Injected Diesel 56cc 2 Stroke, Will it ever work?"
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Hi Lloyd,
I was recently reading about old "Field Marshall" tractors, and I think they might be of interest as a source of ideas for your project. They use a single cylinder 2 stroke diesel, scavenged by crankcase compression like your engine will be.
First point regarding lubrication, they use oil fed to the bearings by a pump and drillings rather like a 4 stroke. A non return valve placed at the bottom of the crankcase allows excess oil to be forced out by crankcase compression and returned to the tank. If you used that strategy you wouldn't need to worry about seals on the big end.
Second point regards starting. They have a 'glow plug' in the form of a holder for a piece of smouldering paper that is screwed into the cylinder head. I think this would be a good system for our models, no need for electric heaters. Apparently the original paper for this purpose was soaked in potassium nitrate and would smoulder even in the absence of air, but modern owners say a piece of egg carton works just as well.
American readers may also be pleased to hear that the starting system on these tractors involves a blank shotgun shell... the shell is placed into a breech mounted to the cylinder and the engine rotated just past tdc. Then the firing pin is struck with a hammer. The ensuing explosion is directed into the cylinder where it kicks the engine over. I'm not sure if this system could be replicated on a model scale. Perhaps one could use a Ramset cartridge as the shell?
I was recently reading about old "Field Marshall" tractors, and I think they might be of interest as a source of ideas for your project. They use a single cylinder 2 stroke diesel, scavenged by crankcase compression like your engine will be.
First point regarding lubrication, they use oil fed to the bearings by a pump and drillings rather like a 4 stroke. A non return valve placed at the bottom of the crankcase allows excess oil to be forced out by crankcase compression and returned to the tank. If you used that strategy you wouldn't need to worry about seals on the big end.
Second point regards starting. They have a 'glow plug' in the form of a holder for a piece of smouldering paper that is screwed into the cylinder head. I think this would be a good system for our models, no need for electric heaters. Apparently the original paper for this purpose was soaked in potassium nitrate and would smoulder even in the absence of air, but modern owners say a piece of egg carton works just as well.
American readers may also be pleased to hear that the starting system on these tractors involves a blank shotgun shell... the shell is placed into a breech mounted to the cylinder and the engine rotated just past tdc. Then the firing pin is struck with a hammer. The ensuing explosion is directed into the cylinder where it kicks the engine over. I'm not sure if this system could be replicated on a model scale. Perhaps one could use a Ramset cartridge as the shell?
The Ruston-Hornsby single cylinder diesel in the grain elevator my father managed had the same paper glow plug, from memory, it was a tightly wrapped cylinder of paper about 1/4 to 5/16(6-8mm) in diameter x about 2.5 inches(63mm) long and was fitted in a plug that was drilled on the piston end for the 'glow plug' and screwed into the head.
For a model, has anyone ever used a gas lighter filling valve and a shot of butane gas to turn over an engine? With a glow plug it could ignite and give a suitable kick to start the engine?
I guess a 56 cc diesel really wants a decent starting handle or rope starter? A bicycle crank (6in?) is about the right size I guess?
The last car I had with a starting handle was a 2l, 4 cylinder petrol Volvo with fuel injection. 500cc per cylinder, 10.5:1 compression. C 1972. Of course, I have had many different motorcycles with kick-starters.
K2
I guess a 56 cc diesel really wants a decent starting handle or rope starter? A bicycle crank (6in?) is about the right size I guess?
The last car I had with a starting handle was a 2l, 4 cylinder petrol Volvo with fuel injection. 500cc per cylinder, 10.5:1 compression. C 1972. Of course, I have had many different motorcycles with kick-starters.
K2
For mine I was planning to rope start.
Roger B
Well-Known Member
I would suggest that you look at a suitable drive dog or free wheel so you can turn it over with an electric drill, especially in the early stages. This allows you to adjust settings whilst the engine is turning.
Thanks for the ideas, N1000. I am temporarily stalled on the project due to other obligations, but it is still sitting on it reserved workbench in the middle of the shop.
Actually, this model will have a roots blower, which is one of the few parts that is actually finished and working obediently. Post #99 of this thread shows it in operation filling up a 130 liter plastic trash bag. So, there will be no combustion air passing through the crank case.
You aren't trying to get me in trouble suggesting those ramset blanks for a starting trick, are you? Like using ether and a match for re-seating the bead of a tire on a rim? That process never worked for me, and a little scary, too.
