Bates & Edmonds gas engine electric plant

[Steamchick]

that's a beautiful job.... I have a question, the answer to which might enhance your story - since you have a generator attached, if it's 1/8 scale it ought to be able to produce 17/8 = 2.125 KW, but of course power doesn't scale linearly - can you increase the load on the generator and (since you have a volt meter and an amp meter) tell how much power your engine puts out?

Hi Bill, Jeff,
As a "werrit" (someone who worries about things even for no reason, and who sticks his nose in where not appropriate...) I spotted your remark about non-linearity of models: Of course, when it comes to things like polar moment of inertia (4th power) Stiffness of beams (3rd power) volumetric considerations (engine displacement etc. Cube = 3rd power) Areas (area of piston = force developed on con-rod) etc. I understand all these matters, but for a generator I would have simply guessed at a volumetric (cube, 3rd power) relationship with scale? I.E. for the "same" flux density as the full sized generator, and speed of change (dB/dt = rate of change of flux: or N=>S =>N at the same rpm as full sized) then the "Power" developed in a generator could be purely a volumetric ratio, of the "volume of flux" involved? - or "Volume of copper wire" involved? I haven't thought too deeply about this, but maybe you have the answer and explanation? Hence 1/8th scale generator = 1/512th of the power? => 17kW => 33w?
Thanks,
K2

 

[Steamchick]

Jeff, On another matter:
You mention the difficulties of setting the engine?
Are you referring to the curious arrangement of the "cam-levers" that operate the valves?
As per gen-set 11.jpg photo.
It looks to me like the "levers" are all wrong in the layout, but I am sure it is a true reflection of the full sized engine. Am I right in understanding that the "push-rod driven levers" acting on the levers on the valve tops act as cams? It feels wrong to me that these "cams" would have been acting in the middle of long levers, as the valve to levers are then having to resist bending ...?
An odd arrangement I should have avoided by arranging for the
cam=action to be in the line of the valve motion...? Or maybe I have mis-understood the mode of operation? - It is a curious arrangement of levers - to me at least.
Can you explain this at all? Having made it work, I hope you know what is really going on here?
Thanks,
Ken

 

[Rustkolector]

Jeff, On another matter:
You mention the difficulties of setting the engine?
Are you referring to the curious arrangement of the "cam-levers" that operate the valves?
As per gen-set 11.jpg photo.
It looks to me like the "levers" are all wrong in the layout, but I am sure it is a true reflection of the full sized engine. Am I right in understanding that the "push-rod driven levers" acting on the levers on the valve tops act as cams? It feels wrong to me that these "cams" would have been acting in the middle of long levers, as the valve to levers are then having to resist bending ...?
An odd arrangement I should have avoided by arranging for the
cam=action to be in the line of the valve motion...? Or maybe I have mis-understood the mode of operation? - It is a curious arrangement of levers - to me at least.
Can you explain this at all? Having made it work, I hope you know what is really going on here?
Thanks,
Ken

Ken,
The long rods do not work on the push stroke. They work on the pull stroke. You first adjust the angle of the top valve lever nominally by guess until till you get a near 90 degree angle between the pull rod and the top lever to maximize mechanical advantage against the valve spring torque. At the same time you will be setting valve opening distance. The inherant over travel of the cam levers adds to the confustion. Since the rods have two slight bends each in them you cannot adjust their length by a few degrees of rotation. The minimum stroke change can only be adjusted by a full 360 degree turn of the rods or a half turn at the top lever rod end. So you adjust the rod pull stroke duration nominally and then go to the eccentrics to get fine tuning of the duration. The real engines had a fine adjustable eccentric drive gear of some sort inside the crankcase. Adjustment was accessed through the front inspection cover. Not doable on the model. So you compromise until you get the engine to run well enough. It gets a little confusing at times but once you have it you better have taken good notes.

Jeff

 

[Steamchick]

Thanks Jeff, I think I follow the settings now. I was aware of the idea of eccentrics operating valves with 3/4 of their use flapping in the breeze.... so there are no Tappet clearances to set. And that the eccentrics need to be timed for opening and closing times, which can't be adjusted except by rotating the eccentric on the shaft.
Seems like a pre-camshaft arrangement for operating poet valves?
But a lovely model when running!
Cheers!
K2

 

[xander janssen]

Nice model and generator!!!

Given that you have propane as fuel, how do you lubricate the piston/cylinder?

For my 2VD5 I was first thinking of running it on petrol with a few % oil for lubrication. However, propane might be nicer as that allows to place the carburetor further away (out of sight) from the cylinder.

In that case, I can make faux (imitation) intake filters and use the crank case venting tubes (that end up in the intake manifold as real intake, feeding a mixture of propane/air that has been mixed by a carburetor in the base/stand of the model. This might even work with petrol/air mixture, but I assume that droplet formation (poor evaporation) in the long supply line might be an issue. Furthermore, the oil will not evaporate and hence does not end up in the cylinder for lubrication.

 

[Rustkolector]

Xander,

Propane fuel would likely require a wet sump for lubrication of the cylinders and the crankcase interior. Propane provides very easy starting, and reduces exhaust odors. It also keeps the combustion chamber area very clean. I can’t say that for a wet sump crankcase though. Propane combustion produces a little more moisture than petrol combustion. If the crankcase oil does not get really warm during engine use the oil will often get milky looking with emulsified water vapor until the piston rings are well seated. The milky oil is not a problem if you change it after use and flush with WD-40. Unfortunately model engine piston rings don’t seat very quickly running at no load. A venturi in the exhaust pipe could help draw the crankcase vapors out but may not prevent this problem totally. Despite this minor drawback propane is still my favorite model engine fuel.

Jeff

 

[Steamchick]

Using a petrol bubbler may work? All Intake air drawn through liquid petrol to bubble... then the air-petrol vapour in the space above the liquid fuel being drawn into the intake, works for idling some engines.. lots on U-tube mixed in with rubbish.
K2

 

[xander janssen]

@Rustkolector

Thanks for the answers. Once I get it running on gasoline, I will look into converting it to propane. I already have all the parts for the demand valve as it can be found on the internet. Only detail I'm lacking is what pressure of propane I should deliver to the demand valve. Some state several (~4) PSI, but that is about 300 mbar, for which I have not yet found a pressure regulator here in Europe.

What pressure do you supply to the demand valve and what type/brand of regulator do you use?

Regards,

Xander