Mini diesel engine.

[minh-thanh]

, but be realistic and listen to us who can provide the answers to what you need to know based on our knowledge and experience.

I think you're talking about "you", not "us"

. Do not forget that you made it work with the help of us who guided you to make glow plug engine, model diesel engine with compression screw and the 4 cylinder 4 stroke engine with good results and these model engines ran so well.

I'm always welcome to comment, everyone
I learn and get help from so many people , From masters to those who have never done engines , from forums , facebook , youtube , google... , and I am always grateful for the comments contribute

back problem : 0.03 mm stroke
The oil volume in the cylinder has a diameter of 2mm with a stroke of 0.03 mm
V = 3.14.r.r.h = 3.14 x 1 x1 x 0.03 = 0.0942 mm3
this can be achieved (??) when the lobe surface finish, the oil loss between the cylinder and the piston, the perfection of shaft, ..... is 0.0000mm , eliminating the vibration engine running.....
Because all of that will affect 0.03 mm of piston stroke
Watch from the 28th minute of the video, you can see the piston stroke - that is probably the only video where i can see the piston stroke
and I'm sure it's not 0.03 mm . stroke

 

[Mechanicboy]

back problem : 0.03 mm stroke
The oil volume in the cylinder has a diameter of 2mm with a stroke of 0.03 mm
V = 3.14.r.r.h = 3.14 x 1 x1 x 0.03 = 0.0942 mm3
this can be achieved (??) when the lobe surface finish, the oil loss between the cylinder and the piston, the perfection of shaft, ..... is 0.0000mm , eliminating the vibration engine running.....
Because all of that will affect 0.03 mm of piston stroke
Watch from the 28th minute of the video, you can see the piston stroke - that is probably the only video where i can see the piston stroke
and I'm sure it's not 0.03 mm . stroke

You have not understood the whole point of 0.03 mm.
It is not the lifting height of the camshaft itself.
When Find Hansen measured the 0.03 mm pump stroke it was at idle he could observe how big the pump stroke was to be able to run the engine at idle.

Look at it all: For example, the camshaft has a height of 3 mm stroke and the regulator has a wedge that goes in / out between the camshaft and the pump. It is this wedge (red wedge in picture) that changes the pump stroke length from 0 mm (engine is stopped) to a maximum of 3 mm (maximum injection volume at maximum speed). Somewhere between 0 mm and 3 mm, there is a certain amount that is injected into the engine at a certain speed when one puts the regulator in a certain spring force which is connected between the regulator and the lever for regulating the speed.

The pump stroke varies depending on the speed range via the regulator and one controls the speed using the spring force. Tight spring force = high speed and slack spring force = low speed.

The amount injected into the diesel engine is very small in a small engine. The fuel itself has high calories to burn so well in the combustion chamber. Look at the model engine running for a long time on a tank that there is such a small amount that is burned for each engine burns at each combustion stroke.

How is fuel injection measured in the car diesel engine?
Fuel injector size determines how much fuel is able to be injected into the combustion camber by the injector. Normally, fuel injectors are sized by cubic centimeters per minute of fuel able to flow through them.

Also in a model diesel engine, there is even much less fuel that is injected into the internal combustion engine than in the car diesel engine.

 

[Steamchick]

Excellent explanation Jens. I am learning a lot.
K2

 

[TonyM]

''You have not understood the whole point of 0.03 mm.
It is not the lifting height of the camshaft itself.
When Find Hansen measured the 0.03 mm pump stroke it was at idle he could observe how big the pump stroke was to be able to run the engine at idle.''

I fully understand, as I am sure Minh does also, Jens graphic description but I have to agree with Minh on this. If you slow the video at 28.2 then, remembering this is running at idle, that pump is moving way more than .03mm / .001'' more like 1-2mm After reviewing the vid again the wedge looks at about the half way mark at the speed it is running. So based on the wedge being 0-3mm, the pump piston movement is about 1.5mm at tickover.

