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basic steam system design info?

Posted by ReubenT 
basic steam system design info?
January 29, 2012 09:44PM
Where do I find design info? like boiler HP calculations based on cu ft heat surface and pressure, matching boiler size to engine size, etc. Perhaps something on steam flow rate to determine best port size for a given pressure, displacement, and rpm. I used to have a little pamphlet with some of that info. but can't find it right now. I know there can be a lot of variables, but a known starting point would be good. I have a number of old book reprints on steam engine design but they have nothing on sizing info. I don't want to put something together and then have a boiler too small for the engine size.
Re: basic steam system design info?
January 29, 2012 10:57PM
Hey Reuben,

Some of it is cut and dry, some is a bit more difficult to figure and depends greatly on the type of aparatus used.

Port size, generally you want to keep the steam velocity bellow 12,000 feet per minute(roughly 120 mph), slower is better.

To get the required port area, multiply the piston speed in feet per minute by the piston area in square inches, then divide that by the wanted steam velocity in feet per minute.

You said the engine you have laying around is 97.6 ci and four cylinder. So 24.4 ci per cylinder. I don't know the bore and stroke so I will assume 3" stroke that would give a piston area of 8.133 square inches. Piston makes two strokes per revolution so 6" per rev or 1/2 foot. So the piston feet per minute would be 1/2 the rpm. Say 2,000 rpm, that would be 1,000 feet per minute piston speed, times 8.133 sq in gives 8,133, divide that by 12,000 and you get .677 square inches port area.

Really, 8,000 feet per minute steam velocity would be much better, so that would be just about one square inch of port area.

For steam and power per square foot of boiler check out the link bellow, then scroll to the bottom of the link for a table of four different boilers giving statistics about them.

[www.steamgazette.com]

Power from the engine is another thing all together! It depends on a load of factors. Lets assume that you run your engine with an Meen Effective Pressure( MEP ) of 150 psi, horsepower is equal to 33,000 lbs lifted one foot in one minute or 33,000 ft lb min. All of your four single acting pistons would give total one foot of power stroke per revolution with the figured 3" stroke. So then 150 psi times 8.133 sq in gives 1,220 lbs of force, giving in theory 1,220 lbs ft of force per revolution. Lets assume that the MEP I gave already has all of the engines losses included in it.

If you wanted say 20 horsepower from the engine then that would be 660,000 lb ft min, so 660,000 divided by the 1,220 produced per rev would give 541 rpm, then 40 horsepower would be at 1,082 rpm and 60 horsepower at 1,623 rpm. Assuming the same losses for a given rpm, generally however the losses in a steam engine increase with rpm.

A bigger question is, is the engine you are using designed to handle torque like that at such low rpms? Will the oiling system keep the bearings from freezing up? The figures above indicate about 200 ft lbs of torque. Any idea what the engine originally produced?

Caleb Ramsby
Re: basic steam system design info?
January 30, 2012 05:12PM
Probably the most difficult thing to figure is the efficiency of the engine.

The term generally used there is pounds of steam per horsepower hour produced per hour. A pound of steam being a pound of water boiled into steam.

This is a rather contentious issue, to say the least.

The best a Stanley, with its simple expansion engine could get is 16 lbs per hp hr. Both the Doble and White used compound engines and could get 12 lbs per hr hp. Some of the most extreme uniflow simple expansion engines could get 8-9 lbs per hp hr.

All of these figures come from running the engine on the dyno, measuring the horsepower the engine produces then measuring the lbs of steam the engine uses, via condensing the exhausted steam from the engine and weighing it. Then dividing its weight by the horsepower produced.

On the surface the White should have gotten 133% more miles from a gallon of fuel then the Stanley. However this is not the case, they got roughly the same milage per gallon of fuel! The White boiler is slightly less efficient then the Stanleys, so that helps a little bit, but that isn't the whole difference.

One must consider how much metal is being heated up when warming up the car. The compound engines must either be larger in displacement, run faster or operate at higher pressures to give an equal amount of torque from a given steam pressure then a simple. This generally equals a heavier engine, thusly more metal to warm up. When starting from a stop and warming up the White is required to be run in simple mode. This sends steam from the boiler directly to the low pressure cylinder and exhausts from the high pressure cylinder to the condensor.

The significance of that is the fact that the clearance volumes of a compound in general and the White in particular are twice as large as the clearance volume of the Stanley. They are also run in very long cutoff when in simple mode, so the steam rate per hp hr during real world driving is dramatically lower then it is when producing a lot of power on the dyno.

The thing to keep in mind when studying the "efficiency" of engines is that the operating conditions of the engine on the dyno, such as being fully warmed up, running at very high outputs and with the optimal cutoff, are rarely if ever experienced on the road.

The SES steam car project was just about the most advanced steam project from back in the 70's fuel crisis. It used a single acting uniflow with poppet valved design engine and design parameters of over 1,000 psi and 1,000 deg F steam. That great steam temperature giving then a number of issues.

