G8MNY > TECHNI 05.10.21 09:20l 161 Lines 6888 Bytes #999 (0) @ WW
BID : 48699_GB7CIP
Subj: PERFORMANCE POWER 1kW Genny
Sent: 211005/0712Z @:GB7CIP.#32.GBR.EURO #:48699 [Caterham Surrey GBR]
To : TECH@WW
By G8MNY (Updated Aug 21)
(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.
▄▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▄ █ __________________ █ Tube
█/~~~~~~Tank~~~~~~~\█ █/" 6L Tank "\█ Cage
█-------------------█ Fuel Tap █==========================█
█────────────┬┬─/~~~█ & filter\█o~~~~~~~~~~~~~~~~~~~~~~~~o█
█ Tap(0)│elec█ STOP█  on°_°▒A▒│°Trip █ DC 1x 2Pin
█Choke // \___█ SWITCH█o off │V│▒C▒│-| DC o█ AC 1x 13A
█┌────┐ /~~~~~\\. █Pull █┬──┬─────────┬───────┬──┬┬█
█│In- │,' /~~~\/\\ █Start █│F │ENGINE │ │ ││█
█│Take││ │ ( ) │ │ █ █│A │ oil(=)│ ALT │ ││█
█└────┘ \ \___/ / █ █│N │ _____│_││______│__││█
█ ┌' ┌─────┐ `┐ █ ▀▄──┴───▄┘ ~~~ └▄┴┴▄▀
It started on "easy start" ether spray OK. But the mixture was very lean & need
the choke partly on, to run for several minutes. (old Petrol?) I striped down
the carburettor & clean the main jet, then it was a little better.
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 & a fully "screwed in" tap!
Min Petrol ││-Filter
Level---││ So make sure the tap in only "just" (2 turns)
───────────┐__▄ŢŮ▄__┌───── screwed into the tank, & then do up sealing Nut.
Sump/ ▒▒▒▒\O ring
Unused thread _ ŢŮ & Nut
____/ __ \
Carb Pipe ____ (Ů_) )
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 ┌─────┐ ┌─o\__
│+ -│ E _│_ │bk bk│ Earth
3A Bridge ┌N L┐ /// _│_ │ _│_
Rectifier │ │ /// │ ///
│ │ ├Meter┤ │
4A* │ │ 4A │
Trip │ │ Trip │
│ gn│ │ │ │
│gn │ 12u 450V │bk rd│ External│ Pointless
- Ý - Ý - - - - - - Ý - - Ý - - - - - - - - - │ - - - - -
│ │ ┌─┤├──┐ │ │ ┌──R──┐ | Magneto│ Coil
│ │ Ýye yeÝ │bn bn│ ├─┤>├─┤ | ┌──()))))══════╗
│.4ŕ│ │ 9.6ŕ│ │ 4.3ŕ│ │ │ | │0.2ŕ 5k6 ║EHT
└())┘ └(((()┘ └(((()┘ └(((()┘ | │ ┌─> <═1/4
=== ===== ===== ===== | _│_ _│_ Plug
Load Exciter Load Rotor | /// ///
A L T E R N A T O R | F L Y W H E E L
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 (& 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
This system is more reliable than the DC to brushes & slip rings type, but it
does produce a slight kink in the load winding waveform & there is no
opportunity for voltage control other than engine RPM.
CHARGING (20V off load)
The genny came with the special DC plug & lead (- |), but the lead is short &
the trip was only 4A, & 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 & flowing lots of 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!
This is a simple bob weight & 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.
1100W 215 Max Throttle!
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 same reach & ideally same temp type.
2/ I added a non-inductive 5K6 in series with spring inside the spark plug cap.
(Ů▀Ţ part unscrews)
| _==== < spike
S=Shortened Spring | S ┌----
R=5k6 bare ends | R |
3/ Then I added a coax braid over the EHT lead & earthed it at the cylinder
head. The braid is kept insulated other than at the cylinder head end!
.-----================================----- EHT Lead To
|n┌---================================───── Magneto coil
│~│ // Added Coax Braid
┌┘ └┐ ||
Ţ▒▒▒Ů || Braid earthed
Cylinder ─┼───┼─┼┼ to head bolt
Head └~u~┘ with a tag.
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 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 its was heavily used. The moulded 12uF capacitor bolted in
the alternator has dropped to only 3uF. I replaced it with 6x 2uF 450V AC
fitted into the control panel & wired to the alternator OK.
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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