oil pressuer on commandos

The commando design does not require high oil pressure. True or False? Oil goes from the pump through the crank and to the big end bearings. It also feeds the rockers and I suspect it feeds the cam in some way. The mains are splash feed and so are the cam and followers. Oil draining down the pushrod tubes also lubes the cams. The rods have holes in the outside faces to splash the main bearings. So long as there is a constant oil flow, where is the need for high pressure? [ racing engines are excluded from this scenario but I suspect same applies ]
The old Chev Blue flame engine had pressure feed mains and dippers to feed the big ends. I understand that Chev engine ran at 15psi.
Dereck

There is nil need for pressure in sane pubic use but to assist gravity oil tank flow to feed spinning crank fast enough to keep up with rod oil sling out. Norton only issued early Cdo oil gauges for about 12 weeks til flooded with freaked out owners seeing zero pressure at hwy speeds a fast service notes send out stating solution was to remove the gauges immediately and carry on. The oil hole in rods hit at the inside seam of piston pin on down stroke as can't hit piston on up stroke and are ancient manufacture error bodge that should be blocked off forever more. Some Commando said to develop 50 PSI at hwy speed which may not be as good as one would think as may be just extra work-heat load on engine that don't need that much to last a long time at oil surfing rpms. So real question is do we immediately shut down to rebuild pump to crank in those engine that barely bump needle off peg or just forgetaboutit?

hobot said:

Norton only issued early Cdo oil gauges for about 12 weeks til flooded with freaked out owners seeing zero pressure at hwy speeds a fast service notes send out stating solution was to remove the gauges immediately and carry on. ?

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Where the blazes did this info come from ??
Show us where Commandos EVER had oil pressure gauges ?
Is your latest ploy to fabricate stories if you don't actually know the answer ?

Nortons fitted oil pressure gauges for the early dommie twins, circa 1949 - to 1952 or early 53.
The readings weren't particularly useful, sometimes showing quite low readings, even if the engine carried on regardless.
And if the oil level got too low and the engine suffered, the gauge didn't allow owners to notice this in time to help anyway.
So the gauge was deleted for the 1953 model year, and the ritual checking of the oil tank level was encouraged.
Norton owners having got over the fear of oil pressure loss in these new fangled twin cylinder thingies....

The pressure relief valve in Norton engines limits the pressure available to about 40 psi or 50 psi, give or take a lot,
so clearly don't need high pressure for the big ends.

The oil squirt holes in the conrods were said to be a mistaken solution to a piston design problem,
and once that piston problem had been solved, the squirt holes are not actually needed.

I'm sure others will add to this.
As you mention though, plenty of engines throughout automotive history had been designed to run on just splash lube,
with no pressure at all, just splash and trickles feeding things...

Perhaps the auto engines which had splash feed to the big ends did not rev very fast ? I'm under the impression that there must always be sufficient pressure between the shells and the journal to prevent metal to metal contact even when the motor is very hot. On my triumph billet crank, I hard chromed the journals and use Morris Cooper copper lead shells. After the most strenuous races I could never push in the pressure indicator button.

10 psi per 1000 rpm for shell bearings used to be a fairly good bench mark, you could live with a 50 psi cut off at high rpms maybe.
No wonder every shell I have seen from a Commando shows copper.

Rohan said:

hobot said:

Norton only issued early Cdo oil gauges for about 12 weeks til flooded with freaked out owners seeing zero pressure at hwy speeds a fast service notes send out stating solution was to remove the gauges immediately and carry on. ?

Click to expand...

Where the blazes did this info come from ??
Show us where Commandos EVER had oil pressure gauges ?
Is your latest ploy to fabricate stories if you don't actually know the answer ?

Nortons fitted oil pressure gauges for the early dommie twins, circa 1949 - to 1952 or early 53.
The readings weren't particularly useful, sometimes showing quite low readings, even if the engine carried on regardless.
And if the oil level got too low and the engine suffered, the gauge didn't allow owners to notice this in time to help anyway.
So the gauge was deleted for the 1953 model year, and the ritual checking of the oil tank level was encouraged.
Norton owners having got over the fear of oil pressure loss in these new fangled twin cylinder thingies....