To be very frank, a great deal of people still insist that this is the only way to go. It must be uniflow, must have poppet valves, must use as high of a temperature as possible and must have the greatest expansion ratio as possible.

Well, here are the results as given by a member of the SES team:

[www.steamcar.net]

I would like to note two VERY significant things.

1: He states that with a steam temperature much above 750 deg F there was little to no difference in engine efficiency! He states that had they known this before they started they would have saved a LOT of time and money in development, as in buiding things to withstand such great temperatures.

2: The minimum cutoff of the engine gave an expansion rate of 1 : 15.4. This figure, as he states, it including the clearance volume. This is an increadible expansion ratio for a simple engine, that is all of the expansion occuring in one cylinder. He also states and shows with the graph, that the best economy was produced with an expansion ratio of between 1 : 4.5 to 1 : 7.5 . With little difference between these figures. You can see clearly from the graph that expansion ratios beyond 1 : 7.5 gave lesser economy from the engine!

Please note that he also states that the dyno efficiency results were not as good as the formulas showed they should be and the road efficiency results were less then what was shown on the dyno.

It took me way too many years to come to the conclusion that there is such a huge difference between what an engine SHOULD do according to Formula and what it WILL do in Reality, thusly the formation of the F/R ratio.

The benefit of low expansion, relatively low pressure and low temperature engines is that even running slowly, they are small and light, run very smoothly at low speeds, don't require rare metals to survive and potentially last a lot longer.

As opposed to high expansion, high pressure and high temperature engines, which basically must run fast, are large and heavy for their torque, run very rough at low speeds, must be built from more expensive materials and potentially won't survive as long.

This is much more showing in simple engines, with compound engines the low pressure cylinder is running with rather low pressure and temperature steam, it is the high pressure cylinder that takes all of the massive abuse.

That is what I have gathered in the last ten years of studying light steam power.

Caleb Ramsby
Re: basic steam system design info?
January 30, 2012 09:36PM
Thanks a lot, lot's of good info to run with. By the way; doesn't boiler HP go up when PSI increases? There aren't any PSI figures on the chart of those 4 boiler types. I'll have to balance PSI with ease of engine construction, try not to go any higher than needed to get the job done with a reasonable size boiler/engine combination. I'm thinking about the possibility of a yarrow boiler on a 5 ton truck, maybe 200 HP if possible. Something that will work on solid fuel easily, and I have a good share of the stuff to build one. A whole truckload of heavy wall steel pipe, mostly 1.5" dia, some 2.25" and some 2.75". and a 7 ft length of 6" pipe with 1/2" wall thickness that might make 1 good mud drum. Would have to find a couple more pipes for the other side and top drums. The truck I have to work with is an old 5 ton semi tractor 6x6. Cab is beat up pretty good but running gear looks real good with no oil leaks. The engine in it is the LS 465 multifuel diesel, 165 HP, and very under powered for it's size but the tractor low gears make up for the lack of power to some extent, It'll climb a mountain with a load at maybe 10 mph.

Looks like the subaru engine and the ofeldt will be close enough matched to be ok together. I think it can handle the torque, since it was a tough little engine designed for a car by a truck manufacturer. (the clutch may not) Even though normal car gas engines usually have torque figures somewhere in the same vicinity as HP. which would give my 4 cy engine about 70 ft lb as a gas engine. Whereas diesel engines commonly have torque numbers around 3 times the HP. I have in mind using a synthetic oil like amsoil and adding a metal base lubricant additive to get the best lubrication possible. MBL is the kind of stuff that will coat bearing surfaces and stay there, reducing friction to way below what oil by itself can do. We were testing it many years ago and it was amazing what it will do, we could wipe all oil off and dry the metal surface and it was still there doing a better job than a normal oil bath. Had to use sand paper on the steel wheel to get it off. It is supposed to make an IC engine run without oil indefinitely. (I did it for a while once)
Re: basic steam system design info?
January 30, 2012 11:17PM
Hey Reuben,

Boiler horsepower is really considered to be a misnomer now. Especially if it was considered alone without considering the engine involved.

No, pressure has no relevence when considering the boiler horsepower.

Boilers are rated in the pounds of water they can boil into steam in an hour.

Lets say you have a boiler that can boil 1,000 lbs of water in an hour.

Now say you have an engine that uses 50 lbs of steam per hour to produce one horsepower, that would be 20 horsepower produced for hour. Note that engines using no superheat, which have very leaky valves and large clearances can easily consume this much steam to make one horsepower for one hour.

Now say you have an engine that uses 12 lbs of steam per hour to produce one horsepower, that would be 83 1/3 horsepower produced for one hour.

So, is the boiler in question a 20 horsepower boiler or a 83 1/3 horsepower boiler?

Ofeldt also made engines and in the booklet I have, which I got from the steam automobile club of America storeroom, they state:

"Our boilers, as listed, are rated when used in connection with a single or double, double acting high pressure engine, operating under 250 lbs steam pressure, turning 400 revolutions per minute and without vacuum. When used in connection with compound engines they will give half as much again as the listed ratings, and when used in connection with a triple expansion engine they will give double the high pressure rating."

