How Slow Can You Go

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bretk

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Ok, Based on the recent posting, here are vids of my slow runners. One, an old wobbler with a history unknown to me, was an ebay basket case find that needed alot of TLC but it sure runs nice now, and very slow for a wobbler. The second was a half completed casting kit that I finished some years ago with the help of a knowledgable steam sage of yesteryear. I'm sure he forgot more about steam engines than I will ever know.

Enjoy -Bret



 

Powder keg

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Those are great!!! Dosen't get much slower than that. The first one is neat! I like how the con rod goes all the way through.

Wes
 

CrewCab

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Bret, they are both nice engine's but, I particularly like the second one 8) ......... don't s'pose you have any plans ???

Thanks for the video's, dam fine work 8)

CC
 

bretk

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CC,

No plans, That was part of the fun ::) we just used the castings we had, and fabricated what we didn't, I have seen similar engines on ebay, but they haven't had the tunnel crosshead guide casting like this one does. I seem to recall someone saying the castings may have come from power models, but scince his place blew up I can't say for sure.

-Bret
 

Paula

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Hi Bret,

I know this is an old thread, but I couldn't help but notice how similar your second engine is to one that I built from a casting kit sixteen years ago. It's not *exactly* the same, but they seem too much alike for it to be merely coincidence. Here is a picture of mine (Note: the base originally had mounting lugs like yours, but I removed them and bolted them from beneath the wood platform):



I purchased the casting set for this engine from "D & M Model Engineering" in late 1990, and have seen very few examples since then. Here is a scan of the 1986 D & M catalog page:



Unfortunately, my engine will not run as slowly as yours! There is no binding in any of the linkage, but it has two cast iron rings on the piston which still impart a significant drag on the cylinder wall. I've tried adjusting the valve for slower running, with negligible results.

Thanks for posting the videos, Bret! If anyone's interested, I could take a video of my engine running, and post it here for comparison.

Cheers,
Paula
 

steamer

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I still have the "who got Sabino to run the slowest" title

She's 7 x 14 x 12... 75 HP compound in the steamboat Sabino at Mystic Seaport.

The record.... 13 rpm. She was turning so slow the tide was pushing the boat backwards ;D

Set the condensor vacuum to 18 in Hg, open the LP drain valves, set her to full link, and keep your pressure up(110 plus)

Dave
 

dparker

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Paula: Very nice looking engine there, and WELCOME to the forum. It certainly looks like quite a few hours went into that engine and the paint job is superb! Truly a masterpiece!
Thank you for showing it to us, if you have more please let us see pictures or videos.
don
 

Paula

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Thank you for the kind words!

Here is a back view of the engine. I equipped it with a displacement lubricator, just for appearance sake -- it's never been run on steam (ditto the cylinder drain cocks):



The handwheel on the steam valve is custom-made. The original knurled plastic one just didn't look very good to me (though it probably would have saved some burnt fingers if I was using steam).

I will make a video of it running as soon as I can -- my compressor is down for repairs right now.

Thanks again for the compliments.

Paula

(PS - Sorry Bret... I didn't mean to hijack your thread!
)
 

Paula

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Hi again!

Well, I finally got my compressor up and running, so I took a short video of my D & M #11 engine in action. It's running on around 5-7 PSI, with the throttle set to run just fast enough to give a smooth motion. (It will run slower, but in a rather herky-jerky fashion):



Much faster than Bret's engine, I'll grant you. No doubt the main reason is the two 1/16" wide cast iron piston rings, comprising fully one-half the length of the piston. I made it per the drawings, but knowing what I know now, I probably would have used an oil-grooved (ringless) piston, like the one specified for my Stuart 10V. Particularly since this is not a "working" engine, but an occasionally-run "shelf queen". Still, I'm very pleased with how it runs. At higher speed and pressure, it puts out very respectable torque. I only wish that I had known (or cared) how to balance an engine when I built this one.

All comments welcome :)

Paula
 

Maryak

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Paula and bretk,

That is three very nice engines


Paula, whats wrong with the balance?


Best Regards
Bob
 

Paula

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Thanks, Bob!

