:38 PM  5 years agoPost 16
Snake007

rrNovice

Mayfield, KY, US

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Did the test flight on the 700E DFC and the buzz in the tail is a lot better but not gone. Going to try a different set of tail blades next.

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11-08-2012 07:11 PM  5 years agoPost 17
Snake007

rrNovice

Mayfield, KY, US

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Update on tail vibration,
After I got the TT turning true the vibration was better but not gone. I then put the tail blades on a balancer, the CG of the blades looked good but one blade was heaverier than the other one. I do not know how much as I do not have a scale that will measure it. I took a new set of blades and di the same thing with the same result. I took the heavy blade from each set and they balanced perfect. I then did a test flight and it was a lot better but not as good as I wanted it. I then looked at the tail grips and there was side to side play in the grips. I added a 0.010 shim between the bearing and the thrust bearing ( There was already a 0.012 shim there)this took almost all play out of the grips. Did the test flight and it is the best so far. I can no longer see any vibration in the tail but I can still hear a buzz. The buzz is not real loud but I can hear it. My plans are to fly it like this and see how it does.

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11-08-2012 11:32 PM  5 years agoPost 18
raptormandan

rrApprentice

springhill florida

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tail buzz
just keep and eye on the lever arm....only a little 3mm holding it in...i stripped mine out do to tail vibe..if you loose that be prepared to auto.but like i said switched to rail tail blades and umbrella gears .. all is well after now easy 50 flights

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11-10-2012 02:17 AM  5 years agoPost 19
Snake007

rrNovice

Mayfield, KY, US

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Flew the 7oo DFC today with some friends. The tail vibe was a lot better but after a friend flew his I could tell mine still had a buzz. So my friend gave me a set of Rail tail baldes to try and no buzz at all, He also had a set of Curtis tail blades and I tried them also and again no tail buzz. So now I can only conclude that I had a number of issues but the main one being the tail blades.

Now for some strange info. Another friend has some scales the measure to the 100th of a gram. He took 2 sets of Align blades that I had and weighed them. The resuts are as follows

The two blades first flown today...they were the "heavy" ones. 6.70 and 6.68 grams

The used "light" blade during bad vibes 6.68 grams

The unused "light" blade 6.66 grams

The two Rail blades from Paul both weighed exactly the same at 5.48 grams

Going to try to check the CG of the blades next.

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11-11-2012 06:20 PM  5 years agoPost 20
raptormandan

rrApprentice

springhill florida

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rails
hmmmmmm...... where have i heard this before.......lol

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T-REX 700 › 700E DFC tail vibrations
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