Model Diesel: 32mm bore, 38mm stroke, indirect injection

[EyeTrip]

EDM I'm looking into this myself

 

[Nerd1000]

I don't often have time to do machine work during the week, but the 3d printer is at my apartment so I can sometimes print a part. I just did the rear gear cover, from carbon fiber filled nylon 6.

I think this is the best part I've ever printed from this material, must have finally got the settings just right. The cover is also the housing for the centrifugal governor which accounts for the funky shape.

 

[Nerd1000]

After some trials, tribulations and a redesign, here are the rockers fitted along with the pushrods.

I like this system of rocker pedestals and trunnions, it turned out very nicely and I'd certainly use it again. I would however beef up the middle of the rocker a bit, I managed to squash one in the vise and had to remake it.

It's not so obvious in the photo, but I also made the copper head gasket. It seals well, and at present the only obvious leak is the valves. I'll have to re-lap them. Even with a substantial leak from the valves the compression pressure is considerable, the engine is very difficult to turn past TDC by hand. This of course raises the question of how I'm going to start it, as it is also a struggle for my electric drill.

In terms of major assemblies I only have the injection pump and governor left to go. Plus a few odds and ends. Very exciting and I can't wait for the next time I've got some free time for machining

 

[The Ignoble Troll]

After some trials, tribulations and a redesign, here are the rockers fitted along with the pushrods.View attachment 156112
I like this system of rocker pedestals and trunnions, it turned out very nicely and I'd certainly use it again. I would however beef up the middle of the rocker a bit, I managed to squash one in the vise and had to remake it.

It's not so obvious in the photo, but I also made the copper head gasket. It seals well, and at present the only obvious leak is the valves. I'll have to re-lap them. Even with a substantial leak from the valves the compression pressure is considerable, the engine is very difficult to turn past TDC by hand. This of course raises the question of how I'm going to start it, as it is also a struggle for my electric drill.

In terms of major assemblies I only have the injection pump and governor left to go. Plus a few odds and ends. Very exciting and I can't wait for the next time I've got some free time for machining

Buy a bigger drill?

But seriously:
Can you set up a movable shim on your exaust valve to be a decompression set up. Then once the flywheel has some speed you could drop the valve?

 

[The Ignoble Troll]

After some trials, tribulations and a redesign, here are the rockers fitted along with the pushrods.View attachment 156112
I like this system of rocker pedestals and trunnions, it turned out very nicely and I'd certainly use it again. I would however beef up the middle of the rocker a bit, I managed to squash one in the vise and had to remake it.

It's not so obvious in the photo, but I also made the copper head gasket. It seals well, and at present the only obvious leak is the valves. I'll have to re-lap them. Even with a substantial leak from the valves the compression pressure is considerable, the engine is very difficult to turn past TDC by hand. This of course raises the question of how I'm going to start it, as it is also a struggle for my electric drill.

In terms of major assemblies I only have the injection pump and governor left to go. Plus a few odds and ends. Very exciting and I can't wait for the next time I've got some free time for machining

Buy a bigger drill?

Can you set up a movable shim on your exaust valve to be a decompression valve to let you spool it up freely?

 

[minh-thanh]

View attachment 156112


It's not so obvious in the photo, but I also made the copper head gasket. It seals well, and at present the only obvious leak is the valves. I'll have to re-lap them. Even with a substantial leak from the valves the compression pressure is considerable, the engine is very difficult to turn past TDC by hand. This of course raises the question of how I'm going to start it, as it is also a struggle for my electric drill.

"the engine is very difficult to turn past TDC by hand"
Only when you build will you know how it is

 

[Nerd1000]

I spent today doing some odds and ends parts of the engine project. The crankcase has been drilled and tapped for mounting brackets so I can bolt it to a base, I made a new washer for the timing gears, put the nylon cap on the front end of the cam, and made a starter dog and driver. After re-lapping the valves yet again, they are finally sealing well enough that the rings are now the main leak. An aside here, they still leaked despite the lapping compound having made a dull ring all round the seat. I ended up checking by putting a thin coat of prussian blue on the valves and turning them in their seats. I also sealed the two crankcase halves together with RTV.

Having done all this, temptation took over and i put the head on and cranked the engine with a more powerful drill in low gear. There was a noticeable smell of burnt oil, and so, optimistic, I sprayed some 'start ya bastard' into the intake port and tried again... a large cloud of white smoke shot out of the exhaust as the valve opened. We've achieved compression ignition! After a few more tries the engine stopped firing after getting a squirt, so I put a bit of oil down the intake and it fired on the next attempt. Seems like we just need the rings to bed in (or to crank faster than 550 rpm). I pulled the head, and here's what I saw on top of the piston:

As you can see, there's a burn mark, where the oil on the piston crown got scorched. It's right under the pre-chamber passage, which would be consistent with ignition happening in the pre-chamber and shooting hot gases out towards the piston.

This is all very promising, I'm pretty confident that if we can fire from cold on starter fluid we can probably get it running on diesel. However, the starter dog is a problem.

The setscrew securing it to the crankshaft chewed up the flat on the shaft pretty badly. I need a better solution, currently thinking of changing to a clamp style design that grips the shaft by closing up. And of course, we need the injection pump so it can run for more than one revolution.

