Chris's New Steering Engine

[crueby]

Hi all,
With the Ohio Crane model complete and some improvements done on the mill and the shop cleaned up, its time to start in on a new engine. This time it will be another steering engine. These steam engines were used on ships right through WW-II when they were replaced with hydraulic and electric driven equivalents. They take input from a steering wheel, and use that to control a valve which runs the engine forward or reverse until the rudder position matches where the steering wheel was turned to - the original power steering! The feedback mechanism in them works a lot like a rodaio-control servo does, just using mechanical linkages rather than electronics and sensors. They were invented in the 1800s, and went through many different designs though most worked on the same principals. They were needed when ships got so large that the rudders were too big to turn and hold by hand againts wave/motion pressures.

Here is the model I built a couple years ago, its based on the original engine that Michael owns, from a German paddle steamer:

And here is the design for my new one:

It functions in the same basic way, with a number of differences. The other one has a set of clutches and a second steering wheel to allow for manual steering (with more gear reduction) in the case of loss of the steam engines or steam supply. It has a rudder indicator built in to the main shaft, and uses a set of crank arms and linkages to get the control input down to the control valve. The cylinders use spool valves, switched by the control valve between center admission and end admission to control the direction of rotation.

On the new design, based on the style used by Navy torpedo boats and others, is a simpler design. In these engines, the manual steering backup and the rudder indicator were done outside the steering engine. It uses a direct linkage from the control shafts to the control valve, eliminating the cranks and links (which is good for the model, less motion loss in all those connections). Also, I have changed from the spool valves to the 4-port valves and double layer D valves as used in steam shovel slew/crowd engines. These valves are simpler to make and get good seals on at model scale. Other than those changes, the function of the feedback mechanism is the same.

The model will be built with 1" bore/1" stroke cylinders, and will sit on a 6" x 6" base.

The feedback and control valve setup on steering engines is pretty clever. Here is a diagram of the main shafts:

The steering wheel at the left end turns an inner shaft that runs about halfway down the length, to where the threaded section is. There is an outer shaft that spins seperately - the center of that shaft, between the two bronze bearings just left of center in the diagram, holds the worm wheel that is turned back and forth by the engine. That shaft also turns the grey piece in the center, with long flats cut into it. Those flats turn the bronze colored control nut.

So, when the steersman turns the steering wheel, that turns the threaded section, causing the control nut to move in or out - the control nut is kept from spinning by the flats mentioned above. The control nut moves the valve rod at the right end - this rod is concentric with the steering input shaft but is seperate from it. When the valve rod moves, it pushes/pulls the D valve in the control valve, sending steam down one pipe and taking exhaust from another, those pipes lead to the 4-port valves on the cylinders, making the engine start to spin. As the engine spins, a worm gear on the crankshaft turns the worm wheel mounted on the outer shaft (see the picture above this diagram to see those gears). As the worm wheel turns the outer shaft, that turns the control nut via the flats. That turning of the control nut re-centers it, which pulls the control valve closed again. Quite clever! As the outer shaft turns, that also turns the chain sprocket, moving the chain that leads to the rudder. You can see a video of the action here, on the first steering engine model:
<a href="https://www.youtube.com/watch?v=pKp-J9aGXiA" target="_blank">http://www.youtube.com/watch?v=pKp-J9aGXiA</a>

Thats where this build will go with the new design. This morning the shop elves went up to the bandsaw, and cut me the kit of parts for the cylinders, end caps, crosshead guides, and the base plate. The cylinders/guides are being made from 1-5/8" brass roundbar, all taken from a 4' length I picked up at Yarde Metals Drop Zone, where they sell offcuts from their commercial supply at a very good price. The whole bar cost me about $100, and this model is only using a fraction of it.

Then I spent some time on the lathe, getting the end caps trimmed to thickness, and the other bars trued up on the ends. The cylinder/crosshead bars are all about 1/2" over finished length, to give me room to chuck them up. The outer ends you see will be the mating surfaces at the piston rod gland end, to ensure the bores are square to the mating ends. The other ends will be trimmed off after all shaping is done. The outer ends of the cylinders get the end caps, which are less critical to alignment. First I cut the outer profile on the cylinders, and drilled a starter hole down the bore:

Likewise with the crosshead guides. The left end of the guides, up by the chuck, will be the ends towards the crankshaft. Those ends have a smaller flange than the other ends, since they do not need a bolting flange.

Next will be to rough out the bores close to the final ID, final cutting will be done later when the bolt circles are drilled in. The cylinders need flats cut on the outsides to silver solder on the steam chest bases and the floor mount blocks. The final boring will get done after those steps are done, in case there is any movement from the silver soldering and milling steps.
 

[redhouseluv]

wow - a new start already Chris, and moved from trains to ships! It looks like another great challenge, I never realised that was how the steering mechanism worked.

[tghs]

he'll be done with it Sunday afternoon..

[crueby]

he'll be done with it Sunday afternoon..

Don't  exaggerate. Monday morning!   

[cnr6400]

Maybe we should start a pool like they do for when kids are born. My guess is Tuesday afternoon at 2:35. 

Just joking Chris, looks like a great start on the steering engine version 2. 

[Michael S.]

It's always amazing how many versions of steering motors there are. Your new motor looks great, and it's going to be an interesting project.

That reminds me: the paddle steamer, which is a museum in my town, also has a steering engine that looks completely different. I definitely have to go there and take some photos.