A high torque battery powered drill and a little over-running clutch might be easier on the heart (mine). I have had my share of uh-ohs where it took me a minute before I got the courage to look at my hand. Luckily, the only bad one was at age 15, and it was just my pinky. Didn't need it anyway, LOL. But at my age now, all parts that are still working are too valuable to risk too much.
I was wondering about the possibility of using a 2 stroke engine glow plug. I have a couple of them and they have a 1/4-32 thread an I can squeeze it into the head. But I am not sure if they will stay incandescent (a bad thing??) after the engine is running. Don't they rely on methanol or nitro to stay glowing? Just wondering if they will cool down after the voltage is remove from them. Or maybe it doesn't matter, but it does sound a little bit like cheating. Or maybe its just using technology to your advantage??
Lloyd
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I think it is the methanol that keeps them glowing in glow motors. There are some special glow plugs made for running glow motors on petrol, though I don't know how they differ. Not cheating to use one in my opinion, you are just finding a engineering solution that works!
I wasn't being serious about the ramset starter, way too risky and there's no advantage over an electric start with a drill anyway. I just found the concept of starting your engine with an explosive charge amusing.
Well, I am glad you didn't present that starting method as a dare, LOL.
ajoeiam
Well-Known Member
We had one of those tractors. IIRC it was an unusually sized shell - - - 10 ga - - - but then that is from information some over 50 years ago and no way to corroborate it today. (source is dead for some 11 years already)
Off of dead center
I am finally off of dead center on this project and have a top end, including a unit injector working like I think it should. There are a half dozen injectors in the scrap box, but this one, with its synchronized low pressure pump seems pretty close. I had to turn the fuel volume up way too high to get a cloud that was easy to see for the video. There is an electric motor powering the cam shaft. All rocker tips are rollers. Only the injector lifter is a roller lifter, because the loading is quite significant. The 1/4" dia black plastic handle at the top is just an extension of the fuel control lever that twists the helical plunger. It will eventually be controlled by a governor.... I think.
I am finally off of dead center on this project and have a top end, including a unit injector working like I think it should. There are a half dozen injectors in the scrap box, but this one, with its synchronized low pressure pump seems pretty close. I had to turn the fuel volume up way too high to get a cloud that was easy to see for the video. There is an electric motor powering the cam shaft. All rocker tips are rollers. Only the injector lifter is a roller lifter, because the loading is quite significant. The 1/4" dia black plastic handle at the top is just an extension of the fuel control lever that twists the helical plunger. It will eventually be controlled by a governor.... I think.
PISTON
Now that I am past the injection (an almost fatal consumer of good shop time), I can have fun again. I made the piston last night, but it still needs ring grooves, after I have the rings. There are lots of 39mm rings available, and after the injector debacle, I will be buying the rings.
This is a two cycle engine of 39mm bore and 50.8mm stroke so the piston has to be very tall to seal the inlet ports when at TDC. Also, the wrist pin hole has to be very low in the piston so that the rod has clearance to the cylinder walls when the rod is at its most extreme angles. That also means a very long conn rod and the resulting balance problems.
But I am getting back into the fun.
I did have a near disaster when making the piston. I was using an internal 3 jaw to hold the piston inside the skirt to take the final clean-up cuts on the piston O.D. And of course, with the long cantilever, the tool grabbed and yanked the piston off the jaws. I was afraid to dig the piston out of the chip pan, but luckily, there was just enough cleanup material left to fix the boo-boo. One of the rings will have to be positioned over the one gouge that was a bit too deep.
Thinking back on this, many of the mishaps where I do, or almost do, ruin a part, are because of inadequate fixturing. Hmmmmm.
Now that I am past the injection (an almost fatal consumer of good shop time), I can have fun again. I made the piston last night, but it still needs ring grooves, after I have the rings. There are lots of 39mm rings available, and after the injector debacle, I will be buying the rings.
This is a two cycle engine of 39mm bore and 50.8mm stroke so the piston has to be very tall to seal the inlet ports when at TDC. Also, the wrist pin hole has to be very low in the piston so that the rod has clearance to the cylinder walls when the rod is at its most extreme angles. That also means a very long conn rod and the resulting balance problems.
But I am getting back into the fun.
I did have a near disaster when making the piston. I was using an internal 3 jaw to hold the piston inside the skirt to take the final clean-up cuts on the piston O.D. And of course, with the long cantilever, the tool grabbed and yanked the piston off the jaws. I was afraid to dig the piston out of the chip pan, but luckily, there was just enough cleanup material left to fix the boo-boo. One of the rings will have to be positioned over the one gouge that was a bit too deep.
