Sportcopter Rotorhead on a GyroBee?

[Brian Jackson]

Hello.
Has anyone ever used a SportCopter rotorhead on a non-SC machine? I've read such wonderful things about the SC head design (http://www.sportcopter.com/pages/partslist.htm) that I was curious if it was able to be used on a GyroBee. The photo in the link above shows cheek plates already installed, but these will undoubtedly be replaced if used on another machine due to hang-test differences, etc.

Thanks,
Brian Jackson

[Doug Riley]

Replaceable soft bumpers in a rotor head at the control stops and teeter stops are a nice feature. They'll reduce metal-to-metal wear.

OTOH, you have to wonder how well the rubber bushings really can isolate the the airframe from vibration. "Isolation" of vibes is an involved science. A rubber bushing is simply a non-metallic spring. The spring can spread out the sudden accelerations associated with vibes and shock loads over time, thus reducing their suddenness. How effective this "spreading-out" will be depends on the stiffness of the spring material and the available travel distance in the spring mechanism.* Perhaps one's expectations shouldn't be too high in the case of a relatively small rotor head bushing that's already compressed by the weight load of the gyro. The system may help, however, and certainly the reduction in wear is worth something.

* A dramatic example of the need for travel distance is the Monarch/Carter vertical-descent landing gear. A short video of this gadget in action has been posted here in the past. To allow a reduction in acceleration sufficient to permit gyro landings right from vertical descent, the gear looks as if it compresses by more than a FOOT -- maybe even two feet.

[PW_Plack]

Brian,

The Sport Copter single-place machines use redundant 1-x-2 aluminum masts, so it shouldn't be too complicated, unless some revisions to the controls are required. Call Jim Vanek at (503) 543-7000 some weekday. If there are any special tricks required, he'll know.

[GyroRon]

I don't see why it wouldn't work, but it sure is a expensive piece to use on a in expensive gyro like a gyrobee.....

[Brian Jackson]

I don't see why it wouldn't work, but it sure is a expensive piece to use on a in expensive gyro like a gyrobee.....
This is true! :eek: I'd have more $$$ wrapped up in the SC head as I would the whole airframe. However, if the head is really as good as they and others claim, I might bite the bullet and go for it. As far as coupling it with such an inexpensive gyro, even if money was no object, I believe I'd still choose the GyroBee as my first build.

I suppose the next obvious question is... how "interchangeable" are heads, hub bars & blades? I'm pretty much sold on Ernie's DWs, but I know very little about mounting compatibilities between heads, etc. I don't know if Jim Vanek would be too keen on answering a lot of questions about a competitor's blades as they relate to his SC head.

...and the learning process progresses :) ...

Thanks,
Brian Jackson

[GyroRon]

If you want the Best Rotorhead on the market then a Double bearing heavy duty rotorhead with Slider from Ernie at RFD is the hot ticket. Price should be less than the sportcopter head or at least in the same ballpark and it offers a true slider to take away the shakes.

[Brian Jackson]

If you want the Best Rotorhead on the market then a Double bearing heavy duty rotorhead with Slider from Ernie at RFD is the hot ticket. Price should be less than the sportcopter head or at least in the same ballpark and it offers a true slider to take away the shakes.
I'll definitely check Ernie's rotorhead out. Hopefully, with his DW blades, I'll still squeak in under part 103 weight.

Thanks,
Brian Jackson

[Doug Riley]

Don't use a double-bearing head on a light machine. It adds needless weight and tends to increase the control pressures. I'd use any one of the Bensen-clone 1-bearing heads, such as Starbee's Black Beauty, Brock, Air Command or RFD/Dominator.

Head designs are semi-standard, at least among the 1-bearing heads designed for light gyros. The offset of the longitudinal pivot from the rotor axis is typically 1", they usually use a 5206 ball bearing, a 1" square torque bar, a half-inch rotor axle bolt and 3/8" bolts as pivots and teeter bolt.

The undersling of the blades is one area where mixing brands can get tricky. The old standard was 2.5" height from the top surface of the teeter stop plate to the center of the teeter bolt. Most blade makers can supply a teeter block that fits such a head, and this, in turn, usually gives you about the right undersling to keep 2/rev to a minimum.

[GyroRon]

Well sure Doug a double bearing head is overkill on a single place machine, but I was only saying what the BEST is. Other than extra weight, that extra bearing can't be looked at as a negative otherwise... I single bearing head with slider from RFD would be my pick if I had the extra money to Splurge. But I doubt I would have the extra money so in that case I would just use a plain jane single bearing head from whoever has one for sale at a good price.

[Brian Jackson]

Ron (or anyone),
What exactly is a "slider" and how does it function? Am I to assume Earnie's single bearing head lacks one? Obviously I have much to learn about rotorheads, hence all the questions. Thanks.

