Positioning Y rail blocks - for new makers building LowRider v3

LowRider CNC Advice
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I shared the following details in a private conversation with a maker building his own LR3, and thought it might help others too, to better gauge where to position your Y rail blocks for your given table situation.

So, one crucial bit of dimension to know, is the distance taken up by the linear guides (that are attached to the YZ plates) and their slide bearing trucks (that are attached to the XZ plates). If those items are all according to spec, the total for them as a set, should be 13mm. (You could measure in the real world to confirm.)

Once you know that number, you can get the sum of YZ plate thickness x 2, XZ plate thickness x 2, gap of 13 mm between those two plates x 2, plus your proposed tube length, to get an overall number. For instance:

YZ plate thickness = 12.7 mm x 2 = 25.4 mm
XZ plate thickness = 6.35 mm x 2 = 12.7 mm
Gap of 13 mm between those two plates = 13 mm x 2 = 26 mm
Proposed tube length = 1422 (or 1425) mm.

Thus, using 1422 it would be 1486.1 mm.
Or, by using 1425 it would be 1489.1 mm.

The above would be total width of your LowRider from outside edges of YZ plates. Does not include motor “stick out,” etc.

Another crucial bit of dimension to know, is the distance from the center of the Y rail to the outside edge of the YZ plate on that side. That number can vary based on the thickness of your YZ plate. It can be calculated by the “known” distance from the center of the Y rail to the inside face of the YZ plate, then add on the thickness of your YZ plate. The “known” distance from the center of the Y rail to the inside face of the YZ plate = 26 mm if my 3D modeling mockup of the LowRider is correct.

Armed with this, you can then layout your location for the Y rail blocks to be attached.

PS: because I do a lot of remixing and mods, I dropped almost all the printable models of the LowRider into SketchUp and arranged them to resemble an assembled LowRider. This has been invaluable to me.

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thank you for that. I will for sure keep that in mind and probably come back for reference

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I get ypur math…but personally, I don’t care about the outside edges of my YZ plate.

The Y belts are positioned based on the inside edges of the YZ plates for everyone, save possibly those using your hidden belt modification. I care about distances from the belt mounts for positioning things. I can see where you get your math, but from your exame, thst 25.4mm for the YZ plate thickness doesnt matter. What matters instead is the offset of the belt from the inside edge of the YZ plate, which is a fixed value. (Which I don’t remember, but I did work it out at some point.) This is why I could replace my YZ plates without moving any other fixtures, though I did need to move the belt mounts when I replaced the XZ plates.

For those with a standard build, the outside of the YZ plates is of no consequence, it is only for the hidden belt mod that it matters, because the hidden belt mod mounts the Y lotors to the outside of the YZ llates. The standard build uses the jnside of those plates as the reference edge.

I would be more incluned to use the hidden belts, but unistrut is a royal pain to get here, and the exposed belt isn’t a real issue for me.

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Good points as always

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My thinking here (which is sometimes outside the box) about the width of the LR3 is just to help new makers get a handle on the width of the total assembly as compared to their table, to help with a sense of understanding placement of the Y rail and understanding where the placement will position the 608 bearing wheels on the far side.

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you’re in luck. for the low low cost of my plane ticket, I’ll bring as much as you would like to your door.