Michael

( I found a picture on the internet. )

[crueby]

It's always amazing how many versions of steering motors there are. Your new motor looks great, and it's going to be an interesting project.

That reminds me: the paddle steamer, which is a museum in my town, also has a steering engine that looks completely different. I definitely have to go there and take some photos.


Michael

( I found a picture on the internet. )

Interesting  layout! I've seen  other ones with the angled cylinders like that in some of the early patents, and in catalogs like from Hyde if I  recall  correctly.  It would be interesting to see  more pictures and details of that one.


The Liberty Ship had a fairly large one, cylinders on either side, that was geared directly to the rudder post. That one had control rods leading forward and up to the bridge where the steering wheel is. All sorts of designs of them! Until I  saw the one at Mystic Seaport I  never knew about steering engines, never thought or realized they would be needed.

[crueby]

After drilling/boring the cylinders and crosshead guides out to 0.8" of the 1" final bore, I moved over to the mill to cut the flats for the mounting bases and steam chest bases. Measured a number of times to ensure these flats would not encroach on the final bores!

and also cut/trimmed the blocks for the bases. They fit between the flanges at the ends of the cylinders. Final cut was a light truing cut on the faces that will be against the cylinder flats and soldered, since raw flat bar stock is never quite flat and true - holding a piece against a good straightedge and up to a bright light will usually show a little wavyness across the width.

Here are the parts so far:

Next step will be to drill/tap some for some small screws to hold the blocks in position against the cylinders for soldering, then will take them outside to silver solder them. I also like to put a few small center punch marks on the flats of the blocks so there will be room for the solder to wick in.

[crueby]

Was up bright and early today (well, it was cloudy, so dim and early?  ) and got the screws in to hold the mounting base and the steam chest base drilled/tapped for a brass screw to hold them together for silver soldering. The holes were drilled tap-size in through the joint, with the blocks  clamped in place, then tapped with the blocks still in the clamps. That way there is no clearance size hole to give it wiggle room. Here are the parts, ready for soldering:

The screws are to the side of future fasteners and passages. Turned out one screw on each was enough to hold things. Then outside to solder them up, and into the pickle solution for a while to clean them up. The solder flowed nicely through the joints, and I could even see it come out up higher at the edges of the flanges - I used some extra solder to ensure good coverage right through the seams, so there would be no leaks out from the passages. Here are the parts so far:

Then, after making a list of steps for all the operations to come, I chucked up the first cylinder and took a light trueing cut down the bore. You can see that I used a hose clamp to attach a scrap block of brass to counterbalance the cylinder, the two soldered on blocks took it way off balance and made the lathe want to shake above very low speeds. With this on there, it runs pretty smooth. I have some stick-on wheel weights that I could have used in addition, but were not needed this time.

Then got out the bore gauge, and found the right tip combination for this size hole, and checked for any taper down the length of the bore.


It turns (pun!) out that there was a couple thou difference end to end (over 1.6") so I tweaked the headstock over slightly, and on the second attempt it was right on the money. Got lucky, usually takes a couple tries. So, then was ready to bore it out the rest of the way. I swtched to a larger diameter bar, since this one was ringing just a little at higher speeds - it was no problem on starting the hole, but now that the hole is larger I could switch over.


The bore came out glass smooth, and I also took a trueing cut on the face of the flange so the crosshead guide would bolt on square to the bore, and put a slight chamfer on the corner into the bore to make it easier to get the piston/ring started.
Next session I'll move the chuck with the cylinder still in place over to the rotary table on the mill to drill the holes for the end cap and crosshead to attach to. Then will chuck up the end cap, drill it, as well as the hole for the piston rod and its ring. Then bore and drill the crosshead guide to match the hole pattern. After that, will do the same sequence on the other cylinder. After all that, it will be time to trim off the excess material at the outer end of the cylinder, and drill it and the end cap. Keeping things in this order should ensure that all the parts line up when bolted together. Lots to keep track of, which is why I started by making the list!

[Michael S.]

The cylinders don't have any time to rest. They're always rotating, and then they have to lose weight.

A good start on the cylinder! 

Michael

[crueby]

Thanks  Michael!

[cnr6400]

  Great start Chris! and I caught the "turns" pun. (didn't even use AI, just I )   

[crueby]

Great start Chris! and I caught the "turns" pun. (didn't even use AI, just I )   

Thanks!  And artificial puns just never taste the same!   

[crueby]

Some more time in the shop yesterday afternoon when the rain rolled in, and this morning. Got the second set of cylinder parts bored out like the first, and also the end mounting holes drilled/tapped. Each cylinder part was drilled/tapped for the mounting holes while still held in the chuck for boring. Set up the rotary table for the first cylinder, and kept that position through all the parts. First the cylinder,

then the crosshead guide

then the base end cap

While the cap was still in the chuck, the piston rod hole was drilled and the o ring recess bored in as well

After both cylinder sets were done to this stage, then set up and drilled for the piston rod gland mount holes in the end caps

and turned/drilled the glands to match

Then set up the vertical rotary table to cut the openings in the sides of the crosshead guides. Milled in from the side first

then opened up the window with a vertical cut on each side

Here are the parts so far, set on the base plate blank. Still need to cut the side openings in the second crosshead guide, then can cut the cylinders/guides off their bases...

But, its warming up outside and the afternoon rains are still a couple hours off, so outside I go!

[Kim]

You're really moiving along quickly on your new steering engine Chris!  Cylinders, caps, and crosshead guides already!  That's impressive! 

Kim