Request For Comment

[aubrey]

Hi Everyone
Problem: Need mechanical energy source in Malawi but petrol/diesel VERY expensive and electricity not available.
Looked at steam - Too Dangerous for the local level of expertise.
Looked at Stirling and Atmospherics as well - not enough grunt.
Came up with the following design which will give me power (how much I dont know) WITHOUT needing a boiler.
The fuel will be wood.

Theory on how it works:
Normal crank, conrod, piston and cylender.
The crank has a cam (as opposed to an eccentric) to operate the port sealer/water injector via a conrod.
The port sealer has a spigot on the front which engages the water injector piston (after the port is closed).
The water injector piston moves forward, closes the hole to the water supply hopper, builds up pressure which forces the water thru the one-way valve into the hotbox steam generator.
The hotbox steam generator has the fire made around it and is hopefully just about red hot at all times.
The injected water turns to steam which pushes the piston/conrod down which turns the crank.
At bdc the cam retracts the port sealer (the water injector piston moves back opening the port to the water supply and is re-filled) and the piston moves up, exhausting the steam.
Just before tdc the cam moves the water injector piston forward completing the cycle.

The beauty is that there is no boiler to blow up! This is VERY important as the people who will operate the machine are at best semi-literate and even if the thing overheats or runs dry, I cant see an explosion happening.

Connecting 2 together 180 degrees out of phase would give a constant power stage at the flywheel.

Please remember that this is not a desktop model but will be used to power irregation pumps, sawmills and the like in a very poor and rural setting using wood as the fuel source. Currently they are irregating thier crops by bucket from a well point at least half a mile away. They simply dont have enough manpower to get enough water to the crop and the result is a food shortage.

What I would like is for the members of this forum to rip the design apart and tell me what is right with the design, what is wrong with the design and how to rectify the problems.

Also, advice on what material to use would be appreciated. (ie could I use a VW Bug cyllender barrel and piston). Please bear in mind that average annual income of these people is less than $100 a year and the more "scrap" I can use, the better.

Thanks a lot guys, look forward to hearing from you.
Best Wishes,
Aubrey

[aubrey]

Before going any further, I need a proof of concept.
Went into the local lawnmower repair shop and got an old 4 stroke Briggs & Stratton lawnmower motor (donated).
Now all I need is a piece of 2 to 3 inch pipe to use as the steam generation vessel.
I have an old VW Bug brake master cyllender I can use as the water injector.
The steam generator can be screwed into the spark plug hole.
I'll have to make up some sort of cam on the putput shaft to operate the water injector.
Another cam can open both existing inlet and exhaust valves so that they operate as the exhaust port.
May need a heavier fly wheel (the alluminium one wont be worth much)
Bodge up a frame to mount everything on, suspend it over the barbeque and see what happens.
I see a busy week-end ahead!
Aubrey

PS. Just got off the phone to a pal with an aluminium foundry who has a contact with a cast iron foundry about 3 miles from where I live (didnt even know it existed!). The cast iron guy says casting will not be a problem.
Looks like I may have a nice Christmas present for Nyrenere (my Malawian friend)

[handlewanker]

Hi Aubrey, if you are concerned about safety, then go back to basics and I mean 1700.
The steam engines then were atmospheric engines and the steam pressure was about 2 psi, which was not enough to blow your hat off.
These engines worked on the principle of flooding a large diam cylinder with low pressure steam and then condensing the steam to cause a vacuum to pull the piston up the cylinder.
This is very basic engineering and the piston seal was usually a leather skirt that was immersed in water to stop the air getting into the cylinder.
The boiler was often made of lead as it only had to bring water to the boil and pressure was not required.
The beauty of the set up was that it could be fired by any fuel that would burn, even solar power.
If you are unfamiliar with the principle just look up Newcommen or James Watt on the 'Net.
These engines do not require a crankshaft or flywheel to operate when pumping water, and could be operated by the village idiot if required.
The beam engine is a typical design type.
Ian.

[CJL5585]

Aubrey,
I am somewhat illiterate on steam engines, but I wish you the best in your quest for a power source.

Good Luck.

