Bushed

I have been continuing sporadic work on the beam engine with today being a relatively quick wee part: a bushing to hold the crank shaft onto the crank. Given that this part was about 1/”8 in diameter and 5/16″ long, it is one of the smallest things I have attempted.

My ML7 lathe was supplied with an excellent ER25 collet set that mounts directly on the lathe spindle. I thought it would be useful but I am still growing in appreciation of just how much. Holding onto the 1/4″ round brass bar I started with was no problem but niether was holding the finished 9/64″ barrel so I could turn off the remains of parting off. And, as is the special property of collets, it did so concentrically as far as I can tell. Which is just as well since I needed to finish reaming out the center hole from that side.

I find this especially exciting since this is getting into the range where I could turn bushing, bearings and the like for 1/4″ scale railroad models if I need to.

Beam Engine Crankshaft

Having finished the crank, the obvious next step is the crankshaft. This will link the flywheel to one end of the beam and introduce the first interesting motion to the project. It is also the start of the wee small bits, at least according to my experience. Learning experiences were anticipated.

First I tackled the end that goes on a pin sticking out of the crank. I again used the method of milling the piece out of a larger bit of stock with the extra used to hold on to. In a flash of enlightenment, I realized I could up the game a bit by using my small toolmaker’s vise to hold the stock. I could then rotate the part 90 degrees without unclamping the stock.

The major work was done with the vise clamped to the rotary table. The fun bit was getting the appropriate spot centered on the table. I did this by center punching the spot, deploying my fancy new coaxial indicator which came with a tip for just such a purpose and gently tapping the vise around until it was centered. I then clamped it down and rechecked to make sure I didn’t shift it. Surprisingly, I also managed to get the thing square in the x-y plane to within 30 arc minutes. (I needed to know where to start and stop the rotation of the table to be planar with the straight sides of the piece.)

After I got the main body of the piece shaped and drilled, I needed to drill a hole in the flat end for the shaft. This was easily done by clamping the vise on its side in the mill vise. I found the edges by using a drill blank because there wasn’t room to get my center finder in there next to the vise jaws. I know that things are at right angles because the toolmakers vise has precision ground sides for just this sort of thing. I may have committed a sin by clamping on the jaws of the vise, though.

The last operation was just reclamping the piece wide side up and skimming off the back side. This was easy in this case because there are two parallel sides unlike the crank.

Next, I made up the crank shaft itself which was a simple matter of threading one end of a 3/32″ brass rod and cutting it to length. For the exercise, I used the lathe to square and shorted to final length the cut end. Here is the piece to date. I still need to do the other end which has a fork to go around the beam. I added my machinist scale to the photo for a size comparison.

Starting the Beam Engine Cylinder

I have been having a really hard time getting off my duff and down to the shop so I actually started the beam engine cylinder block about a week ago, got called away and took this long to get back to it. But back to it I got where I finished turning the bit on the bottom that goes into a hole on the base and got set up in the mill to put in the holes for the piston aka the cylinder proper and, in this design, a parallel hole for the valve as well as a couple of screw holes to hole on the cylinder head.

This is the first real use of the lathe DRO and I am getting the hang of it. It is also my first real use of high speed steel lathe tooling. I had been getting by on carbide insert tools but the ML7’s top speed is only about 1100 RPM and that is low for brass and HSS, nevermind carbide. Also of note is my fancy aluminum shim stock(aka Coke can) protecting the brass hex bar from the chuck jaws.

Here is a dry fit shot of the progress to date.

I put the vise back on the mill table, got it squared up and the cylinder set up in the vise. I left it there because I am thinking that doing the head first would be better since I could use the holes in the head to place the valve and screw holes. A bit of thought prior may save me some aggravation later. I have learned that it is possible to machine a part into a state where you have no good way to do the next operation.

Miscellaneous Update #1

It’s been more than a week and I have no significant progress to report or at least anything that photographs. I have nevertheless made some progress on a couple of items.

Firstly, I have completed the beam engine beam to a functional if somewhat imperfect state. I messed up the rounding of one end but as that is cosmetic I just cleaned it up as best I could with a file. The original plans expected that the entire shaping of the round ends would be done with a saw and file so I am not way off.

