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Return to: Steam Power
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#Post#: 211--------------------------------------------------
Re: Lawn Mower Engine conversion to Steam
By: crazyguy Date: August 10, 2013, 6:58 pm
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i watched your videos on the monotube boiler.
why cant you gravity feed the water.?
how big of an engine can this feed.,?
i would love to make this a backup emergency generator instead
of gasoline powered.
#Post#: 212--------------------------------------------------
Re: Lawn Mower Engine conversion to Steam
By: lynx wind Date: August 10, 2013, 9:01 pm
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Steam is very different from a gasoline engine. Timing is just
as crucial but different. You want the steam valve just
cracking open at TDC and closing at about 25-30% of the stroke
on a single acting cylinder. Uniflow ports are uncovered at 85%
of stroke near BDC. An auxillary exhaust valve is possible with
this conversion and can be open until the piston is at about 80%
of the way back to TDC. You want a little compression to
cushion the piston, or you can crack open the inlet at 1-2
degrees BTDC.
Air is not a great simulation for steam. It doesn't expand the
same, and doesn't give up energy as heat like steam.
A monotube boiler is just a coil of tubing. That is a whole
other discussion. Sizing, velocity, placement, etc....
You can't gravity feed a monotube boiler. The feedwater has to
be forced in under pressure.
#Post#: 213--------------------------------------------------
Re: Lawn Mower Engine conversion to Steam
By: burnit0017 Date: August 10, 2013, 9:06 pm
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Hi, I would check out the video's Lynx posted, good info. The
pressure inside the boiler is higher than the reservoir, I think
a gravity feed might be a problem. Because I am using the F&P
with a MPPT the load created by the (I squared R) should not be
a problem. I tested the RPM at 100 psi and it was over 700. At
50 PSI it was over 500. I really do not know how well this work
but when I was manually testing the F&P MPPT I was able to
generate a max of 7 amps at 12 volts using a 12 volt deep cell
as load. It should be a week or two before I can finish the
boiler. This is a first attempt for me and I am wondering if the
size mono tube I plan on building will supply enough steam, I
plan to try make it expandable if needed. I will be using a
rocket stove for the fire box.
The backup generator is a good idea. The engine modification was
not that hard, the boiler looks to be more of a challenge.
#Post#: 214--------------------------------------------------
Re: Lawn Mower Engine conversion to Steam
By: burnit0017 Date: August 11, 2013, 5:36 am
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Hi, are there any diagrams showing the position and flow for a
uni-flow ports?
Hi, I found one.
http://www.steamcar.net/movies/uniflow-engine.gif
#Post#: 215--------------------------------------------------
Re: Lawn Mower Engine conversion to Steam
By: crazyguy Date: August 11, 2013, 6:34 am
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you cant do that with an old gasoline engine.
funny my Mr. Coffee has gravity feed for its water and it makes
steam. does it have some kind of valve.?
#Post#: 216--------------------------------------------------
Re: Lawn Mower Engine conversion to Steam
By: burnit0017 Date: August 11, 2013, 7:05 am
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http://opensourceecology.org/wiki/Steam_Engine_Design
http://opensourceecology.org/wiki/Steam_Engine_Design
Hi, interesting site. The gravity feed may be a different
design, it looks like a gravity feed would not work with a mono
tube boiler.
#Post#: 217--------------------------------------------------
Re: Lawn Mower Engine conversion to Steam
By: burnit0017 Date: August 11, 2013, 7:29 am
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http://www.backwoodshome.com/articles/images/goebel43_f2.jpg
Hi, more complex, it looks like a gasifier fire box.
#Post#: 219--------------------------------------------------
Re: Lawn Mower Engine conversion to Steam
By: crazyguy Date: August 11, 2013, 10:20 am
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Now that "bump valve" is interesting. No cam or timing. steam
comes in and when the cylinder gets to the top "bump" and it
goes back down.
#Post#: 220--------------------------------------------------
Re: Lawn Mower Engine conversion to Steam
By: burnit0017 Date: August 11, 2013, 11:00 am
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Hi, what letter are you referring to??
#Post#: 222--------------------------------------------------
Re: Lawn Mower Engine conversion to Steam
By: lynx wind Date: August 11, 2013, 5:00 pm
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Bump valves work for a short time. They are also called "bash
valves". The discussion really deserves its own topic.
The only proven designs out there operate at 1000-2000 psi,
cutoff is very brief and the valve is actually shaped like a
mushroom cap to create a larger seat and larger opening with
very little lift.
The ones you see out there in YouTube land will work for a while
until the piston is deformed or punctured. Timing is achieved
on the low pressure versions with a long extension tube and has
to be velocity matched with the piston speed and length of the
passage. That passage forms what is called "clearance space"
which is something steam engineers try very hard to avoid.
If the piston simply comes up and bumps a ball bearing it will
refuse to kick over. The torque from steam is instant. The
steam has to enter at or after TDC. Ball bearings make bad
bash valves in the long run because they deform and then quickly
deform the seat within a short period of time.
There are some other clever ways around this problem but I
haven't seen them in action.
My opinion is that the bash valve is best used with high
pressure steam in a purpose built uniflow engine.
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