Injected Diesel 56cc 2 Stroke, Will it ever work?"

[Lloyd-ss]

This side conversation might be getting a bit esoteric, but that's ok.
An art, vs a science, in a more technical application.
I originally heard that: art vs science, from a sales rep for military style round connectors. His statement was that soldering was an art, and crimping was a science, and it made perfectly good sense to me in that application. Two broad classifications. Call it an art, a craft, a skill, whatever you want. With the crimping, with proper calibrated tools, most people, with the slightest bit of technical ability, can make a proper crimp joint on a connector pin. But soldering, no, that is an art (or a skill, call it whatever you want), that even with hours of training, some people cannot do. Like making a beautiful tig weld. I will call it an art if it requires a certain ability to make very subtle instantaneous decisions and adjustments in a process to achieve the desired perfect result.

I know that the 2 broad classifications is an over simplification, but it is just to make the point that even with lots of training, there are some things that many people just cannot master. In fact, much of the work that is done on this forum might be considered to be art more than a science. But it is a continuum, with lots of opinions to go along with it.

Just my thoughts on the subject.

Lloyd

 

[Lloyd-ss]

The valve spring seat pockets are now machined Even though there is a one inch difference in the height of the injector and valve stems, there will be a single rocker arm shaft for all 3 rockers. The injector will have its rocker beam above the shaft and the valves will have their rocker beams below the shaft. Their will be only two pillars to support the shaft, mimicking the Detroit Diesel layout. Because the strokes are so short, the radii from the shaft to the roller tips contacting the stem tips will be satisfactory.

A general 2d layout sketch of the entire engine is forth-coming.

 

[ajoeiam]

The valve spring seat pockets are now machined Even though there is a one inch difference in the height of the injector and valve stems, there will be a single rocker arm shaft for all 3 rockers. The injector will have its rocker beam above the shaft and the valves will have their rocker beams below the shaft. Their will be only two pillars to support the shaft, mimicking the Detroit Diesel layout. Because the strokes are so short, the radii from the shaft to the roller tips contacting the stem tips will be satisfactory.

A general 2d layout sketch of the entire engine is forth-coming.

View attachment 146553

How did you make/design the springs? (very curious)

 

[GreenTwin]

That is some nice valve and spring work !

.

 

[Lloyd-ss]

How did you make/design the springs? (very curious)

That is some nice valve and spring work !

.

Total transparency here guys. I mentioned this path earlier, but it bears repeating. The work on the roots blower and the injector was 95% me, and the effort to get both functioning properly, just about beat me into the ground. So I decided to not get burnt out on the project by helping myself with a few purchased parts. I feel like the model should be like those huge dinosaur skeletons in the museums where the fake bones are a different color, LOL.

So, the spring for the injector is left over from a drum brake rebuild kit. The pair of exhaust valves with springs, retainers and keepers were from rebuild kits for 50cc motor bikes (shipped from North Carolina). Bought on eekBay for a ridiculously low price. Much less than one hour of a psychotherapy session that was the other alternative, ha ha.

Lloyd

 

[Lloyd-ss]

Here is a sketch of the 3 rockers that will be on a common shaft with thin-wall bronze bushings. Each rocker will have a half inch of length on the shaft, which should offer plenty of stability. The two small circles at the top of each valve stem show the max up and down position of each valve.

And a photo of the head with the rocker shaft and pillars. There is enough space around the edge of the head to fit seven more-or-less evenly spaced head bolts.

 

[ajoeiam]

Total transparency here guys. I mentioned this path earlier, but it bears repeating. The work on the roots blower and the injector was 95% me, and the effort to get both functioning properly, just about beat me into the ground. So I decided to not get burnt out on the project by helping myself with a few purchased parts. I feel like the model should be like those huge dinosaur skeletons in the museums where the fake bones are a different color, LOL.

So, the spring for the injector is left over from a drum brake rebuild kit. The pair of exhaust valves with springs, retainers and keepers were from rebuild kits for 50cc motor bikes (shipped from North Carolina). Bought on eekBay for a ridiculously low price. Much less than one hour of a psychotherapy session that was the other alternative, ha ha.

Lloyd

Aw shucks - - - - and I thought I could learn how to make such wonderful looking items - - - - bummer (fake pouting - - - - lol).

Hopefully not to frustrating being asked - - - - I can understand the need to finally get something done.

Sadly - - - - all too often!

 

[Lloyd-ss]

Aw shucks - - - - and I thought I could learn how to make such wonderful looking items - - - - bummer (fake pouting - - - - lol).

Hopefully not to frustrating being asked - - - - I can understand the need to finally get something done.

Sadly - - - - all too often!

