G Scale Model Train Forum banner

1 - 4 of 4 Posts

·
Premium Member
Joined
·
161 Posts
Discussion Starter #1
As some of you may remember, I started building a 7/8" scale model of Sandy River & Rangely lakes #23 some time back. I've always liked #10 too, and since the engines would share quite a few of the same parts I figured that I might as well start building them both at the same time. I'm still looking for any sort of drawings, but have a start with some known dimensions and a photo.

The first thing to do was start with making some drivers. As far as I know, no scale 36" drivers exist for sale, so I took my existing 33" drivers from #23 and copied the features on a larger wheel. Any deviation of the features from the prototype will be kept as identical as possible between the two engines to give them a family connection. So to start, here's a little bit on how I put the spokes in the drivers. A rotary table was invaluable for doing this.

Befor cutting any metal, I came up with a drawing showing the centers of all the fillets between the spokes and the arcs under the rim. This also gave me the information on how much to rotate the wheels to create the arcs. Here's a freshly turned wheel next to the drawing.


First was centering the rotary table and the wheel under the mill's quill. After that it was a simple matter to mover the table over the required dimension and drill the first set of holes (1/4" diameter in this case, spaced 45* apart for an 8 spoke wheel).


Second was drilling the holes that would become the fillets between the spokes and the outer arcs. In the first photo, you can see a dimension of 21.5* circled. This was rounded off to 22* and that was the total amount of distance between the holes (11* off of each previous 45* index). Another 16 holes were drilled, and you can see a bit of yellow paint as an aid to see where the material will be removed.


Now starts the fun part! After swapping the drill for an end mill, it's time to start connecting the dots. First up was creating the arc segments.


The mill's table was then moved over half the width of the spoke plus half the diameter of the endmill. Another slot every 45*.


Finally the table was moved in the opposite direction the full width of the spoke plus the full diameter of the endmill. The last of the slots were then finished (again every 45*).


After some hours and countless dial cranks later you end up with four pretty nice looking spoked wheels.


The spokes don't have any draft angles and I won't bother radiusing the tops. I don't see the need for an outside frame engine. Plus if I did, I'd have to do the same to the six drivers on #23 and that just sounds too much like work!
 

·
Premium Member
Joined
·
161 Posts
Discussion Starter #2
Next up are the main axles. The design of thses was determind by the previously purchased drivers for #23. Those originally had a 7/16" hole with a pressed in Brass bush to bring it down to a 1/4" axle diameter. The idea of having two press fits on a brass bushing just didn't sit right to me, so the brasses will be pressed out and new axles made for all 10 drivers. Probably not necessary but sometime I can be fussy and just end up making more work for myself.

Now, I also like having a stop on the axle to press the wheel against. This makes a nice, easy fit with no guessing as to how far onto the axle to press the wheel. This unfortunatly means having at least a 1/2" daimeter stop against the 7/16" diameter bored hole. With that diameter axle, you're looking at some pretty large eccentrics (for axle pumps), so the center of the axle was turned down do an accptable size. This forces me to use spilt eccentrics but so be it.

I did have a nice fancy CAD drawing, but left it at work. So instead here are the first two axles next to the original sketch. The first sketch was modified somewhat to so that a smaller diameter shoulder would be against the ball bearings that will be pressed on later. Also, I had to scrap 4 (FOUR!) axles due to various problems before I finally made these two acceptable ones. And I still have to do 3 more...


After the axles were turned, each got a small drop of steam oil on the area that would be pressed into the wheels. The wheels were then pressed into place.


 

·
Premium Member
Joined
·
492 Posts
Justin,
The gauge is going to be 45mm which works out to 2 ft in 7/8ths right? Beautiful work. Going to be coal fired of course! Can not wait to see it in person.
Noel
 

·
Premium Member
Joined
·
369 Posts
Thanks for posting the spoke sequence. I was thinking about how to do that.
I'm planning a model of F&M #2, Baldwin's 1st 2' gauge engine with outside frames.

Harvey C.
SA1838
 
1 - 4 of 4 Posts
Top