Roller Coaster Gantries
- kinematic mounts are three button head cap screws on 20mm grid w/ reciprocal / wherever-u-like mount ins
- all axis have scroll-along top plate w/ connection to motor plate, final scroll kinematic triangle
- all axis have scroll-along bottom beam plate w/ 20mm grid w/ last scroll kinematic triangles
BOM
Hardware
| Type | Size | QTY | Where Used | McMaster PN |
|---|---|---|---|---|
| SHCS | M3 | 2.5mm Hex | 91292A110 | |
| SHCS | M4 | 3mm Hex | 91292A116 | |
| SHCS | M5 | 4mm Hex | 91292A124 |
| Type | Meaning |
|---|---|
| SHCS | Socket Head Cap Screw: machine screws with hex heads in a 'socket' - i.e. the head is the socket, not the driver. |
| FHCS | Flat Head Cap Screw: similar to SHCS but have triangular heads, used when making fastener surfaces flush. |
| BHCS | Button Head Cap Screw: rounded head socket heads ! |
| PLSTCF | Plastic Thread-Forming Screws: have triangular lobed threads and torx drive caps, wonderful in plastics as the beefy threads mean no inserts required. |
OLD DOC: move this to /kunits/README.md and /kunits/images
Scratch / Landing page for the roller-bearings and 2d-sheet-stock axis system.
With RCT, we break axis into individual kinematic elements - and roll those elements into machine designs.
A reasonable system for beginners, and easy to manufacture (with another CNC mill). Particularely, this system begets the Madison Park Vocational Machine
Building Axis and Machines from 'Kinematic Elements'
Machines are made of degrees of freedom, and those degrees can be assembled from 'Kinematic Elements' i.e. here I have one Motor / Pulley Unit, as well as Lateral (into the gantry) and Cross (across the gantry) supports. I'm doing a mediocre job of explaining this, but here are some images:
To scratch a machine together, I pull elements into Rhino as .step files, and lay them out into axis - here's one linear degree of freedom:
Then I assemble those axis together, keeping track of where I'll be adding plates of material:
Then I go about filling in detail design, adding tabs etc to bring beams and chassis together.
Fabricating Axis
I then mill these axis on our shopbot, or any CNC mill you like - the N17 size elements can likely be laser-cut with acrylic or similar (delrin would be nice, but is expensive and a bit toxic to cut, so goes the lore).
I do CAM in Fusion with a .step I export (after flat-packing) from Rhino.
Assembling Axis
I typically assemble machines one axis at a time. That's not saying much, but here's an image to get a sense of how the hardware goes together:
The 'adjustable' elements use a captured nut to pre-load bearings against gantries. TODO is better documentation of this, but here's an image of the flexure in simulation to get a sense for what I mean:
CAD for You
RCT Elements NEMA17 Size
CAD For these elements is available in the repo cad/elements/rctElementsN17
This set assumes you're building with 1/4" HDPE or similar, Nema 17 Motors with GT2 Pulleys of 6mm width, and have access to a set of M3 Socket Head Hardware and 'MR115' or '5116' trade names or similar, 5x11x4mm. Lots of those.
RCT Elements for NEMA23 Size
CAD For these elements is available in the repo cad/elements/rctElementsN23
This set assumes you're building with 3/8" HDPE or similar, Nema 23 Motors with GT2 Pulleys of 9mm width, and have access to a set of M5 Socket Head Hardware and 'skate bearings' - 608ZZ or similar, 8x22x7mm. Lots of those.
Hardware Notes
! to add here
- hardware stackups, BOM, tuning note
Notes for Jake
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RCT Mod
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tabs on rail supports still no bueno
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std. order side-wall taps / wall-to-surface -
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of course the belt tensioning needs help ... fold-over or something ? glue it down? single track?
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belt tender assy - 3dp walls, bearings to hold-down, m4 screws on to carriage at edges ?
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motor rotational tensioning: pin one
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and make tools for drill, tap 3dp
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also drill / tap m6 / m4 verticals
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m4.3 or similar nice for m4 thru on motor
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order up tiny clampz