Regards,
Brian Jackson

[ultracruiser41]

I used a Joe Souza head on my Bee and it is fine. Price was reasonable too if I remember correctly. But you are right, the Sport Copter head is the nicest looking...I know their rotor blades are good, heads should be too !


Barry

[Brian Jackson]

Thanks Barry.
Fortunately I have a few months to go before it's time to worry about a rotorhead. So during that time I'd like to ask some (hopefully) intelligent questions and learn all I can about them.

Brian Jackson

[Chuck Roberg]

To Rotopix. Slider head from old conference. Hope this helps.................



Date: December 24, 2001 10:51 AM
Author: Dave DeWinter (dave@thumpernator.com)
Subject: Ernie's slider
Paul said, "Ernie has done it with his slider head, which to me is closer to the source, but induces wear and tear on the roll bolt."
Paul, There isn't a "roll bolt" to wear.
(NOTE: See correction post. It is a hardened tool steel pin running in a teflon impregnated kevlar bushing!)
Dave DeWinter, Thumpernator, Lovejoy, Ga.

Date: December 24, 2001 12:14 PM
Author: Dave DeWinter (dave@thumpernator.com)
Subject: Correction
It is a hardened tool steel pin running in a teflon impregnated kevlar bushing!
Dave DeWinter, Thumpernator, Lovejoy, Ga.

CA BEATY (cabeaty@worldnet.att.net)
Subject: Slider
The slider is an interesting gadget, Ron.
It isn't so much isolation as detuning. The actual motion, judging from the polished area on mine, is only about plus/minus*1/16". On my gyro with fully triangulated rotor pylon, the 2/rev was unbearable. The version you saw at Mentone (I've forgotten the year, early 90s perhaps.) had drag hinges and door hinge type teeter pivots but wasn't much better than a normal underslung rotor. It's hard to believe all that hammering could be eliminated with only 1/16" of travel but it was.
The leaf springs ought to be arranged to give non-linear resistance -soft on center and stiffer as travel increases. You might use a softer spring with a curved backing plate so the spring is in effect shortened as displacement increases.
*Originally that was a plus/minus sign with the plus sign on top of the minus sign but I'm told the MS browser changes it to a one. I didn't mean nor type 11/16".

CA BEATY (cabeaty@worldnet.att.net)
Subject: Slider
Yeah, Ron, there isn't much new under the Sun. Cierva and a handful of really bright people made possible modern rotorcraft flight. Even then they were considered aviation's lunatic fringe.
I had originally tried to use rubber springs on the first slider but it didn't work as well as I had hoped. Thought the rubber was squeezing down around the roll pivot bolt and locking it up so made up hollow rubber cylinders that had no contact except at the ends. Didn't work very well either.
Lloyd Poston was standing around asking dumb questions but taking it all in. He suggested that I use coil springs. Didn't think much of that idea but to humor him tried coil springs and like magic, the 2/rev was gone.
One of my early sliders slid too far and completely locked up the rotor head in pitch. I had to mush in for a landing just using throttle.


Subject: Black plates...
Dave,
what are the black plates on the front and back of the head? Are those the springs?

Mike Gaspard
Kaplan, La.
Bensen B8MG, NX36MG


Date: December 31, 2001 09:48 PM
Author: Dave DeWinter (dave@thumpernator.com)
Subject: Yes
Those are the springs to keep the slider from bottoming out.
Ken J, What?
Dave DeWinter, Thumpernator, Lovejoy, Ga.

[Doug Riley]

Ron Awad, Rotopix and others: there is an additional disadvantage to double-bearing heads that I alluded to earlier. The "centering" force created by the gimbal head results from the undersling of the pitch and roll pivots relative to the teeter bolt. The thrust of the rotor opposing the weight of the gyro (as long as you have positive G) tends to make the head assembly and airframe orient themselves along the rotor thrust line. This provides centering forces to the stick. The taller the head, the more leverage the rotor has on the head and the stronger the centering forces (imagine trying to move the stick if the teeter bolt were, say, six feet above the head pivots.).

You may or may not like the higher stick forces; most people enjoy a light stick on a sport aircraft. Two-place gyros with tilt heads tend to drive like dump trucks with no power steering... partly for this reason and partly because the rotor thrust force itself is greater in order to oppose the greater weight.

[GyroRon]

Never really considered that Doug. I knew that using tall teeter towers can make for a heavy stick, but never thought about how a double bearing rotorhead would do the same. Thanks for making me think

[Aussie_Paul]

Hey Doug, I thought that the torque tubes were 1 1/4" square. I thought my Bensen, Air Command and Rafs were all 1 1/4". I had better check!!!! maybe I am incorrect!!!! (never wrong!!!). :eek:

Aussie Paul.:)

[Doug Riley]

No, Paul, you're right. 1-1/4" square.