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G8MNY  > TECH     27.06.26 16:52l 170 Lines 7278 Bytes #9 (0) @ WW
BID : 63501_GB7CIP
Read: GUEST
Subj: PERFORMANCE POWER 1kW Genny
Path: JH4XSY<N3HYM<K5DAT<GB7BED<EI2GYB<GB7CIP
Sent: 260627/0747Z @:GB7CIP.#32.GBR.EURO #:63501 [Caterham Surrey GBR]
From: G8MNY@GB7CIP.#32.GBR.EURO
To  : TECH@WW

By G8MNY                                     (Updated June 26)
(8 Bit ASCII graphics use code page 437 or 850, Terminal Font)

I was given this 87cc genny, it was very clean & hardly used, but been garage
stored (some corrosion) for a few years. It was supplied by NuTools. In layout
it is very similar to my much bigger well-used MEDUSA SIP2300 2.3kW one.

 ﾜﾟﾟﾟﾟﾟﾟﾟﾟﾟﾟﾟﾟﾟﾟﾟﾟﾟﾜ                ﾛ  _________����_________  ﾛ Tube
ﾛ/~~~~~~Tank~~~~~~~\ﾛ               ﾛ/"        6L Tank       "\ﾛ Cage
ﾛ-------------------ﾛ      Fuel Tap ﾛ==========================ﾛ
ﾛﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾂﾂﾄ/~~~ﾛ      & filter\ﾛo~~~~~~~~~~~~~~~~~~~~~~~~oﾛ
ﾛ        Tap(0)ｳelecﾛ           STOPﾛ  [] on�_�ｱAｱｳ�Trip       ﾛ DC 1x 2Pin
ﾛChoke //       \___ﾛ         SWITCHﾛo off  ｳVｳｱCｱｳ-| DC      oﾛ AC 1x 13A
ﾛﾚﾄﾄﾄﾄｿ  /~~~~~\\.  ﾛPull           ﾛﾂﾄﾄﾂﾄﾄﾄﾄﾄﾄﾄﾄﾄﾂﾄﾄﾄﾄﾄﾄﾄﾂﾄﾄﾂﾂﾛ
ﾛｳIn- ｳ,' /~~~\/\\  ﾛStart          ﾛｳF ｳENGINE   ｳ�      ｳ  ｳｳﾛ
ﾛｳTakeｳｳ ｳ ( ) ｳ  ｳ ﾛ               ﾛｳA ｳ   oil(=)ｳ� ALT  ｳ  ｳｳﾛ
ﾛﾀﾄﾄﾄﾄﾙ \ \___/  /  ﾛ               ﾛｳN ｳ _____ｳ_ｳｳ�______ｳ__ｳｳﾛ
ﾛ     ﾚ' ﾚﾄﾄﾄﾄﾄｿ `ｿ ﾛ               ﾟﾜﾄﾄﾁﾄﾄﾄﾜﾙ   ~~~      ﾀﾜﾁﾁﾜﾟ
ﾟ"""""""""""""""""""ﾟ                 ﾟﾟﾟﾟﾟﾟﾟﾟﾟﾟﾟﾟﾟﾟﾟﾟﾟﾟﾟﾟﾟﾟﾟﾟ

STARTING ENGINE
It started on "easy start" ether spray OK. But the mixture was very lean and
need the choke partly on, to run for several minutes. (old Petrol?) I striped
down the carburettor and clean the main jet, then it was a little better.

PETROL TAP
There is next to no tank sump, so an unlevelled ground may result in fuel
starvation, despite there being quite a bit of fuel left. This not helped by
the "in the tank" hidden fuel filter and a fully "screwed in" tap!

                ﾚｿ
   Min Petrol   ｳｳ-Filter
        Level---ｳｳ           So make sure the tap in only "just" (2 turns)
 ﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄｿ__ﾜﾝﾞﾜ__ﾚﾄﾄﾄﾄﾄ  screwed into the tank, and then do up sealing Nut.
         Sump/ ｱｱｱｱ\O ring
Unused thread _ ﾝﾞ   & Nut
               _ﾝﾞ_
          ____/ __ \
Carb Pipe ____ (ﾞ_) )
              \_ﾞ__/
                ﾞTap

CIRCUIT
No circuit in the handbook etc. So I have reverse engineered this diagram.

