Mini diesel engine.

[pirmin kogleck]

has someone ever tried to use o rings on the injection pump plunger =? i made a injector tester a injection pump
( plunger type) and injector close to find hansens measurements but my plunger gets slightly leaky after some time . here a video of the injector with the leaky pump . u can only see the injecotr but i think with a tight pump i would have a lot better spray pattern as i saw a much better mist in the first few testes before the plunger got leaky.i heard mr hansen maybe used o rings on his pump but i cant proof that as he do not share a lot of information but his videos are a usefull source, there only i could see his water feed pump used a o ring as a seal. maybe this is the way to go for a tight fuel pump. i try to achive about 35 to 50 BAR and i am very close to have a good working, mine already worked until it got leaky. the mist was very fine, much much finer than in that video i post underneath. but lets hope someone can help. i ordered me some o rings for watch crown repairs they come from 0.6mm up to 2.4mm diameter, and i hope they might help

i try to attach a video, not sure if it works

 

[a41capt]

I’ll be following this thread. I’m also wondering if O-rings would work, and thinking that perhaps a hard nylon ring (or three) might stand up to the abuse if it didn’t have too much of an “overhang”.

Keep us posted!
John W

 

[Stefan-K]

Hi together
I also built an Injection pump for a small Diesel engine. I used the dimensions that Hansen told in his Video. So its very small. I can Tell you that any Kind of o-Ring, be it Rubber or plastic does not work at All. It can not withstand the necessary high pressure. I could reach about 120 bar of Injektion pressure with this pump but only for a short time. Think about a running engine! The time when the fuel is injected is very, very short. There is no need to keep the pressure up for a long time. So if the pump is capable of building up a high pressure in a short time, enough to inject then that's OK. Its much more important to prevent the backflow of fuel with a good working check valve. Another important point is the pressure difference between the compressed air in the cylinder and the injected fuel. The higher the difference the finer the spray mist will be.
Stefan

 

[minh-thanh]

Hi pirmin kogleck !
Because they only focus on the smoke of my engine in the last video
If they sit down and ask, "Why is there more smoke than in the previous two videos?" or something like that, they'll have some of my reasons for that. But now is not necessary .
Back to your question
After thinking for a while, I don't know if I should reply to you here or in Messenger
I know there are a few people who can answer your question, but I'm not sure if they've read this thread , or for some reason it's hard for them to answer you..
So
Like I said before, ( I couldn't find it in this thread) Yes, I tried with O-rings, but I don't really like it. , I haven't tried it with the engine but again just based on experience : With a 4 stroke engine you can use O-rings for piston because the pressure is not high - compression ratio 10-1 or 9-1 ... moreover with the worn O-ring it's like trap the air and keeping the engine at 4-1 or 5-1 compression and the engine running . But you said the pressure is 35 - 50 bar, which is very high pressure and it runs in oil, and that's why I don't like to use O-rings and based on my experience with several related jobs
Some of your questions in Messenger :
In the 2 videos you sent me, your injector and the way it spray are really good and I'm sure it will be fine with my engine: 100%.
About the material, I only tried it with brass for a short time, so I don't know if it's durable or not.
I suggest you use the material combination according to the table below for the pump piston and cylinder
( black : that was my last test , and it was really good . About metal standards , Steel SAE 1020... : I chose the equivalent because my country's standards are a bit different from yours , I really hate that . )
Again , about O-rings: I don't use it on engines and I haven't experimented with it much so my opinions on it are just suggestions , and based on my little experience on how the my engine can run :
If your engine has a low compression ratio and uses ether in the fuel and gives early injection time or gives early injection time with high compression ratio- about 45 degrees before TDC seems fine.
because if the O-rings are worn, the pump will still create enough oil pressure to inject into the cylinder at the compression stroke 45, 40, 35, 30 degrees before TDC, because at that time the pressure in the engine cylinder is still low. Or you can also combine the above suggestions with brass cylinders

PS : I really hate you for bringing me back to this topic
Now, more than 19,500 members know I hate you.

Edit : Injection time: More precisely the time the lobe begins to contact the pump piston: 22 to 45 degrees before TDC

 

[Mechanicboy]

now my question :

has someone ever tried to use o rings on the injection pump plunger =? i made a injector tester a injection pump
( plunger type) and injector close to find hansens measurements but my plunger gets slightly leaky after some time . here a video of the injector with the leaky pump . u can only see the injecotr but i think with a tight pump i would have a lot better spray pattern as i saw a much better mist in the first few testes before the plunger got leaky.i heard mr hansen maybe used o rings on his pump but i cant proof that as he do not share a lot of information but his videos are a usefull source, there only i could see his water feed pump used a o ring as a seal. maybe this is the way to go for a tight fuel pump. i try to achive about 35 to 50 BAR and i am very close to have a good working, mine already worked until it got leaky. the mist was very fine, much much finer than in that video i post underneath. but lets hope someone can help. i ordered me some o rings for watch crown repairs they come from 0.6mm up to 2.4mm diameter, and i hope they might help

i try to attach a video, not sure if it works

Pirmin Kogleck..

