SP NG Diesel #1 (GE 50T) - Triennial or Bust

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rkcarguy
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Re: SP NG Diesel #1 (GE 50T) - Triennial or Bust

Post by rkcarguy » Fri Mar 30, 2018 3:04 pm

Sounds like you are on the right track, if you are going to play with gearing yet that makes sense.
They make nice split sprockets for the go-karts, but I don't think they go small enough to clear the wheels in your scale unfortunately.
Work has got their CNC plasma table up, and we've got some guys learning to load drawings and nest practice parts from remnants we have laying around. Perfect opportunity for you if you need me to sneak some parts in there for you, let me know and send me a DXF file and as long as it's not great big parts they'll be freebies. Right now we're sending everyone home with steel deer cutouts lol
We are setup for 1/8" to 1" materials, holes are coming out decent as long as we don't get too small for the material thickness.

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senorgilamonster
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Re: SP NG Diesel #1 (GE 50T) - Triennial or Bust

Post by senorgilamonster » Wed Apr 11, 2018 11:31 pm

Bending Tacos: I finally started work on the cab. I made a bending form for the 1" radius by routing MDF

Then made 2 halves of the cab shell. I did not cut the pieces to size before bending. After bending, I then cut the halves to the correct length so that they will match up correctly. I also cut in the door opening. I used this method...works really well: https://www.youtube.com/watch?v=jTlzcDJqcWU

I have not cut the roof profile yet - thus the current cab in the pics is too tall. I will wait until the halves are true, square, and welded together and then cut the roof profile.

I positioned the seams to be in the center behind the hood and over/under the door. This leaves the smallest amount of joint space visible + the joint under the door is even covered up by an access panel. That leaves only a couple of linear inches total visible joint line for the entire cab.
IMG_1201.jpg
A closer view of the nice radius corners:
IMG_1202.jpg

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makinsmoke
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Re: SP NG Diesel #1 (GE 50T) - Triennial or Bust

Post by makinsmoke » Thu Apr 12, 2018 6:29 am

Very nice sheetmetal work!

That looks a lot like the cowl battery box for
an M38 jeep!

Will you butt weld the edges?

What is the gauge of the sheet?

Thanks for sharing!

Brian

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senorgilamonster
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Re: SP NG Diesel #1 (GE 50T) - Triennial or Bust

Post by senorgilamonster » Thu Apr 12, 2018 8:39 am

18 ga. I am planning on butt welds but I will probably place another strip of 18 ga on the inside for added strength and rigidity at the weld point.

I would lap it if I had a tool that would give me the right bend/crimp for 18 ga. Either way I know I will have to go slow, back with a heat conductive piece, and/or run a series of short welds at differing locations to keep from warping. I don't want to burn through.

I'm off to Seattle to day to pick up a few pieces of metal including the 2'x6' piece for the deck and to resupply broken drill bits, etc.

rkcarguy
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Re: SP NG Diesel #1 (GE 50T) - Triennial or Bust

Post by rkcarguy » Thu Apr 12, 2018 11:24 am

FYI, continuous welds on thin sheet metal are going to warp it quite badly even if you jump around with short welds. I would recommend drilling a row of holes in the edge of each plate and "spot welding" to a backer bar, also known in the industry as a "puddle weld". If you look at the construction of many Baldwin diesels for example, they are actually built this way, the outer skin has rows of holes at the seams which were then puddle welded to the frame or strip steel at a splice. This will allow you to use a thicker backer bar so you don't worry about burn through, and you just get enough weld in there until it wets out into the edges of the holes and the weld is a little proud of the surface, and that is that. You can leave it, or grind it flush to your preference.
Good step drills work wonderful when working with sheet metal, I have one that goes from 3/16" to 1/2" that came in a 3-pack from harbor freight that I use ALOT. It has fairly long steps, and makes really nice holes in up to 1/4" material. The next step up has a chamfer on it, so if you are careful you can get your hole and a bit of a chamfer/deburr all on one shot.

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makinsmoke
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Re: SP NG Diesel #1 (GE 50T) - Triennial or Bust

Post by makinsmoke » Thu Apr 12, 2018 3:11 pm

My bet is the Baldwin cabs were spot welded, not plug welded. The look is very similar on the finished product, but the spot weld typically doesn’t need any drilling or clean up.

Back to the jeep guys. The sheetmetal on the old Willys was 18 gauge as well. Most pieces were originally assembled using spot welding.

Repairing the old tubs requires blasting, cutting out the rotten sheet, then either butwelding where continuous parts were cut to repair bad areas using stitch welds to prevent the warping mentioned above, or plug welding where parts are sitting on top of each other.

To disassemble parts spot welded one uses a spot weld cutter. It’s a two step drill bit that cuts a hole roughly the size of the spot weld through the top piece, yet does not penetrate the bottom sheet.

To replicate spot welds when installing new sheet, typically the top piece is drilled 1/8-3/16”, then mig welded. If repairing where a spot weld cutter was used, a few tacks are done
to fill the hole, aka, plug welding. Light grinding takes off any proud weld material. Back up your welds with a heat sink made of copper. It won’t stick. I bought a 1/2” copper tee and beat it flat, leaving one side a little off angle so I can hold it with pliers.