I need to cut and fit a couple of shafts so I can assemble the progress so far. I have also begun on the last major piece, the cylinder itself. Not that it is the last piece of interest but everything else is in the nature of connecting things together.

Secondly, I have got enough code done on the traverser controller to be able to manually move the table at least once I get it connected to said table. I thing that needs to be the next thing since I have no sense of how fast the motor need to rotate to provide satisfactory move times nor how steep of an acceleration I have have without tipping over the stock on the table.

Milling Pallet

Much of my shop time in the last year(!) has been consumed with making tools for my tools. A later addition that turned out to be way more useful than I expected is my milling pallet.

A milling pallet is a flat piece of metal with a bunch of threaded holes in it. Matching bolts, clamps, and whatever are used to fix pieces of stock in place for machining. Mine is a 6x6x1″ square of aluminum with a grid of holes spaced 1″ apart. This is a common shop project so there was lots of ideas to glean from the internet but here are the features I settled on:

  • Through holes are tapped M6 except that the top 1/4″ is reamed .25″ to take dowel pins. The pins can be used as something to bump against in a repeatable setup.
  • A shallow step is milled into the bottom to allow clamping the pallet into my milling vise. The edges of the pallet are square with that step which means I can use the edges to align things, even before clamping the vise.
  • Extra counterbored holes allow me to bolt the pallet to the top of my rotary table. The rotary table only has four radial t-slots so this greatly improves my clamping options.
  • I made two sizes of .25x.50″ toe clamps that combine with an assortment of M6 hardware to do most of my clamping.

Here is the flywheel for my beam engine project in progress clamped on the pallet on the rotary table.

Beam Engine Progress or Go With What You Got

I have gotten out of the habit of regular posting as my current machining focus is a bit off the beam from what this blog started out as. I have finally admitted to myself that it will be a while before significant model railway activity takes place and also have reminded myself why I chose the blog name I did. So, I shall report on what I am doing in hopes that it will be of some interest albeit perhaps not to exactly the same audience.

To recap, I have been developing my machining skills by working on a model beam engine based on plans by Elmer Verburg. This engine is commonly referred to as #24 (Elmer created many plans and made them freely available, may he rest in peace). I have done the base, flywheel bearing, flywheel, eccentric hub, and column. Here is a dry fit of those pieces.

The part in progress is the beam. This is attempt the second as the first effort is now part of the scrap pile with the end of a #55 drill firmly embedded in it. Trying to drill that size of hole with the lathe going at 1100-ish RPM was not a success. The mill going at 4300 and a less ambition depth did the trick.

There are three 1/16th inch reamed holes in that piece. Photographing shiny aluminum close up is still something I need to work on.

Next step will be to flip the part over and mill it down to final thickness and take off the edges at an angle to produce an elongated lozenge shape. I have a plan but it may not work out. On the other hand, the only crucial dimensions on this part are the holes and the thickness of the hub. All else could be done with a saw and a file.

Model Building of a Different Sort

It has been quite some time (March!) since I posted. I have not been idle but work on Comstock Road has been minimal although I have enjoyed a few impromptu operating sessions which have gone surprisingly smoothly given the general lack of activity.

I recently reached a point in my machining journey where I felt it was time to make something that wasn’t a tool for making things. I hit upon a site containing many plans for model stationary steam engines created by the late Elmer Verburg. These plans can be built from standard metal shapes without the need for castings which makes them ideal for beginners who may need multiple attempts to make a part(ahem).

I have begun the process of creating a horizontal beam engine aka Elmer’s Engine #24. I have three parts made with the second and third requiring two attempts each due to measuring errors caused by duffing fractions to decimal conversions. I need a wall chart.

Anyway, here is the project to date with the base and flywheel bearing assembled. Eccentric hub not show as it is currently clamped in a vise awaiting drilling and tapping for a set screw.

All of those holes will eventually get something in them. It is an interesting contrast to the usual railroad model build in that each part is a project in itself requiring planning, setup and machining. It has also been a good skill bilding exercise as I have had to execute a variety of new operations.

Next part will be the flywheel, I think. This will be all kinds of new challenges as I deploy my shiny new rotary table for the first time. Adding a fourth axis to my mill means more thinking and care are required. I have laid in lots of extra stock for the likely multiple attempts. 🙂