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Splash Lubrication and a Very Low Idle

splash lubrication low idle very low idle splash lubricated super low idle low idle contest oil slinger dipper

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#1 MaxTractor OFFLINE  

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Posted May 16, 2018 - 05:31 PM

I have loved small engines since childhood and a big reason has always been the cool putt putt sound. I have always loved low idles, whether on a small single cylinder or on a big v8 or on a big diesel or on an antique engine.

I think the lower the idle on a Garden Tractor, the more it feels like a tractor and the more classic feel it has. I'm not so into the unchanging 3200 rpm buzz or high idles of many mowers, especially later ones. I only tolerate it when necessary.

 

So I like to get all of my engines down to the lowest possible idle. I think it is a sign of a good running, well-tuned engine, and clean, properly-operating carburetor and ignition system when you can get your idle putt-putting really slow.

 

On that note I think this thread could simultaneously contain a discussion of HOW TO GET YOUR IDLE AS LOW AS POSSIBLE on various engines. I don't mean crazy win a contest slow, I mean nice practical slow.

 

Now my one reservation with running low RPMs is of course Splash Lubrication. I know there are many factors which vary greatly between different engines like where oil needs to be splashed up to, whether oil vaporization is a need for the particular oiling system, the design of the oil paddle/dipper/slinger, etc. The obvious thing is that low RPMs mean less splashing of the oil, less oil gets splashed up to higher areas inside the engine and less oil vapor is created. For example, the Overhead Tecumsehs, use oil vaporization to lubricate the valves way up top. Vaporization is another level above mere splashing IMO.

 

I think what would be helpful in understanding more about this potential danger to a valued engine, is some real concrete information or analysis of the issue. If anyone knows of some scientific or some quality garage-mechanic science on this or some educated/experienced thoughts, it would be great to learn from this and discuss it.

 


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#2 James Bosma OFFLINE  

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Posted May 16, 2018 - 09:21 PM

If you research the particular engine you will find that the manufacturer supplies specs for low to high rpm

EG: Kohler K series K321 for Massey MF 14, Idle 1200 rpm, max 3600 rpm

These specs should be followed to ensure proper operating order

If these specs are not followed there is no guaranty the engine will operate properly

If running engine below recommended rpm it becomes user beware, only one to blame is user / owner if damage occurs

Engines can run slower but oiling issues WILL occur

Engines and their splash oiling systems are designed to run at a certain rpm range

Engines with oil pumps have to run at a certain speed to maintain a certain pressure

In the end they are your engines and you are more than welcome to run them as you please

Just beware of issues from running engine below low rpm spec


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#3 Billy M OFFLINE  

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Posted May 17, 2018 - 08:49 AM

Another thing to thing about is cooling.  On an air-cooled engine, very little air is being moved by the jug/head at idle.  I have a  Kohler K361 OHV 18HP single.  It's not recommended to let those idle for extended periods due to insufficient air flow at idle...even at the factory recommended specs.  Some engines tolerate a slow idle better than others.  I guess you could monitor temps with a surface thermometer.  You could check the variation between idle and running to get an idea of what's going on.

 

As far as oiling goes...that's a tough one to guess on with a splash-lubed engine.  I've seen videos of small engines running an impressive amount of time with NO oil in them.  I would think a small engine would seize while running at a low idle, rather than send a rod through the block. 

 

Side note...I once brought a seized engine back to life with WD40.  The owner ran the engine completely dry of oil & seized it.  I filled then engine with enough WD40 to cover the rod journal.  Got it to break loose and slowly work it back & forth until I could get a revolution on it.  I kept turning it until it would turn with an acceptable amount of force.  Drained & filled the engine with fresh cheap oil.  Ran it about 5 minutes.  Drained & filled it with good oil.  It's still running fine to this day.  It was an old vertical shaft 12HP Briggs on a Simplicity.  I was impressed!  These old engines are quite tough.


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#4 framesteer ONLINE  

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Posted May 17, 2018 - 02:12 PM

At the local farm tractor show, they often have a "slow race".  Whoever can make it over the specified distance taking the longest time wins.  It's a combination of low gearing and lower than low idle.  John Deere two cylinder tractors always win.


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#5 olds45512 ONLINE  

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Posted May 17, 2018 - 02:21 PM

At the local farm tractor show, they often have a "slow race".  Whoever can make it over the specified distance taking the longest time wins.  It's a combination of low gearing and lower than low idle.  John Deere two cylinder tractors always win.

That's because nobody has ever showed up with an old Ford that had a Sherman and an Everett gear reduction, if you have both and put them in low range the tractor could idle for an hour and not make it more than a few feet.


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#6 MaxTractor OFFLINE  

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Posted May 17, 2018 - 02:33 PM

Reduced cooling from reduced airflow at low idle speeds is a good point. But at a lower idle speeds the engine is generating less heat from both combustion and friction.

 

So I have another little project to put a computer on a tractor. It is not finished but it does have a temperature sensor. My sensor only covers 0-100 Celcius but I can get a different one to cover a wider range.

 

One thing I think I will do is put the sensor somewhere under the shroud where cooling air has just finished flowing past the head and is about the exit the internal part of the shroud directing the air.

 

I will look not for absolute temperatures at first, but what I can check for is a difference in temperature between say a standard idle of 1200 and a very low one of like 600 or maybe less.

 

This is the little computer I use for many things. It is called an Arduino. Almost as easy as Legos and not much more expensive to build basically anything electronic. Writing the code is no more difficult than anything else you watch teach yourself online, mostly via YouTube.

 

I have got this thing measuring temps very accurately and in a stable manner.

 

I was going to do this anyhow but I did not have a very useful reason. Thank you guys for giving me the idea to test something meaningful!

