Goblin Fireball makes ticking sound when running

[ventle]

I just noticed when flying my Goblin Fireball (1st gen, not Havok or Competition) it was making a ticking sound. Landing and pulling the battery, I was able to recreate the sound while hand-cranking the rotor. The "tick" occurs about once every second full rotation of the mainshaft.


Here's a video with the main and tail blades removed showing what I'm talking about:



Another video close to the right belt tensioner where the sound is even more audible:



Is this sound a notification of an impending belt failure? I took the tail apart, carefully inspecting the belt, pulleys and tensioners without finding any signs of wear or damage. The (plastic) tail boom has a few cracks near the end (where the tail shaft holder is bolted to it), but I cannot understand how that could translate into a sound that is synchronous to the main shaft rotations.


This is my first belt-driven heli, so I have no experience of what to expect I do not have a spare belt lying around to test swapping it right know (I have a few on order, anyways).

[ventle]

Seems that the Youtube-tag causes havoc to the forum formatting. Here's direct links to the two videos instead:

Goblin Fireball 280 belt ticking sound (0 min 31 sec)

SAB Goblin Fireball 280 belt ticking close up (0 min 26 sec)

[Heliwhisperer]

https://www.helifreak.com/showthread.php?t=789807

[JimJW]

Sound like it could be flashing on the tail drive gear. Or that it’s warped out of round. The original fireball uses a plastic gear that bolts to the motor, it’s been suggested that they can warp if tightened down too much.

Check for flash on the plastic and that it hasn’t warped. I didn’t like the plastic pulley so I replaced it with the Aluminum version. Lynx and SAB both made one...

[tonys-heli]

Just a side question.. how are you varying the throttle like that? A linear throttle curve?

[Steve.Favorite]

looks like the belt or motor has an issue, if you watch the front of the motor you can see the belt is not running true, for some reason.

[blarks]

Are you sure the belt is setup correctly? It looks skewed in the video.

[ventle]

Originally Posted by JimJW

Sound like it could be flashing on the tail drive gear. Or that it’s warped out of round. The original fireball uses a plastic gear that bolts to the motor, it’s been suggested that they can warp if tightened down too much.

Check for flash on the plastic and that it hasn’t warped. I didn’t like the plastic pulley so I replaced it with the Aluminum version. Lynx and SAB both made one...

You might be on to something. I do have the plastic main drive pulley, and by close inspection the "click" comes when the belt cams aren't properly engaged, but suddenly seats to the pulley about halfway through the rotation. I wasn't able to spot any blemishes to the pulley, but I guess they can be too tiny to see with the naked eye.


I've ordered an aluminum pulley along with some spare belts and we'll see how it works out.

[ventle]

Originally Posted by tonys-heli

Just a side question.. how are you varying the throttle like that? A linear throttle curve?

Yes, I was using a linear throttle curve for this testing. Always used flat curves for actual flying, though.

[tonys-heli]

Before you change it, just spray the belt where the teeth are with some silicone spray and see if it stops. I bet it does

I would use a gov.. either fbl or esc.

[blarks]

Have you made sure the belt is installed correctly? In the attached image the belt looks as if it is riding low on the side closest to us. It is also noticeable in the other video.

[ventle]

It does indeed ride lower on the left side, but I thought that was to be expected given that the right side leads to the top of the tail pulley and the left to the bottom? As far as I can tell it's installed according to the manual

[blarks]

Originally Posted by ventle

It does indeed ride lower on the left side, but I thought that was to be expected given that the right side leads to the top of the tail pulley and the left to the bottom? As far as I can tell it's installed according to the manual

All good, just looked a little more than what I remembered on mine. Mine is currently in pieces so I can't really check anything. Can you pinpoint where the clicking may be coming from?

[tonys-heli]

the clicking is from the belt teeth settling in the plastic grooves on the tail belt gear.. spray it with silicon.

[ventle]

I will try that, just got hold of some silicone lube. I have the aluminum pulley coming soon, too.

[tonys-heli]

ya might not need the pulley..