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

[Lloyd-ss]

Hi Lloyd, I really admire your work!
I have a question for what might seem a potential issue, unless -of course - is not the complete design; which I believe is the case.
The link between cylinder liner and crank case, as seen in the picture, looks not that rigid and prone to cyclic bending during engine run. Will you add more reinforcements?
The nice part of any project is that only the owner has the final image of how it will look like. And it's a mix between design concept and methods to reach there.

I agree with you. Those 2 plates are 5mm 6061-T6 aluminum, but I think they will flex during operation. To fix that, there will be a cover plate with a flange machined into it such that screws will come thru the existing angled plates, into the cover plate, and lock the structure securely together. That plate will pilot over the snout of the crankshaft and support the bearings for the gear train. The gear train will have the main gear on the crankshaft, then up to an idler gear, then up thru another gear on the end of the camshaft on the right, then across to the left to the balance shaft, then again to the left to drive the roots blower at 2x overdrive. The location of the camshaft and the balance shaft will be a mirror image of each other, but will rotate in opposite directions. The camshaft and balance shaft will both have eccentric counterweights. The timing of the cam and balance shaft weights will be such that when the crankshaft counterweights are at the very bottom, the cam and balance shaft counterweights will be at the top. The crankshaft, camshaft, and balance shaft all rotate at the speed. That is how the 1-71 Detroit Diesel manual describes it, so I think it will work.
Thanks, Lloyd

 

[Lloyd-ss]

(snip and high-lights by Lloyd)................................
The nice part of any project is that only the owner has the final image of how it will look like. And it's a mix between design concept and methods to reach there.

I was re-reading some posts and looked at your last sentence again in post #260. That is so true! When we have limitations in the tools and materials in our home shops, sometimes the "methods" play a much stronger role in the project. And sometimes the "method" is getting a tool to do something that it was never designed to do. Excellent observation.
Lloyd

 

[Lloyd-ss]

July 6, 2024
Getting closer and closer. I have added the odd shaped piece that is the crank cover and gear train plate. It is machined on the back side such that it has a flange on all edges to ( @NapierDeltic ) improve the rigidity of the assembly.
No gears are on it yet. I have set the head in place, along with the exh rockers to give a feel for what it will look like. The big ugly block on the left will become the cam shaft bearing block and also the lifter support. And on the right in a similar fashion will be the roots blower. The compartment at the bottom will house the pumps, etc.
Right now the beast is 11 kilos and 0.43 meters tall. I am glad I didn't have a serious weight or size goal. Just like budgets, they are a noble goal that is seldom met.

 

[The Ignoble Troll]

That is a serious looking piece of machinery

 

[Lloyd-ss]

That is a serious looking piece of machinery

Where I was working, "robust design," was a euphemism for the literal translation of "too damn heavy to lift."

 

[petertha]

But the .250" wall was a different animal. Not as pretty in the I.D. and there was a faint witness line from the ERW process, but the I.D measured right on the money. This time I started by honing the I.D. to 38mm, which meant removing only a few thou. I honed out nicely and the new 38mm rings fit nicely.

What do you use for honing tools in this diameter range?

 

[Lloyd-ss]

What do you use for honing tools in this diameter range?

It's a brake cylinder hone I bought years ago at an autoparts store. It has one set of fine stones and will close down to about 19mm. I just chucked the liner in the lathe, protected everything as best I could with a bunch of rags, chucked the hone in the tailstock and manually moved the tailstock back and forth, while running at 300rpm. I used plenty of oil from a squirt can and stopped periodically to clean out the resulting slurry and mess. I clamped some stop blocks on the lathe bed to control how much the stones exited the ends of the bore, maybe 6mm. The stones are 28mm long.

It actually worked better than I expected. Moving the entire tailstock back and forth by hand, gently hitting the wooden stop blocks, made the process easy to control. I deburred the scavenging ports in the liner before I started honing. The large burrs probably would have messed up the hone.

If the finish is too smooth, some cloth can be used to build up a wooden dowel to the I.D. size of the liner, and them some 150 grit silicon carbide sandpaper taped around the cloth. Turn the lathe speed down and stroke the dowel and sandpaper just a few strokes and it will quickly add a nice cross hatch if that is your preference.

Lloyd

 

[Nerd1000]

It's a brake cylinder hone I bought years ago at an autoparts store. It has one set of fine stones and will close down to about 19mm. I just chucked the liner in the lathe, protected everything as best I could with a bunch of rags, chucked the hone in the tailstock and manually moved the tailstock back and forth, while running at 300rpm. I used plenty of oil from a squirt can and stopped periodically to clean out the resulting slurry and mess. I clamped some stop blocks on the lathe bed to control how much the stones exited the ends of the bore, maybe 6mm. The stones are 28mm long.

It actually worked better than I expected. Moving the entire tailstock back and forth by hand, gently hitting the wooden stop blocks, made the process easy to control. I deburred the scavenging ports in the liner before I started honing. The large burrs probably would have messed up the hone.

If the finish is too smooth, some cloth can be used to build up a wooden dowel to the I.D. size of the liner, and them some 150 grit silicon carbide sandpaper taped around the cloth. Turn the lathe speed down and stroke the dowel and sandpaper just a few strokes and it will quickly add a nice cross hatch if that is your preference.

