Lubrication system. Please explain.

G'day all... As I'm about to start the rebuild of " Compound Fracture", or more honestly, help with the rebuild, I need to ask this rather embarrassing question as I can't really find a clear explanation in any of my books or on the Forum.
Could someone please explain just how the Oil is moved around the engine. The bit I don't get is that the pump obviously pumps more (faster) than the return to the lower Crankcase, or else it wouldn't pump out the Cases after Wet sumping...Does the Pump therefor suck air most of the time....The tank is not pressurised, or else you couldn't remove the cap while the engine is running... Thanks all...
AC. P.S. Anybody caught laughing will be set upon by Bandits.

AussieCombat said:

Could someone please explain just how the Oil is moved around the engine. The bit I don't get is that the pump obviously pumps more (faster) than the return to the lower Crankcase, or else it wouldn't pump out the Cases after Wet sumping...Does the Pump therefor suck air most of the time....

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Yes, the scavenge side of the pump (which draws the oil from the sump and returns it to the tank) has a much higher pumping capacity than the feed side, therefore (theoretically) the return system should always clear any excess oil, and due to the extra capacity the scavenge system will draw in a certain amount of air once any excess oil has been cleared.

AussieCombat said:

The tank is not pressurised, or else you couldn't remove the cap while the engine is running...

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The tank as you say, is not (or should not become) pressurised, as any build up of air pressure inside the tank would eventually slow down or even stop the oil returning to the tank.

http://www.oldbritts.com/oillines.html

Here's a picture of the return (scavenge) flow during a test I did driving a Norton oil pump with a drill motor. Yes bubbles and froth.

And that is why the return oil is squirted out of those two little holes up under the filler cap. Not just so you can see if there is oil return but it helps get the air bubbles out of the oil. Do away with that feature when you build a custom tank and you will end up with frothy oil. Jim

Be alert some manuals instruct on wrong oil manifold tube to hook inlet and out let hoses to. Oil goes down the outside manifold stand pipe. The main flow paths are pretty obvious and well illustrated in graphic but the bypass pressure valve paths is still a mystery to me.

I can only hope Ms Peel's one in a row OIF design can handle the foaming return oil and vent it out exhaust.
Sure would like to see video of how much oil bypass can spray out over engine needs at 6000 rpm.

Yeah thanks for that, it is much clearer now. Coloured diagrams are a great help when you'r not sure.
I have fitted an oil filter, so when it comes to bleeding the oil lines, pre startup, is kicking the engine over ( no plugs ) good enough ?
I have considered running the engine first up, with the return going into a container, just to be sure all is ok and it might take some of
the original crap away. All new inside including Cam which came with a tube of Lube.
It's getting exciting now. Haven't rebuilt a Norton before, never had to...
Must say it is a little different to the inside of these... BSA Bantam, James Cadet, 350 Mack Velo, RT 360A, ( you think Nortons can kick ), TS 250 Suzuki,
250/360 VA Montessa, CCM 500/560, TT500, 250KX A4, TD 250 Yam, TR 350 Yam, TZ 250, ATK 560,... Bla Bla Bla......Loved em all.
.AC. P.S. Norvill site says... Words to this affect.... All new Cams should have new lifters, and to run the engine on initial start up at NO LESS THAN 2000 rpm..?
Hobot... Yes I hope Ms Peel is ok.

I used a pump type oil can and an extra banjo fitting. Made a connection with a piece of tubing and pumped 12 to 16 oz to prime the system. Squirt some on the lifter and around the pushrods for good measure. I then crack open the fitting on the left, (far side of the head and kick it over til oil came out. That was enough to insure lubrication on initial start up.

That makes sense too..AC... Posted at 11.50 am. Thurs.. 14th.

For Hobot - Found a good pic of the oil milkshake just after a run. Again with the drill motor so no engine heat generated. The pump gears just really aerate the oil. As long as you feed your oil from the bottom of the OIF "tank" you may be OK. (Maybe a black and tan not a milkshake.)

Boy that makes two shots of moisture laden aerated return oil. Ms Peel OIF will allow many feet of travel for bubble to pop out to top of spine tube, but hoping the exhaust eductor can suck off the pressure build up. If not I'll have to outward vent maybe to gas tank if not the ground. Peel has one way inward check valve so no suckion can develope in spine, extra pressure just pushes more to pump, I hope.
Peel will feed oil to engine completely on either side, standing on tail lens or on head light, only upside down can starve her, but don't spend much time like that on the few occasions me and her have been upside down.