Joe,
I wind springs when I "have to." Not too bad if you have the right dia spring wire on hand. With a hand crank on the lathe spindle, and a length of wire and a piece of round stock clamped into the chuck together, just keep a lot of tension on the wire by pulling straight out away from the lathe with a pair of pliers, and turning the hand crank. You can pretty much eye-ball the coil spacing. Cut off the excess wire and crappy coils from the spring. Closing the ends is the hardest part. With a little butane torch or similar, heat the end coil exactly where you want it to bend. Just the tiniest spot of red. Bend it quickly to close the coil. Flatten the end coil using the side of the bench grinder wheel. Use water to kill the heat.

 

[Lloyd-ss]

The rockers are roughed in and now need roller tips.

 

[Lloyd-ss]

Valve Train

A long absence from the forum. Spring and summer means lots of outside work to be done, but I do manage to steal a few hours for the model diesel every now and then.

I have the head, unit injector, valves, rockers, cam, lifters, and push rods all mocked up onto a solid aluminum block for testing. It is hooked to a variable speed motor for running at speed.

Here are some pics. A video of it in action is coming shortly
Thanks all, Lloyd

Click on the pics if you wish to enlarge them.

 

[Lloyd-ss]

Here it is in action. It is powered by the $100 usd sewing machine motor I bought a while back for making test set-ups. It does take some torque to lift both of the exhaust valves at the same time.
When the injector is actually pumping fuel, even more torque will be needed on the camshaft.
Lloyd


There is audio in the video, but it is very quiet at the beginning.

 

[Steamchick]

Hi Lloyd, Very Interesting! very few model engineers test with rigs (and modify if required?) before further assembly. "We" use the finished model as a test rig... not always the sensible route to success... so I congratulate you on your extra effort!
I hope the results made you smile?
I am smiling for you!
Just an aside, I like your idea of purchasing springs etc. as they are so highly refined by the specialist makers, for performance and longevity, that it is almost a shame to "spoil" a really good model for the sake of "purism". I strongly believe a good engineer selects when to make and when to "buy" - to include all the advantages that specialist supplier manufactured parts can offer. (I buy castings, springs, nuts and bolts, etc... as I am not a purist!).
Working for a car maker, (engine design dept.) it was common practice to use the specialists as appropriate (Valves, springs, oil-pump rotors, collets, camshafts, etc.) and "home make" (in plant that is) the unique elements for the engine (heads, etc. with unique assembly, features such as valve angles, porting, etc.)
K2.

 

[Lloyd-ss]

Hi Lloyd, Very Interesting! very few model engineers test with rigs (and modify if required?) before further assembly. "We" use the finished model as a test rig... not always the sensible route to success... so I congratulate you on your extra effort!
I hope the results made you smile?
I am smiling for you!
Just an aside, I like your idea of purchasing springs etc. as they are so highly refined by the specialist makers, for performance and longevity, that it is almost a shame to "spoil" a really good model for the sake of "purism". I strongly believe a good engineer selects when to make and when to "buy" - to include all the advantages that specialist supplier manufactured parts can offer. (I buy castings, springs, nuts and bolts, etc... as I am not a purist!).
Working for a car maker, (engine design dept.) it was common practice to use the specialists as appropriate (Valves, springs, oil-pump rotors, collets, camshafts, etc.) and "home make" (in plant that is) the unique elements for the engine (heads, etc. with unique assembly, features such as valve angles, porting, etc.)
K2.

Steam,
Yes, I agree on all points!

First, yes a very big smile on my face. I love the sound in the video when it is spinning at 2,000 rpm. I was not expecting that adrenaline-pumping sound!

When building complex devices, testing at various subassembly stages is vital. At least in my opinion.
I dabble in electronics and as something goes together on the breadboard, taking the time to do testing.... as feasible..... makes the trouble-shooting process more manageable. Once it is all built, finding a hidden error is a major pain. It is good knowing that "this subbasembly is good, so the problem must be over here in this later sub."

And the old make-buy dilemma. I know where you are coming from on that one! As the old saying goes, you can't beat a man at his own game. They have already done all the development and testing and have the process figured out. Yes, you "can make it", but should you make it? Sometimes if your in-house facilities are low on work it might make sense to do it yourself, so long as you don't get bitten in the butt by being over-optimistic. It only takes one or 2 bites to learn your lesson. I know, LOL!!

There seems to be nothing wrong (to me) in using off the shelf parts that already work well. Using a few purchased part is nothing close to just doing the final assembly on a "kit." I almost got burned out getting the unit injector to work like I wanted. Buying a few of the difficult parts if they are available not only saves you from burning up a few hours, it also helps from getting burned out on the project and just quitting.
That is where the big smile comes from. When you hit those mile-stones and it really works, that puts the bounce in your step.

BTW, I have heard that some people find these home videos like this test set-up to be boring? Can you believe that? Me neither, ha ha.
Lloyd

 

[minh-thanh]

@Lloyd-ss .
I like the way you build your engine.
Thanks for sharing !
Please update ....

