Pennsylvania A3 Switcher (Kozo)

[Roger B]

Kozo certainly gives you some fun fabrications    Coming along nicely   

[Kim]

He certainly does! 

Kim

[Kim]

Chapter 32.3 – Cab Front

The Cab Front may not look like much, but there are a LOT of little details.  I spent many hours making my working drawings with coordinates from my chosen reference.  And that involved understanding how everything fits together, which took me some time.  I also came up with another anomaly in one of Kozo’s drawings which added to that time.

In Figure 32-7 of the Cab Front, the height of the door is given as 3 7/16” (circled in red).  However, if you compare that distance with the dimensions shown on the opposite side that define the location of the 3/16" tall notch that it lines up with, the bottom of the door would be 1/8" higher that is shown here.  Checking all the other drawings and photos showing the front of the cab with the door, it’s clear that it’s supposed to be where he has it drawn.  I eventually concluded that the height of the door should be 3 9/16” rather than what is shown in the drawing.  I’m going to proceed with that anyway. And if I come up with a problem, I’ll revise at the time.  But it really looks like that number is 1/8” off from what it was intended to be.


I was able to square up the cab front sheet using my mill vise, which was really nice, because I'd just spent a bunch of time setting it up on the mill bed.  I had to remove one of the jaws from it to get the sheet to fit long ways, but it did fit – just barely.  And my Y travel was just enough to cover the needed length. Yay.  Here I’ve made one side flat and using it as my reference against the vise jaw (the removed vice jaw).  The side being held by the movable jaw isn’t square or even.  So I used a piece of copper wire between it and the vice jaw to allow it to be held securely even though the side isn’t even.  It may not make quite as secure of a grip, but it kept the sheet square with the reference jaw, and I took light enough cuts that this wasn’t a problem.


With the cab front sheet squared up and trimmed to final size, I then marked out the major features.  My Dykem layout fluid is apparently too old to work well.  I did clean the surface of my metal, but the small amount of fluid left in the bottom bottle is very runny, doesn’t go on well, and doesn’t cover evenly like it should.  I think it’s time to break down and buy a new bottle.  After 15+ years, that’s probably reasonable.    Anyway, I think I made it work this time.  You can see the cutout for the boiler there and rectangles where the doors and windows will be.


To make the curve along the top I just lined the roof up where it will meet with the cab front and traced the inside shape with the scribe.


Then I cut the sheet for the doors and windows.  These were cut from 0.040” thick steel sheet (also 4130a).


Next, I’ll square up and trim the doors & windows to size, then solder them all together before final shaping.  I want to leave the part square as long as possible. Once I put that curve on the top it will become much harder to hold.  I’m also thinking I’ll probably just freehand the curve for the boiler. I was considering using the rotary table, but in the end, the final shaping will be done with files to fit any irregularities on the boiler. So it doesn’t seem worth the setup time to get the nice semicircle, only to mess it up by filing it by hand later, you know?  Time will tell. Guess we’ll see what happens!

Kim

[crueby]

Lots of details in that wall!  I like the idea of the copper wire, hadn't thought of that before.   

[Kim]

Yeah, lots of detail!  It takes some time to get all in there, but the parts Kozo has you make sure come out looking good in the end 

The copper wire trick isn't original with me.  I know I've seen it in other places.  I think I may have picked that one up from Blondihacks, but I'm sure I've seen it other places too.  The soft copper wire mushes some around the spot you're clamping and gives you better contact than a hard surface would in these cases.  It works surprisingly well!

Kim

[uuu]

The top of the door does seem to line up with the notch - but the bottom looks a tiny bit above the #37 hole, so you could make it a touch less than 3 9/16" perhaps.

Wilf

[Kim]

The top of the door does seem to line up with the notch - but the bottom looks a tiny bit above the #37 hole, so you could make it a touch less than 3 9/16" perhaps.

Wilf

This is true, Wilf, and I considered that.
But the bottom of the doors line up exactly with the 3/8" mark for the center of the boiler cut out.  What's weird, is that his 3/8" for the boiler center and the 3/8" for the #37 screw holes don't line up.  So I chalked it up to him doing all his drawings by hand.  Or maybe he was showing that the holes are independent of the boiler center mark and the doors, even though they are shown with the same dimension.  I don't know.  Or maybe he felt that the counter sunk screw holes might interfere with the edge of the door, so he showed them a titch lower to keep them from interfering?  But if that's the case, why didn't he make them a 5/16" or 11/32" or something?  I likely will never know!