The pressure relief valve in Norton engines limits the pressure available to about 40 psi or 50 psi, give or take a lot,
so clearly don't need high pressure for the big ends.

The oil squirt holes in the conrods were said to be a mistaken solution to a piston design problem,
and once that piston problem had been solved, the squirt holes are not actually needed.

I'm sure others will add to this.
As you mention though, plenty of engines throughout automotive history had been designed to run on just splash lube,
with no pressure at all, just splash and trickles feeding things...

Click to expand...

I brought this subject up because we were getting carried away with it on another topic. Lets forget about oil pressure gauges and look at just the oil pressure requirements of this engine and why we should or should not be too concerned about low oil pressure.

acotrel said:

Perhaps the auto engines which had splash feed to the big ends did not rev very fast ? I'm under the impression that there must always be sufficient pressure between the shells and the journal to prevent metal to metal contact even when the motor is very hot. On my triumph billet crank, I hard chromed the journals and use Morris Cooper copper lead shells. After the most strenuous races I could never push in the pressure indicator button.

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You are right. Those engines were pure luggers. I would think volume of flow would be more important than pressure. Lets face it, most of the oil is feed direct to the big ends, and the rotation of the crank would pump that oil up to rather a high pressure.
regards, Dereck

While its true that older splash lube vehicles mostly are low speeds, some big speeds were variously achieved by some of those engines...

The JPN Race Team commented that the oil just sluices through the big ends under race conditions ?

Its only the tiny 'hydraulic wedge' that forms in plain bearings that keeps the metal-to-metal contact from happening.
It doesn't need pressure to form - the pressure only supplies a constant feed of oil for it to happen.

Sorry, got carried away with oil gauges.
Some should check their facts BEFORE posting, however.
As has been said several times here before, we think...

Rohan said:

Its only the tiny 'hydraulic wedge' that forms in plain bearings that keeps the metal-to-metal contact from happening.
It doesn't need pressure to form - the pressure only supplies a constant feed of oil for it to happen.

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You need to bring the running clearance and oil viscosity into the equation, what is the Commando clearance and guess what small clearances can induce ?
Increased bearing and oil temperatures.

The clearance can be quite big, and the hydraulic wedge can still form.
The crank doesn't necessarily sit in the middle of all its clearances.

The combustion forces will of course try to drive it through the bottom of the sump...

Thanks guys, I think we were getting carried away on the other thread. I detected a bit of micky taking. Lets keep It clean and to the point. I like the good discussion that happens here.
Dereck

You won't be running a large clearance with low pressure.
I also doubt the stock oil pump could supply the volume based on that and the stock oiling system.
That would be running and side (bleed at the fillet) clearance, not to mention centrifugal forces at the shell.

There is a fancy word for the rod oscillating on the oil wedge but I forget the name, not an issue perhaps at sane revolutions.

There is also pressure induced scouring of the bearing surface but doubt that would happen on a Commando. (even with a minimal clearance)
Does the Commando crank run 0.001" per inch of journal ?

As well as my MK2 850 I have an unrestored 1951 Model 7 with less than 5000 miles from new. The tank top pressure guage shows around 40 psi most of the time, drops to around 20 when hot and idling and up to around 50 or so when cold and revving. The oil pump and engine design is pretty much the same so I don't see why the pressure in my MK 2 should be any different, not that I'm bothered really - it runs fine.

Norton knew not to fit pressure guage so early on warned diistrubutors and owners not to. I can not find a reference to factory ever selling them.

Oil pressure gauges on Commandos tell you very little
If you read the appropriate section in the Service Notes you'll find the opinion that use of such a gauge is somewhere between a bad and terrible idea. Not only is it useless once the motor is warmed up, because most of the oil from the pump is doing its work on the bottom end and only a trickle is coming up to the rockers. If it breaks, you might not notice until you've lost your top end. John S. Morris (jsm@mediaone.net) on NOC-L 28th. Aug 1997

