old cable style rotorheads

[Brent_Brown]

scorpion 133 helicopter with old cable style rotorheads anyone have photos of one? or have one?

I would like to see just what it would take to use one on a gyro.

[Al_Hammer]

Here's a photo, Brent.

[Brent_Brown]

Thanks Al.
do you think it is a good head for a gyro?

[Al_Hammer]

Brent, every word I've ever read about these things has been negative.

Supposedly they don't work to control the rotor unless its loaded. Then the cable stretches and the collective pulls in too much and you jump up 6 ft.

Not to mention the fact that it is very hard to find evidence of any Scorpion having actually achieved sustained flight.

One of our forum members has a photo of himself flying over Mesa Arizona in his Sccorpion. It looks to me like the collective is in the down position, compared to the photo of the same machine in a hover, but I could be wrong.
I hate to accuse anyone of faking a photo..
http://hoytstearns.com/Rotorway/N9066Falcon.jpg
Looks like it is taken from 8mm movie footage. Notice the dirt and hairs typical of a movie film. Then again, there are programs that will allow you to simulate such artifacts. This would be a fun one to have the digital photo experts look at.
If he's really "commuting" in a cable head Scorpion, god bless him.

[hstearnsjr]

Brent, every word I've ever read about these things has been negative.

Supposedly they don't work to control the rotor unless its loaded. Then the cable stretches and the collective pulls in too much and you jump up 6 ft.

Not to mention the fact that it is very hard to find evidence of any Scorpion having actually achieved sustained flight.

One of our forum members has a photo of himself flying over Mesa Arizona in his Sccorpion. It looks to me like the collective is in the down position, compared to the photo of the same machine in a hover, but I could be wrong.
I hate to accuse anyone of faking a photo..
http://hoytstearns.com/Rotorway/N9066Falcon.jpg
Looks like it is taken from 8mm movie footage. Notice the dirt and hairs typical of a movie film. Then again, there are programs that will allow you to simulate such artifacts. This would be a fun one to have the digital photo experts look at.
If he's really "commuting" in a cable head Scorpion, god bless him.

Hey, that's me! (the picture is a 35mm slide) I thought the rotor head was great, no problems at all and the easiest and most stable of any helicopters I've tried -- almost hands off. It is very clever to decouple the collective from the cyclic completely with the added advantage that the thrust bearings don't have to constantly cycle.

I had about 60 hours in it before I sold it. Probably many people have not been careful in building theirs.

Hoyt Stearns
http://HoytStearns.com

[Al_Hammer]

Hoyt,

you said in another post that BJ Schramm helped you build the Scorpion. Surely you are aware that BJ himself used to caution people not to fly the cable head. I believe I remember hearing him say that myself, but I can't swear to it.
I do know that BJ was pretty proud of the rotor and rotorhead on his last design- the Helicycle. It is said to be very smooth.
Here are some posts I just found on the net containing information about the cable head.
There are some problems with the old rotor
head. B.J Schramm, the designer should be contacted about those problems.
I believe I heard him tell one person not to fly the version with the looped
cable in the head. I used to fly a Benson gyro with a McCullough engine.
It was a quiet sewing machine compared to the sound of the Evinrude engine
in the Scorpion. Be very careful.
Stu Fields
====================
The bent cable is for the collective. Its a nutty way of doing
things, but it does work. Its just not as good as a regular system.
The only real problem with the bent cable rotor head is that it does
not use elastomeric bearings. It uses unsealed thrust bearings
instead. However, because of the way the cable head works, they only
move when you actually move the collective. I'll probably have to
spend a bit of time every few hours of operation greasing them, but a
friend showed me a trick where I can grease them easily with a
hypodermic needle. Hopefully that will make operating it more
manageable.
========

Take the cable-in-shaft control head for example. The entire rotor
head tilts on a U-Joint rather than cyclicly changining the pitch as
does a traditional helicopter. You might look at that and wonder why
BJ Shramm did it that way.

Here is the answer. At the time, the patent on elastomeric bearings
was still in effect. BJ could not use them. He elected to use
traditional thrust roller bearings. The problem with using these
bearings is that if they are under a load and are used cyclicly
(rocking back and forth with every revolution), the grease rolls out
of the way after a few minutes of operation and the bearings have to
operate without lubrication. This results in a failure.

To avoid this problem, BJ tilted the entire rotor head rather than
changing the pitch cyclicly. In fact, the pitch on the blades only
changes when the collective is moved and not the cyclic. This results
in the grease being retained for a longer period of time. It still
needs frequent regreasing, but at least you don't need a new set of
bearings after each hour of flight.

=============
The scorpion DOES have a
traditional swashplate. The linkages to and from it are a little
different, but that's all. It has only two control rods to it. There
is a pivot mechanism at the rear to hold it at a third point. It does
not slide up and down on the shaft. On the top side, there is only
one linkage which is connected to the hub itself and not the blades.
This linkage is what tilts the rotor head.

The collective is totally separate. It is a cable that runs from the
collective control, through the shaft, and out to a sissors joint on
the hub that changes the pitch on the blades. On this design, the
blades only change pitch when the collective is moved and not cyclicly
as in a regular helicopter.

So, with the Scorpion design, the swash plate is not used for the
collective control and is only used for the hub tilting mechanism.

There are other swash plate designs that use a pivoting rod inside the
rotor shaft that are not as reliable. The Mini-500 uses this
approach. Personally, I would not fly in a helicopter that had this
kind of swash plate mechanism as there is no way to inspect it to make
sure its still connected properly. Such a critical component needs to
be out where you can shake it.

[Al_Hammer]

So, to get back to your question, Brent--
I'm sure you've figured this out from reading the description, but to use the cable head on a gyro, it looks like you'd have to have the swashplate and the mast , plus all the cyclic and collective controls as well, unless you ran it at fixed pitch. I imagine you want the collective for jump takeoff?

