Geared flywheel and super slow engine pondering.

[hitnmiss]

I like steam engines running super slow, lets you view the works.

I the sound and looks of a open horizontal hit and miss engine.. Mine runs slow but still the conrod and piston are moving pretty quick.

Imagine a slow running big flywheel'd horizontal engine running at say 200rpm, now imagine the same engine with a 10:1 gearbox running the flywheel at the same 200 rpm but the crank and piston running at 20rpm. I think the sound of the powerstroke running up the flywheel and then the long coastdown as exhaust, intake and compression occur and repeat would be a treat, not to mention the slow movement would make a very cool display.

I would guess a long stroke would be in order, maybe twice the current norm. Also maybe a o-ring to really seal the slow piston?

My question is how slow could a engine like this run do you think? Would this idea even work? From my calcs, 20 rpm would be a power stroke every 6 seconds.. Imagine the sound... 1.5 seconds for the exhaust stroke.

Wouldn't mind building one but is there even a chance it would run?

 

[Cedge]

I'd have some pretty large doubts about it running. Flywheel momentum is basically what carries the rotation past the dead spots in the engine's cycle. A gear reduction system would add significant resistance which would probably nullify the usefulness of the flywheel action. Just an educated opinion, based on years of steam engines... with zero math to back it up.

Steve

 

[snowman]

I've done similar things without engines attached, wish I had taken pictures of those projects. Get rid of the gearbox and just use a pulley with big O-ring, there is no timing involved, so it's not necessary to have the synchronization of a gear box, let alone the frictional losses. You will need to do a very small reduced diameter on the flywheel, and likely a large cylinder diameter to provide enough power.

 

[Philjoe5]

Hi HnM:
I am also a big fan of slow engines. My latest build, a horizontal mill engine (1" bore x 1.25" stroke) with a 4" flywheel can run as low as 60 rpm. I don't have 2 hours of run time on it yet so when she's broken in who knows ??? At that speed you can see the impulse of the compressed air as the flywheel momentarily speeds up just beyond TDC. ;D

Cheers,
Phil

 

[AllThumbs]

I think it would work fine. You need a large flywheel though to carry it through the exhaust stroke.

E

 

[Bogstandard]

Do it like the Victorians did in their engine houses. Very long stroke maybe up to 4 or 5 to1 bore/stroke or even longer, with a massive flywheel to store the energy.
You could almost count the spokes when running at full speed.

John

 

[hitnmiss]

Phil,

What is the compression ratio? Hit and miss?

Hi HnM:
I am also a big fan of slow engines. My latest build, a horizontal mill engine (1" bore x 1.25" stroke) with a 4" flywheel can run as low as 60 rpm. I don't have 2 hours of run time on it yet so when she's broken in who knows ??? At that speed you can see the impulse of the compressed air as the flywheel momentarily speeds up just beyond TDC. ;D

Cheers,
Phil

 

[Philjoe5]

Hi HnM,

Sorry, I forgot to mention it's a steam (compressed air) engine; when I have it running slowly you can hear the air pushing through the ports, somewhat like when you pull a stopper or cork out of a bottle. ;D

Cheers,
Phil

 

[Bogstandard]

This slow

[ame]http://www.youtube.com/watch?v=LkaY_SdzW04[/ame]

 

[Paolo]

Nice video John...one tear went down....
Paolo

 

[snowman]

That's actually pretty fast. There is one in grand rapids at the Van Andel museum that they usually run slower. It's got an 18 foot flywheel.

 

[Philjoe5]

Where is that cool engine located? I have a 10x22 lathe and lots of determination. Can I build one :big:

Cheers,
Phil

 

[Bogstandard]

phil,

this is the prince consort engine fitted into the crossness pumping station.

a lot of these engines had their own names, usually named after members of the victorian royal family or if installed in mills, the owners family members.

if you do a search for crossness pumping station in utube there are a few more clips of the engine. but there are a lot better ones than this one.

john

 

[ianjkirby]

Hi Guys,
I see no-one has posted it, so I will pass on a secret, known to very few.
First a few caveats; small engines will never run as slow as larger engines, simply because of the lack of inertia, and the effects of friction. Double-acting engines will always work better than single-acting ones, and similarly, multi-cylinder engines work better than single-cylinder ones. Steam will work better than air, but that of course depends on it being available! And finally, the "timing" of admission and release of the steam or air will have a large influence on the performance. However, all other things being equal, the idea will work on any engine, but for the reasons above, results may vary a bit.
Now for the secret itself. Most engines have their throttle/regulator on the input side, and run with no sensible load. First up, they will frequently run slower if a suitable load is applied, and the exhaust may sometimes be more audible. The simple addition of something to drive will make any engine run "better". Secondly ( and this will work independently of the load ), a better effect is created by putting the throttle on the exhaust side, maintaining full steam or air pressure on the inlet at all times.
Ok, its not really a secret, but very few model engines I've seen are controlled in this way, and I'm not sure why this is so. Try it, you'll like it! ...and post your results/thoughts.
Regards, Ian Kirby.

