Andrew Hanna, Dan Taub, Danny Zirkel
What is it?
Drive Train vs. Friction Plates
- Friction plate: connected to clutch basket
- Driven plate: connected to inner hub
- When clutch depressed: both spin freely
- When clutch not depressed: surface friction prevents slippage (allows transfer of energy)
Specs:
- Thickness: 1/8 in
- Diameter: 4.95 in
Cups / Springs
Purpose:
- Compress the clutch plates together when clutch is not engaged.
Specs:
- Free length: 1.4 in
- Compressed length (for testing): .77 in
- Force applied during testing: 40lbs=177.93N
- Spring constant: 761lbs/ft = 11,120.55 N/m
Lever
Purpose:
- Utilize mechanical advantage to lower the force needed on the handle.
Specs:
- Distance from pivot to push rod: .25 in
- Distance from push rod to applied force from cable: 2.5 in
- Mechanical advantage: 5:1
Not listed here: Primary Chain, Push Rod
The Science Behind
How much force is required to depress the clutch?
(Measurements based on ’58)
Force to release clutch without any mechanical advantage: ~200lbs
Divide by mechanical advantage of lever (5:1): ~40lbs
Divide by mechanical advantage of clutch handle (2.5/.6 =4.2:1): ~9.5lbs (with no friction)
Slippage:
Symptoms: Engine revs but no corresponding acceleration.
How: Clutch slippage is when the clutch plates are slipping across each other, rather than engaging and transferring engine torque to the drive train.
Why: The cause can be a poorly adjusted clutch, or worn springs, or worn plates.
Our clutch slips at between 6 and 9 ft lbs with well-compressed springs.
Working With the ’58
Clutch was heavy, noisy
**During testing, clutch cable “snapped”
Solution 1: We used emory paper to smooth out the teeth on the driven clutch plates, then buttoned up and attached new cable
Consequences: “Oh, well that’s just awful.”
Solution 2: We lubed cable to stop noise; tightened adjustment screw for better push-rod connection
Consequences: “…still worse than it’s ever been.”
Solution 3: Run cable along a straighter path (reduce friction)
Consequences: “The best this clutch has ever felt!”
Reassembling the ’59