Most amateurs can repair an old jeep tub with practice and care. The good ones do it so well it looks factory.

Sorry to drag on, but it seemed relevant.

Somewhere there is a thread showing how to lap seams. Hisonner Master Bodenmann unless I’m mistaken.

Take care,
Brian

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senorgilamonster
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Re: SP NG Diesel #1 (GE 50T) - Triennial or Bust

Post by senorgilamonster » Thu Apr 12, 2018 7:03 pm

Call for Opinions: Does anyone see any reason not to build out my bolsters like the cross section below?

Bronze Bushings through steel channels with an inner bronze core. Then a steel bolt through the assembly from the top down with a bolt or pin on the bottom. The upper channel will be bolted to the frame cross member so that it can be dissembled for maintenance.

I'll probably use bronze bearing blocks to control the max amount of tilt.

Better ways of doing it would be welcome and appreciated.
Attachments
Bolster Pivot Exploded Detail.jpg

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Re: SP NG Diesel #1 (GE 50T) - Triennial or Bust

Post by OddDuck » Fri Apr 13, 2018 9:10 am

To my mind the inner bushing is not needed, the two outer bushings with the bolt between them would be enough. Not much of a bearing surface between the two, however.
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rkcarguy
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Re: SP NG Diesel #1 (GE 50T) - Triennial or Bust

Post by rkcarguy » Fri Apr 13, 2018 10:11 am

I really liked the way bigdumbdinosaur did them on his F-7, He used spherical bearings and then mounted bearings on bolsters behind the truck sides as "sliders" so that the trucks can articulate up and down independent to the springs, but not side to side. There is a lot of ways to do it, I feel this one was the best though as it doesn't allow any lean, but allows a lot of movement up and down(front to back) to tackle changes in grade like when you unload down a ramp from a trailer, etc.
Being you are building a lighter locomotive in a smaller scale than I am, a couple 1/2" self aligning pillow blocks should do the trick at the pivot pins. These are plenty cheap on Amazon.

rkcarguy
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Re: SP NG Diesel #1 (GE 50T) - Triennial or Bust

Post by rkcarguy » Fri Apr 13, 2018 10:53 am

https://www.amazon.com/KFL001-Aligning- ... ed+bearing

These are 12mm metric self aligning bearings. Just bolt them to your bolster and provide a through hole, then bolt to chassis with a spacer so it can pivot. Then, further out on your bolsters, you could use anything from a half round of plastic to ball bearings on tabs that "thrust" on the bottom of the chassis as the truck pivots. I can upload a sketch if it doesn't make sense.

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Re: SP NG Diesel #1 (GE 50T) - Triennial or Bust

Post by 0351 » Fri Apr 13, 2018 9:32 pm

rkcarguy, please upload your sketch. I'm curious of what you've came up with using these bearing on bolsters.
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rkcarguy
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Re: SP NG Diesel #1 (GE 50T) - Triennial or Bust

Post by rkcarguy » Sun Apr 15, 2018 1:35 am

Ok, will do. Probably be Monday when I'm back at work.
A better explanation, is that when you look at the common truck, the bolster pivot has a wide flange area which doesn't allow any movement to suit changes in track elevation. The truck stays flat to the rolling stock, and only the springs allow the wheel sets to move. That's fine for full size, but when we have far more steep grades and ramps to deal with when loading/unloading from a truck or trailer, it's quite different. The typical design for backyard trains is similar, if you look at Island Pond RR's site for example, he sells different spring weights for different weights and loading of rolling stock under the same premise. Light springs absorb the bumps well and allow the truck to tackle a grade change, but bottom out with more weight. heavy springs can cause a derailment, because for instance, when you were to unload your trains from a trailer, as the first wheel set crested the end of the trailer and started onto the ramp angled down, the front wheel could raise off the track and cause a derailment. The wheels aren't loaded evenly on uneven surfaces as well, causing more problems with wear and potential derailing on riding cars when they are empty vs. full. The stiffer the springs selected, the worse it's going to be.
What is needed is to allow the truck to be able to pivot independently, so when viewed from the side of the train the ends of the truck can move up and down besides just the movement offered by the springs alone.
Imagine using a round bar for the bolster, a spherical bearing and bolt as the bolster pin, with the round bar being greased and contacting a large area on the bottom of the locomotive or rolling stock, and be able to not only pivot on the bearing/bolt, but pivot back and forth somewhat allowing the truck to level itself to the track condition while still evenly loading both wheel-sets. Likewise, leaning will be limited only to the travel of the springs, and springs can be stiffer to take heavier loads and still stay on the track much better.
Hopefully that makes sense? It is similar to the way the linkage works on a tandem axle trailer. When done properly, the center linkage at each end of the leaf springs pivots in the center, allowing both axles to take the load fairly evenly even if the hitch height is wrong and the trailer is much higher at the front or back. Done improperly(without this linkage), the trailer would have to be perfectly leveled, or would overload one axle, and on grades one axle/tires could come completely off the ground.

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