I tried to do Alwayscrash’s tail gear mod:
http://www.rcgroups.com/forums/showp...postcount=1697
but ended up breaking my drill bit due to off center hole, bummer.

So I put on my thinking cap and came up with two possible fixes for the weak breaking tail shaft gears on the 4G6/4#6. The first fix which I’ve actually tried but haven’t crashed yet demonstrates that the tail still works well after this mod with no extra parts. I did manually try to turn the tail rotor with the main gear held stationary and it released the excess pressure and still works with no damage after doing this several times.

I used a spare tail shaft and a medium sized tail gear that fits on the tail shaft. Place the tail shaft gear on the shaft in the normal position then using a small nut driver that fits on the backside of the gear. Then hold the nut driver in place with the tail shaft vertical on a firm surface and give the nut driver a tap with a tool, not too hard just enough to drive the gear past the stop on the shaft. This will slightly enlarge the D shaped hole in the gear. The key is to get it to the point that it still indexes and holds the shaft but will release to excess pressure from rotation. Put the gear on the shaft in the normal position and it will maintain the shaft position with the original collar in place and seems to hold the tail assembly without slippage in normal operation.

I figure since most folks with 4X6s will have plenty of those mid-size gears because the small one at the main gear always strips in a mishap. So you have nothing to loose trying this mod. If you do try it please report back here how it works out for you. I’m a little chicken to stick something into the rotating tail blades just to test it out.

My second idea was to drill a hole in the mid-sized tail gear face just above the D shaped hole flat spot. This may create a spring like effect that would allow the shaft to rotate past the flat with excessive force from a blade strike. I haven’t tested this because the first approach seems to work and is way easier to do.

Edit: Three flights so far without problems...no tail stoppages though.

Good Luck, Don

Originally Posted by dbennettya

I tried to do Alwayscrash’s tail gear mod:
http://www.rcgroups.com/forums/showp...postcount=1697
but ended up breaking my drill bit due to off center hole, bummer.

So I put on my thinking cap and came up with two possible fixes for the weak breaking tail shaft gears on the 4G6/4#6. The first fix which I’ve actually tried but haven’t crashed yet demonstrates that the tail still works well after this mod with no extra parts. I did manually try to turn the tail rotor with the main gear held stationary and it released the excess pressure and still works with no damage after doing this several times.

I used a spare tail shaft and a medium sized tail gear that fits on the tail shaft. Place the tail shaft gear on the shaft in the normal position then using a small nut driver that fits on the backside of the gear. Then hold the nut driver in place with the tail shaft vertical on a firm surface and give the nut driver a tap with a tool, not too hard just enough to drive the gear past the stop on the shaft. This will slightly enlarge the D shaped hole in the gear. The key is to get it to the point that it still indexes and holds the shaft but will release to excess pressure from rotation. Put the gear on the shaft in the normal position and it will maintain the shaft position with the original collar in place and seems to hold the tail assembly without slippage in normal operation.

I figure since most folks with 4X6s will have plenty of those mid-size gears because the small one at the main gear always strips in a mishap. So you have nothing to loose trying this mod. If you do try it please report back here how it works out for you. I’m a little chicken to stick something into the rotating tail blades just to test it out.

My second idea was to drill a hole in the mid-sized tail gear face just above the D shaped hole flat spot. This may create a spring like effect that would allow the shaft to rotate past the flat with excessive force from a blade strike. I haven’t tested this because the first approach seems to work and is way easier to do.

Good Luck, Don

If it was the D hole on the gear that was holding the tail shaft from sliding out to the left. Once you do this what is holding the shaft from sliding?

The plastic compresses when the shaft is driven through and springs back enough to hold the shaft in position and key the gear to the shaft. I actually had to rotate the gear on the shaft several times to get it just right (able to spin on the shaft with excess force but still maintain proper position and function.

Don

Originally Posted by livonia bob

If it was the D hole on the gear that was holding the tail shaft from sliding out to the left. Once you do this what is holding the shaft from sliding?

