DESIGN: SynchroLite ~ Power Train - Overrunning Clutch

Outside Helicopters

Groen Gyrocopter

Rather than an overrunning clutch, engagement to the rotor shaft is by a pawl (sawtooth dog clutch), pulled in by a solenoid.


Sprag: Transmits power from outer-race to inner-race. They are intended for high-speed operations. If they were to be used they would have to be locate between engine and primary reduction.

Sprag clutches wear out very quickly when there is no shock absorption device between them and the reciprocating engine. [~ from D.K] Particularly reciprocating engines with few power pulses per revolution. Do not use.

Cam: The shaft should be the overrunning member, which is perfect.

Roller & Ramp: Preferable to have the outer-race as the overrunning member. They operate at slower rpm's than sprag clutches.

Ratchet: Its advantage is precise and consistent rotational positioning.


Locate between the large sheave and the input shaft on the secondary reduction.

Torque at location of clutch:

The torque at the overrunning clutch will be 186 ft-lb at 1818 rpm:

Reference;- Ratios, HP, Torque & Losses:

Sprag Clutch:


Cam Clutch:

Morse series B2+ and Marland-RINGSPANN R 200 series seen to be the same.

A light 200 series bearing must be added with both.

Torque Values:



Morse Cam




175 lb-ft

195 lb-ft



275 lb-ft

325 lb-ft

Calculations re: Selection of Morse Overrunning Clutch (page C25)

1/ 186 ft-lb

2/ Overrunning

3/ Gradually applied 1.25 ~to~ 1.75

Note the use of a reciprocating engine and possible misalignment may take the factor up above 1.25. The fact that there is a belt in the drive train plus the inertia of the sheaves and gears etc. may minimize this factor increase.

4/ 186 * 1.25 = 232 ft-lb ~to~ 186 * 1.75 = 325 ft-lb

5/ Bore requirement is between 1.1875" and 1.5748" (40mm).

6/ Overrunning speed is 1818 * 1.20 = 2182 RPM. Inner member is the overrunning one.

Item 0260 is 275 ft-lb. The associated bearing is taking very little load so use Ultra Light Series bearing.

Calculations re: Selection of Marland-RingSpann

Marland-RINGSPANN R 206 [Item 0524] is 195 ft-lb. 1.289" bore 2.440" OD

Requires bearing. The 206K bearing weighs 0.43 lbs.

Questions; -

What is min. and max. speed




Design & Engineering specs.

Note:- The 207 is 57% stronger (325 ft-lb) than the 206 but it, the bearing, the spacer and the larger housing OD will increase the weight by exactly 1 lb.

Warner - Sprag and Roller/Ramp Clutch:

Calculations re: Selection of Warner Overrunning Clutch (Cat P-956 8/98, page 12)

Will accept up to 0.025" of misalignment. Where did this come from?

namax = 1818 * 1.2 = 2182 RPM Maximum outer-race drive speed. OK

nimin = 1818 * 1.2 = 2182 RPM RPM Minimum inner-race overrunning speed. OK

1/ Torque to be transmitted:

223 ft-lb

 2a/ Reduced load cycle rate: I donn't know where this came from.

10^5 / (1818 rpm * 60 min.) = 0.92 hours

1000 hours will be: 1000 *1818 * 60 = 109,080,000 load cycles

The load factor fK is there fore ????

= 223 * ???? = zxc

2/ Service factor: of 1.75, for Gasoline engine and light steady load (low starting torque)

3/ Design torque:

zxc * 1.75 = xxx lb.-ft. Reduction for load cycle.

223 * 1.75 = 390 lb.-ft. No reduction for load cycle.

4/ Shaft size: Between 1.1875" and 1.5748" (40mm).; which is less than the bore of all for clutches.

5/ Overrunning speed: 1818 rpm * 1.2 = 2182 rpm. (Inner race)

6/ Selection:

The following torque capacities look low. Why?


Torque capacity:




168 lb.-ft.


0.86 lb.


196 lb.-ft.


0.97 lb.


210 lb.-ft.


1.08 lb.


280 lb.-ft.


1.46 lb.


295 lb.-ft.


1.10 lb.


xxx lb.-ft.


1.79 lb.

Ratchet Clutch:

This will probably not be used.


The ASK 60 (Item 0567) appears to be the better one of the Warner clutches, by far. Handle the small axial loads with a pair of simple Oilite thrust washers.

Alternatively, the CSK..2RS Model 40 looks even better. It includes ball bearing (which look like they can take small axial loads), lubrication and lip seals and a smaller bore. Item 0741 modified for the extra width for the seals.


Will probably be required.

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Last Revised: February 8, 2005