Thusly if they rated a boiler at 20 hp, that was for use with a simple expansion engine, what they call a "high pressure engine". That is it only works on live or high pressure steam. 30 hp when used with a compound and 40 hp when used with a triple expansion engine. Note again that these differences would be much more pronounced with stationary or marine service with their more steady outputs, not so pronounced when used in a road vehicle.

Stanley rated their boilers by straping the system on a dyno and seeing what horsepower they could get out of their engines while maintaining a steady boiler pressure. Note that in the link I gave you before the Stanley 20 horsepower boiler made 326 lbs of steam per hour. That would be 16.3 lbs of steam per horsepower hour.

Of very great significance is that boilers which have a large volume of water up at temperature, such as the Stanley firetube, Ofeldt water tube and Yarrow watertube, can be "over drawn". That is the very hot water in them acts like a heat battery and its energy can be used to get more steam out of the boiler then the burner or fire can produce.

The Stanley for instance can provide the engine with FIVE times as much steam as the burner can produce! Not forever, that's for sure, every second one is drawing more steam from the boiler then it can make, the pressure in it will reduce and at an exponential rate. So for a few minutes the Stanley 20 horsepower boiler can given the engine enough steam to make 100 horsepower!

Here is where there is a bit of a dilemma.

With a monotube type boiler or one that carries virtually no very hot water inside it, there is no real capacity to "draw down" the boiler. Whites, which had monotubes when Stanleys had the heavier firetubes, the Whites couldn't even have a whistle because blowing it would flatten the boiler pressure! With Stanleys you can whistle away a lot and the boiler won't "feel it" .

So, with a boiler with little water in it, the max boiler output is determined by how much steam the fire can make.

With a boiler holding a lot of water it is determined by the amount of water it holds and at what pressure the water is. So, I suppose in that way the pressure determines the boiler horsepower. Higher pressure steam requires the water to get hotter to boil and requires less heat to vaporize a pound of water to steam, although it takes more heat to get it hot of course. I wrote a rather long and probably boring article about this subject for the SACA bulletin a while back.

So, what it comes down to is that with a boiler with a lot of water, it only need to be powerfull enough to give the engine enough steam to produce the "nominal" horsepower required. Lets say that a truck, going 60 mph down the flat road takes 50 horsepower(I am a bit too tired and hungry to do the math on that right now), then if that is your desired use of it a 50 horsepower boiler would be good enough and the "boiler reserve" that is the "draw down" power would give you the extra umph required to get over a big hill. . . as long as the hill isn't too long. If it is too long then the boiler would run out of steam before it reached the top. In hilly terrain a steamer like the Stanley loses pressure going up a hill, then builds it back up going down the other side of the hill, so that when it reaches the bottom of the next hill it is at full pressure again and ready to tackle another one.

A monotube or small reserve boiler must be capable of producing enough steam with the fire to give the max horsepower required, so it must have a much more powerfull burner.

With a wood fire, especially hand stoked, running with a boiler which has a large volume of water in it will help keep it MUCH more stable under a great variety of road conditions.

"The more you know, the more confused you become! "

Caleb Ramsby
Re: basic steam system design info?
February 01, 2012 12:03AM
Thanks a lot Caleb, most of it makes sense. (Unlike my brother and cousin who're doing something that doesn't make sense. oh well, I'll stick with shop work and let them finish the house)

It just seems to me that higher PSI would do more work at a given evaporation rate.
So a mono tube boiler would be OK in a boat where the load is more or less constant, or even a tractor doing steady work. and the boilers with some water capacity would do better in a vehicle and in wood fired situation where the fire may not be real consistent. Looks like a steam truck may be quite feasible and practical after all. I'll have to experiment with a smaller system and then scale it up.
With a hybrid electric car we size the batteries to provide enough power to climb the maximum hill we want to drive up in one shot, and the generator just needs to provide average power. (home made small car hybrids commonly get 80-100+ mpg, I've heard of 120 but I think they were averaging 45 mph and running a small diesel generator) Steam works the same way, heat production and it's transfer surface being the generator and water capacity being the battery. (A couple years ago I repaired an electric car and converted it to hybrid with a removable generator, and then sold it for twice the money I had invested, but a dead EV for cheap is not a frequent find)

Confused? I think my ideas are getting a bit more organized. I enjoy a mechanical challenge with practical working results. But am royally disgusted with modern liquid fuel powered IC junk. Every time I have to work on a car any newer than about 27 years old, I get so fed up with the obvious intentional robber technology I vow to never work on em again. They intentionally make them hard/expensive to fix in order to push people into buying new more frequently. And the old better ones are getting too old to keep going in many cases. Gonna have to start making my own vehicle drive systems. Wither electric, steam, or probably both. Thanks for all the info. RT
Re: basic steam system design info?
February 01, 2012 12:49AM
Hey Reuben,

Glad to be of some help.