Originally Posted by dbennettya

The plastic compresses when the shaft is driven through and springs back enough to hold the shaft in position and key the gear to the shaft. I actually had to rotate the gear on the shaft several times to get it just right (able to spin on the shaft with excess force but still maintain proper position and function.

Don

Get some flight time on this and get back with us..

Originally Posted by dbennettya

The plastic compresses when the shaft is driven through and springs back enough to hold the shaft in position and key the gear to the shaft. I actually had to rotate the gear on the shaft several times to get it just right (able to spin on the shaft with excess force but still maintain proper position and function.

Don

Your Mod may work when hovering or FFF but i wonder how it handle when turn...For making tiny pin hole, first drill a start point just about a bit deeper onto shaft then use a smaller drillbit to go through, this way you'll not break it.After that, use the first drillbit to finish it (better by hand by turning slowly for haft turn each time until the end).Always drill with slow rpm and don't let beaver stay in drill hole.

So far I have six flights with lots of turning at various speeds and directions, very solid performance. Also had one crash due to choppy wind pushing me into the ground. All links popped off the swash, the tail blades where facing down into the grass after the crash. Checked it out and flew it with no damage from the crash, so far I'm stoked

Don

Originally Posted by Alwayscrash

Your Mod may work when hovering or FFF but i wonder how it handle when turn...For making tiny pin hole, first drill a start point just about a bit deeper onto shaft then use a smaller drillbit to go through, this way you'll not break it.After that, use the first drillbit to finish it (better by hand by turning slowly for haft turn each time until the end).Always drill with slow rpm and don't let beaver stay in drill hole.

Good stuff db!

I did this 2 days ago now as I am on my last tail gear and I wanted to try something to save it..

I just forced the tail rotor shaft to turn in the gear to round out the D-hole. I turned it a few times till I felt like it was 'good'.

So far I have had the tail kick/pulse a time or two, but the HH gyro of the 4#6 took care of it without messing up my flight.

I have crashed like 5 times since and I know the tail got stuck on at least one of them...the one the tail blades got caught up in my lace curtains, and no damage to the small main to tail gear!

This much better than stripping the little gear, IMO.

And if you get the medium size tail rotor gear 'wrong' (too loose), you know you have a ton of them left over from all the "tail gear transmission kits" you've gone through to try another one...

Thanks for sharing db,
Jay

Jay, Thanks for posting. So far I've had another 8 flights with no issues but no crashes either. I think I'm more relaxed not worrying about the tail I did set it down in the grass once without incident

On my second 4G6 I tried your method and it seems to work about the same but doesn't require any tools. Just put the gear on a spare shaft and give it a few twists until it can index and slip around the shaft with a little extra force. So far I haven't noticed any downside to this mod.

Don

Originally Posted by GITech

Good stuff db!

I did this 2 days ago now as I am on my last tail gear and I wanted to try something to save it..

I just forced the tail rotor shaft to turn in the gear to round out the D-hole. I turned it a few times till I felt like it was 'good'.

So far I have had the tail kick/pulse a time or two, but the HH gyro of the 4#6 took care of it without messing up my flight.

I have crashed like 5 times since and I know the tail got stuck on at least one of them...the one the tail blades got caught up in my lace curtains, and no damage to the small main to tail gear!

This much better than stripping the little gear, IMO.

And if you get the medium size tail rotor gear 'wrong' (too loose), you know you have a ton of them left over from all the "tail gear transmission kits" you've gone through to try another one...

