Welcome! Log In Create A New Profile Recent Messages

Advanced

Converted 4 stroke engine to uniflow steam

Posted by Arch-Tone 
Converted 4 stroke engine to uniflow steam
June 27, 2017 11:30PM
Hey guys,

Just posted a video on YouTube of my 17.5 HP Briggs and Stratton conversion to uniflow steam engine...yeah, yeah I know...ANOTHER lawn mower engine conversion on YouTube...but I would like to think it was done correctly. Let me know what you guys think...any advice, criticism, questions or praise are always welcome. I plan on reinstalling it back on the mower soon with the steam generator and hopefully have it ready for the fall SACA meet. I am using the original valves with a modified cam, but with the steam going into the old exhaust side (shorter path) and the old intake valve is used just to reduce compression on the up stroke. I drilled exhaust holes at the bottom of the stroke to make it uniflow. The exhaust empties into the crank case and keeps the bearings lubricated thanks to the inline displacement type oiler....not sure if it is sufficient, but it keeps a nice coating of oil on the moving parts....similar to how a 2 stroke IC engine lubricates....replaced the original valve spring with a stronger one to keep the valve from lifting from the 800+ PSI steam pressure...It runs like a champ on the work bench but have yet to try it with a load...here is the link:

[youtu.be]

Will post new videos/pics of the build as it develops further...again...any advice you guys can give would be much appreciated
Re: Converted 4 stroke engine to uniflow steam
June 28, 2017 12:28PM
Sweet sounds, good luck with it!
Re: Converted 4 stroke engine to uniflow steam
June 28, 2017 03:43PM
Good job. My respect. Practical result is ever better then pure theories. But i would inverted valves on a steam engine order. Otherwise You loose automatic operating of relieve to do which You now need to operate the valve with a cam in a constant timing, so compression became difficalt to control in a proper order. And besides compression doesnt work to help open intake valve. Yes, You have the steam pressure to help it but then need to have big effort to close it. Would You say (and show) about the boiler? Controls? It is very interesting.
Serge
Re: Converted 4 stroke engine to uniflow steam
June 28, 2017 07:20PM
Thank you for your response, sidrug and Serge. I understand that inverted poppet valves are the ideal valves to use on a steam engine. I am using the original valves out of convenience and may eventually go with a proper poppet or a bash valve design. I am currently redesigning my steam generator....I have this idea for what I call a "Turbo LaMont" and will be experimenting with that soon. It's small and involves no external motors but yet is still forced circulation....more on this to come as it develops. For now, the monotube you see in the video provides ample steam for my needs.

Jamison
Re: Converted 4 stroke engine to uniflow steam
June 29, 2017 10:00AM
Jamison,

sure Turbo-LaMont is very interesting thing, i would not dare to ask about it before it has been tried out. But this monotube You already have in hands is a beauteful thing at my opinion. Could You tell more about it?
Everything is of interest. Length and size of tube, number of coils and windings in the coil, steam generating capasity? Would be nice to look at some pictures.

Serge
Re: Converted 4 stroke engine to uniflow steam
June 29, 2017 12:38PM
You can get a good view of my boiler in action from the video....right at the 4:38 mark. It currently has 50' of 3/8" 316 stainless tubing (closest to the fire), 100' of 3/16" copper tubing in the back...this section used to be 50' 1/4" stainless but I'm experimenting with smaller/longer tubing there....and 100' of 1/4" copper wrapped around the boiler shell to preheat the feed water. The 100' of 3/16 tubing flashes water to steam almost instantly, but i really have to watch the heat there because of the soft copper. If I decide to keep that tubing size, I will replace it with NiCo or stainless. At the output side of the 3/8" tubing I have a small external steam drum. From there it goes into 6' of 1/2" 316 stainless back into the boiler as a superheater, coiled mid furnace then another 6' of 1/2" as a steam line to the engine. I have a high quality pressure relief valve installed on the drum for safety and the throttle valve is between the drum and the superheater. The torch is a store bought propane "weed burner" mounted at the front. I have no idea what the steam generating capacity is....I'm not an engineer...maybe someone out there can make the calculations....but I know it is sufficient to run a 3 1/2" bore, 3" stroke engine with no problem, as the video demonstrates.

Jamison
Re: Converted 4 stroke engine to uniflow steam
June 29, 2017 02:48PM
Thank You, Jamison. To know steam rate of the generator no need to be an engineer, just to look how much water "ate" the pump (which turned to steam) per some period of time. This number and knowing HP of the engine would give You evaluation of the system efficiency.
Serge
Re: Converted 4 stroke engine to uniflow steam
June 29, 2017 05:27PM
I was very impressed on the video. Can you show more of your burner, fuel etc.
Re: Converted 4 stroke engine to uniflow steam
June 30, 2017 09:48AM
Thanks, Jeremy...the burner is just a propane powered torch...marketed as a "weed burner"...that can be purchased at most home improvement stores for about 50 bucks. It advertises having a 500,000 BTU output and over 3,000 deg temperature flame and sounds like a rocket engine when ignited. It comes with a handy inline gas valve, 10' gas hose and 20lb tank connection. I simply mounted the torch at the entrance of the steam generator. Some models even come with a piezo igniter built in as well. The flame is directed into a column by the cylinder around the torch nozzle....my boiler shape is actually designed around the flame path of this thing. That's why it's relatively narrow at 8" and tapered in the front at 6". I have an air gap between the torch and the boiler entrance that creates a nice venturi to draw in air. The whole boiler is about 34" long, the shell is made out of two small stainless steel trash containers connected together and have held up well, even after 2 years of use (and abuse). You can see the boiler at the 4:38 mark in the video...it is now disassembled as I am rebuilding it as a forced circulation, "Turbo LaMont" idea I have been working on....more on this as it develops.

