System based on sprockets and toothed belts provides high and low speeds in forward drive and high speed in reverse. It is inexpensive to produce and maintain, light in weight, reliable, and long-lived without lubrication

Burch, J. L.

English

NASA Technical Reports Server

Slowly Turnina Sorocket 
with Ratchet 
Spring-
Latch in 
Cable-Actual 
Speed Shift 
Angular Coi 
Ball Bearint 
(Typical) 
Fixed Idler Two:
:lectric 
/lotor 
September 1970	 Brief 70-10193 
NASA TECH BRIEF 
NASA Tech Briefs announce new technology derived from the U.S. space program. They are issued to encourage commercial 
application. Tech Briefs are available on a subscription basis from the Clearinghouse for Federal Scientific and Technical 
Information, Springfield, Virginia 22151. Requests for individual copies or questions relating to the Tech Brief program may 
be directed to the Technology Utilization Division, NASA, Code UT, Washington, D.C. 20546. 
Two-Speed Wheel-Drive System Without Lubrication 
The problem: 
To devise a system for conversion of motor power 
to drive of individual wheels, as for drive of a vehicle's 
wheels by electric motors; the system should provide 
different speed ratios. Available systems use gears, 
shift mechanisms, and clutches and operate within 
lubricating baths; because no more than two teeth are 
engaged at a time, the loading on teeth is heavy.
The solution: 
A novel system, based on sprockets and toothed 
belts, that provides two speeds (high and low) in for-
ward drive and (with reversal of the motor) one speed 
(high) in reverse. It is relatively cheaply produced and 
maintained, light in weight, reliable, and long-lived 
without lubrication. At least four sprocket teeth are 
engaged at any moment.
0111 inued ocrIcau) 
This document was prepared under the sponsorship of the National	 Government assumes any liability resulting from the use of the 
Aeronautics and Space Administration. Neither the United States	 information contained in this document, or warrants that such use 
Government nor any person acting on behalf of the United States	 will be free from privately owned rights.
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How it's done: 
Two toothed belts and four sprockets transfer the 
rotation of the motor's shaft, reduce its speed, and 
drive the main driven wheel. The smaller sprockets 
are mounted on a rotatable plate, on a common cen-
ter line. When its latching pawl is released, this plate 
can be rotated 1800, the latch engages the opposite 
slot, and the belt driving the main wheel engages the 
opposite sprocket, which is rotating at a different 
speed. 
The alternate duty cycle is in effect low gear and high 
gear and requires no external power for operation. 
When the plate is rotated through only 90°, both 
slowly turning and fast-turning sprockets engage the 
main driving belt simultaneously; this phase of opera-
tion requires that the slower sprocket be driven 
through a ratchet that allows its shaft to turn faster 
than the sprocket until the plate completes its 180° 
rotation and the spring-loaded pawl again locks into 
place. Because of the ratchet, reverse drive can be in 
high gear only. 
The high-gear ratio is (D is "diameter of") 
D main-wheel sprocket

D fast-running motor sprocket
The low-gear ratio is 
D sldwly turning sprocket with ratchet drive
X 
D fast-turning motor sprocket

D main-wheel sprocket

D fast-turning motor sprocket 
N ote: 
No additional documentation is available. Specific 
questions, however, may be directed to: 
Technology Utilization Officer 
Marshall Space Flight Center 
Huntsville, Alabama 35812 
Reference: B70-10193 
Patent status: 
Inquiries about rights for commercial use of this 
invention may be made to NASA, Code GP, Washing-
ton, D.C. 20546.
Source: J. L. Burch

Marshall Space Flight Center 
(M FS-20645) 
Brief 70-10193
	 Category 07


Two-speed wheel-drive system without lubrication

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