 

[Roger B]

I use a split clamp for my starting dog. I doesn't damage the crankshaft so much and will act as a mechanical fuse if something jams whilst you are cranking with a drill.
Congratulations on the first puffs of smoke

 

[Nerd1000]

I'm making some progress on the injection pump. The body of the pump and the barrel are done and the barrel has been lapped, though I may give it one more go with finer abrasive. I also made a plunger. Both plunger and barrel are of silver steel and hardened by quenching in oil. Worked well for the barrel, but it backfired with the plunger! I tried lapping it today and discovered that it warped from the quench, so I couldn't get it to clean up all the way around before it went undersized.

I'm part way through making a replacement. I think I will forego the heat treatment this time.

 

[Roger B]

I'm making some progress on the injection pump. The body of the pump and the barrel are done and the barrel has been lapped, though I may give it one more go with finer abrasive. I also made a plunger. Both plunger and barrel are of silver steel and hardened by quenching in oil. Worked well for the barrel, but it backfired with the plunger! I tried lapping it today and discovered that it warped from the quench, so I couldn't get it to clean up all the way around before it went undersized.

I'm part way through making a replacement. I think I will forego the heat treatment this time.

I think it would be better to harden the plunger while it is round and then grind the helix otherwise the unequal sections will distort when hardening. I moved from hardened and lapped silver steel to commercial pin gauges for my plungers.

 

[Lloyd-ss]

................... snip

Having done all this, temptation took over and i put the head on and cranked the engine with a more powerful drill in low gear. There was a noticeable smell of burnt oil, and so, optimistic, I sprayed some 'start ya bastard' into the intake port and tried again... a large cloud of white smoke shot out of the exhaust as the valve opened. We've achieved compression ignition! .

Nerd, I missed the engine firing party, but want to add my congratulations! I brought an apple pie, too.
Your tenacity is admirable and contagious. Well Done !!
Lloyd

 

[The Ignoble Troll]

My understanding of helix plungers is that they need to be rotated(or the pump body) to align the helix for a given discharge volume.

What are you guys, who use helix plungers, using to rotate the plungers?

 

[Nerd1000]

My understanding of helix plungers is that they need to be rotated(or the pump body) to align the helix for a given discharge volume.

What are you guys, who use helix plungers, using to rotate the plungers?

My plunger passes through the middle of a control collar that has a slot cut in it. The plunger is cross drilled for a pin that rides in the slot.

 

[Lloyd-ss]

My understanding of helix plungers is that they need to be rotated(or the pump body) to align the helix for a given discharge volume.

What are you guys, who use helix plungers, using to rotate the plungers?

@The Ignoble Troll
The GM plungers had a flat ground along the outboard end to make it D shaped. Then a small gear with a matching D hole thru it allowed the plunger to move up and down thru the gear. A rack went cross-axis, and off the center axis, thru the injector body and engaged the gear. Pulling the rack in and out rotated the plunger.

One problem with all of the helix arrangements is that they are easy to twist when not under load. But when they are pumping and under load for the down-stroke, it is like shifting a trans with dogs but no synchronizers: it will only rotate when the load is off for that half cycle. The Detroit Diesels had a hydraulic assist in their governors to move the racks in and out in unison even when in that loaded half of the pump cycle. The ramp angle of the helix can really affect its sensitivity where (in a worst case) any slop in the linkages can cause different amounts of hysteresis and thus inconsistent injection amounts. I find it amazing that they work at all, LOL.

 

[The Ignoble Troll]

Thanks guys!

 

[Nerd1000]

I decided to take Roger's advice and grind the grooves in after heat treatment. Here's my setup, I just put a dremel cut-off wheel and arbor in my milling collet.

Worked pretty well. I covered my ways with rags before grinding, the abrasive dust is not good for them. My mill only does 1100 rpm at full speed which is really too slow for a grinding wheel. Still made a lot of heat, I had to squirt coolant on it between passes to avoid taking the temper out of the part!

This part lapped in much better. Interesting observation, it was actually lobed with 3 high points. I suspect the low points lined up with the chuck jaws on the lathe when I was turning it. I've got it cleaned up slightly oversized, I'm not totally happy with the surface finish in the barrel (grit was too coarse) so I think I'll finish by lapping the barrel bigger to match.

 

[peterl95124]

Having done all this, temptation took over and i put the head on and cranked the engine with a more powerful drill in low gear. There was a noticeable smell of burnt oil, and so, optimistic, I sprayed some 'start ya bastard' into the intake port and tried again... a large cloud of white smoke shot out of the exhaust as the valve opened. We've achieved compression ignition!

I used some "start ya bastard" on my Merlin V12, that was the only time it ever backfired, and given the large volume of the intake manifold, it was quite a backfire resembling a gun shot more than an engine pop, not using it any more :-( !!!

anyway, following this thread with interest as I have a Hansen A-frame Diesel in the works but have not yet attempted the fuel pump and injector...

 

[Steamchick]

Peter, White smoke means we either elected a new pope, or unburnt fuel has been vaporised.
WELL DONE!
K2

 

[minh-thanh]

Hola dónde puedo encontrar los planos de ese inyector

You go to a place where English is the standard, you should use English, Don't make it your own place !!!!
I got a PM from you but I'm too lazy to translate it
Imagine, many others learn the way you do, then this place will be a trash can
Note: 90% of my comments on the forum are completely using google translate .

 

[ruben]

Hola donde puedo encontrar los planos del piston

Hello, where can I find the piston plans?