3/4" Scale Cylinders

[jbodenmann]

Here the holes for the #2-56 model bolts that will hold the slippers in place are being drilled after being located with the digital read out and spotted with a center drill.

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[jbodenmann]

And finally the slot for the main rod (connecting rod) is being chundered out. These last several operations have been made without removing the part from the spindex, thus mainaining squareness and alignment. A collet was used to hold the work piece as that is the most accurate way of holding things that I have available. Go with what you got!

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[jbodenmann]

Now that all the milling has been done our little crosshead will be returned to the lathe, using the same collet. The hole for the piston rod will be center drilled, drilled and then bored to the one in five taper utilizing a tiny boring bar. The piston rods were machined in the same set up so that the tapers would be identical ensuring a good fit. The crosshead was carefully bored and opened up gradually, all the while testing the fit of the piston rod until it was just right. Easy peasy!

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[jbodenmann]

And finally, after all the machining was done the crosshead has been cut off of the end of the length of one inch round stock and finished off nice and square. Holding little bits like this it seems is always the bugaboo. The tyro frequently makes the mistake of cutting off a tiny bit of metal from that which would be most useful to hold it with, and then tears his or her hair out trying to keep it from coming adrift during machining. In this photo the crosshead is stuck to the end of the piston rod just to have a look. Now we can start on the slippers.

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[jbodenmann]

Here is the start of the slippers. A lump of aluminum bronze and some scribbles. Even though I have some beautiful full page drawings of the parts to be made I will usually sketch up a drawing of my own on a 5" x 7" note pad. This is done for two reasons, first and foremost is to fully familiarize myself with the part to be made, and any notes or scribbles can be made on the note pad instead of the actual drawings. Then most of my little note pads get glued into a note book concerning the project at hand, listing any problems and the hours worked for future reference. These note books have come in very handy to refer back to at a later time.

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[jbodenmann]

Here the slippers ( I'm not sure that is really the correct name for this part ) have been fitted to the crosshead, and after careful measurement the slots for the crosshead guides will be cut.

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[jbodenmann]

Now

[jbodenmann]

Now the slots have been cut, and the parts have had a good going over with a fine file and some #400 grit abrasive paper. Metal finishing is an important part of fine model building, just as good paint work can improve a good model. Things have been stuck together to have a look and now work can proceed on the castings that hold the crosshead guides. Careful fitting and measuring will pay off here as for the engine to run smoothly and not beat itself to bits these parts must be correctly aligned. Merry Christmas My Friends.
Jack

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[alanstepney]

Jack, It is interesting that you started on the crossheads with round bar, then milled it to a rectangle.

I would have started with square/rectangular bar, then turned the circular parts.


Of course, there is no absolute "right way" to do it, it is just a matter of personal choice.
I just find it interesting that people tackle tasks in different ways.


Or was there, perhaps, some specific reason for you doing it the way you did?

[jbodenmann]

Hi Alan
Good question, I considered making the crosshead from rectangular material but that would require the use of the four jaw chuck and some means of centering the part. As the part went from the lathe to the mill and back to the lathe again this would require indicating the part several times. The use of the collet in the both the lathe and spindex maintained center, and eliminated much fiddling about with the indicator. Use the materials and techniques that you are comfortable with. The equipment that you have laying around also dictates how things are done.
Happy Model Building
Jack

[Smifffy]

Nice work and great pictures. Please keep us updated going forwards.

Smifffy