The best solution: Lapped plunger piston of hard steel in the cylinder of cast iron with tight tolerance who are not allowing to leak the fuel, but keep the plunger lubricated toghether with the cylinder.

Lap the cylinder first until all tool marks is disappeared and then lap the plunger piston and clean up free parts for lapping paste then try to fit into the cylinder carefully with oil on the parts, relap if the plunger don't fit into the cylinder. The plunger piston must move free and keep tight into cylinder without leakage. The edge on the end of the plunger pump must not be sharp, better a bit rounded to not scratch the bore and allow to lubricate without leakage.

The plunger piston must be longer than the bore to make less leakage and less side thrust on the cylinder caused by the plunger piston.

To example we can see at the injection pump in the Sabb semidiesel engine (Norwegian boat engine) has 6 mm plunger piston and the length of plunger piston is 100 mm, also the length is about 17 times longer than diameter. Pump stroke about 5-8 mm in the maximum full stroke.

Then we can set the plunger pump to 34 mm in length if use 2 mm diameter in the model diesel engine if we calculate the diameter x 17= length.

 

[pirmin kogleck]

okay, coolthanks for all the answers!

i try to stay with brass and steel same like mr hansen , i use plunger 2mm and 18mm long , the cylinder is drilled down untill the end of the square part. at first my pump generated perfect pressure and a very very even mist pattern ! almost lke fog from a micro fogger for the garden.... i was so happy because it took me about 100 hrs to get there with several injecotrs and pump prototypes.

my main goal is to achieve same dimensions like find hansen and also i want to use the same material because he proofed it works . so i d like to stay with a brass cylinder and a steel plunger . in all the years i tried to reach out to find hansen i always got no answer, only one time , and this is about the o rings and he said i should use them in the pump.
someone said he used solder in the cylinder wich is true but only on his very first engine with very low pressure. so i will try to make a few o ring porototype pumps. and see from there what happens, i lapped about 4 or 5 plungers so far. all seem tight at first and start to leak after a few tests, my injectors are perfect , i use same dimensions as find hansen , it is easy to take measuremnts from the pics he provided.

i wait for a box of watch crown o rings from china to arrive, they come in sizes from 0.6 to 2.4mm and i think they are maybe worth a try. otherwise i will try use the mini tiny o rings from cheap gas lighters . they seem to have 2.7mm OD so i would have to drill and ream the pump cylinder a little bigger than find original. we will see . i keep u guys updated,

 

[minh-thanh]

pirmin kogleck !
If you have Mr Hansen's answer
and

about O-rings: I don't use it on engines and I haven't experimented with it much so my opinions on it are just suggestions , and based on my little experience on how the my engine can run :
If your engine has a low compression ratio and uses ether in the fuel and gives early injection time or gives early injection time with high compression ratio- about 45 degrees before TDC seems fine.
because if the O-rings are worn, the pump will still create enough oil pressure to inject into the cylinder at the compression stroke 45, 40, 35, 30 degrees before TDC, because at that time the pressure in the engine cylinder is still low. Or you can also combine the above suggestions with brass cylinders

I think you shouldn't worry too much about it .

Do the best you can - Trial and error....and I think you will
About the ether, If your engine can't run with kerosene, you should try with some ether. when the engine run you will know more about it
And then kerosene is no longer a problem for you.

 

[Mechanicboy]

okay, coolthanks for all the answers!

i wait for a box of watch crown o rings from china to arrive, they come in sizes from 0.6 to 2.4mm and i think they are maybe worth a try. otherwise i will try use the mini tiny o rings from cheap gas lighters . they seem to have 2.7mm OD so i would have to drill and ream the pump cylinder a little bigger than find original. we will see . i keep u guys updated,

To use O-ring the plunger piston must be mirror polished to not scratching the O-ring. Keep all parts clean before assembly. The nut who are holding the O-ring must be adjustable to keep tight if leakage is there and the return spring must be strong enough to return the plunger with tight O-ring.

