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Thunder Raptor 90/G4 Thunder Tiger Raptor 90/G4 Helicopters


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Old 09-21-2012, 04:59 PM   #1
jwatts007
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Default Broke rear ELE mount again....

Hi fellas I have broken another rear servo mount, I have also had the front mount break once that time the lugs of the servo broke as well, I am lucky that it has never led too a crash and have only noticed them broken when back on the bench, has anyone else had this problem, I only know of one other that has had a front one break on him.....
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Old 09-21-2012, 11:45 PM   #2
white95gt
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wow, that doesnt look good. you hit the ground or fly hard 3d?
i put my main frames together tonight and didnt install the servo mount for elev yet.
its looks pretty strong, maybe you got a bad batch, first run production.
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Old 09-22-2012, 12:21 AM   #3
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Thought it may be a 1st run thing when the 1st one broke, I then had a beefed up one made as I could not get the part, then the front one broke so fitted all new original parts recently, this one did not last long at all, I only do sports flying nothing hard at all, seems strange I am having this problem as others with there G4s flying like demons have never had one break....

No the model has never been crashed......

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Old 09-22-2012, 01:38 PM   #4
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is yours fbl, i wonder if the fbl models are cycling so often they are stressing the bracket to much. you said you had a stronger one made, why did you go back to stock, was it to heavy. do you have a pic of the stronger one.
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Old 09-23-2012, 03:02 PM   #5
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Hi Fella...I had one made as I could not get parts for it at the time...basically it is a little thicker and wider than the stock one...here is thread that a friend started when it 1st happened with pics of the mounts http://www.rcheliaddict.co.uk/g4/665...t-failure.html anyhow what happened then was the front one broke ruining the servo case...so I purchased the parts and fitted them wanting it stock and all as new and thinking that it was just a faulty part...it lasted no more than 6 flights breaking the servo lug off again in the process...yes it is FBL I would like too know why this is happening to mine as other who fly a lot harder than myself x10 do not have any issues with there's...could it be the JR servos for some reason or is it binding somehow I really need to check it out now...do not be put off they are great helis and my mates have never had a problem bar 1 who has had a front one go read the thread yourself....Good luck and enjoy your G4.....
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Old 09-23-2012, 06:39 PM   #6
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i just saw in the first pic you use the plastic "washer" then the metal one on the outside closest to the nut. maybe try all plastic and see what happens.

and this heli is really nice, goes together easy and the fixed lenght control rods are a breeze to setup the heli. im really impressed. i thought the x50 would be nice, but since i got this one im really pleased.
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Old 09-24-2012, 02:30 AM   #7
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The only other thing that is different on mine too all the others I have seen is I am using normal servo horns the balls are a little further out than the TT ones that come with the kit...I wonder if this could be adding more leverage too the mount enough too snap them...the reason I have these horns is when I built the model the JR fitting were not available.....
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Old 09-26-2012, 04:42 AM   #8
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I know they are supposed to be 6.6mm thick or thicker. If they are less than this, that could be the reason. Also if there was a hardening issue with a batch.

Other than that binding would only be the other possible cause.

Good luck with it.
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Old 09-26-2012, 06:34 AM   #9
gwright
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There is some "offset" built into the bellcranks both up front (on sides of frames) and on the elevator, allowing use of the stock straight metal arms which give you some reduction in movement (I forget, maybe 1.7 to 1 or 2 to 1), allowing use of the very long levers to reduce interactions caused by differential movement. To illustrate, If you watch all three pushrods from the side of the heli, they remain parallel throughout collective movements, plus the angle changes very little due to the long bellcranks. This requires some ratio of reduction from servo to bellcrank . By using another servo wheel that is not exactly the same length you are introducing binding at the extremes of movement. Actually there would be binding anywhere away from center, it just would get very noticable at the extremes. This is going to constantly load the mounts back and forth. I still can't understand that sort of breakage as the mounts are very strong aluminum parts and the rubber grommets should absorb some movement, however, I think the binding should be eliminated first. To check how much binding there is just snap one of the links off the servo wheel (top one would be easiest to see) then move the servo through rotation to the ends and see how "out of phase" the link is with the ball. You should see what I'm talking about fairly easy.
If you must use plastic or metal arms that aren't the ones from thunder tiger, ensure that you get the right length, it should be EXACTLY the same as the thunder tiger servo arms.

