Recent content by massta

Pipe/beam: OD: 2in ID: 1.87in Length between simple supports: 258in Total weight/load: approx 80lbs (includes all materials) or 0.2899lb/in L = Length (258in between supports) E = Young's modulus for steel material (30,000,000 psi) I = pi/64 * (OD^4 - ID^4); I = 0.18514in^4 Deflection: d = w *...

This idea is great. By deflecting the ends with a special bracket, it will put an opposite deflection in the beam. When the beam has a load it will straighten out. Only problem is the beam will bow when the screen is unrolled, so better to make it as stiff as possible. Going through the...

I'd like to see your formula. The only support is at then end, I understand the force is even throughout the beam but it only has one support so the entire force (or 1/2 because there are two supports) are enacted here. That said, all of the weight isn't at the middle, it's spread out. So this...

@rollingstein, you are correct. I made the mistake of using a solid beam. For hollow tube: I = pi * (OD4 - ID4) / 64 Where: pi = 3.14159 OD = the outside diameter (2 in) ID = the inside diameter (1.87 in) so I = 0.185142 in^4 plug in new I for Deflection: D = (F * L^3) / (3 * E * I) D = 5.11...

I just found this company and it's 4" aluminum pipe with 0.5" max deflection: http://www.phototechinc.com/102612_pwrroller/102712_pwrroller.htm costs $400 plus another $175 shipping, ouch Wish I thought of the rigid foam idea, just don't want to waste any money building another tube and...

Moment is force times distance. My thinking is because it's supported at both ends, I can run math for half of the beam. But what is my force? Weight: Support to middle of center pipe: 10.75' x 1.343lb = 13.43lb One coupler: 1' x 2.73lb = 2.73lb Outer shell: 10' x 1.2lb = 12.0lb 1/2...

Second attempt will be similar but with an axle pipe running the length of the tube. I'm nervous this will deflect also. Here are my drawings of the stages to completed. Basic drawing: This might be the easiest place to start. The screen only weights 23lb total and will be even across...

This is a real world project. I'm building a giant roll-up window shade to be used for a special effects green screen. The first real model attempt (without math) failed. See the two pictures of the tube structure being held up by chairs. The only axle was about 3ft of 1.5" pipe at each...