scavenge pump flow rate

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All I can say is that whatever the figure it is enough to ensure that I only need close one tap to ensure that oil goes through coolerrather than back to tank . it was a discovery made by accident and lead to amuch neater installationthan the previous one of using two taps. And it has worked pretty well since the late 1970s. For it to work properly i wouldhave thought morethan 0.33 wouldbe necessary butin the wordsofan old song you never can tell
 

texasSlick

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If that fiqure of pump rpm is 45% engine rpm is correct, it changes the math considerably.

Instead of 60 oz., the scavenge side of the pump will deliver 60 x 0.45 = 27 oz./min. Then, the figure of 1 L/min (33.8 oz.) at 3000 engine rpm is impossible as the pressure side of the pump has shorter gears than the scavenge side. So something is amiss.

The ratio of pressure side capacity to scavenge side capacity should be exactly the same as the ratio of length of pressure side gears to scavenge side length. Can you measure and report the length of gears on both sides?

Slick
 

Richard Tool

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If that fiqure of pump rpm is 45% engine rpm is correct, it changes the math considerably.

Instead of 60 oz., the scavenge side of the pump will deliver 60 x 0.45 = 27 oz./min. Then, the figure of 1 L/min (33.8 oz.) at 3000 engine rpm is impossible as the pressure side of the pump has shorter gears than the scavenge side. So something is amiss.

The ratio of pressure side capacity to scavenge side capacity should be exactly the same as the ratio of length of pressure side gears to scavenge side length. Can you measure and report the length of gears on both sides?

Slick
IIRC the axial dimension of the scavenge gears is double the feed dimension- but my memory ain’t what it used to be so please correct me if needed.
 

texasSlick

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IIRC the axial dimension of the scavenge gears is double the feed dimension- but my memory ain’t what it used to be so please correct me if needed.

Double is what I remember the Norton Manual states.
Which shows something is indeed amiss regarding the flow rates as measured by the OP, flow rates as stated by the source I quoted, and the pump rpm vs the engine rpm.

I would like to get to the bottom of this.

Slick
 

texasSlick

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Just found this from the NOC (https://www.nortonownersclub.org/node/10626) post dated 02/04/2020:
Which states a 6 start pump delivers 25.5 gallons/hour at 6500 rpm.. That works out to be 1.61 L/min. At 3000 rpm we can expect 1.61 x 3000 / 6500 = 0.74 L/min.

Slick

@Tom Vachon:
Was your measurement of pump rpm vs engine rpm done with a 3 start or 6 start pump?

If you are working with a 3 start pump, then I think the numbers can be resolved.
 
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Just found this from the NOC (https://www.nortonownersclub.org/node/10626) post dated 02/04/2020:
Which states a 6 start pump delivers 25.5 gallons/hour at 6500 rpm.. That works out to be 1.61 L/min. At 3000 rpm we can expect 1.61 x 3000 / 6500 = 0.74 L/min.

Slick

@Tom Vachon:
Was your measurement of pump rpm vs engine rpm done with a 3 start or 6 start pump?

If you are working with a 3 start pump, then I think the numbers can be resolved.
Sorry, i dont know what u mean by 6 start or 3 start? pls explain.
btw, i ‘ll be supplying more data and pic of a graph hopefully tomorrow. But would like to know what 6 start and 3 start means
before i try to make sense of what im seeing. Tom
 
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Sorry, i dont know what u mean by 6 start or 3 start? pls explain.
There are 2 sets of scroll gears for the pump and crank, 1 set gives 3 start and a later set gives 6 start and this later set doubles the pump revs per rev of the crank. The change was pre Commando and timed to the change from rocker feed being from the return side at low pressure to the feedside feed at big end pressure. To stop over oiling of the top end the rocker shafts were rotated to reduce the flow at the same time as the change from 3 start to 6 start. As you have a pump out of a Commando the scroll gear set is 6 start.
 

Mart UK

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Double is what I remember the Norton Manual states.
Which shows something is indeed amiss regarding the flow rates as measured by the OP, flow rates as stated by the source I quoted, and the pump rpm vs the engine rpm.

I would like to get to the bottom of this.

