How thin the oil?

Hobot · May 27, 2012

A different oil thread. Anyone got any thoughts experience on lower grade oil in a fast turned Commando? My thoughts are less friction and more heat carrying capacity in a special. Nortons don't seem to need to show oil pressure at speed - if one can trust Norton factory wisdom to quickly drop the oil gauge option. Any horror stories on using 30 grade or less in a pinch?

1up3down · May 27, 2012

Steve,

I don't think we really have much mechanical reason to put in a lighter oil than 40 weight

And the reason is because these are air cooled motors without the benefit of closer tolerance water cooling manufacture that insures a more even cooling distribution throughout the engine

In addition, our motors were designed and built 40 years ago when manufacturing tolerances where slightly more "forgiving"

For the above reasons, most knowledgable people agree that 40 weight is the lightest oil we should be using,
and many of us believe straight 50 or a 15-50 or 20-50 is the ideal

john robert bould · May 27, 2012

oil is designed to lube,prevent rust , carry away heat etc etc.
On a cold start the engines parts are "nicely" held apart by the "goo",providing hydraulic buffers, thicker the "goo" better the gap filling and more important "Better" at resisting from being sqeezed out.....as it thins with heat the less this lingers in the gaps, But thicker oil sap's power ..so quite over power,your choise

Dances with Shrapnel · May 27, 2012

Getting into the realm of rheology and lubrication.

Thinner (less viscous) is generally better up until you reach the point of introducing another problem as a result of the lower viscosity. Oil can also be too viscous in that it does not flow adequately to remove heat.

The term used (and worth searching on) is hydrodynamic wedge. I recall their being three or more phases of lubrication starting with the zero movement start up phase where additives provide the metal to metal protection. The final (normal operating) phase is when an adequate hydrodynamic wedge forms.

Rod bearings, rings, cam followers, piston skirts and a few sleeve bearings are (in my opinion) the critical bits, the rest (main bearings, cam chain, oil pump seals etc) are fairly tolerant.

As mentioned earlier by someone else, in some instances water is used as a lubricant. One example I can think of is in old grinding mills where the bearing surfaces would be mycarta (sp?) or wood blocking turned up on end and water would be fed under pressure. Once the mill was underway there was very little friction and plenty of cooling.

As for Norton's not having to show oil pressure at speed, I rationalized and calculated away my one experience with this on a short stroke Norton twin. Basically the centripetal force "apparently" assures adequate pressure at the rod journal and the pump provides the feed rate. If you have pressure and feed at the journal - life is good.

1up3down · May 27, 2012

Dances said:

As mentioned earlier by someone else, in some instances water is used as a lubricant

I presume you were referring to me, the someone else, as I was the only poster so far that even mentioned water.

To be clear, my reference to water was to its ability to cool, and had nothing at all to do with it as a lubricant, which I have never heard of it being used as.

Dances with Shrapnel · May 27, 2012

1up3down said:
Dances said:

As mentioned earlier by someone else, in some instances water is used as a lubricant

Click to expand...

I presume you were referring to me, the someone else, as I was the only poster so far that even mentioned water.

To be clear, my reference to water was to its ability to cool, and had nothing at all to do with it as a lubricant, which I have never heard of it being used as.

Who knows, I dont' know, it may have been you.

Once you are on and are able to maintain a hydrodynamic wedge it does not matter much which fluid is being used. Another example of a water lubricant would be on select pump shaft seals.

Now as I recall, these old mills with water bearings would need to be jacked up some how prior to start of rotation. Interesting stuff

Hobot · May 27, 2012

Dances we have women on the list so watch your language eh.
Ok so no one really knows yet how thin a HI spun Cdo engine can exist on -just- thank goodness the crank sling feeds enough at speed and sucks enough head off oil pump it can keep up when oil hot and thinned enough.

I'm a water skier and hydro plane kiddo so know about hydrodynamic wedge surfing support and that water is a decent lube if not reaching its vapor phase temp. An asymmetric wedge forms to hold shaft slightly in eccentric in bore d/t the shaft rotation and driven load.
There are stories of people getting away with water in place of engine oil to escape situations but had to top off or cool off to prevent seizures. Can even work hydraulics for a time till rusted up.

The ZADP only forms its zn/phos nano pads over 200'F surfaces and the things that cause over that temp like actual metal/metal contact wipe it right off before cool down.

I noticed lower temps and maybe more spunk on 15/40 diesel grade oil in Peel. Had oil leaks couple times that I got home more safely by couple quarts of cheap 30 grade farmers had on hand. But too timid to test endurance and temps on limp home to stifle the leak. I've used far more 15/40 in Trixie than 20-50 or plain 50 and hear no extra engine noise. Checked the lifters/lobes and rocker/valve stems on Trixie after 7000+ miles to not see any evidence of wear just better polish burnish on contact surfaces. cool.

