Author Topic: Fuel injection systems  (Read 22216 times)

Offline Roger B

  • Full Member
  • *****
  • Posts: 2965
Re: Fuel injection systems
« Reply #135 on: July 23, 2017, 11:20:32 AM »
The next step was to make the pump plunger and injector needle from 2mm and 1.5mm silver steel respectively. They were cut to length end the end of the pump plunger was threaded M2 before hardening. The pump plunger was lapped to 1.98mm diameter and the bearing surface of the needle was lapped to 1.48mm. The 50░ point was ground on the end of the needle as before.
When I tried to grind the shank of the needle down to 1mm diameter the finish was bad and the end snapped off  :( I tried again with the same result  :headscratch:
I looked back to see how I successfully made the first one and what was different.
The solution was as follows:
Harden ~20mm of the 1.5mm silver steel, don't cut to length yet.
Grind and polish the point.
Grind the shank to 1mm diameter with the lathe at 250rpm in reverse and the grinding wheel at ~5000rpm.
Reduce the depth of cut from 0.05mm to 0.025mm.
Feed in at the chuck end and cut towards the point.
Polish the shank.
Lap the bearing surface to 1.48mm and cut to length.
Best regards

Roger

Offline Roger B

  • Full Member
  • *****
  • Posts: 2965
Re: Fuel injection systems
« Reply #136 on: July 23, 2017, 12:33:00 PM »
Next I needed to change to milling mode to cut a screwdriver slot in the end of the nozzle so I could insert and remove it.
Whilst in this setup I cut a slot in the end of the operating plunger for a small ball race to run on the cam and cut the slot in the control gear for the piece that will turn the plunger and set the helix position.
I then went back to lathe mode and lapped the bores of the nozzle and pump body.
Next step put it all in the ultrasonic bath to remove the diamond paste residue.
Best regards

Roger

Offline Roger B

  • Full Member
  • *****
  • Posts: 2965
Re: Fuel injection systems
« Reply #137 on: August 06, 2017, 04:37:59 PM »
Having removed the contact breaker from the diesel engine I wanted to try the roller follower for the injection pump. The follower housing was held onto the crankcase with a small milling clamp and a steel ruler was used as a return spring. Unfortunately, but not unexpectedly (which is why I did the trial) it tended to run at an angle  ::)

I could either slot the plunger and add some sort of guide pin or key or change the design to a swinging link type follower  :headscratch:

<a href="http://www.youtube.com/watch?v=vjbnAhMha0Q" target="_blank">http://www.youtube.com/watch?v=vjbnAhMha0Q</a>
Best regards

Roger

Offline Brendon M

  • Full Member
  • ****
  • Posts: 132
  • Melbourne, Australia
Re: Fuel injection systems
« Reply #138 on: August 17, 2017, 09:00:57 AM »
I am up to date again Roger, keep at it :)

I found the procedure for forming the injector needle quite interesting.
(This signature intentionally left blank)

Offline Roger B

  • Full Member
  • *****
  • Posts: 2965
Re: Fuel injection systems
« Reply #139 on: September 03, 2017, 04:46:02 PM »
Thank you Brendon  :)

I made the union and nipple for the injector in the same way as before. This time I drilled the cone in the nozzle a little deeper and filed a flat on the nozzle to allow a couple more threads to engage.

I then ground the helix in the plunger and trimmed it to length, again as previously. The next bit was the tappet to go on the end of the plunger and transmit the rotation from the rack gear. This was sawn and filled from a piece of 4mm square silver steel so I can harden it. Having just purchased a set of edge finders I tried one out to centre the hole in the tappet.
Best regards

Roger

Offline Roger B

  • Full Member
  • *****
  • Posts: 2965
Re: Fuel injection systems
« Reply #140 on: September 03, 2017, 05:52:57 PM »
Problem  :( When I assembled the system it would not turn freely and jammed completely in a couple of places  :headscratch: After a series of checks I found that the bore was not concentric with the running surface for the rack gear by ~0.2mm. This was a result of drilling from the other end to give the delivery valve seat a better chance  ::)

OK, start yet another injector pump body with a different machining sequence. This time I turned the spigot for the rack gear and then drilled and reamed the bore. As a further, hopeful, refinement I started with the drill as far into the chuck as it would go and then moved it out in stages as the hole got deeper. The process was the optimum one from my experiment with the floating reamer holder.
Run at 2000rpm
Center drill deep enough to leave a countersink.
Drill 1.85mm
Ream 1.95mm with a controlled feed of 0.08mm per rev.
This seemed to work, the 1.96mm pin gauge passed straight through, the 1.97 mm barely entered. It was also concentric to better than 0.02mm and when reversed and mounted in a collet the run out of the bore was not detectable   :)
Best regards

Roger

Offline Admiral_dk

  • Full Member
  • ****
  • Posts: 664
  • S°ften - Denmark
Re: Fuel injection systems
« Reply #141 on: September 03, 2017, 09:13:20 PM »
Quite an improvement in precision  :ThumbsUp:

Hope that you will have much more "luck" with the next test  :)