Thinking back on this, many of the mishaps where I do, or almost do, ruin a part, are because of inadequate fixturing. Hmmmmm.
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Half the fun is making fixtures, jigs, test rigs, etc.
ENJOY!
We are!
K2
ENJOY!
We are!
K2
PISTON, ROD, WRIST PIN
Here are the rod, piston, and wrist pin. All finished/semi-finished. The rod is 117 mm C to C. The conn rod big end bore is roughed out until it is time for the bearing/bushing. The rod profile needs a little shaping to give adequate clearance for the piston skirt and cylinder liner.
Here are the rod, piston, and wrist pin. All finished/semi-finished. The rod is 117 mm C to C. The conn rod big end bore is roughed out until it is time for the bearing/bushing. The rod profile needs a little shaping to give adequate clearance for the piston skirt and cylinder liner.
peterl95124
Well-Known Member
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looking good !!!, this is the point where I start grinding notches in the end of the cylinder liner and taking off some of the piston skirt, rather than weaken the con-rod, YMMV, ...
The conn rod looks out of proportion to the piston, but it is a diesel, and the stroke to bore ratio is 1.30, so I will accept it for what it is. The original Detroit Diesels were 1.18, but I wanted to give as much combustion travel as I could. The DD was about 3.7" (out of the 5" stroke) and my model will be about 1.5" (out of the 2" stroke).
I just measured the max tilt angle of the rod when installed in the piston, and it is 75.9 degrees which places the center of the rod big end 1.118" off center. Because the crank radius is 1.00", it looks like there is plenty of clearance of the rod to the inside of the piston skirt. Checking for interference between rod and cylinder liner is a bit more involved and I will have to do that graphically as soon as I update the as-built assembly drawing.
There is something very satisfying in updating the as-built drawings to the actual real dimensions. It is like I built the parts exactly to the drawing, LOL. But I do find the update process to be very important because a few thou here, and few thou there can make a pass-fail difference, unless you compensate for it as soon as you know about it. I have no qualms at all deviating from my original design, because sometimes it even turns out better.
As you can tell, I am having a great time with this project! But I sure hope that in the end, it actually runs!
Lloyd
Well done guys, nice machining... - wrong subsidiary comments. ("Grinding notches", "The rod profile needs a little shaping to give adequate clearance", etc.) - NOT what I feel I should be reading here.
But please do the DRAWINGS properly and work out sizes correctly before machining. It saves all the "unprofessional bodging" I hear you planning....
The most successful people on the planet plan to fail. They usually succeed 100%.
Others take the more difficult (sensible?) way of planning for success, and sometimes fail, but do better than "Don't plan at all, "Wing-it" and fail in the process" crowd....
Don't waste you own lives with "doing it wrong then trying to fix it afterwards" - YOU are BETTER than that! (May be I am not, but I try to be!).
I don't mean to upset anyone, but simply help you do a better job: I.E. "Right first time EVERY time".
Please?
K2
But please do the DRAWINGS properly and work out sizes correctly before machining. It saves all the "unprofessional bodging" I hear you planning....
The most successful people on the planet plan to fail. They usually succeed 100%.
Others take the more difficult (sensible?) way of planning for success, and sometimes fail, but do better than "Don't plan at all, "Wing-it" and fail in the process" crowd....
Don't waste you own lives with "doing it wrong then trying to fix it afterwards" - YOU are BETTER than that! (May be I am not, but I try to be!).
I don't mean to upset anyone, but simply help you do a better job: I.E. "Right first time EVERY time".
Please?
K2
Steam,
I know that you have a thick skin, and a sense of humor, as do I, so we might have to agree to disagree on this one. There is a wide latitude between complete planning, and unprofessional bodging. For hobbyist work , it is usually a matter of the time budget or the tools available. I always start with decent drawings, definitely not napkin sketches, but with enough detail where all of the important features are planned, and the best attempt is made to build to the drawing although, as I said, a few thou here and a few thou there, might have to be accepted. And the more complex an assembly is, the more surprises might turn up along the way that require professional judgement to be exercised. Sometimes those surprises occur because this hobby is a learning effort. I feel that if you don't make mistakes, you are not pushing the envelope.