Definitely noticed less drag and lower gear box temps with ATF inside. Going by the brief sincere feedback's implies heat is more important than oil wedge issues. Ie: maybe 5-30 grade might separate parts ok yet carry away significantly more heat. If surfaces not getting too hot they can take more pressure w/o wear, which is also a chemical phenomena at these pressures and temps.
1st is metal-metal contact
2nd is oil slickness
3rd is oil surfing wedge
4th is oil vaporizing even to detonation
5th is metal-meat elastic deformation, metal surfaces turn into traveling wave shapes
6th is metal-metal plastic deformation, metal deforms permanently to start galling
7th is metal explodes into basic elements disassociated into a hi temp plasma.

i called a thermal engineer on what grade they use in transformers and other oil heat conductors to be told as thin as water or it don't carry off heat just absorbs it and hangs on to it more.

After timid run in of Peel on 15/40 hi detergent oil I'll work down to at least 10-30 monitoring best I can, even with nil pressure on gauge. I think I want her oil temps to get almost to boiling when fed into oil pump. So 2 gauges needed one on intake as well as out let. Alan Goldwater already told us how hot oil gets in front of head but nothing can be done about that w/o new engine design.

1up3down · May 27, 2012

After timid run in of Peel on 15/40 hi detergent oil I'll work down to at least 10-30 monitoring best I can, even with nil pressure on gauge. I think I want her oil temps to get almost to boiling when fed into oil pump

Steve, what is your reasoning for planning on putting in 10-30 because as you say you want your oil temp to get almost to boiling?

How does this benefit your engine to have oil almost to the point of boiling?

Dances with Shrapnel · May 27, 2012

hobot said:
Definitely noticed less drag and lower gear box temps with ATF inside.

ATF in gear box is a bad idea in my opinion. Sure lower drag and if lower temps, because of reduce shearing (maybe). What's necessary is extreme high pressure performance at the gear tooth interface. Not sure if ATF is up to the task. That is why recommended hypoids have sulfur since sulfur acts as an extreme pressure lubricant.

hobot said:
Going by the brief sincere feedback's implies heat is more important than oil wedge issues.

Both are important. Too much heat and the lubricant boils away or breaks down and the hydrodynamic wedge goes away. This is why oil flow is just as important as oil pressure. No hydrodynamic wedge and too much friction resulting in too much heat.

hobot said:
i called a thermal engineer on what grade they use in transformers and other oil heat conductors to be told as thin as water or it don't carry off heat just absorbs it and hangs on to it more.

Different application. Transformers usually rely on convection of the oil to remove heat. More viscous oil reduces the rate of convection. In our applications the oil is being forced through the journals.

Flo · May 27, 2012

I have been using semi synthetic 10-40 for 4 or 5 thousand miles now. Engine feels slightly free-er & more responsive
May seem daft to say, but engine sounds mechanically quieter. Does not wet sump any quicker.

1up3down · May 27, 2012

Steve, what is your reasoning for planning on putting in 10-30 because as you say you want your oil temp to get almost to boiling?

How does this benefit your engine to have oil almost to the point of boiling?

conkers · May 27, 2012

1up3down said:
Dances said:

As mentioned earlier by someone else, in some instances water is used as a lubricant

Click to expand...

I presume you were referring to me, the someone else, as I was the only poster so far that even mentioned water.

To be clear, my reference to water was to its ability to cool, and had nothing at all to do with it as a lubricant, which I have never heard of it being used as.

We had a Stuska (water resistance) engine dyno at the competition engine company I worked after leaving college, the bearings in the dyno units were lubricated by the water that was fed into it....

Mike

steveyacht · May 27, 2012

Not sure why you want a thinner oil, but many racing engines, particularly those used for qualifying will use 0 (Zero) weight oil. Many automobiles manufacturers have also specified 0w-20 in order to help acheive a higher CAFE rating. If you are attempting to lower friction losses caused by higher viscosity oils you may want to try a 0w-20 Synthetic.

Hobot · May 27, 2012

Well I asked for it on an oil thread didn't I : )

I hope Peel can process about 3x's the heat a Combat does but that requires hi rpms. I have seen enough wear surface articles to "feel" and think heat is more the issue than oil wedge maintenance in Peel. Only place oil wedges matter in Nortons are rod journals wide areas and the cam lobe/liters, not the crank bearings or rocker shafts or valve stems guides or TS drive. Peels cam gets oil pressure to aid its ends and lobes. Our engines don't depend on any oil convection to carry heat off so thin oil does indeed carry off more than more viscus oil as engineer verified in activity pumped coolers.

AMC trannies can not get thick oil into the sleeve bushes while in lower gears at much rpm. I'm sticking to ATF in Peel, even with a ITT eventually but I put what ever in my plain Jane Trixie, I rarely rev long below 4th.

