Mini diesel engine.

[Mechanicboy]

u think i havent already tried that ? i already lapped my 7th plunger and housing just now and it failed again. like i said i have information from the probalby most reliable guy and he uses o rings on all his engines since the early 1990s and they never failed he said. i just dont know if he made the o ring on the plunger or inside the liner. and pls as a reminder. i would like to stay with brass and steel as a plunger . and i d like to stay on same dimensions , so pls no other suggestions. the main goal is now to achieve 100% tight pump. not another pump with cast iron...no longer plunger....it must be 18mm plunger ( same bore depth ) +- 1mm bore depth . i found that when i drill 1.9mm and then ream 2mm H7 it is a hole about 2.02mm because my plungers fit as soon i reach under 2.023mm at 2.019 they are alreadx to loose and at 2.020 they start to work good , but only for short time once the brass is a bit peeled or ground by the plunger they get leaky... i hope my o ring set arrives soon. i ordered them from ebay. 12-Size Waterproof Rubber Watch Crown O-Ring Gasket Assortment 1000Pcs 1.4-2.8mm | eBay

with those o rings i should be able to fit one or two in a row on the 2mm plunger .when i make a samll groove in it ...well lubricated they last forever i have been told!

You used cylinder made of brass instead cast iron. The problem with brass: the gringing particle by lapping paste will be embedded in brass where is very difficult to clean up free from lapping paste. Hence you got leakage in short time.

 

[pirmin kogleck]

You used cylinder made of brass instead cast iron. The problem with brass: the gringing particle by lapping paste will be embedded in brass where is very difficult to clean up free from lapping paste. Hence you got leakage in short time.

But my cylinder is only drilled and then reamed to 2mm H7

The plunger is then put to size and cleaned well in boiling water to prevent that i try to not use diamond paste!

I am aware of that and as u said the plunger has to have a mirror finish u where not right!
Such tight pressure fits are achievable more likely with rougher surfaces.
I try to show u some info on that !

I still think o ring is the best idea and worth a try.

 

[pirmin kogleck]

https://www.mnrubber.com/tools-reso...er-standard-parts/groove-design-o-ring-seals/

 

[pirmin kogleck]

In the link above it is mentioned wich roughness on surface has to be achieved for a O ring in a rotary or linear piston application.

 

[ajoeiam]

Re: use of o-rings - - - please see attached.

Reading through the doc it would seem that using o-rings in an injection system is likely something fraught with issues.
Speed of motion and the pressures involved would appear to be the issues.

Now if you keep your piston motion slow and the pressures down - - - - hmmmm dunno how you're going to get a working engine doing that.

 

[Stefan-K]

Pirmin!
Komm lass gut sein.Nicht aufregen. Du hast ja recht, aber es nützt nix diese Deppen hier zusammenzuscheißen. Das kapiert die Sorte von Leuten eh nicht. Ich hab auch schon was gesagt, hat aber auch kaum Wirkung gehabt. Am besten du ignorierst die, das ärgert sie am meisten.

 

[minh-thanh]

Hi Stefan-K !
You wasted my time because of google translate
Hi pirmin !
Can I design an engine similar to Fin Hensen's ? May or may not .
My design , With very little information ... , even stupid .. I will choose a way I can easily change : pump, diameter of Cyl , stroke... Because I need that for : trial and error
When I make the pump : use O-rings ? brass cylinder ? cast iron cylinders, steel cylinders ?...?? and what materials to use for pistons, a lot of things I have to consider
Final decision : I choose the best way possible - because then I no longer care whether it is good enough or not .
About O-rings and brass cylinders: I can't help you.
I don't like to comment on what I don't know. Just as I have no opinion about other people tell you must to do....
So If you chose O-rings and brass cylinders: trial and error is the only path you have to take.

 

[pirmin kogleck]

hy stefan , hy minh, thanks for comments...

1: i know it is useless to adress my thoughts to those peope wich eat our time ...


stefan , i reached out to you but never got reply !


minh:
i wrote u message ,
i got email from the modeller in Malta today , he just told me today in the morning, i should use 2mmx18mm plunger and o rings 2x1mm ( i think mister hansen confused himself with his own measurements,because of his confuse tactic to not share a lot ... 2mm plunger and 2.7mm hole make no sense even with a 3.1.5.0.5mm o ring.....later hem mentioned somewhere even that he then chaged to 4mm o rings ( the pump has 4.5mm diameter so i dont believe that .

it ois a good idea to better not say anything than just recommend BUlsh*t based on zero experience or some Big engines. a plunger pump from a big engine might use this or that ...but in the end u cant just scale every part down...this would be a milkrun if i just have to scale things down..

Trial and Error is the only way to go...same on my injectors....it was a long long way...easy 100hrs with the pump and the prototypes i made wich never worked.

i will keep the post alive and try to post as soon i have o rings from china.
by the way. i ordered mne red fiber gasket and punshed 3mm holes in 1x1cm squares , right into the center comes the hole ( could also be drilled ) , then i lined them up on a bolt and secured them with a nut , this went on to the lathe and then i sanded them...i got perfect round gaskets like find hansen... the red material is available on ebay inn several grades ! it is super good, much better than the brown i used on my pump now.

thats it for now

regards

Pirmin

 

[pirmin kogleck]

this is the gasket materials, i have 0.5 and 1mm , all u need is a leather belt punch to punch the holes and then cut 1x1 cm and the rest on the lathe,..,.

https://www.ebay.at/itm/233181275868
https://www.ebay.at/itm/331544193055

 

[pirmin kogleck]

Re: use of o-rings - - - please see attached.

