building a 3" scale bobber caboose

[Harlock]

It took a while to formulate exactly how the pedestal assembly was going to come together using water jet pieces, but enough morning shower sessions (that's where I get all my hairbrained ideas, standing in the hot water waking up, after sleeping on it) and then some decisions were made. Over the next few weeks some drawings were made and then sent off to be waterjet by fellow live steamer Doug Maywald. I am machining two sets of pedestals and spring rigging, one for myself and one for Jim Sabin who is building a nearly identical caboose.

The first order of business was to double check all of the height setups to see if the caboose would end up at the right spot when sitting on the springs, relative to the coupler which is already installed. A simple drawing was made for this. The set up is very close to prototype in heights and what-not, except our coupler is a little lower on the frame because it is set up for 2 1/2" scale coupler standards like the rest of my train, so as to be compatible with 2 1/2" scale equipment which is not far off from my 3" stuff. 2 1/2" scale coupler height is 5.42" to the centerline from the top of the rail. (for 26" coupler height prototype used on many narrow gauge railroads)

Like the Chloe, the springs are set up to actually work, which means in physics of scale they are generally thinner or have less leaves or a combination of both compared to prototype, but still look the part.

The pedestal frames are two identical waterjet 1/4" plate pieces per pedestal, with welded or silver brazed spacers between. An RP outer fascia will cover up the outer pedestal frame with a high strength plastic plate that is cast in appearance. It will look the part like all my other scale hardware.

I left locating holes to pin the blocks for locating while clamping for welding, and decided I would pin one side only of each spacer and let the other side float while a big locating block in the journal slot would actually do the locating between the pedestal frames, to make sure the frames are parallel and aligned perfectly for the journal.

On the front side the holes will be covered by the fascia, on the backside I will fill them in.

Picture three shows one caboose worth of pedestal frames and two sets of spring hangars. The spring hangars were waterjet from 1" thick plate, then over the last two evenings I drilled the hole and machined the slot in each one, and generally cleaned them up. The only thing remaining is to lightly drill and ream the hole at the curved end of the hangar, which is still just a rough waterjet finished hole.

The slotted hole is so that the hangars can be adjusted to precisely center the springs, then a second lag is put in the round hole when ready. Like everything else these will be home made square head lags. The slotted hole is invisible once the spring hangar is installed. The slots were my dad's idea.

When cutting 1" steel plate with waterjet, there is a slight pattern at the far edge which was the bottom of the plate during the waterjet process. The water begins to spread and a noticable grained curve is visible at higher water cutting speeds. The angle compensator however keeps it fairly straight and taper from spreading is minimal. Fortunately all of this will be hidden on assembly so there is no need to touch up the surface. waterjet parts can be treated kind of like a fine casting. There will be some imperfections, but every single one will have the exact same imperfections in the same spots. Every one had the flat end milled off a tiny bit to get rid of some burring where it attached to the rest of the plate, for example. the burring was identical on each one.

Anyhow that's what I've been up to for the past few months in-between some down time and work being very busy.

Next up is to order the material for the spacers and cut to shape. It's all set up so that the basic dimensions are stock metal dimensions and only one dimension needs facing. I will also order an RP fascia sample.

-Mike

[Brian Hilgert]

Very Nice!
I'm glad to see that I am not the only one who finds the drier as a perfectly good workbench!

What are you going to use for the Journals? Castings or machine out of stock?

B

[Harlock]

Very Nice!
I'm glad to see that I am not the only one who finds the drier as a perfectly good workbench!

What are you going to use for the Journals? Castings or machine out of stock?

B

The dryer is right next to my mill so it ends up getting used as a staging table for parts I'm working on.

The journals will be machined from solid stock, with roller bearings inside. I will likely get something a little wider than the pedestal slots, then machine down to form the shoulders between the pedestal frames.

Like the pedestal frames, an RP cellar door cover will give the detail on the part that people can see.

[Love4Steam]

Those look familiar! Somehow they look even better after you machined them. Really coming along nicely. Keep up the great work!

[Kimball McGinley]

Mr. Masse: I have been looking for a live steam friendly waterjet source to cut some brake shoes from 1/2" steel plate. Can you share your source?

[sabin]

Thank you Mike for your continued contributions to my caboose project. And thank you Doug for your water jet parts. I would never be able to finish my bobber without you guys.