 

[Mechanicboy]

''You have not understood the whole point of 0.03 mm.
It is not the lifting height of the camshaft itself.
When Find Hansen measured the 0.03 mm pump stroke it was at idle he could observe how big the pump stroke was to be able to run the engine at idle.''

I fully understand, as I am sure Minh does also, Jens graphic description but I have to agree with Minh on this. If you slow the video at 28.2 then, remembering this is running at idle, that pump is moving way more than .03mm / .001'' more like 1-2mm After reviewing the vid again the wedge looks at about the half way mark at the speed it is running. So based on the wedge being 0-3mm, the pump piston movement is about 1.5mm at tickover.

The pump stroke varies all the time depending on the speed and load so there is no fixed pump stroke in a diesel engine that it can go far down to the lowest pump stroke to the highest pump stroke in a speed range. If you load a motor, then it gives the larger pump stroke, you let it run unloaded, eg drive a car down, then the pump stroke becomes smaller or zero fuel. The same goes for the engine faster than it should run, then the pump stroke becomes smaller and vice versa. See at the movie of the Find Hansen's engine: The regulator, it never stands still. It regulates all the time.

 

[minh-thanh]

Mechanicboy .
I know you want to help, but right now: sit down, have a coffee or a beer, calm down and think !!

 

[Steamchick]

Gentlemen, I suspect you are on the same lines, but at different perspectives. (I'm just as likely to get this wrong, as right, but here goes....). I think the perspective of the fuel pump with variable stroke - connected to a governor - says the pump has a "minimum" stroke that it will use with governor adjusted to "idle"... but that isn't Minh Thanh's demonstration. It is the demonstration in the Utube videos.
However, Minh Thanh is demonstrating that he can achieve an injector that will work "at some pressure and volume delivery" - likely to be the maximum stroke - ergo volume - that the pump can deliver.
Maybe the next step is for Minh Thanh to develop a means of adjusting the stroke of his fuel pump to see what minimum speed and pressure it can deliver a "good spray" ??
There is one caveat that may or may not affect all this: The demonstration of a hand (or powered) pump showing the spray pattern (I learned using a Lucas CAV hand pump back in the 1960s) only demonstrates the pattern of fuel spraying into still atmosphere. When introduced into an engine, with variable speed and pump delivery (stroke controlled), the internal cylinder pressure is going to be +25bar - or whatever - and the much denser air will have a tremendous amount of turbulence or swirl generated by the shapes of the surfaces of the changing volume of the cylinder as the piston moves. So the "hand-pump" test does a few things:

1. It determines a pressure at which the injector opens (Generally, the higher the better). As seen on the pressure gauge - as I remember from 55 years ago...?
2. It shows the spray pattern, so you can measure the "angle of the cone" - I was taught that for a multi-cylinder diesel, it was more important to match injectors for pressure, then angle of cone, than anything else, for a smooth running engine.
3. It shows the spray pattern, so you can measure the "uniformity of spray of the cone". You don't want it to be "all on one side" - or with "gaps in the cone". - These would be classed as NO GOOD, and re-worked until OK or scrapped.
4. You can check for leakage by pumping to 3/4 (??? - I can't remember, but an expert will surely advise?) of the "spray pressure", holding for a minute, then checking how many drips have fallen from the injector. NONE is good.

But back to the volume delivered... Minh Thanh, - I think (from the thread above) you do need to consider making a 2mm diameter pump instead of the 4mm you have made. Then measure delivery pressure from the injector and specific rpm, as well as the delivery volume. Then you will have numbers to help the experts advise you properly.

I hope this helps, and apologise if I am completely "off-target" or inaccurate with my remarks. I am an amateur in the subject of "diesel injection"... maybe the experts can help us all understand this subject in correcting my diatribe.
Stay happy! - Life is too short and too little Love, Laughter is most important.
K2

 

[ajoeiam]

I believe its a magazine but what is 'SIC'?
(Referring to an earlier post in this thread.)

