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The Lister Generator Project Page 7 The little genset has needed attention in one area, that of speed regulation. The engine has a built in governor that is supposed to maintain the rpm set by the operator and automatically compensate for changes in load. The governor set up works, but not too good. This is a common complaint from lister operators. After carefully studying the governor linkage setup and other articles written on the subject, I felt the closed loop performance could be improved by finding a different governor spring that had a similar but better rate constant. I made a search thought my junk box and came up with a nice looking candidate that if stretched far enough, had the same resistance as the stock spring. The balance in a governor system between rate and strength can cause the system to either under regulate as is the current situation, regulate perfectly, or hunt/oscillate never quite able to find a steady balance. Installing the spring had the immediate latter effect. The engine would alternate between full throttle and idle every second or so. The spring was strong enough, but lacked the rate constant to match the rate of the internal fly weights. After many trial and error attempts, I zeroed in on the perfect setting. I did this by moving the spring attach point ever closer effectively shortening the spring, then re-adjusting the attach point until the perfect length was attained. Prior to this modification, the engine would vary RPM 10% from full load to idle. This translated to 55 Hz - 65 Hz if no tweaking adjustments were made by me. This was unacceptable as the loads would frequently change as air conditioners cycled on and off. This set the house lights dimming and computers squealing and wife-a-bitching. With the new spring setup, I was able to achieve a 1.5 Hz difference from no load to full load, however the system was prone to occasional hunting so I clipped off two more turns of the spring to increase damping. The final setup shown below, is a 21 turn spring, conveniently able to reuse the existing attach stud, and it operates with a spread of 2.2 Hz from no load to full load. I set the speed to 61.2 hz at no load and it drops to about 59 Hz at full load.
The new spring in action along with the original spring (small/longer) and a spare I made hanging next to it for comparison. All is well! |
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"Sadly,
artificial intelligence will probably never be a match for natural
stupidity." |
