Ohio Locomotive Crane

[crueby]

That's looking great, Chris! 

So, with that lever arrangement, isn't there going to be a little vertical motion in addition to the horizontal movement that you want for the valve rod?  Is the hole at the end of the valve rod large enough to accommodate that vertical motion?  Enough so you won't get binding between the valve rod and the valve gland?

Kim

Yes, but the horizontal motion is very small, so the vertical motion is even smaller, since the lever has a radius of 0.6". Its common to see this kind of arrangement on steam engines - the Lombard had it, many of the steam shovel slew/crowd engines had it too. The rod can pivot that tiny amount in the gland, and the valve slider is free to move across the valve face if needed. Even without this motion, I like to make all the piston and valve holes slightly larger than the rods so they dont rub, and let the o rings hold the rod in the center.

[Kim]

That's looking great, Chris! 

So, with that lever arrangement, isn't there going to be a little vertical motion in addition to the horizontal movement that you want for the valve rod?  Is the hole at the end of the valve rod large enough to accommodate that vertical motion?  Enough so you won't get binding between the valve rod and the valve gland?

Kim

Yes, but the horizontal motion is very small, so the vertical motion is even smaller, since the lever has a radius of 0.6". Its common to see this kind of arrangement on steam engines - the Lombard had it, many of the steam shovel slew/crowd engines had it too. The rod can pivot that tiny amount in the gland, and the valve slider is free to move across the valve face if needed. Even without this motion, I like to make all the piston and valve holes slightly larger than the rods so they dont rub, and let the o rings hold the rod in the center.

Alrighty, then! Cool, I knew you had it all figured out, I just wanted to understand.  Thanks for the explanation, Chris!

Kim

[cnr6400]

  Like Mr Stewart Hart used to say - "A little clearance never got in the road".   

[bent]

Wow, nice work Chris! 

[crueby]

Thanks guys!

And speaking of clearance, there is not much between these levers and the crosshead - going to be a little trimming needed on the side of the crossheads to increase the gap, it would be destructive if they collided!

[john mills]

i see the valve rod move meant i wonder how they kept the glands when working on the full size engines as these clearances kept minimal  and good alignment is what is important to keep gland  packing lasting and working .

[crueby]

i see the valve rod move meant i wonder how they kept the glands when working on the full size engines as these clearances kept minimal  and good alignment is what is important to keep gland  packing lasting and working .

On the full size engines, the vertical/arced movement is still tiny. For example, on the Lombard engine, the lever has a radius of about 6", and it only moves about 1" from the top/center position of the lever. Here is a picture of it. Green arrows show the pivot/end of the lever, moving the valve rod marked in red:

With those dimensions, the rod end only moves about .083" vertically total, and if they split the difference and had the center half above the line of the rod, thats only a 0.0415" movement from the centerline of the rod, assuming the joint at the end of the rod has no play in it. That works out to less the 0.2 degrees on the rod. Since the end of the rod inside the steam chest is not restrained, but can float in the valve slider, there is no bending moment on the rod. Thats very little rocking that the gland needs to absorb. On the full size engines, that packing is likely some sort of fiber material, not just a bronze bushing. And, on the full size engines, a tiny puff of steam from glands is not uncommon as they run.

[crueby]

Got the levers/bases for the valve rod ends prettied up and installed:

Hard to tell in the picture, but the center section of the lever is recessed both sides.  So, on to the last pieces before applying compressed air to the pistons: the eccentric straps!  I need to get the stock prepped for them and start machining.

[PaulR]

With those dimensions, the rod end only moves about .083" vertically total, and if they split the difference and had the center half above the line of the rod, thats only a 0.0415" movement from the centerline of the rod, assuming the joint at the end of the rod has no play in it. That works out to less the 0.2 degrees on the rod. Since the end of the rod inside the steam chest is not restrained, but can float in the valve slider, there is no bending moment on the rod. Thats very little rocking that the gland needs to absorb. On the full size engines, that packing is likely some sort of fiber material, not just a bronze bushing. And, on the full size engines, a tiny puff of steam from glands is not uncommon as they run.

Wonder why they didn't just make the lever rock either side of vertical and knock spools on the valve rod as some water pumps do, to get rid of the turning force altogether? When were the originals made?

