[SOLVED] E7SE and Tail - too tight and feels notchy?

[johncclayton]

Hi

I fitted the tail to the E7SE, in doing so I ensured that the tail boom is flush with the most forward boom block.  I've pinned in in this location.

When fitting the whole tail rotor assembly, I pushed the thing on as much as I could - this causes the rear torque tube gear to move outwards something like 1mm which in turn causes a pretty notchy rotation.

So I fixed it by moving the tail case back by about 3mm - which allows me to push the rear torque tube gear back towards the main gear just a fraction and thus things don't feel notchy any more.

Is this bad / good / ok?

Cheers
--
John Clayton

[Chris Sexton]

Make sure the gears are seated against the bearings in both the front transmission and rear tail box.  Also check to be sure the tt ends go into the gears smoothly and don't bind.

if the tt is pushing the gears out a bit then the boom might be in just a bit too far.

[curmudgeon]

The TT should be seated is such a way as to allow a little bit of axial play within the boom to prevent binding on the mushroom gears on either end.  After a little bit of experimenting on the E5's and E7SE, when the boom is 8mm longer than the TT, the TT sits flush (and somewhat tight) within the mushroom gears when the front boom end is flush with the front boom clamp and the rear end of the boom is inserted all the way into the tail case.  I cut the TT so that it is 10-11mm shorter than the boom.

My E7SE came with a 813mm long boom, so I cut the TT down to 802mm long.

The flat contact surface of the 320-502 TT end is 15mm long, so even with 2-3mm axial play there is plenty of contact surface between the TT end than the mushroom gears.

[johncclayton]

Ok, good to know - in my case I have pinned the tail case but didn't push it entirely onto the torque tube / boom as that causes the mushroom gears to bind.  As mentioned, there's about 3mm of distance I'm not using.

The tail case is secured with the clamp and pinned with one screw on the rear as well as two screws at the front.  This will also serve to extend the tail a little - which I've heard is needed if I plan on running 716 mains and 116 tails.

[steffgiguere]

If I were you I would check the TT front transmission surely you have a gear which is not fulling pushed against the bearing.

[johncclayton]

Ok, will do - definitely not a big deal to check.

[Rob Cherry]

Definitely not required to modify ANY stock parts to have a nice fit. Per the instructions there is still some moment in the TT. The models are designed in a way to allow very little, but still some movement back and forth.  Take out the TT and test fit the ends into the TT gears, they should be snug but not too tight.  If they don't seat fully, let me know and we'll get you straightened out.

Cutting the TT shorter than stock and having the boom located correctly could cause problems if the TT slides completely to one end, leaving the other end half (or even less) inserted into the gear.  At that point it can fail, it's happened.  - Rob

[johncclayton]

SOLVED - I checked the front transmission assembly, all good there meaning things we're meshed well and the gear appeared to be seated perfectly.  I re-assembled, this time making sure that the boom itself was moved backwards by approx 1-2mm and tadaaaa, no notchy feeling when all fully assembled.

It means I can't use the pinning I've made - but I carefully applied a reasonable amount of both thread lock and torque to the boom clamps, keeping in mind the manual specifically mentioned not to be a gorilla when doing these things up.

Thanks for the hints / tips - I very much appreciate it!  Now I can focus on cleaning up the wiring a bit more as I'm still waiting for the sizing tool + other bits to arrive in the mail.

Attached is a pic of the torque tube pushed into the front assembly, I noticed that it was quite stiff getting the tube in there so I sanded the front pins of the torque tube with 600 every so slightly.



--
John Clayton

[curmudgeon]

Glad you got the original problem solved.

I like how you are using nylock nuts to hold the TT ends to the TT instead of the regular nuts and Loctite like the manual states.  However, the stock M2x10mm screws are a bit too short to penetrate the nylock nut fully.  Consider using longer M2x12mm screws and reducing the excess with a Dremel of a regular file.

Difference in length between M2x10mm and M2x12mm screws.



Stock M2x10 screw is too short, and does not penetrate far into the lock nut.


Stock M2x10 screw is too short, and does not penetrate far into the lock nut.  This short screw makes minimal contact with the lock lock plastic, thus defeating the purpose of the lock nut.



The M2x12 screw is a tad long.  The excess will not bind against the boom, but may theoretically throw off rotational balance.



I reduced the excess length of the M2x12 screw in an effort to reduce rotational imbalance.  I used a Dremel grinding stone and finished it off with a file.

[johncclayton]

Damit, another good idea :-)  I noted this too .. at this rate I'll NEVER finish the build ... hahah... thanks again.

[curmudgeon]

LOL.      It also takes me a long time to build helis.  I've built several T-Rex's, Thunder Tiger's, Miniature Aircraft's, and SAB Goblin's.  My favorite helicopters are the Synergy's.  The only reason I fly a Goblin 380 is because Matt has not released a similar sized Synergy helicopter.  Except for the metal tail slider [200-411] for the E5, the Synergy helis don't need any upgrades.  The magnetic canopy mounts on the front make life easier, but the are not needed.

BTW, the E7SE and E5 have 7 screws that screw into metal that do not require Loctite and may make maintenance easier if you avoid Loctite:
1) M3x23mm socket head screws [100-323] that serves the dual purpose of holding the washout control arms [305-206] and clamp the head onto the main shaft.  There are 2 of those screws.
2) M3x8mm socket head screw [100-308] that clamps the tail box assembly onto the boom
3) M3x10mm socket head screws [100-310] that clamp the boom on the two main boom clamps.  There are 2 of those.
4) M2.5x10mm socket head screw that clamps the main shaft collar [610-150] unto the main shaft.  (Awesome design, much better than using shims)
5) M3x12 socket head screw [100-312] that clamps the boom support clamp [610-128] unto the boom.