Hi Tys,
Another thing comes to mind... And something that I have a little experience with in the "intelligent charger/inverter" side too... If you have had a laugh and a read at the "Listeroid Chronicles" thread, buried deep inside it is a recount of a bit of time I spent playing around with pulley ratios and engine speeds. Granted, my roids are rated to up to 1000RPM, but I dont run them at that - I have tried to keep them at more "traditional" 500-850 RPM speeds...
This is what I found:
I have a few "Intelligent" APC UPS's dotted around the premises - they are capable of being set as to input line power quality sensitivity - this boils down to a whopping 3 choices that you can set them to - Low/Medium or High Sensitivity as to input line power quality..... I have set all of them to being as tolerable as they can, ie Low sensitivity, of the incoming line power quality - This sensitivity is regarding input frequency as well as input voltage variations...
What I found was that with the roids running slowly - 500 to 600 RPM, the frequency variations due to the suck/squeeze/bang/blow of the big 4 stroke cycle drove the charger units nuts - they couldn't cope with the short interval frequency differences and rejected the incoming power as being unstable, subsequently shutting down the chargers until things in the input mains side cleaned up... This was with or without AVR's installed, 2 different alternators, 2 different roids, 2 different sets of flywheels, even with one roid having a double set of flywheels. The power was usable for everything else, pumps, fridges, aircon, tv's stereos etc... no problem there... just the damn inverters complained...
I then upped the revs on TM1 - and eventually settled on around 750RPM as giving about the lowest RPM with adequate quality - TM1 has "Stover" type wheels, a single set. He can go down to about 700RPM without the UPS's complaining about power quality (From a frequency POV).. Now with TM2 I started playing about quite a bit - Eventually installing 2 sets of similar wheels and reducing the revs and changing the pulley ratios until the UPS's started complaining - Then upped the revs by 50 to 650RPM and have left him at that. Bear in mind, TM2 has 2 sets of Stover wheels on him - Plenty of rotating mass to keep things smooth. (Or so I thought!!)
Regarding governor springs et al, I have been there, done the mods, smoothed things out and still run into stability problems due to the above. The couple of Hz/Volts up or down over the long term while operating does not seem to make a big difference - the most notable effect I have found is in the short term frequency differences over a few cycles... I have not been able to do much about it, but did improve matters a bit (with other downsides though) by reducing compression ratios and retarding injection timing... Ultimately, and after many 100's of hours of running the things at varying speeds, I have come to the conclusion that on the single cylinder beasts, there is not much more that can be done to clean up the short term frequency variations except by upping the revs a bit, or increasing rotating mass - Although it has been done before, I am not wild about it, you can add a flywheel to the alternator side of things to smooth things out a bit...
Before you go and wind open the governor and start changing pulley ratios, ensure your wheels are capable of taking the extra energy....
Hope this helps...
Regds
Ed