Guide Rolls Gearbox

If you want a good answer you MUST give full information:

- make a sketch of kinematics

- a picture of the whole

- a picture of the broken shaft of the broken part and of the part which still in the box bearing.

I did not make any computation but if it is a cantilever the highest probability is you get a combined torsion+bending fatigue. This can have several reasons thus the need for informations.

Thank's guru for answering my question. I will send you complete drawing and photo tomorrow.

br

Does it stall for any reason (i.e. due to obstructions), if so then the actual torque will increase dramatically and so does the shear stress. My guess would be in that case that it is torsional shear of the input shaft.

Dutchy

Dear Guru,

Attached is the picture that you need. the same problems happened on the pinion input shaft, it was broken like attached output pinion shaft.

Sorry to sending you late picture.

Br

Zainal Abidin

It is ok but the pictures do not show important details.

You should make pictures of the failed surfaces on both sides so that the fracture can be looked at and analysed.

What is fastened on the left side of the shaft? Is it a gear? is it a coupling? Is that the part of the shaft coming out of the box?

Make also 3 pictures of the input shaft as for the output one.

I imagine that it could be a problem of side loads due to misalignments but as long as I do not see the fractured surfaces it is difficult to go further.

Concerning the input shaft it is even more difficult to explain since the assembly is, due to the box, well centered and I doubt that the manufacturer will deliver misaligned boxes. It would be good to know how the motor shaft is connected to the box thus the need for gearbox schematics.

Could you make a sketch of the gear box to show where are the bearings and where are the gears?

There is also a possibility depending on the different inertias that the system motor+gear box+ cylinder show torsion vibrations and those lead to an early fatigue, there is also the possibility that the start is too brutal and the torque is too important with respect to the designed one .

It would be of help to know:

- motor power, nominal RPM - diameter of broken shaft and radius between broken part and next shaft step since it seems that the crack developed at a high stress concentrator spot, - diameter and length of the cylinder and its material (for inertia calculation), - type of coupling between output shaft and cylinder.

All those data are required to make a serious analysis and come as near as possible to the most probable reason.

Take your time, as soon as I have the data I shall analyse them and send you the results.

Nick

will send you req info asap.

br

Zainal Abidin

Dear Guru

please find attached the drawing that you req

in addition:

input shaft connection is using rubber spider coupling, the motor capacity is 4kW/1740 rpm, coupling type as seen on the attachment file.

Thank for kind cooperation. Please let me know if you need some more data

br

Zainal Abidin