3D printing SP prototypes

[ATSF_Ron]

And life continues to throw curve balls this week...anyhow, I thought I'd have this wrapped up by this evening.  Wrong!  Desoldering the truck pickups went relatively easily.  As I went to get the electronics wired up to the new tender, I discovered an issue.  Pic 1 shows the BLI tender chassis.  Pic 2 is the 3D printed SP chassis.  Note the difference in diameter where the trucks screw to the bottom of the tender!  The 3D printed tender clearly has larger openings, so the factory BLI screws have nothing to bite into.  My micrometer says 0.074" is the thread diameter.  Okayyy...so I guess I can try to measure the 3D printed screw hole diameter (not too accurate I think) or come up with another solution.




I think I saw an article some time ago that solved a similar issue.  Get some styrene of the correct diameter, glue it into the 3D printed hole, then attempt to drill it out to the BLI screw thread, or close to it.  Any thoughts on this one, Railwire folks?

Thanks,

ATSF_Ron

[Chris333]

I used to use 1/8" styrene tube and just thread a Kato truck screw into it.

This is an old photo of mine...  (20 years old now     )
https://www.trainboard.com/highball/index.php?media/mp-4-4-0-tender.28083/full

[ATSF_Ron]

Thanks, Chris. That’s pretty close to what I remember seeing.  Maybe it was even your post! It was a while ago…

[ATSF_Ron]

I bought some styrene tubing 1/8" diameter, smallest I could find locally.  Actually it's solid tubing with a tiny dimple in the center for starting a pilot hole, I assume.  Even after a LOT of sanding it's still way too big to fit in the mounting hole of the truck frame.  I suppose I could buy smaller tubing like 1/16" but can't seem to find any locally.  Two other thoughts have occurred to me though.  One is I could drill out the hole in the truck frame to accept the sanded down styrene rod, then glue it in and drill a pilot hole for the truck screws.  My concern there is breaking the 3D printed frame while drilling.  I've read this can be a concern with some 3D printed materials.  Another option (maybe?) is to fill in the 3D truck mounting holes with two part epoxy, then drill out & screw into the epoxy.  My feeling is it seems that the styrene tubing would be a more secure installation than trying to screw into two part epoxy.  Has anyone done the two part epoxy technique before?  I seem to have a bit of analysis paralysis on this project, lol!  Thanks!

ATSF_Ron