Steam Loco Spoked Wheel Making

[mmagliaro]

I thought it better to open this as a separate topic.

I had pretty good success with the first part of this side project: making the brass flanged tires
that will go over the spoked wheel centers.  ( I say "side project" because this was a detour from my NP 2-8-2
project, which I will be getting back to shortly).

Photos are below, along with a link to video at the end.

I bought some 3/8" thick-walled brass tubing (.049" wall) online.  K&S doesn't quite make enough sizes and thicknesses
for this project, so I had to go searching.  There are industrial metal suppliers that have a wider variety
of metal tubing.  I got mine from onlinemetals.com  It is 0.375" OD (3/8")  with an inner diameter of 0.277"

Running a length of this stuff in the mill, with a good Starrett gauge against it, I was pleasantly surprised to
fine that the total run-out error (which includes the tubing itself and whatever error is in my lowly Micromark mill),
was far less than .001".  It was only about .0003"  (3 "tenths"). 

The target diameter is a 51" driver, so I settled on 0.320" (51.2")   With this tubing, that gives me plenty for a flange,
and leaves a tire thickness of  (.320 - .277)/2 = .022"  That's also a happy number because it allows cutting
a .010" deep groove for a traction tire, and I will still have .012" of metal left.

The following documents the process and results, including some video. 

I won't kid you.  I tossed out 5 or 6 of these before I got "in the zone" and figured out just how to set up the
workpiece and the cutter in the mill.  But once I got it, I turned out a bunch of them and the dimensions are really really close, as in under +/- .001" on things like tread diameter, flange depth, wheel thickness, etc.

I was able to make cutting tools from tool blanks that formed a nice tread and flange in one smooth step,
as well as parting off the finished wheel while cutting the tapered back of the flange in one step.
A little rubbing/polishing the cut wheel on some 800 grit sandpaper was the only clean-up needed after milling.

I may be a total idiot when it comes to milling and machining, and I certainly won't be giving up my day job to
take employment as a machinist any time soon.  But at least I got decent tires.

As delicate as this was, this is still the "easy" part.  Making the spokes and hub that go inside it will be
the big hill to climb.

One big side benefit of this is that now I can turn replacement driver tires to do things like
putting a traction tire onto an engine that has no grooves.

















Video:  It's nothing spectacular.  It just shows me turning one of these.  But it's almost impossible to ever
find video of how to mill small parts for N Scale, or even how these things work in a mill,
so I thought it might be helpful.
https://www.youtube.com/watch?v=3LUdOg9TzxA

[Scottl]

I love this thread already.  Milling has been somewhat of a mystery for me, and I can see you have a lot of knowledge to share.  Thanks!

[Iain]

Are you going to nickle silver plate the tires?

[randgust]

Max....

Aside from large piles of envy with your tooling collection.. one thing did occur to me.   

K&S at least, is relatively 'soft' material.   Did you have to deliberately choose a harder material for this, or was is purely enough to just find the right dimensional stock?

It would just really be awful to get through all this and build it and find the flanges wearing off!     I've only ever seen 'terminal' flange wear in HO.

[mmagliaro]

Randy,

I don't think I had much of a choice, but it is 260 brass. 

I believe K&S is 260.

Whether it isn't hard enough, I do not know.  Hopefully somebody on the forum will chime in who knows the
metallurgy better than I.

No, I don't plan on nickel plating these.  I plan to chemically blacken them.  I know there are home do-it-yourself
electroplating kits.  Micromark sells one for about $50 that looks easy to use and would allow me to nickel plate these
wheels.  If anyone has direct personal experience using it, please chime in.  My fear is that the thickness of the plating
layer would not be very controllable, and it might make a mess of things - throwing my wheels out of round by a few thousandths
of an inch (or a lot worse!), which I want to avoid.

============
Scottl:
I have about as close to zero knowledge of machining as you can get while still being brave enough to put
my hands on a milling machine.  But I'll learn.

These mini mills are not the greatest for super-precise control of the head and X-Y table.  I have the
guides adjusted so there isn't any rocking or wobbling in the motion, but there is still some annoying backlash in
all the X, Y, Z gearing mechanisms, so you have to really watch out for it.  Just get the table moving in one direction to
take up the lash, and then you're okay.

The important things, however, like stability and the darn thing turning true, are there.  I was shocked at how good
the run-out was on this mill, especially using a chuck.  I expected the collet holder to do much better but it does not,
so it must not be a very good one (I bought it when I bought the mill).   But if I can chuck something in
the mill and turn it within .0002", that's good enough for me.  It's better than I am at being a machinist.

