Steam Loco Spoked Wheel Making

[mmagliaro]

Just FYI, scaling off that same HO brass engine, the hub would be about 0.100" in N Scale, with a 1.5mm (.0590") axle.
So a 1/8" brass rod, bored with a #53 bit to .0595, and then turned down to 0.100" should work. 
It has been my experience that boring with a #53, even though it seems like it should be a tad oversized for
1.5mm shafting, is actually not.  We are talking .0005" here, and there is usually some flex in the bored material, even in brass, so that the hole ends up a tad smaller than you expect.    But of course, I will experiment.   

Anyway, 0.100" inch on the hub, with .277 inner diameter on the rim, gets us
(.277 - .1) / 2 = .0885" long spokes.  Isn't that amazing?  Think of what a heavy piece of .080" thick styrene looks like.
The spokes are only about as long as that thing is thick!

[Lemosteam]

Max you could crush brass tubing with a vise to the thickness of the spokes in the side view, cut to length and place them in for soldering.  You could make s small jig with pins sticking up that would represent the space between the spokes to position each spoke  accurately.

[mmagliaro]

Max you could crush brass tubing with a vise to the thickness of the spokes in the side view, cut to length and place them in for soldering.  You could make s small jig with pins sticking up that would represent the space between the spokes to position each spoke  accurately.

The jig with pins would be fine to position them radially around the circle.  In fact, I will probably do something like that.
My problem is how to position the rim itself at exactly the correct position relative to the hub, so that when I solder in
the spokes, the wheel will turn concentrically around the axle.  In other words, I put the hub down on a table.  I press a
steel axle through it.  I place the rim on the table, around it.  How do I get that rim positioned perfectly around
the axle?  (and I mean perfectly as in +/- .001").   The trick is not to focus on the hub itself, or the spokes.  No matter
how perfect those things are made, there is no way I will cut spokes to length within < .001".  And even if I did,
no jig or pins would be good enough to position them so perfectly that the wheel would be exactly concentric around
that axle.   

I'm thinking I need to bore a piece of brass rod with a 1.5mm hole, press an axle into the hole, chuck the axle in the mill,
turn down the rod until it "just" fits inside the tire.  Part off the rod to get just a disk with the axle through it.

Now, put the disk on the table, axle sticking up out of it.  Put the hub on the axle, snap the tire down around the disk,
and I think that should be good enough.  Plus, a little brass disc won't absorb too much heat, so I should still be able to
solder without too much trouble.  The problem is that once the rim is pressed around the disk, there's nowhere
for the spokes to actually go!  So I will have to make the disc a little thick, and face-mill away chunks of it until
it's a disk with 4 legs sticking up at the edges.  Now the tire can be pressed down around those 4 legs, which should center
it well, but the interior of the tire will all be open, so I can put in the spokes and solder them (anywhere there isn't a leg).
Once I get 4 or so soldered in, pull the thing off the form and glue in the rest of the spokes.

down around

[Lemosteam]

Max, I do not have my normal computer tools available to me right now, but I have an idea that will solve all of this, as far as a fixture goes.

[mmagliaro]

Max, I do not have my normal computer tools available to me right now, but I have an idea that will solve all of this, as far as a fixture goes.

Well?
...

WELL???   

[mmagliaro]

I have questions about milling speeds.
I am actually cutting this tube as though I were working on a lathe, as Peteski pointed out, so let's calculate
this based on lathe formulas.

I have stock that is 0.375" in diameter.  So one rotation = 1.178" , or .098 feet, of linear distance.
The material is "yellow brass" for lack of a more precise term.  I found recommendations for turning that metal
to be about 300 sfpm  (surface feet per minute) when using high speed steel cutters (as opposed to carbide).

If you calculate the RPM for that,
300 / .098 = about 3000 RPM.

Here's the thing.  I am not running this spindle anywhere near that fast.  In fact, it can't even go that fast.
I am running it at the lower end of the 0-1100 rpm range, so it is probably running at about 300 rpm, tops.

In fact, for some of the delicate spots, I run that cutter so it's turning very slow indeed. 

