Prop-end bearing for the Razorback project

rtfm

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Hi,
As some of you are aware, I am building a steel tube pusher gyro, which departs quite significantly from more traditional designs, without in itself, breaking much new ground. It is really one interpretation of some of the newer design ideas which have been floated on this forum.

I began working on a tractor design, but for a number of reasons elected to side-step from that partially designed project, and complete this one first.

I have dubbed the design the RTFM "Razorback". It will feature variable pitch control, wings and an hydraulically controlled "minimum rotor speed" power.

The bulk of the design work is now complete, and the project is finally taking shape (albeit only in the Proof-of-Concept) stage. I have braised the mild steel tubing of the main airframe, together with the tail section together, and so far, so good. One of the first things I noticed in the P-frame stage was that the moment arm of the tail is quite long, and this seems to place excessive strain on the top "rafter".

I have decided that I need to support my tail boom in the same way that Dick DeGraw does on GyRhino (http://www.youngeagles.org/photos/gallery/Helicopters_-_Rotorcraft/DeGrawGyrhino.jpg)

Does anyone know what this sort of bearing might be called? It's a bit difficult trying to source something and not knowing what to ask for.

Kind regards,
Duncan
PS This is a sketch of the Razorback.
 

Ga6riel

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yes I find that very interesting too
heres a pic for those of you slightly puzzled
What Duncan is describing is the attachment joining the propshaft to the struts connecting the tail empenage
 

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Bob

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Duncon :
I would sujest the same berring you use on the rotor head.
sense its strong enough to hold the rotor on it will be more than adiquite to support the tail section.
a plate to mount it in the center of rotation of the prop and
a locking mechnisum to inner turning part of the berring that will be stationary with the tail section.
this should prove strong enough in any condition, but it would be important to check the ware on the berring from time to time,
because if the berring seezed up it could rip the tail section off.... so just incase of a berring seezure on the prop center line a sheer pin on the tube supporting the tail might be a good idea ...
My 2 coppers
Bob.......
 

Jazzenjohn

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I think I'd look at dual tapered rolled bearings. There could be a very high axial shock load at landing and I'd think ball bearings would tend to brinnell. JMO
 

rtfm

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Hi,
Thanks for the suggestions. My gut feeling is that it shouldn't be necessary for reinforce the tail by linking it to the end of the prop.

After all, most traditional gyros have a piddly 2x2 Ali tube sticking out the back supporting the tail and absorbing the landing forces via the tail wheel quite successfully. All the Razorback is doing is inverting the picture, and using triangulated tubular steel instead of Aluminum tube. It is significantly stronger, without being much heavier. Perhaps the impression of requiring extra strength is purely psychological. If we had to invert the traditional Ali tube arrangement of the Dominator or Sparrowhawk and dangle it downwards, it, too, might look as though it required additional reinforcing.

Dunno. Still thinking on this one. I'll complete the concept welding, and measure the deflection under static stress. Then I'll have some facts to work with.

The second issue of adding an additional brace up to the mast has merit, but completely destroys the flexibility of the mast. The mast itself is a circular 4130 tube, able to flex throughout the 360 deg range. This will significantly help alleviate stick shake, especially since the tube is mounted on rubber mounts. The brace will undo this, making the mast rigid. But its all a matter of trade-off. This might well be worth further consideration.

Thank again, guys.

Regards,
Duncan
 

Ga6riel

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many thanks Al
for a while there, I thought it may have been a solid shaft with the prop on bearings around it. Allowances would have to be made for thrust surfaces and for detachment of the prop.
I hit on that idea when considering building into the drive a reduction system, for it wouldnt have been as complex a job as all that, just a little unique. And it would provide the opportunity for generous shaft support....which gyrhino has too.
 
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