Author Topic: Ashwamegh 25/2 :the saga continues  (Read 1065 times)

32 coupe

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Ashwamegh 25/2 :the saga continues
« on: August 05, 2018, 05:24:52 PM »
I just can't get this thing to produce power.

I sent the cam to Butch who installed the new weights and see no change.

The engine will pull about 1600 watts but if I load it with another 1000 watts it just won't
do the deed.

With  no load I set the speed to 720 engine rpms. That will give me 1800 at the gen head.
I see 120 volts at 63 HZ. With a 1600 load it does 117 volts @60 HZ.
But another 1000 watts and the voltage will fall to 93 volts @ 54 HZ.

The engine is not "working" at this speed the governor just won't "pick up".

I tried several springs and spring combinations.

I am thinking a larger gen pulley to bring the engine rpms up to about 800 or so.

The engine has always run very close EGT's but I see a slight difference now. I guess this is do
to the new cam lobe on the #1 cylinder. I haven't reset the timing on that side yet but I don't believe
it is enough to cause the problem I am having.

I am open to ideas.

Gary

« Last Edit: August 05, 2018, 05:27:08 PM by 32 coupe »
Metro 6/1 turning a ST 7.5 KW gen head
Changfa 1115 turning a ST 15 KW gen head
Ashwamegh 2/25
John Deere 110 TBL
New Holland TC 30

"I was sitting here reading this thinking what an idiot you are until I realized it was one of my earlier posts !"

BruceM

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Re: Ashwamegh 25/2 :the saga continues
« Reply #1 on: August 05, 2018, 06:34:03 PM »
Have you checked for wrong governor weights (light high speed types) or binding in governor?


32 coupe

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Re: Ashwamegh 25/2 :the saga continues
« Reply #2 on: August 05, 2018, 07:15:56 PM »
Bruce,
Yes, the cam went to Butch for new weights....they are just a little heavier than "stock".

No binding in linkage.  The engine starts and runs great.  It just won't  pull a load.

Gary



« Last Edit: August 05, 2018, 07:17:46 PM by 32 coupe »
Metro 6/1 turning a ST 7.5 KW gen head
Changfa 1115 turning a ST 15 KW gen head
Ashwamegh 2/25
John Deere 110 TBL
New Holland TC 30

"I was sitting here reading this thinking what an idiot you are until I realized it was one of my earlier posts !"

BruceM

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Re: Ashwamegh 25/2 :the saga continues
« Reply #3 on: August 05, 2018, 07:31:35 PM »
What happens when you manually move the rack?  Is there plenty of authority and power there?  If so, it still comes back to governor.  Is exhaust looking OK? (Wondering about injection, valve timing.)  If valve timing is off a tooth , from a misplaced idler gear, power can suffer but it will otherwise run just fine and exhaust looks fine (until heavily loaded).  I'm assuming the same problem could happen on a twin. Don't ask how I know. ;0



32 coupe

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Re: Ashwamegh 25/2 :the saga continues
« Reply #4 on: August 05, 2018, 08:35:22 PM »
The linkage works with no binding or problems.

The engine starts right up and runs to speed with no smoke and a nice clear exhaust.

I can easily run the throttle up with a slight touch of a finger on the linkage with no change in
the exhaust

I am 100% convinced it is the govenor that is why it went to Butch for the weight change and "check out".

I am thinking pulley change for more engine rpms (720 to 800) or one of those "screen door" return springs.

At this point my 6-1 will put out more HP !

Metro 6/1 turning a ST 7.5 KW gen head
Changfa 1115 turning a ST 15 KW gen head
Ashwamegh 2/25
John Deere 110 TBL
New Holland TC 30

"I was sitting here reading this thinking what an idiot you are until I realized it was one of my earlier posts !"

BruceM

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Re: Ashwamegh 25/2 :the saga continues
« Reply #5 on: August 05, 2018, 09:28:29 PM »
Yep, my older 6/1 at 5600 feet elevation will pull out more watts, too.
Seems like something might be off in the governor assembly inside the case, since your linkage checks out OK.  A softer spring would help with diagnosis...too soft should hunt.  I hope Butch will pop in here and help get you sorted. 



2Ton46

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Re: Ashwamegh 25/2 :the saga continues
« Reply #6 on: August 05, 2018, 10:59:13 PM »
If I'm reading correctly, when you have the larger load on that is pulling down to an unacceptable speed, you are able to touch the rack with your finger and bring it up to speed with that load still applied.  If so, this condition is similar to what I have had going on with my 12/2. 

