Governor drift - Help please

[BruceM]

Horsepoor-  better check with the manufacturer about this unit's stability with very low speed engines.  It may not be stable for our 650 rpm engines. 
Best Wishes,
Bruce

[Horsepoor]

Good point, but as I think about it, if this is an issue I might be able to use the lever arm on the actuator to reduce the response by placing the linkage closer to the pivot point. I do t know, just thinking about the analog governor in my quest for true listeroid euphoria. Before I buy, I will inquire, I like the ability to regulate engine speed directly from the ST generator head by measuring frequency. If it is less than $200, I will buy one and test it.

[BruceM]

The problem with our low speed engines without the heavy SOM flywheels is that there is considerable variation in rotational speed, which shows up as a variation in generator speed (with a 10 Hz period).  The speed is slowest during the compression stroke, and highest after the power stroke.

If the governor can be "detuned" enough to ignore this variation, then all is well.  But for normal 1800-3600 rpm gensets, this level of insensitivity would allow very poor speed regulation.  It would be unusual for an off the shelf governor to handle a 650 rpm engine, unless it has been specifically designed to do so.  (Thus my suggestion that the manufacturer be contacted.)

In one  video linked to from this forum of a very professional  setup, a modern commercial electronic governor was applied to a Listeroid.  What resulted was constant 10Hz thrashing of the fuel rack.  While it worked, I expect the fuel rack will be worn out rapidly.  

[Horsepoor]

Interesting, and good points. To offset this, I am using a ST 7.5 with a very heavy cast iron two speed sheave spinning at 1800 rpm. This 70 lbs of rotating mass eliminated my light flicker and might be enough to smooth out the power pulse onto the governor speed control system. What do you think?

[BruceM]

Horsepoor, It seems like your generator's rotating mass at 1800 rpm has done the trick.   I hope it will solve the governor stability issue, too.

Bruce

[Horsepoor]

I must admit, with the help of others and this forum, I have solved all my significant issues. Now I just tinker to see how much lipstick I can put on my pig. I've achieved less than 2 Hz drift but I like to tinker, thus my interest in the analog governor if it is cheap enough.

[BruceM]

I tried the Home Depot  759 541 spring today on my older Metro 6/1. Alas, it is a bit too soft and hunts badly. This spring, while close, is not a perfect match for all Listeroids.

I added a second even softer spring (one of a selection I got at ACE for my first round of spring fiddling) and now it's better than my old 2 spring setup.  No load of 62Hz, and fully loaded 59.7 Hz. No hunting or instability with all the various loads I could try.  My old setup had just slightly worse range (loaded 59.5), but also for some loads it would hunt a little.

I suspect I could accomplish the same thing by shortening the Home Depot spring, but I didn't try that.

My rule of thumb for spring fiddling- if it hunts, add another spring, or switch to a stiffer spring.  If it varies too much with load, go to a softer spring.

My thanks to Horsepoor and Veggie !

[Tom Reed]

Bruce, see my post on the Lister board about this subject. IIRC I got 1.5 hz with a 7/16 x 2.5 x .043 homodpt spring.

[Ronmar]

quite a few variables here to proclaim a single spring is the be-all, do-all fix,  the biggest of which is flyweight mass. I highly doubt all these engines have the same weight flyweights...  After cleaning up the linkage pivots and taking out all the slop of that very sloppy yoke with a VERY soft spring), I am very happilly running the main governor spring it came with. Unless the governor spring rate is matched to the possible flyweight it must counter, it can hunt.  Excessive slop or binding of the yoke can also cause hunting as it will take a larger movement force(change in RPM) to cause the governor to move the rack and compensate.   Taking the slop out is probably the biggest single improvement you can make.  Being unable to take all the slop out of the yoke was impractical, so I used a VERY soft spring from an old tape recorder or CD drive, to gently hold the slop at one end of it's travel without causing binding. This single thing had the biggest effect on stability of any thing I did.  It is very simple to experiment with using a rubber band.  My ultimate fix would be to use a weed-eater throttle cable in place of all the linkages and add a very soft spring connected to the opposite end of the rack to keep the cable in tension and to close the throttle and shutdown if anything should come apart...

I am happilly getting +/- 2Hz from no load to full load.  62 droops down to 58.  I think this is fantastic for an anchient governor design.  2Hz is absolutely phenomenal IMO...  Check your utilities advertised specs for frequency.  +/- 5Hz is probably pretty typical, although they typically do far better than that... 

[Tom Reed]

Yet, nothing was done to remove the slop on the linkage on my machine and with just a spring change now have 1.5 hz response.

[Ronmar]

Well you must have a fairly tight yoke and linkage then.  The time required to take up all the slop in the linkages and IP is the main cause of lag/overshoot.  It can also induce a type of random hunting if the yoke is really bad as the rack will move a little on it's own causing uncommanded throttle changes that the governor will then try to sloppilly regulate:)

[Tom Reed]

Well I don't know how tight the linkage is compared to others as I've only had my hands on one other roid. There is a fair amount of slop in it though.