Trex 250 Pro DFC, Torque Tube Front Drive Gear (H25131) gets loose!!

[kickbackkid]

Originally Posted by A VIKING

That would be:
http://helidirect.com/align-carbon-f...50-p-10529.hdx

It's been a good boom, went through my last crash without fail. The struts were pulled out and the aluminum end fittings of the struts were bent so it went through some stress. You can break them though, just like bending the aluminum boom. The carbon boom is a hair lighter than the aluminum boom but I wouldn't change it for weight, I did it only because I like the looks and carbon fiber is a little quieter in transmitting vibration than solid metal.
Carbon fiber really hides failure very well so if you do crash any carbon piece look at it very carefully, you may see a hidden crack.

Viking

Thanks dude! I will look into that.

[lasakro]

Originally Posted by A VIKING

Lasakro,
Any question worth asking is worth knowing the answer to.
The Align 250 carbon fiber tail boom has a wall thickness of .32mm by my measurement. Should be very close with that.

Wow and I thought the .5mm one I had folded easily on a crash. Running now with 1mm wall should hold up like a brick house.

[A VIKING]

Originally Posted by lasakro

Wow and I thought the .5mm one I had folded easily on a crash. Running now with 1mm wall should hold up like a brick house.

Yup, I believe ,3 to .5mm is pretty much standard wall thickness for tail booms up to 450 size, after that I don't know what they run.
What about the support bearing for the TT shaft, will it fit the interior dimension of that tube or are you planning to run without?

Viking

[lasakro]

Originally Posted by A VIKING

Yup, I believe ,3 to .5mm is pretty much standard wall thickness for tail booms up to 450 size, after that I don't know what they run.
What about the support bearing for the TT shaft, will it fit the interior dimension of that tube or are you planning to run without?

Viking

I use the bearing w/o the rubber holder. Wrap it in a little tape until it's snug. On larger birds heat shrink does the job.

[A VIKING]

Originally Posted by lasakro

I use the bearing w/o the rubber holder. Wrap it in a little tape until it's snug. On larger birds heat shrink does the job.

Very cool.
If you have the most terrible crash you've ever had...the only thing recognizable will be that tail boom.
Super up grade.
Any problem with CG?

Viking

[lasakro]

Originally Posted by A VIKING

Any problem with CG?

No change in CG.

[beer2morrow]

lasakro, I did the same pin-hole mod as you did few days ago, and I used gorilla glue to secure everything together. The result was pretty good, I thought it would be indestructible. Put it in the heli, tried it in my hand without the main blades, guess what, the two front gears stripped. These gears have been though a crash so I thought they might have been weakened in some way, so I changed them all two brand new black gears last night, and flied it this morning. The first flight this morning was superb, i felt like this mod worth all my broken drill bits, and then on the second flight, after some piro flips and tic tocs, the TT snapped in the air.

I don't know what I'm gonna do next, I've kinda lost my faith in this thing. This is what happens when bad design meets poor engineering, or maybe they just didn't put enough effort in to this. I've had enough of this and probably I'm gonna give it up for good.

If you are going to test it, stay away from it.

[ferebeed]

I changed mine over to belt. The TT works great in the 450 & up but this should stay belt. I also changed to the old slider too. It's smooth & my timer is set for 4min & I put in around 550 mAh back in on a TP 850 mAh 45C & 65C.
Don't have to worry about the tail spinning to the right because of those gears. I love the frame layout. I had the V1 of this guy. I hated the frame. Sometimes you have to leave it a lone.
Also my tail blades never touched the ground. It was front TT gear that would fail. 3 of them.

[volar]

Have a beer2today and re group, this is an addiction, dont give up.

I have not tryed the pin mod yet, but tempted on next failure, the glue did fail, i reglued a new one but i backed off a little on tork tube as suggested by (viking). been holding since, have appox. 30 flights. these guys put up some great advise.

Keep the faith.

[beer2morrow]

Originally Posted by volar

Have a beer2today and re group, this is an addiction, dont give up.

I have not tryed the pin mod yet, but tempted on next failure, the glue did fail, i reglued a new one but i backed off a little on tork tube as suggested by (viking). been holding since, have appox. 30 flights. these guys put up some great advise.

Keep the faith.

I'm not saying that I was gonna give up this hobby stuff, but I'm just tired of part failures on this align 250. Clearly all the align engineers were drunk or drugged when they were working on this 250 back then. After I've fix the front drive gear shaft, the gears themselves would strip, and then I've fix the gears up, the TT snapped. There are litterally endless parts failures to encounter.

I think I'm gonna sell this thing and then get a goblin 500.

[beer2morrow]

Originally Posted by ferebeed

I changed mine over to belt. The TT works great in the 450 & up but this should stay belt. I also changed to the old slider too. It's smooth & my timer is set for 4min & I put in around 550 mAh back in on a TP 850 mAh 45C & 65C.
Don't have to worry about the tail spinning to the right because of those gears. I love the frame layout. I had the V1 of this guy. I hated the frame. Sometimes you have to leave it a lone.
Also my tail blades never touched the ground. It was front TT gear that would fail. 3 of them.

