Has anyone used a 3D scanner for RR parts? How well did it work?

Look at the top of the page and click on the 3D scanner catalog or do a search using 3D  scanner.

Gunny

Not that I am aware of.  There is some cursory info in this thread...

Affordable 3D Scanner Anyone??

For parts, some folks here do use photographs (not, photogrammetry)  converting raster images (.jpg, .png etc) into vector images and then adding dimensions to those vector images to properly scale the parts and save them as a 3D printable (.stl) file.   A vector image can be scaled without loss of fidelity.  If you have some good Hi-Res photos of your part this process along with any available dimensional drawings and/or a good set of calipers... you would be on your way to printing 3D parts

Depending on what you want to model you may be able to use a picture.  I've imported and top-down picture of a dummy coupler into FreeCAD (other CAD programs will let you do similar).  The picture included a ruler so that I could actually scale the coupler.  I set the scale and then traced and extruded the part.  At this point you could send it to the printer or add detail.  Below was the first attempt at scaling.

One thing to watch out for is parallax distorting the actual measurements.  The coupler was ~3/8" thick and if I laid the ruler on the table my part would be too large.  I shimmed the ruler so that the scale was level with the coupler top surface.   Obviously moving the camera farther from the object will reduce the effect but the loss of pixels on the object may be detrimental.

Jan

Jan, I've done the same thing to get a nice 2D model to start with, but the 3D scanner output would take our capabilities to the next level.  Imagine being able to scan and then print something complicated to do in 3D like a locomotive bell that can't be started in 2D from a photo and then extruded.  I'm interested in a scanner, but the problem is that they all *sound* outrageously good when you read the product descriptions, but I know that this is somewhat new technology and will require serious money (but getting cheaper every day) to get the accuracy that we need for our relatively small models.

Having never used a 3D scanner myself, I have a hard time understanding how a hand-held scanner would work well since you'd be wiggling the scanner around holding it and your scans would seemingly suffer as a result.  It might be time to buy a cheapie scanner that works with my phone and see what happens...low investment and an opportunity to learn.

Dale

This doesn't answer the question about 3d scanners, but there's nothing particularly complicated about a bell.  It's simply generated from a revolve of a 2d profile, rather than an extrude.  But I get what you are saying, complicated objects, usually meaning castings in my case, might be easier to recreate with a 3d scanner.  Of course you need to have the part to scan in the first place, which can be a problem in itself.  Something like this EMD jacking pad would have been a good candidate for scanning, with its compound curves.

For 3d scanning, I know that the Apple Ipads include some sort of scanning capablitiy, it may be Lidar.  Not an Apple guy, so only going on what I've read.  But I do know that Modelu in the UK uses an Ipad to scan real people and then turn that data into 3d prints for O scale figures and other items.  The items I've seen are quite good, so the technology must work fairly well.

Jim

This example is from eight years ago. I had to recreate a set of forging dies. These would be NC machined. The information to go by was a set of prints and a scan of an old set of the original dies.

The company that did the scanning used a scanner that cost around $45,000 at that time. It did a pretty good job but there was no easy way to convert the scan (a mesh) into solids at that time. The scan could only be used as a guide in recreating the surfaces and solids needed.  I am not sure if the software used today can do the the conversion needed.,

The good scanners are way too expensive. The less expensive ones are problematic as to the quality of the image.

At this point, if I don't have the actual model part, I get a nice photo and a few given dimensions and make the 3D model.

Sometimes, I work back and forth between a 2D program and a 3D program to make the model.

I would use a scanner if the cost was not prohibitive and it could produce a high-quality 3D model image,