2off my prototypes have cracked, but now i know that the screws need to be replaced too.
The medallion needs to be held on with through screws and nuts, using the existing ones tapping into the medallion has meant that in the opening and closing of the legs my new parts all cracked at the corner, see highlite on pic, notice the lighter streak, thats a minor crack (this actually is visable on the main pictures, I just hadn’t noticed it had already cracked when pic was taken). The lug that the screw taps into cracks away form the main body at both screws.
Basically using the existing screws tapped into the medallion means that the lug where the screws tap into wants to stay sitting on the bracket but the rest of the medallion pushes away and cracks at the corner. I think even with radius in there after a while a similar problem would arise, it might be the threads stripping instead of cracking but the cause is the same. Maybe having longer screws that tap deeper into the main medallion body would help but i think thru screws is the correct way to secure this. By using screws that go thru the medallion and secured with nuts the whole medallion moves slightly when opening/closing legs but as the whole thing moves there are no material stresses generated.
I will keep opening closing legs etc and see if i can spot any stresses etc with the one i have on my stand, I think i have now solved the cracking problem so in theory it should be fine.
Attachments:
DogP: The strength seems good, its a chunky piece of material, some more pics of it removed from the stand included. (took with digi cam with a magnifying loop held in front for a v.close up view)
I do want to add a radius on the angled faces where the legs sit against when open, thats the potential weak point at the moment as its a sharp corner, any stress and it might crack there, putting in a radius removes the corner & the possible weak point.
Pocket: Its actually an engraving CNC machine, not really a mill but due to the size of the parts we can make the machine cut them, not that i can program the machine, I prepare the drawings in CAD and the operator imports them to his package and does the cutting.
The material: I agree 100% it should be black with red lettering. Unfortunatly to get black material would cost quite alot just for a small piece so I ended up buying a chopping board (don’t make black ones though), an inch thick, and then we machined off the top and bottom surface to get the medallion a bit thinner. Not sure exactly what type of material it is, some kind of Polypropolene is my guess, but it machines quite well. The engraving could be better, next lot should improve on that, use a flat face rather than point cutter for the lettering.
Once another batch is made i can work out a proper price for these, I hope it don’t work out too much as I really like the idea that these could resurrect quite a few forgotton units with broken stands.