Could you tell us a bit more about the belt set up? Like what parts need to be changed or modified?

[kickbackkid]

Originally Posted by beer2morrow

lasakro, I did the same pin-hole mod as you did few days ago, and I used gorilla glue to secure everything together. The result was pretty good, I thought it would be indestructible. Put it in the heli, tried it in my hand without the main blades, guess what, the two front gears stripped. These gears have been though a crash so I thought they might have been weakened in some way, so I changed them all two brand new black gears last night, and flied it this morning. The first flight this morning was superb, i felt like this mod worth all my broken drill bits, and then on the second flight, after some piro flips and tic tocs, the TT snapped in the air.

I don't know what I'm gonna do next, I've kinda lost my faith in this thing. This is what happens when bad design meets poor engineering, or maybe they just didn't put enough effort in to this. I've had enough of this and probably I'm gonna give it up for good.

If you are going to test it, stay away from it.

Hey buddy, I've been in the same boat with the 250 as you. When I first got it, it flew amazing compared to my 130X.

Then trouble started developing. The Align tail servo wouldn't hold. Replaced it with a KST. Things seemed fine.

Had a few minor crashes then things started going bad. I was treating it like my 130X. You need to take the time to rebuild your 250 completely. All vibrations must be gone. I tore mine completely down and replaced my main bearings and the tail grip bearings, as well as the bearings around the tail shaft. Replaced both tail drive gears for the TT.

Now this thing is flying so amazing right now. I am doing inverted nose down funnels both CW and CCW and the tail holds perfect.

These things are what I have learned about the 250 and will keep you flying. Be sure to check these every flying day:

*Motor pinion- make sure it is not slipping and is lined up perfectly with the main gear. Can cause vibrations if not aligned.

*Main gear- make sure it is just barely tight. There should be no up/down play on the main shaft. Use red loctite...don't want it backing out.

*Tail drive gears- replace every crash, hard landing, or tail tap. The black gears are prone to stripping off the shaft and causing no tail authority. Look for the plastic peeling off the top of the spindle like an apple peel. Dead sign that you need a new gear.

*No binding in the tail slider- the tail should be super smooth. Check with the tail control rod off the ball link. Majority of the time you get loctite in the brass bushings causing binding.

*TT- make sure it is dead straight. These can be very easy to bend. Roll it on a solid surface to make sure it is straight.

If you can follow these items, the little guy should hold up well for you. If you get any vibrations at these head speeds, bad things will happen. Any vibrations can lead to screws backing out, or the tail boom snapping in half during flight like I can attest to. I would get so frustrated because I wanted something dependable like my 500 and 600.

Good luck and let us know how it goes.

[lasakro]

Originally Posted by ferebeed

I changed mine over to belt. The TT works great in the 450 & up but this should stay belt. I also changed to the old slider too.

Originally Posted by beer2morrow

Could you tell us a bit more about the belt set up? Like what parts need to be changed or modified?

I'm seriously thinking about giving the belt a shot for about $51. Align parts needed are with ~ ebay prices:

Tail Mount Gear Set H25063- $9
Metal Tail Belt Unit H25026- $23
Metal Tail Drive Gear H25079A- $9
Boom Mount- H25020- $5.40
Belt- H25028- $4.50

I think that should be it.

[beer2morrow]

Originally Posted by lasakro

I'm seriously thinking about giving the belt a shot for about $51. Align parts needed are with ~ ebay prices:

Tail Mount Gear Set H25063- $9
Metal Tail Belt Unit H25026- $23
Metal Tail Drive Gear H25079A- $9
Boom Mount- H25020- $5.40
Belt- H25028- $4.50

I think that should be it.

Have a look at H25026B, do you think it's the same casing as the dfc pro? If so, we might just get the H25075 and put it into the tail case comes with the dfc pro kit, will it fit?

[beer2morrow]

Originally Posted by kickbackkid

Hey buddy, I've been in the same boat with the 250 as you. When I first got it, it flew amazing compared to my 130X.

Then trouble started developing. The Align tail servo wouldn't hold. Replaced it with a KST. Things seemed fine.

Had a few minor crashes then things started going bad. I was treating it like my 130X. You need to take the time to rebuild your 250 completely. All vibrations must be gone. I tore mine completely down and replaced my main bearings and the tail grip bearings, as well as the bearings around the tail shaft. Replaced both tail drive gears for the TT.

Now this thing is flying so amazing right now. I am doing inverted nose down funnels both CW and CCW and the tail holds perfect.

These things are what I have learned about the 250 and will keep you flying. Be sure to check these every flying day:

*Motor pinion- make sure it is not slipping and is lined up perfectly with the main gear. Can cause vibrations if not aligned.

*Main gear- make sure it is just barely tight. There should be no up/down play on the main shaft. Use red loctite...don't want it backing out.

*Tail drive gears- replace every crash, hard landing, or tail tap. The black gears are prone to stripping off the shaft and causing no tail authority. Look for the plastic peeling off the top of the spindle like an apple peel. Dead sign that you need a new gear.