   12V    F R O N T   240V AC            STOP
Charging  P A N E L    ﾚﾄﾄﾄﾄﾄｿ          ﾚﾄo\__
  ｳ+ -ｳ                E    _ｳ_         ｳbk bkｳ     Earth
 3A Bridge          ﾚN   Lｿ ///        _ｳ_    ｳ      _ｳ_
 Rectifier          ｳ     ｳ            ///    ｳ      ///
  ｳ   ｳ             ﾃMeterｴ                   ｳ
 4A*  ｳ             ｳ     4A                  ｳ
 Trip ｳ             ｳ    Trip                 ｳ
  ｳ gnｳ             ｳ     ｳ                   ｳ
  ｳgn ｳ 12u 450VAC  ｳbk rdｳ           Externalｳ Pointless
- � - � - - - - - - � - - � - - - - - - - - - ｳ - - - - -
  ｳ   ｳ   ﾚﾄｴﾃﾄﾄｿ   ｳ     ｳ  ﾚﾄﾄRﾄﾄｿ | Magnetoｳ Coil
  ｳ   ｳ   �ye ye�   ｳbn bnｳ  ﾃﾄｴ>ﾃﾄｴ |    ﾚﾄﾄ()))))ﾍﾍﾍﾍﾍﾍｻ
  ｳ0R4ｳ   ｳ 9R6 ｳ   ｳ 4R3 ｳ  ｳ     ｳ |    ｳ0R2  5k6      ｺEHT
  ﾀ())ﾙ   ﾀ(((()ﾙ   ﾀ(((()ﾙ  ﾀ(((()ﾙ |    ｳ        ﾚﾄ> <ﾍ1/4
   ===     =====     =====    =====  |   _ｳ_      _ｳ_ Plug
  Load    Exciter     Load    Rotor  |   ///      ///
        A L T E R N A T O R          |   F L Y W H E E L

ALTERNATOR EXCITATION
This is a "brush less alternator", with the excitation of the rotor
magnetically charged up each half cycle from circulating 90� out of phase
currents from the exciting 12uF capacitor. The rotor winding has a diode across
(and back emf R) it to maintain the current half a cycle after the kick (100 
times a sec). Excitation starting with the weak residual magnetic rotor field,
needs at high enough RPM (2000RPM) to overcome the rotor diode voltage drop.
About 10% of the power is needed for excitation of the rotor, hence alternator
fan must be kept efficiently working!

This system is more reliable than the DC to brushes and slip rings type, but it
does produce a slight kink in the load winding waveform and there is no
opportunity for voltage control other than engine RPM.

CHARGING (20V off load)
The genny came with the special DC plug and lead (- |), but the lead is short
and the trip was only 4A, and it trips all the time @ it's rated 5-6A charging
current, unless the RPM is well reduced. So I swapped the trip for 10A more
reasonable rated one.

The rectifier is only made from 4x 3A diodes inside the connector socket, with
no heat sink! To improve on this, I doubled up on the diodes, putting 4 more
1N5402 diodes on the copper side of the PCB and flow solder on the tracks to
improve heat dissipation. Note the current trip does not prevent blowing the
diodes on wrong battery polarity! So a 13A fuse in the charging lead will help
that!

AC REGULATION
This is a simple bob weight and spring RPM controlled engine governor, with the
alternator's capacitor self-exciting winding at 90� to the load winding which
gives some load to voltage compensation. On this generator these two features
alone seem to give quite good results.

  Load  Volts
    0W   240
  275W   237
  500W   235
  775W   230
 1000W   220
 1100W   215  Max Throttle!

IGNITION NOISE
This was quite high, noticeable on HF - UHF, as there are NO suppression parts,
despite the CE compliance markings etc. I did 3 things to get it down 30dB.

1/ Change the spark plug for a resistive type (measures between 5K-15K) it must
   be the same reach and ideally same temp type too.

2/ I added a non-inductive 5K6 in series with spring inside the spark plug cap.
   (ﾞﾟﾝ part unscrews)

                    .--------
                    | _==== < spike
 S=Shortened Spring | S ﾚ----
 R=5K6 bare ends    | R |
                    |ﾞﾟﾝ|
                    |   |
                    |   |

3/ Then I added a coax braid over the EHT lead and earthed it at the cylinder
   head. The braid is kept insulated other than at the cylinder head end!

           .-----================================----- EHT Lead To
           |nﾚ---================================ﾄﾄﾄﾄﾄ Magneto coil
           ｳ~ｳ  //        Added Coax Braid
          ﾚﾙ ﾀｿ ||
          ﾝｱｱｱﾞ || Braid earthed
Cylinder ﾄﾅﾄﾄﾄﾅﾄﾅﾅ to head bolt
Head      ﾀ~u~ﾙ    with a tag.
       Spark Plug


OTHER MODIFICATIONS
A/ Reduced the tappet clearance as it was quite noisy (rattly).
B/ As with other Gennys, I added an earth lead to clip on earth stakes etc.
C/ And also the 13A socket rattles any plug out a in a few mins, so a Bungee is
   needed and stretched over the plug to keep it in.

FAULT:- NO/LITTLE AC OUTPUT
I had problem with the excitation capacitor (large AC cap), after an 8 day
summer camp where it was heavily used. The moulded 12uF exciting capacitor
bolted into the alternator has dropped to only 3uF! I replaced it with 6x 2uF
450V AC fitted into the control panel and wired to the alternator.

FAULT:- PULL CORD TANGLE
1 of the 2 ratchet paws broke its plastic piviot hole. Repaired with glue &
pins supporting the broken peice. 

FAULT:-NO IGNITION SPARK
Poor mag coil, a common fault with kit left outside! Removed from outside of
flywheel, and dried out in oven @ just above >100�C. After testing OK, sealed
it with plastic ignition spray.


See my TECH buls "Regulating 12V Generator Output", "MEDUSA SIP2300 Generator
info", "MEDUSA SIP2300 Generator Repairs", "Cheaper Generators" & "Petrol
Generators for /P SSB"


Y Don't U send an interesting bul?

73 de John G8MNY @ GB7CIP


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