The
Clutch
Andrew Hanna
Dan Taub
Danny Zirkel
Que es clutch?
O Is it:
O A: a firm grasp?
O B: a handbag without handles?
O C: A group of eggs fertilized at the same time,
typically laid in a single session and (in birds)
incubated together?
O D: a device that enables two revolving shafts to be
joined or disconnected as required, esp one that
transmits the drive from the engine to the gearbox
in a vehicle ?
O E: all of the above?
Exploded!
Our Exploded
Back Plate / Hub
O Purpose:
O Connected to main shaft; transfer rotational
energy from clutch basket to transmission.
Basket
O Purpose:
O House the clutch plates; connected to the
primary chain.
O Specs:
O 48 teeth (engine
sprocket has 18 teeth)
O Gear ratio of 2.67/1
Friction Plate / Smooth Plates
O Purpose:
O Friction plate: connected to clutch basket
O Smooth plate: connected to inner hub
O When clutch engaged: both spin freely
O When clutch not engaged: prevent slippage
with surface friction between plates (allow
transfer of energy between basket and hub)
O Specs:
O Plate thickness: 1/8 in
O Plate diameter: 4.95 in
Primary Chain
O Purpose:
O Transfer rotational energy from engine
sprocket to clutch basket.
O Specs:
O 3/8 x 7/32 in
O 62 links
O Duplex
Cups / Springs
O Purpose:
O Compress the clutch plates together when
clutch is not engaged.
O Specs:
O Free length: 1.4 in
O Compressed length (for testing): .77 in
O Force applied during testing: 40lbs=177.93N
O Spring constant: 761lbs/ft = 11,120.55 N/m
Lever
O Purpose:
O Utilize mechanical advantage to lower the
force needed on the handle.
O Specs:
O Distance from pivot to push rod: .25 in
O Distance from push rod to applied force from
cable: 2.5 in
O Mechanical advantage: 5:1
Push Rod / Adjustment Screw
O Purpose:
O Transfer of mechanical energy from the lever
to the pressure plate.
O Specs:
O Length: 7.01 in
O Diameter: .156 in
The Science Behind
O How much force is required to depress the
O
O
O
O
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
O Symptoms: Engine revs but no
corresponding acceleration.
O How: Clutch slippage is when the clutch
plates are slipping across each other, rather
than engaging and transferring engine
torque to the drive train.
O Why: The cause can be a poorly adjusted
clutch, or worn springs, or worn plates.
O Our clutch slips at between 6 and 9 ft lbs
with well-compressed springs.
’58: The Devil’s Dance
O Clutch was heavy, noisy
O During testing, clutch cable “snapped”
O Solution 1: We used emory paper to smooth
out the teeth on the driven clutch plates, then
buttoned up and attached new cable
O Consequences: “Oh, well that’s just awful.”
‘58 (continued)
O Solution 2: We lubed cable to stop noise;
tightened adjustment screw for better pushrod connection
O Consequences: “…still worse than it’s ever
been.”
O Solution 3: Run cable along a straighter path
(reduce friction)
O Consequences: “The best this clutch has ever
felt!”
‘59: Re-assembly
O Original parts:
O
O
O
O
O
Back plate / hub
Lever
Pushrod
Springs/cups/screws
Adjustment screws
O New parts:
O
O
O
O
Basket
Friction plates
Driven plates
Cable
Re-assembly
Dis wus the best presentA-tion ah eva did see!
Clutch Photoshoot ‘13