A S.T. steam hammer build

[crueby]

Great looking cylinder, Chris! 

Kim

Thanks Kim!  The cylinder and valve are about it for the engine, no crankshaft, eccentric, con rod, any of the usual stuff, which is great for a 'quick' build between big projects.


One thing I need to decide on soon is the lead of the passages. The original spool valve is inside admission, and it depends on the valve movement directions for the auto shutoff of steam when raising the piston/hammer. There is a lever the hammer end hits to push the valve vack to neutral and stop the rise.


Since the d valve is outside admission, it operates in the opposite directions. That means to keep the auto stop on raising that I need to reroute the passages to swap the leads to the end ports. Should be simple, just need to lay it out before drilling the passages.


Also, as part of that, I'd like to incorporate a needle valve into the lower passage so I can tune the flow to the bottom end of the cylinder and limit how fast the piston can rise since there is no crank to limit movement like a typical engine. Again, easy to do as long as I plan it out first.

[vtsteam]

When they used these, and there was a long pause, was the hammer left in a lowered position? Would the steam cool and condense in the extended portion of the cylinder?

[crueby]

When they used these, and there was a long pause, was the hammer left in a lowered position? Would the steam cool and condense in the extended portion of the cylinder?

That's a great question. I'm guessing since I have no experience with these machines, but seems like you are right about leaving it down, especially if the main steam supply was shut off and things cooled. With perfect seals everywhere, the vacuum at the top could hold the piston up, but even a tiny seep around piston rings or in the valve would let air in, even if the valve was left in the neutral off position.

[vtsteam]

Thanks Chris.

[Charles Lamont]

Also, as part of that, I'd like to incorporate a needle valve into the lower passage so I can tune the flow to the bottom end of the cylinder and limit how fast the piston can rise since there is no crank to limit movement like a typical engine. Again, easy to do as long as I plan it out first.

If you are only ever going to run it on air, you could (in theory) put a needle valve in the exhaust from the top of the cylinder. This is the way the speed of an air cylinder is usually controlled, as it gives a much stiffer and more predictable system than restricting the inlet. 

[crueby]

Also, as part of that, I'd like to incorporate a needle valve into the lower passage so I can tune the flow to the bottom end of the cylinder and limit how fast the piston can rise since there is no crank to limit movement like a typical engine. Again, easy to do as long as I plan it out first.

If you are only ever going to run it on air, you could (in theory) put a needle valve in the exhaust from the top of the cylinder. This is the way the speed of an air cylinder is usually controlled, as it gives a much stiffer and more predictable system than restricting the inlet.

How would I restrict the exhaust from the top without restricting the flow on the power stroke? Its the same passages used for both. 
Your question made me rethink my idea - the way I was thinking would have slowed the exhaust from the bottom as well as pressure going in, cutting the effectiveness of the power stroke. Better to stick with what the original models did, and have a stop on the control lever to keep the up stroke inlet from opening too far!
 

[Charles Lamont]

How would I restrict the exhaust from the top without restricting the flow on the power stroke? Its the same passages used for both. 

You would need a 'pneumatic diode' in parallel with the needle valve, such as a ball valve. But I do not suppose all that could be squeezed
in to the space available. Of course, if you had stuck with the inside admission piston valve, you could have put the restrictor in the exhaust downstream of the valve.

Your question made me rethink my idea

Glad to be of service

Alternatively, could you limit the valve travel so that on the up stoke it is only cracked open?

[crueby]

How would I restrict the exhaust from the top without restricting the flow on the power stroke? Its the same passages used for both. 

You would need a 'pneumatic diode' in parallel with the needle valve, such as a ball valve. But I do not suppose all that could be squeezed
in to the space available. Of course, if you had stuck with the inside admission piston valve, you could have put the restrictor in the exhaust downstream of the valve.

Your question made me rethink my idea

Glad to be of service

Alternatively, could you limit the valve travel so that on the up stoke it is only cracked open?

My last sentence mentioned the stop on the lever, that is the usual way people have done it.


And the downstream exhaust is shared on both piston valve and d valve. Same passages both ways i  the plans.

[Jasonb]

It would depend on how Stuarts have done the porting and whether inside or outside admission. But with an inside admission piston valve there are two exhausts from the piston chamber one of which could have the adjustable restriction as arrowed in red, the lower exhaust from the valve bore is not restricted . Not critical if they join up later to form one single exhaust connection.

This would not affect the passages between cylinder and piston bore which are shared as inlet and exhaust in the same way as slide valve ones are shared.

[crueby]

Stuart did it as inside admission with one exhaust out the top, a hole through the piston valve. Doesn't matter much since I am using a d valve.

[crueby]

Continued on with the bottom gland cap, drilled the mounting holes

and installed the gland cap

then turned/drilled/tapped/installed the top cap from the leftover piece of the cylinder

I figured out where I wanted the passages, and laid out the pieces for the mounting flanges, drilled/tapped for them

and made the flange bars. The mounting bolts are countersunk in to allow the plates to sit flush against the column and the steam chest

The mounting holes themselves on the lower bars will be drilled after I get the column casting, just in cast the dimensions need to be tweaked from the drawing. So next steps will be to drill the passages, then can start on the steam chest itself...
 

[cnr6400]

Looking great Chris! 

[crueby]

Looking great Chris! 

Thanks CNR.  This model is a nice break from the big projects, seeing it take shape quickly is nice!

[vtsteam]

Really nice! 

[crueby]

Thanks Steve!

Next up was to drill the steam passages. Unlike the original kit, this model is built up from bar stock, which allowed me to change the valve/passages up a bit. I'm not a huge fan of piston valves, so I decided to make this one with a D-valve. To keep the direction of movement on the lever vs the piston/hammer the same I need to make the bottom cylinder passage go to the top port, and vice versa. That will allow the same cutoff lever setup from the original still work with the outside-admission D-valve vs the original inside-admission piston valve. So, I drilled the passage holes from either end offset from center so they could pass each other.

The recess to connect the passage end to the cylinder was also milled in on each one

and then connected the ends of the passages up through the steel backer plate. This plate is NOT getting the ports cut in it for the valve, there will be another thin valve plate on top of the steel for that. Since the passages are off center , these holes are off center too, so will need a little milling to connect them better to the ports in the brass plate.

While doing the drilling, also drilled through the exhaust port in the side of the steel plate

Then went back and added the milled slots to connect the end passages to the port plate better:

These openings don't need to be precise, the brass port plate will do that, and some gasket goop will seal between the plates.
So, next time I'll start in on making the port plate and the steam chest...