[randgust]

I'm not a metallurgist either, but my previous employers insist I attempt to become one - first in carbon and stainless steel and then in brass, including taking the American Society of Metallurgist courses (crankshafts and radiators).  So I know stuff I'd just as soon forget.   It's one of the reasons I'm such a nutbag about wheel composition and the impact on tractive effort in N.  With a 260 brass wheel, Max, here's some thoughts:

1)  I don't think you'll need to put on traction tires, you'll probably get 18-20% adhesion just on the brass alone against nickel silver rail.
2)  Work to slightly thicker tolerances on the flange width if you can get away with it to allow for some eventual wear.
3)  Blackening 'may' compromise electrical pickup, but it will wear off soon enough.

260 is basically cartridge brass, and the time-honored way to mess with its structure (deliberately or accidentally) is work-hardening.   You can anneal it to make it more ductile, but you can't heat treat it. 
http://metalshopborealis.ca/pics5/brassprop.jpg

If you've ever cut a piece of K&S copper tubing with a Zona saw (or bigger stuff with a hacksaw) you can literally feel the work-hardened zone on the metal outside surface, as once you get through it, it's noticeably softer and easier to cut.   

 Many of the 'brass' wheels out there are more on the phosphor bronze alloy side, which is a LOT harder than 260.  I'm convinced that Atlas is using a very, very hard wheel, which makes it slipperier.

Depending on how you are cutting it (which really is a machinist, and I'm not one!) you may be work-hardening it during the cutting process and not even realizing it, or it may be near 'raw' and be much softer.   I usually don't notice if something is noticeably work-hardened until I try to cut it with hand tools.





 

[peteski]

I love this thread already.  Milling has been somewhat of a mystery for me, and I can see you have a lot of knowledge to share.  Thanks!

Scott,
if you looking here to learn milling, then this is not where you will learn that (at least not now).  Max is creatively using his mill as a lathe to turn (not mill) the wheel tires. 

Nice writeup Max.  I used to do the opposite. With an aid of a vertical column attachment I used to turn my Sherline lathe into a ... mill! 

[Scottl]

Now I know that turning and milling are different.  That would be about doubling my knowledge of both subjects. 

[randgust]

Max, as long as you're doing all the actual work and I can just type.... here's a thought.

Shapeways offers printing in metal, but the fine detail isn't there.    But this is nearly jewelry, at least for the wheel centers.   

Assuming you can still put a hole in the center for an axle, and chuck it in that way to machine the outer surface to dimension... would the spoke wheel detail be good enough?   Strong enough?    I've never heard of ANYBODY attempting this or anything like it, but the alternative of a FUD-printed center, or individually-cut spokes seems rather daunting.  Home delrin-casting seems a bit farfetched.   Finish-maching a Shapeways printed metal wheel center for a tire?    I suppose you could even machine it and put in an insulating gap like Mantua used to do in HO.   Maybe.  Or not.....!

Or you could be like Atlas on the 4-4-0 and just print a picture of spokes in low relief.... that should work in anything harder than Evergreen styrene   .

[mmagliaro]

Scott,
if you looking here to learn milling, then this is not where you will learn that (at least not now).  Max is creatively using his mill as a lathe to turn (not mill) the wheel tires. 

Nice writeup Max.  I used to do the opposite. With an aid of a vertical column attachment I used to turn my Sherline lathe into a ... mill! 

That is exactly right.  I don't own a lathe, and don't plan to buy one.  But for very short stock (i.e. that brass tube is only sticking out of the mill chuck about 1/2"), you can turn things in a mill and get darn true turnings, because there's no deflection
on a length that short.

Randy,
My flanges are .024", which is .002" over NMRA spec, and they can wear quite a lot before there would be trouble.
For example, Fox Valley wheelsets have .015" flanges.  Something else you'll note.  My wheel tires are .022" thick.
So they can wear down an awful lot before there's trouble.  True, the flanges would start getting deeper if the treads
ever wear, but then, you can always flip the engine on its back and skim a little off the flanges if you have to.

All of this, I think, is only a consideration if I were going to run this engine under conditions like a department store
where it runs 8 hrs a day every day.  I cannot imagine these brass wheels or flanges wearing out, or even wearing
noticeably, after just a few hundred hours of run time, which is likely all they will ever see in my lifetime.

[mmagliaro]

Max, as long as you're doing all the actual work and I can just type.... here's a thought.

Shapeways offers printing in metal, but the fine detail isn't there.    But this is nearly jewelry, at least for the wheel centers.   

Assuming you can still put a hole in the center for an axle, and chuck it in that way to machine the outer surface to dimension... would the spoke wheel detail be good enough?   Strong enough?    I've never heard of ANYBODY attempting this or anything like it, but the alternative of a FUD-printed center, or individually-cut spokes seems rather daunting.  Home delrin-casting seems a bit farfetched.   Finish-maching a Shapeways printed metal wheel center for a tire?    I suppose you could even machine it and put in an insulating gap like Mantua used to do in HO.   Maybe.  Or not.....!