 

The tiny temp sensor is just out of view in this pic. The CTL 510 number shown is the position of the knob (halfway position) which I will be using for fine-control of a linear actuator.

Celcius and Farenheight readings of the sensor are shown below.

 

Display $12. Sensor $8. Computer $30. Other bits $20. And I paid way way too much because I bought retail.

 

Second pic shows the sensor as I bought it, already mounted on a tiny circuit board with a needed resistor and capacitor. I recommend buying them like this. Actual size is about 1 inch by half inch.

IMG_2528.jpg TEMP-01_SPL.jpg


Edited by MaxTractor, May 17, 2018 - 02:39 PM.


#7 MaxTractor OFFLINE  

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Posted May 17, 2018 - 03:33 PM

This engineering forum discussion a splash-lubricated gearbox design brings up some other points on the oil and temperature.

https://www.eng-tips....cfm?qid=310814

Summarizing new/relevant points:

 

1. Specifics of HOW the oil is splashing inside the case is important to cooling. Enough oil must splash on moving parts to extract heat. Oil is the way heat is carried out of the engine. To release the heat, oil must splash on as much of the CASING as possible, transferring the heat to the casing and to the outside through as much of the casing as it can touch. This means if oil is not splashing as high, you have more of a sump volume of oil, collecting and not releasing its heat. Your engine case is your 'radiator'.

 

2. Moving parts, rotating gears and bearings, when fully submerged in oil, generate more heat because of friction with and within the oil itself. So when an engine is at a lower idle, less splashing means a greater sump volume and more things will be submerged to a greater degree, so more heat will be generated by gears and bearings which are submerged in the oil to a greater degree. (A lot of high school science classes demonstrate how stirring water increases it's temperature. Remember that one?)

* But this conclusion is countered by the fact that higher RPMS also mean more friction with and within the oil. How these two similar factors balance out could vary a lot with engine design.

 

I guess the heat issue is completely inter-twined with the lubrication issue.

I am definitely learning from this research and might end up limiting my very-low RPM running to something occasional.


Edited by MaxTractor, May 17, 2018 - 05:53 PM.


#8 MaxTractor OFFLINE  

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Posted May 17, 2018 - 05:13 PM

Briggs Opposed Twin with plexiglass case side, to show splash lubrication/RPM differences. Now I think he converted this twin from horizontal shaft to try to make it run vertically. Not sure, but in any case, this is one of the most illustrative videos on the topic I could find. It is very clear that much less oil splashes up at low RPMS. His is just using the starter, but when he feeds it 24 volts and doubles the RPM speed, oil goes from almost no useful splashing up to a good amount of splashing. Of course this is a highly custom engine mod project and he is specifically concerned with getting sufficient splash lubrication.

 

There are a lot of vertical shaft push mower (and/or lawn tractor) engines available so sometimes people convert them to horizontal shaft operation. Looks like most mods related to splash lubrication. It's interesting to see how new oil drain/flow channels for bearings were cut and old vertical-op channels were JB-weld-filled. This person made their own paddle/slinger/dipper.

 

Great demonstration of how a briggs vertical oil slinger works, shown in a disassembled engine:

 

Educational animation on the topic.


Edited by MaxTractor, May 17, 2018 - 05:41 PM.


#9 MaxTractor OFFLINE  

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Posted May 18, 2018 - 04:07 PM

Another thing to thing about is cooling.  On an air-cooled engine, very little air is being moved by the jug/head at idle.  I have a  Kohler K361 OHV 18HP single.  It's not recommended to let those idle for extended periods due to insufficient air flow at idle...even at the factory recommended specs.  Some engines tolerate a slow idle better than others.  I guess you could monitor temps with a surface thermometer.  You could check the variation between idle and running to get an idea of what's going on.

 

As far as oiling goes...that's a tough one to guess on with a splash-lubed engine.  I've seen videos of small engines running an impressive amount of time with NO oil in them.  I would think a small engine would seize while running at a low idle, rather than send a rod through the block. 

 

Side note...I once brought a seized engine back to life with WD40.  The owner ran the engine completely dry of oil & seized it.  I filled then engine with enough WD40 to cover the rod journal.  Got it to break loose and slowly work it back & forth until I could get a revolution on it.  I kept turning it until it would turn with an acceptable amount of force.  Drained & filled the engine with fresh cheap oil.  Ran it about 5 minutes.  Drained & filled it with good oil.  It's still running fine to this day.  It was an old vertical shaft 12HP Briggs on a Simplicity.  I was impressed!  These old engines are quite tough.

My 16 hp Kohler in the Wheel Horse is pretty tempting to make idle slow. But is has a nice thumpy tractor sound already so Idefinitely won't risk that engine. I think it is low hours. I will be getting into monitoring temps, either the easy way with a point and shoot thermometer or using my little experimental computers and sensors. (These can easily track temp data over time with or without a laptop to even graph it if you like. Simple to use.)

I will be getting an RPM sensor into the mix so I could track them together, averages over time etc. (Nerdy stuff done for fun, learning and experience.)

 

Yeah the splash-oiling RPM situation definitely needs to be considered differently for each engine and is complex. I think some good info can be gleaned from the links I posted above tho.

 

I have some good luck with patience and WD40 too. My C-160 hydraulic valve/control was frozen solid, heavy rust on the exposed plunger. I did a hundred or so cycles of: apply WD40, spraying to get it down plunger/shaft into stuck area, tap it LIGHTLY on the end with a hammer while alternating LIGHT pulling force on the control back and forth back and forth tapping. Took a long time before it even budged but I never forced it and eventually got it free and better. Works like new now. I am sure some small rust and dust particles were released and went through the system but by design I imagine they never made it past the filter and never entered the pump internals. Very satisfying to free up good equipment like this and bring it back to life.






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