Steam power, does it work?

Discussion in 'Spare Parts, Tools & Product Developement' started by jawnn, May 10, 2012.

  1. jawnn

    jawnn Member

    I know this can't possibly work very good, so ca you tell us why?

    I think I saw a velomobile that uses steam, but with the wight of water and batteries, how good can it work?

    Are their any videos of one working?

  2. loquin

    loquin Active Member

    It's a power-density thing.

    Steam could be used to power a bike engine. Ideally, the steam would spin a two stage turbine, (steam output from the high pressure turbine would be fed into the input of the low-pressure turbine) where the shafts are coupled, and the shaft of which would be geared down to something usable to drive the bike. But, you would probably need several hundred PSI steam pressure. So, you have an externally fired boiler, a water source, a low volume high pressure pump to inject water into the boiler to maintain the liquid level a burner, a fuel tank... Now, an external combustion engine (which a steam engine is) is much cleaner than an internal combustion engine. Of course, if you're trying to use batteries and an electric heating element to generate the steam in the boiler, you'll have issues with electrical storage capacity.

    Steam has it's own issues. First off, it's corrosive - especially if it's not pH neutral. Second, any minerals in the water get left behind in the boiler as the water boils away, so there are issues regarding scaling (mineral deposits when the mineral levels get supersaturated in the boiler water.) You have to have some sort of level control, to automatically keep the hot water level in the boiler stable. You have to fire up the boiler well in advance of actually going anywhere, too.

    You could use a piston-based engine, (probably based on a 4-stroke gas engine) but, in order to get any sort of efficiency, you would again want a two-stage design, with essentially two separate engines with mechanically coupled output shafts, where a small cylinder high pressure engine is used as the primary stage, and it's output steam is fed in to a large, low-pressure steam engine used as the second stage. Think of using a Honda GXH25 as the primary stage, and a GX160 as the low-pressure stage. 200 psi into a 1 inch cylinder, and 50 psi into a 2 inch cylinder. Both would generate the same thrust...

    Steam can be quite efficient, but, at larger scales - think power plant scales. Even at locomotive scale, internal combustion engines are more efficient... (A diesel-electric locomotive can produce much more power than a steam locomotive, for instance.) As the power plant gets smaller and smaller, the efficiencies get lower and lower.
    Last edited: May 10, 2012
  3. motorpsycho

    motorpsycho Active Member

    steam can make gobs of low end torque.
    the problem would be carrying excess amounts of water, a boiler, and a fuel source (coal or wood) to heat the boiler. and then you'd have to have a decent size combustion chamber with a piston and all that stuff.
    Now, if you could go to a battery powered "fuel" source to heat the water it would be easier to carry than a bunch of coal or wood.
    but you'd still have the weight of the battery, the boiler and the water.
    I don't know, maybe there's an easier way, but probably not.
    Steam can makes lots of power, but the downside is the weight from all of the resources needed to make it work.
  4. I have seen videos on youtube of steam powered bikes. Most had very large, old fashioned boilers and had solved the gear question by using a piston rod connected directly to the rear axle via a crank throw sticking out on one side of the wheel and a shorter throw crank on the other side of the wheel to operate the valve. A steam piston engine has so much torque, no gear reduction is needed. A modern, very small tube, flash boiler fired with propane or diesel/kerosene could be small enough to fit within the frame of a bike and produce enough steam to run the tiny bore, fairly long stroke engine needed to move a bike right along. Using only distilled water cures the mineral-deposits-in-the-boiler problem, but without a condenser, a good amount of water will need to be carried for any signifigant range.

    Yes, any competant machinist could fashion the engine, after all, the cylinder could be made of a length of thin wall steel pipe. The steam inlet/exhaust valve would be a little more difficult, but certainly do-able. The boiler and water pump are the hard part. A working pressure of well under 100 pounds would be adequate, and make passing a low pressure boiler inspection easy.

    It wouldn't be dead easy, but it is certainly something to think about. A now departed old steam fan I knew built a functioning 1/8 scale steam locomotive from scratch in his basement and drove it on home built tracks around his lawn each Summer, sitting in the tender and grinning ear to ear.
  5. corey872

    corey872 New Member

    It would certainly be a neat project. I guess I'll go against the grain a bit...I don't think distilled water is really needed...I don't think I've ever seen a steam engine run on distilled water...though plenty run on water out of a hose, rain water, river water, or what ever else comes down the pipe. Just blow down the boiler properly and it's not a problem. You should never run the boiler dry, so there will be much less chance for scale.

    As for power, steam engines are some of the most powerful beasts around...1930's/40's steam technology can still generate almost 2x the 'horsepower' as a modern diesel electric engine...some steamers topped out around 7,000hp, modern diesel engines are starting to get into the 4,000+ range.

    I'd throw out any hope of 'converting' a gas engine. The beauty of steam is the ability to push the piston both ways...that's not really feasible with a gas engine. Plus, a gas engine uses iron rings in an iron cylinder...which can pose lube issues for a steam engine...not insurmountable, because that's what the old timers used. But you might as well take advantage of modern materials. You could probably design so the temps are compatible with teflon seals which cure a whole host of problems and even give the possibility of condensing the steam in a closed loop system.

    A double or triple expansion engine (even quadruple if you have the space) would boost up efficiency substantially.
  6. wheelbender6

    wheelbender6 Well-Known Member

    The Panama canal was built with steam shovels. It works. We just have better sources of power now.