 

[Mechanicboy]

However, Minh Thanh is demonstrating that he can achieve an injector that will work "at some pressure and volume delivery" - likely to be the maximum stroke - ergo volume - that the pump can deliver.
Maybe the next step is for Minh Thanh to develop a means of adjusting the stroke of his fuel pump to see what minimum speed and pressure it can deliver a "good spray" ??
There is one caveat that may or may not affect all this: The demonstration of a hand (or powered) pump showing the spray pattern (I learned using a Lucas CAV hand pump back in the 1960s) only demonstrates the pattern of fuel spraying into still atmosphere. When introduced into an engine, with variable speed and pump delivery (stroke controlled), the internal cylinder pressure is going to be +25bar - or whatever - and the much denser air will have a tremendous amount of turbulence or swirl generated by the shapes of the surfaces of the changing volume of the cylinder as the piston moves. So the "hand-pump" test does a few things:

1. It determines a pressure at which the injector opens (Generally, the higher the better). As seen on the pressure gauge - as I remember from 55 years ago...?
2. It shows the spray pattern, so you can measure the "angle of the cone" - I was taught that for a multi-cylinder diesel, it was more important to match injectors for pressure, then angle of cone, than anything else, for a smooth running engine.
3. It shows the spray pattern, so you can measure the "uniformity of spray of the cone". You don't want it to be "all on one side" - or with "gaps in the cone". - These would be classed as NO GOOD, and re-worked until OK or scrapped.
4. You can check for leakage by pumping to 3/4 (??? - I can't remember, but an expert will surely advise?) of the "spray pressure", holding for a minute, then checking how many drips have fallen from the injector. NONE is good.

But back to the volume delivered... Minh Thanh, - I think (from the thread above) you do need to consider making a 2mm diameter pump instead of the 4mm you have made. Then measure delivery pressure from the injector and specific rpm, as well as the delivery volume. Then you will have numbers to help the experts advise you properly.

Steamchick ..

The cone and length varies from nozzle to nozzle depending on the type of diesel engine built as a direct injection, pre-chamber or vortex chamber diesel engine.

Semi-diesel engine is injection nozzle difference from diesel engine injection nozzle as it is not high pressure that opens the nozzle needle, adjustable nozzle works the same principle as hand spray where you can regulate the nozzle from thin jet to fine atomized spray and the fuel is already heated by hot bulb to develop into fuel steam before combustion starts. Thin jet directly in the cylinder at high speed so that the hot bulb does not get too hot and leads to engine knocking under load and a nice atomized spray to idle to keep the hot bulb warm (see away from Find Hansen who used the same nozzle in both model engines Diesel engine and semi-diesel engine as the semi-diesel motors are too small to have an adjustable nozzle).

Leak test: hold the test pump up to the opening pressure 1-2 bar before the opening pressure and let it stand for a few minutes: if it drips, it is not completely tight nozzle and must have a new nozzle needle set. No drip = the nozzle needle is tight and everything is in order. Nozzle with the right opening pressure you can hear "RRR - RRR - RRR" every time you pump at a certain speed on test pump (I have worked and still work as a car mechanic for over 30 years).

As you just wrote about 4 mm pump diameter, it's way too big. We have such Norwegian-produced SABB semi-diesel engine, they have a pump that has a diameter of 6 mm, there is only a 2 mm difference between Thanh own pump and pump in the SABB semi-diesel engine. SABB Type C has a bore of 120 mm and a stroke of 150 mm and uses 6 mm diameter and the stroke is not large, varies from about 3-4 to 6-7 mm depending on the speed range. 4 mm pump provides too much fuel for a small engine and much more difficult to regulate the stroke to get a desired amount to inject into the engine as a much shorter stroke is required than a 2 mm bore pump. With a smaller pump diameter, it becomes a larger range to regulate the amount from the smallest to the largest stroke. Because a pump with a small diameter with a larger stroke length makes it easier to regulate from the lowest to the highest amount of fuel.

And the nozzle does not atomize so well on a reduced camshaft profile of 1.8 mm. This means that a much smaller nozzle about as small as a match as you can see in the photo at Find Hansen is needed for it to atomize better on a smaller amount of fuel.

