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Telumehtar · 08-21-2009, 04:01 AM

Having learnt to hover on a coaxial, I bought a kit from eHirobo containing a 4G3 and a 4#3. Ten minutes playing with the 4G3, spinning it up on the floor and thinking I'd better fit some training gear, I picked it up and the rotor head came loose in my hand, detached from the main shaft.

Searching the floor I found a small metal pin. But this pin seems too slender to do the job: it comes loose and falls out very easily. Now I'm wondering if I just found some random piece of metal on my floor (I also found two screws that don't fit).

Could someone describe what the pin holding the head to the shaft should be like? I'd imagine it should fit tightly at least. I have the metal head, but I'm thinking I might buy the plastic head in the hope that the pin from that is the same. But from photos it looks different. Or maybe I could just improvise something -- suggestions welcome!

Thanks,
Rob.

Steve Joblin · 08-21-2009, 07:35 AM

The metal pin is just shy of 5.5mm in lenght, and should be just shy of 1.0mm think. If you examine it very carefully, you will see one end has a slight 45 degree taper around the edge to help with installing it. You put this chamferred edge in first.

There is nothing "magical" about the pin. Any small metal rod with the right dimensions will work just fine.

The pin should fit in rather tightly and you should need a bit of force to remove it. You don't want it coming loose in mid-flight. On larger helis (and real helicopters) it is called the "Jesus bolt". The name comes from Pilots saying that if the bolt falls off in mid flight, you find Jesus real fast!

Telumehtar · 08-21-2009, 08:13 AM

Thanks, Steve. I'll have another look at it when I get home but it does sound like either it came with the wrong thing (which would explain why it fell off in the first place) or I've lost the right thing. I will improvise something, and hope it doesn't give me cause to need Jesus.

Telumehtar · 08-21-2009, 01:18 PM

Hm, this is discouraging. The pin I have is exactly the dimensions you describe, but still fits loosely in the hole. Is it possible the metal head has a different sized pin?

Everything I have tried to improvise so far has fallen out pretty quickly. I don't want to resort to glue...

SQRT(-2) · 08-21-2009, 01:31 PM

A small bolt and nut?

A small cotter pin?

Locktite on the pin?

Dusty1000 · 08-21-2009, 02:08 PM

bent paper clip?
you could bend it into an 'S' shape

Dusty

Telumehtar · 08-21-2009, 02:57 PM

Hm, I suppose it isn't that critical that there's no slop -- the torque should hold it tight. Maybe the bent paper clip will work! But a small bolt and nut would really do it, seems so obvious now.

Thanks,
Rob.

Steve Joblin · 08-21-2009, 04:23 PM

Depending on handy you are, you could take a 1.5 mm drill bit and create a long taper over an inch or so to create a "wedge" that will insert easy, but then get snug as you continue to insert it.

Telumehtar · 08-24-2009, 03:11 AM

It turns out the paper clip idea worked better than I imagined. The tolerances on these helis aren't as critical as I thought they'd be.

rhsmd · 05-03-2010, 09:20 PM

I lost mine. now i use a cut paper clip. then i secure it with a dab if crazy glue.
works fine

08-21-2009, 04:01 AM	#1 (permalink)
Telumehtar Join Date: Aug 2009	Rotor head pin with metal head Having learnt to hover on a coaxial, I bought a kit from eHirobo containing a 4G3 and a 4#3. Ten minutes playing with the 4G3, spinning it up on the floor and thinking I'd better fit some training gear, I picked it up and the rotor head came loose in my hand, detached from the main shaft. Searching the floor I found a small metal pin. But this pin seems too slender to do the job: it comes loose and falls out very easily. Now I'm wondering if I just found some random piece of metal on my floor (I also found two screws that don't fit). Could someone describe what the pin holding the head to the shaft should be like? I'd imagine it should fit tightly at least. I have the metal head, but I'm thinking I might buy the plastic head in the hope that the pin from that is the same. But from photos it looks different. Or maybe I could just improvise something -- suggestions welcome! Thanks, Rob.

08-21-2009, 01:31 PM	#5 (permalink)
SQRT(-2) Registered Users Join Date: Jan 2009	A small bolt and nut? A small cotter pin? Locktite on the pin? __________________ Gaui Hurricane w/ 530mm blades & Robird G31 Walkera Super CP Walkera Devo 10 w/ Deviation

08-21-2009, 02:08 PM	#6 (permalink)
Dusty1000 Registered Users Join Date: Sep 2008	bent paper clip? you could bend it into an 'S' shape Dusty __________________ Blade 400, mSR, mCPX - Sonix SX450SE - Walkera 1#A, 4#3, 4#3A, 4#3B, 4G3

05-03-2010, 09:20 PM	#10 (permalink)
rhsmd Registered Users My HF Map location Join Date: Aug 2008	I lost mine. now i use a cut paper clip. then i secure it with a dab if crazy glue. works fine __________________ If you want to avoid a crash, stay away from the ground! IRCHA # 1261, Blade 400 (hopped up), T-rex 450 se V2, Blade cMX, Blade mSR, T-rex 250 se, Blade mCPx, Blade 130 X, Blade 300 X, Blade 450 3D, Blade nCPx, Parrot AR Drone, Blade 230S

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08-21-2009, 07:35 AM	#2 (permalink)
Steve Joblin Registered Users My HF Map location Join Date: Aug 2008	The metal pin is just shy of 5.5mm in lenght, and should be just shy of 1.0mm think. If you examine it very carefully, you will see one end has a slight 45 degree taper around the edge to help with installing it. You put this chamferred edge in first. There is nothing "magical" about the pin. Any small metal rod with the right dimensions will work just fine. The pin should fit in rather tightly and you should need a bit of force to remove it. You don't want it coming loose in mid-flight. On larger helis (and real helicopters) it is called the "Jesus bolt". The name comes from Pilots saying that if the bolt falls off in mid flight, you find Jesus real fast!

08-21-2009, 08:13 AM	#3 (permalink)
Telumehtar Thread Starter Join Date: Aug 2009	Thanks, Steve. I'll have another look at it when I get home but it does sound like either it came with the wrong thing (which would explain why it fell off in the first place) or I've lost the right thing. I will improvise something, and hope it doesn't give me cause to need Jesus.

08-21-2009, 01:18 PM	#4 (permalink)
Telumehtar Thread Starter Join Date: Aug 2009	Hm, this is discouraging. The pin I have is exactly the dimensions you describe, but still fits loosely in the hole. Is it possible the metal head has a different sized pin? Everything I have tried to improvise so far has fallen out pretty quickly. I don't want to resort to glue...

08-21-2009, 02:57 PM	#7 (permalink)
Telumehtar Thread Starter Join Date: Aug 2009	Hm, I suppose it isn't that critical that there's no slop -- the torque should hold it tight. Maybe the bent paper clip will work! But a small bolt and nut would really do it, seems so obvious now. Thanks, Rob.

08-21-2009, 04:23 PM	#8 (permalink)
Steve Joblin Registered Users My HF Map location Join Date: Aug 2008	Depending on handy you are, you could take a 1.5 mm drill bit and create a long taper over an inch or so to create a "wedge" that will insert easy, but then get snug as you continue to insert it.

08-24-2009, 03:11 AM	#9 (permalink)
Telumehtar Thread Starter Join Date: Aug 2009	It turns out the paper clip idea worked better than I imagined. The tolerances on these helis aren't as critical as I thought they'd be.

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