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G8MNY > TECH 16.07.12 21:24l 195 Lines 9177 Bytes #999 (0) @ WW
BID : 51240_GB7CIP
Read: GUEST
Subj: NORTHERN 650W 2 Stroke Genny
Path: IZ3LSV<IK2XDE<ON4HU<CX2SA<GB7CIP
Sent: 120716/1808Z @:GB7CIP.#32.GBR.EU #:51240 [Caterham Surrey GBR] $:51240_GB
From: G8MNY@GB7CIP.#32.GBR.EU
To : TECH@WW
By G8MNY (Updated Jul 12)
(8 Bit ASCII graphics use code page 437 or 850, Terminal Font)
I bought very clean hardly used non working 63cc one at a junk sale, & "it
worked OK last year" I was told! It seems identical to the Wolf, Pro User &
KINGAVON versions.
On looking into the non-running, there was no intake "suck". This is a 2 stroke
with an angled engine & the carburettor ported into the crank case with a reed
valve, rather than an upright engine with bottom edge of piston valve intake.
Oil Measuring
Filler Cap Ü Handle ÜÜÜÜÜÜÜÜÜÜÜ
Ú===¿ Û ÞÝ Ú===¿ ÞÝ
/~~~~Tank~~~~~\ /~~~~~~Tank~~~~~~~\
----------------- ---------------------
Mains|ÀÄÄÄÄÄÄÄÄÄÄÄÄÄÙÝ DC|~~~~~³~~~~~~~~~~~|On/off
|(0)= _-~\ÞÝSilencer |MAINS³ choke []|
Choke´Tap Start\\\\\\Plg Ý ³ ø ===== |\
|ÄÄÄÄ¿pull~\\Cyl\ Þ³-----------------| |Pull
Air |Carb³,\/~~~\\_-~ Alternatorݳ Air |ø|Start
Box &| ³ ³ ( ) ³ ³ß Þ³ Filter | |
FilterÀÄÄÄÄÙ\ \___/ / Ý_________________|/
Ú'ÚÄÄÄÄÄÄÄÄÄ¿'¿ ÀÂÄÂÙ ÀÂÄÂÙ
""" """ """ """
ENGINE FAULTS
Checking the ignition there was a weak spark OK & there was compression so I
tried putting petrol/ether spray into the crankcase through the reed intake
valve, but the engine still did not fire. So I put took the silencer off
(needed painting anyway) & put spray through the exhaust port, this did give a
bang on turning over, so the ignition & timing was OK etc.
The fault was eventually found to be a popped out crankshaft bearing oil seal
rubber, between the engine & the alternator. This may have happened if there
had been backfires in the crankcase or just a lot of compression, as there was
non-of the usual spring circlips in grooves to hold them in place in this
design!
To get to the fault, I needed to split the alternator off the engine (3 outer
bolts) & remove silencer & gently levering off the end casing. A long bolt
through the alternator shaft holds it on to the tapered crankshaft, this was
the first problem & a smart tap the socket set freed this OK. Then on the lose
bolt a sharp tap with a hammer to free the crankshaft off the alternator rotor.
Now was the problem of fixing the hardly worn air seal back in place so it
would not spin. Initially I used instant gasket sealant, but eventually I added
2 right angle metal pieces to held in be drilled & tapped screws in the
available cast lugs around the bearing, to lock the seal in place.
ALTERNATOR
± ±
± ±
TAPERED ±ÝÞ±
ENGINE SHAFTÞÝÞÝ SCREW &
ÅÅÄ¿ ÛÝÞÛ ÚÄÅÅÄ right Angle
ÄÄÄÄÄÄÅÅ¿³ ÛÛÛÛ ³ÚÅÅÄÄÄÄÄÄ
Web Tap³³ ÛÛÛÛ ³³Tap Web
hole³°°>ÛÛÛÛ<°°³hole °°> Air tight Oil Seal
³(o)ÛÛÛÛ(o)³ (o) Ball race bearing
ÄÄÄÄÄÄÄÄÁ ÛÛÛÛ ÁÄÄÄÄÄÄÄÄ
CRANK CASEÛÛÛÛ
Also I noticed the Alternator Fan was loose, this removes the 100W or so of
heat, & blows it over the exhaust, & it was able to free wheel! Some 2 part
glue fixed that OK, & re-fixing the locating lugs etc.
Long Bolt
Bearing [~~]
[(o)±Þݱ(o)]
±ÞݱSHAFT
ÚÂÂÄÂÄÂÄÂÂÄÄÄÄ¿±ÞݱÚÄÄÄÄÂÂÄÂÄÂÄ¿ALTERNATOR
³³³ ³ ³ ³³ ³±Þݱ³ ³³ ³ ³ ³³³FAN
³³³_³_³ ³³_ _ ³±Þݱ³ _ _³³ ³_³_³³³
³ ³_glue/±Þݱ\glue_³ ³Lug
²²² ±Þݱ ²²² inside
ÛÛÛÛÛÛÛÛÛÛ±ÞݱÛÛÛÛÛÛÛÛÛÛ
ÛÛÛÛÛÛÛÛÛÛ±ÞݱÛÛÛÛÛÛÛÛÛÛROTOR
CIRCUIT
Not having the handbook etc. I have reverse engineered the diagram...