[crueby]

With those dimensions, the rod end only moves about .083" vertically total, and if they split the difference and had the center half above the line of the rod, thats only a 0.0415" movement from the centerline of the rod, assuming the joint at the end of the rod has no play in it. That works out to less the 0.2 degrees on the rod. Since the end of the rod inside the steam chest is not restrained, but can float in the valve slider, there is no bending moment on the rod. Thats very little rocking that the gland needs to absorb. On the full size engines, that packing is likely some sort of fiber material, not just a bronze bushing. And, on the full size engines, a tiny puff of steam from glands is not uncommon as they run.

Wonder why they didn't just make the lever rock either side of vertical and knock spools on the valve rod as some water pumps do, to get rid of the turning force altogether? When were the originals made?

The lever does rock either side of vertical. These machines date to aearly to mid 1900s. I've seen the same thing on many manufacturers machines, and they all work just fine for many years (some still running at museums today). Ass I mentioned, the angular deflection is tiny, and does not cause any problem. I have the same setup on several models, they all work fine too.

[cnr6400]

 

[crueby]

I've gotten a good start on the eccentric straps. Cut strips of brass flat bar, notched the ends of the end caps, and drilled/tapped the pieces so they could be bolted together:

Then set up the four jaw chuck on the rotary table, and centered up the first bar with the center of the eccentric hole on the center of the rotation - took a few tries and tweaks of the jaws to position it, but got lucky that the flats on the bar were reached by the sides of the jaws so they would squeeze down and hold it. Then drilled a starter hole for the end mill. One the left, is the plug gauge I made when I turned the eccentrics a while back, turned on the same bar and at the same time/same handwheel settings as the centers of the eccentrics. I'll use this to gauge the size of the holes, which will save taking the parts out of the chuck and removing the caps to test fit them on the eccentric, which has raised lips on the edge to retain the strap.


Then after a lot of round-and-round turning of the rotary table, got the first hole out to size

When I got close to the final size, I frequently raised the cutter and checked with the gauge and the calipers till it was a nice fit:

Then milled in the extra recess at the edge that will fit over one of the lips on the eccentric - the straps are slightly thicker than the center of the eccentric slot:

Same was done on the other strap, then set up to do the final shaping of the strap:

Lots more shaping to go...

Another background project over the winter was working out the design of another steering engine, to go with the one I built to match Michaels full size engine a couple years ago. Since then I've found original blueprints for a few other engines, on the US National Archives site and the MIT library site, as well as catalogs and patents from other companies. There were quite a few variations on the mechanism, and I learned that some, like Michaels German one, had the extra gearing and clutches to let the same machine do both steam-assisted steering and totally manual steering if the engine or steam supply went offline. Other steering engines only did the steam assisted steering, and on those ships they had a separate manual steering setup, with disconnects on the shafts. Some of the Navy ships would have several options as backup. What I designed is the second type, without the manual steering option, which removes a set of gears and clutches, simplifying the engine quite a bit. This engine looks more like the one I saw at the engine show at Mystic Seaport several years ago, as well as ones made by Hyde Manufacturing and also by Herreshoff. Here is a CAD screen capture of what I've come up with. This may be the next build after the crane model is done. Or the build after whatever else I decide on next...  This design uses the same 4-port D valves for reversing with a single eccentric set that most steam shovels used, where most of the steering engines used a spool valve setup instead - I prefer the D valve style for the models more, much easier to get a good seal.

[cnr6400]

 

[Kim]

Nice start on the eccentric straps, Chris!   

And now I get to look forward to another steering engine!  How fun is that! 

Kim

[crueby]

Nice start on the eccentric straps, Chris!   

And now I get to look forward to another steering engine!  How fun is that! 

Kim

Or maybe two. One of the plan sets I found was for the steering engine on the battleship Arizona (of Pearl Harbor fame), I have been studying those plans to figure out its mechanism. The plans show all the parts, but not a good view of how they all go together, so going to take some investigation. May need to draw the parts in CAD and see if the 3D parts go together in a meaningful way. I also have the plans for the propellor turning engine from the Arizona, that one is a lot more straightforward. Years ago I drew up the steering engine from the USS Kearsarge - that one all makes sense, but its a huge and complex engine. The engine itself is the chunk in the middle, tow the left are the manual steering wheels (about 8 foot diameter, three to allow a whole bunch of sailors to apply muscle), on the right is the screw shaft mechainsm to actually turn the rudder post at the far right. Huge mechanism in real life!