Hope this helps!
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Old 09-26-2012, 04:22 PM   #10
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Thanks fellas I have got all the parts needed come today including the JR inserts for the horns...so I will finally be able to set it up as it was meant to be...and make sure that there is no binding and hopefully it will be the end of this happening to me.......
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Old 09-27-2012, 06:10 AM   #11
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Out of curiosity, what length were the arms you were using, and what is the stock length? I should know the stock length, but at office so can't measure, and I forget.
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Old 09-27-2012, 06:34 PM   #12
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it doesnt say in the manual but i measured just a tick under 11mm. unless your doubling that i dont see why the servo mount broke. must be a vibe or a bind.
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Old 09-28-2012, 05:13 AM   #13
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I am using the 28mm horn from Q.UK on the outer holes http://www.quickuk.eu/cat/general_pa...els.html?nav=2 2 they are about as close as I could get too the TT ones that came with the kit....
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Old 09-28-2012, 06:35 AM   #14
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I think you've found the cause. Stock at 11 per side and you're at 14 per side, so that will create considerable binding, not to mention excessive stress on the servo. Since you're apparently using very high power servos, that binding force has to be transferred somewhere. and it seams the rear servo mount is what recieved it. Did you ever snap a link off and look at how out-of-phase it got with the ball at extreme movement? With those numbers, if you rotated 90 degrees (just mentally, to make visualization in the mind easier<G>) you'd end up 3mm out of phase with the ball. At 60 degrees it would be less of course, but still a couple mm. Kinda like grabbing the servo mount post with a pair of pliers and forcing it back and forth a couple mm, repeatedly, the entire time you're flying. It would finally fatigue and crack. Come to think of it, there is a less than 1 to 1 ratio in that push-pull, with the required "offsets" built into the elevator bellcrank to netralize the differential movement, so the stress on the mount that I tried to explain above would be even greater than mentioned.
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Old 09-28-2012, 07:43 AM   #15
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Yes stock is 11mm- 22mm overall and the distance I had was closer to 25 mm over all, as the servo has had to come out to have a new top part of the case to be replaced I have not checked the servo for the binding, they will now have the TT horns fitted that came with the kit, and hopefully fly it this weekend.....
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Old 09-28-2012, 09:12 AM   #16
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sorry i should clarify what i measured, its the ball link to ball link dimension on the stock thundertiger linkage. so you where doubling plus a little the distance from ball to ball on the servo which is most likely the reason for breaking the servo mount, to much stress applied to the design of the mount therefore causing the fracture.

no big deal, you didnt crash the bird. and now that you have the correct installation i dont see why you will have this problem again. you should be smooth sailing from now on.
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Old 05-22-2013, 02:59 AM   #17
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Well it happened again broke both mounts in flight...very lucky that I somehow managed too land without any damage...4th time now...I reckon I can break them at will now with ease...
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Old 05-27-2013, 07:51 PM   #18
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Changed the setting all to a 100 in the distance boxes (had too reduce the cyclic ring after doing this)...reason I did this is the model must have mechanical mixing done through the bell cranks...otherwise how else would it fly FB or with a FBL unit that never had the setting the distance option...by setting the CH1 ELE too 70 in the V Bar and CH2 and CH3 too 99 isnt the ELE trying to get there faster than the other 2 servos causing a brief moment when the servo are fighting each other...this may be the cause of the mounts breaking...when I first built the model I had a Beast X fitted set too 140deg and no problems...the mounts started breaking when the V bar was fitted within a few flights in fact....
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Old 05-27-2013, 09:12 PM   #19
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Default Re: Broke rear ELE mount again....

could you post your Vbar file


The settings Marco posted have worked flawlessly for many. Nicks settings are very similar, ive tried both with out any issues, i belive his are 72 100 100 you'll find the exact numbers in the electric thread.


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Old 05-27-2013, 10:12 PM   #20
sjsamuel
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Default Broke rear ELE mount again....

Had a broken elevator mount at my local field on a g4 720 nitro as well.
I set this machine up originally with a vbar and had 20-30 flights. But this Heli was bought used and flown on a vbar for an unknown number of flights before I set it up.
Recently changed to a CGY750, and used all of nicks values from his 750 setup videos as the machine has the same servos. 10-12 flights in on the bench we saw the front part of the elevator mount was broken. Servo was warm, but funny thing is the entire flight was uneventful! Mount is being replaced, but I've subscribed tithe thread so hopefully we can figure out what's going on!!

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