Villengineer
Gold Member
Re: Any ME\'s out there?
After reading through this here are some thoughts I had:
1) Make sure you stress calcs are for welded connections in your truss. Many truss formulas are based on pinned connections. This will probably change your results. Especially since you now will have shear forces to deal with in your welds/tube walls.
2) I see some issues with welded joints that you should address. With such a thin wall your effective weld is very limited. Additionally, do you have sections of tubing long enough to make half span? If not, you're going to have some butt welds that you will have to make sure are strong enough.
3) Since your truss is at an angle remember that the total deflection is the resultant vector of both your DeltaX and DeltaY.
4) If you do a physical test on a short section you will have to remember that while it's true that the deflection varies linearly with load, for a simple uniformly loaded beam supported at both ends, it varies by the length to the 4th power at the point of max deflection (half the length). Just throwing a short section together and loading it may not really tell you anything.
Again, I'm no expert in trusses, just some things I see as a guy who designs welded structures. I'd rely on your SE friend as much as you can.
After reading through this here are some thoughts I had:
1) Make sure you stress calcs are for welded connections in your truss. Many truss formulas are based on pinned connections. This will probably change your results. Especially since you now will have shear forces to deal with in your welds/tube walls.
2) I see some issues with welded joints that you should address. With such a thin wall your effective weld is very limited. Additionally, do you have sections of tubing long enough to make half span? If not, you're going to have some butt welds that you will have to make sure are strong enough.
3) Since your truss is at an angle remember that the total deflection is the resultant vector of both your DeltaX and DeltaY.
4) If you do a physical test on a short section you will have to remember that while it's true that the deflection varies linearly with load, for a simple uniformly loaded beam supported at both ends, it varies by the length to the 4th power at the point of max deflection (half the length). Just throwing a short section together and loading it may not really tell you anything.
Again, I'm no expert in trusses, just some things I see as a guy who designs welded structures. I'd rely on your SE friend as much as you can.