General Torque Tube Gear/Front Drive Gear Mesh Troubles

Derek

Derek

Well-Known Member
A few weeks ago, I replaced the stock white gears on the front drive assembly, on my Trex 600 Pro DFC, and the torque tube because I had stripped out a few teeth on the front drive assembly. I installed new black gears where I could. The manual says that the tail drive gear is 34 tooth, so I bought a 34 tooth replacement.

The weather was spectacular today so I went out to fly a few packs. After a few minutes, I noticed an odd sound. Set the helicopter down and unplug everything and I find that the torque tube umbrella gear is missing 3 teeth and the front drive gear is missing 3 teeth. This has to be a "gear mesh" issue. Perhaps I have the mesh too tight and its stripping teeth or perhaps I don't have the gear mesh tight enough and it's stripping teeth. How do I know if I have the gear mesh set properly? I really don't want to have to replace these gears every 3-4 flights because I'm constantly stripping gears, lol.
 
Tony

Tony

Staff member
Just like the main gear to the pinion, you want them as tight as possible but still with some play. Make sure everything moves smoothly and there is no binding, and that the tail is not hitting the ground or rocks/grass when it's spinning. Also, be careful of the tail when loading and unloading. The head is locked in position so it's easy to strip the gears. And seeing as there were 3 on the front, and 3 on the back, that tells me that it was more than likely damage caused while in the vehicle.
 
Derek

Derek

Well-Known Member
OK, I just pulled the bad parts from the 600. There are 2 teeth missing from the torque tube umbrella gear. Those two are side by side. There are 2 teeth missing from the umbrella gear on the front drive gear. Those two are almost on opposite sides of the gear.

While taking the tail apart, I quickly realized that I can't really adjust the mesh (tighter or looser) because everything fits into it's own place. It's simply "pull the bad parts, install the new parts". While putting new gears into place, I did check the mesh and it seems snug but not tight and the two gears spin with no resistance. They don't spin "freely" (like a large washer on a small bolt) but everything does spin nicely.

I suppose I can go to the local hobby shop tomorrow and see if they have a new torque tube. I doubt it though. The guy that works there flies only SAB, so naturally there are tons of SAB parts and very little Align parts. I may just have to put the 600 back on the shelf for a few days and order a torque tube from HeliDirect.

Tony, I completely understand what you are saying but I think it's unlikely that I damaged it while putting the helicopter into the truck and taking it out of the truck. Now, "unlikely" is not "impossible" so I will definitely try to make an extra effort to be sure to take the helicopter out of the truck carefully and keep an eye on the tail.

I've had no hard landings "yet". In fact, I've gotten comfy with doing some "baby autos" from about 5-6 feet and gently setting the helicopter down. It's just amazing, to me, how there is still that much lift as the head is winding down.

So...I appreciate the replies guys! I always do! I'll see if I can get another torque tube soon and replace it "just in case" and I'll check the gears after each flight. I sure do hope I can get rid of this "tooth stripping" ordeal, lol.
 
Graham Lawrie

Graham Lawrie

Well-Known Member
As you did not hit anything? and just heard a strange noise? my money is on the torque tube:)

I have had ground strikes with blades and seen axial mirroring on the gears(my terminology for stripping gears in identical plane). I have also recently fitted new torque tubes and they have had bends on them. Not sure what the tolerance permissible as the tube rotates and flexes. But when you think all that is keeping it in a straight line from front to rear is your torque tube bearing:)
 
Derek

Derek

Well-Known Member
Yes, I am sure that I did not hit anything nor did I have any hard landings. But, a new torque tube is rather inexpensive so I'll see if I can hunt one down today.

Thanks for your replies, Graham!!!
 
wolfman76

wolfman76

Well-Known Member
spin it in your hand before reinstalling the boom i notice on mine you can adjust it somewhat by either pushing the umbrella gears on the front or rear tighter or pull them off a very slight amount to tighten the mesh i found this out cuz my mesh was too tight when i spun the shaft so i had to push the umbrella gear on ever so slightly tighter
 
P

pvolcko

Well-Known Member
I was having this happen on my 550x main gear. Mesh was too loose. The umbrella gear should have some small amount of play available by controlling how far you seat the gear into the block bearings.
 
Derek

Derek

Well-Known Member
I've gotten a lot of people, on Youtube, telling me to not let the tail blades touch the ground when landing. I am 100% sure that my 600 landings are the softest of all my helicopters, so I am certain that my landings aren't causing this damage.

Tony suggested that the damage could be happening when I remove the helicopter from my truck or when I put it in the truck. Perhaps I'm tapping the tail on something, while the head is stationary because the blades are in the blade holder. Although I find that unlikely, because I know that I'm careful, I can see it as possible.

One of my Youtube buddies sussgested the same thing that you said, Paul. I can see this as a potential cause for the stripped gears. When I replaced the gears last time, I pressed the umbrella gear as far into the bearing casing because that's how it was before. Perhaps, being that far in, there is actually a bit too much slop in the mesh between the two umbrella gears. Its too late in the day for me to tear it down and check the gears now but I will surely do it tomorrow before I go flying....as long as the rain stays away.

Thank you, everyone that has commented! I'm still learning lol.
 
Lee

Lee

Well-Known Member
The demo of these black gears, had them chopping through a block of wood until the tail blades were little stumps.
They still didn't break.
I can't see how these things are suppose to break, from cutting a few blades of grass, being lifted out of a truck, or having slightly too much play.
Unless the demo ones were made of high strength unobtainium, and then they made the real ones out of cheese???
Very strange???
 
wolfman76

wolfman76

Well-Known Member
my guess if the stripped that easy then maybe the umbrella gears were pushed down too far on the shaft creating too much slop well enough to break the teeth off like it did only thing i caan think of
 
Derek

Derek

Well-Known Member
I dunno, Kyle. I really don't know. But...I'm gonna take it apart this evening and see what can be adjusted and we'll go from there.
 
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