How Slow Can You Go

[Jones]

When I have it running next I will try to get a video of the wobbler I made. It would have to be one of the slowest running 'single acting wobbler' engines out there. It has ball races on the crank and big end.

 

[fdew]

I don't know if this will work on an engine or not, but on pneumatics, when you want to go slow you put a needle valve on the exhaust, not on the input. It might be worth a try.

Don't do this with steam. Just air.

Frank

 

[rake60]

Now THAT is some impressive lack of speed Phil! :bow: :bow: :bow:

Rick

 

[chuck foster]

i have seen allot of slow running engines but phil that has to be the slowest 8)

chuck

 

[Philjoe5]

Funny, that's exactly what many of my former teachers said about me. Little did they know that some folks find that a noble goal :big:

Cheers,
Phil

 

[steamboatmodel]

I don't know if this will work on an engine or not, but on pneumatics, when you want to go slow you put a needle valve on the exhaust, not on the input. It might be worth a try.

Don't do this with steam. Just air.

Frank

I remember when taking a pneumatics course the instructor telling us " When in doubt meter out". if you have the needle valve on the exhaust you are creating a back pressure which will work with some valves (piston), but may cause problems with slide valves.
Regards,
Gerald

 

[old_bones]

Hi All,

This is my entry for the "How Slow Can You Go" challenge. It's a horizontal mill engine with 1.0" bore and 2.0" stroke.

[ame]http://www.youtube.com/watch?v=1FguWF5nef0[/ame]

I don't think it wins the prize but my grandchildren love to watch it go.

 

[chuck foster]

i think you have won just by having your grandchildren intersted in the engine 8)

chuck

 

[potman]

I've noticed that some of these engines appear to slow down when the crankpin is moving up and almost stall just as it reaches it's highest point. I assume this is because energy to lift the connecting rod against gravity is being sucked from the engine. If one were to add a counterweight on the flywheel just opposite the crank would the engine be able to run slower?

Anybody want to try it and report back?

earl...

 

[Philjoe5]

Being a fan of the slo-mo engine at some point I'll try a needle valve restrictor on the exhaust and the flywheel counterweight. Both sound feasible and easy enough to try. Just don't know when I'll get to it. ???

Cheers,
Phil

 

[Noitoen]

I've noticed that some of these engines appear to slow down when the crankpin is moving up and almost stall just as it reaches it's highest point. I assume this is because energy to lift the connecting rod against gravity is being sucked from the engine. If one were to add a counterweight on the flywheel just opposite the crank would the engine be able to run slower?

Anybody want to try it and report back?

earl...

My understanding of the thing is that the area of the piston is different because of the connecting rod. Since the pressure is constant, the low pressure has grater difficulty to move the piston "up" than "down. :

 

[rake60]

This is a great thread!

Models that are running this slow are actually producing output power.
It might not get you from 0 to 60 in 5 seconds, but it is just as impressive
for the scale.

It's a model powering a flywheel rather than a flywheel keeping a model
running. Does that make any sense at all? scratch.gif

Beautiful Works Everyone! :bow:

Rick

 

[dparker]

Hello All: This intrigues me I suppose when things are running fast they don't seem to last (Hopped up motors). I enjoy seeing something running slow and lasting forever or at least being reliable.
My examples seem to gather more interest when running slow than running at higher speeds.
McCabes Runner:
[ame]http://www.youtube.com/watch?v=_0OlpkLcddM[/ame]
The Stuart 10V will run very slow if desired (sorry not what we were trying for when these pictures were made) but It may give you somewhat of a idea about the model.
[youtube=425,350]gxPKYE4ZVqg[/youtube]
These engines sit on the shelf most of the time because I know of only two brothers in the neighborhood who are even interested in this kind of toys. It is amazing that the wife can find the remanents of home machine shops at estate sales around the area. I wish we were not so paranoid to let people know our interests but then you open yourself to exposure to the bad element and it is safer to keep your mouth shut I guess.
--don

 

[Philjoe5]

Hey Don,
Neat engines....you've got that McCabes Runner to go pretty slow :bow: I like the Stuart too and hope to build one someday

Cheers,
Phil

 

[Philjoe5]

I have a video of my latest engine running at about 30 rpm. I can't get it to run slower without stalling but it only has an hour of break-in time on it. I had thought that this design would allow for slower operating speeds based upon some of the discussion here and elsewhere. Here you go:

[ame]http://www.youtube.com/watch?v=F2c9oPjSbW0[/ame]

I think, for now, I've reached a personal goal and will now move on ;D

Cheers,
Phil

 

[zeeprogrammer]

That is so cool.
I like slow.

 

[Cheshire Steve]

Its a shame if a model with an interesting linkage can't be run slow enough to see it. I am currently building a true-to-scale beam engine so people could watch the Watts linkage, and it occurred to me that this one will have to run slow if people are going to appreciate the motion.

Apart from the obvious issues of balancing and reducing friction, there is a fundamental role of scale - they say you can't scale nature - and in some ways this is true. Some things scale with volume (like weight), so at 1/10th scale you have 1/1000th of the weight. Other things scale with area, like force on a piston or area of bearings, and as for flywheels, well they don't scale well at all.

So getting a scale model to run slowly is a real challenge, with best chance being for engines that are multi-cylinder, large scale, and those that had big flywheels to give excellent speed stability (such as those used to generate electricity). You may not get the speed stability, but at least they should run fairly slow.

Has anyone any thoughts on whether the type of piston rings (or no rings) is important in getting slow running ? I am guessing having no rings, but a couple of oil grooves, is lowest friction as this seems the common type for hot air engines.

Steve

 

[Philjoe5]

Steve,
FWIW I'm using 3 oil grooves that are 0.003" deep.

Cheers,
Phil

 

[DavesWimshurst]

My Stuart beam engine has piston rings but no packing on the rods. It seems to have more friction than the similar bore Stuart 10V with graphited yarn packing. Here it is running at 44 rpm:



Dave

 

[Kermit]

Its a shame if a model with an interesting linkage can't be run slow enough to see it. I am currently building a true-to-scale beam engine so people could watch the Watts linkage, and it occurred to me that this one will have to run slow if people are going to appreciate the motion.

Perhaps the key to success with slow speed is to keep a decent amount of pressure, say something that gets you 70 RPM and then INCREASE friction thereby loading down the motor. You should be able to get much slower. try a piece of felt over the top of a rubber band. The more you stretch the rubber the more the friction increase.



Throwing ideas at the wall, hoping something helpful sticks,
Kermit