HELP: D-Valve or Spool Valve

[vederstein]

I've done a few steam engines, both oscillators and valved with spool valves.

Concerning the spool valves, I've had consistent issues with valve leaking too much. Sometimes the casting had a sink in it that caused problems, but I think I just may not know what the hell I'm doing.

Is an engine with a D-type valve and steam chest generally easier/more successful to build? I'm trying to get an engine to put out about a 1/8-1/4 horsepower to run a small lathe.

What's the break in period (steel/cast iron) usually to get the valve to seal properly?

Below are two videos of the engines, leaking a lot....

<iframe width="420" height="315" src="http://www.youtube.com/embed/R6wpWBVYBjw?rel=0" frameborder="0" allowfullscreen></iframe>

<iframe width="420" height="315" src="http://www.youtube.com/embed/gQogfGCLc3w?rel=0" frameborder="0" allowfullscreen></iframe>

Comments? Suggestions?

 

[vederstein]

The embedding didn't work.

Here's just links to the videos:

[ame]http://youtu.be/gQogfGCLc3w[/ame]

[ame]http://youtu.be/R6wpWBVYBjw[/ame]

...ved

 

[Philjoe5]

I'm no expert, but a few observations on the steam leaks....
What are you using for gaskets and packing in the packing glands?
The engine in the second video seems as if the timing is off

A "D" valve should seat after a few hours of running depending upon how much care you've put into the valve face and the matching cylinder face. Steam pressure works for you in pressing the valve onto the cylinder face.

The displacement lubricator should be as close to the steam chest as you can manage

You've got some good runners there that just need a bit of tweaking.

Phil

 

[aonemarine]

Ok here is one of those times when I sould just stay quiet but just cant. You are building "model" engines, they can run well but generally are not well suited to performing work. I dont know what else to say.....

 

[Jasonb]

I agree with Phil you need to look at your gaskets and gland packing.

On the first engine you can see condensate leaking out from each cylinder cover and both engines are loosing stem around the valve rod

J

 

[gbritnell]

Only a few changes would have to be made to a 'model' engine to turn it into a 'work' engine. In no particular order it would need a mechanical lubricator and not a displacement lubricator. All of the sliding and hinged points would need some type of constant lubrication. The last thing is the bearing material for the crankshaft would have to be a good bearing bronze.
I can only judge what I see on the videos and not knowing the tolerances you have built your engine to I would say that it's not so much the case of using a D valve as opposed to a spool valve but rather the overall construction. Most definitely you would need better packing and gasketing materials.
Not that it's not a worthwhile goal to have an engine do some work the logistics of trying to maintain water levels, steam pressures, burner control and lubrication all the while running the lathe seems like it would be a bit too much for a person to handle.
gbritnell

 

[RonGinger]

You do not have a problem with wet steam, your problem is a cold engine. You are going to have to cover up some of that neat paint striping with insulation- its called laging and all steam engines must have it. If the cylinder is a lower temperature than the steam it will cause the steam to condense and water drops fall out- you could use the hottest, super heated steam around and the cold engine would still condense.

When we start up a loco we open the cylinder drain cocks and crack open the throttle valve to let steam flow through the engine and pre-heat it. We rock the johnson bar back and forth a few times to heat both ends of each cylinder. As we pull out of the station we leave the cocks open until only dry steam is escaping and we know the cylinders are up to temperature.

A cold engine will run poorly and knock loudly. My traction engine actually wraps the cylinder in a steam jacket- like the water jacket around a gas engine- but its not to cool the engine its to heat the cylinder.

A spool valve needs to be a very close fit so it doesn't leak. In larger engines the spool valves had rings, just like the piston rings.. They are tough to make in model size. A D valve is probably easier because you can put an O ring or packing around the valve stem, and the rest of the chest is gasketed.

 

[Ken I]

A spool looks simple on a drawing but in practice its a sod to make and really needs to be lapped to fit (at least at model sizes). Wear = leaks, clearance = leaks.
A D valve my look a little tricky but in my opinion dead easy to make and is very forgiving. Wear generally seats it.

A poorly seated D valve can be fixed - a loose fitting spool can't so its rather unforgiving.

2c

Ken

 

[kvom]

An advantage of the D-valve is that you can more easily do without cylinder cocks. If there is excess water in the cylinder it will be forced back up the steam port and lift the valve, rather than cracking the head.

There are many steam launches working with displacement lubricators, so I would think that should be OK. Although a mechanical lubricator might be preferable.

On my loco, I've been advised about two ways of sealing gasket material. One is to coat the paper gasket with anti-sieze. The other is to mix graphite powder with oil and coat the gasket with that mixture.

 

[vederstein]

Thank you all for your comments. They are welcomed.

The purple engine is the 6CI from PM Research. It's a full sized 1/4 hp engine, a reproduction of castings from 1896 or so. The casting had a sink in it, so I pressed/epoxied a sleeve in the valve bore then made a spool valve to fit the sleeve. I made probably about 4-6 valves until I got one to work somewhat. The packing glands are silicone orings. I think that getting the spool valve to fit was just beyond me, especially that the sleeve was probably out of round after pressed into the bore.

I've got some other plans (engines in the pipeline). But when I get around to another mill engine, I'll probably give the D-valve a try.

Thanks again.

...Ved.