Custom chassis fabrication?

[mike_lawyer]

In a mill it could probably be cut and then each end faced and pinned to set the axle centerlines perfectly.  Maybe even be done by machining to insert an axle set in one of the center positions if there was a benefit to maintaining the chassis end features.  But what about the rest of the components?  Drive rods, valve linkage, etc.

I have plenty of extra valve gear, wheels, cylinders, etc. in my parts box, so that isn't really an issue.  If I can get the frame set up right, I should be good to go.

[peteski]

But what about the rest of the components?  Drive rods, valve linkage, etc.

Best way to do those in larger quantity is photoetching (stainless steel).  That is how the Mikado rods are made.  The "real" model companies also sometimes make the running gear from pressed steel.  Things like the crosshead are usually diecast metal or injection molded plastic.

[narrowminded]

I have plenty of extra valve gear, wheels, cylinders, etc. in my parts box, so that isn't really an issue.  If I can get the frame set up right, I should be good to go.

Send me some parts and I'll see what I can do.  

I'm finally getting my machines ready to run again.  They've been down for home and vacation issues and I still have to devote some time to my lady with some doctor and hospital runs for a hip replacement and some back issues so it may not be immediate but should be able to get it in between duties.

[motofavorite]

I bumped into this Kato conversion the other day. A mikado into a pacific?

https://www.trainz.com/collections/all/products/kato-126-0202-n-scale-erie-heavy-mikado-steam-locomotive-tender-ex-box?variant=39631060959354

[mike_lawyer]

I bumped into this Kato conversion the other day. A mikado into a pacific?

https://www.trainz.com/collections/all/products/kato-126-0202-n-scale-erie-heavy-mikado-steam-locomotive-tender-ex-box?variant=39631060959354

Looks like a Kato C55 Pacific with a Mikado shell and tender added. 

[JMaurer1]

When are 3D scanners going to drop in price like the printers have/are? A small 3d scanner is still over $800 minimum. I would probably have a 3D printer if I could just scan something (say, an HO boxcar) and shrink it down to N scale and print it out (even though I'm an IT by trade, learning how to run those CAD programs is just intimidating...the want is there, but the reality of actually DOING it isn't). Being able to scan the frame, cut and paste the extra driver slots into the file and printing it sounds simple.

[Lemosteam]

When are 3D scanners going to drop in price like the printers have/are? A small 3d scanner is still over $800 minimum. I would probably have a 3D printer if I could just scan something (say, an HO boxcar) and shrink it down to N scale and print it out (even though I'm an IT by trade, learning how to run those CAD programs is just intimidating...the want is there, but the reality of actually DOING it isn't). Being able to scan the frame, cut and paste the extra driver slots into the file and printing it sounds simple.

@JMaurer1 , For fear of beating a dead horse, see the following response to a similar thread:

https://www.therailwire.net/forum/index.php?topic=43699.msg558296#msg558296

Nohting beats a pure CAD model for accuracy.

[Kentuckian]

I recently had some dental work done, a tooth replaced. They made a 3D scan of my teeth by passing some sort of small scanner over them several times. Then they worked up a CAD model of my teeth, including I presume the gap where the old tooth was. Then a CAD model was made of the replacement tooth, and it was 3D printed. When installing the temporary tooth on the implant post, they still had to test fit and hand file about three times before the doctor was satisfied. All this in about 45 minutes.

After a few months of healing I will get a milled zirconium “permanent” tooth. But my point is that 3D scanning, modeling, and printing cannot meet the sloppy tolerances of a temporary tooth yet.

[peteski]

I recently had some dental work done, a tooth replaced. They made a 3D scan of my teeth by passing some sort of small scanner over them several times. Then they worked up a CAD model of my teeth, including I presume the gap where the old tooth was. Then a CAD model was made of the replacement tooth, and it was 3D printed. When installing the temporary tooth on the implant post, they still had to test fit and hand file about three times before the doctor was satisfied. All this in about 45 minutes.

Teeth are organic shapes. They are uneven and undulating. Lots of bumps and valleys.  No straight edges, large flat surfaces, complex but smooth curves, sharply angled window openings, rivets or seam-lines, etc.  3D scanners work well with organic shapes, but if you try to scan a model boxcar or a loco, they will not do so well.  Just like what Lemosteam mentions, a 3D scan is not ideal.  Even cleaning up the scan manually would probably take more hours than drawing the object from scratch (just using its known dimensions).  But if you want e 3D scan a human, or some larger fantasy game miniature, and shrink them to N scale, that will work ok. Again, organic shapes.