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Mr Hudson Service Notes quote that relates back to oil coolers.
OIL PUMP: The oil pump takes a long time to wear out, but when the mains go it's a good idea to recondition it, as
all those bits of bearing have to go through the oil pump on their way to the tank-full instructions are given for this
operation in the workshop manual. Usually, you'll be glad to know, no new parts are required. If you have changed
the cover, the gasket, or the oil pump, check that the little conical black rubber on the pump is just compressed-it
shouldn't be possible to push the cover quite home by hand. If the cover is very proud, check that there aren't too
many shims on the oil pump under the black rubber. They tend to stick together and not get noticed. For the hat few
years these shims haven't been used, a paper washer between the oil pump and the crankcase is used instead. I have
heard of engines which ran quite successfully for a while without the rubber seal-because somebody forgot it (no it
wasn't me)-the theory is that the centrifugal whirling of the crankshaft forces oil out into the big ends and draws oil
into the crank. The output from the pump is enough to drench the hole so that air isn't drawn in. No oil goes to the
rocker gear, though, as this requires pressure.
Mention of pressure brings me to another point-the fitting of oil pressure gauges. On the Commando (and for similar
reasons. most bikes) an oil pressure gauge is more of a liability than an asset. It is of necessity, fitted on the feed side
where any failure of pipe or gauge is disastrous to engine and rider--it's touch and go whether the engine seizes
before or after you fall off with oil on the back wheel. On the Commando this failure could be caused by engine
vibration in the same way that early rocker pipes failed. (We're coming to that.) The other reason that a pressure
gauge isn't much good is really twofold. At high speeds and high oil temperatures the pressure can drop to nothing
on the gauge because the pump can hardly keep up with the rate the stuff is flying out of the big ends. The
centrifugal force can keep the pressure at the big ends above the danger point, so there's no real panic--but the gauge
would inspire you with horror. Then of course if you did seize an oil pump by the time you noticed that the pressure
had dropped the big ends would have gone (. . . through the hole in the crankcase, with average N.O.C. luck!). If you
want an interesting gauge to frighten yourself with, but, which is inherently safer and can give useful information, fit
an oil temperature gauge in the oil tank. Let me know what it reads as you change into top for the Mountain Mile on
both the fourth or fifth lap! The latest Racing Nortons (we can't call them J.P. Nortons any more as they've stopped
the bikes from smoking) had a new type of oil pump-I wonder if this is because the ordinary pump can't keep up?

hobot » Thu Nov 20, 2014 1:16 pm

Norton knew not to fit pressure guage so early on warned diistrubutors and owners not to. I can not find a reference to factory ever selling them.

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Norton "warned" distributors and owners not to fit oil pressure gauges you say?

I have owned five brand new Commandos and never got any warning about this.

Can you tell us where you got this information about Norton warning owners not to fit gauges?

link, name of book, magazine name and date, anything where you got this info, Hobot?

Good to know, thanks for the real world information.
I will put any wear at the shells down to numb nuts previous owners and lack of oil changes.

pev said:

As well as my MK2 850 I have an unrestored 1951 Model 7 with less than 5000 miles from new.The tank top pressure guage shows around 40 psi most of the time, drops to around 20 when hot and idling and up to around 50 or so when cold and revving. The oil pump and engine design is pretty much the same so I don't see why the pressure in my MK 2 should be any different, not that I'm bothered really - it runs fine.

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Time Warp said:

10 psi per 1000 rpm for shell bearings used to be a fairly good bench mark, you could live with a 50 psi cut off at high rpms maybe.
No wonder every shell I have seen from a Commando shows copper.

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Rohan covered the short term era of factory issued pressure gauges before Cdo's and why it can be a false safety feature. I left quotes of Service Notes also alerting against its use on Commandos. So question remains what do we do if a seeming good runner shows nil PSI at hi way speed, glance away till blows up or quit till rebuilt from crank up? I like needle dials so even have a disconnected Ammeter in Trixie to fill shell hole and look interesting when turned off. I love to see the fancy gauage installs and want my own plus more of others even if it confuses us no end. I'd tend to think up the oil grade thickness with temperature increase till needle is at least lifting off peg some.

Rohan said:

The crank doesn't necessarily sit in the middle of all its clearances.

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Actually the crank never sits in the middle in real world conditions and the "wedge" term refers to the geometry of the gap caused by the eccentricity of the shaft relative to the bearing.


Tim

I think one of the easiest checks is to take the filler off after any run you do and see that the oil returning to the take is satisfactory. I just checked mine a few minutes ago and gave it a rev, It nearly splashed oil out at me so much was being returned.
Dereck