Or you could be like Atlas on the 4-4-0 and just print a picture of spokes in low relief.... that should work in anything harder than Evergreen styrene   .

There are a few guys on the web who have used CNC machines to cut out spoked wheel centers in N Scale and the results are fantastic.  But then... they have CNC machines and I do not, nor am I willing to make a CAD drawing and farm it out
for somebody else to do.   The point here is to do this myself.

Nothing I've seen come out of Shapeways yet is smooth enough or good enough that I would want to use it for a locomotive.
And besides, that would again be giving the hard job to somebody else to do, which I don't want to do.

Right now, my plan is still to work out a scheme using boring, turning, and a good dial indicator to:

1. Make a perfectly bored, true, brass hub, bored out for 1.5mm (the axle)
2. Make a jig where I can place the hub inside one of my wheel tires, perfectly located concentrically
3. Run strips of brass stock through the mill to taper one edge
4. Cut spokes from that strip and solder them in between the hub and the wheel tire.

I think I can turn down a piece of brass rod so that it just fits inside one of my wheels, and then
mill away sections of it, so that it is just a cross-shaped "insert" with a hole in the center of it,
and use that to exactly locate the hub within the tire.

Locating and soldering the spokes is not as hard as it sounds.   I can draw the spoke pattern in a computer and place it under
the wheel/hub, and just place the spokes over the lines and solder them.  Remember, they don't have to be 100%
exact.  Once the hub is located at the exact center of the wheel tire, that's all that matters.  The spokes
support the wheel, but they are really just for show.

[randgust]

Years ago I had a substantial fleet of Trix units, which were some kind of machined-brass alloy with silver plating on them.    Once the plating wore through, two things happened - the tractive effort went up by about 25%, and the flanges started to visibly wear.   I never got one so worn that I had to take it out of service, but yeah, there sure was wear there on both the flange and tread.   It's measured in lots of time and miles though.

I've got a fleet of HO Mantua GP20's in our office window layout that is on the ground-level street.  It has a button and a two-minute timer on it, and it's basically an on-off switch that gets hit 5-50 times per day.   After the plating wears off, a locomotive is good for about a year and a half before the now-visible brass wheels get 'condemned', it starts to derail, and in one particularly memorable episode, grind the lead wheel flange off and plunge onto the floor with the train.  The first thing, not the last thing, to go, is the wheel flanges.   Not motor brushes, not gears.... flanges, and these are HO scale Pizza Cutters.   The 'fine scale' RP25 flanges go much, much quicker.    It's a folded dogbone with and 18" reverse loop on the top, so it's pretty brutal on wheels.

Max.... read your 'how to' post.   Holy Crap!  The only thing I ever even attempted like that was soldering up an N Shay crankshaft out of individual pieces  before Atlas made theirs.   I did get it made, and to turn, but I've never attempted anything that daunting since.

[mmagliaro]

Years ago I had a substantial fleet of Trix units, which were some kind of machined-brass alloy with silver plating on them.    Once the plating wore through, two things happened - the tractive effort went up by about 25%, and the flanges started to visibly wear.   I never got one so worn that I had to take it out of service, but yeah, there sure was wear there on both the flange and tread.   It's measured in lots of time and miles though.

I've got a fleet of HO Mantua GP20's in our office window layout that is on the ground-level street.  It has a button and a two-minute timer on it, and it's basically an on-off switch that gets hit 5-50 times per day.   After the plating wears off, a locomotive is good for about a year and a half before the now-visible brass wheels get 'condemned', it starts to derail, and in one particularly memorable episode, grind the lead wheel flange off and plunge onto the floor with the train.  The first thing, not the last thing, to go, is the wheel flanges.   Not motor brushes, not gears.... flanges, and these are HO scale Pizza Cutters.   The 'fine scale' RP25 flanges go much, much quicker.    It's a folded dogbone with and 18" reverse loop on the top, so it's pretty brutal on wheels.

Agreed... it would take a LOT of hours to wear down those Trix flanges.  In the HO scale case, I would argue that the forces
on those flanges are a lot more brutal than on an N scale engine.  The weight and forces are a lot more than 2x, so even though those flanges may be physically 2x the size of N Scale, they are subjected to a lot more punishment.
At the low end, 5 times per day x 2 minutes = 10 min/day   x 260 weekdays x 1.5 yrs = 63 hours
At the high end, 50 times per day, = 630 hrs.  Let's call it somewhere in between, say, 300 hrs.
I think it will be good enough.

[randgust]

What kind of soldering equipment are you using?  micro-flame butane torch?  Resistance?   Flux capacitor??? 

I can do precision stuff like wire handrails in my sleep but anything with any heat-sink-transfer nature still makes me crazy.   As long as there is somewhere to hide the crappy soldering (like inside the boiler) or machine it off later I'm OK, but otherwise, not so much.

Now thoroughly dialed into this thread!!

[victor miranda]

I am riveted!