Pennsylvania A3 Switcher (Kozo)

[Kim]

Thanks, Todd! 
Kim

[Kim]

There are a couple of pairs of holes needed in the cab roof.  One pair is for the cab ventilator unit, and the other is for the prop that will hold open the cab roof so you can more easily work the controls.  To drill these, I used the outside printed form to hold the part level on the mill.  The clamps are actually pressing on the very edge of the roof, rather than the form itself.  This is probably not the most secure setup, but it was plenty good for holding it in place while drilling the holes where all the force is directed downward.


Next, I made the cab edge pieces.  These go along the base roof line of the cab to help stiffen it.  Not sure they correlate to anything on the prototype.  It might represent the gutter above the windows, but it’s hard to tell based on the few pictures I can find.

These pieces were (previously) cut out from the same 1/16” sheet steel as the roof.  I double-sticky taped them together, trimmed them to size, and then drilled a couple of holes for some #1 screws for holding the part during soldering, and one 3/32” hole for the pin that the cab roof will hinge on.


Now, to make the corresponding holes in the roof I had initially thought I’d hold it using the inside and outside forms like this, then drill the holes through the top of the form.  However, this setup was just a bit too squirrely.  The top edge of the roof was not straight with the x-axis.  There was about 30 thou of difference between one end of the roof and the other.  And when the part you’re holding on is only 3/16” wide, that’s a pretty big error.  That didn’t make me happy. With a little more investigation, it seems that the top edge of the roof would twist oddly when I tightened the mill vise.  I believe that the bends in the roof didn't match the form close enough and varying the pressure on the C-clamps or the vise caused the top edge to move quite a lot.  So this setup was clearly a no-go.


I had worried that might be the case, so I’d had the foresight to drill the screw holes in the edge pieces to tapping size (as opposed to through size).  This way I could use the edge pieces as a guide for drilling the roof.  I used my corded drill for this since it has a much higher RMP than my battery drill.  This worked quite well.


Then I made a pair of roof hinge pins from stainless steel round bar.


After tapping the screw holes in the roof, and opening out the holes in the edge pieces to #1 through size, I was able to assemble it and see how it looked. The pins are set right by where they want to go.


I disassembled everything and gave it a good cleaning. Then applied some flux and little pieces of solder along the joint:


Then proceeded to heat it up from the underside with the torch.


This went much faster than silver soldering, but the solder doesn’t wick nearly as well.  I used a pointy solder stick to move the solder around quite a bit. The long joint worked out quite well. But the stainless steel pins didn’t solder at all.

I cleaned it up and re-soldered the pins in place. It seemed to work fine the second time around.  Wonder if it’s because I used stainless for the pins?  Anyway, got it to work eventually.  Kozo says to make them a press fit or to use Loctite to hold them on.  But I’m not sure Loctite would make it through the powder coating oven.  I know that soft soder will survive because I’ve done that before!

All in all, it came out pretty well.


Next up will be the ventilator for the top of the cab.

Kim

[crueby]

Yeah, soft solder doesn't work well at all on stainless. Silver solder does, but on a thin piece like that you'd be risking warping the room. If the roof was brass or copper then soft solder would stick fine. I'm surprised that Kozo didn't specify riveting them in place, he uses rivets in lots of places on the cabs on his other models. I've found that if you use a countersink cutter (like for wood screw heads) on the edges of the holes, you can give room for the rivets to expand into without sticking up so far, enough that you can file them off flush but still have them hold in that beveled area.
 

[Kim]

Yeah, soft solder doesn't work well at all on stainless. Silver solder does, but on a thin piece like that you'd be risking warping the room.

Yeah, that certainly matches my experience here.  I looked it up on the all-knowing internet and seemed to come up with the answer that you could solder stainless.  But like you said, it doesn't seem to work super well.

Yeah, I'm sure that's why Kozo specified soft solder here, not silver solder.

If the roof was brass or copper then soft solder would stick fine. I'm surprised that Kozo didn't specify riveting them in place, he uses rivets in lots of places on the cabs on his other models. I've found that if you use a countersink cutter (like for wood screw heads) on the edges of the holes, you can give room for the rivets to expand into without sticking up so far, enough that you can file them off flush but still have them hold in that beveled area.
 

Interesting idea.  I'll probably stick with the solder method for the cab, but we'll see how it goes.  the countersunk rivet idea is a good one!

Kim

[cnr6400]

 

[uuu]

I have had success silver soldering sheet stainless steel, but using an appropriate flux, Tenacity No 5.  I think it's more aggressive than the normal brew and lasts longer - but it needs a caustic pickle to clean up.

Ashpan2 by Wilf, on Flickr

Wilf

[crueby]

Yes - I use high temp silver solder on stainless all the time, its the low temp soft solders that dont work well on stainless. The Tenacity 5 is great, as is the Harris Black flux which is also longer lasting.

[Dave Otto]

Hi Kim

Are you using the Harris Say Brite Tin/Silver solder?
They recommend using the Say Clean liquid flux with steel and stainless steel because it has better oxide removal. Also did you thoroughly clean both parts before assembly? I'm sure that you did but just thought that I would ask.
It also appears that for the color of the steel your heat may be been a little to high.
https://ch-delivery.lincolnelectric.com/api/public/content/9d74aee959c14d75b5b4354bed373479?v=2944ecaf

Just some thoughts,
Dave

[Kim]

Yes, I'm using Sta Brite solder and Sta Brite flux. However, the flux I have is paste flux.  I may have a little bottle of the liquid Sta Brite, I'll have to check. But that's not what I used.  I did clean the parts but I probably could have done a better job. That may be part of the problem (at least the second time).

Good point on the heat, Dave.  I definitely think you're right that I was using too much heat.  I should have stepped down on the size of burner I was using.  It didn't take long for the solder to melt.  I wanted to make sure and get things hot all the way through, but I'd probably have had better control and kept the whole thing a little cooler if I used a smaller burner on the Seivert.

Kim

[Don1966]

Kim I been absent for a while life and knee joint replacement. I just finish catching up on your remarkable project. Very intuitive work and your skills are remarkable. Did I say I ………….like…………..


 
Don

[Kim]

Thanks Don!

Hope you're new knee is doing well and that you're able to get out and about and do things.

Kim

[Kim]

Chapter 32.2 – Ventilator

Before I started on the Ventilator, I had to take care of a couple of things on the roof that I hadn’t finished up yesterday – I had to file off the heads of the screws that were used to hold things in place for soldering.


And I needed to file off the excess length of the roof edge pieces.  I started with the file, but being a lazy person by nature, I moved to the belt sander rather quickly.  This picture was taken just before I moved to the belt sander


With that done, I started on the ventilator.  This is not a working vent, it's just for looks.  It is made from two pieces of 1/8” x 1 1/4” CRS bar.  The first one is the base which was trimmed a bit with a shallow channel taken out to make it sit level on the slight curve of the roof.


The second part is a little bigger than the base but has no interesting feature other than the countersunk attachment holes.  Here are the two parts of the ventilator.  The base is on the left and is upside down in this picture.


And here’s the roof, complete with ventilator.


Next will be the cab front.

Kim

[cnr6400]

 

[crueby]

Great progress on the cab!   

[Kim]

Thanks Jeff and Chris! 
Kim