Rostock Mini Calculations

I just printed out parts to build a Rostock Mini, but I'm confused about diagonal rod length. I decided I would just do the calculations myself based on scaling down the Rostock, but I can't find ay information about these calculations. Could somebody please point me in the right direction? I thaught there would have been spreadsheet calculators for this sort of thing.

Maybe because there is not much to calculate there at all.
Diagonal rod length is typicaly set to the value equal two times the delta radius.
But you can have diagonal rods longer or shorter.

Edited 1 time(s). Last edit at 10/11/2013 05:47PM by hercek.

i had the same question although i planned on creating my "own" design basically Borrowing from some of my favorite builds I particularly like the Cossel, Cerberus and 3DR versions of the Delta Printer. Planning on using Open V Slot extrusions. I want a large build volume like 300mm Diameter Plate. i haven't done the math yet but i'm sure i can figure out the triangle frame measurements. i am looking for the length of the diagonal rods and height to accomplish this.

If you want it simple put the diagonalRodLength = 2 * deltaRadius. This is the most simple case and if done so you get:
* the fully usable printing height of (heatBedToEndstopHeight-hotEndVertOffset-carriageVertOffset-diagonalRodLenght)
* the diameter of the usable print area is deltaRadius
* hotEndVertOffset is vertical distance between ball joint on the platform and the tip of your hotend
* carriageVertOffset is vertical distance between ball joint on the carriage and the end of screw which is going to activate endstop

Thanks for the information. Is deltaRadius the radius to the side of the base triangle, or the vertex?
For instance, just to make sure I am understanding you correctly, on an equalateral triangle with a side length of 10 units, the distance from the center of the triangle to any vertex is 5.774 units, which would be the radius. That multiplied by two would be 11.548 units, which would be the diagonal rod length.

Edited 1 time(s). Last edit at 10/12/2013 09:41AM by iVoid.

No, delta radius is computed like this (from Configuraiton.h file):

// Horizontal offset from middle of the printer to the center of line
// connecting centers of one tower smooth rods.
#define DELTA_SMOOTH_ROD_OFFSET 175.0 // mm

// Horizontal offset of the effector (platform) center from the center
// of the line connecting the effector universal joint centers (for one tower).
#define DELTA_EFFECTOR_OFFSET 33.0 // mm

// Horizontal offset of the line connecting universal joints on the
// carriage and the line connecting smooth rod centers.
#define DELTA_CARRIAGE_OFFSET 18.0 // mm

// Effective horizontal distance bridged by diagonal push rods (the delta radius).
#define DELTA_RADIUS (DELTA_SMOOTH_ROD_OFFSET-DELTA_EFFECTOR_OFFSET-DELTA_CARRIAGE_OFFSET)

I.e. your distance between triangle center and the tower center must by bigger by DELTA_EFFECTOR_OFFSET and DELTA_CARRIAGE_OFFSET (compared to what you assumed in your post).