Building
the
Hydraulic Injection Pump And Injector
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25 August 2017:
Getting started on the injector parts, I made what I -think- will work for a pintle (teensy poppet valve).
 
     The little collet and the drill rod blank.                                Grinding the small diameter pin for the head.
 
Center punching for the head bore.                                               The (hopefully) finished pintle.
All of this took the whole morning.  After I was done, I quit for the day with a bit of eyestrain.

Since the chuck in my lathe will not close down smaller than 0.100", I had to make a funky collet.  I used an end of 1/2" bar stock and drilled it to accept the 0.069" drill rod.  I then slotted it so it would squeeze in the chuck to hold the workpiece.  This worked pretty well.

The first thing I did was to use the Dremel "toolpost grinder" to grind a smaller diameter on the end of the rod for the head to slip over.  A piece of 1/8" drill rod was used for the valve head.  I made some executive decisions on some of the dimensions to be able to actually build the parts.

After facing the 1/8" drill rod with the toolpost grinder, I used a centering punch in the tailstock to mash a center point in the rod.  Then it was drilled with a #55 drill to fit the smaller diameter on the stem.

Once the head was semi-pressed onto the end of the stem, the protruding smaller diameter was peined over to lock it into place.  

Lastly, the spring retainer clip groove was ground in the stem and the stem was cut to length.

In the injector, I am relying on clearance between the stem and the injector body to allow fuel to flow to the tip.  Also, the clearance will allow the tiny poppet to float to find it's best seat.

At least, that's how I think it will work.
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26 August 2017:
The lower part of the injector body is done.

Injector lower body with pintle.
I didn't get as much done today as I thought I would.  While hogging the diameter of the lower injector body, the primary cog belt in the lathe broke.  While replacing it, I found a couple of issues relating to that part of the lathe that had to be addressed.  The part did get done.

Because the pintle was a relatively tight fit in the body, I used some fine alumina lapping compound to get the fit better and take a first shot at lapping the valve.  Working in these small dimensions is not easy.  First, the runout in the lathe chuck is about 0.0005".  For normal work in larger fractions of an inch, this fades into insignificance.  For dimensions in a few thousandths, it has to be contended with.  I hope I can chase this to a point where the parts will fit well enough to work.

I hope to finish the injector tomorrow.
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29 August 2017:
I've finished the injector and started testing it.
   
Itsy-bitsy retainer washer.                                                                Funky first effort spring.                                                                        Under test.        
I took a wild guess as to the strength of the cracking pressure spring and have it quite a bit too strong.  I can peg the gauge and it doesn't do a thing.  Tomorrow, some changes will be made and further tests done.  I think the valves in my pump need a little more work, as the pump bleeds down to a couple hundred psi after a few seconds.

Making these itty-bitty parts takes more time than making the bigger ones.


Oh, yes.  My friend Denis Basson from Australia brought to my attention that I am not properly describing the stem thingy.  It is NOT a pintle thingy but is a poppet valve thingy, a totally different animal.  I will be much better at the terminolgy after I get farther along in my apprenticeship. :-)
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30 August 2017:
After lapping the injector poppet for a couple of hours, I finally got it to sort-of spray but it still needs more work.  Then, the bolt that holds the banjo fitting on the injector broke.  I'm calling it a day.

El Drato!
The banjo bolt is an 8-32 machine screw.  Since I have to drill it for a fuel passage, it was weakened to the point that, after several tightenings for bleeding and testing, it finally gave-up.  Tomorrow, I think I will change it to a 10-32 to give more strength.
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31 August 2017:
Today, I upped the size of the banjo bolt to 10-32, re-drilled the injector top and tapped it, Drilled the top bolt axially with a #55 drill and then used the same size drill to drill the radial hole to meet it.  Drilled out the banjo for clearance.  Made two new copper sealing washers and put it back together.  Leaked like a sieve.

After lapping washers and generally fiddling around with it, it still leaked just enough so I couldn't get to anywhere near the cracking pressure I was shooting for.  Finally, I just kept tightening the bolt with less and less leakage until it started twisting off.

I quit for the day.  Maybe I need to go with something like 1/4-28.  It will look sorta klunky but will be the same size as the banjo bolt on the pump.  
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Boy!  This is fun!

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Since 23 August 2017