I've been working at the problem some recently and have gotten a much better response by adding an additional spring in series with the one it came with. In my case, the short spring when adjusted to give my desired rpm, would rapidly loose tension as the rack opened. In fact, it would be pretty much not doing any tension as the rack got to the full open position. This led to the rack not opening as the spring tension would drop off and stop overcoming even the now slowing weights, and would result in a large speed loss when my compressor cycled on that sometimes wouldn't even recover to set point by the time it cycled off again.

By adding in a longer spring I was able to greatly reduce the force dropping off as the rack opened. For experimental purposes I used a piece of wire around the bottom of the oil pump as a temporary and adjustable anchor. As an initial setting I tied the spring in series with the other one, after unhooking it from the peg on the block.  I then pulled the pair tight with the wire until the end of the original spring lined up with the peg again. This gave approximately the same tension on the arm as before, but the force no longer drops off as rapidly (or increases as rapidly) as the arm moves.  This gives a nice steady pull to work against the weights over the whole travel of the rack. The downside is speed adjustment now requires more change in length than before.

Boy what a difference! I've gone from badly over damped to a slightly under damped control situation. Upon startup it will slightly overshoot the speed set point and then settle in as it slows to speed. With no load, it seems to be slightly hunting as the rack is moving around a little, but it doesn't by sound or show up in my cheap tach. With a load, it maintains set point beautifully. Now when the compressor cycles on, the speed drops slightly but its back to set point within a second or two. It's fun to watch the rack open up and then back off slightly again when the compressor cycles on and it recovers the speed and gets back to maintaining rpm with the new load. The rpm change is is now fairly small and is perceptible by ear when the compressor loads...but recovers quickly and sounds more like its not lost speed and recovered but is just thumping a little harder suddenly.  When the compressor unloads, its even quicker to get back to set point as it speeds up with the loss of load and settles back.

mikenash

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Re: Ashwamegh 25/2 :the saga continues
« Reply #7 on: August 06, 2018, 02:09:37 AM »
There are anecdotal stories of folks using "fly-screen door" springs for the same reason?

38ac

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Re: Ashwamegh 25/2 :the saga continues
« Reply #8 on: August 06, 2018, 12:14:22 PM »
This is one of those deals where being there beside it would allow for it to be quickly fixed but diagnosing from afar gets pretty wordy.
First question which has all ready been asked.. and if you answered it I missed it, sorry. When the engine is loaded to the point of slowing down can you manually push the rack open and bring it back up to speed?  This must first be checked and answered to get you headed the right direction.

That being said and assuming it will indeed speed back up when you run the racks by hand.  Then you next check the linkage adjustment. Here is how you do that https://youtu.be/N4otiDKDiyk

The high speed engines have a very stiff spring and it will not control the engine very well when it is slowed down as 2ton46 very well explained.  The next step would be to replace it with a lighter spring. May I suggest the one from your 6/1? save a trip to town and if it shows improvement would mean you are headed the right direction. 
There is no black art to spring selection. the longest spring you care to fit that has enough pull to give the required RPM without the engine hunting (speeding up and slowing down on its own)  is the one that will give the best regulation.


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glort

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Re: Ashwamegh 25/2 :the saga continues
« Reply #9 on: August 06, 2018, 12:45:20 PM »
the longest spring you care to fit that has enough pull to give the required RPM without the engine hunting (speeding up and slowing down on its own)  is the one that will give the best regulation.

I'll give this a go on the Kohler fitted to my tractor Mower. Motor runs like a dream, smooth and not a puff of smoke but really hunts at idle. I tried changing the spring position in the linkage arms but only made things worse.
I'll try pulling it through and bending it to tighten it up a bit and see how that goes.

Thanks for the tip.

32 coupe

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Re: Ashwamegh 25/2 :the saga continues
« Reply #10 on: August 06, 2018, 01:45:54 PM »

The first spring I tried was so light the engine would hunt.
I then went to several others including one off my 6/1.
No luck.

I stopped this morning and bought a few more springs from a local
supply shop and will give it another go this weekend.

All the linkages, pumps and injectors are fine and working properly so
I am sure the spring is my problem.


Thanks for everyone's input. I will report back next weekend.

Gary



Metro 6/1 turning a ST 7.5 KW gen head
Changfa 1115 turning a ST 15 KW gen head
Ashwamegh 2/25
John Deere 110 TBL
New Holland TC 30

"I was sitting here reading this thinking what an idiot you are until I realized it was one of my earlier posts !"

