Recent content by Whymars

Actually gluing them in is a great idea. I hadn't really thought about that before because I've been consciously avoiding a messy sort of build process, but the right amount of the right glue would be ideal, and would look great too - could dispense with fasteners on the outside entirely...

Hi folks, thanks for thinking about this so carefully! The bolts in this prototype are M4, and the holes are... a bit bigger... I believe I would have used a 4mm drillbit in the first instance, but I also remember playing fast and loose with the needle files at some point. This one is a...

Hi nvn, that might be a good plan - although it will mean that when the arm is upright, and any bend disappears then the arm will then be biased to roll right over. In practice this won't be a problem as there'll be a mechanical stop on the pivot so it can't, and in any case, I'd like it to...

Hi nvn, I'd moved the cw back to it's old position already - it still exhibits the horizontal stability, albeit more gently. Looking at the arm along it's length, even with it screwed up tightly, there is still a visible slight bend in it though, partly a property of the material maybe, but more...

nvn, phrak and QGoest, thanks for all your help here, very very helpful indeed. My aim with the structure was always to go for a finger-tip sensitive neutral equilibrium - able to be posed upright or horizontal and any point inbetween (and at any extension). On reflection, I suspect this ideal...

Intuitively, I did think that the counterweight should be in the centre of the mass. But if it's right at the end instead, that'll move the centre of mass for the whole arm towards the end - but won't that centre of mass will still move in the same proportion as if it were in the centre? I...

I did think that would be ideal, but then couldn't decide if there was any geometric difference in having the cw at the end, and it's certainly preferable to have a lighter weight if possible. I guess this is why it balances a little more stably with the cw lower down, I hadn't really...

Hi nvn - Each segment is cut from identical plans, but only by hand so there is some inaccuracy. The main problems with this model is that the holes have been filed out slightly too large for the bolts, and the hardboard is fairly thin so the bolts aren't inclined to stay very perpendicular...

Thanks very much Q_Goest, that's outstandingly helpful - I've already trialled the counterweight in a different position (where there happened to already be some holes, fortunately), with enlightening results! New placement (was through the metal pivot hole previously) Fully extended...

Thanks Lok, but if the beam is horizontal, isn't gravity acting equally on both sides? I don't want to be able to pose it at particular angles, just to try and understand what makes it tip from horizontal when it gets shorter. I've resisted using friction in the design so far because [it...

Hi guys, I'm working on a prototype for a lamp and have quickly overreached my meagre school boy mechanics skills, almost at the first hurdle, in fact. Embarrassing, I know, but hopefully some kind soul here will be able to point me in the right direction. A picture is worth a thousand words...