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 Post subject: Pump to convert to a Steam engine?
PostPosted: Wed Nov 23, 2011 9:39 pm 
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Warming the Engine
Warming the Engine

Joined: Mon Jan 11, 2010 4:07 am
Posts: 66
Hey all, it's been awhile.

Life has taken me far afield from the steam hobby, but I'm circling back around again and trying once more to put some kind of steam boat together.

Since I have discovered that a traditional steam engine is simply out of my reach, I have been looking for alternatives that would still be acceptable. I noticed that one of the well known steam boats on the west coast, the Otter, is basically run with a converted refrigeration compressor. Not very attractive, but functional.

I was looking around, and came across this over at harbor freight: http://www.harborfreight.com/145-psi-3-hp-twin-cylinder-air-compressor-pump-67697.html

It's cast iron, so likely to withstand some good pressure (rated for 145 PSI output pressure) It says 3 horsepower, but that's the rating for the electric motor intended to run it as an air compressor. I'm curious as to what you all think it might generate as a steam engine. It would have to be modified with a steam chest (or piston valve and appropriate piping) but it looks like it might do well. And for not much money either.

What do you think?


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 Post subject: Re: Pump to convert to a Steam engine?
PostPosted: Wed Nov 23, 2011 11:35 pm 
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Full Steam Ahead
Full Steam Ahead
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Joined: Fri Nov 20, 2009 5:34 am
Posts: 946
Location: Phila PA USA
Boat Name: Margaret S.
A two cylinder inline air compressor can be converted to steam engine service very easily, so can almost all gasoline and smelly long-chain hydrocarbon engines too. There are many plans to do this conversion, some can even be done without any machine shop equipment.

The compressor you mention is about 11 cubic inch displacement, and with 100 PSIG steam @ 400 RPM you can get about 2 HP maximum. That should be OK for about a 16 foot long launch.

Picture is a 4.7 cubic inch chain saw engine, converted to steam for a canoe.


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File comment: 4.7 cubic inch two stroke gasoline to steam conversion.
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 Post subject: Re: Pump to convert to a Steam engine?
PostPosted: Thu Nov 24, 2011 12:37 am 
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Warming the Engine
Warming the Engine

Joined: Mon Jan 11, 2010 4:07 am
Posts: 66
Interesting. You wouldn't happen to have a link to converting a gasoline engine? I happen to have a push lawn mower (briggs and stratton 6HP gasoline) that quit over the summer due to never being maintained. i suspect the spark plug needs to be replaced, but i was given a free replacement before I had the chance to repair the old one, so now I have a spare motor.

Although it's probably a 4 cycle, so I don't know if that would work...


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 Post subject: Re: Pump to convert to a Steam engine?
PostPosted: Thu Nov 24, 2011 5:00 am 
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Full Steam Ahead
Full Steam Ahead
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Joined: Fri Nov 20, 2009 5:34 am
Posts: 946
Location: Phila PA USA
Boat Name: Margaret S.
A 4 stroke engine can easily be converted, in some ways it is better than the 2 stroke for conversion. There happens to be a discussion about IC engine conversion to steam going on at another forum: (CSEE) CLASSIC STEAM ENGINE ENGINEERING FORUM: http://www.classicsteamengineering.com/ ... en#msg2533

The best engines to convert will be cast iron engines, or those at least having a cast iron cylinder liner. Your 6 HP IC engine would probably make a reasonable conversion to a launch engine.

I don't think counterbalancing will be necessary at several hundred RPM, at least the engines I have made with stacked pistons didn't need it. The bearing loads are far greater from pressure on the piston than imbalance loads (at several hundred RPM), so bearing wear will not be a function of weather the engine is balanced or not.

Of course you can turn IC engines into steamers without the stacked pistons, retaining the original piston as the steam piston. There re-balancing would serve no purpose. When you pick out the actual machine you will convert, be it an air compressor, AC compressor, or IC engine, we can supply some design details for your specific machine.


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 Post subject: Re: Pump to convert to a Steam engine?
PostPosted: Thu Nov 24, 2011 11:09 pm 
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Full Steam Ahead
Full Steam Ahead
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Joined: Wed Nov 18, 2009 6:08 am
Posts: 439
Location: Menlo Park, CA
Boat Name: Otter
I finally retired the Otter's engine a few years ago after 20 years of steaming; the main bearings and seals were worn to the point of leaking and knocking. Considering the compressor cost about $15 at a scrap yard in the 80s, I felt I certainly got my money's worth :). Some things I learned along the years:

* Buy some good cast iron & bronze (or cast iron again) for the slide valve; this gets some serious abuse in marine engines - especially when throttling down after a hard run - the superheat from the throttling makes things squeak.
* Avoid superheat with slide valves. My first boiler (a Len Williams special) had quite a bit of superheater surface area, and I ended up resurfacing the slide valve every other year or so.
* If you use the existing piston(s), run mostly water w/ a couple of table spoons of thick heavy oil (600W steam oil) in the crankcase. If you're condensing, I hear Mobile 1 140W gear oil works well and is much easier to remove from the hotwell.
* Use a feed water heater in the exhaust - there's a lot of waste energy there on a small single.

The Otter now has a engine from 1895 or so; I had to make a new spool valve, valve rod, piston, piston rod and misc. valve gear parts. It's about 40% larger displacement and with the switch from 13x17 to 16x20 prop, the Otter is quite lively.

- Bart

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Bart Smaalders http://smaalders.net/barts Menlo Park, CA


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 Post subject: Re: Pump to convert to a Steam engine?
PostPosted: Fri Nov 25, 2011 3:31 am 
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Warming the Engine
Warming the Engine

Joined: Mon Jan 11, 2010 4:07 am
Posts: 66
Bart,

I gotta know, How did you deal with the fact that your slide valve operated at the same angle as the orientation of your drive shaft? Unfortunately, the pictures on your website really don't tell the tale (BTW, you REALLY gotta update that thing brother.) The one really good shot of your slide valve assembly shows it broken. So it's tough to tell how you got it to work.

Incidentally, there is another pump available over at harbor freight that would work. This one. Would make a nice V-twin. I'd have to work out two steam chests, but each one would have much larger tolerances as it would only have to service one piston, not two. Looks to be a good 75% larger displacement too. so more HP. Again, all cast iron construction.

Of course, using my old lawn mower engine is still the cheapest alternative. Gonna have to bring that bad boy in before it snows and start ripping it apart.


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 Post subject: Re: Pump to convert to a Steam engine?
PostPosted: Fri Nov 25, 2011 6:05 am 
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Full Steam Ahead
Full Steam Ahead
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Joined: Wed Nov 18, 2009 6:08 am
Posts: 439
Location: Menlo Park, CA
Boat Name: Otter
Wearyman wrote:
Bart,

I gotta know, How did you deal with the fact that your slide valve operated at the same angle as the orientation of your drive shaft? Unfortunately, the pictures on your website really don't tell the tale (BTW, you REALLY gotta update that thing brother.) The one really good shot of your slide valve assembly shows it broken. So it's tough to tell how you got it to work.


I used a rocker arm ;-). We found a piece of it in a photo (most of the older photos aren't digitized; by the time we had the digital camera the steam engine had been running for 10 years.... so didn't show up in lots of pictures), attached.

If you do a rocker arm, mount it on needle bearings for minimal fuss.

- Bart


Attachments:
OtterEngineDSC_0366.jpg
OtterEngineDSC_0366.jpg [ 201.73 KiB | Viewed 1761 times ]

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Bart Smaalders http://smaalders.net/barts Menlo Park, CA
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