Lucas Mechanical PI System Model

Hello Mike,

I accept that there will be some leakage, as in the full-size version, and I will feed it back to the tank. I just drilled two weep holes on the trial version to give me an idea of how much leakage there would be.  I would like to reduce the quantity to around 1/10 of what it is, so reducing the clearance from a couple of 1/100 to a couple of microns using similar techniques to my diesel injection systems.

Hello Minh,

The gear pump tests are just to measure and adjust the injector opening pressures. The shuttle metering pump will give a sharp rise and fall in pressure and the system fuel pressure is intended to be around twice the injector opening pressure as in the full-size Lucas system.

The next step is how to reduce the clearances. I made another rotor and lapped the outside which gave a diameter close to 5.99 mm. I now need to purchase a suitable reamer to give a finished bore of maybe 5.97mm so I can lap the final 0.02 mm to give 5.99 mm.

Having drilled the ports I then ran the 1.95 mm drill through the bore again to remove the burrs followed by the 1.95 mm reamer. The 1.95 mm and 1.96 mm pin gauges both pass through so I need to start lapping in the direction of 1.98 mm. This is always a little problematic as you have to lap out 0.01 mm before the next size pin gauge will enter.

I now needed to look at the nominal 6mm bore between the rotor and the sleeve. I took a trial length of 12 mm silver steel and drilled it 3 mm then 5.9 mm. My dial calliper registered between 5.90 and 5.94 mm so as expected the hole was oversize and oval.

I then reamed it to 5.95 mm using the floating reamer holder. The 5.96 mm pin gauge would not enter but the 6 mm barrel lap would pass through.

I then started lapping, using 5 micron paste, and the 5.96 mm would quickly enter. On with the lapping 

Picking this one up again. I had some problems with tapered bores on the nominal 5.95 bore. Unusually the entry was on size and the exit was 0.03 – 0.04 mm oversize. I wanted to make a longer brass lap to finish the outside of the rotor but found that the bore was tapered  After a number of experiments I am still not sure of the root cause. I thought that I had a fairly good understanding of reaming from my diesel injection work. Another 5.95 mm reamer from a different source and adjusting the spring loading on the floating reamer holder seemed to help.

Having, hopefully, solved the reaming problems I started on a new 6mm external lap, rotor and sleeve.

The parts were made much as before.

I am not sure if it is better to ream the bores before or after drilling the ports?  For the sleeve bore I tried running the reamer through again after the ports had been drilled. The rotor bore was reamed after the ports were drilled as I had done for the diesel injection pumps.

The rotor and the sleeve were then lapped with 5 micron  diamond paste. The rotor was finished to 5.98 mm along the length as well as I could measure with a micrometre. The sleeve was lapped out until the 5.97 mm pin gauge would pass through and then step by step until the rotor would just slide in.

Next lap the rotor bore to fit the shuttle parts.

I'm glad to see your progress 

But this episode has me question a few things ....
1)  We all know that a Drill-Bit can NOT drill a Round nor Straight Hole !!!!
2)  a Reamer can't correct the Errors from #1
3)  if a Straight Round Hole is needed - you will have to Bore it, with either a Boring Tool or a D-Bit.
3)  a Reamer Needs to Cut => 0.2-0.5mm. for a Hole around 6mm. - so why do you only Cut 0.05mm. ?

Or that is what I would have answered anybody asking me on how to do it .... have I got something wrong ?

Best wishes

Per