andypugh Posted October 8 Share Posted October 8 (edited) FWIW my dad used to say that gears should dip by twice the tooth depth + 1/4" (And as he worked as a gearbox designer at David Brown he ought to have known) Edited October 8 by andypugh 1 Quote Link to comment Share on other sites More sharing options...
dgrev Posted October 9 Share Posted October 9 Andy Interesting comment. Did he mean that rule applies to every gear in the box? Lets say with something like a transfer box, where the box sits at an angle, does that mean the top gear must be immersed to that depth or the bottom gear in the train? Once the gearbox is in motion, the oil will be transferred by the teeth meshing to the top gear I would think. So as long as the bearing for that gear is lubricated, is it really necessary to have the oil level to the lower part of the top gear, which brings with it lots of oil leak issues due to the lower gears being fully immersed and thrashing the oil much like a propeller on a ship? Quote Link to comment Share on other sites More sharing options...
Asciidv Posted October 9 Share Posted October 9 Following on from the question to Andy (above), I can appreciate how oil transfer from the teeth of the lower gear will lubricate the other teeth in the gearbox but this does not convince me about bearing lubrication. In a total 'guess the correct level' situation I like to see the lower part of the main shaft bearing under the oil. I haven't had any problems apart from the inevitable oil drips. Barry. Quote Link to comment Share on other sites More sharing options...
andypugh Posted October 9 Share Posted October 9 8 hours ago, dgrev said: Interesting comment. Did he mean that rule applies to every gear in the box? No, he meant the lower gear of the pair, which will transport the oil to the upper gear. (Presumably you would choose the oil level that satisfies at least this requirement for each pair in a change-speed box) The issue with having more that this (especially if you submerge the mesh) is that the oil in the mesh has nowhere to go, and this hydraulic force can increase bearing load. It also thrashes and heats/aerates the oil more. Bearings don't need a constant change of oil, there will typically be enough splash and oil running down the shaft to keep them adequately oily. Quote Link to comment Share on other sites More sharing options...
dgrev Posted October 9 Share Posted October 9 Thanks Andy, you have confirmed what I suspected. Quote Link to comment Share on other sites More sharing options...
flandersflyer Posted Sunday at 11:46 AM Share Posted Sunday at 11:46 AM Will you put a couple of magnets in that gearbox...? Quote Link to comment Share on other sites More sharing options...
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