Large Scale Central

Truck springs

Modeling Technical Modeling
#1
I had been using Aristo’s modern roller bearing trucks for almost all my scratch-built rolling stock. Now that they’ve become scarce, it’s pushed me to find an alternative. Below is what I’ve come up with. This is just a rendering of a Sketchup drawing – I’m having the first set printed in SLS nylon & don’t have them yet. I intend to put Gary Raymond 33” wheels in them, with flanged ball bearings in the journals.
 
After my experiment with the AAR-type B trucks, I have realized I need much weaker springs. Spring steel is way too stiff. I’m looking at phosphor bronze now. I realize I could wind my own, but I’m afraid they wouldn’t be consistent. This particular truck has two different size springs. In 1:29, they work out to 0.1896” & 0.1034” OD. Fully compressed, they need to be 0.1916”. I will probably experiment with whatever I can get from McMaster-Carr, but I was wondering if anyone had any resources for miniature springs they’d be willing to share?
 
 
#2

Wow that’s a lot more detailed then any “off the shelf” truck I have seen. Very nice.

Stupid question time here. Why cant you print springs out of some kind of plastic? Metal springs look to be too small (scale thickness of the wire wise) and steel being too stiff, maybe some kind of plastic would be soft enough but not too soft when rendered in proper scale.

#3

I’m thinking nylon at that diameter would be too soft. But it might balance out with one steel spring, and the rest nylon. Now to figure out how to draw that in Sketchup…

#4

Burl, I have a lot of springs that are .106 OD x .165 tall .098 when fully compressed. It takes about a pound by the “feel” of them to reach full compression.

If you can use them I’ll hook you up with a bag of 5000 for the cost of shipping.

#5

Randy, the OD would be close enough, but I need 0.1916" tall when fully compressed. Thanks for the offer though.

#6

and why would you want them to fully compress anyway?

#7

So you know the bolster can’t pop out by accident if they’re overloaded.

#8
 
 
I received my first print from Shapeways today. It needs a couple things tweeked.
 
I made the bolster a little too narrow. You can’t really tell in the photo, but I had to add a block of styrene to the sideframes (right under the writing) to keep the bolster from twisting & clearing the printed stops.
 
The spring seats need to be a little wider to keep the springs centered.
 
My biggest problem is that the springs are too soft. There are 8 printed springs & 6 metal springs in each truck. I thought I could leave out the innermost printed springs if needs be, but even with all the springs in, its too soft. I will probably order some metal springs from the links some of you provided & keep experimenting. I tried a set from a spare set of Aristo Craft trucks I had lying around, but they were too stiff. Or I guess I could run with them bottomed out. At least I know they’d track that way.
 
Some of the sideframes have very visible print lines. That would seem to indicate Shapeways is manipulating the individual parts within my file to re-orient them. I am considering printing a master in acrylic to solve this problem. I’m happy with the bolsters in SLS nylon.
#9

(http://burlrice.com/_LS_Barber_S2A0/1st_3d_print_painted.jpg)

#10

Nice & amazing!

#11

Question. Why do you really need the springs to be compressed a little? If its just a visual thing, then you could glue the bolster to the side-frames slightly lower then at the top, and then put in your plastic springs. I know my Aristo trucks have actual springs in them, but they don’t seam to compress any, I mean, the bolster appears to me to always be at the top of the opening in the side-frames.

#12

I got my Gary Raymond wheels in this week, as well as some suitable springs. I decided to go with Kadee (IH) 701 springs, cut in half, for the main springs - they’re in the back row, so you can’t see them. Kadee #875 springs were used for the smaller springs in the middle row. That gave enough support to let the whole assembly flex without bottoming out. For the main visible springs, I used my 3d printed springs - which have the diameter correctly scaled.

This is the first set of Gary Raymond wheels I have had, and I am very impressed. I wasn’t expecting the wheel backs to be machined out, but man do they look nice. These would look great on a covered hopper, or a tank car.

#13

Burl,

been admiring your work from a distance and it is fantastic with the resources you are using. I started and got spoiled with the resin 3d printers back in 2006, it is hard to go back, although I recently did have Shapeways do a print on an I beam and it came out great for what I am using it for. One question is that how much will the springs compress in your truck when loaded with a car? being very familiar with the prototype the bolster is pretty close to touching the top of the side frame when there is no car on them, and with a loaded car the bolster would be down only about half the distance shown in your picture. ultimately will affect ride height san coupler position.

Al P.

#14

Good question, Al. Measuring a set of Aristo trucks, I get 25.5mm to the top of the bolster. Mine measure 22mm. I may need to make a slight adjustment there.