Ideas for making an etched part

[peteski]

It'll be interesting to see what the final solution is.

[Lemosteam]

I think your cardboard mockup closely captures what I would like to achieve.  I'm still unsure of the best approach for doing the folds.  Usually it would be done with a half-etch line on the back of the metal, but trying to model the corner angle irons of the proto which are around 3-4 scale inches means that the parts would be around 0.020" on either side of the etch line.  That's pretty small to get a grip for forming.

One possibility might be a mini bending brake like this one from Micro-Mark:

http://www.micromark.com/mini-bending-brake,6702.html

I don't have one on hand to try out, tho it does not seem to me that this tool is designed to work with metal parts of such small size as we are talking about here.  Even if the die were fine enough, there still seems to be the problem of accurately positioning the part for forming.

The other consideration is that a half-etch fold line on the back would preclude the possibility of etching raised details on the front side of the metal.  Aesthetically I am not sure that having finer parts devoid of visible detail would be much of an improvement over the factory parts (at least not enough to justify the work it would take). I guess the only way to find out is to etch up some test parts and see how it works out.

@ednadolski
You could make the ladders separate and the fold lines wouldn't matter, because the base cage would be symmetrical.  Then half etch the ladders with rivets and CA them in place on the cage.

I use this with good success on phosphor bronze with 1mm wide flanges to hold.: 

http://www.amazon.com/Small-Shop-Photoetch-Bending-5-Speed/dp/B00QHCWGIY?ie=UTF8&psc=1&redirect=true&ref_=ox_sc_act_title_2&smid=A2AQEEYD5Z5W05



With this mod for better grip on long thin flanges:
https://www.therailwire.net/forum/index.php?topic=39348.msg480398#msg480398

[ednadolski]

You could make the ladders separate and the fold lines wouldn't matter, because the base cage would be symmetrical.  Then half etch the ladders with rivets and CA them in place on the cage.

Say, I think you might have given me an "ah-ha!" moment here! A separately-etched 'frame' piece, with the three ladder pieces subsequently glued on, does sound like an intriguing possibility.   It could perhaps even do away entirely with the need to make long folds or solder any parts.  I'll definitely make up some pencil sketches to help me further think this through.

That's also a very interesting improvement you've made to the bending tool.  I have the small "Bug" version which has a single knob. But now I wonder if that could be part of the problem, since having only one pressure point might possibly allow the work piece to lift or slip ever so slightly during the forming.

Thanks for the great ideas!   

Ed

[tom mann]

I would love to see a new end cage made with delrin plastic (what MT uses).  Maybe your design can be made by MT as a replacement part?

[peteski]

I would love to see a new end cage made with delrin plastic (what MT uses).  Maybe your design can be made by MT as a replacement part?

The big problem with Delrin is the coloring.  Because paint doesn't stick to it MT molds them in the color of the car.  That is not something which would be feasible if those were sold as separate parts.  There are just too many color variations out there.  Well, you might be able to get some paint to stick to it well enough to make it viable, but they between the primer (adhesion promoter) and a layer of paint you are probably covering up all the fine details.  Plus even then the paint still is not as well adhered as it would be on a polystyrene or ABS part.

[ednadolski]

@tom mann, i am wondering -- why delrin?  I'm sure it could get some better dimensionality but in addition to the paint issues as @peteski mentions, I am not sure that it would be very durable the closer you get to scale sizes.  The NRE/tooling would easily make it infeasible cost-wise (4+ figures I'd guess), and making it to proto dimensions would probably preclude most commercial couplers/pockets.  Also, if HO handrails are any indicator, it is susceptible to warping/distortion.

Ed

[Lemosteam]

Say, I think you might have given me an "ah-ha!" moment here! A separately-etched 'frame' piece, with the three ladder pieces subsequently glued on, does sound like an intriguing possibility.   It could perhaps even do away entirely with the need to make long folds or solder any parts.  I'll definitely make up some pencil sketches to help me further think this through.

That's also a very interesting improvement you've made to the bending tool.  I have the small "Bug" version which has a single knob. But now I wonder if that could be part of the problem, since having only one pressure point might possibly allow the work piece to lift or slip ever so slightly during the forming.

Thanks for the great ideas!   

Ed

Ed, thanks for the kind wors and you are welcome.

While the bearing area under the knob grew quite a bit, that is not the reason I changed to the larger knobs.  It is the torque I could apply with them.  The small knobs were ripping my hands apart.  Also I found that the Bakelite knobs would stick when trying to loosen them.  The nylon washers help tremendously with this.

[tom mann]

@tom mann, i am wondering -- why delrin?  I'm sure it could get some better dimensionality but in addition to the paint issues as @peteski mentions, I am not sure that it would be very durable the closer you get to scale sizes.  The NRE/tooling would easily make it infeasible cost-wise (4+ figures I'd guess), and making it to proto dimensions would probably preclude most commercial couplers/pockets.  Also, if HO handrails are any indicator, it is susceptible to warping/distortion.

Ed

I only suggest it because it's super flexible and forgiving.  I was thinking that MT stirrups are finer, so it would work out.

[John]

coat delrin with a silver sharpie, then paint it anything you want

[ednadolski]

Here is a (very!) quick hand sketch.  Part D would be the 'frame', etched as full-thickness metal.  The two side tabs and the bottom coupler support bracket are meant to be folded 90 degrees to make the base shape.   No difficult forming here, this should be doable with a decent set of pliers.  Note the tabs on the ends for attaching the frame into holes drilled in the plastic carbody, there are 6 attachment points in this drawing.

Parts A, B, and C are half-etch for the ladder frames and full thickness for the ladder rungs.  It may also be possible to half-etch the rungs from the back to get a finer appearance.  These should glued onto the frame, part A first and then B and C.  Again, no forming, other the cosmetic angle bends for the stirrups.  Note that I also left some holes for installing a brake platform and drop-style wire grabs.  Part E is the coupler adapter which goes on from the bottom. (I may want to eliminate the coupler pad on part D, as it seems redundant.)

This sketch is for the A end of the car, but the B end will include a place to mount the brake equipment (wheel, housing, and chain).  It may be preferable to assemble the cage first and paint it before attaching to the car, at least when installing on a factory painted model.

I'm initially envisioning this as etched on 0.010" phosphor bronze, mainly since I expect to have room on an etching that I currently have in progress.  That should at least help to get the dimensions right.  Ultimately it could be done in 0.005" stainless steel which should allow the rungs to be made pretty close to scale size.



Thoughts?

Thanks,
Ed