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Author Topic: Engine power measurement and lubrication.  (Read 235 times)

KBIO

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Engine power measurement and lubrication.
« on: September 30, 2020, 01:14:03 PM »


First of all, what is the purpose of engine lubrication?
By definition, lubrication is intended to reduce friction and wear between two parts in contact and in motion relatively to each other. Considering the power of our engines, we understand that it is rather the friction reduction that we are interested in.We Steamer, then , have a problem to solve : we need to oil,  moving parts in a hot and dry environment! Every one knows that saturated steam is dry. Fortunately , if I dare to say so, the steam in our lines engines , if not overheated, will condensate a bit. We shall take advantage of it to make our oilers work.. This is this small amont of water which spread the oil all over the moving parts. The steam condensating when hitting the oil surface in the oiler.Now, we have to send oil in a water wet environment! Oil and water do not mix naturally. Not enough water and the oil stays in . Too much water and it makes nasty mayonnaise. What is mayonnaise then !It is an emulsion. In our engines, the steam is dry = basically no water- and mayonnaise cannot , a priori, forms. Unless the steam condenses a bit and , that little bit of water with oil will create an emulsion that will cling to the moving parts. The sliding valves are excellent beaters to make this mayonnaise! Let's take advantage of it !The mayonnaise hangs well on the walls The goal is is to obtain a good ratio. and as the best being the enemy of the good, we must allow the smallest possible volume of oil in. I always take the exemple of of a drop of oil on a wet floor to make the people understand that the combination of oil & H2O is what reduces the friction between the sole shoe and the ground. Some remember it by (painfull) experience.
But let’s keep it simple  .
Let's find a solution!
To lubricate our engines we need to find an oil which have the following properties:-It must have a viscosity that allows it not to disperse: viscosity is rather a state; when it increases, it opposes a resistance to flow. The state of a viscous fluid will flow without turbulence.-It must be fluid enough to allow it to flow out without doing it all at once. The more sleek a fluid is, the less it will resist to flow-It must be smooth, i.e. “weting” the surface to be lubricated. So spreading out well on the surface without discontinuation.-Must attach to the moving parts. Can not evacuate under mechanical (centrifugal) or thermal (steam) action-It must keep all these properties at the required working temperature.And now you have set a foot in: Tribology!
Tribology being the study of friction and the means to reduce friction.
T
oo complicated for me, I leave it to competent engineers!


There are several kinds of oils: animal, vegetable, mineral... we will talk about the one that best suits our problem.
Some use olive oil! Castor oil is however better lubricating.The viscosity of vegetable oils varies little with temperature, and these oils are particularly suitable for fixed-aperture lubricators, the flow remaining substantially constant. They are the most stable up to a certain temperature.....and stink ! I' have heard so much miraculous recipes on this matter!But at high temperatures, vegetable oils decays, acidifies and carbonises itself . We are talking here about temperature at 350°C (Tassignon.be)


The problem with olive oil is that if it fairly resists to temperature , but is not tha best oil for lubricating , and , it will eventually rub out the metal on a long run.
At the end, the most elaborated product adapted to our engines is mineral oil.
It meets all the conditions required to improve the performance of our engines under steam conditions.
The viscosity of an oil is its ability to not shear the oily film that separates moving parts under unconventional conditions.
An engine oil is proposed with different grades according to the needs and there is necessarily one adapted to our needs.
There are several units of measure of viscosity depending on whether it is dynamic or kinematic: But we don’t care!
It varies with temperature, the oil must remain viscous enough to keep between the two parts in contact, while remaining fluid enough to move freely through the engine.
To measure the grade, the oil is brought to a certain temperature, then the time it takes to pass through a standardised orifice is measured . I pass over oil characteristics, grade , … Bla-bla-bla ...

On our assemblies, we need two kinds of lubricants.
-The one used to lubricate the parts outside the motor; bearings, slides,..... In short, all that must rub without gripping, pinchhing, and facilitate the sliding of parts in contact at moderate temperature A sewing machine oil is too fluid and quickly loses its properties with heat; it is quickly evacuated. A lost-consumption olive oil might be suitable if it wets all the parts in contact, but a SAE30 engine oil will hang better on the metal, because it is made for that!.

-The other place we have to pay special attention to is the inside lubrication of the moving parts within the steam environment; sliding valves , segment rings, pistons/cylinders.
At this point we must take into account two things:
Bring just enough oil to the parts in contact and create just enough emulsion to hang on. In order to avoid excessive consumption, an 80/140 SAE will be suitable .
Avoid having an oil that degrades and loses its lubricating properties due to temperature. A Grade 120 @ 140°C will be viscous enough and will guarantee this oily film between the rubbing parts,
Since the temperature is 133°C @ 3 bar (gauge) in the engines, the oil must not degrade with the temperature.
For convenience, it can also be applied to moving parts outside the engine, as these parts will be  hot : +/- 50°c measured on the crankshaft.. We must not forget, either, that unlike a conventional engine, the oil only passes through . A bit like on the chain of the chainsaw. There’s no point in overpricing oil.



What quantity to use in our steam plants ?
From my experience and tests that I have done, I would say that 1cc of oil for a 5cc engine running for 45min at 3 .5 b abs makes the job.
You may obtain diferents figures depending of a lot of factors , but as long as there is a drop of oil passing by in the condensates , that will be fine.


