Lucas Mechanical PI System Model

[Roger B]

I cleaned all the components in the ultrasonic bath and assembled the pump.

The gears were around 0.1mm too thick so I attempted to skim 0.1mm off both.

The first trial was unsuccessful      The pump was hard to prime and barely reached 0.8 bar. On checking again the gears were now around 0.1mm to narrow, I guess some bedding in took place.

Following an idea from Petertha’s gear pump thread I skimmed the surface of the body and gears with an end mill, attempting ~0.02mm cuts. The first trials were good, reaching 1 bar at 1000rpm but then the pump locked up     On dismantling there was a small piece of swarf caught in one of the teeth. I am not sure if this actually was the cause      The next trial exceeded 5 bar at higher speed, but the outlet hose blew off from the pump causing a bit of a mess      The pump them started jerking and jolting. The idler shaft had moved out of the pump body and was hitting the collet nut     Maybe this was the cause of the first lock up 

Time to regroup, Loctite the idler shaft in place, fit the lip seal and used solid pressure piping.

I have also ordered a different commercial fuel pump to try as well as some steel MOD 1 gears. The Delrin gears, like the cheap brass gears are not truly round, I guess due to the moulding process. The diameter over the teeth varies from 13.9 to 14mm.

[Kim]

I may not be your real target audience, Roger, but I do enjoy reading about what you're doing.  It's not something I'm likely to do, but I do find it fascinating!   

You are incredibly patient and methodical.  I learn a lot from reading your build threads!

Kim

[MJM460]

Hi Roger, please keep posting your incredible work.  I am another who reads every post and views all your pictures.  They form an excellent documentation of your work.

I am in awe of your skill at coaxing such accuracy out of small equipment that I don’t think was ever intended to achieve such precision.

Thank you,

MJM460

[Roger B]

Thank you both for your support 

The idler shaft was fixed in place, the lip seal was fitted and the outlet hose was clamped ready for the next trial. I reached 5 bar but had a fountain from the body – cover joint   

<a href="https://www.youtube.com/watch?v=vRMJimfOzCY" target="_blank">http://www.youtube.com/watch?v=vRMJimfOzCY</a>

On dismantling the pump again there was a very small ridge between the two milling passes      I polished this off on a sheet of 400 grit abrasive paper and tried again.

This time 7 bar was possible with only some dampness on the pump body, the lip seal seemed to stop leakage along the shaft.

<a href="https://www.youtube.com/watch?v=0mPQptSbY_M" target="_blank">http://www.youtube.com/watch?v=0mPQptSbY_M</a>

After the trial I took the cover off the pump again. The rubbing marks suggest that the clearance is close to zero.

I have also received my new gear pump and MOD 1 steel gears. I am not sure about following the instructions and gluing the brass adaptors in place     They are tapered from 4.4 to 4.5mm so there isn’t really much space for the adhesive   

[Admiral_dk]

Progress is progress - even if the road isn't straight   

Per              

[jcge]

Enjoying watching your progress Roger - and impressed that you've achieved 7 bar with such a tiny pump.

Please do keep posting !!

Regards,
John

[Roger B]

Thank you   

The gears as supplied have a 3.2mm bore (for 1/8” motor shafts?) so in needed to open them out to 4mm to suit my bearings and oil seals. They were held in a 14mm ER collet with a second gear at the other end of the collet to keep it balanced and concentric. The hole was bored out to ~3.8 mm using a Proxxon 3mm end mill as a boring tool (I made a holder for these when I made the CD carburettor) and then reamed 4mm. In days gone by I would probably just used a 4mm drill but now I am chasing every micron.  The bosses were then parted off. The finish is not very good but the gears will be skimmed again later in the build.

To test the new purchased pump I needed to build a simple test rig to hold a fuel tank, the pump and a support for the pressure gauge. A chance to drill big holes and not worry about the microns, +/- half a mm will do