Where I spent my last 25 years working, there were some brilliant people working who had the best analytical software and the knowledge to use it. And ridiculous budgets to analyze all the vibration, shock, heat, performance, etc, etc. And they almost always got it right. And my hat is off to these geniuses.
But at home in my shop I have neither the luxury nor the desire to carry things out to that many decimal places.
I prefer to build some prototypes, see what works, and then revise and/or re-start. Prototyping is almost always money well spent.
Indulge me the opportunity to relate a real world experience. There was a guy who invented some new technology for a popular piece of outdoor sporting equipment. He got his foot in the door to a well known manufacturer, who had the capability and the "need" for something new in their field. Meetings were held, the guy built prototypes to the best of his ability, a patent was awarded, and a licensing agreement was put into place and everyone was eager and excited. The prototypes and drawings and lots of personal consulting was turned over to the licensee. The licensor offered the advice to the licensee: replicate the prototypes and test them, and you will find these two specific problem areas that need to be addressed. The solutions should be straightforward but must be implemented and tested before moving forward with the final design.
Instead, the licensee spent all of their time budget developing a perfect 3d model where everything worked perfectly. No prototypes were built. If the "give it a try and see what needs to be changed," approach had been taken, the project would have been a big success, instead of just a mediocre success. Lessons learned.
Steam, maybe it is just a matter of semantics, but we have both achieved success (and failure) in our many endeavors, using methods that we believe in because we know they (almost always) work.
And, @Steamchick , while I am on a roll (and have not taken offense, nor meaning to offend), my original comment about "the rod profile needs a little shaping for adequate clearance tot eh liner and skirt," was for shaping that was in my previous planning of hand shaping to mimic the inside radius of the piston skirt and liner.
Oh Ye of little faith.
And all of that planning was being done to also assist in doing some analytical work regarding he balancing of the crank and associated rotating and mechanical parts. Again, Oh Ye of little faith.
For example, if an engine is balanced for 6,000 rpm and the rpm drops 1,000 to 5,000 rpm (a 17 percent reduction of angular velocity) but if an engine is balanced for 2,000 rpm and the rpm drops 1,000 to 1,000 rpm (a 50 percent reduction) the resulting imbalance increase can be as high as 37 Percent for the 6,000 rpm engine, but as high as a staggering 125 percent for the 2,000 rpm motor. Or something in that neighbor hood. Definitely maybe.
Steam, if you saw the number of spreadsheets that I already have for vibration and rod angularity, and cylinder pressures, and balancing, for this project, I venture to say that you might be coming to me with hat in hand....
Yes, I am glad we both have a sense of humor, LOL.
Oh Ye of little faith.
And all of that planning was being done to also assist in doing some analytical work regarding he balancing of the crank and associated rotating and mechanical parts. Again, Oh Ye of little faith.
For example, if an engine is balanced for 6,000 rpm and the rpm drops 1,000 to 5,000 rpm (a 17 percent reduction of angular velocity) but if an engine is balanced for 2,000 rpm and the rpm drops 1,000 to 1,000 rpm (a 50 percent reduction) the resulting imbalance increase can be as high as 37 Percent for the 6,000 rpm engine, but as high as a staggering 125 percent for the 2,000 rpm motor. Or something in that neighbor hood. Definitely maybe.
Steam, if you saw the number of spreadsheets that I already have for vibration and rod angularity, and cylinder pressures, and balancing, for this project, I venture to say that you might be coming to me with hat in hand....
Yes, I am glad we both have a sense of humor, LOL.
Thanks ! - I do appreciate where you are coming from with your comments, and also appreciate your expertise and depth of endeavour are very thorough.
My point (semantics maybe?) was that:
Reading the words (not necessarily trying to re-interpret as how you really do things as I am sure you are expert and thorough) - which anyone can and will do - could be very mis-leading and suggest to them that you are explaining is the correct way. I.E. "Make something that looks OK, find where it fouls, then file a bit off here and there till it works, and that's it".
I am sorry if my words were harsh - not wanting to offend anyone, just wanting to say that if we want to encourage others in the CORRECT process - as we are trained and believe is correct - then we should explain that process so others can equally improve their knowledge and skills.
I admit I have made a con-rod, left excess material on (because of a poor set-up), forgotten that in the build and then assembled an engine that fouled the cylinder. It is good to admit mistakes and explain why, how, and how to rectify mistakes. But surely "we that think we know enough to advise" should explain the Best Practice we know?