[handlewanker]

By the way Aubrey, once this "engine " has been made and installed, will you be around to keep it going?
If not, how the hell will a bunch of ignorant people be expected to even understand the goings on in a mechanical device that is working at the limit of it's capacity when it breaks down?
The very fact that water injection is contemplated is the first source of breakdown.
The simplest device is the most complicated to design and make.
SOMEONE has got to be trained to be able to take it apart and reassemble it without too many bits left over.
I see you mentioned a foundry just down the road.
Are you contemplating re-inventing the wheel?
If the sole purpose is to bring water from a distance then a simple viaduct filled with a water wheel or wind mill driven archimedean screw will be cutting edge technology in this instance.
There must be a river or stream nearby which can be dammed to supply water power?
I don't suppose the whole tribe could be re-located to the water source thereby killing all the birds with one stone.
What fuel are you going to use to power it?
If it's wood, how are they going to cut enough wood without deforesting the immediate area and so adding to the further advance of the deserts as has happened in other areas.
I would strongly advise mounting the engine on a mobile trolley, like a traction engine, so that as the wood is depleted in the immediate area the engine can be powered up and so go foraging for it's own supplies on an ever increasing circle.
I hope you don't think I'm unjustly picking holes in your project. If you can overcome any criticism in this endeavour then it will win.
Ian.

[aubrey]

Hi Ian
They are going to have to do it themselves after a little bit of training.
These people are definitely not "ignorant". They survive in an environment that would kill most of us in a matter of weeks.
They simply do not have the exposure to technology that you or I do and therefore do not understand how dangerous leaving a pressure vessle unattended could be.
Therefore, dont give them one.
They simply march to the beat of a different drum (possibly you have heard the expression "African Time"? I'm sure that rural south Americans have a similar concept.).
As to the "water injection", my trial unit will use a VW Bug brake master cylender (simply because I have one lying around). Production model will probably have a leather sealing washer simply because they will be able to make a replacement locally when they need one.
Some of these guys are very intelligent and ingenious in thier own way. In one of the towns I saw an arc welder that had been made using 4mm fence wire wound with insulation tape to make the transformer coils. And best of all is that it worked.

The area is very sandy and although there is enough water, it is at least 3 to 4 meters (10 - 12 ft) down. We have to get it UP! Making a dam doesnt work because the water soaks away faster than it is flowing in.
There are no rivers or streams as such because any surface water simply seeps away and the wind is not very strong - when it blows.

As to fuel, these people have been carrying out good conservation practices since they settled the land which was before europeans colonised Africa and the Americas.
Normally, the area around the village is devided into 4 sections (north, south etc) and each year, only 1 area is used. Also, some trees are marked and are not allowed to be harvested so that they can grow into "big wood" for use in the building of housing. So every section is allowed to re-generate for 3 years and harvested for 1 year. And if you have to walk 4 miles to get wood then that is what you do.
The whole thing is controled by the headman who simply kicks you out if you dont live by the rules. Therefore you live by the rules, no questions.
The only time you get de-forestation is when someone from outside comes in and strips the natural resources and sends them out of the country. Nigeria and Congo are good examples of this and guess whose dollars and euros and rands buys the timber. Sometimes I have to wonder as to who is more civilised - them or us.
At the present time, the children do the water carrying and when it is hot, ALL the children are roped in because if the crop fails, the village starves - simple fact!.
This means no school and that is what pi$$es me off but I can see the point that food comes first and all else is second.
So the bottom line is that it must be simple enough to repair in the field, cheap enough to be sponsored and safe enough to be used by the local population.

As to "unjust criticism", bring it on!!!
Maybe you will uncover something important or vital that I havnt thought of and maybe you can get a better insight into how other people live.
And hopefully it is a win win thing.

Anyway, thanks a bunch for the interest and comments.
Best
aubrey

[handlewanker]

Hi Aub, I lived in South Africa for ten years and South West Africa in the Namib for another ten years, so I know where you're coming from.
Probably the term "ignorant" was a bit strong, but it meant a lack of technical understanding beyond 19th century technology.
As far as pressure vessels are concerned the method of atmosperics is to use low pressure steam, 2 psi, to evacuate air and condense it to create a vacuum. This is extremely low tech and even a child can manage it.
This method was used to pump out deep mines in the early years before high pressure boilers came into vogue, but I expect you are familiar with the history of steam in the Industrial revolution.
From your description it would appear that the people are pretty well organised.
I wouldn't go a bundle on lashing up a Heath Robinson device just to see the wheels go round.
Just looking at the design indicates that with the proper proportions for piston area, fire-box capacity, and injection quantity will make it work, as this method is the heart of a monotube boiler and engine.
Even if you get the VW set up to work it will not be reliable and you will have to go back to the drawing board to design something that is practical and is able to be made for next to nothing, otherwise you will be labeled as the "white man's revenge".
The VW is labeled as "Hitler's revenge".
Ian.

