Large Scale Central

Corn syrup tanker

Modeling Technical Modeling
#1

I’ve been drawing some parts up in hopes of modelling this:

Some of the stuff I had 3d printed has started to come in. I had bolsters printed in SLS nylon. I tried to dye them black, but they came out dark blue. Not bad for a first try, as I was looking for any color other than stark white. This was the product of black & brown Rit dye. Next time I’ll just use brown.

I had my side frames printed in acrylic, and made an RTV mold of them. Unfortunately, the pattern didn’t come out in one piece, but that was not unexpected. Here’s the first casting out of the mold. I’ll make three more, then re-mold with all four so I can do a pair of trucks in one pour:

Here are renderings of some of the other parts I’m waiting on to use as patterns for RTV molds:

And other parts that will be printed in SLS nylon:

The last one will probably get redesigned. Apparently the printing the handrail is asking too much of Shapeways, as I got a failure notice when they were removing it from the print tray. I will probably take the railing out of the 3d print, and make a jig to form it out of 1/16" brass wire.

#2

Are these going to be offered for sale? Kits? even just some of the parts???

#3

I’m hoping to make it a kit, yes.

#4

That’s great! I’ll be watching to see if I can afford them. Great work, by the way. Were the walkways on the PS hopper printed? Etched? They look great.
Your detailing sets these cars apart. It’s tuff to look at some custom cars that are below current standards, and still consider them.

#5

Joe: Yes, the walkways were made out of photoetched brass on that car. There will be some photoetch on this car, but significantly less.

#6

Here are the final truck castings. I tried to take a picture of the bearing caps, but since they’re printed in clear acrylic, they didn’t photograph well. I will have to wait till my wheels come in, and I can paint everything, to get a better picture. These will have music wire springs in the back row (for functionality) and SLS nylon springs in the front (for looks, to scale).

(http://burlrice.com/_LS_CornSyrup/assembled1.jpg)

#7

My patterns arrived from Shapeways last week. I made up most of my first generation molds over the weekend. Here’s the first casting of the saddle:

(http://burlrice.com/_LS_CornSyrup/resin_sadle.jpg)

I think I went to low on the poly count on the tank car ends. They came out with very visible concentric circles. I should have taken a picture, but I didn’t. I primed and sanded three times to get a smooth surface. Here’s the first casting:

(http://burlrice.com/_LS_CornSyrup/resin_end.jpg)

#8

Well Burl, the casting sure came out nice. Maybe a bit of had work paid off. Was it any cheaper?

#9

Yes, because I need two. The A end is the same, except the brake wheel support - so I poured another and carved that part off with a chisel. It takes approximately 2 ounces of resin to pour one end.

#10

Burl,

I was referring to the Shapeways print. Was it cheaper using a coarser resolution for the source print?

#11

(http://burlrice.com/_LS_CornSyrup/resin_bolster.jpg)

#12

It wasn’t the resolution of the print that was the problem. It was that I should have made more sides to the drawing in Sketchup.

#13

Thanks for the clarification Burl. Nice work so far. You are a master at casting those things…anything…

#14

After getting the 4" tube from Plastruct, I found the wall thickness to be thinner than expected. I had some 3.5" tube already, and it measured around .070" wall thickness. I think the larger tube was somewhat thinner. The SLS nylon ring I had printed didn’t fit exactly snug, so I wrapped it with a few layers of tape to get a tight fit.

I kept going over in my mind what would give me the best bond between the printed ring and the tube, and I was leaning towards epoxy or gorilla glue. I have a phobia about weak glue joints. I especially didn’t want to get this thing almost ready to mold, then fumble it & bust the seam. Then it hit me: expanding foam.

I wish I had thought of that before I cut the tube. As it is, the ~.060" thickness of the plastic lets it flex & makes it very difficult to get a true cut on the miter box. Hind-sight is 20/20 though.

#15

I would have said use the gorilla super glue or even pvc cleaner and glue. I would have said make an inner sleeve for more gluing area and strength. I wouldn’t have thought of using expanding foam. With the way that stuff sticks, I don’t imagine that joint can fail? That is a cool, modern thinking idea!
If it’s good enough to hold commercial buildings roofs together…it autta hold up here!

#16

(https://fbcdn-sphotos-d-a.akamaihd.net/hphotos-ak-xpa1/v/t1.0-9/10928987_636596166463067_2548565506499776257_n.jpg?oh=fe21d23278ba3900da75c98802347316&oe=555AEF5A&gda=1429056738_d128a3c47b904c6dd4f1c2f442dc4c9c)

(https://fbcdn-sphotos-f-a.akamaihd.net/hphotos-ak-xpa1/v/t1.0-9/10923503_636596146463069_68766334344089722_n.jpg?oh=5d31a47faf1982f8b8821813f2490d33&oe=55216504&gda=1433055366_6106209c1d883c692edf48f2d7d2ef27)

test prints done and can be sent out tomorrow Burl…

#17

Very nice job so far Burl. Ive had to remove things embedded in that foam before and it wasn’t easy. I have noticed it can shrink some with age, but seeing that it’s totally enclosed in the tube I think that it would be minimized. My buddy is getting a 3D printer soon. I’ll be showing him this thread. Keep up the good work.

#18

I took the easy way out on fitting the wrapper in the middle. When I had the connecting ring printed, I also printed a half ring. I know there’s a formula for calculating the intersection between two cylinders, but this seemed less error prone. My gut was that any slight variance in the wrapping underneath would have a bigger effect on the wrapper, and that seemed to be true (the main tube got two layers of poster board wrapped around it to bring it up to size).

The wrapper gets taped around a blank with the half ring:

(http://burlrice.com/_LS_CornSyrup/sanding_jig1.jpg)

The disc sander makes quick work of the raw edge, which is resin. Since SLS nylon doesn’t sand well, its easy to tell when I’ve sanded far enough:

(http://burlrice.com/_LS_CornSyrup/sanding_jig2.jpg)

#19

Some more progress on the castings. Here’s the final bolster & saddle:

(http://burlrice.com/_LS_CornSyrup/resin_bolster_saddle1.jpg)

And here they are together:

(http://burlrice.com/_LS_CornSyrup/resin_bolster_saddle2.jpg)

I’m pretty happy with the fit on this. I don’t think I could have ever gotten it to fit this well if I had made it by hand.

I don’t have much to show yet on the main body. I glued the wrapper on last week, and almost got discouraged enough to peel it off and start over. My problem was that I tried taping it on while the glue set, and I never could get the edges to lay flat enough. So I came up with this:

(http://burlrice.com/_LS_CornSyrup/tank_body.jpg)

Its the mold I used to make the wrapper, trimmed slightly to fit the diameter of the tank body. I wetted the edges of the wrapper with thin CA, then wrapped the rubber mold around that, with a layer of sacrificial styrene, then band clamps on top of all of it. The perk to using the old mold was that CA won’t stick to RTV, so I could clamp it down extremely tight & not worry about it not coming off later.

Currently, I am sanding & filling on the body. I’m being very picky with it at this stage, because I don’t want to have to sand & fill on the finished tank casting. Maybe I’ll have something to show for it later in the week.

#20

the other jigs done, not the correct size wire for this jig, but it works

(https://fbcdn-sphotos-b-a.akamaihd.net/hphotos-ak-xpf1/v/t1.0-9/10408537_639084032880947_6561889117449227239_n.jpg?oh=22f874f1f7b8689fa90b4a227eef5f39&oe=5520A690&gda=1432373498_05d4ce5d47d12dc02bb6b1012f8f3312)