Jamison
Re: Converted 4 stroke engine to uniflow steam
June 30, 2017 10:17AM
Very impressive. I didn't see a water pump. What did you use? Do you have any way to control the heat or water flow to the boiler? Do you have problems with flooding the boiler? You mentioned overheating the copper section. How do you prevent that?

Lohring Miller
Re: Converted 4 stroke engine to uniflow steam
June 30, 2017 11:20AM
The water pump is a 120vac electric 1600 PSI pressure washer I plumbed into the feed line, bought at Harbor Frieght Tools for $80. It does a good job forcing water through the small 3/16 tubing but the fact it uses a120vac motor makes it obviously impractical for mobile use (unless I use a really long extension cord...lol). I have experimented with driving just the pump with an 18vdc electric grinder (with its built in gearing) that will spin just fast enough with 12vdc to run the pump....but the lower voltage and increased load was overheating it.....another solution is to power the original motor with 4-6 12v batteries in series....it is a brushed motor so it would work, but again the extra weight of the batteries needed for the 20 amp motor makes that undesirable as well....anyways....the pump and flame were both manually controlled, but I do have a water level sensor on the base of the steam drum so I don't get water in the engine. I keep a constant eye on my tubing for overheating and adjust the flame appropriately. The pumping restrictions from the 100' of 3/16 tubing seem to help keep the boiler getting flooded....I can get plenty of consistent, dry, high pressure steam just by running the pump about every 15 seconds for a duration of about 3 seconds...with the fire at full blast....while watching the gauges and tubing very closely. There is a hole in the boiler shell that allows me to see the front of the 3/16 copper section (about mid way). When the front 3/8 stainless section starts to glow a little....I turn down the heat. When the front of the 3/16 section starts to glow a little....I turn on the pump. This works very well and consistent and I suppose could be controlled with some temperature sensors at both sides or a Wetz expansion/contraction type controller....but considering I am now going with a LaMont, all I need is a water level control and a pressure switch to control the fire...which really simplifies things.

Jamison
Re: Converted 4 stroke engine to uniflow steam
June 30, 2017 11:41AM
Forgot to mention.....I have a double acting piston pump...that I originally built as a LaMont circulating pump....that will be the new feed pump for the "Turbo LaMont"....it has a 1" solid Teflon piston that works great without lubrication, but Teflon's 450 degree breakdown temp and 600 deg melting temp was a concern for hot water circulation. It is driven by an electric motor belted to a small gearbox and linked to the pump shaft with a Scottish yoke...you can catch a glimpse of it in the video...it is laying on the floor between the steam generator and the engine. I haven't measured it's pressure output or flow rate yet....but I believe it will do the job.

Jamison
Re: Converted 4 stroke engine to uniflow steam
June 30, 2017 03:43PM
I may have missed this, can you tell us about throttling of the engine. I am also very impressed with your use of the Lucas oil stabilizer, I invested a small fortune in steam cyl oil I have 460 and 680 (not sure about the weights) but im definitely go with using the lucas as percentage. Boy its really amazing to see all the water exiting the crankcase until you have the engine warmed up.


One other question are you admitting the oil with your steam feed.

I have an engine with no crankcase so I admit my oil a drop at a time to the piston cyl about mid stroke thru a bore.

For my mains (crank bearing) I use a grease fitting (cup) and that lubricates the main journal.



Edited 3 time(s). Last edit at 06/30/2017 04:10PM by Jeremy Holmes.
Re: Converted 4 stroke engine to uniflow steam
June 30, 2017 08:13PM
The throttling is controlled by a 1/2" stainless steel ball valve that is rated at 2000 PSI...it is also fire safe and blow out proof. Believe it or not, they only cost $36.50! I wouldn't run superheated steam through it.... I have mine installed between the steam drum and the superheater (like the White steam cars) and it has been working great for about a year now. I also have a globe valve that is rated at 5,000 PSI and 1000 deg....it cost $110 and has graphite seals, but it takes several turns to open and close it...not so good for throttling so I use it to drop pressure going to the steam whistle. I bought both from Zoro. As far as the oil goes...I was looking online for some real steam oil...hard to find nowadays...then I came across a website that talked in depth about steam oil properties and the modern equivalents. Here is the link:

[www.southernsteamtrains.com]

They didn't mention Lucas oil stabilizer, but it did educate me on what to look for....I then did an internet search for those properties and found that the Lucas was a great match! A trip to the auto parts store and few bucks got me some pseudo-steam oil. It doesn't have the organic tallows but everything else seems on target, unless I'm missing something. Here is the Lucas tech data:

[lucasoil.com]

I have a simple displacement type oiler installed just before the engine to insert it into the steam flow. You can see it in the video, it's the length of pipe with valves at both ends attached to some 1/4" tubing.

Jamison
Sorry, only registered users may post in this forum.

Click here to login