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Great job using hand tools, Bob B)

The problem with that approach is the narrow ribs all over the sides and roof.
The spacing of those is 1.25 mm, roughly equivalent to 20 ribs per inch, and I don't think a hand tool can do that. I know I'm approaching the tool limit even for the CNC production of an extrusion die.

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1.25mm is about a .050 in. diameter mill bit, very common, not a problem to cut aluminum or in my case, Bondo.  Again, I would be making the mold out of resin and not aluminum, so making an extrusion is out of my league.  Bob.

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while I do have a plan, I'm certainly not ruling anything out at this time.


1.25 mm is the spacing or wavelength if you will. The ribs are approximately 0.45 mm and the space between the ribs is approx. 0.8 mm
Is this still feasible with a mold?

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I'm sorry, I had to go to a converter, I understand thousands better, so, .45mm equals .0177 inches, and .8mm equals, .0314, so if you were making the part for a pattern, a .0177 inch cutter would be needed, but if you are making the mold, then you could use a .0314 inch cutter and then the depth?  My choice would be to cut the mold and then make the part, because of using a bigger cutter, about a 1/32 in cutter. I just looked at an MTH O gauge super dome and it has 32 ribs, probably not to prototype, I think you said it should have 27?, anyway if they can do it in 1:48, 1:32 should be a breeze, Bob.

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Well, it sounds like it's doable then.
I'll run with the extrusion for now, but the project is still only aiming at fixing a total design cost. There's no guarantee it will be feasible in the end, so it's nice to have a plan B.

Thanks for the inputs, Bob. Much appreciated.

Jens

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Jens, I am trying to imagine how an extruder would work and correct if I am wrong, either the aluminum would be rolled with the proper dies, or a blade that would cut the shape. In the case that it is a cutter, the cutter would most likely be made on an EDM machine, electronic discharge machine and If it is, I don't think that the making of that tool would be all that expensive.  You probably already know this, but I thought that I would suggest it. If it were me, I would make my own extruding machine, but that's just me. Bob.

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OK, I went on YouTube and took a look at an aluminum extruding machine and I won't be making one of those.  I takes more machinery to straighten the extrusion after it comes out of the extruder, but I can see a row of 30 saw blades turning on a horizontal shaft, spaced accordingly, and moving the sheet through the cutters, maybe several times raising the work for each cut until the desired depth is achieved.  A horizontal mill would do the job.  Horizontal mills are usually cheap to buy and the saw blades are cheap.  A setup like that would probably cheaper than hiring someone else to manufacture the parts, just a thought. Bob.

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:D I'm trying to imagine an extruder in my house and the domestic discussions before that would happen.

Some years ago I visited Hydro Aluminium which is the largest manufacturer around here, and I got an idea about the possibilities and the pitfalls. As you say, the extruded parts must be stretched after the extrusion to even out tensions in the material. That means the die shape must be 2% larger in all dimensions because stretching a rod of course means the cross section gets slightly smaller. And don't even mention heating the aluminium billet to just below melting temperature before extruding it ...

No, I'm leaving the extrusion to the professionals.

 

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  • 2 weeks later...
On 4. april 2016 at 3:12 AM, enginear joe said:

Put that on a set of the correct trucks with bearings, and I'm in. Well,if you will sell?

 

How about trucks like these ?

 

truck1.jpeg

 

I'm not done with the design, but they're to scale, they're one piece and they're printable.

I have the NWSL wheels and ball bearings, and I'll make a test print as soon as the design is complete.

 

B)

 

Jens

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Doesn't matter, really.

I've picked my wheels, but there's a tradeoff.

 

On the drawings, the truck frames are of course designed for prototypical wheel flanges. When using model wheels you need to extend the end crossbars a little to allow for the larger flanges. This may not be needed if you're using fine scale wheels, but using the wheels I picked - the NWSL #28671-4, I need to move the crossbars on the design away from the prototypical dimension. If you're using even larger flanges, you need to adjust for that.

 

This is actually bad news, because (I think) the larger flanges are typically used on layouts with sharper curves, and bigger truck frames restrict the movement of the trucks, and thus the minimum negotiable curves of the cars.

This can probably be mended somewhat by designing the truck frames for maximum movement between the skirts of the car, and I'll work on that eventually.

 

When I'm done, my plan is to provide the CAD file for the trucks as a download, so anyone can adjust to their particular like of wheels and bearings.

 

Jens

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I'm running 14ft min curves outside and hope they'll make it. If not, I'd be willing to do some work. Just about everything I've bought in G scale needed some kind of work!

I'm excited to see these coming along. I'm hoping to be able to acquire some. I should get some more older SF engines to my rooster! Thanks for sharing the progress.

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That drawing looks fantastic. The smaller scales are spoiled. They've had stuff this detailed.

 Aristo's design had a weak area where the spring tension would crack the plastic over time and the truck would fail. I actually had one break and then wedge itself into a #6 switch. The train slammed to a stop. I wonder if their design loading the springs makes them worse off?

I only have two of their Amtrak passenger cars so I shelved them for now until I cast my own stronger version.

I'm excited to see how these trucks will roll. Easy rolling on long trains helps the plastic geared engines survive longer. The new Accucraft passenger trucks roll so easy they move around the layout to find the valleys on their own. I would love to have all my rolling stock roll so well. I'm more into reliability than exact details. Having both will  be fantastic!

 I don't know your final price on these but I'm hoping to run a decent sized train of them. For others as well, I'm thinking of adding a little extra weight to the MTH F series engines. I'd love to have a set of Es to pull that train. I have an area of the back yard layout that needs a cut to help lower the grade a bit. My engines are working too hard. I just added a set of MTH SF cars to the passenger train.

I'm more into reliability than exact details. Having both will be fantastic!

 

DSC_1564.JPG

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Looks nice. That concrete helps on weeding. Those are blocks you put down, or poured? A guy in Canada does that Aristo parrt that breaks on the streamliner trucks, it's a lot stronger. I replace mine with his part, but seldom run that set any.

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Done.

All the parts are now in place.

 

It still needs some spit and polish and I need to have a look at why some of the parts act up in the CAD modelling. I also need to strip some material on the inside to optimise the price.

It hasn't been tested for printability at Shapeways, but I've kept all dimensions within their recommendations, so it can't be much off.

 

Jens

 

truck3.jpg

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It does look great and I am drooling myself :D

 

But ... one thing is CAD and another thing is the finished part.

Can't yet say for sure what is possible and of course only time will show if the design is reliable in the long run.

 

Jens

 

 

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Here's an NSWL wheelset with the 10mm/3 mm bearings mounted.

Also a CAD rendering of the rear of the axle boxes on the trucks. I've made cutouts to embed the bearings and allow for the axle studs.

The idea is that the axles with bearings clip up into the truck and are held in place - but allowing for easy removal.

 

IMG_0274.JPG

 

truckrear.jpeg

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