Optimum operating speed?

[Duncan.e]

Gentlemen,

I need some more advice....

I have a design more or less finished for a two cylinder double acting oscillating engine that ultimately I want to use to drive a 7/8" / 1' scale 'coffee pot' locomotive.

My question is, what sort of rpm is optimum for these engines? I don't know whether I need to include some reduction gearing in the engine. I reckon on running the axles at no more than 1500rpm.

I'm hoping the engine will run happily at no more than 30psi and have plenty of pulling power, which suggests running the engine faster and adding reduction gearing to increase torque....

Your advice will be appreciated!

Duncan

 

[Maryak]

Duncan,

Without knowing the size of the drive wheels on the track and the scale speed you wish to achieve. IMHO it's a bit difficult to say.

Best Regards
Bob

 

[Blogwitch]

You will find that steam engines only run at that sort of speed on the bench with no loading.

Normally, say in a model boat 200 to 300 RPM is plenty fast enough for a steam engine. With say a 2 to 1 piston diameter/throw long stroke, you will not get even that sort of speed under load and will be a lot more efficient in both steam usage and pressure.

You only have to look at full steam locos, they are most probably running somewhere between 60 and 100 strokes per minute.

Steam engines give out a lot of torque at low RPM's.

Go to this site and click on the engine in the bottom left corner, it will allow you to download the pdf plan file. Long stroke, and will run perfectly on 25 to 30 psi of steam. It is a very powerful motor for it's size. It can easily be modified to make it easier to make.

http://jpduval.free.fr/Plans_moteurs_vapeur_p1.htm


John