Where to hold crank while tightening crank drive sproket L/S

[G-Man]

If you're holding one end of the crank and doing the nut up at the other end, that's a great way of twisting the crank out of line. If you've ever trued a crank you'll know how easy they are to deflect.

Same fitting new outer bearings. Always support the crank close to where you are pushing.

Better to absorb the force as near to its application as possible.

Villiers used to supply a little block which fitted perfectly between the two primary drive sprockets.

https://villiersservices.co.uk/index.ph ... cts_id=418


G

If you have a strap wrench on the rotor there is no need to hold the brake.

[Seadog]

... If you've ever trued a crank you'll know how easy they are to deflect.

Amen to that!

[mike in idaho]

If it was that easy to twist a crank out of register it would get twisted every time you opened the throttle wide open. In first gear with the output shaft nut getting say, 50 foot pounds of torque, that torque figure would be divided by the ratio of first gear(2.788:1) then divided farther by the ratio of the primary drive(3.13:1)= 5.73 foot pounds at the alternator bolt. I think the crank will handle that.

[G-Man]

Just not good Engineering practice.

Supporting the applied force directly by locking the sprockets is easier and safer all round. The sprockets are designed to transmit torque. The alternator rotor is not.

Multiplying or dividing by the primary drive or gearbox ratios is irrelevant for the torque being transmitted from one end of the crank from the other.

If you look at the wear marks on the big ends these built-up cranks twist under load and the wear occurs at one edge of the crank-pin/rod/roller as they are pushed out of parallel.





G

If it was that easy to twist a crank out of register it would get twisted every time you opened the throttle wide open. In first gear with the output shaft nut getting say, 50 foot pounds of torque, that torque figure would be divided by the ratio of first gear(2.788:1) then divided farther by the ratio of the primary drive(3.13:1)= 5.73 foot pounds at the alternator bolt. I think the crank will handle that.

[bill440cars]

Just not good Engineering practice.

Supporting the applied force directly by locking the sprockets is easier and safer all round. The sprockets are designed to transmit torque. The alternator rotor is not.

Multiplying or dividing by the primary drive or gearbox ratios is irrelevant for the torque being transmitted from one end of the crank from the other.

If you look at the wear marks on the big ends these built-up cranks twist under load and the wear occurs at one edge of the crank-pin/rod/roller as they are pushed out of parallel.





G

Sounds like sound advice there, G-man, and much appreciated, especially since I will be getting into one of these motors, before long, myself. Since the crankshaft is "Pressed together", it is very understandable, how making the wong move, could throw things out of whack.

[LOUD MOUSE]

Looks more like water pitting than side play wear to me. ...............lm

Just not good Engineering practice.

Supporting the applied force directly by locking the sprockets is easier and safer all round. The sprockets are designed to transmit torque. The alternator rotor is not.

Multiplying or dividing by the primary drive or gearbox ratios is irrelevant for the torque being transmitted from one end of the crank from the other.

If you look at the wear marks on the big ends these built-up cranks twist under load and the wear occurs at one edge of the crank-pin/rod/roller as they are pushed out of parallel.





G

If it was that easy to twist a crank out of register it would get twisted every time you opened the throttle wide open. In first gear with the output shaft nut getting say, 50 foot pounds of torque, that torque figure would be divided by the ratio of first gear(2.788:1) then divided farther by the ratio of the primary drive(3.13:1)= 5.73 foot pounds at the alternator bolt. I think the crank will handle that.

[G-Man]

LM - Not side play wear just high contact force causing classic rolling contact fatigue. High contact forces cause the metal to crack under the surface.

Then the cracks join up and the bits break away (spalling). This happens at the highest contact force part of the power stroke.

If the two bearing surfaces are not in parallel contact the local contact force is higher.

http://www.tribonet.org/wiki/rolling-contact-fatigue/

G

Looks more like water pitting than side play wear to me. ...............lm

Just not good Engineering practice.

Supporting the applied force directly by locking the sprockets is easier and safer all round. The sprockets are designed to transmit torque. The alternator rotor is not.

Multiplying or dividing by the primary drive or gearbox ratios is irrelevant for the torque being transmitted from one end of the crank from the other.

If you look at the wear marks on the big ends these built-up cranks twist under load and the wear occurs at one edge of the crank-pin/rod/roller as they are pushed out of parallel.





G

If it was that easy to twist a crank out of register it would get twisted every time you opened the throttle wide open. In first gear with the output shaft nut getting say, 50 foot pounds of torque, that torque figure would be divided by the ratio of first gear(2.788:1) then divided farther by the ratio of the primary drive(3.13:1)= 5.73 foot pounds at the alternator bolt. I think the crank will handle that.