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Author Topic: Twin...SLOW SLOW speed....?  (Read 137 times)

Powdermonkey

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Twin...SLOW SLOW speed....?
« on: November 30, 2021, 12:24:58 AM »
Folks- As a test, I removed my governor spring from my external linkage on the 30/2.  Under load, and "at speed", I'm running right about 800 rpm IIRC.

With the governor spring removed, that engine idled down to 20 turns in 7 seconds.  I could actually count the gib rotation on the mainshaft. 

So...about 200-250 rpm.  Quite slow. 

And that got me thinking:  On REALLY cold nights down here in FLA, could I run my 30/2 overnight at ~ 250 rpm, just to keep my cooling water from freezing?  By calculations, I'd use about 0.08 gallons/hour...or less (no load) at 200-250 rpm.   

The engine has an oil pump, which largely lubricates the mains.  Splash oiling for the rest of it.  So...my only real question is "lubrication".  Will ~ 250 rpm provide adequate lubrication to this 30/2?

Anybody got "real world" knowledge on this?

mike90045

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Re: Twin...SLOW SLOW speed....?
« Reply #1 on: November 30, 2021, 05:14:37 AM »
Somebody, in times past, made a crankcase cover door of plexiglass, to observe the activity while running.  instant oil mist was the reported result ( as I recall )  at normal RMM's the dipper slings oil everywhere, up to the piston grudgen pin, cam bearings... everywhere.    I doubt that can happen at slow RPM's and you could have an oil related failure.   
 And without sufficient heat, the piston & head will carbon up

veggie

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Re: Twin...SLOW SLOW speed....?
« Reply #2 on: November 30, 2021, 04:03:27 PM »

As mike suggested, the issue may be carbon buildup if you don't have enough cylinder head heat.
So.... find a way to build heat.
Do you use active cooling or heat-syphon?
A small12 volt circulating pump in the cooling circuit could overcome resistance caused by the addition of an inline thermostat. (Maybe 180f)
Many of us have modified the cooling water outlet flange at the cylinder heat to accept an automotive type thermostat.
Also, add a little load to the engine at that low speed. In fact, load it up as much as possible. Perhaps an alternator to charge the battery that powers the circulating pump plus some additional light bulbs until the engine is sufficiently loaded.
Then you may make enough heat to prevent carbon buildup.

veggie
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Powdermonkey

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Re: Twin...SLOW SLOW speed....?
« Reply #3 on: November 30, 2021, 09:40:43 PM »
Veggie- Many thanks.  The engine is thermosyphon cooled.  I "could" pinch down the ~ 2 feet of rubber hose transition I've got going up into the tank.  That would provide some level of restriction.  I guess I could also run a bypass with a thermostat in the bypass.  I could also see how the thermosyphon works at low speed.  If I can bring the head temperature up to ~ 150F...that might do the trick. 

Hugh Conway

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Re: Twin...SLOW SLOW speed....?
« Reply #4 on: December 01, 2021, 04:30:08 AM »
@Powder
I don't know how your cooling system is set up. Tank or rad. If a rad, just throw in some anti-freeze, acts as a corrosion inhibitor too.
 If tank cooled, it will take too much antifreeze to be economically feasible. Also, a drain valve on the lower cooling outlet would allow you to easily drain the coolant out during freezing weather if it is only water that you want to use.
I am in Canada, my 6/1 lives outside and is used daily in winter for charging batteries. I use an old cast iron house radiator for cooling and a 50/50 antifreeze mix. Works for me.
Cheers,
Hugh.
BTW, I once removed the inspection door while running at very low speed. I can tell you that oil does get flung about quite a bit, even at low RPM............took me hours to get cleaned up!
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Tanman

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Re: Twin...SLOW SLOW speed....?
« Reply #5 on: December 01, 2021, 06:45:14 AM »
I have a similar question to this, I have a 12/2. But really only need 4kw of power out of it at any given time. I'm assuming there would be less fuel consumption and wear If I built it to run continuously at (guessing) 450rpm ish? My other idea was to remove the second piston, rod, and pushrods and run it as a single at the regular 650rpm.
Kubota ea300
Metro 12/2

38ac

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Re: Twin...SLOW SLOW speed....?
« Reply #6 on: December 01, 2021, 10:58:39 AM »
Slowing a 12/2 down to 500 RPM makes it a 10/2. Using the 2HP to 1 KW rule of thumb you would have a 80% loading at 4KW, which is ideal IMO.
If you decide to remove one rod and piston be sure to have a camera set up and share video the first time you start it!! 😆
Collector and horder of about anything diesel

veggie

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Re: Twin...SLOW SLOW speed....?
« Reply #7 on: December 01, 2021, 06:56:33 PM »
BTW, I once removed the inspection door while running at very low speed. I can tell you that oil does get flung about quite a bit, even at low RPM............took me hours to get cleaned up!

Hugh,
That is useful information for us low speed runners.
Thanks very much for sacrificing one of your favourite T-shirts to get that info  ;D

cheers
- 6/1 GM90 Listeroid - Delco 33si Alternator
- Changfa R175 - Lease/Neville Alternator
- JiangDong R165 Air cooled - 2 kw

Tanman

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Re: Twin...SLOW SLOW speed....?
« Reply #8 on: December 01, 2021, 07:49:52 PM »
Slowing a 12/2 down to 500 RPM makes it a 10/2. Using the 2HP to 1 KW rule of thumb you would have a 80% loading at 4KW, which is ideal IMO.
If you decide to remove one rod and piston be sure to have a camera set up and share video the first time you start it!! 😆

Lol, well that answers that question.
Kubota ea300
Metro 12/2

38ac

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Re: Twin...SLOW SLOW speed....?
« Reply #9 on: December 02, 2021, 02:25:36 AM »
Back when the debate was on as how to orient the dipper on a Listeroid I posted that one doesnt need to guess or do any more than run the engine for a minute, shut it off and remove the crankcase door,, warning! have LOTS of rags handy! The amount of oil slung around in these engines at normal RPMs is tremendous.
Collector and horder of about anything diesel