BruceM

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Re: Ashwamegh 25/2 :the saga continues
« Reply #11 on: August 06, 2018, 02:35:24 PM »
Gary-   I use two springs in parallel, one that was a hunter, plus a second spring in parallel that was too soft to be useful alone but combined with the hunter works well.  You don't have to find the perfect single spring.




mikenash

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Re: Ashwamegh 25/2 :the saga continues
« Reply #12 on: August 07, 2018, 10:44:34 AM »
Small stationary engine such as those in Lawnmowers or the Chinese 3kVA generators tend to have two springs - one that is attached to the governor and against which the governor works, and another, much much lighter one, attached to the linkage as an anti-hunting device.  In my experience with small petrol gensets, if the small, light spring is lost damaged or worn - the engine will hunt ferociously, no matter what you do with the big spring & its attachments.

All of which maybe just tells us that CS spring is probably tring to do two jobs - and also, maybe, that we're trying to get a level of performance out if it which is challenging its 70-years-old design

Just my $0.02

38ac

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Re: Ashwamegh 25/2 :the saga continues
« Reply #13 on: August 07, 2018, 12:47:22 PM »
and also, maybe, that we're trying to get a level of performance out if it which is challenging its 70-years-old design

Just my $0.02

Not maybe but exactly the problem. Back in the day engine governing in England  was required to meet certain "classes"  I dont have the class of the CS committed to memory but  it was very lazy.  Most people DO expect a lot more out of the CS governor that it was designed for and it is to the credit of tinkerers that it works as as it does when tweaked.   In this case 32coupe does have an issue, they work better than he is experiencing even when not messed with.

One thing that vastly improves the engine governing is a larger element in the fuel pump. What this does is give more fuel for less movement of the rack. I think that Eddie has also played with that if I am not mistaken? My 8/1 gen set has a fuel pump from a 25/2 on it and the difference in governing is marked. The exact element diameters are not committed to my memory but I can get the information for anyone thinking about going that route. . The 6/1 8/1 pumps are marked 032 and the larger element pump for a 25/2 or 14/1 will be marked 034.  There are even larger elements available through MICO up to about 10MM I think? Depending on how large a person goes and how he  loads the engine it is wise to install a rack limiter such as Lister put on the engines originally.
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EdDee

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Re: Ashwamegh 25/2 :the saga continues
« Reply #14 on: August 08, 2018, 11:46:25 AM »
Indeed I have played with various pump element sizes - And found that the best all round for performance and speed governing tended towards the largest element I could get...

Smaller elements had a tendency to be lazy on the governor, as well as cause a greater amount of carbon build up in the cylinder when running crappy fuels... There was marginally more "ignition knock" with the larger element when timed correctly for the RPM desired....

Further, I experimented with everything I could lay my hands on spring wise for determining best governor responses...

I ended up with a basic formula of spring length un- tensioned, at rest, being 3x the length of the lower end of the bellcranks total travel as its shortest, to 6x the travel length at its longest.... The spring wire diameter does make a substantial difference, but that being said, the average best wire diameter I found was between .8 and 1.2mm and the nominal coil diameter was around 10 to 12 mm... Wide variances I know, but with not all springs having the same wire hardness (thus changing the forces they can exert over a given pull distance), there is a fair bit of leeway for playing around....

The easiest thing I found was to get 2 identical springs, set one up and start trimming until the response is satisfactory, or best with that particular grade of spring... If you overcook it and trim too much, slap the other one in and don't tighten it till it breaks....Lol.... Trimming off one or two coils at a time was a tedious, but rewarding job ultimately.... Also, I swopped the mounting/adjustment points round for better running too... (as well as getting a nice long adjustable area to work with)...

Some crappy pics below ..... (Not the ideal spring, but what I had on hand at the time.... It holds to around 51Hz unloaded through to about 50.5 when loaded to 3Kw or so...)

Cheers
Ed

PS, the silver tank is an auto oil top up I made and installed..... Keeps the oil up to max level, unattended while running long and extended periods.... It can be filled up during running too, by closing the tap, opening the top plug which has a dipstick attached to it, topping up the the tank, closing the top plug then re-opening the tap....Think its worth a patent application?

....Naah...

If you like it, use it!!

Edit... Oops, forgot to mention.... the crappy pic of the IP rack shows a weak spring I installed to take the slack out of the linkages and further improve governing tremendously... It also provides the peace of mind that should a link fail, the rack closes automatically... Additionally, there is a nut that allows the opening limit to be set to prevent "dirty black specs" on clean washing.... Nuff said!
« Last Edit: August 08, 2018, 11:51:28 AM by EdDee »
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