Photo Backdrop Clamp Pad Embiggening

We got a photo backdrop stand to hold Mary’s show-n-tell quilts during her quilting club meetings, but the clamps intended to hold the backdrop from the top bar don’t work quite the way one might expect. These photos snagged from the listing shows their intended use:

Emart Photo Backdrop - clamp examples
Emart Photo Backdrop – clamp examples

The clamp closes on the top bar with the jaws about 15 mm apart, so you must wrap the backdrop around the bar, thereby concealing the top few inches of whatever you intended to show. This doesn’t matter for a preprinted generic backdrop or a green screen, but quilt borders have interesting detail.

The clamps need thicker jaws, which I promptly conjured from the vasty digital deep:

Spring Clamp Pads - PS preview
Spring Clamp Pads – PS preview

The original jaws fit neatly into those recesses, atop a snippet of carpet tape to prevent them from wandering off:

Spring Clamp pads - detail
Spring Clamp pads – detail

They’re thick enough to meet in the middle and make the clamp’s serrated round-ish opening fit around the bar:

Spring Clamp pads - compared
Spring Clamp pads – compared

With a quilt in place, the clamps slide freely along the bar:

Spring Clamp pads - fit test
Spring Clamp pads – fit test

That’s a recreation based on actual events, mostly because erecting the stand wasn’t going to happen for one photo.

To level set your expectations, the “Convenient Carry Bag” is more of a wrap than a bag, without enough fabric to completely surround its contents:

Emart photo backdrop bag
Emart photo backdrop bag

I put all the clamps / hooks / doodads in a quart Ziploc baggie, which seemed like a better idea than letting them rattle around loose inside the wrap. The flimsy pair (!) of hook-n-loop straps don’t reach across the gap and, even extended with a few inches of double-sided Velcro, lack enough mojo to hold it closed against all the contents.

It’ll suffice for our simple needs, but …

The OpenSCAD source code as a GitHub Gist:

// Clamp pads for Emart photo backdrop clamps
// Ed Nisley KE4ZNU Jan 2021
/* [Hidden] */
ThreadThick = 0.25;
ThreadWidth = 0.40;
HoleWindage = 0.2;
Protrusion = 0.1; // make holes end cleanly
inch = 25.4;
function IntegerMultiple(Size,Unit) = Unit * ceil(Size / Unit);
module PolyCyl(Dia,Height,ForceSides=0) { // based on nophead's polyholes
Sides = (ForceSides != 0) ? ForceSides : (ceil(Dia) + 2);
FixDia = Dia / cos(180/Sides);
cylinder(d=(FixDia + HoleWindage),h=Height,$fn=Sides);
}
//----------------------
// Dimensions
OEMpad = [24.0,16.0,3.0]; // original pad
Pad = [35.0,25.0,8.0 + OEMpad.z]; // pad extension
PadOffset = [0,-3.0,0];
CornerRad = 3.0; // corner rounding
Gap = 3.0;
//----------------------
// Shape the pad
module BigPad() {
difference() {
hull()
for (i=[-1,1],j=[-1,1],k=[-1,1])
translate([i*(Pad.x/2 - CornerRad),j*(Pad.y/2 - CornerRad),k*(Pad.z/2 - CornerRad) + Pad.z/2])
sphere(r=CornerRad,$fn=6);
translate(PadOffset + [0,0,Pad.z - (OEMpad.z + Protrusion)/2])
cube(OEMpad + [HoleWindage,HoleWindage,Protrusion],center=true);
}
}
//----------------------
// Build a pair
translate([0,(Pad.y + Gap)/2,0])
BigPad();
translate([0,-(Pad.y + Gap)/2,0])
rotate(180)
BigPad();

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