Northern 4-8-4 Build 3/4”

Where users can chronicle their builds. Start one thread and continue to add on to it.

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bushav
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Location: Bainbridge GA

Re: Northern 4-8-4 Build 3/4”

Post by bushav »

Boy o boy. I've got so much learning to do! I started machining the Walschaerts gear today. I started out with some .500 12L14 and by the time I had my first piece milled to thickness I had a bowed piece of steel.

I just received "The Pennsylvania A3 Switcher" book by Kozo. I think I'll do some reading before butchering another piece of steel.

Maybe I'm overthinking some of these pieces. 12L14 is expensive and not readily available in the proper thickness. In reading some of the machinist forums it appears I overlooked the fact that cold rolled steel has internal stresses just waiting to spoil my day.

I was a little productive this week. I made some clamps that will be needed for fixturing.
clamps.jpg
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Building 3/4” 4-8-4 Northern &
1” 4-6-2 Pacific
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Bill Shields
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Re: Northern 4-8-4 Build 3/4”

Post by Bill Shields »

You are learning .. .

I am personally fond of ground to size hot rolled which is available from several vendors.

Tool steel works well also.

12L14 is restricted to screws in my shop. (Round bar and hex)

Cannot say I have ever purchased a piece of it in flat plate form...
Too many things going on to bother listing them.
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bushav
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Re: Northern 4-8-4 Build 3/4”

Post by bushav »

I picked up some hot rolled 1" x .250 this afternoon. I'm going to experiment with it tomorrow and see if I can clean it up by the time it reaches .1875. I am attempting to make the end plate (end plate mount) where the expansion link rotates. The inner plates are already soldered onto the crosshead guide support and chassis. The four tapped holes are just waiting for the outer plate and this looks like a good place to start. The only difficulty will be perfectly locating the pretapped holes and the expansion link pivot point as this part of the engine doesn't follow the plan's dimensions (since its a 4-8-4 vs 4-6-4). Once I get a plate properly dimensioned I think I am going to make some pointed studs to screw into the four mounting holes and rap on the plate while held in place thereby making tiny indentions to locate the mounting screws. At least that will be my "first" attempt.

It's fun learning. I think my progress will pick up pace once I do a few pieces. At least that is how my rib stitching goes when I first start recovering an aircraft. The project tends to pick up the pace as the muscles start communicating with the brain.
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Building 3/4” 4-8-4 Northern &
1” 4-6-2 Pacific
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NP317
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Re: Northern 4-8-4 Build 3/4”

Post by NP317 »

I recommend using Transfer Screws:
https://www.mcmaster.com/transfer-screws/
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Berkman
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Re: Northern 4-8-4 Build 3/4”

Post by Berkman »

wow do they have transfer screws in npt pipe sizes? that would make locating holes on the jacket a lot easier too.
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Bill Shields
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Re: Northern 4-8-4 Build 3/4”

Post by Bill Shields »

Make them.

Take a pipe nipple, cut it short and press in a a transfer pin

After all ..the id of the pipe is cylindrical
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Harold_V
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Re: Northern 4-8-4 Build 3/4”

Post by Harold_V »

bushav wrote: Wed Oct 26, 2022 4:56 pm it appears I overlooked the fact that cold rolled steel has internal stresses just waiting to spoil my day.
While what you said is true, it's also true of all materials. Stresses are a fact and must be properly addressed. Cold worked materials tend to be worse, but even hot rolled materials have stresses.

Pretty much any time you remove more material from one side than you do the opposite side, you can expect the material to bow. You can address this issue by roughing all features before taking any finish cuts. That way the stresses are relieved, with the finish cuts taking the part to size after it has moved. It stands to reason that roughing cuts should be substantial---leaving behind only enough material for the part to clean up when it is taken to size. Rule of thumb is to leave between .030"/.050", with the lowest amount being desirable.

When you reduce stock thickness, you can control movement by taking small amounts off each side, alternately. Take a cut, flip the part, take another cut, flip the part, and so on. It takes more time, but it offers the results you seek. That applies when milling as well as grinding.

Round (lathe) work when accomplished on center does this automatically. If, however, the work is eccentric, you may experience some unwanted movement.

Working between centers (as opposed to holding in a chuck) also is self-correcting, assuming you leave material for a finish pass.

H
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Harold_V
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Re: Northern 4-8-4 Build 3/4”

Post by Harold_V »

Bill Shields wrote: Thu Oct 27, 2022 6:27 am Make them.

Take a pipe nipple, cut it short and press in a a transfer pin

After all ..the id of the pipe is cylindrical
Well, yeah, sorta. Pipe is generally welded, so the bore isn't really round. Also, the thread may or may not be concentric with the bore (and often is not).

H
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Bill Shields
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Re: Northern 4-8-4 Build 3/4”

Post by Bill Shields »

The small diameter brass pipe I use in model building appears to be DOM

At worst case ..chuck it up and shove a boring bar into it
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bushav
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Re: Northern 4-8-4 Build 3/4”

Post by bushav »

Thanks for the advice guys. Keep it coming. I made progress today. I fabricated some threaded pins to locate my four mounting holes. This worked as expected and amazingly the mounting pattern works on both sides, even with very tight tolerances for the mounting screws.

The hot rolled flat bar machined easily and held its shape. Cheaper, readily available and works. I’m sold!

However, my 5/16-24 bolt/pin didn’t locate the pivot boss very well. I should have known that threads aren’t good at maintaining concentricity. The pin located the opposite 1/2” hole forward of where it should actually be by about 1/8”.

I’ll be at work the next four days. That will give me a chance to develop a better plan. At least I’ve got a good pattern for the mounting screws.

I’ll get pics for you guys next week. I didn’t have my IPad with me today.

I took this one with my phone. Orientation is wrong but not annoyingly so.
Pivot boss locating pin (no good)
Pivot boss locating pin (no good)
New to live steam
Building 3/4” 4-8-4 Northern &
1” 4-6-2 Pacific
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bushav
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Re: Northern 4-8-4 Build 3/4”

Post by bushav »

Success!

End plates turned out great. I ended up unsoldering previous owner’s bushings on the inner plates. They were out of alignment and causing me great grief. First time silver soldering. No problem! I aligned all four bushings with some drill rod while soldering.
Aligning bushings with drill rod before soldering
Aligning bushings with drill rod before soldering
End plates completed
End plates completed
New to live steam
Building 3/4” 4-8-4 Northern &
1” 4-6-2 Pacific
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bushav
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Joined: Wed Aug 24, 2022 2:23 pm
Location: Bainbridge GA

Re: Northern 4-8-4 Build 3/4”

Post by bushav »

Machined the blanks for the link rocker assemblies today. Also started setting up my Phase 2 rotary table for this task. I have never used the rotary table so I had some issues. Disassembled and freed up eccentric and verneer scale and ordered the small t bolts I need for clamping. I know I could have made some but dang the time gets away from me. Headed to work for 4 days so I took the short cut and just ordered some.

The rotary table picture is just me working out a plan. I’m going to cut a base plate which will be sacrificial and I I’m just gauging how it will all work to hold the pieces and sweep the arcs.
Rocker assembly blanks
Rocker assembly blanks
Setting up rotary table for first time
Setting up rotary table for first time
New to live steam
Building 3/4” 4-8-4 Northern &
1” 4-6-2 Pacific
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