Mini diesel engine.

[Willyb]

As Nerd1000 has cautioned in post #98. Diesel engines are totally different from their brother the gasoline engine. Gas engines with a carburetor or injector/throttle body limit and control the amount of fuel/air entering the engine. With diesel engines the intake passage to the cylinders is wide open. All diesel engines while operating at their full horsepower rating have an excess of oxygen in their cylinders after combustion. With the addition of more fuel and you will have a runaway. There are basically two ways to stop a runaway diesel. Cut off it's air or cut off it’s fuel. When I worked as a diesel mechanic I rebuilt allot of medium to large truck diesel engines. On startup after a rebuild I always made sure to have the manual handy to place over the intake pipe in the event of a runaway. Another method was to discharge a CO2 fire extinguisher into the intake which displaced the oxygen with Carbon dioxide. Some guys kept a hammer handy to break off a fuel line or fitting and try and starve the diesel of fuel. Never like that method as it usually wasn’t fast enough. I remember one guy tried to stop his runaway by putting the truck in gear to stall the engine. Didn’t work. In fact not only did the diesel require rebuilding, but it also required a new clutch. Have witnessed two runaways and in both cases the engines required overhauling, again.

All I’m trying to say here is be very careful. Without any proper fuel control you can end up with an uncontrollable engine and possibly a bomb.

Cheers
Willy

 

[Mechanicboy]

Minh-Thanh,.. easy to remember the rule:

Rule 1

A certain speed has a certain amount of diesel that is injected into the cylinder which is impossible for a designer to make a diesel engine without a regulator whether it is mechanical or electronic as the amount varies constantly under a certain speed range depending on the load of the engine.

Rule 2

The speed can be regulated by means of spring force in the centrifugal regulator or via ECU in the common rail diesel engine which is set on by the operator himself who wants the engine to run a certain specific speed.

Rule 3

Diesel engine always has excess air in the cylinder that is not regulated, only amount of diesel via diesel pump combined with regulator either it's mechanical or electronic.

 

[mcostello]

A friend was in the military and rebuilding a 8" howlizer engine and had a runaway. The engine blew and put the piston through the block and threw a block wall. He heard of another one running away and to stop it a Guy fell on the intake to stop the air. It pulled His intestines out and He died later, trying to save Others.

 

[tim9lives]

Willy B is absolutely right. I’m surly not an expert but my 20 years of turning wrenches taught me to always think about how I was going to kill the runaway diesel. Whenever I would begin to work on a MB, I’d have some sort of ball or pan which I could jam into the intake if the engine began to run away. I had to do just that on a few occasions. Damned things would start to run away and you’d better have a way to kill the airflow or you’d end up with a blown engine. Scares the hell out of you when they start to scream.

 

[minh-thanh]

After reading the comments, I thought:
The engine is pretty small, it can explode and become a bomb I don't know, but anyway I don't want it damaged when running uncontrollably - if the engine can run
2/ With a little experience: Adjusting the initial amount of oil will make it easier to start the engine
.....
So I will design and make a part to adjust the piston stroke of the pump
Thanks for the comments .
Thanks so much !

 

[tim9lives]

You could easily design a butterfly plate to close off airflow. It would look like a choke plate on a carburetor.

 

[djswain1]

Don't quote me on this, but I have an idea Bosch and CAV mechanical pumps were up to 8 or 900 psi, before the move to common rail and piezo injectors... Now those have gone from 1200 to 1600 plus psi impulsive pressure. You can't measure those injection pressures on a gauge, as they are impulsive, I.E. A shock wave generated when the injector is fired.
Looking at M-t's injection, the pressure is too low, by hand. But a cam at speed is a different matter.
I remember injector testing with a CAV hand-pump in the 1960s. But I can't remember the pressures we had for valve opening, and to witness a "good spray cone". But the intrusions were on the label affixed to the device. I think they are still available on e&@y, etc...
K2

Mechanical dieseel engines in production today (and since 1970's) that I work use injection pressure IRO 2100 - 3200 PSI
Common rail pressures are 10x that... see picture

 

[reichpaul630]

fwiw, here's some tech stuff on the Bosch VE distributor-type injection pump series. it's been a real
workhorse in a lot of truck and car diesel engines. my VW has one of these.

the requirements for a pump design, and ways that the requirements were achieved are described in
some detail. in particular, the internal governor may be interesting

it's may be worth referring to the designs Find Hansen came up with. there's an example HERE.

i'm quite interested to see what the OP comes up with.

paulr

 

[Badhippie]

Better make sure you install a deadman lever. You may need it at some point
Thanks
Tom

 

[minh-thanh]

Hi All !
An update :

 

[ajoeiam]

Hi All !
An update :

Curious - - - are you making the gears as well?

 

[minh-thanh]

Curious - - - are you making the gears as well?

Yes i made the gears myself, it's not accurate
You can download the image and zoom in and you will see
Hi All !
More :
Piston will have 3 rings.

 

[Richard Hed]

Yes i made the gears myself, it's not accurate
You can download the image and zoom in and you will see
Hi All !
More :
Piston will have 3 rings.

Accurate enough.

 

[minh-thanh]

Accurate enough.

Accurate enough with 2 : 1 . ratio

 

[Mechanicboy]

Diameter in the hole for wrist pin looks a little too thin considering the forces from the combustion pressure can be strong enough to break off the wrist pin.

 

[Willyb]

Hi All !
An update :

Hi minh-thanh

Nice parts. Keep up the good work.

Cheers
Willy

 

[Steamchick]

Do you calculate your sizes? - e.g. Wrist pin diameter? - Fatigue strength is all important to prevent failures. I'm curious for your calculations on that...
K2

 

[minh-thanh]

Mechanicboy !
You're right,
I can drill holes as large as 5.5 mm
But I'll drill the big hole when I make the connecting rod
Steamchick !
Not, Do you know a formula for that ?
Willyb !
Thanks ! I will..

Hi All !
A Update ::

 

[Thommo]

Hey Than, your machining looks better with every engine you build mate

 

[minh-thanh]

Hi Thommo !
Thanks !
Are you Mark Thomas ?

Hi All !
A update :