Slick
It seems to work fine though. I too would like to understand it, but am relaxed it's stood the test of time. If I can help it, I'm not looking to add to my list of things to worry about:)
 

Richard Tool

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The feed side measures .250”
Scavenge side measures .405” +/-
so not quite double .
As the diameters are equal and both turn at the same rate via a common shaft this assures that scavenge side volume will always exceed the feed side volume.
B73F9DB1-AF95-4E72-8EA5-59A769CE10EE.jpeg

9A2208A0-8957-4BFA-A375-A2B177E5F211.jpeg

ABF72108-2DD7-40AC-ADBB-ABC0EC3B8E9B.jpeg

Regardless of pressure differential between feed/scavenge I believe what Tom is trying to do is quantify the difference in performance of the worn pump vs. the same pump freshly lapped. Very interested in the results and I applaud his efforts so thanks to Tom for posting and sharing this .
Cheers - RT
 
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texasSlick

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25.5 Imperial gallons/hr, 115.92 litres/hr, 1.932 l/min.

(According to John Hudson, it was: "26 gallons per hour at 6,000 RPM")

Thanks, LAB, for that subtle update: ..... of course it is Imperial gallons. Also, thanks for the 6 start/ 3 start picture.

Then, if we use Hudson's data, the flow at 3000 rpm (which is most likely crankshaft rpm) computes to 0.97 L/min. This is close enough to the data source I quoted earlier of 1.0 L/min. Since the scavenge side of the pump has gear length twice that of the pressure side, the scavenge flow rate is expected to be 2 x 0.97 = 1.94 L/min..
UPDATE: Using Richard Tool's measured gear length data, the expected scavenge flow rate is 1.00 x 0.405/0.250 = 1.62 L/min, or if we are not picky, 0.97 x 0.405/0.250 = 1.57 L/min

@TomVachon
If you wish to compare your results to that of Lab's sources, you will have to account for the relative rpm difference between the crankshaft and the pump shaft. In this regard, it does not matter which set of drive gears you have, just so you relate your measured flow to a calculated crankshaft rpm relative to your drill (pumpshaft) rpm.

Slick
 
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BERT

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Thanks for YOUR data. Yea, looks like theyre in the same ballpark anyway.
But dont know what pressure or temp, etc. And i think its not linear since % leakage probably varies with rpm. Meanwhile i just spent a good hour sanding the body face down on sandpaper on glass. Trying (assembling and disassembling) it over and over trying to get it good without overshooting it. Finally got it and im quitting for tonite. Plan to clean thoroughly tomorrow, oil and try again on my test stand. Hoping for significantly better than 8 oz per min at 400 rpm. I’ll let u know as soon as i have some more data.
Thanks for your input and interest.
Tom, as you are lapping the pump body, remember to also check the length of the non drive spindle to make sure it doesn't end up a few thou too long for the assembly.
 
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The feed side measures .250”
Scavenge side measures .405” +/-
so not quite double .
As the diameters are equal and both turn at the same rate via a common shaft this assures that scavenge side volume will always exceed the feed side volume.
View attachment 83321
View attachment 83322
View attachment 83323
Regardless of pressure differential between feed/scavenge I believe what Tom is trying to do is quantify the difference in performance of the worn pump vs. the same pump freshly lapped. Very interested in the results and I applaud his efforts so thanks to Tom for posting and sharing this .
Cheers - RT
Mine measure exactly the same. TomV
 
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Tom, as you are lapping the pump body, remember to also check the length of the non drive spindle to make sure it doesn't end up a few thou too long for the assembly.
Great point and i did and i have about 0.004” clearance. TomV
 

NickZ

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Bench testd my 71 Commandos scavenge pump and with my drill running it at 400 rpm, it puts out 8 oz per minute at room temp with 20W50 oil. Its set up to mimick its function in the bike lifting the sump oil about 6”” to the pump and pumping it up about a foot to the top of the oil tank.
As best i can measure the axial clearance of gear to endplate is about 0.002 to 0.0025”. This is too much but i wanted to get a baseline to see how much i can improve it by lapping the body of the pump as the shop manual describes.
Anybody else have any flow rate info on the scavenge pump??
I tested 3 pumps at approx 2600 rpm (engine), 70*F 20W50, Sump flow rates were between 0.37 - 0.53 L/min. These tests were mainly for comparison. Not exact bike setup.
For details, see:

I think it is post #24
 
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