Two suggestions, possibly both not practical😉 -Can you attach guy wires that run from an axial rod extended from each hinge point to the end of each truss to give a bigger triangular truss on each section? -Can you put a weight that is sprung from both sides out near the inside end of the last truss section to counter the bounce that is inherent in the structure, this may require some extended trial and error to get the correct weight and spring rating? Third suggestion, (very impractical, but seen used on movie camera booms), mount 3 gyroscopes in the X,Y & Z planes at the end of the boom.😁
A mass damper is something that I have considered. I wanted to get the basic structure stiffened up first; next on the list is the hinge. As fxm5715 says, it would not need to be much. I don't particularly want to guy the first section and statically it is not twisting as much now. My next step is a new design of hinge. The design on there hinges as I want it too but is too loose and sloppy (modified commercial hinges - not surprising in hindsight). If I can firm that up I may get rid of some of the bounce/ flex. Gyros are way too sophisticated for me. I've seen some of the gyroscopic camera mounts and they are rather spiffy. Some cameras now have an anti movement mode on them - if the bounce persists maybe that is the next step.
Hi Mike, it is a great looking device. Perhaps look into the polar moment of inertia of your beam components for vertical stiffness, either in the upper tie strut or on the lower member. A vertical gusset in some key places and maybe some "parliament" style hinges could give you the balance you need.
Thanks Dave. I had a look at parliament hinges but I'm after effectively 360 degrees rotation so need either 2 axis of hinging (like bar door hinging) or some schmick hinges that won't sag when set up like I have them. There is a plan in motion for doing that at the moment... As for calculating a polar moment of inertia, my head explodes just thinking about it. I know theoretically it can be done, but I have that many tubes running everywhere that even working out the location of the axis of rotation would be a challenge - because of the shape of the truss I suspect that it moves the further you get from the hinge. I might have to measure carefully and see if I can get it up on a CAD system to calculate that and go from there.
I have some comments on your aluminum welding, in my experience the issue you identified is correct that it is related to shielding gas. The gas lens smooths the flow of shielding gas, a dirty lens will cause turbulence drawing in air causing the contamination. I have also found that the volume of the gas is an important factor, as using a higher than necessary flow rate can introduce turbulence causing similar issues. gas flow should be as low as posable to provide the shielding necessary. I have also found that when issues start it is necessary to remove all of the contamination prior to resuming welding, as any contamination will causse issues even if you have all of the other factors correct. Also I don't sharpen my tungsten for aluminum, I form a rounded end on the electrode by creating an arc on a scrap peace of steel, the rounded end will make a broader arc and help flow out the edges on your beads. I hope the helps.
Thanks for those thoughts. I've run into the shielding gas flow one before, and with most of these, once you have the issue (and solve it) you can spot it quickly the next time. I must admit to being a bit lazy when it comes to removing prior contamination. The main reason I included that sequence was in case anyone viewing has had similar welds and could not work it out - I'm learning as I go and hope it helps others.
There probably is - if I were better at maths I'd be able to tell you what it is. In my case, frequency is a convenient way of showing increased stiffness.
Not exactly, because as you add stiffness you add mass, which is a natural dampener. Ran up against this little beauty in second year mech eng undergrad. A life of weapons and motorsport engineering has given me a healthy respect for resonance. The function is based on the square root of the spring constant(k) divided by mass(m). f=(1/2*pi)*sqrt(k/m)
@@GTRgeoff Thanks. I had a sneaky suspicion that there was a square root involved, but it has been many years since I've even thought about this stuff.
Sometimes stepping back prepared to ignore the sunk costs and re-evaluating can be beneficial mate, unless you want to keep throwing effort at it. Cantilever beams, especially open truss, can become a nightmare and ally isn’t a great damping material. Add stiffness and it bounces faster, add weight and it bounces slower as a rule of thumb, but you have to make conscious decisions to chase a resonant frequency beyond what it might encounter. Maybe strapping some carbon rods along the upper elements could crank up the tensile strength and damping, with little load added. If I ever decide to film in a workshop on a regular basis I’d put in steel landing pads above and use a monopod camera post with a magnet to attach. Make a huge Noga arm for your camera to hang from the ceiling 😂. Legit I wish my workshop was in action just so I could film that build myself.
Interesting idea - I was considering a gantry type mount, but it would need to have a 6m span in one direction, so getting pretty big. This was a compromise - I think it will work well enough with a bit more work. The Al was chosen for weight primarily, so yes, not the best for dampening.
@@occasionalmachinist I have to say I enjoy watching people learn by doing. Just the honest process of trying something and seeing if it’s better or worse than before.
A little bit of nit picking... you keep saying hundreds of Hz, Looks more like Hz to me - @4:00 1 cycle per second... Anyway, interesting regardless. cheers.
I'm just going off the numbers I could read on the display. The before read around 100Hz on the display. It's a bit tricky because the Al is reflective too and confuses things. I guess too I should be halving the frequency I'm reading as once cycle should involve an up and a down - that would take it to 50Hz. The main use of the tacho was to get a relative indication of the stiffness of the structure, which it seemed to do.
He has a hobby channel mate. Easy to mistake cycles per minute and Hz or cycles per second if it’s not your regular reference measure, and the premise was correctly applied as a simple reference tool of improvement in the desired direction. Maybe you should hop over to breaking taps channel and correct him. 😂
@@stustoys Yes. A Brain fade on my part, but as @GTRgeoff has pointed out, it was intended as a relative measure to determine improvement rather than an absolute number. In part I chose using a tacho like that just to show a simple way to assess relative improvement.