This provides excellent control, minimal heat, and the metal just peels off clean and neat with no trouble.
If I crank it up to, say, 700-800 rpm, all that does is make lots of heat, and the metal does not cut nearly as well.
(hot enough that the lubricating oil starts smoking!)

So...
What's going on here?   Is there something in the formulas that I'm overlooking?  I can't argue with the results.
Very low speeds are working great.  High speeds do not.

[haasmarc]

Max,

Can't you do as you suggest with boring for the axle in a brass rod but make it larger in diameter than the tire.  Part off a thickness of the rod, say 1/8th".  Then insert the axle and chuck the assembly in the mill/lathe and machine a recess into the rod that the tire rim, not including the flange, just fits into.  Now you can have the axle sticking up through the recess, put the tire on it face down, slide the hub on the axle and solder the spokes from the back side?

[mmagliaro]

Max,

Can't you do as you suggest with boring for the axle in a brass rod but make it larger in diameter than the tire.  Part off a thickness of the rod, say 1/8th".  Then insert the axle and chuck the assembly in the mill/lathe and machine a recess into the rod that the tire rim, not including the flange, just fits into.  Now you can have the axle sticking up through the recess, put the tire on it face down, slide the hub on the axle and solder the spokes from the back side?

Yep.  This is one of the ideas I am considering.  That dished-out recess has to let the tire "just fit into", as you say.
I will probably have to make a few before I get one just right.  But I agree, once I have it, I think this will work.

[Lemosteam]

Ok Max.  You've forced me to go old-school on ya.  This may not satisfy all of your requirements but I am just trying to illustrate that all pieces can be accurately located before the soldering process.

[victor miranda]

rut roh.

[mmagliaro]

Thanks, John.  Nice drawing!  (I am not kidding!)

Yes, I've been pondering something just about like that.  The key is making that recessed disk accurately enough.

I'm not TOO worried about the location of the spokes.  I can draw out a pattern on the computer, print it on paper, and
score right through it with an Xacto to make lines on the brass plate.  The spokes just have to be straight and
evenly spaced to the tolerances of the human eye.  The concentricity of the wheel is the big thing.  That has
to be better than the human eye, because otherwise, when it rolls, the "egg-shape-ness" of it, if there is any,
will become quite readily apparent.

I have one more tire to cut.  I did the first traction tire one of the "new type" (with the little recess in the face)
last night.  One more to go.

[Lemosteam]

Well not adding the pins saves a lot  of time.  The center axle could be extra long and you could put another disc open top to act as a clamp for the assembly, where you could put the axle back in the collet to check runout an if too high, the clamp could allow you to true up the wheel as an assembly.

[peteski]

I'm not TOO worried about the location of the spokes.  I can draw out a pattern on the computer, print it on paper, and
score right through it with an Xacto to make lines on the brass plate. 

Brass?  How you are going to prevent the solder from soldering the spokes to also adhere to the brass plate?  It would make sense to make the plate out of aluminum (which is soft and easy to machine). At least that guarantees that the soldering will not be a problem.  Regular solder and flux used for brass will not stick to aluminum.

[mmagliaro]

Brass?  How you are going to prevent the solder from soldering the spokes to also adhere to the brass plate?  It would make sense to make the plate out of aluminum (which is soft and easy to machine). At least that guarantees that the soldering will not be a problem.  Regular solder and flux used for brass will not stick to aluminum.

The wheel will be sitting face-down on the brass plate, and I will be soldering the spokes from behind.  I will be
putting a little flux on the joint between the spoke and rim and soldering there.  While it is theoretically possible for me
to flow a lot of solder down into that joint so that I end up sticking myself to the brass plate, in practice, it will be
very unlikely.  I probably will not be able to get that brass plate hot enough to even stick solder to it.  The flux will be the key.
I need to be able to get the local joint between spoke and rim hot enough to flow solder without heating up the whole brass plate, which would be impossible with an iron. 

I do like your idea about aluminum.  It's very easy to machine and I don't think it would absorb as much heat as a brass plate.

[JMaurer1]

Two words: Solder paste

Put it on and heat the entire thing in an oven until it melts. I don't know if the solder paste is structurally strong enough, but it should work otherwise. Just a thought.