 

[pirmin kogleck]

i didnt think about that so far. somehow truw but on finds waterpump u see the o ring is in the bottom and there is no nut or anything. sure it is the water and not the injection pump but i think the o rings are the key. i looked up model excavator micro hydraulic pistons and they use o rings on the double acting systems ( i know not the same but i thought maybe it is worth a try, and like minh tanh said, trial and error, i have spend about 100hrs so far on the tester, pumop and injectors including drawings....so i think i have to spend another 20


i will keep you updated

 

[pirmin kogleck]

@ minh than

i wnt even try to uswe ether, i want it to run without, allthough i have a lot ether athome and some model aero compression engines, i dont want to get into the ether discussion now...kerosene or nothing ! thats my goal. it must be a true diesel , not a compression ether engine ,....

 

[pirmin kogleck]

have yozu tri

To use O-ring the plunger piston must be mirror polished to not scratching the O-ring. Keep all parts clean before assembly. The nut who are holding the O-ring must be adjustable to keep tight if leakage is there and the return spring must be strong enough to return the plunger with tight O-ring.

ed it ? i mean have u made a pump and tried use o rings ? i have informations from a very very reliable persion and he mentioned he used o rings on all his plunger pumps. 2.7mm cyl. diameter , the rest is unknown of dimenions

 

[Mechanicboy]

 

[pirmin kogleck]

@Mechanicboy!

this makes sense on some bigger engines but i thinku underestimate the size of the pump, it is only 20mm high with the top art a bit more . and according to find hansens informations there is no o ring above the plunger , there is a housing for the plungerspring and a nut to secure the housing but no o ring is visibe there because there is a hole drilled for lubriicastion and u can clearly see no o rings on alkl his videos above the plunger. i can only assume that he grooved the plunger in lower section and uses a o ring there like he did on his water pump. the water feed pump is the same pum just scaled up and a bit different plunger but overall he mentioned that it shares the rest with the injection pump.

matereial barrss cly and steel plunger, o ring 2.5x1x0.5

cylinder bore 2.7mm

thats it

so i dint understand if he made a 2.7mm plunger piston aswell or a 2.6 or anything below and then fit the o rings , or if he uses a lapped plunger pistn and uses the o rings then on that lapped one so u have at least 2 secure ways to hold oressure one by lapped plunger and second the o rings . i ried to use o rings on 2,mm plunger so far i was not able to get it into the cylinder therofr i wait for tiny o rings. i cant await it...the chinese post is realy fast but this seems to take a century for me

can u mark on my picture where u would put the o ring ? ps i want to stay with that design and materials

 

[pirmin kogleck]

it would be a milkrun for me to make a big injection pump. but the sizes we are talking are so small..for my first working plunger it tookme 4 try to get one good one and this one started to kleak, and find said himself it is impossible on our smallmachines and tools to get that perfect fit without lapping , and even with lapping it starts to leak at a certain point after time. thats why i am very convinced by the o ring method.

 

[Bentwings]

Pirmin Kogleck..

The best solution: Lapped plunger piston of hard steel in the cylinder of cast iron with tight tolerance who are not allowing to leak the fuel, but keep the plunger lubricated toghether with the cylinder.

Lap the cylinder first until all tool marks is disappeared and then lap the plunger piston and clean up free parts for lapping paste then try to fit into the cylinder carefully with oil on the parts, relap if the plunger don't fit into the cylinder. The plunger piston must move free and keep tight into cylinder without leakage. The edge on the end of the plunger pump must not be sharp, better a bit rounded to not scratch the bore and allow to lubricate without leakage.

The plunger piston must be longer than the bore to make less leakage and less side thrust on the cylinder caused by the plunger piston.

To example we can see at the injection pump in the Sabb semidiesel engine (Norwegian boat engine) has 6 mm plunger piston and the length of plunger piston is 100 mm, also the length is about 17 times longer than diameter. Pump stroke about 5-8 mm in the maximum full stroke.

Then we can set the plunger pump to 34 mm in length if use 2 mm diameter in the model diesel engine if we calculate the diameter x 17= length.

I was going to suggest the same idea of a long piston in a very tight tolerance bore. You can probably lap this but I YHINK it better to be honed. Precision honing is pretty easy if you leave stock . It’s just like preparing combustion cylinders . I’ve used .003 “ stoke so called rough but smooth bore take about 1/2 of that for rough hone then about 1/2 of the remaining for sizing then the rest as “plateau “ finish sizing and finishing . This will get ride of all torn machined metal then provide a very smooth cros hatched final bore size . The piston needs a ground finish what every steel or cast iron material . The long piston length to bore length gives the seal. Probably about .0002” clearance at room temp any shop that does honing could help with what they can do . If you choose hardened bores they use boron alloy “ stones” for 0 wear so the bores will be dead straight . Automotive diesel pumps are very close fitting like this . O rings just don’t wok . I don’t realy think any type of split piston ring would be very good.