Thanh ..
The injection nozzle size is determined by the pump size. So you have gained new experience why it does not atomize so well at the smaller amount of fuel needed in a small engine after you had reduced to 1.8 mm pump height. 4 mm diameter and reduced stroke does not work as well on a nozzle that is larger than Find Hansen's nozzle.

 

[minh-thanh]

The injection nozzle size is determined by the pump size. So you have gained new experience why it does not atomize so well at the smaller amount of fuel needed in a small engine after you had reduced to 1.8 mm pump height.

I found the cause : Ball valve spring is too weak,
sometimes the outlet pressure is very weak. I replaced the springs with a new one and it sprays so much better.
I just thought that the springs just holding the ball in place with light pressure would be enough, but I was wrong
1.8 mm stroke is max stroke, With the latest video the piston stroke is less than 1mm ( about 0.8 mm , but I'm not sure )

I will try with diameter 4mm, 3mm and 2mm .
because I don't know how well the pump I do? does it generate enough pressure...
With the injectors, I'm making 2 new injectors, their size will be smaller like no.2, no 3
There's only one way to know: trial and error

 

[Mechanicboy]

I found the cause : Ball valve spring is too weak,
sometimes the outlet pressure is very weak. I replaced the springs with a new one and it sprays so much better.
I just thought that the springs just holding the ball in place with light pressure would be enough, but I was wrong
1.8 mm stroke is max stroke, With the latest video the piston stroke is less than 1mm ( about 0.8 mm , but I'm not sure )

I will try with diameter 4mm, 3mm and 2mm .
because I don't know how well the pump I do? does it generate enough pressure...
With the injectors, I'm making 2 new injectors, their size will be smaller like no.2, no 3
There's only one way to know: trial and error

In outlet, the spring must be strong (not stronger than injector needle spring), but weak spring in suction side due limited by force of vacuum created by pump.

 

[Vietti]

SIC magazine was a fantastic source for those interested in internal combustion engines. SIC stands for "Strictly Internal Combustion". The founder/editor was Bob Washburn. As the title suggests its only about internal combustion with no clocks or steam, etc.

I had forgotten how good it was till I went looking for the info on the Dux. May have to sit down and read the whole series again! Well worth the effort to get copies.

Does anyone know how to get copies??

John

 

[Steamchick]

Thanks Jan.
K2

 

[Steamchick]

1.8 mm stroke is max stroke, With the latest video the piston stroke is less than 1mm ( about 0.8 mm , but I'm not sure )

I will try with diameter 4mm, 3mm and 2mm .
because I don't know how well the pump I do? does it generate enough pressure...
With the injectors, I'm making 2 new injectors, their size will be smaller like no.2, no 3
There's only one way to know: trial and error

Hi Minh Thanh,
As "the ancients" found out when throwing rocks at each other..... You have your first marker - the 4mm diameter pump ram.
Next make the smallest you can: 2mm diameter or less? then compare calibration of the smallest volume of fuel the pump will deliver (I.E. the pump variable stroke device adjusted to the minimum that works the injector successfully), with the "expected volume" - from the advice from others above. Then a simple comparison will tell you:

1. If the smallest you can make is small enough,
2. if the smallest you can make is large enough - at max stroke - for the max. fuel you need for the engine you are making.
3. Remembering that delivery volume is proportional to the SQUARE of the diameter, you can determine the cross-sectional area of ram to meet the minimum fuel volume you need (for idling the engine) and the max stroke that that diameter ram needs to get the max. fuel you need.
4. Then you can make the pump to the required sizes.
5. This empirical method should save a lot of "trial, error, frustration and disappointment, and time, before success is achieved.

