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In traditional syringe pumps they are but in this design we may not need to.

this is the design.

On ‎Monday‎, ‎April‎ ‎9‎, ‎2018‎ ‎08‎:‎41‎:‎54‎ ‎PM‎ ‎EDT, MichaelAtOz <[hidden email]> wrote:

I presume the syringe is strapped down somehow?
Would a V shape be suitable, any radius (with parallel sides) will be held
in a V.

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 At this point, I'm lacking the concentration to follow through on my "discovery," but a preliminary drawing shows that the process of creating the part can be made parametric. If it doesn't need to be parametric, it's easier to make the drawing and pull the numbers off via the appropriate tool for the drawing software. I'm "building" this model by creating cylinders to be subtracted from the monolithic base. For practical purposes, the cylinders can be considered circles in this exercise. Picture the smallest diameter for the collection of syringes. You want the most support, but you don't want the C-shape of the cross section to impede insertion. That makes the end result limited to the diameter of that syringe. Any cross-section cut higher than the diameter becomes a "gripper" of sorts and may be beneficial, but impedes this calculation. It can be added later as a parameter sum of an arbitrary distance of percentage. The centers of the circles are the parametric aspect that currently escapes me. I know it's simple, but the pounding headache I have is preventing me from proceeding. What I have been able to determine is that the spacing of the center of the second circle from the first circle is the diameter of the second circle minus the distance of the chord of the second circle from its center, with the chord of the second circle being the diameter of the first circle. I've done math of this sort before and have found an abundance of formulae to solve for this result. Because each circle references the preceding circle, the primary formula should be iterative, allowing for as many circle stacks as desired. In the image above, I used syringe diameters based on arbitrarily taking the capacity and making those numbers diameters, only to manage a relatively proportional image. I found a  web page containing the formula   I'd likely use to pursue this as an OpenSCAD project. The "welded" version of the above diagram: -- Sent from: http://forum.openscad.org/_______________________________________________ OpenSCAD mailing list [hidden email] http://lists.openscad.org/mailman/listinfo/discuss_lists.openscad.org
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 > ...  spacing of the center of the second circle from the first circle is the diameter of the second circle minus the distance of the chord of the second circle from its center, with the chord of the second circle being the diameter of the first circle. ... Unless you want to get fancy, if you have circles with radius r_0 and r_1, then the z-distance between centers is simply sqrt(r_1*r_1 - r_0*r_0) since there's a right triangle. A (probably managable) issue with this design is that the position of the center line of the syringe then depends on the syringe size, so the other parts need to accommodate that as well. -- Sent from: http://forum.openscad.org/_______________________________________________ OpenSCAD mailing list [hidden email] http://lists.openscad.org/mailman/listinfo/discuss_lists.openscad.org
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 It's not the distance between centers, it's the distance between the center of circle 1 and the center of circle 2 minus the distance from the chord on circle 2 that has the diameter of circle 1, if the other aspects of the design are valid. I had not considered that the center line of the syringe has to be maintained, and the information from the OP doesn't give that indication. If it's necessary to maintain a common center, it would be easier to create a series of inserts/sleeves to secure each smaller syringe in the larger mounting hole. -- Sent from: http://forum.openscad.org/_______________________________________________ OpenSCAD mailing list [hidden email] http://lists.openscad.org/mailman/listinfo/discuss_lists.openscad.org