Email from Zimbabwe, Governors


Hi George,

I have a Changfa engine 1110 engine running a ST generator head , In the last few weeks I have replaced my pulley on the gen head and engine with high quality pulleys , at the same time I changed the ratios and my engine is running at a lower rpm for engine longevity , the engine now runs at 1750 rpm about when my gen set is at 1500 rpm . My question is would this affect the engine governor and cause it to be lazy because the governor spring might be to strong now that the engine is running at a slower rpm , we use the generator to pump water when we go of line which in zim is every day , now on start up of the pump the voltage dips about 40 volts from the set volt age of 400 on the 3 phase to a voltage of 360 . This voltage is acceptable to the pump tolerances of 10 % increase or decrease , I am only concerned that the engine now takes time to reach the set speed because the governor is slow to react and that when the load is taken off and the generator now is running at a lighter load the engine is increasing in speed and then decreasing in speed in a slow noticeable cycle , until we start the pump again to fill the water bowsers . this is a cycle that is done about twenty times a day , as we fill bowsers during the work day .

How would I be able to adjust the governor or replace a spring that will give me a bettor response to the engine. When we use the gen to power the homestead and there is no switching on or off of pumps and the load stays constant and the engine runs very smoothly and there is no change in rpm of the engine.

Other than this , these engines and generator heads are in my opinion indestructible and considering the cost of what I paid , I will not hesitate to buy again , they are easy to maintain and fix in any situation and I have never gone without power because some electronic part has failed .

George’s Reply:

Hannes, always good to hear from Zim! You email addresses a classic concern. I have written pages on the topic that are likely search able with ‘Utterpower governor’.

The 1110 is a fairly standard Asian workhorse, Changfa is a better built engine from experience, but friend warns me that counterfeiting the name or brand is a common thing on the mainland!  Quality ranges from very good to JUNK.  Some manufactures make them to sell,  some make them to use, and to this point, the Changfa company appears to make better stuff. There are a lot of things that can be left out of this design, oil pressure relief valves, bushings on the counter shaft and main shafts VS roller/ball bearings, plastic parts that quickly fail VS the traditional and more costly metal parts.  Another concern I have seen is assembly by the unskilled, heads not surface ground properly, water leaks developing in the head gasket area. A quick inspection, and then improving this surface with wet or dry paper on a dead flat surface is a good precaution and eliminates a common cause of failures in the bush. Another thing to watch on these engines is the single bolt that fastens the valve cover, when not properly torqued, these come loose, the lube oil leaks out till the engine destroys itself. It’s not so much about the design, it’s knowing what you need to look for and knowing it was built right and addressing the small and important stuff like checking rocker arm alignment, and assuring you properly torque down the single stud on the valve cover!  Some engines have two studs, a much better idea.

Same goes for the ST, they are anything from reliable to junk, and there lies the problem.

Back to your Governor Issue

If we look at the typical governor, it’s little more than a tug of war contest between a fly weight and the spring, but in this case we have a throttle rack right in the middle that gets drug back and forth until equilibrium is reached (load dependent).

When we choose to run at a low ‘set speed’ we handicap the flyweights as they can no longer develop the same ‘tugging force’. In order for the contest to be fair, we must also handicap the spring.  This is best done by fitting a weaker spring and studying the voltage droop or RPM drop when your load is placed across the Generator. try a selction of weaker springs and increase tension till you get the best results.

After studying the Bush generator for years and the typical failures, I think it is wise to invest your time in tuning the governor to maintain speed best it can and then address voltage droop, your goal is to provide acceptable droop, not to provide a voltage to the nearest decimal point.  If you can do this without a voltage regulator, you have a better situation in small bush power generation because many if not most of the voltage regulators in this class of generator are poorly implemented and misunderstood by the generator operator. One thing for certain, bush generators only fail when you need them most.

As I often say, opinions vary. When you analyze an opinion, attempt to quantify the amount of hands on experience of the Author.  I love some of the posts I see on DIYer forums. “I just opened the crate this morning , and I can tell you this generator is a masterpiece of engineering! I called the manufacturer this AM and ordered 100 more and I’ll be selling them, send me an email and let me know how many you want”.

Sad to say but the game has now become far more complicated. We now live in a world of uncertainty, what you ordered last month may have no resemblance to what you receive next order. What counts is the track record of your supplier and his Warranty.

Oh yes… you knew I couldn’t stay on topic, but you’ve come to expect that haven’t you ??  

All the best,

George B.

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