Steam engine cant start to run

[WearyParticipant @weary]

Hello Martin,

It reads to me that your engine is suffering hydraulic lock due to steam condensing in the piston.  Bear in mind that your cylinder will have to be above 100 degrees C for the engine to operate.

Looking at your picture you have a significant mass of metal (cylinder, and ‘stand’/backplate) to heat and a length of pipe linking boiler and engine also cooling the steam.  Given that your boiler is maintaining a pressure above the stall pressure: when the engine stalls, flick the flywheel over a few times to expel condensate, given the boiler pressure you noted, even though it falls sometimes perilously close to the stall-pressure, the engine should ‘pick-up’ again, even if only for one or two rotations.  So, repeat the ‘flicking-over.  And repeat again until the cylinder-block is heated through and allows the engine to run.

Your design appears to be at the limits for oscillating cylinder engines, so it is not too surprising that it is ‘temperamental’.  Most commercial engines of that type would have a far shorter cylinder-pivot point to big-end distance to increase cylinder swing & a significantly larger piston surface. In addition the cylinder is often mounted on-top of the boiler so that connecting pipework is minimised and heat is applied to the cylinder too, thus assisting warming-up and reducing condensation when running.  You will also note that commercial cylinders and ‘backplate’ tend to be of minimum mass possible.

If  your porting is now ‘sorted’ and given one of your comments above I also wonder if your engine is a little tight too as the stall-pressure you require seems  ‘high’.  Differential expansion when hot between your piston and cylinder can easily increase friction and I cannot see a method of easily introducing lubricant to the piston, or indeed any of the moving parts.  Your design has a large area of piston-wall to cylinder-wall ‘contact’; as ‘SillyOldDuffer’ pointed-out above this could usefully be reduced.   To give  you an idea, Jason will (probably) be ‘generating’ 0.1-0.15 bar (say around 1.5 lbs per sq in) in the video that he posted above.  Unlikely that you could match that stall-pressure given your small piston surface, but it does give you an idea of the kind of stall-pressures to aim for!

Phil

 

[Dark KnightParticipant @darkknight31337]

1. Temperature expansion shouldn’t be a problem, there is 0.05mm of space between piston and cylinder. I know that from my images it seems that big metal conrod is the same diameter as piston but it isn’t. Is a little bit smaller for 0.15mm and the only reason I made it that diameter is that I minimise wear on brass piston by increasing friction only on edge of cylinder by a minimum. It is screwed on conrod so I can change it when needed.

I did some tests with new conrods as suggested and made them lighter for approximately 4-5 times, and the stall pressure was completely the same.

I reduced stall pressure to 0.3bar by using Castrol grease as suggested on tables in literature ( new coefficient 0.11, old one 0.18), I also greased flywheels axis ball-bearings with graphite grease.

Im almost convinced that the problem is in boiler. I thank you all for helping me with engine especially Jason B.

My air setup:

On these 2 links are new tests with air:

Stall pressure:

https://files.fm/u/52mf4tunb7

Max RPM:

https://files.fm/u/e6wk6kjva9

Martin

 

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