The boiler pressure to engine horsepower deal is a bit confusing at first. The issue is that with an increase in pressure there is a reduction in volume of the steam. So a given pound of steam at higher pressure is much smaller.

One pound of 300 psi steam takes up 2,667 ci, one pound at 600 psi take up 1,330 ci and one pound at 1,200 psi takes up 625.3 ci.

So you can see that, roughly, doubling the pressure halfs the volume.

So if one assumes that there is a cylinder with a given bore diameter, which takes live steam from the boiler for all of its stroke, then if it were ran on 1,200 psi steam, the engine would produce 4 times the work as if it were running on 300 psi steam, however at 1,200 psi it would also consume just a bit more then 4 times the weight of steam.

As far as expansion goes, as shown above expansion ratios of above 1 to 7.5 really are not very usefull, expanding the steam down to, lets say 10 psi over atmosphere pressure or 25 psi absolute, which it 10 psi gauge that would take 187 or so psi, actually a bit more then that because as the energy is sucked out of steam as its pressure drops, it drops more rapidly then the formula " constant = pressure * volume " there is what is called the polynominal expansion coefficient and is usually between 1.1 to 1.3 depending on the steam conditions, this is an exponential applied to the volume in the C = P * V equation to figure out the actual pressure drop during expansion.

So, for practical purposes any steam pressure much over 300 psi will provide plenty of power and easily enough pressure to expand the steam enough to make its use economical.

The use of steam pressures well over 1,000 psi is mainly in an attempt to reduce the volume of the engine, although as I mentioned before it easily causes at least as many problems as it is purported to solve.

Getting a bit more into personal opinion here, I feel that what has happened in the internal combustion engined world has been going on in the light steam world since the 50's or 60's. I believe that part of the allure for the early steam cars and trucks, was their relative(relative to what some might say) simplicity. Yes, there was a lot of plumbing and numerous mechanical bits, but is was all mechanical and if you knew the system relatively easy to sort out. The biggest issue was waiting for it all to cool down so it could be worked on. The saying back then was it took the same time to fix a steamer as a gas car, with the steamer it took 10 minutes to figure out what was wrong and 2 hours to fix it, 1 hour and 50 minutes of that time just waiting for it to cool down, with the gas car it took 2 hours to figure out what was wrong and 10 minutes to fix it. Now with a gas car it takes longer to figure out what is wrong and much longer then that to fix it! Working on a SUV recently, replacing the fan bearing(idle type, with sparky clutch) , one is supposed to "tilt the radiator forward a few inches" hummm, the fittings on the radiator had been changed sometime and the bits that were supposed to let her slide, didn't let her slide, even with all bolts removed and significant force involved, the rubber isolation castings had been changed in design, so it wouldn't tilt forward, thusly the fan shroud had to be. . . well cut up a bit for the work to continue, my brother(owner of the SUV) wasn't bothered much, since is was not a significant alteration of the operation, his wife on the other hand. . .

Caleb Ramsby



Edited 1 time(s). Last edit at 02/01/2012 12:52AM by Caleb Ramsby.
Re: basic steam system design info?
February 06, 2012 12:06AM
Ok it's getting clearer. Kind of like PSI gets the work done but evaporation rate tells the psi how much work it can do. After all the energy comes from the heat transfer. you could make 1000 psi with a candle on a little tube of water, but how much work will it do? But now it looks like we might get more energy from the system if the pressure/temperature were lower, Since as was mentioned with the lamont, a cooler water temp soaks up heat faster. larger difference between fire temp and boiler surface temp. But the difference may be insignificant.

But if basically the same amount of work can be done by a lower pressure with a larger bore engine with a given sq footage of heat transfer. I might as well run it at a lower pressure and make a bigger engine.
I did some calculation using the figures given on the chart, and it looks like I could run it at 200 psi and make a single cy traditional engine out of one of the old D4 cylinder sleeves. Then I could use a simple slide valve and not have the excessive pressure on the sliding surface to deal with. It would be 4.5" dia with 9" stroke. The 40 hp boiler would keep up with a 25% cutoff at 500 rpm. (if I got the figures right) I'd try to make it adjustable from 0-50% or so.
Re: basic steam system design info?
February 06, 2012 05:29AM
Hi Reuben

Scientific terms Force, Work and Power and be a bit hard to grasp. They are
simple if you can under stand the math.

Work equals Force times Distance, Work = Force * Distance.

It takes some force to move an object. The force applied to move an object
produces a quaintly of work in moving it.

Pressure produces that force in an engine by acting on the an area. 200 PSI
acting on a 10 square inch area produces 2000 pounds of force.

If you maintain that pressure through the full stroke say 10 inches you produce
work = 200 PSI * 10 SQ-IN * 10/12 feet = 1666 2/3 foot pounds work. Piston area *
stroke = volume displacement. Work = pressure * volume.

