12" working railroad

Discuss park gauge trains and large scale miniature railways having track gauges from 8" to 24" gauge and designed at scales of 2" to the foot or greater - whether modeled for personal use, or purpose built for amusement park operation or private railroading.

Moderators: Glenn Brooks, Harold_V

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Topics may include: antique park gauge train restoration, preservation, and history; building new grand scale equipment from scratch; large scale miniature railway construction, maintenance, and safe operation; fallen flags; track, gauge, and equipment standards; grand scale vendor offerings; and, compiling an on-line motive power roster.
rkcarguy
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Re: 12" working railroad

Post by rkcarguy » Thu Dec 06, 2018 11:42 am

My S-12's truck sides are finally into the system for "infill work". We changed to a different nesting software for the laser table that will select parts from "infill work" files, to use up leftover materials on each sheet. I made a few last minute changes to the truck sides, incorporating larger diameter springs (I had a old set of large diameter Volvo red block valve springs laying around from my boats cylinder head rebuild), notched out the spring areas so I can weld in stepped discs of plate for the spring retainers, and refined some of the hole sizes as I will be ream drilling and tapping many of the holes.
My imageshack account expired, so I'm going to have to owe you some pictures until I can get a moment to renew it. Hoping to have all my truck parts to work with over Christmas break.

rkcarguy
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Re: 12" working railroad

Post by rkcarguy » Fri Dec 07, 2018 1:13 pm

Truck sides are cut!
lasertrucks.jpg
trucksidesdone.jpg

tomc
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Re: 12" working railroad

Post by tomc » Sat Dec 08, 2018 9:24 am

Nice. It is neat you have a burner to cut metal for you.

Tom C.
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rkcarguy
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Re: 12" working railroad

Post by rkcarguy » Mon Dec 10, 2018 4:08 pm

Tom, this is one of the reasons I took on such a project:)

The first steps on these, are going to be welding in the upper and lower spring perches. Then the channel "bolsters" and heavy pipe will get welded/bolted between the truck sides and all the parts get the edges chamfered and then go in the roto-blaster. Then it's time to ream drill and tap the holes 3/8-24 in the equalizer bars for the flanged pillow block bearings.

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Re: 12" working railroad

Post by Harold_V » Mon Dec 10, 2018 4:50 pm

rkcarguy wrote:
Mon Dec 10, 2018 4:08 pm
and then go in the roto-blaster.
Steel shot?
If so, that's a wonderful way to blend surfaces. Wish I had one in my shop. I have to settle for sand or glass bead, and a small cabinet, which is somewhat restrictive.

H
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rkcarguy
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Re: 12" working railroad

Post by rkcarguy » Mon Dec 10, 2018 7:22 pm

Yes it basically shoots shot at the parts on a rotating table. The only thing I don't like about it is it seems to "expand" the side of the part it hits, and you have to do both sides or it will warp the part. Overall it's nice to have access to, it gives a textured finish for paint to adhere to and removes the mill scale from the material...both vital to have a lasting paint system.

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BigDumbDinosaur
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Re: 12" working railroad

Post by BigDumbDinosaur » Tue Dec 11, 2018 1:24 am

rkcarguy wrote:
Mon Dec 10, 2018 7:22 pm
The only thing I don't like about it is it seems to "expand" the side of the part it hits, and you have to do both sides or it will warp the part.
Roto-blasting is basically a somewhat uncontrolled shotpeening operation. What is happening is the surface being struck by the shot is being cold worked and thus experiences some dimensional change. You can somewhat mitigate this effect by limiting the blasting operation to the shortest amount of time that will achieve good surface "profiling." In other words, don't beat the parts to death. :D

Another mitigation technique is to place the pieces near the periphery of the platen (rotating table), which has the effect of reducing the average amount of time the pieces are in close proximity to the blast nozzle. That is when the shotpeening effect is at its greatest.
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Harold_V
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Re: 12" working railroad

Post by Harold_V » Tue Dec 11, 2018 2:32 am

rkcarguy wrote:
Mon Dec 10, 2018 7:22 pm
The only thing I don't like about it is it seems to "expand" the side of the part it hits, and you have to do both sides or it will warp the part.
That's not restricted to shot blasting, although it may be more extreme because of the severity of shot blasting. The same thing happens when you bead or sand blast. Any time you alter the surface of a piece of material, you mess with stresses. Any change will either cause the piece to pull or push. That's a tough lesson for some folks to learn, which they do only when they scrap a project because they're ignored the admonition to address stresses when working with metals. In a machinist's world, it's generally addressed by roughing features before any finish cuts are taken.

