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Item 0055

OTHER: Helicopter - Outside - Coaxial - Little Zipster - B-9 and B-8MH

Little Zipster - B-9

Picture:

It appears that yaw is controlled by brake bands

Outside Remarks:

B-9 Little Zipster 19?? = 1pOH; 60-70hp Mercury outboard motor; rotor: (upper) 22'0" (lower) 20'0" v: x/60/0 range: 100. Co-axial rotors. POP: 2 prototypes [N58U, x].

Engine: 1 x Mercury rated at 55kW, upper/lower rotor diameter: 6.70/6.10m, length: 3.50m, height: 2.60m, take-off weight: 318kg, empty weight: 204kg, max speed: 128km/h, cruising speed: 96km/h, service ceiling: 3350m, range: 160km

Hans said;

It had no autorotation

The gap between the rotors is only about 18"

It had delta-3 hinges. This may be intended to help in keeping the rotors apart. ?

It was copied by Air Scooter

Joe Bucci, jklbucci(@)att.net, 06.10.2008

I got the plans from Vortech Inc. poBox 511, Fallston, Md. 21047 USA.

the zipster, looks like airscooter did a modern knock off of it and called it revolutionary

A` friend of mine is a aircraft builder (one of the best) i think he said it is not real stable this friend of mine knew Bensen he was one of the first ones in P.R.A when they started it.

Bensen did say in his Little Zipster stuff that he did come up with a release mechinism that could allow autorotation with the Zipster it would just increase the price of the kit.

ON another thread someone posted a picture of Bensen's Little Zipster, a coaxial machine, I have the technical drawings and assembly manual for it. IT had B8 blades, teetering head and a D3 angle of 15 degrees. Pretty neat design so that as the one blade dipped the D3 angle helped correct the flight path so the one rotor system never came into contact with the other even though there are so close together.

B-9 Little Zipster This is a true helicopter with a contra-rotating rotor system driven by a 60 h.p. or 70 h.p. outboard motor. The rotor drive is through a differentia] which allows the upper 22ft rotor to revolve at a different speed from the lower 20ft one. The rotors are typically Bensen: rigid, with control by tilting the whole head from a hanging stick with a handlebar grip having a twist-grip throttle. This model is still in the development stage.

THE LITTLE ZIPSTER CO-AXIAL HELICOPTER, Construction Prints & Manual. From Vortec. Have 3 drawings and manual.

From Rotary Wing;

Bruno, the upper rotor is set at an autorotative fixed pitch (ex: 4 degrees aerodynamic), the lower rotor has an automatic variable pitch, the pitch is higher with rrpm...The gears incorporate a differential to accommodate the difference of RRPM of the two rotors. In case of the engine failure, the autorotation is enabled...I wonder of the problem of vibrations!?

Kevin, the "little zipster" alike helicopter in the Mentone museum is this one:

Observations by Self;

Yaw is by applying a friction braking to either of the two rotors. This means that the crossing locations of the blades will vary about the azimuths of rotation.
It appears that the cyclic control forces by the pilot would have been quite high.
It appears that the blades have a protrusion on their leading exges at about 75% of span.

B-8MH

Picture:

Outside Remarks:

Demonstrated in public for the first time in 1976, this is described as a 'Hovering Gyro-Copter'. It is powered by a 70-110hp modified water-cooled outboard engine driving the lower of the two rotors; the upper rotor autorotates. One 14 hp modified air-cooled go-kart engine drives the pusher propeller mounted at rear.

This machine was a coaxial helicopter with both upper and lower rotors driven through a diffentral gear.

by Dennis Fetters;

The rotor hubs would automatically pitch depending on power, and the small prop on the back was only to blow across the rudder for yaw control, nothing more.

It was only an experimental concept machine, never really flew but a few times, ended up being way too complicated, and Bensen abandoned the concept.

by quadrirotor;

Bruno, the upper rotor is set at an autorotative fixe pitch (ex: 4 degrees aerodynamic), the lower rotor has an automatic variable pitch, the pitch is higher with rrpm...The gears incorporate a differential to accommodate the difference of RRPM of the two rotors. In case of the engine failure, the autorotation is enabled...I wonder of the problem of vibrations!?

By C. Beaty;

The rotors were driven through a differential gearset, ensuring that each rotor was supplied with equal torque even though their speed ratio wasn’t constant.

This made tilt head cyclic control possible.

The blades of the variable pitch rotor were retained by twisted cable loops, incidence responding to centrifugal force. Mechanical links tied the blades together, keeping them in track.

I’ve seen Dr. Bensen fly this thing and it looked like a handful.

Hovering height control by engine throttle isn’t easy.

Last Revised: May 20, 2013