Few years ago, my dentist had a 3D scanner which scanned the teeth inside of my mouth to make a crown.  It was basically a wand with a camera, and a sophisticated software to stitch the 3D images into a 3D scan.  He had to take dozens of photos (while looking at the screen which show him how to line up the next photo.  It was cumbersome, but very hi-tech and impressive. Then once the 3D image was created and edited, it was sent to a CNC type milling machine made just for making crowns, which milled the crown from a piece of crown material, Once that was done and test fitted, the crown was then fired in a kiln, to harden it.

But when he made another crown for me last year, he was back to making rubber impressions  of my jaw. When I asked, he said that the in-mouth 3D scanning was not accurate enough, plus it took too much time.  Now he sends those tooth molds to a lab. There they place them on a stationary 3D scanner, then the rest of the process is like you describe.

[mike_lawyer]

I am thinking that maybe trying to splice Kato Mikado frames together might be the best way to go about this.  The question is how to cut the frames to splice together.  I would be very open to suggestions on that.

[narrowminded]

Cut in a milling machine.  To assure accuracy, a clamping fixture with precisely positioned pins that locate the chassis by axle bearing pockets with all following cuts measured from those locating pins.  A lengthwise machined pocket with an inserted and pinned stiffener spanning both parts may be helpful too but the basic idea of referencing everything from the axle pockets would remain.  Those axle pockets are the critical dimension as I understand it.  What I don't understand at this point but could, is whether additional gear pins or gear pockets are required internally or if the whole chassis is to be lengthened by one axle position or simply the addition of one axle pocket to the existing chassis length.  The final details could change the method used but the basic idea of fixturing/ referencing from the axle pockets would remain.

[narrowminded]

OK.  I finally found some pictures that show one of these exploded and with enough detail to develop some ideas on what may be done.  Of course, this assumes that the firebox location as it is, relative to the back axle, would be nice to maintain.  This requires two chassis' to get the required pieces.

A cut ahead of the last axle and just behind the second to last axle that removes the back of the chassis at that point, also right at the front end of the motor pocket, would remove that section and be discarded.  Then the second chassis is cut ahead of the second to last axle position at a dimension that maintains the axle C/L positions, will afford the extra axle while maintaining the pins and such to gear drive that final axle with original parts.  This can be done because it maintains the idler gear pin and position relative to those two axles.  Also, the original motor mount pocket in the rear section and the worm bearing pockets in the forward section are retained intact.  This retains all of the Mikado's original components and positioning except for a straight forward extending of the universal/ driveshaft between the motor and worm. 

This, of course, assumes that this approach has the desired features and that what appears to be doable actually is with pieces in hand and the last few thousandths are encountered.

This picture helps to see the parts requiring cut and splice.

http://murfjunction.com/pages/trainlayout/nscale/DM8A3258.jpg

This links to an extensive series of pics that reveal a lot more of the component detail.

http://murfjunction.com/pages/trainlayout/nscalesound.html

[mike_lawyer]

Yup. That's the way i do it anymore. It's easier for boiler fitment.

So it sounds like hacking and splicing two Kato Mikado frames together might be the easiest solution here.  Do you have any pictures of how you accomplish this and keep everything aligned?  I would really appreciate any insight on this.  Also, when you splice the frames together, do you just glue them together with epoxy like JB Weld?

[Lemosteam]

Although I have spliced minitrix frames in the past using hand cut and spliced pieces, I would not recommend doing this by hand on this chassis.  @narrowminded has mentioned and I agree, that accurate machining of these frames and subsequent reattachment of the frame pieces is crucial to the operation of the model, as you discovered just when adding blocks behind the fourth axle to make a fifth axle pocket.

[mike_lawyer]

Although I have spliced minitrix frames in the past using hand cut and spliced pieces, I would not recommend doing this by hand on this chassis.  @narrowminded has mentioned and I agree, that accurate machining of these frames and subsequent reattachment of the frame pieces is crucial to the operation of the model, as you discovered just when adding blocks behind the fourth axle to make a fifth axle pocket.

I agree, I was not intending to do this by hand, but rather with a milling machine.  I was just curious how @draskouasshat went about cutting the frame, specifically, which cuts did he make and how did he keep everything aligned?