I'm only vaguely familiar with this type of blasting. I know Wheelabrator hurls the shot, it is not propelled by air pressure. Does the equipment you have access to work the same way?

H
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rrnut-2
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Re: 12" working railroad

Post by rrnut-2 » Tue Dec 11, 2018 6:55 am

I used to have access to shot blasting equipment. I tried a hood for a tractor once, wasn't pretty! It did get all of the paint off though. :D

Jim B

rkcarguy
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Re: 12" working railroad

Post by rkcarguy » Tue Dec 11, 2018 11:32 am

Our roto-blaster consists of a large AR plate wheel(think steamboat) that spins very fast, and the shot is fed into it and then re-collected, elevated, and fed back through the system again. The table is about 6'-4" in diameter and spins slowly, and the inside is lined with replaceable rubber? panels.
The shot is pretty small, I'd say .015-.020". I have found if I make sure I run the parts the same time on both sides, the end result is still flat. My truck parts are 3/8" plate, so they will be fine, but I need to make sure they stay flat so the sliding action of the outer plates on the inner frame isn't messed up by the plate being warped.
I am well versed with material warping and moving, stainless can really go nuts. I milled a small custom channel for a guy years ago and the sides pulled in so bad we had to start over with a larger piece of stock, so equal material could be milled off all the sides so it would stay straight.

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steamin10
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Re: 12" working railroad

Post by steamin10 » Tue Dec 11, 2018 12:12 pm

For my home shop I have a gutted out fridge with a plate glass front fitted into the door and covered with a piece of screen wire to deflect the sand. Thsi keeps the sand from etching and clouding the glass. Teh glass panel was stolen from an old cabinet style TV and held with a small angle iron for a mount. some RTV seals the gaps. A walk tread grate makes the floor about door level, the freezer door is reversed with the main door. The snad gun and hopper mostly sit inside the cabinet, and a small sand lot shovel reloads the dusty sand for another run. The blower unit is from a junk window air unit, and has a soft clothes dryer duct that leads outside. A light switch turns it and the two cabinet spot lights on for ample lighting. Two hand holes in the door are covered with rubber slits, to keep the majority of the sand in the abinet. The walls of the cabinet are lined with scrap plywood, and get replaced when blasted through. (has not happened yet, but are showing the many hours of wear.) The biggest problem is keeping the ceramic nozzles in stock. They break easy and only take a bump when used. I have been taking some copper tube and using that for a nozzle as they dont shatter, and are very cheap to make, but dont last all that long. It should be noted that any sand / grit/ media blasting is noisy, creats dust, and requires a lot of air. I have a 80 gallon Ingersol -Rand to run the thing, but you wont do it with a 20 gallon portable. I used a 100 lb LP bottle for air storage, to get started, and get that puff of air to do some work and then wait forever for the air to catch up. (I had stinky air from the used tank). But you can get the idea that we worked around the problems of the hobby. Blasting things to a a matte finsh was very nice and saved time over hand sanding and wire brushing to remove tooling marks..
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rkcarguy
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Re: 12" working railroad

Post by rkcarguy » Tue Dec 11, 2018 3:45 pm

I have a fairly powerful 220 volt 60 gallon air compressor, as I used to run one of those portable sand blasters. I will probably see if I can cobble something together once I've got my container shop setup so I can blast small to medium size parts. My main concern is getting a good profile for painting, as the weather here is just ruthless and everything is soggy and wet for months on end. Anything outside needs to have good prep and paint system if it is to survive any length of time.

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