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G8MNY  > TECHNI   06.10.21 11:20l 137 Lines 5510 Bytes #999 (0) @ WW
BID : 48770_GB7CIP
Subj: Diesel Generators
Sent: 211006/0900Z @:GB7CIP.#32.GBR.EURO #:48770 [Caterham Surrey GBR]

By G8MNY                               (Updated Aug 13)
(8 Bit ASCII graphics use code page 437 or 850, Terminal Font)

Only had experience of one, a 6kW Clarke diesel generator, it weighed in at
150kg & has a 12BHP engine all in a weatherproof noise reducing box!

               Top Hatch 
      │ Fuel  │      Decomp|   │
      │  Tank │       Valve|   │
      └─┬─────┘  Injector ||   │
Electric│ Fuel     |ENGINE||   │
  Panel_│  Tap     |      ||Fan│
      │┌ - - - - -┐| Inj- ||   │
      │|ALTERNATOR|| pump ||   │
      │|          ||      ||12V│
      │|          || Sump ||Bat│
         └─┘              └─┘

It was a little used generator that had been stored for years, initially the
main problem was dead battery, on starting, we soon found rubbish in the fuel
tank blocked much of the fuel line system...

Plastic                                Electric   Injector   Cylinder  
tank----Tap------In line------Bleed----solenoid-----fuel-----injector---unused
      on case   fuel filter   Screw    fuel valve   pump                return

When this had been cleaned out & a new filter put in, all seemed well for a 9
day radio summer camp with it.

However our wet British summers soon found that water got into the fuel tank.
The low fuel sensor was placed in the top of the tank in a large molded recess,
this of course filled up with water on a rainy day & the only way out was
straight into the tank!

┌───┐   ┌──┐ Water capture area   Return┌───┐
│   └───┼──┼─────────────────────────┘└─┘   │
│       Low       PLASTIC                   │
│       fuel       FUEL                     │
│      sensor      TANK                     │
                                     Tap Feed

Rubber seals & self taps into a thin plastic tank used by the maker are a silly
idea! Draining off 2L of fuel into an empty clear drinks bottle, showed just
how much water was getting into the fuel. (bottle now part of tool kit)

Diesels with hand start options, have an extra cuylinder valve or open the
intake valve for one full engine cycle to initialy stop the high 22:1 or
greater compression (decompression lever), this enables enough speed to be
built up for a proper compression starting stroke.

The Solenoid Tap
Fairly straight forward plunger device.

▒┌──┐▒Coil         ▀ Steel Case
▒│­­│▒             ­  Return Spring
▒│­­│▒             █  Soft Iron Plunger
▀│██│▀             ▓  Attached Rubber Seal
 │██│              │  Brass tube

On testing one annoying problem was the electric fuel solenoid, this only
operated on starting if battery > 11V or the engine was running. It was NOT
open if electrics were just in the "ON" position!

Poor Battery Starting
To overcome the fuel being shut off when the battery is slightly weak on
starting. Crank the engine over on decompress for several seconds before
releasing the decompressor. This gets quite a bit of fuel in the cylinder, that
will burn on the compression stroke even the fuel valve does shut off on the
heavy compression stroke starter battery load.

The Injector Pump
This is one of the most complex parts in a diesel, it gives variable volume at
very high pressure. e.g. 30 atmospheres or 450PSI at a few degrees before top
dead centre of the engine cylinder's compression stroke.

           ├ ┤  Ball
         ┌─┘­└─┐Valve                 The timing cam strikes the follower
    Pump ├──°──┤                      & the small piston moves fuel
 Cylinder│Ů ███│                      through the ball valve until the
         │Ů▄ ▀█│__                    diagonal slot aligns with the inlet
   Piston│Ů██▄Ů┌───Inlet              port when the output is stopped.
with fuel│Ů████│
    slot │  █╚════ Throttle Arm
         ├─ █ ─┐  (Piston rotation)   The throttle arm is a sliding key
          ­ █ ­                       on the piston that controls piston
          ­ █ ­ Return                angle & hence the fuel volume.
          ­ █ ­ Spring
          ­ █ ­
       Cam Follower

The Injector
This takes the high pressure fuel pulse & injects it in an atomised form into
the engine cylinder.

     Clamp plate
Pressure┌───┐_                  Difficult to draw here, the
   Valve│▄▄▄┌─Input             high pressure input causes
        │­ ­│                   the pressure valve to let fuel
  Fuel _│­ ­│Spring             suddenly pass through to the
 Return─┐▀▒▀│                   microscopic spray holes.
▄▄▄▄▄▄▄▄└┐▒┌┘▄▄▄▄▄▄▄▄           (Usually 4 of them).
▄▄█ Spray|▒|Spray █▄▄
▄▄█      └V┘      █▄▄           Fuel that does not get through
▄▄█      Pin      █▄▄           the holes is returned back to the
▄▄█ENGINE CYLINDER█▄▄           tank when there is combustion.

WARNING: High pressure sprayed fuel is very dangerous, it will easily go
through your skin or affect your eyes. So a cover must be used to test the
injector action. e.g. half a clear plastic bottle!

Generator Governor
This works in a similar way to that of petrol generators. Force from spinning
"Bob weights" is used to balanced against a preset speed (Hz/volts) spring &
the difference used to move the throttle arm. Note that a drop in revs is
needed to open the throttle!

See also my Tech bul on "Petrol Generators for /P SSB"

Why Don't U send an interesting bul?

73 de John G8MNY @ GB7CIP

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