Request - Injector designs

[Roger B]

Ruben sent me a message asking for details of my latest needle style injector and an early design of helix pump. I will post them directly in this thread in case anyone else is interested.

First the new needle injector:

This was designed to overcome some of the manufacturing problems with the first series of needle injectors, especially the deep hole in the brass nozzle and the long needle. There are still some challenge with this design, a deep 1mm hole that must intersect with the 1.2mm fuel entry and keeping the body and the nozzle concentric.



The body is a piece of 10mm square black bar. The top end was drilled and tapped M8 for the spring adjusting screw. This thread also allows the body to be mounted on an M8 threaded mandrel for turning the other end.

The end of the body was turned to 8mm and the fuel inlet was made and silver soldered on using a short 1mm steel pin to keep it in place. The long 1mm fuel passage was drilled to the correct depth and the hole in the fuel inlet was extended to meet it. The body was fitted back on the mandrel and centered to turn the 7mm locating land and to cut the M8 x 0.5 thread.

The bore for the needle takes some practice. I made a number of trials with different speeds, different drill sizes and various reaming techniques to obtain an accurate and parallel bore with no bell mouthing. The required diameter depends on how the needle is made. I used 1.5mm diameter silver steel which when hardened and lapped ends up around 1.48mm so that was my target diameter. The diameter after reaming needs to be around 1.46mm to allow for lapping. I use a 1.35mm drill and a 1.45mm reamer in a floating reamer holder. The bore was lapped with an Acro needle lap and 1 micron diamond paste. The bores are checked with a set of pin gauges from 1.45 to 1.50mm.

The tip of the needle was turned to 60° and the required length was turned down to 1mm. The needle was then hardened and the working length was lapped to 1.48mm with a homemade brass lap and 1 micron diamond paste.

The nozzle was turned to size externally and parted off. It was then mounted in a 5mm collet and drilled 1.5mm to the required depth. The 90° seating was cut with a homemade D bit. I am using a 60° needle and a 90° seating to get a line contact seating. The 0.2 mm orifice was drilled using a 0.2 mm twist drill fixed into a 1.5mm diameter brass rod.



The nozzle was then fixed to the body with the clamping nut (the 7mm diameter locating land in the nut should be bored so it is accurate and parallel) and needle was lapped to the seating once again with one micron diamond paste. Finally the needle was cut to length and it all went into the ultrasonic bath for cleaning.

I am not a draughtman, I use CAD as an electronic back of an envelope but hopefully all the relevant dimensions are there. I have uploaded the .DWG as well as a .JPG The scallops out of the sides of the body are not essential, they were clearance for the injector fixing nuts on my four stroke diesel.

 

[ruben]

Ruben sent me a message asking for details of my latest needle style injector and an early design of helix pump. I will post them directly in this thread in case anyone else is interested.

First the new needle injector:

This was designed to overcome some of the manufacturing problems with the first series of needle injectors, especially the deep hole in the brass nozzle and the long needle. There are still some challenge with this design, a deep 1mm hole that must intersect with the 1.2mm fuel entry and keeping the body and the nozzle concentric.



The body is a piece of 10mm square black bar. The top end was drilled and tapped M8 for the spring adjusting screw. This thread also allows the body to be mounted on an M8 threaded mandrel for turning the other end.

The end of the body was turned to 8mm and the fuel inlet was made and silver soldered on using a short 1mm steel pin to keep it in place. The long 1mm fuel passage was drilled to the correct depth and the hole in the fuel inlet was extended to meet it. The body was fitted back on the mandrel and centered to turn the 7mm locating land and to cut the M8 x 0.5 thread.

The bore for the needle takes some practice. I made a number of trials with different speeds, different drill sizes and various reaming techniques to obtain an accurate and parallel bore with no bell mouthing. The required diameter depends on how the needle is made. I used 1.5mm diameter silver steel which when hardened and lapped ends up around 1.48mm so that was my target diameter. The diameter after reaming needs to be around 1.46mm to allow for lapping. I use a 1.35mm drill and a 1.45mm reamer in a floating reamer holder. The bore was lapped with an Acro needle lap and 1 micron diamond paste. The bores are checked with a set of pin gauges from 1.45 to 1.50mm.

The tip of the needle was turned to 60° and the required length was turned down to 1mm. The needle was then hardened and the working length was lapped to 1.48mm with a homemade brass lap and 1 micron diamond paste.

The nozzle was turned to size externally and parted off. It was then mounted in a 5mm collet and drilled 1.5mm to the required depth. The 90° seating was cut with a homemade D bit. I am using a 60° needle and a 90° seating to get a line contact seating. The 0.2 mm orifice was drilled using a 0.2 mm twist drill fixed into a 1.5mm diameter brass rod.



The nozzle was then fixed to the body with the clamping nut (the 7mm diameter locating land in the nut should be bored so it is accurate and parallel) and needle was lapped to the seating once again with one micron diamond paste. Finally the needle was cut to length and it all went into the ultrasonic bath for cleaning.

I am not a draughtman, I use CAD as an electronic back of an envelope but hopefully all the relevant dimensions are there. I have uploaded the .DWG as well as a .JPG The scallops out of the sides of the body are not essential, they were clearance for the injector fixing nuts on my four stroke diesel.View attachment 159898

Thank you for the plans and help

 

[Roger B]

Helix controlled injection pump:

My first injection pump was used for manifold injection on a petrol engine so a variable stroke controlled by a wedge was adequate. For the diesel trials a more defined start of injection was required so I decided to go for a helix controlled jerk pump.



I had already resolved lapping the pump bore in the variable stroke pump using a similar technique to that used for the injector. The first plungers were made from hardened and lapped 2mm diameter silver steel but after a problem with a tri lobar piece I now use commercial hardened and lapped pin gauges. As the silver steel ended up at around 1.98mm this is the bore size I have been using.

The body is once again made from 10mm square black bar. The bore axis is not in the centre of the bar so it needs to be set up in the 4 jaw independent chuck. The 5mm diameter for the control gear is turned first, followed by the pump bore. Initially I made it all 1.98mm but for later versions the first 6mm was opened out to 2.2mm diameter. The bore was drilled 1.85 mm and reamed 1.95 mm using a floating reamer holder. It was not lapped until the 1mm diameter inlet port was drilled.

The body was then turned round and held in a collet by the 5 mm diameter section so the delivery valve seating could be cut with a 4.5 mm end mill and the M5 x 0.5 thread for delivery valve body tapped. I initially made the seating by tapping a 3 mm ss ball with a hammer and brass drift but I found I got better results using a 3mm diamond charged ball lap after the pump bore had been lapped. The delivery valve bodies were initially made from modified commercial unions but later they were turned from brass bar.

The plunger is made from a 1.98mm diameter pin gauge. The helix is cut to a 4mm pitch in the lathe using a Proxxon mini tool with a grinding disc. I cut both ends of the pin gauge when the lathe is set up for this to have a spare if necessary. The grinder needs to be set at 32° and I cut to a depth of 0.5mm in 0.05mm steps. The plunger is then cut to length with the Proxxon grinder and the end is annealed to allow an M2 thread to be cut.

The control gear is 20T MOD 0.5 meshing with a length of MOD 0.5 rack. There is a rectangular recess cut in the face of the gear to engage with a rectangular piece threaded and Loctited onto the end of the plunger. The gear is wide enough so that it stays engaged for the full 3mm stroke.

I am not a draughtman, I use CAD as an electronic back of an envelope but hopefully all the relevant dimensions are there. I have uploaded the drawing as .DWG and .JPG. There are also a couple additional pictures.