I haven't used Tinkercad for a few years, but I really don't think it's an ideal program to be doing anything that is complex and requires precise measurements. While it's possible to do, other tools are much better suited to such tasks. Tinkercad works well for simple models that you need to put together quickly, but I've found it becomes clunky once you get much beyond that. Sorry, I don't have an answer for what you're specifically asking.
When building a model, you really want to start with dimensions, instead of figuring it out later. It can be hard to judge scale and proportion when looking at a model on a screen, so even if it looks right as you make it, you may discover that what you've spent a lot of time making will not fit a chassis or look right compared to other models in real space.
How far along is your model to completion? I hate to tell you to switch what you're doing, but I'd recommend exporting your project as an STL and transferring it to a mesh editor such as Metasequoia, which is what I use. Your existing project will serve as the overall skeleton, but using a mesh editor you will be able to measure distances between vertices precisely and you can move around vertices to correct your measurements. You also get the benefit of being able to use blueprints on all axis if you are basing the model off of technical drawings.
When making a locomotive, there's a lot of precision you have to consider regarding what mechanism you're using, and getting things like coupler mounting heights correct. This is a locomotive I recently built, an EMD GT26CW-2. I did all of the modeling in Metasequoia. If you're starting from the ground up, I would reccomend using a program that is more geared towards real-world objects, such as FreeCad or Fusion 360. I used Metasequoia because I had some existing mesh models that coudn't really be modified in FreeCad and the like.
-Peter. Mantua collector, 3D printing enthusiast, Korail modeler.
Have not done a loco yet, but it is on the list down the road. Here is what i have accomplished so far....
These tenders are one piece shells.
I use Sketch Up Pro to draw with, Simplify-3D to slice with, and the models are printed on a seriously hopped up ANet8. My apologies for the lousy camera work.
PMR
In the top right corner of the screen shoul dbe a ruler picture icon. click on that to get the dimensional ruler tool. to activate. place on the location you want to measure. click, hold and drag should give you the dimensional measurement you see on blue prints
SHane
A pessimist sees a dark tunnel
An optimist sees the light at the end of the tunnel
A realist sees a frieght train
An engineer sees three idiots standing on the tracks stairing blankly in space
It seems to me that drawing an item to specific dimensions is a pretty basic function of any CAD program.
I don't know TinkerCAD, but any program should also have a tool to measure a distance of a line/edge or between two existing points or parallel edges to verify a dimension.
Chris van der Heide
My Algoma Central Railway Modeling Blog
Also, check Youtube and FB there are some excellent tutorials on Youtube and you can ask questions in the comments section below.
Brent
"All of the world's problems are the result of the difference between how we think and how the world works."
Go to the tinkercad help forums and ask there. Every software is different, and you're likely going to find mroe help there than here.
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Modeling the PRR & NYC in HO
Youtube Channel: www.youtube.com/@trainman440
Instagram (where I share projects!): https://www.instagram.com/trainman440
I have been working on a shell for the past year on a platform called tinkercad but the only problem I have is I can't get it to show me the size and I dont know how. I am wondering if any of you guys have ever 3D printed a locomotive. Maybe you could help.