Kim

[MMan]

Hi Kim,

Enjoying this build immensely, if quietly.

For your boiler cutout consider using a hole saw (probably bi-metal for steel) - they are cheap and low on drama if all you want is to remove most of the material and file from there.

All the best,

Martin

[Kim]

Hi Kim,

Enjoying this build immensely, if quietly.

For your boiler cutout consider using a hole saw (probably bi-metal for steel) - they are cheap and low on drama if all you want is to remove most of the material and file from there.

All the best,

Martin

Thanks Martin! 

Interesting idea with the hole saw...  It's just enough over a half circle to fit the drill at the center of a hole saw.  But how well does that work to cut a hole where only 60% of it is there?  Would that work OK or cause weird problems with the hole saw?  I've never tried it on a partial hole like that before.

Kim

[crueby]

Hi Kim,

Enjoying this build immensely, if quietly.

For your boiler cutout consider using a hole saw (probably bi-metal for steel) - they are cheap and low on drama if all you want is to remove most of the material and file from there.

All the best,

Martin

Thanks Martin! 

Interesting idea with the hole saw...  It's just enough over a half circle to fit the drill at the center of a hole saw.  But how well does that work to cut a hole where only 60% of it is there?  Would that work OK or cause weird problems with the hole saw?  I've never tried it on a partial hole like that before.

Kim

When over a partial piece, or anytime with thin sheet, clamp the piece between two sheets of plywood to hold it in place and keep it flat. Make the bottom piece of wood thick enough for the  pilot drill of the hole saw to stay in the wood till the saw is done cutting.

[Kim]

Ah... good advice, Chris!

I checked when I was out in the shop earlier, and I don't have a hole saw anywhere near the correct size.  I do, however, have a fly cutter circle cutter. I've used that many times to make round holes - in both wood and metal.  But I don't know how well it would react to the interrupted cut of a non-full circle in the steel.  Hmm... feels a little iffy.  I'll have to think about that.  Might just end up cutting it out on the jigsaw.

Kim

[Kim]

Today I made the cab front windows and doors.

I’d already cut the blanks last time (from 0.040” steel sheet).  So today, I squared them up and cut them to size.  Since there are two of each, I double-sticky taped the parts together for the job.

For the doors, there is a window and a panel cutout in each one.  The windows will be cut later after the doors are soldered to the cab front.  But the panel just provides a nice detail for the door, it doesn’t go all the way through the cab, just the ‘door’ piece.  So I marked the four corners of the panel with a 1/8” drill:


Then cut the panel out with a 1/8” end mill. I also drilled a couple of holes for solder hold-down screws in the upper part of the door.  These screws are positioned inside the window cutout.  So they’ll be removed when I cut the hole for the window later.  Here I’ve cut three of the four sides of the panel opening.


Then I did the same thing for the windows (minus the panel cutout).  And here are all four of the pieces that will be soldered onto the cab front.


Next, I’ll drill the solder screw holes in the cab front and solder all the parts together.

Kim

[crueby]

Ah... good advice, Chris!

I checked when I was out in the shop earlier, and I don't have a hole saw anywhere near the correct size.  I do, however, have a fly cutter circle cutter. I've used that many times to make round holes - in both wood and metal.  But I don't know how well it would react to the interrupted cut of a non-full circle in the steel.  Hmm... feels a little iffy.  I'll have to think about that.  Might just end up cutting it out on the jigsaw.

Kim

Yeah, I  agree on an interrupted  cut that large a diameter!

[cnr6400]

  Re the method for the big hole to be cut - I'd go with the jigsaw myself, or chain drilling / belt sander method. These will have a lot less drama (and less un-intended rapid energy transfer to the user's limbs and person) than hole saws - hole saws in sheet steel with interrupted cut makes me nervous, based on several awful attempts with bad results. (thankfully no ambulance rides either). I really like fly cutting too, with one exception - trepanning holes in sheet steel! Again, had some less than fun experiences.  Good luck with the big hole excavation!  PS if you know anyone with a plasma cutter, CNC sheetmetal shop, or laser metal cutting service, these methods are much better and safer in the long run for making big holes in thin steel sheet.

[Kim]

Thanks Chris and Jeff,  Good advice, all the way around! 

Kim