The Home Machinist!

During the construction of the pilot for my 1.6" scale NYC & HR 999 project I was faced with how to effectively generate the helical face of the staves.

The attached top view photo of the pilot of my Disney 4-4-0 shows a typical 1800s pilot with the helical face of the staves. The faces of top of the staves are parallel with the front face of the pilot beam while the bottom of the stave face is parallel with the front edge of the lower frame. The top and bottom faces are connected by a form of a helix having straight edges on the inner and outer faces. It can be seen that the staves are handed to the right and left sides of the pilot. Because each stave per side is a different length the angle it intersects the lower frame is different.

Prototype 1800s pilots were made of wood. The pattern maker or carpenter who built them could scribe a straight line for the inner and outer edges then with a plane or draw knife shape the helix. However, the pilot staves were made of hard wood, usually oak, and 2" to 2 1/2" wide. So it must have been a tough job. Maybe the locomotive builders had some sort of machine to make the staves.

Since the frame of my pilot is steel and the staves aluminum I had to come with an alternative method. One alternative would be to rough mill than file and sand to shape, although a lot of hand work. I decided to machine the helix.

I decided the way to go was helical milling. Helical milling is described in detail in the Machinery's Handbook. Basically the process is to connect the spindle of a dividing head to the miller table lead screw with a set of gears so that the part rotates the proper number of degrees for the number of rotations of the lead screw corresponding with the length of the helix.

The 1st attached photo shows my set up. An equal number of teeth gear pairs were mounted on the lead screw and the dividing head spindle to make up the center distance for the change gears available. The four gears in the center (one is hidden) are the required compound gear set. I.E.: (lead of the helix to be cut/lead of machine) X (product of the driven gears/product of the driving gears)

The 2nd attached photo shows my fixture with a stave mounted on it. The fixture is vertical and the cutter is over the top end of the stave. As the cutter enters the stave the start of the cut will be parallel to the front face of the pilot beam. Note that at other end of the stave the scribe line on the face of the end. The scribe line is the angle of the helix and is flush with the pilot bottom frame front face.

Originally the face of the fixture that the stave is clamped to was on the dividing head center line. However, this created an arch of about .030" on the outer edge of the milled helix. I added an adjustable center pivoting on a 1/4" dowel on each end. By moving the height of the centers relative to the original position I found that set to the center of the stave thickness created an arch of equal height on the inside and outside of the stave of .010" to .015" and not noticeable when assembled into the pilot.

The 3rd attached photo shows the cutter at the end of the cut and bottom of the stave. The fixture has rotated through it'd required number of degrees to generate the helix. The scribe line on the bottom of the stave is now horizontal.

The attached photo shows the finished results on the pilot left side staves. The stave ends are flush with the pilot beam and bottom frame faces with a helix connecting them. The fit and finish are acceptable so I'm satisfied. Now I have to do the right side staves.

Merry Christmas and Happy New Year, Dave

Lovely work.

I suspect that the prototype wooden staves were shaped into the proper helix by steaming and clamping.

Nice work. My Railroad Supply Corporation CP-173 has a pilot fabricated from 1/4" aluminum with lots of filing and sanding to get the form right.

Could you post a couple more photos of the coupler? Is it made to the Disney drawings? If so, I can dig through the Disney drawing set that I have. I have a drawbar, but it's not very practical.

Two wooden pilots are shown in Modern Locomotive Construction, circa 1892. Neither shows a twist in the staves.

It's available at https://ia802704.us.archive.org/20/item ... yerich.pdf

...aw shucks. After machining helical pilot staves, the rest of the loco ought to be a "piece of cake"! What other neat machining processes have you got up your sleeve(s)? After all...sometimes we find the journey more interesting and fun than the destination! Looks great! Carl B.

Dick_Morris wrote:Nice work. My Railroad Supply Corporation CP-173 has a pilot fabricated from 1/4" aluminum with lots of filing and sanding to get the form right.

Could you post a couple more photos of the coupler? Is it made to the Disney drawings? If so, I can dig through the Disney drawing set that I have. I have a drawbar, but it's not very practical.

Two wooden pilots are shown in Modern Locomotive Construction, circa 1892. Neither shows a twist in the staves.

It's available at https://ia802704.us.archive.org/20/item ... yerich.pdf

I have the same book. It was actually one of my references. The staves are not twisted. The back and two sides are parallel just like rectangular bar. It is just the front face that has the helix shape. Look again at the 1892 book. The top view shows the stave sides as straight and parallel, but at the bottom angled to match the angle of the frame front edge. Then scan downward to the side view. You'll see two lines for each stave. The lines are spread at the bottom to match the lower frame angle as seen in the top view. Follow the same two lines to the top and you see they converge to a point. What your looking at is the side view of the helix. Stare at it for a while and you'll see it.

I'll take a couple more photos of the Disney coupler for you. Any particular view you need? I'll also check my Disney drawings to confirm what is there matches the drawings.

Side and front view would be helpful.

The two or three prototypes photos I have found that show conversion of the front draw bar to a coupler on with a long pilot show diagonal braces from the corner of the pilot beam to somewhere around the front of the coupler mount. That looked like a good idea. I didn't have any luck finding the photo today.

I made an index of the Disney drawings long ago. I forgot I had it. Send me your email via PM if you want a copy. The "automatic coupler mount" is on the sheet with the pilot.

I gotta say - that mill is a thing of beauty as well.

Dick_Morris wrote:Side and front view would be helpful.

The two or three prototypes photos I have found that show conversion of the front draw bar to a coupler on with a long pilot show diagonal braces from the corner of the pilot beam to somewhere around the front of the coupler mount. That looked like a good idea. I didn't have any luck finding the photo today.

I made an index of the Disney drawings long ago. I forgot I had it. Send me your email via PM if you want a copy. The "automatic coupler mount" is on the sheet with the pilot.

The Disney pilot drawing is No. 37. On the drawing is part No. 3 "Automatic Coupler Mount" and part No. 6 "Pilot Draw Bar Pocket". I could not find a drawing for the coupler. Attached are photos of both side of the coupler and a front view. I hope this is what your looking for. Let me know.

wewilliams wrote:I gotta say - that mill is a thing of beauty as well.

Heh! Guess I'm not the only one who thinks so.
Such machines aren't commonly found in the home shop. How nice it would be to have a well tooled #3 universal horizontal mill at my disposal.

H

Thanks, that's what I was looking for.