SOHC.co.uk Forums > Anorak's Corner
Zinc content in oil
K2-K6:
I wondered if anyone else would dig up some interesting stuff in this area, but thought I'd add some more.
Like you've done with the mini transmission Totty, I use different application to help me explore some of the limits of this subject, makes for interesting comparisons of why the original design and specs called for some particular oil or procedure.
Following is why ordinary transmission don't necessarily need a heavyweight EP oil of the type commonly used in differentials. Generally gear tooth design places the meshing teeth very carefully against each other as they come into contact, with very little sliding between the faces coming into contact. It's sliding metal to metal that causes the most stress to oils. Wether the gears are straight cut or helical makes no real difference as far as I can see, helical just being quieter than straight as it's less prone to set up a resonance pattern with each tooth taking up drive slowly rather that all at once.
The need for those transmission oils specifically labelled EP comes from Hypoid gear arrangement used most commonly in axle differentials. What that design does is to take the pinion centre and offset it from the crownwheel axis. This involves a tooth design that is hyperboloid being a cross between a worm drive and a plain pinion. It's this design that has a very high amount of sliding between the gear faces and as such requires the special adaptions within the oil to resist oil breakdown and total destruction of it's shear quality that would effectively wear the metal. The advantage of using a Hypoid design is that the pinion can be much larger than a straight on axis design but without increasing the crownwheel diameter, this keeps the diff compact while allowing a high torque capacity in as small a space as possible.
Notably, the old Mini transmission, I think, drives from it's final drive onto the differential cage without any Hypoid gears, it's this aspect that makes it a technical oddity and doesn't require special oils of the degree discussed above.
AshimotoK0:
Really appreciate reading all this stuff K2-K6 . Just was this section was created for. Like 'Jensen' who I mentioned, you may not get a flurry of responses as the info takes a bit of absorbing, understanding and reading around. But it's here as a great reference and easily accessible outside of the 'day-day' forum posts.
In the early 70's I had a Honda CD175A sloper. The local Honda dealer 'Ken Blakey' who had been a dealer since early doors waxed on about using 'Filtrate' oil in Honda's (dark grey because it has molybdenum disulphide in it). So, at great expense, I replaced the 175 oil with Filtrate oil but at the next oil change I cleaned the centrifugal filter housing and was shocked to find so much black stuff in the housing that there was only a pencil size hole down the centre. So what was all that about? Does anyone else have experiences with Filtrate oil (it came from Leeds)?
AshimotoK0:
Some mention of it here . Perhaps it was colloidal graphite not moly.
http://www.voc.uk.com/net/docs/4.2/4.2-437-20.pdf
K2-K6:
As Totty says, they are very different as I understand it.
Our modern use of graphite is most commonly found is Graphogen used as an assembly lubrication particularly for cam lobes and followers, but as you found not applicable to general oil use for our bikes on this forum.
I've some interesting back stories of filtrate etc which I'll post next, just got go out and collect my daughter from school right now.
Nigel.
K2-K6:
Apologies Ash, I got my poster's mixed up there.
I understand it as that voc letter places it, the oils of that time when it was mostly in use were non detergent type so you expected the contaminants and particals from use to drop to the bottom of the sump to be drained out at change time. I'm not that knowledgeable about pre sixties oil filtration systems but ones I've seen have been fairly rudimentary in a basic gause type that would just stop any chunky bits going round again and leaving the graphite in its colloidal distribution to go round undesturbed.
For those looking information, this may help to place what they mean by colloidal.
http://www.whatiscolloidal.com/colloidal-definition/
I guess the Filtrate name effectively refers to a whole package that fits with the engineering of the time in working with contaminate dropout and preserving the additive it would do what they claimed. But as you found with a centrifuge oil filter (likely to be paper filter type as well) the engineering design effectively obsoleted their method. Curiously, a centrifuge filter could possibly out perform a paper type with a solution like that.
Interestingly, most car CV joints use that type of lubricant nowadays, embedded in grease, as it has some very long lasting non volatile properties that are very effective.
I've an odd connection with Filtrate also as my father swore by it for use in a Vincent Black Shadow he owned and raced. He got a third place on it in the 1953 TT 1000cc class using that oil which was provided to him by the factory. Think I've still got the letter of agreement from the oil factory.
More recently, I was standing talking at a bike meet to someone with a Vincent Black Prince, and was recalling my father's bike of which I new the reg no, he made just one phone call to someone that knew of Vincents currently owned and that person is the current owner of my father's bike. What a stunning coincidence.
Nigel.
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