Power is work divided by time, Power = Work / Time

1 horsepower= 33000 ft-lb/min

One of the properties of steam is it's specific volume. cubic feet per pound for
example. Steam properties vary with changes to it's state. There are some simple
formula for an "ideal gas" that illustrate state changes in an ideal gas. Steam
does not exactly follow those simple formula. But for small changes the ideal
gas formula are close. The changes are similar just not exactly so using ideal
gas formula for steam will be a bit off. The can be used ti illustrate the
ideas. The general ideal gas law is the Pressure time specific volume is equal
to temperature * a constant.

P * V = C * T

What Caleb was getting at is that if you have 200 PSI steam at 500 F or 600 PSI
steam at 500 F then

200 * V = C *500 = 600 * V

Sense P * V = work

and 200 * V = 600 * V thy both do the same work. With steam that isn't exactly
true. But there won't by that much difference.

But that is not all the story. Generally you are not supplying full steam
pressure but for part of the engine stroke. At some point in the stroke the
admission valve is closed and work is then being done by expanding steam.
Expansion is far more complicated. The pressure is drooping as the volume
increases. But it temperature is also changing so you can not simply apply the P
* V = C * T formula from above.

This is were pressure is able to effect work. For with higher pressure a greater
expansion pressure drop is passable. It is during expansion the heat is being
converted into work in the engine. And that is were you get your efficiency. The
greater the expansion the greater the potential for greater efficiency. But
there are things countering the increased efficiency with greater expansion. For
one with greater expansion the greater the temperature change of the steam in
the cylinder. This temperature change leads to heat transfer from the cylinder
walls to the steam heating the steam and also reducing the cylinder wall
temperature. On the next admission the cylinder has been cooled by the expansion
so incoming steam will have some of it's heat transferred to the cylinder. Then
when expanding the steam temperature drops below the cylinder temperature, heat
will be transferred to the steam. The back and forth heat transfer reduces
engine efficiency. At higher RPM there is less time for this heat exchanging and
the cylinder temperature swings is less improving efficiency. This subject gets
very complicated. There are lots of older threads here that argue this subject.

The real work producer is heat. To make steam you are adding heat to water to
make it boil and change into steam. The heat added to the water or steam changes
it's heat content. Heat content is a property called enthalpy It takes some
quaintly of heat to get water to the boiling point temperature. Then some
quaintly of heat to change it into steam at that temperature and then further
heating increases it's temperature as the steam becomes super heated. The
boiling point temperature changes with pressure. At higher pressure it takes
more heat to get water to the higher boiling temperature and less heat to change
it into steam. The steams heat content (enthalpy) at the boiling temperature is
different at different pressure. There is a relation between the boiling
temperature and pressure. We have formula that given pressure or temperature the
other can be found. The point at which water boils for a given pressure or
temperate is called the saturation line. The change of liquid (water) into steam
is called a phase change. Ice into water is a phase change. Solid, liquid, gas
are phases of mater. there are other phases of mater. But liquid and gas are
what we need know about for steam engines. Along the saturation line both the
liquid state (water) and the gas state (steam) can and do exist as a mixture. At
a temperature of around 705.4 F you reach a point where the heat of vaporization
is 0. It takes not heat to effect a phase change. That is called the critical
point. above that point the two states of the substance can no longer exist as a
mixture.

Probably have now overloaded you. But the point is that the amount of work
produced by a steam engine is a complicated calculations. And then only
probabilistic.
Re: basic steam system design info?
February 06, 2012 09:36AM
Hi Reuben,

One of the issues I'm studying is efficiency, boiling down to friction and forces induced by compounding or not. If trying to get 25 expansions or so, a non compound has 4 times the loading on the bearings/crank/crossheads/pins etc. as does a compound due to pressure. A compound has more friction losses and components. If double acting, cyclic forces cause more fatigue until you hit a certain rpm range (inertial forces are a ^3 function of rpm). Quite a balancing act of cost and design.

Keith
Re: basic steam system design info?
February 06, 2012 09:49PM
Yes I understand all that's said so far. Just have to figure out what would work best for a given situation and go for it even if some things are not quite ideal. I think I have a handle on matching boiler and engine size now to be sure I'm in the vicinity of the right match. And I think a low speed high torque engine would be fine for a low speed high torque vehicle. Yah, beefy components needed for the torque. I'm a bit unsure if the pillow block bearings can handle the load, but I can change them to something else easy enough if they go bad. The truck running gear is regularly loaded with 30,000 lb and powered with 175 hp diesel. at 440 ft lb torque. In low gear the transfer case must be taking a huge amount of torque. With my current design at 200 psi I'll have about 1200 ft lb maximum shaft torque at mid stroke with the cutoff at 50%. But that's probably far stronger than it'll ever need to be run. Some jobs it would just be "simmering" the boiler and running the engine with maybe 5% cutoff. some jobs would take the full 40 hp capacity. Like running a 5 or 6 ft rototiller or pulling a plow in sod.

