Lang

excessive backlash can cause scuffing

Higher speed ranges on the output portion of the gearbox could be matching resonant frequencies, no matter if you're using premium quality gears, I guess you have to replace the whole gearbox, unless it is intended for higher output upgrades, in wich case you have to ask the manufacturer for the correct kit.

Yahlasit

Thanx farmatt. I once raised the backlash issue but the manufacturer defended himself using the standard (AGMA). However I am going to persue the backlash issue as well. What about the high gear mesh vibration.

Guest thanx to u too. But this one is a low speed gearbox. Output speed is 43rpm and the motor rotates at 980rpm. What migt be causing the vibration.

Formatt, can you explain how excessive backlash causes scuffing. If this is the problem I need to give such an explanation for us to be able to solve tha problem.

Hi, I guess your gear box is related to coal pulveriser. If it is so you check the axial float and radial lift of your driving shaft on which the pinion is mounted. It should be within 0.5mm and 0.15mm respectively. Now come to the meshing of gear teeth. Check contact area by applying blue on teeth. It should be on the middle of teeth surface with a distinct band. Toe or heel contact can cause wear of teeth excessively and also vibration. Backlash is very important in this regard as excessive backlash cause intermittent power transfer and impact in regular intervals on driven tooth which turns into vibration and damage to gear tooth showing shining surface and sharpe edges as well as insufficient backlash causes locking of gears as found in self locking machine like worm & wheel arrangement . Keep backlash within 0.4mm to 0.5mm. If your lubrication is forced then root gap does not matter so,otherwise it must be within manufacturer's recomendation. Also driven shaft bearing clearances to be checked to their limit. Keep a close look on both driver and driven shaft thrust bearings ,thrust plates and shims on those if any. Please note that values given are reffer to E70/62 coal mill as I told earlier I guessed. Hope it will help.

That makes sense. Also check the alignment of the shaft bores on the box casing.

Suranjan thanks for the insight. Can you post a sketch showing the direction of the clearances I need to measure. ie the axial float of the pinion and the vertical lift of the output shaft. I am not sure if I understood you well.

Hi Guest, I am try to describe you the matter but I cann't post you a sketch now. Please note in my previous comment I have told you about bevel and pinion arrangement of E70/62 coal mill wheather it is applicable for any bevel gear and pinion arrangement. Pinion is generally mounted on driving shaft which is assembled with bearings, thrust coller, shims etc. and lub oil guide ring. After proper assemblly of pinion shaft housing put the housing horizentally and strick gently either pinion end or pully end of shaft untill it's movement completes. Now set a dial guage at the stricked end and now strike at the opposite end untill movement stops. The deflection of dial indicator will show you the axial float of shaft. That means the maximum axial movement of shaft after assembly is the axial float. The radial lift is basically the radial bearing clearence and can measured in this method. Put assembled shaft housing horrizentally and set a dial guage keep dial pin on top of the shaft. Now lift the shaft gently by a tommy bar or cotton/PU sling vertically. the deflection in dial indicator will show the radial lift. Take it on both side of shaft and consider maximum value. For better result set dial guage at the end of the shaft as far as possible. Hope it will work. Please let me know the result of your action. I am ready to help. Thanks.