Moving forward from my last post Trail Finder 2 chassis modeling part 2 we can start to see some real progress. When creating these models, sometimes it seems like measurements seem to have a rubber band effect. I try to alleviate this issue by taking a measurement two or three times before settling on a real number. The chassis rails for this modeling project have been particularly elastic. I decided to scan in the rails and get the correct hole placement. Much to my chagrin I discovered I had a lot of rework to do.
There are three hole sizes that are used on the chassis rails. 4mm sized holes are for the leaf spring shackle screws. 3.2mm holes are, what I call, pass through holes for M3 screws. And finally there are the M3 threaded holes which basically measure 2.65mm in diameter. These are the sizes I have gone with now. Before, I was using smaller hole sizes which ended up compounding my hole spacing issues on the chassis rail. Coupled with the incorrect shape of the rail itself was a recipe for….. nothing that I was actually trying to create.
As a general example here is how “off” the shape of the chassis rail was. The lower rail is my first creation and the taller rail is the corrected version.
You might have begun to suspect that if I had to create a new rail, with new hole locations, I might have to do even more work with the other components for them to line correctly to the new rail. You wouldn’t be wrong in thinking that way. Lucky for me though, most of the items I created previously lined up exactly to the new chassis rail holes. With that refreshing discovery, I didn’t have to re-model all of the other parts. Just a few adjustments here and there and it all fit together as it should.
In paying closer attention to my digital caliper, while measuring, I noticed that if I forced the jaws to close tightly, presumably for a more accurate measurement, it would distort the slide rail slightly which would skew my measurement. Noticing this helped me get a much more accurate measurement from the parts. I also updated the transfer case to better match the shapes and alignments of the real one.
Another improvement was an increase in the number of segments in my circles. The default segment count, in Sketchup, is 24. I doubled that to 48 segments for most of the normal circle diameters for 4mm and smaller. For the larger circles I increased the segments to 72 segments. This gives a much greater smoothing effect on the circles. I updated the transmission mounts with more circle segments to bring it inline with the other parts. Things are progressing quite smoothly now that the measurements and alignments are as they should be.