Chris's Build of Steering Engine

[cnr6400]

Oh THAT's where the pivot hole is, in the forked clutch operating lever. Couldn't see the hole in previous pics in post 279. I say forked, but in fact it looks great and perfectly serviceable....

 

[crueby]

Oh THAT's where the pivot hole is, in the forked clutch operating lever. Couldn't see the hole in previous pics in post 279. I say forked, but in fact it looks great and perfectly serviceable....

 

It didn't show in that picture since I hadn't drilled it yet!  Sorry if I forked it up!   

Right now I  am going through the options and thread sizes to figure out the upper shaft, which has several different threaded portions on it, one for the control nut (I am the nut in control, this is the one that moves the valve), one for the rudder position indicator, and one for the end stops.   

[cnr6400]

No comment on the "control nut" statement!  good luck with thread selection! 

Years ago I was in a shop on a crew tightening cylinder head nuts on a large diesel engine. One guy on the crew, Martin, was a real smart aleck. Foreman Jim comes by and sees a box of nuts on the catwalk, and says "aren't these the head nuts?" Martin says "we all thought you was the head nut around here Jim!" everybody got a chuckle on that one. Just a silly memory now. That was a fun crew. And yes, the engine DID run after we messed with it!

[crueby]

No comment on the "control nut" statement!  good luck with thread selection! 

Years ago I was in a shop on a crew tightening cylinder head nuts on a large diesel engine. One guy on the crew, Martin, was a real smart aleck. Foreman Jim comes by and sees a box of nuts on the catwalk, and says "aren't these the head nuts?" Martin says "we all thought you was the head nut around here Jim!" everybody got a chuckle on that one. Just a silly memory now. That was a fun crew. And yes, the engine DID run after we messed with it!

If you worked on airplane engines you would have needed Wing Nuts! 

[cnr6400]

 

[Michael S.]

Last picture:

were you or the elves here secretly coming to my house at night and scraping off the paint and taking a picture?
I haven't been to the garage today....

[crueby]

Last picture:

were you or the elves here secretly coming to my house at night and scraping off the paint and taking a picture?
I haven't been to the garage today....

I did send the elves there to box up the engine and send it home, but they got lazy and just brought me the paint!   


 

[crueby]

Got a hole drilled in the end of the pin - very tiny hole so I used a micro dental bur in the high speed air handpiece to nibble the hole through the end. Then a short piece of chain was wired on so the pin doesn't get lost. The pin end is .070" diameter.

[cnr6400]

 

[crueby]

Thanks Jeff!

After deciding on the thread sizes to use, it was time to make the upper shaft. I originally was going to use a 3/8" acme thread, but that wound up just too large for the control nut and the gear shaft, so I went back to a 1/4" Acme threaded rod instead, which will fit inside the half-lap on the control nut better. Either way, I would likely have to adjust the lenghts of the arms on the crank leading to the valve to get the proper travel.

So, here is one end of the upper shaft. I made the whole thing in one piece from a length of the 1/4" Acme rod. This is the end towards the cylinders. It has the Acme thread in the center to move the control nut, and a M4 thread at the very end for the stop nut on that sits in front of the front wall. I still need to add another threaded section at the front end of the Acme thread, for the rudder position indicator. That will be made on a seperate piece, drilled to match the shaft, and added on to the shaft. That will make it possible to slide it all into the bearing for the front wall.

The other end was turned down to a straight smooth section, just under the root diameter of the Acme thread. That end goes through the small spur gear, and holds the smaller of the steering wheels at the other end. I milled off one side of the spur gear hub at the front end to form the half lap to engage the control nut. Lots of moving parts in this area, this is where a lot of the magic of this engine happens!


Oh, and almost forgot to add a picture of the Acme nut that will become the core of the control nut. The outside will be turned down to take a cylinder with another half lap in it, more on that next time.

Chris

[crueby]

Forgot to mention - the small spur gear is going in the tank for nickel plating, pics of that done this afternoon...

[crueby]

The small spur gear was nickel plated, and the Acme nut was turned down round. Then turned the control nut, with the end at the groove counterbored out larger to fit the turned down nut:

A little Loctite retaining compound later, and the control nut shell has its internal Acme thread. The other end was milled off to form a matching half-lap to the one on the gear hub:

And here it is test fit on the engine:

So, now if the inner shaft is turned the control nut is kept from spinning by the gear half, and it moves one direction. If the gear turns the other way but the inner shaft stays still, the control nut is turned by the half lap on the gear, and the nut comes back to where it was. That is the key thing about how the mechanism works. The inner shaft is turned by the steering wheel, moving the nut, which opens the valve one way or the other. That makes the engine run to turn the gear the other way, bringing the nut back to center which shuts the valve, stopping the engine. Along the way, the turning of the engine spins the lower shaft with the chain sprocket, which moves the rudder chains, turning the ship.  Brilliantly elegant design! Someone with a great mechanical mind thought it up originally.

Now, to keep the inner shaft from sliding forward and back, I need to make a little spacer washer to go between the small gear and the rear wall bearing, plus a stop collar for the other end of the gear shank to keep the small gear from being able to slide. Then, I need to make the threaded collar that goes around the inner shaft just forward of the Acme thread for the rudder indicator. That will be large enough to act as a stop collar for the inner shaft.  All coming together well, very happy with the results so far. Time to sit and stare contentedly at the model while sharing cookies with the shop elves! 

[Kim]

Beautiful, Chris!   

Not only is that a very clever mechanism, it is also a very clever way of implementing it in miniature using the Acme threaded rod and nut!
Really enjoying your build, Chris!

Kim

[Michael S.]

Hello Chris,
very good way.
I took a few more pictures with details. The carrier has 2 cams, but of course it also works the way you do it. It's easier that way too.
In your drawing, the bracket for the linkage is drawn like the lever for the hand lever. In the original, a bronze ring that is divided and screwed slides in the groove.

Michael

[crueby]

Great detail pictures Michael! 




I never noticed that there were two lobes, a bit late for the model but I can update the CAD version and the plans. I really like the follower ring for the valve and will build it that way.  Hmm, since the crank arm swings, there must be some play in the ring up and down? The front and back sides of the ring are close fit, but the center of the ring must be elongated in the center?