 

[peterl95124]

Here it is in action. It is powered by the $100 usd sewing machine motor I bought a while back for making test set-ups. It does take some torque to lift both of the exhaust valves at the same time.
When the injector is actually pumping fuel, even more torque will be needed on the camshaft.
Lloyd

Nice!!!

I am building a Find Hansen diesel, and have been wanting to deviate from his design to put the valves and injector in a triangle rather than a straight line to be less crowded, and also wanting to make a combined fuel pump and fuel injector to eliminate the very high pressure piping and fittings between them, it looks like you're already doing both of these things, great, I no longer have to think of these features as experimental !

 

[Lloyd-ss]

POOP. INJECTOR FAILURE.

I was refining the fuel delivery to the unit injector and it was going well, although, slowly.

A gravity feed diesel fuel tank made from copper tubing, with a 1/4" supply to the injector and a 1/8" return. Because the injector pump has a single inlet/outlet hole, the return spillage was rather frothy and caused the incoming fuel to be the same. That made the fuel delivery inconsistent. I ended up putting a tiny check valve in both the inlet and outlet tubes right at the connection to the pump cylinder. That made a big difference in the fuel delivery and everything was working splendidly. There was just enough leakage past the check valves to feed the fuel well without overloading the piston and its cam. But a weak link showed up and both check valves escaped their retainers and ended up inside the pump cylinder. One was aluminum and the other was Delrin, so it appears no damage occurred to the hardened cylinder and piston. But quite disappointing.


Here is the copper gravity-feed diesel tank, with the supply and return lines tot eh unit injector.
The check valves for each line are/were located right where they mate with the injector body.



Here is a picture looking down into the pump cylinder, with the check valves
and a retainer visible in the bottom. The speed control on the motor was being operated by hand so I was able to immediately stop the catastrophe.
But we have all dealt with worse.

 

[a41capt]

This is a truly fascinating bit of work and experimentation. I enjoy your failures (and the learning experiences they promote) as much as the triumphs!

Thank you for sharing,
John W

 

[Nerd1000]

Rotten luck with the injector.

How was the spillage mixing with air? Injector needs to be bled or is it frothing up in the tank?

 

[Roger B]

What fuel are you using for your tests? Is it put under vacuum when the injection plunger returns? I had a problem with petrol (gasolene) vapourising during the return stroke with a port controlled injection pump. This showed up as bubbles in the fuel inlet pipe. This was resolved by pressurising the fuel to around 0.8bar (10psi) as in full size mechanical petrol injection systems.

 

[Lloyd-ss]

Rotten luck with the injector.

How was the spillage mixing with air? Injector needs to be bled or is it frothing up in the tank?

By design, there is a lot of flow in and out of the tank and resultant turbulence, etc, that, shall we say disturbs the fuel in the tank. Maybe froth isn't the correct term, but with the back and forth flow and the vibration from the valve train, it is obvious that the fuel is not coming from a placid pool. The fuel is standard automotive diesel.

I have avoided pressurizing the fuel supply, but in the end, it might be necessary. I don't know. The entire set-up is very touchy with so many variables during the optimization process. Things like stroke length, starting point and ending point of the stroke, check valve design and cracking force, excess volume, the outlet pressure check valve to the injectors, and more. Changing and testing the variables is time consuming and they are all inter-related, and it is difficult to tell what change is causing what result.

Here is a sketch of the pump portion of the unit injector.
I hope it helps clarify the operation of the pump. It is one of many standard designs and probably has a unique name, but I don't know. I have heard "Mercedes" used but that might not be correct.

The piston moves up and down at a constant stroke length. There is an angular notch ground across approx 60 degrees of rotation of the piston. The notch is connected to the pressure chamber by a hole drilled thru the central axis of the piston. Volume control is via rotation of the piston.

In the sketch the piston is at the top of the stroke and the pressure chamber is filled with fuel. As the piston moves down, excess fuel exits via the spillage check valve. Pressurization does not start until the piston reaches the bottom of the inlet port. Pressure quickly builds as fuel leakages are overcome. When the pressure is high enough, the pressure check valve pops to send fuel to the injector. Depending on where the notch in the piston is rotated to, excess fuel in the pressure chamber exits back into the inlet port and back to the tank via the spillage check valve. At fuel shut-down, the piston is rotated such that the fuel exits via the notch before the bottom of the inlet port is covered. There fore, no pressure builds at all. The 2 check valves in the fuel supply only help direct the flow of the fuel in and out of the pressure chamber, and the fuel tank, but they have nothing to do with how the actual injection hi-pressure is developed.

The design is super touchy and I am not sure I made the correct choice in using this design, but when it works, it works well. But each stage in the engine building process seems to change something and a tweak is needed to get it working properly again. Unfortunately, "which tweak?" is often a mystery. It definitely tries my patience and is more of a psychological challenge than anything else. Probably a little unhealthy, LOL.