TT Initiative - The Buzzkill Clutch

[Gr4yb3ard]

This is like the engineering version of "LOST" or something similar...

Hokay, last time our heros met, we discussed a clutch for the 200 TT.

<Disclaimer>
This is a thought-experiment. I don't have a TT version to play with *yet*. I don't have one to look at, I don't know you, and could care less why your heli crashed. Send your lawyers elswhere, I'm toasted on heli-crack and broke....

1. Attached is a .bmp of the design.

2. The scale is scary, to be sure, but I have come up with two setup jig designs to ensure precision, if you want to go for this, let me know, I will provide the jig designs (uses scrap wood). The entire mod requires just 4 holes drilled with a decent drillpress to make it work. Tools required: Drillpress, small bits, straight edge, ruler, CA. Parts required: suitably sized ball bearings, springs, scrap wood. Time required: 4hrs, plus time spent bashing head against wall....

3. I have allowed for a second hole to be drilled, a second set of ball bearings and spring to be installed, to allow for experimentation, tuning, and cope with the fact that there may not be enough hold with a single set. Again, everything depends on the darned spring... Also note that I have included a retaining collar to be epoxied to the torque tube, as I've not seen the tube, I don't know if there is a shoulder on it to enforce the gear mesh.

4. The plan is contingent on careful drilling work, carefull selection of bits, and the selection of the right spring. If anyone does this, and finds that spring, please buy a bag full and share!!

5. This just might work. I know, I've said that before, but I'm still alive....

Gr4yb3ard
"...guns ready Captain!.. ...argh, put her to the wind mate..."

[Buzzkill]

Not sure I know how it works but the name is awesome! :lolol

[Gr4yb3ard]

Well, Buzz,

It was your idea. I scoffed at first, but after analysis a clutch makes sense.
Not a clutch in the traditional sense, but a torque-release mechanism.

The ball bearings ride in the channel, providing the link between the gear and the torque tube to power the tail rotor.

On impact, the forces push the ball bearings back into their little burrows, and the gear spins until things get back to normal.

The trick is to have enough force on the balls to keep them in the channel under normal use.

I'm gonna hafta get a tt upgrade now, just to do this, a joyous little project!

GAUI, if you're listening, if it works, this is worth a boatload of spare sales and a fantastic write-up in the trades. Patent Pending, but I'll settle for about three-dozen new model TT 200's for me and my budds.

Gr4yb3ard
"...I dona like the look 'a this cap... ...Hold fast gunney, it's just another putrid website..."

[rotorhead58d]

wow, that might just work. i swear we should start our own company. all it takes is money.

RULE #1 100% american made parts.

[Buzzkill]

Very good idea Gr4y and Rotor. Would be awesome on a larger heli.

[rotorhead58d]

anybody notice the full moon tonight?

[Buzzkill]

Well that explains a lot :banana

[small.planes]

What diameter are these bits? Im belt drive on my (3) 200's.
Its a relatively trivial drilling job compared to some Ive had to do recently...:arggg:
Hows the gear held on now?

Would a shear pin work in this? Ive got some 0.8mm dia alloy wire that might do the job, that is an even easier fix, drill 1 hole and put pin in :thumbup:

Dave

[Gr4yb3ard]

SmallPlanes,

Again, this was a thought experiment, I've yet to even see a real torque tube, so I can't help you on the diameters.

At a guess I'd say no more than 1/4 the diameter of the tube itself.
Again, the spring is a major issue, it would have to be pretty small and stout.

Also, one more detail, very important...

It's quite likely that the torque tube is hollow. If so, the end of the shaft would have to be plugged some small distance from the end and filled with epoxy, otherwise the spring may work it's way sideways.

Your thoughts on a wire pin are great. I was thinking along these lines too. Maybe a small piece of fishing line, copper wire, or steel. With these in hand, you could tune the breaking point of the shear pin quite a bit.

Gr4yb3ard
"...better living through modest insanity..."

[Buzzkill]

The tube is about 1/8" I'll measure with the calipers tonight.

[small.planes]

some photos of the bits would help to, Ive no idea what the TT loks like in the flesh, and the Gaui pictures dont help :arggg:

Dave

[rotorhead58d]

larry, do you remember the govt skillcraft pens? how about that spring?:confused:

[Gr4yb3ard]

Hmm,

I think that would be to big, we're talking one mike-mike or less here...
I've seen some little ones, they make 'em, I'm sure. The trick is to find a convenient place to scavenge them or a supply house source.

maybe brushholders for small electric motors??

Gr4yb3ard

[Jetleaf]

I think the small size of this stuff will preclude any type of clutch, and a shear pin I have my doubts. The shaft is a solid rod 3mm diameter. It appears to be some sort of plastic carbon composit. The bevel gear is pressed on one end of the shaft with no set screw. There does not appear to be any spline, keyway, or any other such locating mechanism, it may be glued. The driven end where the crown gear resides has a flat for the set screw. There is a bearing midway down the boom which is secured in place by two pinch points or crimps that appear to have been applied from the exterior of the boom. These pinch point are on the underside of the boom and spaced 4mm apart, on either side of where the bearing is inside the boom. It looks like somebody took a center punch and placed two punch points on the boom.

[Jetleaf]

Also the sd boom is 10mm longer than the belt boom. Both booms are the same OD. The sd boom is .45mm wall thickness and the belt boom is .28mm

[kahn10]

how bout this......http://www.helifreak.com/attachment.php?attachmentid=52241&stc=1&d=1214047689

[small.planes]

That wont work on a solid drive shaft without hollowing out the end. if that is possible (actually it is, but the simplicity of it is questionable) then it would work.
Not having one in the flesh make it harder to figure out the solution...

anyone got a bust one they want to send me? As long as I can see how it works and can measure it it'll do.
Its possible that we could replace the shaft with a larger tube that still fits into the outer and then have a circular spring round the outside holding the balls into the gear IYSWIM.
That would be *relatively* simple to make.

Dave

[kahn10]

http://www.helifreak.com/attachment.php?attachmentid=52254&stc=1&d=1214055378

sorry forgot to draw a bit.......

[mrivers]

How about some, ahem, silicone fuel tubing :) Or, fill the hole with silicone adhesive, and set the BBs in the silicone - once cured, the BBs wont fall out, and maybe there's enough give in the cured silicone to act springy.