Pandemic Oil Pump Insanity

Well, the Pandemic got to me. Looking for things to do, I reflected back on the old Flathead oil pump bugaboo. That is, Flatheads run hot, and cooling them off with oil would seem to be the most practical way open. I’ve used Sporty pumps successfully, but with caveats. the biggest was keeping the motor oil tight where the pump mounted.

Presently I’m using a prototype gearotor pump built by Bruce Argetsinger at Enfield racing on my personal 37ULH.

I’ve built 3 BTSV’s in the last few years for friends and customers and in each I used the modified rotor with 4 vanes instead of 2. This idea I frankly copied from Paul Freibus. From measurements I’ve made, this modification doubles the flow rate of the stock pump.

So, In the search for more oil to cool the motor via splash and Piston jets, we have

Sporty pump; 1 liter/minute at 1500 rpm (aka, battery powered drill in test jig)

Prototype gearotor pump; approx 1 liter/1.5minute? estimated. Balances pump output with stock scavenge pump capacity perfectly. Stock scavenge pump is about 87% capacity of Sporty pump, derived from actual size of pump gears.

4 vane rotor modification: pumps about 1 liter/4 minutes. (twice stock configuration)

Stock pump; 1 liter/8 minutes.

In building these motors the thoughts going through my head is that I wanted to do more oil flow, but at a reasonable cost, and maintain oil integrity. (keep it inside!) The pumps available from Sweden from Calas are a possiblilty, but quite expensive. I don’t begrudge their price, but It’s just beyond what most are willing to spend.

Also, the “K” Shelf combustion chamber heads from Finland are a big help in the heat battle in that their design moves a “Hot Spot” in the stock combustion chamber configuration that occurs right over the spot that Pistons fail from heat! So, far less oil is needed to keep the engine happy. Again, an expensive sell to resolve the longetivity issue with BTSV’s.

So, somewhere along the way, in the last couple of months, the thought occurs that maybe the stock vane pump could be modified for increased output. I did some research on vane type pumps and read a couple research papers on this type of pump and watched some videos on same. The end result is that although rare in motorcycle design, vane pumps are used extensively in the automotive field. One application is in automatic transmissions, obviously an application that requires reliability. Long story shorter, it struck me that these pumps are reliable, and that they respond well to basic mathematics in predicting their operation. I.E., more vanes, more volume, larger pump ports, more volume, larger cavity, linear increase in pump output.

Next in rereading Jim Casey’s text from some years ago on increasing the output of the stock pump, I came across a finding he had made in his testing. He had increased the size of the swept cavity (which is circular), to clean up some scoring, and he discovered an increase in that particular pump’s output. He speculated that the increase might have been do the cleanup cut, and left it at that. It was a small but measurable increase, along the order of 10%. This was enough to encourage to experiment.

AT LAST,

Here’s what I did. we did a lot of envelope calculations and then set up the Bridgeport.

I centered the pump cavity that the base of the rotor holding the vanes sits in. With an indicator chucked in the mill I indicated the offset cavity that the upper part of the rotor and vanes sweeps, noting from the indicator readings which direction the upper vane cavity was offset from the lower centering cavity. By marking the low and high points around the periphery of vane cavity, I determined which direction the upper cavity was offset from the lower. The aim was to determine the axis it was offset on, and then shifted the pump body until this offset axis lined up with the “Y” axis on my mill. To make this easier, I made a plug gauge that I could chuck in the mill and that would just fit into the lower part of the rotor cavity. This allowed me to loosen the pump jig and then rotate the pump about the mill spindle, while using marks made to locate the offset axis to align with the Mill’s “Y” axis. Here, I hate to admit, I just resorted to eyeball dead reckoning. Then making a couple of light passes with the boring bar to fine tune. I don’t have DRO on the mill so I set up a couple of dial indicators on the mill table so I could get an accurate read on actual table movement.

After that, it was just a matter of making a series of light cuts and recording my progress. I ended up doubling the swept volume of pump. This doubled the swept volume from .031 cu in to .0622cu in. I came up with this swept volume by computing the rotor’s volume and subtracting it from the new enlarged volume I had cut for the vane part of the cavity. Might not be true effective pump volume, but at least it was a number to use for comparison.

Bottom line was Measured modified pump out is now 1 liter/2 minutes!

Here’s a picture of my pump test jig. This is what’s left of a 46UL, my first BTSV. This is about all it’s good for now. The generator is just a “BoB weight, got a big chunk of steel inside to make the rig balance a little better :-)

Here’s a front view of the jig. The pump I picked up on Ebay just for testing purposes.

Here’s a rear view, The pump is driven by the number one cam shaft, cam removed. Pressed a 1/4” shaft into a drilled hole in the end of the shaft. Use a piece of gas line for a flexible coupling.

Another look, old coffee can for supply, Graduated cylinder to measure output.

So, the pump is one I picked up on ebay, just for this experiment. Nothing else was changed except that I blocked off the passage in the bottom of the pump rotor cavity that feeds to the bottom of the rotor for the centrifugal bypass valve. No use to deliberately throw away oil. The cam cover has had the passage to the mainshaft and the bypass passage blocked off for these tests.

Hopefully we’ll get around to making some volume vs pressure readings, mocking up a crankpin and piston jets. We’ll see…..