Reading through the doc it would seem that using o-rings in an injection system is likely something fraught with issues.
Speed of motion and the pressures involved would appear to be the issues.

Now if you keep your piston motion slow and the pressures down - - - - hmmmm dunno how you're going to get a working engine doing that.

i can assure u that two persons wich had succes on their Diesel Engines used a 18x2mm Plunger with O rings. thats all i can say. i have no idea wich shore the rubber was , i have no idea about the travel of the piston in meters per minute / m / min and also no idea about the groove size and the corect o ring, i would have to do some maths here...but one of the modellers wich had succes used the o rings from the cheapest gas lighters, they seem all to use the same size o ring and i checked it , they are either 2.5x1x05 or 3x1.5x0.5 or 2.7x1x0.5mm ...so i think two in a row might work...like Minh said trial and erroro, right now on my table i have 3 injection pumps and i just wait for the o rings to arrive..i cant await it and started another diesel model aero engine ( comperssion ignition ) just to keep me busy

 

[minh-thanh]

This has been a very useful and popular thread. Lets keep it that way by confining the posts to topics relative to building model diesel engines. Many fulll scale experiences are also helpful and but should be limited to things relevant too model engines.

Gail in NM
Moderator

Well that's correct and that's why when I started this thread I said :

To me that is useful information.
And thanks to Timar and others for the information on the experience on the big engines !

 

[minh-thanh]

Hi pirmin kogleck !

There's one thing that I'm not clear on:
Where do you use O-rings? Is it the same as in the picture ?

 

[pirmin kogleck]

This has been a very useful and popular thread. Lets keep it that way by confining the posts to topics relative to building model diesel engines. Many fulll scale experiences are also helpful and but should be limited to things relevant too model engines.

In the next few days I will be cleaning up this thread to removing or editing non relevant posts including personal attacks and responses to them. As my time is very limited right now due to cleaning up water damage to my house from a broken irrigation water supply line I am asking the other moderators to assist in this effort. We may make a few mistakes doing this so if you think you have been treated unfairly contact one of us and we will try to resolve the conflict.

I will remove this post when the cleanuo is complete.

Thanks for your cooperation.
Gail in NM
Moderator

i will try to take my posts out... thanks for your message . regards from vienna !

 

[pirmin kogleck]

Hi pirmin kogleck !

There's one thing that I'm not clear on:
Where do you use O-rings? Is it the same as in the picture ?
View attachment 136555

no on the plunger in the bottom, cut a groove into the plunger and fit the o ring. this might needs a littler testing and some refinements.

 

[pirmin kogleck]

hy guys, after a little research i was able to find some information about the A frame Gasoline engine from BENGS MODELLBAU ( a german engine brand and modellshop wich sells casting for hit and miss and other engines and steym engines etc) they developed a engine called Jonas wich also uses a plunger pump, a bit larger than the one i try to get run propperly but it seems to work, the pump delivers fuel from the tank up in a second small tank underneath a carb, wich alsmost looks like a displacement lubricator from a steam engine....anyway...the pump uses an o ring, this is what i found out and i found a pic from Mr. Bengs personall build, the pump is located in the bottom left .

 

[pirmin kogleck]

here a video of my injector at work !
but this was with a lwaking pump, at first as thwe pump was tight it was much better than that but i think this video shows that it is possible to make em as small as find hansen did ( body is about 12mm ) needs a non return ball vlve and a 0.94mm needle with a M1 thread at the last 1/3 with two small m1 nuts to secure . the hole drilled is 1mm


https://youtube.com/shorts/DVBAK2-_bJ8?feature=share

 

[minh-thanh]

Hi !
Don't try to force it to create really high pressure,
Injection time is about 45 degrees before TDC ( + , - ) , I think it will be fine .
Because at that time, the pressure in the cylinder of the engine engine was very low and it doesn't put too much pressure on the pump or the O-rings
( My goal is to do the best I can because I like and I need it for a lot of testing. )

 

[pirmin kogleck]

thanks for that info! i think i did exact that mistake that i forced tomuch out of the pump..., and my thoughts about it are as follow:

when u hit the injection tester with the finger, it cant generate the same momentum as a injection pump cam ! the cam hits the pump much faster and shorter time, so i think it will be fine , but i still need a new pump cylinder because mine now leaks. you are maybe right at 45deg before tdc the pressure is quite low and i also thought maybe i will be fine with my pump. because the injectors proofed to work , so we will see .. i will wait for the rings and then i can report and tell the difference. i just would like to have my pump sealed becase i dont want to have a small fuel pit underneath the engine when runnning aswell , you know ...kerosene smells not pleasant and it would look much better if there are no leaks, same with steam engines, when the gland packing is not tight it looks not good when there is water and steam leaking everywhere...

 

[minh-thanh]

With O-rings and brass cylinders : If you want to create really high pressure to inject at 22 or 20...degree before TDC, you will make wear them out in a short time and damage the O-rings.
So 45 degrees ( +, - ) before TDC seems fine
Edit :
So you don't need to test your injector with high pressure.
build an engine and test : trial and error !

 

[pirmin kogleck]

okay. i also researched a little about this topic and thewre are o rings for exact th<t aplication wich use a harder rubber shore ( the grade of the rubber ) ...trial and error ...