Putting factory Trixie oil lines on tonight, got stereo in shed today after 12 yr w/o.
Temps mild, wife not in mood again so spending it with another mistress even Ms Peel puts up with, because Ms Peel has changed her ways and is under my thumb like the song sings.

batrider said:

For Hobot - Found a good pic of the oil milkshake just after a run. Again with the drill motor so no engine heat generated. The pump gears just really aerate the oil. As long as you feed your oil from the bottom of the OIF "tank" you may be OK. (Maybe a black and tan not a milkshake.)

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how fast were you spinning that oilpump with your electric drill?
the speed does matter as does the way the exit is designed
when we (pol and me ) were trying to dry sump an nsu car engine the speed of the return pump was important or we had what you show in the pic ; foam . the returnline was angled towards the side of the oiltank to promote some swirl and the oil ran over a plate soas to be able to let go of the trapped air
So i think your pic does not really tell us anything .sorry.....
come to think about it ;the speed of the feedline matters of course as well or you get cavitation ,but that is nothing to do here

I bought a laser tach just to check my drill speed. This was the equivalent of running 4100 rpm engine speed. The Matchless uses the Domi pump with 3-start gear so pump was actually spinning slower than it would be in a Commando engine.

Edit: Found my notes from 2 years ago:

> Drill Speed (Applied to pump shaft): full speed actual 988 rpm measured
> with digital laser tach. This corresponds to 4610 engine rpm using the
> 14T pump gear and 3-start worm.

What I was doing was comparing various Norton pumps I had around to get a handle on an over-oiling problem I was having with the G80CS and also this test verified that the scavenge passages were clear. On a Commando with 6-start gear this would be equivalent to 2305 crankshaft rpm. Oil was Pennzoil 10W-40 which I happened to have around for the cars. (The purpose was not to see how much foam I could make so I didn't care about optimizing the oil exit. Just thought hobot might be interested in seeing this since he is making his own tank.)

Informative to me to see the golden foam even in new oil w/o extra heat or moisture involved, ugh. Did you find much variation in various pumps outputs?
Turned at same rates of course.

I don't remember how many times I spun rod bearings in my first racebike before I figured out what was happening. At least 3 times. It would only happen on fast tracks with long straightaways. An oil pressure gauge told the story. After a few long high rpm straightaways you would see the gauge start to surge and jump around and then the left rod bearing would seize a few seconds later.
I had a 3/8 hose and fitting simply dumping oil into the top-side of the tank. Fixing the oil tank so the oil return sprayed against the side of the tank a couple inches above the oil level was enough to cure the problem. Jim

Mainly I was comparing a Dominator pump to a later Atlas pump. When I first got my Matchless G80CS in a yard sale the original pump had the drive gear snapped off and the crankpin was broken. When rebuilding I put in a late Atlas pump which came from a pile of parts that someone gave me.

After that I had an over-oiling problem which went on for many years. The sump would fill when the bike was running and eventually spill over into the primary chaincase (no lipped seal) which would also fill and then dump out onto the rear wheel. This took about 15-20 miles starting with a drained sump and drained primary chaincase. Through the magic of the Internet I later found out that the Matchless was supposed to have the Domi pump which has narrower gears and thus about 25% less output. The Domi pump solved my problem. I think the scavenge drilling in the crankcase was too small to accomodate all the oil being pumped into the engine.

BTW -- Was thinking the heat would probably help to thin the oil so the bubbles could do their bubbling thing and pop easier.

Great thread. Learning stuff. Thanks to all.

lynxnsu said:

...the speed of the feedline matters of course as well or you get cavitation ,but that is nothing to do here

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Just a point about cavitation and the Cdo oil pump: being a gear pump, it's generically a "positive displacement" pump, meaning it simply moves whatever appears at its entrance - air or oil - by increments of volume, not by increasing the energy of the flow, as in a centrifugal pump. Cavitation (defined as a reduction in fluid pressure below the vapor pressure of the fluid) is not relevant to the operation of a gear pump, and bubbles in the flow - supply or return - are not a result of cavitation, since the fluid pressure is above the vapor pressure of the oil at all times except possibly within the pump somewhere, but probably also even there - oil has a very low vapor pressure, so it takes a pretty good pressure drop to get under it.