 

[AllThumbs]

That will only work on double acting engines. It is true that it is possible to make a very slow engine this way.

E

 

[Philjoe5]

This is all quite interesting to me. I'd like to build a small model engine and get it to run at say 30 - 50 rpm. It looks like I should consider a double acting steam engine with a small load, like a model generator, attached. The throttle part isn't clear to me and I must admit I'm fairly new at this. But the model "steam" engines I've seen running on compressed air don't appear to have throttles other than the regulators attached to the air line. Their speed is regulated by the inlet pressure. Are you saying you could regulate the speed on the exhaust side with some sort of device that creates a backpressure? ??? That seems easy enough to do.

Cheers,
Phil

 

[Bogstandard]

Phil,

What I think is trying to be explained is the basics of pneumatics.

Where people fail with pneumatics (air fed engine) is that really you should feed full power to the piston power face, and regulate the speed by throttling the exhaust air on the other side of the piston, this is done with one way adjustable restrictors. So you can have different times for both strokes, say fast out, slow in or vice versa or both the same. It is used in industry where say a punch comes down very slowly, but having full power, then retracts at a much higher speed. The control valves are very cheap, about $10 each, but are rather bulky, but that can be overcome by routing the pipework to somehere they can not be seen.

Doing it this way you can control the speed down to finite amounts, where the piston is hardly moving at all, but still retaining full power. As mentioned before, this will only work on a double acting cylinder. But it is a lot easier to do the steam method of pressure control, even though less efficient.

I have never tried it with steam, but I wouldn't think the throttled exhaust scenario would work too well with steam in the slowed down situation, because steam depends on its expansion coupled with temperature to carry out its job. If you were to slow it down too much, with it's inherent properties, it just might not like it.

Air and steam have totally different characteristics, and as such, the control of the engine should be made relevant to what power source you are going to use.

But usually we all go with the easiest method.

John

 

[te_gui]

Not a pneumatics expert, but know a fair amount about hydraulics, still fluids. If you restrict the exhaust side of thing you will not maintain full power. Any back pressure will result in an opposing force to the input pressure.

Brian

 

[Bogstandard]

Hi Brian,

I take your point, and should have most probably worded it slightly different.

But what you must consider, pneumatics and hydraulics, even though very similar in looks and design, do operate in totally different ways. Mainly due to the supposed incompressability of a liquid and the compressability of a gas. Having worked in both these fields, especially pneumatics, I do understand them a little bit.
Differential areas also come into the equation if using a single ended cylinder, but I was trying to explain how to control an air/steam engine without confusing the issue with technical jargon.

John

 

[ianjkirby]

Hi again,
For the benefit of people without industrial experience in pneumatics or similar, the reason the piston moves slowly with an exhaust regulator is that the force moving the piston is only the result of the DIFFERENCE between the pressure on each side of the piston. For example, if the exhaust regulator was completely closed, there would be no movement at all after the pressure equalises. If the exhaust regulator is then opened just a little, SOME of the pressure on the exhaust side of the piston will bleed away, and the full pressure on the power side will begin to move the piston slowly. In a way, its like applying a load.
If the exhaust is fully open to atmosphere, this "difference" is difficult to control, as most supply valves are not regulating valves, and one is always operating with the valve only just cracked open.
There may still be a "dead spot" near the end of stroke, and this will require a flywheel or similar to carry it over this spot for continuous running. I did mention several caveats, remember! There should be no control problems getting a twin cylinder double acting engine to tick over very smoothly and very slowly. Any configuration less than this will be a bit harder to get consistent slow running.
If nothing else, just put your finger over the exhaust and open the supply valve fully, then "play" with the exhaust pipe. Of course, if its steam, use something a bit more sensible than your finger!!!!
Regards, Ian Kirby.