For some situations absolute maximum efficiency would be worth striving for, such as power plants and long distance haulers. but when the situation involves chucking wood in a furnace to get some farm work done without loosin an arm ana leg at the fuel station, a bunch of extra time and work to achieve that last 5-10% gain is likely not worth the effort. Specially when the only fuel expense is time spent sawin wood up and throwing it on a trailer. (electric chain saw running from a generator on the tractor) Like the double or triple expansion engine is more efficient, but it's more engine work than necessary to get it running, so the simple single on saturated steam will be the way to go. RT


BTW, one side reason I want a steam tractor is so I can pull a steam hood with nozzels under it, (amonia injection nozzels would probably work) and sterilize growing beds for sensitive vegetable crops. It takes plenty of heat and a very slow speed to get the soil hot enough to kill weed seed. I recall hearing about it being done with an old traction engine, but it wasn't done on the go probably because the gearing on the machine wasn't low enough to go slow enough to adequately heat the soil. Besides, it'll likely just be fun to run. At least until it's mid summer and the heat gets unbearable, but I think we can deal with that with some high temp insulation and a canopy, and a fan, and some cold water handy. Winter is firewood gettin time and that's when it gets really fun! forget all that liquid fuel that keeps eating up my limited earnings, just chuck a stick in the fire and keep going. And that's where 4x4 with tire chains is about the only way to get around, right now it's sloppy muddy, my 2wd tractor won't even go up the slope to pull logs out, have to use the little 4x4 kubota and bring them down a little piece at a time.



Edited 1 time(s). Last edit at 02/06/2012 09:52PM by ReubenT.
Re: basic steam system design info?
February 06, 2012 10:40PM
Hey Ruben,

For what your doing, there is no need to go bellow 20% to 25% cutoff, a range of cutoff from 25% to 80% will give you all that is desired. Use the 80% to get going, then once moving, cut it down to 33% or 25%, use the throttle to adjust power output.

With the single cylinder, like the Steam Traction engines, you will want to have an indicator of where the crank is. It will need to be stoped in a position where it can start up on its own again or you will have to push it or turn it somehow to get it going.

The traditional way is to use two cylinders with their cranks set at 90 degrees, any cutoff of over 60% or so will give self starting, no clutch required, no idle, just open the throttle and go.

Maybe others will disagree, but steam and aluminum don't seem to get along very well, steel or cast iron are best. You can get chunks of cast iron that can be whittled down by you to whatever shape you want it.

As to engine construction look at the pictures in this thread of this very light and strong engine design.

[steamautomobile.com]

It uses small piston valves and ran at low speeds, one of the historic engines went down with the Titanic, it was being shiped over here at the time.

Caleb Ramsby
Re: basic steam system design info?
February 07, 2012 03:35AM
Ruben, You should avoid plain barings in a self starting low spead engine. You need speed to make a lubricant work with plain barings.
Re: basic steam system design info?
February 07, 2012 12:03PM
Andy,

What's the problem? Shell bearings are available in a huge number of sizes and are infinitely cheaper, more reliable and better than ball or roller bearings. Not to forget much less inertia and when they go, very little damage is done unless one keeps abusing them.
Put a small oil pump on the burner blower shaft and let that keep the oil film up. A couple of check valves and install it parallel to the main oil pump in the engine.
The blower should be kept running at slow speed when the fire shuts off anyhow to purge the steam generator. Or do you like to remove the soot with a big blast?

Jim
Re: basic steam system design info?
February 07, 2012 11:44PM
Jim, I thought Ruben was talking about steam engine main bearings.
Re: basic steam system design info?
February 08, 2012 01:14AM
I'm going to make it as simple and cheap as possible and still have a reliable machine, so I'll use whatever I have or what looks like will work for me, unless someone tells me it absolutely won't work.
I was measuring the stuff I have, and the flywheel has a hole in just the right place to put in a crank pin, but I'll have to reinforce the hole with a steel block bolted on it since it's not thick enough to hold the pin from turning sideways at that point. The flat pulley bore, shaft, and pair of block bearings are all the right size. 2.5" dia. even though I didn't buy them with the idea of putting them together. The biggest time consumer may be setting up a governor to control cutoff. I'm thinking a weighted pair of arms on a sliding sleeve to control a half stevenson link, (half because I don't need reverse, (it probably has another name but anyway) and figure out how to adjust the control position manually. I was thinking of going down to 0 cutoff to give slow idle capability, and a non self starting single cylinder is OK, I can put an electric starter motor on it, like a rubber wheel on the motor shaft that swings up against the flywheel.
Yah, aluminum is soft, and starts getting a lot softer at 800F or so, melting at 1100. However I think I'll try the aluminum cylinder housing because it's easy and won't take a lot of work to poor the form and machine it. (interesting experiment anyway, after thinking about it awhile I just have to try it) and has a different expansion coefficient as well so may not do well with a cast sleeve locked into it. But I'm aware that it may go bad so I'll plan on doing it in cast iron later. I have a 55 gal barrel cupola ready to do iron casting as soon as I build a charcoal kiln to make fuel for it. Quite tall, 2 barrels lined with refractory and a gas powered blower for air, (old push type street vacuum) an extra tank on top with lid and a sideways chimney with blast air preheater on it. had to make stairs to carry stuff up to load it. Even made my own motor powered sand mauller and it works good, makes the greensand nice and sticky, holds shape very well.
Re: basic steam system design info?
February 08, 2012 01:45AM
Hi Reuben. I have seen old traction engines using simple block barrings. But it
depends on the starting torque and how often. Solid block plain barrings do not
take a lot of loading at or near 0 RPM. Lubricants do not form, (I can't
remember the word,) until some speed is reached. Sorry I don't remember all the
details. It's been a long time sense I researched them. The basic problem is
that without the oil film forming you basically have metal to metal and scoring
occurs destroying the bearing. I have seen some recent developments that clam
high starting torque capabilities using exotic materials. I am not sure how you
will be running you engine. You can search the web for info on plain barrings.
It is up to you to decide their applicability to your project.