12V 240V AC STOP
Charging ÚÄÄÄÄÄ¿ ÚÄo\__
+³ ³- E _³_ bn³ ³bk
3A Bridge N L /// ------------
Rectifier ³ ³ |Electronic|ÄÄÄÄÄÄÄ¿or
³ ³ (155V)³ ³ | Ignition | ³
7A ³ 15u 450V³ 2.3A | Module | 0.2ê³2k2
Trip ³ ÚÄ´ÃÄ¿ ³ Trip ------------ ÚÄ()))))ÄÄ¿
³ gn³ ³ ye³ ³ ³ ³ ³ ³ ³ ===== ³
³gn ³ ³ye ³ ³bk rd³ rd/wh³ bn³ bk³ ³ Coil ³EHT
_³_ _³_³ _ _³ _³_ _ _³_ _ _ _ _ _ _ _ _ ³ _ ³_ _ ³_ _ ³ _ _ _ _ ³lead
³ ³ ³ ³ ³ ³ | 34ê|( )| ³ ³ ³
³.3ê³ ³3.2ê³ ³ 6.8ê³ ROTOR | Timing|( )| ³ ³ Plug ³
À())Ù À((()Ù À(((()Ù Ú(((()¿ | Pickup ÀÄÄÄÁÄÄÄÄÁÂÄÄÄÙ ÚÄ> <5kÙ
==== ==== ===== ³=====³ | & Magneto 730ê _³_ _³_
ÃÄ´>ÃÄ´ | /// ///
A L T E R N A T O R ÀÄÄRÄÄÙ | C R A N K C A S E
ALTERNATOR EXCITATION
This is a brushless alternator with the excitation of the rotor magnetically
charged up each half cycle from circulating 90ø out of phase currents from the
exciting capacitor. The rotor winding has a diode across it to maintain the
current, half a cycle after the kick. Excitation only starts at high enough RPM
(2000RPM) to overcome the diode voltage drop loss with the residual magnetic
rotor field. This system is more reliable than the brush type, but does produce
a kink in the load winding waveform & there is no opportunity for voltage
control other than the RPM.
CHARGING
As I did not have the DC plug & lead, I made a plug (- |) from 2 brass strips,
poked these into socket & through cardboard, to form the plug's mould base, &
fitted a cardboard tube. Made the lot into a good mould, & with the petrol tank
removed up end the generator to get the socket level, spay oil/grease into the
socket holes & refit the plug strips & mould. Mix up resin & hardener with some
fibber glass to strengthen the plus base. pour in & tamp down. When set remove
the plug, cut off the cardboard mould, Grind/file off the resin into the wanted
shape, Solder on the new lead to the brass strips noting +/- & tape the lot up
in rubber amalgamating tape, this finishes the plug.
Although there is a 7A trip (12A to activate!) before the bridge rectifier,
it is only made from 4x 3A diodes in the connector box with no heat sink. To
improve on this, I cleaned off all the copper track paint & flowed a thick
layer of solder all over it to act as heat spreader. I also doubled up on the
diodes putting 4 more on the copper side of the PCB. Note the current trip does
not prevent blowing the diodes on wrong battery polarity, a 13A fuse in the
charging lead will help that!
In practice though on a good battery the charging current is only 3-4A, but
enough to boost a flat car battery in a few mins so you can crank the car over.
MODIFICATIONS
To improve the VHF/UHF ignition noise, I have added a lead a loose braid
earthed at the plug screened cap.
________ Added loose Coax Braid
Metal ³ÜÜÜÜÜÜÜ_================================_____ EHT Lead To
Cover ³Ý|n|ÜÜÜ-================================----- Magneto coil
suppressor ³Ý³~³Þ|~~~
plug cover³ÚÙ À¿³
_ ³³~~~³³
CylinerÁÄÁÄÄÅÄÄÄÅÄÄÄ
À~u~ÙSpark Plug
To improve the voltage regulation, I applied my current solenoid feed forward
modification. This was easily done, by adding a small solenoid (e.g. from an
old VCR) rewound with a few turns of suitably insulated & thick enamelled
copper wire, that takes the 230V full load current. With a single screw it is
mounted firmly on the engine webbing by the speed setting adjuster. The
solenoid piston is linked up to aid the speed setting spring. The length of the
thick link wire is critical so that the piston just goes fully home at full
throttle, & if less compensation is needed the wire can be bent slightly to
adjust the effect.
__
CRANKCASE BOB ³()³AXLE
WEIGHT GOVERNOR³ ³
³ ³ SPRING ___ SPEED
³ o³ÄÄÄ,/\/\/\.ÄÄÄÄ[___[ADJUSTOR SCREW
³ o³ Link Wire ÚÄÄÄÄÄÄÄÄ¿
³ o³============²²³SOLENOID³
³ ³ BOOST__\ ÀÄÄÄÄÂÄÂÄÙ Alternator
³ ³ PULL / bk³ ³bk Load
³ ³ Neutral Neutral
³ o³_________
ÀÄÄÙ Throttle link
N.B. Solenoid pull is proportional to:-
1/ the load current squared,
2/ the number of turns,
3/ the location of the movable iron piston slug,
With this modification a good 800W 230V was available under resistive lamp
load tests from this small generator.
CONCLUSION
Although 2 stokes are not the best engine for efficiency etc. & fuel oil mix is
needed etc, their simplicity & reliability if maintained (clean carburettor &
muffler) does give a simple lightweight power source. The noise of this one
changes from poor putting misfires on no load, to a steady 50Hz hum on higher
loads. N.B. if the engine is hot it can be difficult to start, ether spray in
the air inlet does help!
So a lot of work & really good genny for /P I hope.
See my TECH buls "Regulating 12V Generator Output", "Cheaper Generators" &
"Petrol Generators for /P SSB"
Y Don't U send an interesting bul?
73 de John G8MNY @ GB7CIP
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