It is called "Engineering": Determining where you are going by "Thinking" - before setting out on the journey - then "re-thinking" the details of each next step with the information gathered from the previous step. ("Engineering" is "problem solving" - the "application of Ingenuity").
A tip from NASA (possibly mis-quoted?): "Nobody ever "succeeded" by making a rocket and just "launching it, to see where it would go". But the "Engineering method", of "calculating what is needed", then confirming with some simple tests, before designing and making the real rockets to the determined size, enabled NASA to put a man on the moon and bring him home safely...."
Another quote: "Engineering brings order to evolution, so (many) evolutionary steps can be jumped". (or something - can't remember who taught me that one!)
Hope this helps,
K2

 

[minh-thanh]

Hi All !
Very useful information :

 

[Mechanicboy]

You got about the same answer as here and the other forum when we talked about pump diameter and stroke of a certain size of cylinder volume in the engine.

In fact, the stroke during operation at a certain speed is never a fixed stroke as it varies all the time in a range from the lowest to the maximum stroke controlled by the centrifugal regulator, let us say: at stop the pump stroke is 0 mm and the maximum pump stroke at 1.5 mm, then the diesel engine in an area for example goes somewhere between 0.3 mm and 0.5 mm in a moderate speed with a slightly tight regulator spring, one increases to the desired speed, for example close to the top speed by tightening a little more regulator spring, then it can be between 0.9 at the lowest to the highest 1.2 mm. The pump stroke length is determined by the regulator spring and centrifugal regulator depending on the engine speed and the regulator is never in a certain position, it varies all the time as I had written in a previous post.

When making a pump stroke determined by the wedge between the pump and the cam: Wedge that has a pitch starting from one end 0 mm and up to 1.6-1.7 mm at the other end. Cam disc lift height 1.7 mm which is the maximum as you never reach the 1.7 mm stroke as you can control the speed range yourself via the regulator. Choose a spring that is weak and try until you can regulate from minimum to maximum speed, the engine does not go to maximum speed, replace to stronger springs and try again if you reach the desired speed range. Excessively strong springs are not easy to regulate from low speed to maximum speed, in the worst case the engine can accelerate until it is eventually destroyed.

 

[minh-thanh]

Last word, I will update until I can get the engine running
If the engine can run , and can be damaged at too high a speed... I don't care . I just need it running !
I hate arguing, discussing what I don't know and have no experience with
I'm sure everyone was disgusted reading this thread, I'm sorry !

 

[GreenTwin]

I may have already mentioned this, but it seems like I saw a video one time on Find Hansen's diesel injector, and he said the pressure inside the cylinder has to force the injector closed, and the cam forces the valve open.
I think his valve is like a poppet valve on a standard 4-stroke engine, but tiny.

He said this was the only way to get the valve so seal correctly.

I may have to try a hot-bulb diesel, since it would probably be easier to get it running then have to design an injector.
I don't think Find's injector is that complex though.
I have seen photos of it, and I seem to recall that he had a pretty minimal spring on it.

Good luck everyone with your diesel endeavors.

.

 

[Steamchick]

I may have to try a hot-bulb diesel, since it would probably be easier to get it running then have to design an injector.
I don't think Find's injector is that complex though.
I have seen photos of it, and I seem to recall that he had a pretty minimal spring on it.
Good luck everyone with your diesel endeavors.

You could "cheat" with the hot-bulb and have a model aircraft glow-plug screwed into the hot-bulb... Not exactly true to full size, but using a glowing element inside a hot bulb chamber should give basically the same ignition? Only needs a 1.5V battery to start, then stays hot from continued firing? - As aircraft glow-plug engines run on 50% kerosene/oil, that's close to the fuel you'd probably use on a hot-bulb engine? - But just "an Idea" from an "outsider with no experience".
K2

 

[Thommo]

You could "cheat" with the hot-bulb and have a model aircraft glow-plug screwed into the hot-bulb... Not exactly true to full size, but using a glowing element inside a hot bulb chamber should give basically the same ignition? Only needs a 1.5V battery to start, then stays hot from continued firing? - As aircraft glow-plug engines run on 50% kerosene/oil, that's close to the fuel you'd probably use on a hot-bulb engine? - But just "an Idea" from an "outsider with no experience".
K2

Hi Steamchick, FYI gloplug engines run on methanol/castor oil and sometimes added nitromethane, not kerosene. Miniature compression ignition engines most often are run on ether / castor oil.