*No binding in the tail slider- the tail should be super smooth. Check with the tail control rod off the ball link. Majority of the time you get loctite in the brass bushings causing binding.

*TT- make sure it is dead straight. These can be very easy to bend. Roll it on a solid surface to make sure it is straight.

If you can follow these items, the little guy should hold up well for you. If you get any vibrations at these head speeds, bad things will happen. Any vibrations can lead to screws backing out, or the tail boom snapping in half during flight like I can attest to. I would get so frustrated because I wanted something dependable like my 500 and 600.

Good luck and let us know how it goes.

True, this thing is neither a scaled up mcpx nor a scaled down 600, it does need to be taken good care of. I made a carbon fiber push rod, using a mks ds95i instead of that stupid ds425m, running carbon fiber tail blades, scorpion motor, scorpion esc, and I was 100% sure that the tail was smooth like there was no friction, and the torque tube was dead straight and then I put up 4 brand new black tail drive gears with my pin-hole mod, I thought it was time to rock and roll, finally the torque tube snapped. You know, that's why I feel so screwed up. It was funny though as somehow I felt it was gonna happen.

[beer2morrow]

lasakro, I've just found this http://www.flying-hobby.com/shop/tre...ft-p-9625.html
carbon fiber torque tube, what do you think?

[A VIKING]

You guys that break TT shafts, I have yet to break one and saying that will probably have a failure today but what RPM do you fly at, 100% flat line or something less?
Also do you install the TT shaft support bearing in the correct spot in the boom, I know changes in it's position will change the natural vibration frequency of the turning shaft making it vibrate more or less depending on position.
Where are the TT shafts failing, at the end fittings or somewhere down the shaft.
Also do you pull the boom out slightly from the fully seated position as was discussed earlier.
Just trying to wrap my mind around these failures.
I like the carbon TT shaft idea but have questions of how straight they will be, seems the carbon tube manufactures sometimes create slightly bowed shafts, but in this case, being used as a high speed shaft they are probably dead on.

Viking

[Compusmurf]

Good gawds. After reading all this, I'm glad I'm belted and didn't convert it to TT like I intended to.

[lasakro]

Originally Posted by beer2morrow

Have a look at H25026B, do you think it's the same casing as the dfc pro? If so, we might just get the H25075 and put it into the tail case comes with the dfc pro kit, will it fit?

I think removing the bearing from the TT tail unit will not be as large as the opening of the belt tail unit. The rear side of the TT unit has bearing holder which you don't see in the belt unit photo. I asked the question over on RCG CopterX250 tread just to double check.

Originally Posted by beer2morrow

lasakro, I've just found this http://www.flying-hobby.com/shop/tre...ft-p-9625.html
carbon fiber torque tube, what do you think?

I can't tell from looking at the photo. I was looking for this 2 weeks ago and couldn't find one. Now it's to late, I'm not spending any more on TT parts for my 250.

Originally Posted by A VIKING

Also do you install the TT shaft support bearing in the correct spot in the boom, I know changes in it's position will change the natural vibration frequency of the turning shaft making it vibrate more or less depending on position.

With my electronics now at A+ I give my vibration an F. I've changed everything from the frame back. TT, Boom, TT tail unit, hub, grips and rotor shaft. New 42 mm tail blades weigh the same. Tried them snug and left them loose. Tried the 130X tape trick. TT bearing is perfectly centered in the boom. No axial play in the main shaft. Backed the boom out a couple of mm's that helped a little. Then Kickbackkid posted. Everything he stated was dead nuts correct except my main gear mesh was off. Put my new Scorpion 15T with set screw. It was a little better but still not right and wasted the rear white gears after giving it some rudder on the bench.

So I'm off replacing those gears now. The tail shaft does have about 2 mm of play in the end of it. The other TT tail unit does also. I'll putz around for this a little longer but the belt parts will be here next week. Giving up on the TT.

Originally Posted by Compusmurf

Good gawds. After reading all this, I'm glad I'm belted and didn't convert it to TT like I intended to.

+1

[A VIKING]

With my electronics now at A+ I give my vibration an F. I've changed everything from the frame back. TT, Boom, TT tail unit, hub, grips and rotor shaft. New 42 mm tail blades weigh the same. Tried them snug and left them loose. Tried the 130X tape trick. TT bearing is perfectly centered in the boom. No axial play in the main shaft. Backed the boom out a couple of mm's that helped a little. Then Kickbackkid posted. Everything he stated was dead nuts correct except my main gear mesh was off. Put my new Scorpion 15T with set screw. It was a little better but still not right and wasted the rear white gears after giving it some rudder on the bench.


As far as your TT shaft support bearing being perfectly centered in the boom, it should be 10-15mm forward of center to be positioned correctly. This is again to prevent harmonics from setting up in the TT shaft that could cause vibrations.
Not to say that in your case, this is the cause of your issues.
I think the belt will be a good change, I may drift that direction one day myself just to try something different on the 250.

Viking