Also Ken might be able to tell you more about plain bearings. For my goals I
ruled them out a long time ago.

Hope this helps.

Andy
Re: basic steam system design info?
February 08, 2012 03:38AM
Hi Andy,

Hydrodynamic lubrication is the word [phrase] you are looking for. Plain bearings like in old traction engines is what Reuben is looking for.

Hi Reuben,

Lindsay Books [Google/Yahoo it] has good books on babbitt bearings. You pour 'em yourself, melting the babbitt metal on a kitchen stove, and set up the bearings so you can adjust for wear when they clank. Grease now and then or put on oil cups. I bought a brick of babbitt recently from mcmaster.com for cheap; plan to use it for my eccentric bearings. One brick makes tons of bearings, and you can recycle the metal from worn bearings. I also got some "casting putty" [Babbitrite brand] for damming up the journals and bearing boxes for the pour. Re-useable; one brick of that also does a zillion bearings. Babbitt was the miracle bearing material of the 1800s, still good stuff today. The different metal molecules in it wear different, so the surface develops a texture that retains oil/grease. 1800s Teflon. Today they still "plate" gas engine bearings with it. Plated thin so you have to buy a new one in a few years, no adjustment or repair. Pour your own solid Babbitts, and your great-grandkids will be repairing/re-pouring and running 'em.

Mcmaster also has cast-iron billets, the best stuff for slide valves and slide valve seats/platforms. Recently I got a foot long 3.5" diameter round of malleable/nodular cast iron from them, and cut slices for pistons, slide valves, and slide valve seats on the bandsaw. One chunk makes a lot of engine parts. Works out to a couple bucks a part, lots cheaper than gas or diesel engine parts at auto parts stores. "Cast iron on cast iron" is what the old steam books say is best for slide valves and pistons/cylinders. The old books were written by and for folks who designed, built, and ran real steam engines every day, for decades, and made a good living doing it. With wood fuel and some ingenuity and elbow grease, you can do the same thing today.

Peter
Re: basic steam system design info?
February 08, 2012 07:01AM
Andy,

He is.

Jim
ben
Re: basic steam system design info?
February 08, 2012 08:50AM
Many of the earlier engines used marine style rod AND Bronze box bearing,,,Ben
Re: basic steam system design info?
February 08, 2012 08:24PM
Hi Ben,

Many steam guys prefer bronze bearings to Babbitt. Bronze does make excellent bearings. McMaster and other suppliers sell various bronze alloys, including SAE 660 (very tough stuff) and SAE 841 (sintered and oil-impregnated; releases oil with heat). Buy bronze rod stock, machine to fit any diameter and width of journal desired, run in and adjust as needed. The McMaster catalog's plain bearing section also gives the max load and speed figures for designing plain 660 & 841 bronze bearings. It is a good way to go.

A few years ago 2 Babbitt enthusiasts (not from this forum) talked me into trying Babbitt; I am interested to see how it works out. They said that Babbitt has a bad reputation among many because some guys use the cheap/soft leaded Babbitt alloys and/or overload/under-lube it. This has been going on since Babbitt was first introduced. Unleaded tin babbitt is the good stuff. The Lindsay Babbitt books detail many different ways to make good and bad babbitt bearings. There is lots of Babbitt information available free from "the internets" too. Bearings are a deep and very interesting topic.

Larger-diameter plain bearings get up to hydrodynamic "perfect lubrication" surface speeds at lower rpms.

Peter
Re: basic steam system design info?
February 08, 2012 09:09PM
I have that book on pouring babbitt, will do it if I need to. I think MBL will either partially or completely solve the starting torque issue with bearings. since it forms a film on the surface of metal and makes it super slick. But I've seen the rollers in bearings break up under too much side loading, don't think any lubricant would help that, so the limit is there. My sorghum press made about 1925 by Chattanooga plow company (IH brand because they bought the company prior to that) has the bronze blocks for bearings and that thing runs under several tons of pressure when squeezing a bundle of stalks flat. I'm ordering a crucible for bronze, and it looks like I should get my cupola running, with that I can cast all the cast iron I need in whatever shape needed. I'd feel like I was wasting money if I bought any when I have the furnace almost ready and lots of scrap around. I built it with the idea of making my own engine anyway but got distracted by other stuff. I set out to do some logging to make money for ordering parts and supplies, then just tonight a good friend (retired doctor) handed me a gift of $300, so I'll get started ordering stuff.

