How to repair a crankshaft

[Bigbjorn]

Some of you engine repairers, restorers, and builders may find this clip interesting.

YouTube (https://www.youtube.com/watch?v=ozjP2IT2wCU)

The crankshaft is at about the 9.10 minutes mark.

[goingbush]

Oh , only a small crankshaft then ! [bigwhistle]

I can't figure out the point of the belts swinging on the journals ??

[Blknight.aus]

Oh , only a small crankshaft then ! [bigwhistle]

I can't figure out the point of the belts swinging on the journals ??

They support the weight, and hang from a set of balanced rams that are computer controlled so the crank turns evenly preventing any dishing of the journal that being ground.

[Bigbjorn]

They support the weight, and hang from a set of balanced rams that are computer controlled so the crank turns evenly preventing any dishing of the journal that being ground.

No, the weight is supported in the headstock and tailstock. The belts are a type of vibration dampener to prevent miniscule flat spots from AC power cycles. I have a photo somewhere of a small crankshaft being finish ground in a milling machine with a loose drive belt on the grinder motor to remove the cyclic motion. If I can find it I will post it.

[Bigbjorn]

Oh , only a small crankshaft then ! [bigwhistle]

I can't figure out the point of the belts swinging on the journals ??

Only a mid size one. This clip is a big one.

YouTube (https://www.youtube.com/watch?v=v4GGpJcTXIE)

[Blknight.aus]

No, the weight is supported in the headstock and tailstock. The belts are a type of vibration dampener to prevent miniscule flat spots from AC power cycles. I have a photo somewhere of a small crankshaft being finish ground in a milling machine with a loose drive belt on the grinder motor to remove the cyclic motion. If I can find it I will post it.

Given the crank is 37 feet long and has a reaction plate preventing flex away from the grinding wheel the grinding wheel looks like its about 6-8 feet in diameter and probably ways a couple of hundred kilo spinning at maybe 400RPM, the crank is turning at something like 8RPM and has a mass of in the order of 15T The chances of minisucle flat spots is more or less approximately 0. Theres just way too much mass on the move through too much reduction for a the piffling of torque pulse from an electric motor to be noticed. Maybe if one or the other was being driven by something like a 15 pole 3 phase motor on a direct or low reduction but even then, doubtful

If it was for vibration control for the crank you could get away with a large sheet of rubber layered around the adjacent journals with a weight collar bolted in place


It would be a very brave machinist who tried to grind anythingthat's 37 feet long without additional support to prevent bowing.

[Bigbjorn]

This mob do a bit of crankshaft work, various sizes.

YouTube (https://www.youtube.com/watch?v=8pGBHZuq9FY)