[aubrey]

Hi Ian,
Sorry about the "soap box" trip - Definitely an over-reaction on my part - appologies!!!
Back to business.
I'm not too knowledgable about the various technical designs of the steam engine and that is why I am asking for help.
The atmospheric design needs to be rather big from what I can see and the point you brought up about being mobile is actually very relevant in this case.
Its going to have to be small enough so that 2 people could lift it onto an ox cart to transport around.
As to the VW parts, merely looking for a source of components (they can be bought 2nd hand at scrap metal prices).
As to the "Hitler/White Mans Revenge" part, there is a device called a treadle pump which was introduced up there. Consists of 2 pistons, 2 pedals and a couple of non-return valves. Works very much like one of these stair climbing fitness machines. The problems: the one way valving is "delicate" and wears out quickly and as the seats are part of the body casting, once they are worn, throw the whole unit away. The pistons are pvc but the cylenders are stainless steel - expensive! I think that whoever designed them made a lot of built in redundency to create an on going market for them.
Anyway, its now 7:45am local and I'm heading for the workshop.
Best and Thanks
Aubrey

[epineh]

Is there a total lack of wind there? The windmills I have seen use a very large diameter blades, with a simple crank arrangement, and a simple up/down piston pump, they work surprisingly well even with light winds, very simple to make and maintain. Just a thought.

Russell.

[thkoutsidthebox]

Hi aubrey,
Best of luck with this project, its very interesting.

Im just wondering how your calculating the piston diameter in relation to the size of your steam chest, and the size of the steam storage, and generation rate, in relation to the expected piston movements (rpm) ?

I dont know anything about engineering one of these but in your pic above the piston looks very large compared to the steam box. I'd think that maybe the steam box should be larger....

You said:

Originally Posted by aubrey The area is very sandy and although there is enough water, it is at least 3 to 4 meters (10 - 12 ft) down. We have to get it UP! Making a dam doesnt work because the water soaks away faster than it is flowing in. There are no rivers or streams as such because any surface water simply seeps away and the wind is not very strong - when it blows.

As I mentioned above, I dont know about engineering one of these, so please excuse my lack of knowledge. Will there be enough water being pumped to both supply the unit, and supply sufficient water to irrigate the required area?

Will you have to build an aqueduct system aswell to prevent the pumped water soaking "away faster than it is flowing in" before reaching the irrigation area?

Last question .....what size area are you hoping that one of these could be used to irrigate (Pump rate liters/min)?

[handlewanker]

Hi Aubrey, No problem with the "retoric from the pulpit" just makes good reading, but "hoisted up on an ox cart by two people'? I don't think this would be a good idea.
First off it would severely limit the weight and size that you can make it to.
Secondly it would have to be fired up and cooled down which would make it awkward to use.
Personally I would make it as a fixed in position with the infrastructure around it to keep it happy, also someone will "adopt" it and keep it lovingly tended to make it reliable.
Some people just get "broody" that way with machinery.
If it simply had to be moved I would make it so as to be towed behind the ox cart with it's fuel store and paraphanalia to make it self contained.
Looking back on the designs of the model railway engine builders, the injection pump should take the form of a displacement plunger pump where the piston doesn't actually touch the cylinder bore but displaces the water by it's intrusion into the pumping space.
This will prevent lack of lubrication on the pump piston from failing it prematurely, or causing the "boiler" to coke up due to oil being burnt there.
These pumps are usually driven by the axle of the loco and have to pump against boiler pressures of about 80 - 100 psi.
They are a bronze casting with a stainless steel ram and have a long wear life, very reliable. Gland sealing is effected by either Viton "o" rings (high tech, not recommended due to hard to get etc) or just greased braided yarn,cotton fibre etc.
The design is very simple and can be cast in the backyard type foundry and machined in very primitive simple machinery, even a drill press.
I would recommend that the firebox be made from cast iron so that it can be fired up and hold the heat while the water is just injected at a controlled rate to give the flash steam volume.
If the firebox/boiler is cast as one piece, it can be made to a simple pattern, by the dozen, with minimum machining, to enable it to be bolted on and off for simple replacement when it scales up or corrodes out.
The piston cylinder bit may be tricky, due to lubrication requirements.
Here I would use a large two-stroke engine (vespa scooter 150CC ?) with the transfer ports blanked off so that piston lube can be added to the steam supply and totally exhausted to prevent boiler contamination, and crankshaft lube contained in the sump off side.
Using a car type engine has too much mass and lubrication of the bores and big ends and main bearings would be a serious problem, where hot steam and water in quantity were present.
In this endeavour I would strongly advise contacting someone in the live steam model railway fraternity, and pose the scenario that you intend to pursue.
Ian.

[balsaman]

Leonardo DaVinci was working on a "steam canon" in his day that operates in a similar fashion. Injecting water into a heated chamber and utilizing the rapid expansion to fire a canon ball....

I don't think a working canon was ever built, but I can see this aplication may have a chance.

Eric