March 17, 2013

A Multi-Pronged Assault

3D master model above
a wooden truck
Work progressed on several fronts this weekend. First, my son Chase was visiting and we fired up the vulcanizer and spin caster  to try making some cast metal freight car trucks. I have been working with Eric Cox at Panamint Models to develop an O scale truck. Eric did the master using a 3D software package and the Shapeways Printing Service.

The image at the left shows the 3D master compared to one of my wood trucks. I was concerned that the master was too wide. But the parts fit together amazing well. The precision of the 3D printer is impressive. Eric is also an excellent designer. The parts had all the correct detail.

The Ultra Frosted Detail resin from the 3d Printer survived the vulcanizing mold making process at 300 degrees F for three hours. However, the undercuts on the brake shoes caused them to rip off as we removed the softened resin from the mold.  After prepping the mold with gates and vents, we made about 15 pulls with white metal. The mold worked well, though we were getting some leaking near the end.






As cast parts. The bolster was too wide.
The casting had some flash, distortion and shrinking, so the parts did not fit as precisely as the master. But they looked great. As I suspected the master was too wide and the NWSL wheel sets barely fit in the truck.

I decided to laser cut new bolsters. They were 1.55 inches long and fit perfect. These are visible in the last truck photo. I drilled out the axle hole in the first truck I tried, so you can see the axle shaft. But I found out that wasn't necessary to clear the side frames. So the second truck has the journal caps in place.


Revised trucks with laser cut bolsters
 
I sent samples of the casting and two NWSL wheel sets to Eric so he can evaluate them.  He plans to revise the master to fit these wheel sets better.

The brake detail on these cars is great, but making the brakes work will be tricky.

I also learned that I needed to add insulating washers on the axles to prevent the outer face of the wheels from rubbing the side frame and causing a short.




Also arriving this weekend was a package from Brian Kammerer with a batch of twigs he found that have excellent branch detail. He had prepared them in glycerine and water. I let the twigs dry in the garage over night. Then I hit them with brown, khaki and black paint. I used some of them as background trees and to fill in some of the forest areas. They look great. Thanks Brian!

On the road show, I added the sub road bed for the tracks to the engine terminal.

My mom is working on revising the bunting. We replaced the earlier swags with a pleated skirting made with the red-white and blue with stars bunting. So far, everyone agrees that they look better.

If that wasn't enough we had golf lessons and I did a 10.25 mile run to prep for a half marathon next weekend. Whew! A busy weekend.





New bunting for the road show

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