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Projects ... A3 Switcher   Tie, Arch Bars, Springs and Assembly 10/23/2006

This page covers the machining of the Tie and Arch Bars, Springs and Assembly ... Section 3.5 - 3.7 pages 19 - 22.

Well it has been a while for since my last update to the A3 Switcher. Just a lot of things going on and of course my new workshop. Building the workshop took a lot of time and effort so I wasn't able to work on the A3. But now that's all done (well ... most of it) and I'm back on the A3 !!

The Tie and Arch bars were easy to make. Since the bending and screw holes must line up perfectly ... bending and drill fixtures were made ... the only way to ensure a perfect fit. The material for the Tie Bar is 1/16" 260 Brass sheet; the Arch Bar same except 3/32" thick sheet. McMaster Carr had both so I just ordered the material from them. I usually get my order the next day.
 
The band saw is used to cut the material from a 12" x 12" sheet. It is much easier than a hacksaw or a fret saw. I gave myself plenty of room by cutting each Tie/Arch Bar about 3/8" wide and 6" long. The added length will ensure plenty of extra length to compensate for the bends.

The milling was fairly easy. The Tie and Arch bar width are fairly tight at 0.310" - 0.312". I found that my width was .004" different from one end to the other. To solve that I would file down the extra as shown in the next photo.

     

The file on the right was to remove the major burrs the milling process left behind. The 400 grit sand paper was used to fine tune the width and make the surface smooth. As can be seen I did a lot smoothing by the amount of brass left behind.
 
Here I have the bars marked where the bend line should be, just line them up over the bender and pull the arm down little. My bender is very different from the vise version. Both types will do the job. But since I have a hydraulic press, I just made an adaptor, now I will be able to use it on another project or the A3. The dial indicator helped me determined when to stop the bending, once the springback was found I would pull down to a specific number and stop. Less bending later! Worked good for me.

Now the Springs.
Never made a spring before, although Kozo provided a lot of information I thought it would be a good idea to learn more about making springs. Here are two articles that helped a lot: How to Make Springs and Design and Wind Your Helical Springs by Kozo Hiraoko (who else!). Kozo article is actually 9 separate pdf files. I also called 3 spring manufactures and asked about heat treating after winding ... yes ... you should heat treat.

My spring material is Music Wire (302) bought from McMaster Carr, manufactured by Matlin Co out of Ohio. I have lots of it ... started with about 61 feet ... now have about 55 feet, but only paid $5.61 so now I can make more springs!

There is a lot of stress in the winding after they have been bent, heat treating will remove that stress ... all three said they heat treat their springs. For me about 550 to 600 F.  for about an hour. Don't know why Kozo did not mention it, maybe they really don't need it because of size etc. Also I need to do one more thing ... since I used SS I need to passivate them to prevent rusting due to the coating (not sure about this but that is what they said). Later though.
 

As you can see two more jigs! A Mandrel and a Wire Guide. The spring that is shown is a reject .. has too many coils! Should be 6, there are about 6 1/2 or so. But the coil pitch is correct ... for me 60 / 30 gears, lever in position 4 gives me the 10 coils per inch. They are easy to make takes about 3 minutes to wind. Not shown is a very important safety point.
Remove power from the lathe! Can you imagine what could happen if the lathe was accidentally turned on?
 
Here are two that are usable ... out of the six that need cutting ... 4 or 5 will do. Another jig (not shown here) is used to flatten the ends.

 

Cutting the tails requires a cutoff wheel otherwise grinding will take forever.

Another safety issue ... wear safety glasses ... those tails will spring if you are not careful. I would try to cut almost all the way through, then bend it to break it off ... worked ... but not always.

 
Finally ... an assembly!


Putting all those pieces together:
Tender wheels, bearings, axles, journal boxes, columns, bolsters, side bearing, tie and arch bars, springs and all the screws make up these two assemblies.
   

Very happy with these tenders wheel assemblies
... still a little work left to do:

Number each part, Loctite the wheels to the axles, touch up the corners a little and smooth out the surfaces. Most of this will take place when painting ... yes I am almost certain I will be painting them.

On to the Tender Frame!!
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