...whats wrong with the balance?
At higher speeds, the engine wants to jump around bit. There is a cast-in counterweight feature in the crank disk, but it doesn't seem sufficient to accurately balance the rotating and reciprocating weights. It was only after completing this engine that I learned how to balance an engine properly (I.E. -- I read an article ;)) However, since the goal with these engines seems to be to run as slowly as possible, high-speed balancing seems a non-issue. :D

Cheers,
Paula



 

Maryak

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Paula,

Thanks for that. The reason for my question was my concern re balancing my small 1 pot IC engine.

To give it a somewhat rudimentary check I ran it flat out using a drill. I was pleased with the lack of jumping around but the drill is at best 1/4 - 1/2 the operating speed.

It looks like a suck it and see exercise.

Best Regards
Bob
 

cfellows

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I have a hit n miss engine that is 1" bore and 1.5" stroke. I balanced it by placing 1/2" neodymium magnets on each of the flywheels, opposite the connecting rod journal, on the inside step of the outer rim. I kept adding magnets side by side until the engine would run with no noticable vibration. Someday, I'll weigh the magnets and make steel plates to attach to each flywheel. For now, the magnets work fine and show no tendency to fly off. I can provide a picture if anyone is interested in seeing it.

Chuck
 

Paula

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Chuck, that's a neat idea!

The method I've used is based on an old article in "Strictly I.C." magazine, by Richard Condon. Basically it states that, for the lowest bearing load and minimum vibration, you want to counterbalance all of the rotating weight + 1/2 of the reciprocating weight (you need an accurate scale for this):

1) Weigh the big end of the connecting rod (place the crank-end on the scale, whilst the piston-end rests on a fixed surface)

2) Weigh the crank bearing (if there is one)

3) Add the above two weights to equal the Total Rotating Weight (TRW)

4) Weigh the piston, pin, and ring(s) to equal Reciprocating Weight (RWT)

5) Weigh the connecting rod (without bearing) to equal Weight of Connecting Rod (WCR)

6) Receprocating Weight (WR) = WCR + RWT - TRW

7) Balance Weight (P) = .5(WR) + TRW

With the crankshaft (or crankshaft-flywheel assembly) resting on knife edges, hang a weight equal to P from the crank pin. The crank assembly should balance the weight. If not, apply weights, drill holes, etc. to achieve balance. That's it.

On my Odds'n Ends engine, I elected to do three things to balance the crank:

1) Made bolt-on counterweights for the crank:



2) Drilled out the crank pin, and

3) Chamfered the crank throws:



There is definitely some trial-and-error involved in getting the crank to balance the P weight. If you know Statics, and calculating density of materials, you should be able to save some time here.

It worked like a charm for me -- on several engines.

Paula
 

loggerhogger

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Nothing better than the quiet magesty of a slow running engine. it almost makes me cringe when I see people 'tacking up" their model steam engines until all you can see is a blur of rods and wheels. they look so much better running slow.
 

Philjoe5

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I'm with you loggerhogger on that. I've been able to build a steam (air operated) engine that will rotate at 60 rpm. That's the best I can do to this point. I hope when I put more hours on some of them I'll be able to get them running slower.

Cheers,
Phil
 

Philjoe5

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Again I'm resurrecting an old thread, but when I first read it I kept it in the back of my (convoluted?) mind. One of my aims in building an engine is always to see how slow I can run it.

During the recent Cabin Fever Expo I picked up some needle valve air flow controllers. These valves allow really fine air control. I set up two of my engines that had some break-in time on them. From my compressor I have ¼” air hose going to a 1/8” NPT line that connects to the flow control. Out of the flow controller I have 3/32” OD polyethylene tubing of 0.105” ID going to the intake of the engines.

The engine shown here has a 1.5” bore x 2.1” stroke and is double acting. The flywheel is 6” diameter. I’m able to run it at about 50 rpm.

[ame]http://www.youtube.com/watch?v=vrxSkJBz7HI[/ame]

The engine shown here has a 1.25” bore x 1.8” stroke and is also double acting. The flywheel is 6” diameter. I’m able to run it at just shy of 50 rpm.

[ame]http://www.youtube.com/watch?v=zSucuwlOTBU[/ame]

I think this will be the best I can do with this design but I am still wondering….what’s the lower limit. Has anyone constructed a model engine (air or steam powered) and run it at 10 rpm or less? ??? I feel like Monty Python and the Holy Grail here. :big:

Cheers,
Phil



 
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