Thanks,

Jim

[Harlock]

Mr. Masse: I have been looking for a live steam friendly waterjet source to cut some brake shoes from 1/2" steel plate. Can you share your source?

PM sent....

[Harlock]

Hello all. After many months of halted progress, it is time for an update. This is one of the most interesting pieces so far, the fabrication of the caboose pedestals.

When last I updated above, the pedestal frames had been waterjetted. The next step was to fabricate all of the spacer blocks that go between each frame. As I mentioned above, each block is pinned to one frame only - a die block will locate the two frames together via alignment of the slot.

Here are some family photos of all the metal parts for each pedestal for two bobber cabeece. You have the frames, the spacers and the hollow pins. You can also see the RP plastic fascia that sits on top. Later on it will have one modification made to it, covered in a future post.

Each spacer was machined to a very precise length, with precisely located pin holes. the wood beams below the caboose are planed very accurately to 1.25" width and do not vary between locations, so I was able to machine all the blocks the same. A lot of repetitive work.

the bottom spacers have a tapped hole for the keeper plate.

in the next post, we'll talk about the welding jig.

[Harlock]

Using my trusty Dake arbor press, I pressed in all the blocks to half of the pedestal frames.

The clamping jig uses a very precise die block to align the frames via the slot, where it matters the most.

The die block I machined with a fly cutter in my new mill, which worked flawlessly. Careful tramming of the mill and alignment of the vice just beforehand paid off.

in the third photo you can see the parts needed for clamping - the aluminum die block, two pins to check alignment on the frame holes, and clamps.

In the fourth photo, the frames are sitting on the die block waiting to be clamped. The block is taller than the frames, so the frames are both resting on the top of the slot as a vertical reference surface. When the clamps are tightened up, the spacer blocks set the parallelism. In reality, the hole pins aren't really needed, they are just a sanity check. All of the frame ends are exactly identical water jet pieces.

in the fifth photo, the pedestal is set up for TIG welding, after the pin and block are removed, leaving just the clamped frames and spacers.



(P.S. can you tell I like group part photos? )

[Harlock]

In the first and second photos, here is one of the frame sets welded up.

The third photo shows the RP fascia being glued on. Once again, you can never be too young, too rich or have enough clamps.

[Harlock]

In an earlier post I talked about a needed modification to the RP fascia. You see, those bosses at the top where the large bolts go through the car frame really don't want to be plastic, because there will be a lot of force bearing on them. Over a long period of time they may crack, even though the PA-2200 material from Shapeways is very flexible and consists partially of nylon. While at the hardware store I happened upon some machine bushings that are an exact fit, they just needed some height taken off of them.

To trim the height down, I grabbed the bushings with some V blocks and milled away. There is another bushing at the bottom of the blocks to keep the V-blocks straight.

I then set up the glued pedestal in the mill and milled the bosses down to the metal with an endmill the same diameter of the bosses/bushings. (sorry I only have a 'before' picture for that one)

Then I glued the bushings in and voila! Almost ready to paint.

[Harlock]

In the previous post I said "almost" ready to paint; there was one more small detail to attend to. There is a visible seam between the RP fascia and the metal under-frame. On the advice of my father I tried some DevCon patch and fill and smoothed it out. The stuff smells nasty going on but it works. Once the VOCs evaporate you're left with a nice sandable item. I did not take a picture after I filled it and before paint, my apologies. But if you've seen bondo on a car you've seen that. JB Weld would likely also have worked, though this is a one part filler so less trouble, if you don't mind toulene. Disposable rubber gloves are necessary to smooth it on with your fingers. You can't do it with a stick. The sanding goes relatively quick after that.

After that (and a very long weather delay) I painted the pedestal on the day of this posting and it is now complete and ready for installation. It was shot with automotive primer then satin black paint. The paint really gives it that cast look and 'pulls the room together' in Lebowski terms.

The last picture shows the back side that will be completely hidden.

Very excited to have gone through the entire process with one, the next 7 will go quickly in comparison. The next set of RP fascias will have the boss mod built into them already.

This has been an interesting process using all modern techniques; water jet, RP and TIG welding, rather than a traditional casting. For this short run I am not sure which would have been more cost effective in the long run, but after trying to deal with foundries and tackling pattern making, I decided to go the modern route for this one.

Thanks for looking! Now to do the rest of them...