Rotorhead Question

[MaD Dog]

I am building a rotorhead for a helicopter. It is a two-blade semi-rigid teetering head, pretty standard stuff. Adams-Wilson or Scorpion type with elliptical hub, bearing blocks, and blade attachment straps. I have the grain of the metal (6061 T6) in the hub running spanwise. My question is, in reference to the bearing blocks, do I have to pay attention to the grain direction, and if so, which way should the grain run? The blocks are approximately 2 in. by 3 in. by 3 in. The 3 in. direction is from side to side with the 2 in. dimension running spanwise. The securing bolts are 7/16 in. and are drilled across the 3 in. direction. How much does the grain matter in a piece that is pretty much a square with nearly equal dimensions?
Thanks, MDD

[C. Beaty]

I’m not sure which bearing blocks you’re talking about, Mike; the pillow blocks that contain the teeter bearings or the thrust blocks that contain the feathering bearings.

But it makes no difference; the loads on both are primarily in compression so grain is irrelevant.

[Al_Hammer]

Looks something like this?
There was a Scorpion for sale on ebay a while ago and I saved this photo.

[C. Beaty]

That’s an old one, Al

The first ones applied collective via a Morse control cable running through the mast. It looped up in the shape of an inverted “U” and if it started whipping, produced a ride described as being like a Model A Ford on a washboard road.

The one you posted above must be a mod 2 version with a rigid push-pull rod running through the center of the mast for collective. But the kinematics looks to be incorrect from what I can see of it; i.e., isolation between cyclic flap/pitch and collective.

But on closer inspection, there is probably another pushrod balljoint on the teeter bolt centerline hidden from view.

[Al_Hammer]

Thanks Chuck. I don't have another view of that rotorhead.

Here's the old cable head and then a picture of BJ's more recent work- the Helicycle rotorhead.

[C. Beaty]

You amaze me Al. A virtual rotating wing Library of Congress. All, you claim, on a P1 with W95 and a 4 G HD. Do you store all this stuff on floppies? If so, must amount to a cubic yard of them.

BJ’s last was certainly cleaner, more elegant and impossible for a guy with only a file and hacksaw to duplicate.

I still prefer UltraSport’s configuration using a music wire torsion pack instead off ball bearings however.

[Al_Hammer]

Chuck, my HD is only 2 gigs. It all fits because I only save a few items in each category.
Speaking of Library of Congress, I wish Norm would make available the old forum database soon. It contains about 5 yrs worth of your posts, most of which did NOT fit on my HD, so they're lost to eternity unless we put the heat on Norm.
LArry G. has a copy, but he seems to have gone bye bye from this forum.

The Helicycle rotorhead is relatively vibration free. Elastomerics in the feathering axis help, no doubt.
Under load it only takes a few lbs of force to move the pitch horns. BJ liked to include that demo on the construction videos.

[C. Beaty]

Goes to show you I don’t know what I’m talking about. I had assumed the Rotorcycle used a ball bearing stack just from the looks of the grips.

OTH, from looks alone, one would never know the Ultrasport uses a music wire torsion pack.

Feathering bearings without balls or rollers is the way to go.

Individual blade feathering, omitting the Young rocking hinge is also the way to go.

Computers: In the larger sizes, HDs go for less than $1/Gig. Means you have a $2 HD.

[KenSandyEggo]

What's the status on the builders? Is someone carryinhg on for B.J., or is everyone on their own now as to completing their projects?

[Al_Hammer]

Test test test

[KenSandyEggo]

Good luck, Al. Hope it all goes smoothly until completion.

[Al_Hammer]

Originally Posted by KenSandyEggo

Good luck, Al. Hope it all goes smoothly until completion.

Wow, thanks Ken.


Chuck, you called the Helicycle a Rotorcycle.

For those that might be curious, photos of Hiller's Rotorcycle.
Powered by a 45 hp Nelson engine(with electric start) and weighing 290 lbs, these helicopters were so stable, pilots got only 8 hrs of instruction. The Rotocycle used flying "paddles" to stabilize the rotor.

[C. Beaty]

Sorry about that Al.

But while on the subject, have you ever seen the film clips of a Hiller prototype hovering with sandbags in the seat and 2 people standing alongside?

It’s a trick though; the trick being to load up the paddle blades with enough lead so it won’t respond to anything.

[C. Beaty]

That RC model isn’t purely Hiller, Al. Notice there’s also a differential cyclic input that makes it partly Bell.

[Al_Hammer]

Another example of a "Hiller" system, this time on an R/C helicopter.
Notice how the controls for the paddles are 90 degrees from the controls for the rotor.