 

[pirmin kogleck]

i will say it again

i want to stay with same material as FIND HANSEN !

his pumo :

brass cylinder

steel plunger ( 18mm x 2mm )

it seems many underestimate the size of this pump . made some pics and will send them ina few minute !
i know how to lap model engine cylinders and pistons and how to make those hones, but i cant make a 2mm hone ! it is impossible. could only make a alu plunger and use it for preposilh and then lap the piston to size

 

[Mechanicboy]

I was going to suggest the same idea of a long piston in a very tight tolerance bore. You can probably lap this but I YHINK it better to be honed. Precision honing is pretty easy if you leave stock . It’s just like preparing combustion cylinders . I’ve used .003 “ stoke so called rough but smooth bore take about 1/2 of that for rough hone then about 1/2 of the remaining for sizing then the rest as “plateau “ finish sizing and finishing . This will get ride of all torn machined metal then provide a very smooth cros hatched final bore size . The piston needs a ground finish what every steel or cast iron material . The long piston length to bore length gives the seal. Probably about .0002” clearance at room temp any shop that does honing could help with what they can do . If you choose hardened bores they use boron alloy “ stones” for 0 wear so the bores will be dead straight . Automotive diesel pumps are very close fitting like this . O rings just don’t wok . I don’t realy think any type of split piston ring would be very good.

Lapping give much better precision to work in tight tolerances than to hone the parts. Read this link What is Difference Between Lapping and Honing?

I lapped the pump piston/cylinder where I created the Wakefield mechanical lubricator for steam engine without O-ring. It works very well without leakage past piston/cylinder under high pressure. I selected the pump piston of high tensile steel and cylinder of cast iron in the Wakefield mechanical lubricator.

 

[Mechanicboy]

i know how to lap model engine cylinders and pistons and how to make those hones, but i cant make a 2mm hone ! it is impossible. could only make a alu plunger and use it for preposilh and then lap the piston to size

To lap the 2 mm hole is no problem: Use brass or aluminium rod who are a light tight in bore + fine and ultra fine lapping paste to lap the hole. Lap until you feel there is same resistand in the whole length of cylinder. Be carefully. To get exactly 2 mm: drill 1,9 mm and lap the whole length and test with the 2 mm brass rod carefully there is no binding or conical cylinder inside. Surface must be mirrorlike surface. Next lap the plunger piston who are a bit larger in diameter than 2 mm and test to fit into the cylinder some times with oil after you has cleaned up both plunger piston and cylinder carefully. If the plunger piston goes a bit light tight in the bore, then lubricate with oil only and rotate plunger piston in the bore until the plunger piston goes through the bore without leakage into the bore. Take a pressure test and check there is no leakage with closed outled to injector (blindplug on outled to example).

 

[pirmin kogleck]

To lap the 2 mm hole is no problem: Use brass or aluminium rod who are a light tight in bore + fine and ultra fine lapping paste to lap the hole. Lap until you feel there is same resistand in the whole length of cylinder. Be carefully. To get exactly 2 mm: drill 1,9 mm and lap the whole length and test with the 2 mm brass rod carefully there is no binding or conical cylinder inside. Surface must be mirrorlike surface. Next lap the plunger piston who are a bit larger in diameter than 2 mm and test to fit into the cylinder some times with oil after you has cleaned up both plunger piston and cylinder carefully. If the plunger piston goes a bit light tight in the bore, then lubricate with oil only and rotate plunger piston in the bore until the plunger piston goes through the bore without leakage into the bore. Take a pressure test and check there is no leakage with closed outled to injector (blindplug on outled to example).

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!

 

[pirmin kogleck]

here u can see the leak is slightly visible on the lubrication hole . this is usualy where the pump gets a drop of oil, in my case the fuel /kerosene forms small drops but it got worse after i messed around with a new plunger and now i have no plunger wich is tight, or i should better say the cylinder is now messed up and i had to make a new one , i tried that new one and it is also not good.....,it is a realy pain to geth that part done...i tell you guys ...i have made 4 injectors wich now all work realy well but the pump is what makes me almost cry and crawl on the floor in my workshop....it is so hard and a lot of pushbacks are involved until it might work. but i know it will and can be done. i will upload a slow motion injector video on youtube the next days since it is to big to upload here.