The position of the oiler:
Two choices:
Just before the control valve if the boiler is equipped with an isolation valve. This makes it possible to lubricate this valve at the same time.
After the control valve and just before the engine if the boiler is not equipped with an isolation valve. This is to minimise the return of oil to the boiler when it cools down: depressurization = suction.



I have a good friend of mine claiming that he does not see any advantage of an oiler for his steam engine. That works the same , he said !
I made a test with him , with a Prony 'sbrake to show him the difference in torque and RPM with and without oil.
He saw it and shyly admitted that the engines runs better with oil, but ….. he decided not to use it !
What I can do my « fliend » ???


Below a brake of Prony that I used to compare the power of engines.
One end of a wood is cut along and leaves a round shape to hold the crankshaft. The spring tension can be adjusted with the control knob by pinching more or less the end of the crankshaft.
The tin string wounded around the end is to counter balance the weight of the adjusment knob assy.
There is a needle at the other end to push on the scale .
The torque in Newton by meter is obtained by multiplying the lentgh « L » (between the needle and the center of the crankshaft) by the force « F » (read on the scale).
1000g = 9.81 N ==> roughly 10 g = 0.1 N.
It can be converted in Watts then , for those who likes it better !
From then, you find out your engine power, you can make comparaisons between some, and at least, you'll have a number to prove what you say.


Note :
-Remember that the power consumption of the brake is converted in heat. So with a more powerfull engine you may burn the friction contact and have erroneous readings. …. if not fire !:-0.

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steamboatmodel

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Re: Engine power measurement and lubrication.
« Reply #1 on: September 30, 2020, 04:24:20 PM »

I have found that this article is very good on steam oil;
https://www.southernsteamtrains.com/misc/steam-oil-hwade.htm
Gerald.
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KNO3

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Re: Engine power measurement and lubrication.
« Reply #2 on: October 04, 2020, 10:15:53 AM »

Hello KBIO,
I am very interested in the results you got measuring power of your steam engines. Could you please post them here for comparison?
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KBIO

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Re: Engine power measurement and lubrication.
« Reply #3 on: October 04, 2020, 04:46:10 PM »


Hello.
The measurments are very , very random as there is a bunch of parameters that give up to 40% difference in the same conditions = stable pressure and RPM.
Depending also of the stroke of the engine for the same cc’s, it gives different readings.
The boiler pressure is 2.5b and the engine runs @ 1200 RPM steady for each reading.
Also I needed to change the boiler according to the size of the engine.
So I must admit that I do not rely too much on those measurements. What I measure at 10H00 in the morning is different in the after noon. I don’t know why!!
I did a lot of tests with diffenerents engines: JMC, Anton, Regner, Cheddar , Stuart,  … and I cannot come out with sensible numbers.
I wouldn’t rely on my experiments for precision , but to give a general idea and a rough picture of the  power only.
Sorry !
That’s all fun in any case.
Regards.


   Read power in Watts:   

   
2cc      +/-      5/6
3cc      +/-        8/10
4cc      +/-       10
5cc      +/-       10/15


10cc      +/-       25/30
15cc      +/-       35/40
20cc      +/-       50/55
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KNO3

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Re: Engine power measurement and lubrication.
« Reply #4 on: October 04, 2020, 08:42:55 PM »

Yes, there are many variables. And I do not quite understand how you adjust friction of the device to get accurate readings.

Anyway, wouldn't it be an option to use a directly driven (1:1) dynamo for measuring steam engine output? One could measure the output voltage and draw some conclusions?
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Jerry C

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Re: Engine power measurement and lubrication.
« Reply #5 on: October 04, 2020, 10:45:39 PM »

My father did a great deal of work on dynamometers which he always called a brake. He carried with him his personal Kew Pattern barometer and certified thermometers to calibrate the brake. I still have the barometer in storage and looking for a place to put it on the boat we live on. It’s a collectors item made by Nefertiti & Zambia. The traditional brake referred to earlier in this post is a fine mechanical method for comparative measurements though, only lacking a few constants. The dynamo method also has limitations but simpler in practice.
Jerry C.

KBIO

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Re: Engine power measurement and lubrication.
« Reply #6 on: October 05, 2020, 09:42:55 AM »

Hello!
Quote
I do not quite understand how you adjust friction of the device to get accurate readings.
The way I do , is to run the engine full blast with 2.5b pressure in the boiler.
I turn the knob on the lever ,  squeezing the pads against the crankshaft's end until I reach 1200 RPM. This is close to what we have in a moving boat with a 50mm propeller.
When everything is +/- stable I read the weight on the scale.
So I have the engine power @ 1200 RPM.
This is what it is and worth what it worth %% but I have an idea of my engine capacity then. Remmember that I used this device to show to a friend the difference between an oiled engine and a non-oiled one.
The accademic method is to measure the power with the engine at full revs. (which is not realistic for the purpose of my engines I guess) .

There is more accurate and sophisticated ways to get an engine power but I leave this to more competent engineers.

Best regards.
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KNO3

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Re: Engine power measurement and lubrication.
« Reply #7 on: October 06, 2020, 10:00:13 PM »

Thanks for the explanation!
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