Goblin clicking noise*Solved*

[SRJay]

On all the Goblins I've ever seen all the shaft holes are slightly oversize allowing slop where every bolt passes through. The only difference is the front tail pulley is the only thing not slotted allowing it to clamp. There have been numerous threads about slop on the head, main gear, secondary pinion and lower clamp. I use a T handle wrench on all those bolts and am able to get everything tight enough to achieve no play.

[ranchhand]

Does anyone know why the holes in these shafts are over sized? I've never seen this on any other helis I have owned.

[alexmit]

Originally Posted by Slyster

What is slotting?

The process of adding a slot to the gear. Also a cut. If you look at the main gear it has a vertical cut in the aluminum hub. I just called it a slot. Probably not very descriptive on my part. ;-)

[SRJay]

Slotting or slitting is the correct terminology. The head has it, main gear, and the secondary pinion has it. I used a 1/16" slotting saw in combination with my mill to slot the first gear I tried.

[Rotorexploder]

Thank you SRJay, very good info.

[DarkSyd3D]

i wish i would have seen this a few days earlier so i could have time to fix them before HFFF. Guess i have a bit of wrenching to do when i get back

[SRJay]

If you already have the required tap and drill it only takes about 10min to do the mod. Simply slide the tail pulley off (you shouldn't need to loosen the belt) disassemble the pulley, drill, tap, and reinstall.

[Slyster]

Perhaps someone could do a video? I don't get it.. and never used or own any taps etc.

[DarkSyd3D]

Originally Posted by SRJay

If you already have the required tap and drill it only takes about 10min to do the mod. Simply slide the tail pulley off (you shouldn't need to loosen the belt) disassemble the pulley, drill, tap, and reinstall.

not sure if i have that size tap. I bought a set a couple months ago, now i just have to remember where they are lol

[DarkSyd3D]

Originally Posted by Slyster

Perhaps someone could do a video? I don't get it.. and never used or own any taps etc.

try searchng on youtube. It may already be there. If not ill post one when i do it if someone else doesnt beat me to it

[DarkSyd3D]

Originally Posted by DarkSyd3D

try sea(***WARNING*** Stop Spamming Helifreak)g on youtube. It may already be there. If not ill post one when i do it if someone else doesnt beat me to it

UMMMMMM SPAMMING?!?!?! this is something new to me

[SRJay]

Ok, thought the picture said it all. I will go do a quick video to post.

[DarkSyd3D]

It did but some people are visual learners

[rando]

I've never used a tap either but there are several videos on the net showing the process that can be found. The abbreviated version is below.

1) Drill the appropriate sized pilot hole
2) Twist tap into hole until you feel it get tight
3) Back out the tap a half turn (this breaks off the bit of thread you just carved in step 2)
4) Repeat steps 2 and 3 until the tap threads all the way through.

[DarkSyd3D]

Careful using the Y word. I think that's what got me the spam warning

[rando]

Originally Posted by DarkSyd3D

Careful using the Y word. I think that's what got me the spam warning

Weird since folks link to videos on that site daily. The tag for doing so contains that very same word! In any case, I removed it just to avoid any sort of heavy handed action by the forum admins.

[P.I.Engineer]

Originally Posted by rando

I've never used a tap either but there are several videos on the net showing the process that can be found. The abbreviated version is below.

1) Drill the appropriate sized pilot hole
2) Twist tap into hole until you feel it get tight
3) Back out the tap a half turn (this breaks off the bit of thread you just carved in step 2)
4) Repeat steps 2 and 3 until the tap threads all the way through.

that's it, it's as easy as screwing a screw in.

use some oil, it'll help a lot

[SRJay]

At the request of Slyster here is a short video of how to do the mod.

Goblin Tail Pulley Mod. (5 min 15 sec)

[TT]

GREAT CATCH SRJay!

I'm getting ready to apply this fix to a Goblin 700 and two 500s. I've been getting a mysterious clicking noise during maneuvers requiring full tail throws...actually trying to get it to blow out. I thought it was belt slap or whatever. I removed the pulley bolt and it has been taking a beating...so bad that I think it would eventually fail.

My experiences with set screws against shafts lead me to believe that a flat spot on the shaft would be a requirement but I was worried about grinding one due the thin wall of the shaft as you had mentioned before. Then I came up with this: Run a 4mm tap through the pulley bolt hole and the shaft simultaneously on one side then use a M4x8 grub screw to secure the pulley to the shaft...then do the same to the other side. 3mm tap/screws may work but I'm guessing the holes in the pulley and shaft are too big already.

It certainly wouldn't move after that! No flat spot required, no extra holes, redundancy in case one of the grub screws somehow broke or backed out.

Thoughts?

[seefest]

I've owned 4 Goblins and have never had the clicking noise on any of them. Must be lucky I guess. After reading this thread I did check the three Goblins I still own and the tail drive pulley is tight on all three.