Item 0926

DESIGN: UniCopter ~ Power Train - Assembly - Horizontal Crank - w/ V-belt

Drive is intended for Hirth F-30. It might work with Rotax 912 if gearbox can be removed and other related changes made.

Drawing:

 Components and their Arraignment:

  1. Engine: - Hirth F-30 mounted with horizontal crankshaft.
  2. Torsional Shock Absorber: Inside driver sheave.
  3. Primary Reduction: 3V with 4 belts to each side.
  4. Soft-start: Large wheel against backside of T-2 side of v-belts.
  5. Overrunning clutch: Located in driven sheaves.
  6. Rotor Synchronization: Timing chain between the secondary reduction pinions.
  7. Secondary Reductions: Two conventional 90-degree, 4:1 ratio, spiral bevel gears.

    8. Advantages:

    Simplicity of drive mechanism.

    Smooth flow of fuselage

    Horizontal engine

    Ease of incorporating overrunning clutch and soft start.

    Headroom for tall pilot.

    Disadvantage:

    Timing chain and end bearings are far aft and this could make for a large, heavy frame.

    Consider:

    Fixing the engine's location and using a pulley on the T-2 side of the belts for soft start. The bell adjustment could be handled by shims in the engine mounts thereby leaving the 'belt tensioner' for soft-start only. Guides can be used on the backside of the belts, to help keep them away from the driver pulley when not engaged. The use of these guides also minimizes the amount of wrap around the 'belt tensioner' when engaged. Why was this not done on the Helicycle? Some belts are not designed for a backward bend.

    The larger the diameter of the soft-start pulley then the more wrap on the driver and driven pulleys, larger radius for the 'back-bend' on the belt and more belt take-up is acheived for less movement of the soft-start pulley.

     Notes re the Use of the Rotax 912:

    If the driver pulley has a large enough diameter (which it will have since the engines gearbox has reduction) part of it may fit over the gearbox housing and thereby keep the engines center of gravity reasonably forward.

    A problem with this is that the Rotax reduction combined with the 4:1 reduction is too much.

     Notes:

    The synchronizer connection does not transmit power it only assures that the rotors are synchronized.

    It must have a very high safety factor. Will chain be robust enough?

    Make sure that there cannot be 'surging' between two rotors or two V-belt drives.

    Make sure that the large sheaves will clear the rotor hubs.

    Consider linking the rotors' pinion gear shafts with a chain.

    Consider, also, two idler gears that have fixed stops and movement.

    Options to be considered regarding the idler(s);

    1. No movement during operation. Are only used to set chain's tension.
    2. Movement during operation, with spring tension.
    3. Movement during operation, with dampening.
    4. Movement during operation, with both spring tension and dampening

Consider soft-start to be two idler wheels pressing against back of v-belts.

Consider locating the overrunning clutches in the driven sheaves.

 Notes re Primary Reduction (V-belt):

It looks like the large sheave can be around 9.5" diameter. The ratio will be around 1.4:4. This means that that the small sheave will be around 6.8" diameter. This is bigger than the Helicycle's 5" diameter drive sheave and therefor the transmitted horsepower per belt will be greater.

The diameters have been reduced to 8" and 4.37 and the ratio has been increased to 1.83. (see 0889.html) This will probably change again, hopefully for the better

Option:

The drawing has a view showing 2 small sheaves. A sprocket on the engine will drive one sheave and that sheave will drive the other.

Advantages:

Disadvantages:

 Center of Gravity of Engine:

 

X = -19.5"

Z = 14.6

Y =

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Last Revised: August 13, 2001