An idea I had on using aluminum is to insert a cast iron plate for the bearing to run on. I think cast iron for the whole thing would probably be better, but I'm not sure enough experimenting has been done with aluminum.

Hmmm. Fraid I got too many ideas poppin up in the noggin. I'll do some thinking and drawing and see what I can come up with. Besides just doing one myself I'm halfway interested in figuring out a way to make it so as to help someone without a foundry make it. Would be kind of hard to do it without a lathe though, but I got one for $400 that's very old, line shaft drive with electric adaptation, but in decent shape, built in the days when steam was running about everything. So a lot of money isn't really necessary to get stuff going.
Re: basic steam system design info?
February 09, 2012 09:06PM
Going to need several bearing joints, I could use either brass or babbitt. If brass I'd melt down some old radiators, they're supposed to be copper tubes and brass tanks I think. not an alloy made for bearing service but I suppose it would work. Although it's going to be a bit softer than bronze. Concerning babbitt; what grade is good for the job? do I need the expensive stuff? high tin content for heavy service at $17 - lb. and an overrun discounted one for $12-lb. (best for high load bearing I suppose) Basically 3 types available for light medium and heavy service. (I'm looking at [www.rotometals.com] ) I'm thinking the pillow block bearing would be fine on the pulley end of crankshaft but the flywheel end with crank will get the 1200 lb load momentarily at 90 dg crank position. I think the block bearing has ball rollers in it which may not take it. (A sawmill I have used 2 pillow blocks on the shaft where it had about 1600 lb side load, and they gave out after a few hundred hours, replaced with roller bearings in oil bath and it's still going with a couple thousand hours on it) I think a trailer hub roller bearing will do it because it handles it on the road, so I'll try that for the crank end.
Re: basic steam system design info?
February 10, 2012 05:52AM
Needle bearings are cheap if your willing to use hardened shafting?
Re: basic steam system design info?
March 04, 2012 12:48PM
Reuben T, Get with me sometime off site here to go over steam sterilization of soil. As I understand it there is a problem with carbonizing the soil if the temperature is over 180 degrees F. The soil sterilizers that use steam mix the steam with air and use a Rootes blower to force it through a false bottom in the sterilizer wagon. There is a big market for steam, if we can make it work, now that Methyl Bromide is being outlawed. Tom Kimmel
ben
Re: basic steam system design info?
March 04, 2012 12:55PM
Tom,,,give me a ring,,,re a spare roots blower,,Ben
Re: basic steam system design info?
March 04, 2012 07:56PM
If you can make it to Lancaster County, PA, there are quite a few people doing steam sterilization for Amish farms, using traction engines. I talked to a member of the family that runs the Cattail Foundry, and takes their traction engine rig on the road for weeks, going from farm to farm. Last spring they had more business than they could handle. I also watched this teenager back a traction engine, with a trailer, into a parking space at the Thresherman's reunion at Kinzer. Hard to believe.
Re: basic steam system design info?
March 05, 2012 06:22AM
Actually, it isn't that hard to get reasonably priced, well-used Roots blowers. The 3.8 liter Buick V-6 had a blown version that featured an Eaton 3 lobe Roots blower. While not the biggest production variant of the engine, there should be enough of them in salvage yards to make procurement easy. I've considered these as a way to feed air to a boiler, at least for a first generation model. The housing is a bit large and heavy, but with the blower you have the potential to throttle down the gas outlet and apply higher pressure to the boiler housing if you want to experiment with increasing heat transfer rate. I'm sure more pristine versions are available in boxes from dealerships, at substantially higher price.

Ken
Re: basic steam system design info?
March 19, 2012 05:07PM
Caleb, back on 1/29 you were talking about port sizing. But I notice you did not include any mention of when the steam is going in during the stroke. You used the entire stroke when figuring piston speed, etc. Would the port size required be less if, for example, you had a bash valve with 10% cutoff?

Thanks, Roger
Re: basic steam system design info?
March 19, 2012 05:30PM
Hey Roger,

Well, yes and no.

The old school recomendations were acquired from what worked best on working engines. The steam velocity and piston velocity are averages, but they take into effect the smaller port opening at shorter cutoff, which is usually used at higher speed.

About 100 years ago they were having the argument that the short cutoff occured when the piston speed was low because of the cranks effect, others argued that the port isn't open long enough for the steam to speed up. That same argument is still going on now.

Speaking of bash valves in particular, most all of them that I have studied were designed to run at very high pressure. If your boiler pressure is high enough above what you require in the engine then it isn't a huge issue, but larger ports and valves make for engines that can produce more power then those that don't.

Caleb Ramsby
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