30mm rail for Y axis - lowrider CNC?

finalizing my BOM for my 4x10 full-sheet lowrider (note that’s 4x10 sheet good - so i need longer than 10’ Y).

Turns out I can’t get 20ft EMT sections without a hefty shipping fee; but I found these two options locally. They are essentially the same price, given I just need one. Both are ERW

  1. ~30mm (1 1/16") OD, 113 wall, galvanized
  2. 1" OD, 083 wall, cold roll mill finish

Obviously I don’t need something an ~eighth of an inch thick :slight_smile: but want the galvanized. Any reason I can’t get the printed parts working with 30mm? How exact does it need to be (IE is it mandatory I get it in-hand before printing)?

For Y, I could squeeze both ~5ft sections out of the 21 footer the 30mm comes in, but they’d be twice as heavy as 1" EMT). I assume I should still plan on using 1" EMT for the X axis to minimize weight? Note for future people - both of these are about the same price per foot as EMT from homedepot, when purchased in 20ft from a metal supplier.

ETA: perhaps I could just joint sections of EMT? With some finness that could be made into a very smooth joint at least compared to EMT tube as a whole?

Normally the Y axis is the longest axis. Having a X rail longer than 10’ is unheard of (even 5’ is pushing it).

The Y rail can be as long as you want (within limits of the table length and available rail material), and doesn’t require the strength that the X rail does, so even 1/2” EMT could still work.

my mistake. Yes, Y axis. Post edited.

Sorry, but your post is a little confusing.

Using the LR3 Strut Calculator , you will need 2 pieces of 55" (4’7") tubes/EMT for the X axis, and 1 piece of 132.5" (11’ +1/2" minimum (you probably want an extra inch or so on the Y axis to allow for moving the core off of the work space, and a bit extra on the X axis can’t hurt either). That adds up to minimum 20’+2.5". Even assuming that your cuts are very thin and perfectly square (no wastage), and that you don’t allow for a bit extra on the Y or X axis, it looks like you still can’t get everything out of a single 20’ piece.

No, the LR3 is designed to use 3/4" EMT, not 1" (the dimension on EMT refers to the ID, not the OD). 1" TUBING can be used (tubing dimensions refer to the OD).

I suppose this is possible, but probably difficult to achieve IRL. If you do go this route, it might be advisable to use a 10’ section and a 14.5" (+) section, and place the joint at the Y Max end, as it would get less traffic at that end when cutting shorter pieces,

I can’t tell you why - but the galvanized 30mm comes in 21 foot. Typically it’s 20, obviously, which was why I used that elsewhere in the post - sorry for the confusion.

Thanks for the clarification. Sounds like HW store EMT for the X, regardless.

@vicious1 mentioned that he doesn’t have any stl’s for 30mm OD for Y … which is fair, but looking at the design it appears that I’d only need to modify two parts (??? the rail-block, and rail-holder) which wouldn’t be a big lift, especially if Ryan might share a parametric file for the latter for me to edit/test & contribute back. Are there other parts that require mods for 30mm Y?

If I could make the LR files fully parametric I would have. That is an extremely difficult task. Making boxes parametric is easy. Making a full assembly is not easy and if I could it would only fit a small range of sizes.