Torque tube drive gear mesh

[mikejr718]

I just installed the torque tube upgrade in my synergy e7. The drive gear mesh with the smaller gear that drives the crown gear was very tight when I assembled things. I thought s few flights would wear it in and it would fit ok. The main shaft was noticeably harder to turn and did not spin freely any more. It did disengage from the main gear just fine. After flying a couple of flights it felt different in the air.  Checked vbar logs and they are full of vibration warnings. Did a test hover and it is full of high vibration warnings. Spooling it up on the bench without main blades shows vibrations around main shaft speed but not at a consistent rpm, spikes move around continuously. I noticed the top of the torque tube drive gear has develop a lip of melted gear material on the top of the gear. I checked and made sure the boom was slightly pulled back into the rear mounting clamp so as not to compress the tube.  I really think I need to slot the frames where the rear torque tube crown gear block mounts to loosen up the gear mesh. I have read this is not recommended but see no other solution.  Has anyone else had to deal with this?

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[stevehof]

At least one person has filed the frame holes for the TT transmission. It was common on some of the kits for that mesh to be tight but most 'wore' in OK. If you choose to enlarge the frame holes for the TT transmission, I think you will also have to file the holes for the front boom clamp too. Or, face it of a few thousands of an inch so you can actually move the transmission to the rear. On all of my E7s the TT transmission butts against the front boom clamp. You will need to enlarge the screw holes VERY slightly. The photo of your gear absolutely shows the results of a very tight gear mesh.

[mikejr718]

The transmission for the torque tube on my e7 does not sit flush with the front boom clamp, there is a small gap there. If I unbolt the trans I can slide it back slightly and it will fit flush. Is the gap I have on mine not normal?

[stevehof]

If you can slide the transmission back, do so and see if that fixes the tight gear mesh. If it's not enough then plan B with elongating the TT mount holes and the boom clamp holes too. I don't know if a gap or no gap is 'normal'. Just do what you need to do to get a decent gear mesh.

[mikejr718]

I will elongate the torque tube transmission mounting holes first. The front boom mount is secured to a carbon plate that is attached to the rear boom mount, elongating the front boom mount holes alone will not allow it to move. The rear boom mount is close to the edge of the frame, dont want to move those holes back. I will work on it tonite.

[Anthony Oxlade]

I know matt recommends not elongating the TT transmission holes but i also did this in order to relieve the extremely tight spur gear mesh. I was very careful to remove only a small amount of material and i then set the mesh to have minimal backlash. I did not need to modify the boom clamp holes as my transmission does not interfere with the boom clamps.

[mikejr718]

I feel I have to do something as it appears that the torque tube drive gear is distorting or melting under the stress of the overly tight mesh , as seen by the lip of material forming on the top of the gear.

[mikejr718]

Was able to spend some time with it this afternoon. I slotted the transmission mount holes and put things back together. I was not able to get the gear mesh much looser, still had vibe problems in vbar log on the bench. Looking closer at things I noticed that the rear of the transmission actually fits inside the front tail boom mount. With the tail boom loosened up as I move the transmission back away from the maingear the rear of the transmission will push the boom backward. I left the boom loose and set the gear mesh on the torque tube just tight enough so there was no slop. Then I made sure that the boom did not contact the transmission(pushed the boom all the way forward then pulled it back a little bit.  Spooled it up on the bench and vibes all gone!!!!!!  I took out the transmission mount screws to see how far back it had moved, it was not moved much at all(see picture).

I think if I had removed or slid the boom back out of the way while putting the transmission in I could have avoided a lot of this.



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[stevehof]

Oops, I and I guess everyone else failed mention the boom position being a possible issue. I figured when you said you had a gap that the boom was out of reach of the Transmission. In any case, it looks to me like the transmission is now back at least 6 to 10 thousands of an inch. That can make a huge difference in gear mesh. Glad to hear you got it sorted out...

[mikejr718]

When I was putting it together initially I thought that the instructions said to slide the boom back flush with the front boom mount. In this position it interferes with the transmission.

[cyprusflyer]

Into my new build now and did not like a high/tight spot on the TT drive, the mesh was a bit tight.
Did a combination of 2 things to solve it, was tempted to file the mounting holes a little but really should be a last resort!
I have not put any Locktite on any of the frame bolts yet, wanted to see a nice free shaft etc, so I loosened off all the bolts securing the 3 aluminium bearing blocks. Then pulling everything forward, I nipped up the bolts again.
I did the same for the TT drive assy but pulled the opposite way.
I could not discern movement but must have been enough play to loosen the mesh a bit, now the tight spot has gone and shaft is freer.

[Chris Sexton]

Into my new build now and did not like a high/tight spot on the TT drive, the mesh was a bit tight.
Did a combination of 2 things to solve it, was tempted to file the mounting holes a little but really should be a last resort!
I have not put any Locktite on any of the frame bolts yet, wanted to see a nice free shaft etc, so I loosened off all the bolts securing the 3 aluminium bearing blocks. Then pulling everything forward, I nipped up the bolts again.
I did the same for the TT drive assy but pulled the opposite way.
I could not discern movement but must have been enough play to loosen the mesh a bit, now the tight spot has gone and shaft is freer.

I can see that. Bolt thickness tolerances giving way to small movement.

[stevehof]

Just double check that the mast turns freely and is still easy to push into and pull out of all three bearings. I noticed in the manual that the bottom bearing block for the mast uses slotted holes in the frame so you can insure proper alignment. So, it seems it might be possible to get some minor misalignment in the three bearing blocks while trying to gain better gear clearance on the TT drive.

[cyprusflyer]

Thanks for the advice, yes bearings are free and inline so satisfied all criteria. Will start locktiting all the frame screws one by one now.