Lloyd

View attachment 157914

I use a similar hone, only two stones though. I just run it in a hand drill, prefer to keep the abrasive grit away from the lathe.

 

[Lloyd-ss]

I use a similar hone, only two stones though. I just run it in a hand drill, prefer to keep the abrasive grit away from the lathe.

I am not trying to make excuses, but with the progressive lenses in my glasses, visually checking for vertical, level, perpendicular, etc., is usually a guess. I just don't trust my perception of those characteristics. Using a hand drill never results in a hole that is perpendicular to the entry surface. Better safe than sorry for me, but I am glad that you can still trust your eyes.
Lloyd

 

[Nerd1000]

I am not trying to make excuses, but with the progressive lenses in my glasses, visually checking for vertical, level, perpendicular, etc., is usually a guess. I just don't trust my perception of those characteristics. Using a hand drill never results in a hole that is perpendicular to the entry surface. Better safe than sorry for me, but I am glad that you can still trust your eyes.
Lloyd

The stones pivot so they should follow the hole. Not that I'd trust them to do that if I was actually trying to finish the bore to size! But with the hone you are just trying to remove the tool marks from boring and get a crosshatched finish, so as long as you just do that it should be ok.

 

[The Ignoble Troll]

How self centering are two vs three stones? I always wondered if they were prone to *flipping about* in the bore?

 

[Lloyd-ss]

Camshaft and Lifter Assembly

This is the "ugly block" from post #263. It now houses the camshaft with ball bearings at each end, with the end of the shaft protruding out the front of the block to accept the combination drive gear and balance weight.It will be driven by the non-existent gear train that will be powered from the crankshaft snout that is visible at teh bottom right of picture.

One thing to note about the cam and lifter assy is that (in addition to needing to be polished up a bit) the 2 outer cams are both for the exhaust valve valves and are plain solid lifters. The load on the cam from the exh valves is fairly light. But the center cam is for the unit injector and delivers the force to pressurize and inject the fuel and puts a very heavy load on the cam train. Therefore, the center lifter is a roller lifter and rides in a slotted guide bushing to help the lifter track properly and handle the offset loads.

I need to make new longer push rods, or taller exh valve lifters, but that is pretty easy.

The as-built dimensions for the gear train can now be established and the 6 gears selected and ordered.

Thanks for taking a look and commenting.
Lloyd

 

[Lloyd-ss]

How self centering are two vs three stones? I always wondered if they were prone to *flipping about* in the bore?

I believe both styles are pretty forgiving so long as you DON'T run the stones out either end of the bore, and keep it fairly centered and straight. As they come out the end, they will tend to bottle mouth the bore, and you can't fix that. That is why I prefer the lathe with stop-blocks method.

I have used these flexible hone, glaze breakers, bottle brush hones, (many names) but they work better for tubes rather than shallow bores. They will bottle mouth a bore very quickly. They are very aggressive because they have complete contact in the bore. They come in different diameters and grits but are inexpensive if you find a good source.

Funny story. I was using one of these in a 4" diameter to break the glaze on an engine re-ring job when I was about 19. First time doing something like that and not much experience. It was a blazing hot humid summer and I was doing this outside. The bottle brush left a beautiful finish and I washed it all down with soapy water, admired my work, and went inside to have lunch. When I came back outside I about pooped my shorts! The humidity and the squeaky-clean cast iron had made a layer of RUST in the bores in that half hour. Darn. I quickly re-did the honing, washed, dried, and oiled. No problem, but I learned my lesson.

 

[Nerd1000]

The 'bee's knees' would be a proper rigid hone, like they use on full sized engines and hydraulic cylinders. They can even improve the roundness and straightness of the bore, something the spring loaded ones have no hope of doing. Don't know where you'd start as far as getting one in the right diameter however.

I've always had trouble with my hone wanting to pop out of the bottom of the cylinder like Lloyd describes. A right pain, but so far I've gotten away without bellmouthing a cylinder liner!

 

[The Ignoble Troll]

Thank you both, that's very helpful.

 

[Roger B]

I use Acrolaps:

https://www.acrolaps.com/

The needle laps with 1 micron diamond paste for the injector components and the barrel laps with 40 micron diamond paste for cylinder liners.

 

[Roger B]

Lapping the cylinder liner for my Junkers CLM:

 

[Steamchick]

The following welding failure demo was a good watch too! VERY informative!
K2

K2

 

[The Ignoble Troll]

From the looks of your cylinder liner, you plan to have cooling?

Forgive me if it was mentioned but are you fitting a coolant pump?

Will you eventually add a demo load like a generator to the engine, or will it be a very large tabletop proof of concept engine?

 

[Lloyd-ss]

I use Acrolaps:

https://www.acrolaps.com/

The needle laps with 1 micron diamond paste for the injector components and the barrel laps with 40 micron diamond paste for cylinder liners.

Those laps look high quality like they would control roundness, straightness, all that good stuff. I don't know if you mentioned in detail how the diameter adjustment works and how you load the lap with grit. That video really emphasizes the difference between quality single-purpose built tools and having to make-do with what is on hand.