To the original question, the oiling scheme relies on the flow capacity of the scavenge side being greater than the supply side, which is set by the relative width of the gears - there are four gears. all the same diameter, with the two scavenge gears being wider than the two supply gears (brilliantly simple way of assuring scavenge). The oil level in the sump is set by the position of the intake. Since the scavenge side has more capacity than the supply side, the oil level in the sump falls until the intake sucks air, then it stops falling (also a brilliantly simple level control scheme). Thus under normal conditions there will always be bubbles in the return line to the tank, which serves to enable the air to separate from the oil as well as to radiate some heat. And as has been pointed out in another thread, the pressure at any point in the supply side of the system - or return side, for that matter - is set by the flow resistance existing there. Pressure really only matters for the plain rod bearings, which require enough pressure somewhere upstream to ensure flow to replace the oil squished out every rotation of the crankshaft, otherwise the surfaces touch (and no, the oil pressure doesn't keep the surfaces apart, the hydrodynamic wedge inside the journal does). In the roller main bearings, the roller and race surfaces normally touch - well, there is the film strength to keep them microscopically apart - and the oil serves to reduce the friction and temperature associated with that - thus they just need to be kept wet (but not submerged, because that would cause too much viscous drag and froth etc.) and the heat get rejected somewhere. The top end is basically the same story as the mains.

Qutoe: Kartiste
To the original question, the oiling scheme relies on the flow capacity of the scavenge side being greater than the supply side, which is set by the relative width of the gears - there are four gears. all the same diameter, with the two scavenge gears being wider than the two supply gears (brilliantly simple way of assuring scavenge). The oil level in the sump is set by the position of the intake. Since the scavenge side has more capacity than the supply side, the oil level in the sump falls until the intake sucks air, then it stops falling (also a brilliantly simple level control scheme). Thus under normal conditions there will always be bubbles in the return line to the tank, which serves to enable the air to separate from the oil as well as to radiate some heat. And as has been pointed out in another thread, the pressure at any point in the supply side of the system - or return side, for that matter - is set by the flow resistance existing there. Pressure really only matters for the plain rod bearings, which require enough pressure somewhere upstream to ensure flow to replace the oil squished out every rotation of the crankshaft, otherwise the surfaces touch (and no, the oil pressure doesn't keep the surfaces apart, the hydrodynamic wedge inside the journal does). In the roller main bearings, the roller and race surfaces normally touch - well, there is the film strength to keep them microscopically apart - and the oil serves to reduce the friction and temperature associated with that - thus they just need to be kept wet (but not submerged, because that would cause too much viscous drag and froth etc.) and the heat get rejected somewhere. The top end is basically the same story as the mains.[/quote]

That hydrodynamic wedge is why I harp about people cranking a new motor until oil pressure comes up. Just like a car tire on a wet highway surface speed is needed to keep the two surfaces from contact. According to formulas from some old sae papers that speed is around 1500-2000 rpm to keep a Norton lifter from intimate contact with the cam. It depends on the particular oil, the spring rate and surface finish of the parts. [along with contact area, radius and a lot of other things]
A newly machined part has no surface protection until the part has been used. Pouring oil over the part doesn't do it. The metals and other additives in the oil get burnished or baked onto the metal part when it is in operation which will then provide some protection. Until that has happened the surfaces are prone to scuffing from metal to metal contact. That is why cam manufacturers tell you to bring the engine up to speed as soon as it is started. The speed creates a hydrodynamic wedge that keeps the parts from touching.
The lube that comes with a cam is primarily to provide protection for a few revolutions so you can get the engine assembled and started. Some cams use a deposited layer such a parkerizing which provides protection for a little longer.
The same thing applies to any non-roller bearing in the engine. Jim

Again Thanks!!!

kartiste said:

lynxnsu said:

...the speed of the feedline matters of course as well or you get cavitation ,but that is nothing to do here

Click to expand...

Just a point about cavitation and the Cdo oil pump: being a gear pump, it's generically a "positive displacement" pump, meaning it simply moves whatever appears at its entrance - air or oil - by increments of volume, not by increasing the energy of the flow, as in a centrifugal pump. Cavitation (defined as a reduction in fluid pressure below the vapor pressure of the fluid) is not relevant to the operation of a gear pump, and bubbles in the flow - supply or return - are not a result of cavitation, since the fluid pressure is above the vapor pressure of the oil at all times except possibly within the pump somewhere, but probably also even there - oil has a very low vapor pressure, so it takes a pretty good pressure drop to get under it.

Click to expand...

Are you saying positive displacement pumps are not affected by cavitation?