Most of Peels frame is oil filled surface area so may have to insulate to get near 200'F oil fed back into engine. Racers live fine with these oil temps so why not Peel and it takes about boiling hot oil to get much benefit of ZADP protection on next cold start, which wipes it off till oil pressure kicks in.

Appreciate the really scary thin 0 grade in extremist race engines. Got to be a safe more effective thinner viscosity oil a tight Cdo type engine will like and tolerate. Yes I'm hoping a detectable increase in power too as my bait fish targets are getting quicker all the time.

Dances with Shrapnel · May 27, 2012

hobot said:
Our engines don't depend on any oil convection to carry heat off so thin oil does indeed carry off more than more viscus oil as engineer verified in activity pumped coolers.

I think you have the logic a bit twisted around. Transformer oil you referred to earlier must be thinner so that it will more effectively convect where heat transfer depends on convection.

What is an activity pumped cooler that you are referring to?

In something a little more dynamic such as our lovely Norton twin engines the oil is force fed through journals and is being constantly replenished (slinging and misting) throughout the internals; it is not relying on convection to transfer heat like many large transformers.

Hobot · May 27, 2012

I don't understand your confusion, thin oil has more heat absorbing and releasing capacity than than thicker oil.

Examples of active oil flow exchangers - for one flowing through engines and their oil coolers plus other applications that reclaim oil heat and use it in other places. But your are correct, thin oil that needed in passive convection coolers applies to active flow exchangers too. Lava lamps taught me stuff in the 70's.

The limiting issue seems to be rods and cam. Our rod journals with the sling out force feeding may not need gear oil thickness to stay separated, especially w/o the useless rod jet hole. Oil pressure through cam bushes and lobe should lessen its need of sluggish oil in Peel,I have skied on almost molecular thin sheets of water on a dinner plate size support. Thin oil may stick around if good flow. Don't really know what can get away with - that still has a detectable advantage, wear or heat wise. 30 grade is pretty much universal engine base line that's acceptable in mowers to hot rods even Volkswagen. Will check CHT EGT and oil to see what that reveals. Synthetic of course for its extra advantages and not step too far off the beaten path.

I've got in mind a sound transducer like a knock sensor or such to get baseline sound signatures then hear what changes as oil grade thinned down, put other stuff too.
Digital age ears not old battle of bands blown ones.

Chili · May 27, 2012

Dances
re: the water cooled bearings, the stern tube on older ships had wooden (lignum vitae) blocks the length of the tube, which the shaft ran on, then sea water was pumped through, for both cooling and lubrication.
Chili

1up3down · May 27, 2012

So Steve,

What do you suppose is the reason why the chief engineers at Norton, Triumph, BSA tested and stated was the necessary and correct weight oil for their air cooled twins, both street and all out race bikes?

They really knew as you do that hot thing oil is really better but just wanted to keep it a secret forever?

ATF was available way back when they built AMC gearboxes, why do you suppose they did NOT recommend it?

And why would you assume that you know more than those engineers did?

Just naturally smarter I reckon?

Hobot · May 27, 2012

even a multi-grade like 5w30 is still too thick to flow efficiently when cold. Auto manufacturers choose an engine oil "weight" for OPERATING temperatures, not for when the engine is cold. Even a 5 or 0w oil, when cold, is thicker than a 40w at operating temp. This causes restriction in the small orifices in parts such as lifters, which is the most common source of engine tick when an engine is cold. BTW, cold is defined as a temperature less than the oil's effective operating range, 180-250F for example. That said, an oil at room temperature is still too thick. Google it.

Read more: http://wiki.answers.com/Q/What_would_ca ... z1w84kaM7U

Amsoil say 20 'wt' is too dam low even in tight new engines that run coolant to 205'F. Check.
[video]http://www.youtube.com/watch?v=DO3DcY92yxc&feature=related[/video]

This make me feel better about asking.

For example, you can switch from a low viscosity index conventional 20W-
50 to a high viscosity index synthetic 10W-40, but the oil clearances in the engine must be tight enough. At .001 oil clearance per inch of journal diameter, most racing engines can run a high viscosity index, synthetic 10W-30.
Using too thin of an oil with loose clearances will result in rod bearing failure.

http://www.joegibbsdriven.com/trainingc ... takes.html

Dances with Shrapnel · May 27, 2012

hobot said:
I don't understand your confusion, thin oil has more heat absorbing and releasing capacity than than thicker oil.

No confusion, just that you are running with misconceptions.

Unless you are going to run heat transfer oil or transformer oil in your engine, for all intents and purposes there is little difference between the various engine oil weights in their ability to remove heat. It is a matter of mass flow per unit time.

How thin the oil?

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