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Bodyshell wheelbase measurement

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  • Bodyshell wheelbase measurement

    This is easy when scratch building on a jig but for 3D or CAD purposes you need an accurate dimension.

    After eyeballing a few bodyshells to start drawing up a new 3D chassis and finding the finished print wasn't as accurate as I hoped I came up with this quick and easy method.

    I cut two short lengths of overflow pipe (21.5mm dia) long enough to sit a bodyshell on. The pipes automatically self centre as the tops of the wheel arches are usually the centre line.

    I measure the diameter of one pipe then zero the caliper then holding the body down firmly measure across the outside edges of the two pipes giving the perfect wheelbase measurement for the chassis.

    IMG_20200522_195318~2.jpgIMG_20200522_195407~2.jpg

    I should have thought about this a few weeks ago but it's been bugging me to find a solution... I like it! ????????

  • #2
    Nice to see someone paying attention to detail.
    Too many people built otherwise nice cars, then have the wheels/tires "off center" of the wheel well center. Ruins the entire look.

    Mike

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    • #3
      Or you can even do something like this
      This is a NSR Porsche just for fun.

      Partial_Scan.PNG

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      • #4
        Originally posted by Profoxcg View Post
        Or you can even do something like this
        This is a NSR Porsche just for fun.

        Partial_Scan.PNG
        What are you showing us here?

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        • #5
          A cool image just showing a different way to find the center of the wheel arch - provided you have reverse engineering capabilities.
          Aren't those your 3d printed bodies? if you have the digital file why are you measuring by hand?

          Partial_Scan_2.PNG

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          • #6
            That's a Team Slot Alfa Romeo Giulia GTAm body that I've designed a chassis for this evening.

            ...this method takes 10 seconds, you can't beat a physical measurement.
            Last edited by Kevan; 05-22-2020, 02:44 PM.

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            • #7
              Send me a PM. If you have more bodies I can probably help make yourr life easier.
              Nice work by the way.

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              • #8
                Given the choice I'd use Kevan's method.

                As Kevan mentions in the original post, there may be significant error taking the measurement from the CAD file. The final printed body may have some shrinkage or warp that would affect the wheelbase measurement. Taking the measurement from the finished product should be more accurate.

                The trick is to find tubing that is a close fit to the wheel arches. Faced with a sloppy fit I would wrap packing tape around the tubes to increase their diameter to a close fit.

                I suppose you could machine down an oversize tube if you have a lathe handy. Otherwise you'd best find a smaller tube and do the tape trick.

                The easiest solution may be to install a chassis with an adjustable wheelbase. Eyeball the adjustment. If it looks right it is right.

                Ed Bianchi

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                • #9
                  You are looking at 3d scan of a real NSR porsche. It doesn't get any more accurate than this

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                  • #10
                    Originally posted by Kevan View Post
                    That's a Team Slot Alfa Romeo Giulia GTAm body that I've designed a chassis for this evening.

                    ...this method takes 10 seconds, you can't beat a physical measurement.
                    I am not going to get into what is better or what is not, as every technology has its application and their goals. And yes I can beat physical measurements every time with a good 3d scan (btw what I showed is a draft) I agree that for your application that is probably way overkill and not something that can be justified unless you are a business making and selling parts at great volumes.



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                    • #11
                      If I was 3D printing bodyshells then yes the CAD measurement is obviously going to be accurate but for a bodyshell in your hand that may be 20+ years old you need an alternative method.

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                      • #12
                        ^ well the good thing is that at least your calipers are brand name and therefore accurate.

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                        • #13
                          Originally posted by Profoxcg View Post
                          ^ well the good thing is that at least your calipers are brand name and therefore accurate.
                          Had them many years too, from my toolmaking days when there weren't cheap copies available

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                          • #14
                            I think he may...have been referring to my comment about wheelbase accuracy.

                            Too bad people feel that they have to degrade positive comments for their own minimal satisfaction.
                            "If"...I'm wrong, I apologize to Profox.

                            Mike

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                            • #15
                              If you can measure wheelbase to within 0.2mm you'll not really see the error but that's only 8 thou'

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