Just thought I'd share a new joint I've designed, nice and simple hinge joint for better articulation on knee joints.
Simple 3 part system with silver soldered steel bars for 2mm and 3mm versions, with either 5mm or 6mm diameter steel balls.
Will be included with the soon to be released AnimaSapien Special Edition and as an optional extra with the Pro V2 and XL kit.
I can also offer bespoke made rod lengths with soldered steel balls for this hinge joint as a separate part.
Are you using shoulder screws? If not, are you worried play will develop over time as the threads compact/wear within the through-hole? Also, if I'm seeing it right, by relying on the head of the screw to act as a bearing point, is there any issue with the screw backing out/changing tension over time with movement?
I like the approach; I've used layered sandwich joints similar to yours a few times in the past; I preferred them over fully machined-hinge joints (cause why bother if you don't need to, and your tolerances are all but guaranteed), but I always built them in three layers to avoid issues I mentioned above.
Unless you found a slick solution, which would be totally cool; save space/work where you can...
I agree with Ted. I also use 3 layers - I have tried 2 layers, but the screw or nut tend to loosen when you bend the joint back and forth a few times, so I wouldn't trust a 2 layer joint.
Totally agree guys! Thankyou for the feedback.
These were originally designed as 3 layer, and still are with an additional fixing plate - however, I found that by simply counter-tightening a half or lock nut on the opposite side has prevented the bolt from moving. After rigorous testing, I've found that there is no more maintenance required than that of using a ball and socket joint.
This has reduced not only the cost, but work load and the overall size. Although I probably will include the extra side plate with the bigger version for those larger puppets.
I figured you must of done something like that. Still, two things would give me pause; one, that access to the backing nut (for re-tuning) on a post skinned/cast puppet would be far more invasive then just one tiny slit for an allen key; and two, that without a shoulder on the screw, the threads will definitely wear down within the hinge and introduce a little slop over time. You will feel it like a loose backlash when you change directions in the joint (having learned this the hard way). Otherwise, I really like the efficiency of your approach.
Do you have a pic from the other side? I would like to see how you managed the nut.
In the excitement of it all I overlooked the access issue!
Will go with the three part approach I think, sometimes I get carried away with keeping the cost down and keeping it simple. For novices and small projects it would probably be okay, but no point in cutting corners.
Thankyou so much for your advice!
No problem; we've all been there...
Just had a thought - that 3rd plate is only to stop the nut rotating with it, it isn't needed for strength. So it could be very thin metal, as long as it stays parallel with the other outside plate it would be doing its job. Then would help you keep the joint compact.
I don't think that's the best approach. Ideally, the third plate is not just for securing a nut; the two outer plates are working, with equal pressure (hopefully) to provide even tension on the middle plate. I don't have it in my hands of course, but I think the end result would be diminished with unequal, opposing plates. I think the idea here is to do away with the nut altogether. I say go with equal thickness plates, tap one, through-hole for a shoulder screw on the other two and maybe counterbore the head-side plate to lower the profile of the screw head a little. Not too much (I'd stick to 1/3 of the plate thickness at most), or the thinner area at the counterbore could allow for that plate to deflect slightly over time; and movement quality may diminish.
Another thing I would suggest is trying a different metal for the middle plate; I prefer 510 phosphor bronze (actually, I swear by it). You can still silver solder to it, and it is almost as strong as steel but the bearing quality in that dissimilar setup compared to all steel is incomparable. Rather than relying on bronze washers as most California Tom St. Amand style disciples do, just use a bronze plate. Saves a little room and keeps the setup simple (just layering three plates). If someone is worried about latex contamination, just prep the armature with a light coat of Sprayon 322 silver vinyl coating. $5 a can. A tad cheaper then plating...