[hstearnsjr]

Hoyt,

you said in another post that BJ Schramm helped you build the Scorpion. Surely you are aware that BJ himself used to caution people not to fly the cable head. I believe I remember hearing him say that myself, but I can't swear to it.
I do know that BJ was pretty proud of the rotor and rotorhead on his last design- the Helicycle. It is said to be very smooth.
Here are some posts I just found on the net containing information about the cable head.

Well, he never said that to me, and I knew him fairly well, we've flown together before, both of us with the cable collective head. Those comments must have come after that period (Scorpion 1). He did ask me to install a thicker cable once. I don't recall ever having to grease the thrust bearings. They were lubricated with pure STP. Since Rotorway is close to me, I did borrow some of his jigs and occasionally go to the plant for advise from him and his employees (Burt, Bob Everts, and Norman Bernier), and to refuel, but not often.
The biggest change was to upgrade to a 5/8" chain, which still got too hot.
(They should be using a cog belt now, as in the Mosquito).

There were many parts of the Scorpion design I didn't like, but the rotor head was not one of them.

One thing I've seen is that the cable slider at the bottom of the rotor shaft is in two slots at the bottom. Those shoud be machined carefully and have smooth edges. Some builders just tried to use a file! That's asking for trouble
(collective sticking).

BTW: I have photos of B.J., Norman and I flying in formation with cable rotorheads.

Hoyt Stearns

[Al_Hammer]

Thanks for the info, Hoyt. By all means, you should post those photos of you flying with BJ.

[Passin' Thru]

So, to get back to your question, Brent--
I'm sure you've figured this out from reading the description, but to use the cable head on a gyro, it looks like you'd have to have the swashplate and the mast , plus all the cyclic and collective controls as well, unless you ran it at fixed pitch. I imagine you want the collective for jump takeoff?
.

Hey Brent; I didn’t want to open this can-o-worms, but yes, you can adapt the cable head to a gyro for jump take off. More specifically, you can use the hub.
You can make an offset gimbal head to pass up in side it and not need a swash plate for cyclic control. The teeter towers on the head pass up between the teeter towers on the hub. I made a variation of Jerrie Barnett’s offset gimbal yoke which leaves a big opening up thru the center which provides clearance for the cable swivel and allows the housing to pass thru a big hollow spindle. I don’t know what kind of machining facilities or skills you have available, but be warned that considerable work is required. If you decide you are interested in pursuing this, I could share what I learned and perhaps avoid making some of the same mistakes.

Pete (perpetual tinkerer) Johnson

[Brent_Brown]

I think Mr. Hay used a head something like this to do his jump takeoff.
I am still looking for a two position system not a jump takeoff. Just to make spin up less work.

Thank for all the in put so far.

Pete I can get to the machining facilities and they have the skills. So if you have drawings or photos for what you have or had, I would be greatful if you would let me see them.

[Passin' Thru]

Brent, I'll see what I can dig up.

[Vance]

My experience with Morse cables suggests that the bend at the top is much too tight. Morse recommends a minimum 8-inch radius bend.

Thank you, Vance

[C. Beaty]

The A&S 18A was essentially a two position affair for jump takeoff.

Collective was detented against the no lift stop for prerotation and when the jump button was mashed, collective pitch snapped to about +9º for the jump.

The A&S 18A used about 45º of delta-3 coupling, so as the rotor slowed and coning angle increased, the delta-3 coupling automatically lowered the pitch. However, that much delta-3 coupling has undesirable side effects.

Bensen also used a 2 position collective scheme for his jumper. Collective was spring loaded to snap into flying pitch and for prerotation, the blades were manually cocked to zero lift pitch. A trigger tab projected through the prerotator ring gear that was fired by engaging a thing that bumped it.

With the usual low powered prerotators, 2 or 3 hp, collective pitch is an exercise in futility. If a prerotator will get the rotor to 180 rpm, zero lift pitch might get it to 200 rpm. Jump takeoff is impossible without 20 or so HP to the rotor of a light gyro.

[gyropilot]

With the usual low powered prerotators, 2 or 3 hp, collective pitch is an exercise in futility. If a prerotator will get the rotor to 180 rpm, zero lift pitch might get it to 200 rpm. Jump takeoff is impossible without 20 or so HP to the rotor of a light gyro.Chuck,

Weren't you also explaining to me once that there are some high cyclic stick forces involved when attempting to use a collective pitch control system (for jump takeoff) with the normal tilt style rotor head most of our gyroplanes use? Can you please refresh my memory on that subject?

Thanks,

John L.

[C. Beaty]

Yes, John. With a tilt head system, torque gets to the ground through the gimbal pivots. A component of torque ends up in the cyclic stick. Anyone with a strong prerotator will have noticed that the stick kicks sideways if abruptly engaged.

The old Kelletts and Pitcairns had rotorhead locks for prerotation.

[Brent_Brown]

Bensen also used a 2 position collective scheme for his jumper. Collective was spring loaded to snap into flying pitch and for prerotation, the blades were manually cocked to zero lift pitch. A trigger tab projected through the prerotator ring gear that was fired by engaging a thing that bumped it.

This Bensen scheme is more like what I want.

With the usual low powered prerotators, 2 or 3 hp, collective pitch is an exercise in futility. If a prerotator will get the rotor to 180 rpm, zero lift pitch might get it to 200 rpm. Jump takeoff is impossible without 20 or so HP to the rotor of a light gyro.[/QUOTE]

I was hoping to see morre than a 20 rrpm with zero lift pitch. I guessed if I get 200 now I might see 250 - 275 at ) pitch. So much for that idea.