And I think - having done it - that is is quite easy to plot on the drawing board so you can arrange the bore, piston, crank, conrod and see where fouls will occur - or better still NOT occur during rotation of the crankshaft. (I do it manually as my CAD does not exist - left it when I retired). And I think the proper way for things like that is ON THE DRAWING - before you cut metal. And being "Human" I make real mistakes on the drawing board that do need re-checking and re-working when I find something I got wrong, but I like to think that I correct my errors and properly modify parts, rather than just "grind-off a bit to make it clear", as Peter suggests...
Surely that "uncontrolled" adjustment/bodging/tuning or whatever we call it is simply crucifying all the calculations we made of con-rod strength, etc? Either by making sections thinner than the design (increasing stress and reducing stiffness?) or by introducing a stress-raiser (add a notch here and there?).
Aside - In my earlier job designing high voltage switchgear, there were many cranks, rods and linkages to pistons, etc. If I released a drawing that caused the con-rod to foul a bore, then I would have had to "explain my stupidity to my boss", redesign the parts - and get my boss to sign-off all the calculations drawings, etc, before the CORRECT part(s) could be made and fitted. Too many gaffs and I would lose my job. SO thoroughness in DESIGN was all important before cutting metal. Most of the service failures that had occurred during the previous 20 years or so were due to "parts that had been modified to fit" - thus compromising the design of components and shortening their fatigue life. So the strategy for good products when I was there was "good design, thoroughly checked" - before manufacture. And I think this is "best practice when modelling", as we should be modelling the best process as well. Not just making "shiny metal pretty things".
My simple request is - joking apart - when writing in these very useful and informative threads, please explain to us all, experts and beginners, the "best practice way" to rectify such an inconvenient foul, so we can learn and improve the "proper" way to do things?
Thanks, I am sorry if my post caused any upset. And lets joke about it when it finally runs.
K2
My point (semantics maybe?) was that:
Reading the words (not necessarily trying to re-interpret as how you really do things as I am sure you are expert and thorough) - which anyone can and will do - could be very mis-leading and suggest to them that you are explaining is the correct way. I.E. "Make something that looks OK, find where it fouls, then file a bit off here and there till it works, and that's it".
I am sorry if my words were harsh - not wanting to offend anyone, just wanting to say that if we want to encourage others in the CORRECT process - as we are trained and believe is correct - then we should explain that process so others can equally improve their knowledge and skills.
I admit I have made a con-rod, left excess material on (because of a poor set-up), forgotten that in the build and then assembled an engine that fouled the cylinder. It is good to admit mistakes and explain why, how, and how to rectify mistakes. But surely "we that think we know enough to advise" should explain the Best Practice we know?
And I think - having done it - that is is quite easy to plot on the drawing board so you can arrange the bore, piston, crank, conrod and see where fouls will occur - or better still NOT occur during rotation of the crankshaft. (I do it manually as my CAD does not exist - left it when I retired). And I think the proper way for things like that is ON THE DRAWING - before you cut metal. And being "Human" I make real mistakes on the drawing board that do need re-checking and re-working when I find something I got wrong, but I like to think that I correct my errors and properly modify parts, rather than just "grind-off a bit to make it clear", as Peter suggests...
Surely that "uncontrolled" adjustment/bodging/tuning or whatever we call it is simply crucifying all the calculations we made of con-rod strength, etc? Either by making sections thinner than the design (increasing stress and reducing stiffness?) or by introducing a stress-raiser (add a notch here and there?).
Aside - In my earlier job designing high voltage switchgear, there were many cranks, rods and linkages to pistons, etc. If I released a drawing that caused the con-rod to foul a bore, then I would have had to "explain my stupidity to my boss", redesign the parts - and get my boss to sign-off all the calculations drawings, etc, before the CORRECT part(s) could be made and fitted. Too many gaffs and I would lose my job. SO thoroughness in DESIGN was all important before cutting metal. Most of the service failures that had occurred during the previous 20 years or so were due to "parts that had been modified to fit" - thus compromising the design of components and shortening their fatigue life. So the strategy for good products when I was there was "good design, thoroughly checked" - before manufacture. And I think this is "best practice when modelling", as we should be modelling the best process as well. Not just making "shiny metal pretty things".
My simple request is - joking apart - when writing in these very useful and informative threads, please explain to us all, experts and beginners, the "best practice way" to rectify such an inconvenient foul, so we can learn and improve the "proper" way to do things?
Thanks, I am sorry if my post caused any upset. And lets joke about it when it finally runs.
K2
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