Thanks for sharing db,
Jay

Hi all,

Just did a real world test got too close to myself with the heli and over reacted. Sent it backwards at a good clip into a concrete patio Here is the permanent damage:
lost 2 links from flybar to swash
damaged one blade tip (repaired)
damaged one blade tip and root (trashed)

The tail gear fix worked awesome I just had to re-index the modded gear, replace the links and fix and balance main blades. Checked the pitch and adjusted the links. Now it even flys better than before with less vibs on spin up

Don

Originally Posted by dbennettya

Hi all,

Just did a real world test got too close to myself with the heli and over reacted. Sent it backwards at a good clip into a concrete patio Here is the permanent damage:
lost 2 links from flybar to swash
damaged one blade tip (repaired)
damaged one blade tip and root (trashed)

The tail gear fix worked awesome I just had to re-index the modded gear, replace the links and fix and balance main blades. Checked the pitch and adjusted the links. Now it even flys better than before with less vibs on spin up

Don

dbennettya, Congratus!
Your mod for the saving tail gear is simple and great!
I tried your mod, and tried crashing from the tail blade several times by intention, and it accomplished the work of the clutch splendidly. This mod seems to become practical use enough.
However, the shaft dives by the crash since the stopper of the shaft is weak.
Fortunately, since the tail of my 4G6 was assembled right and left and oppositely, there was play on the Counterclockwise side, and the sleeve was able to be installed. As a result, the shaft never dives.

Thanks

Some ideas are posted here http://www.rcgroups.com/forums/showp...postcount=1787

Originally Posted by Peter_SVK

Some ideas are posted here http://www.rcgroups.com/forums/showp...postcount=1787

Hi Peter_SVK,
To how many mm have you expanded the hole diameter of the tail gear? It must be not too loose. I think that your MOD also uses caught of D cutting part of the shaft.

I tried your MOD. However, I gave it up because the screw could not be cut short.

Originally Posted by Tipstar

Hi Peter_SVK,
To how many mm have you expanded the hole diameter of the tail gear? It must be not too loose. I think that your MOD also uses caught of D cutting part of the shaft. ...

Hi Tipstar,
original 1.0mm hole is over drilled to 1.5mm. D-shape part of the shaft have no effect on the clutch, tail gear is also over drilled to 1.5mm, so it can slip on the shaft (slip clutch). Slightly compressed O-rings (3x1mm size) between tail gear and the collar transfer the torque to the shaft. Rate of O-rings compression determines clutch treshold from transferring the torque to slipping. Brass collar also prevents the shaft from moving to the left in case of hitting the tail.

Originally Posted by Tipstar

...
I tried your MOD. However, I gave it up because the screw could not be cut short.

It can. I recommend to choose such screw, that has the thread as close to the head as possible. I fixed the screw in the vice by head and ground it down to ca. 1 mm by dremel (by small amounts, always check the correct length in the collar - I haven't measured the final length). That's the trick.

Peter

Originally Posted by Peter_SVK

Hi Tipstar,
original 1.0mm hole is over drilled to 1.5mm. D-shape part of the shaft have no effect on the clutch, tail gear is also over drilled to 1.5mm, so it can slip on the shaft (slip clutch). Slightly compressed O-rings (3x1mm size) between tail gear and the collar transfer the torque to the shaft. Rate of O-rings compression determines clutch treshold from transferring the torque to slipping. Brass collar also prevents the shaft from moving to the left in case of hitting the tail.

It can. I recommend to choose such screw, that has the thread as close to the head as possible. I fixed the screw in the vice by head and ground it down to ca. 1 mm by dremel (by small amounts, always check the correct length in the collar - I haven't measured the final length). That's the trick.

Peter

Hi Peter, Thank you for advice.
Can you approve this as the second machine equipped with a perfect clutch?

Installation test with 4G6FP:
Landing in the wrinkle of the sheet is alive of the clutch. The tolerance of the frictional force is considerably wide feeling.
The supplementation:
I am using Rotor Head Dampener of 4G6 instead of O-ring.
Edit:To make the head of the screw low, I make the surface of the shaft which stops the inner sleeve flat.

Hi Tifster,
I'm pleased to see you did it finally! Just few notes: Rotor head damper seems to be quite large diameter, check that it doesn't touch drive shaft gear. To prevent right bushing (next to the tail rotor) from popping out inside, put a small piece of tube (or O-rings) between the collar and the bushing.

Peter