Popping Knee Cop Lame

[Iohn deMar]

This is probably a typical new-guy question, but here goes...

I have a pair of stonekeep articulated knees. 4 lames per knee cop. They've worked fine for me so far, but I recently attached a greave to the lowest lame for added leg protection. The problem is, everytime I take a knee, the topmost lame pops out from the knee cop. How do I fix this?

I can post pics if that's any help.

[wcallen]

The exact fix will depend on how "off" things are.

The real answer is that the lame(s) aren't quite the right shape so when you actually force them the way you are, they pop.
It is possible that you are just really close to right and you could flair the lame a little bit to get it to stop popping. Unfortunately that will make the knee bend a little less and you (probably) are really having the problem because the knee doesn't bend enough.

It is possible that the leg is riding a little low so that the top is trying to bend too much and the bottom lames aren't doing their job. If that is the case, pulling them up a little and the flair might do it.

How involved the fix is will really depend on how "off" the result is. A few pictures might help.

For example, if your leg isn't in the legharness and you bend the armour, how far can it bend before it pops? If that is less than you are trying to bend, then you have a problem. If it bends lots, it is probably the "too low" thing.

Depending on the shape of the lower lame, you could get some more movement between the lames on the cop and the greave.

Another solution is to set things up with a rear plate on the greave and cuisse so that you can't sit all the way on your ankles. Then you need less movement in the knee.

Many SCA leg articulations are "approximate" and almost everyone in the SCA tries to move more than a real leg is supposed to when they loose a leg and crawl around on the ground like a toad.


On to a rant you can all ignore, and then we can go back to being helpful......

I solved the problem in 2 ways:
I don't go down on my knees.
I went to a floating cop.

My previous articulated knees did move enough for me to squat, but I don't like doing it.

How do I get away with this? I don't plan to authorize again, so I can ignore the rules that seem silly. I take the leg in practice, but we are just sparring so I tell them it is good and go on.

..... back to constructive comments.

When we get a picture we will know how big your problem is and then something more productive can be offered.

Wade

[Galvyn Lockhart]

Did the lame pop out before you attached the greave? If so, no idea. If not, try using a separate greave & see what your results are.

[Arrakis]

This is probably a typical new-guy question, but here goes...

I have a pair of stonekeep articulated knees. 4 lames per knee cop. They've worked fine for me so far, but I recently attached a greave to the lowest lame for added leg protection. The problem is, everytime I take a knee, the topmost lame pops out from the knee cop. How do I fix this?

I can post pics if that's any help.

The real answer is: Don't attach your greave to your demigreave. It doesn't work right for SCA combat-from-the-knees crap. Just strap the greave as usual, make sure the bottom bits are shaped right to ride gently on your foot and ankle, and wear it so that the demi covers the top of the greave and all will be well.

I was having a similar problem with a pair of Bokalo's full legs and unriveted the greaves, did a little more shaping... so much better.

[Signo]

The simpler solution that I think of is to dismount the incriminated lame, and hammer the hidden edge ( the edge that pop out ) and draw it longer, sacrifying his thickness In this way you COULD achieve the desired effect, or at least improve the situation. If things improve but not much, you can then try to flare a bit the same edge, but I would avoid that, because if the lame still pop out, then it would be harder to put it back in place. If this happen a complete remake of the lame is needed.

But first of all: Detach the greave from the knee.

[Sean Powell]

Even before detaching anything. Hold the armor up and put it through its range of motion. If the armor bends 140 deg and you are asking it to bend 160 then SOMETHING has to give. You could very well fix this lame and have another pop. If the armor can't make the range there is no fix short of replacing the knees.

There is however a work around. When the armor pops you are creating a small gap between knee and lame but the gap typically isn't large enough to let a rattan stick in. If you want to cut the lame BACK rather then stretch it out. This allows the lame to pop out and then pop back in easily. For a number of years I fought with leg armor where the lame above the knee popped habitually. I developed a habit of smacking my own leg with my sword after standing as it was just enough to pop it back inside the knee. It got some laughs but was perfectly safe otherwise.

Sean

[Stonekeep]

We've made a lot of varieties of joints over the years, but a standard 5 piece flatlame joint wont take the pressure of a pinned greave. Like Sean said, something has to give. Weve made 7 piece flatlame joints which are better suited for pinned greaves, but the only joints weve made which were actually suited for it were the 5 and 7 piece premium dished articulation (Unfortunately, about the time I had finished developing this and getting it polished for production, the economy took a downturn, and the last thing people wanted was to double the price of a pair of joints). They had a wider range of motion than a human leg, so there was no pressure whatsoever when adding a fixed greave. But a pinned greave adds a whole lot of pressure to a standard flatlame munitions joint, and it wont be able to handle it.

[Iohn deMar]

Thanks for the help everyone. I detached the homemade greave from the articulated knee assembly, and all works fine now. Out of curiosity, how far did articulated knees bend in period. The pair I have move about 90 deg., whereas my leg bends about 120 when kneeling on my back leg.

[Signo]

I think that around 90 degrees is a good measure. You can sit, ride, walk, run, jump, make stairs of any kind with just that 90 degrees. NO, kneeling and leaning backward was not contempled.

[Bender]

Legs can be made to do this 120 degree thing. But it takes a careful design consideration and you must also dish the lames. A double pinned articulation relies on an ellipse to cover ranges of motion,and it's a mathematical formula. So you measure the leg and make a couple of marks to gage on it.

If there is going to be a pad,you measure over that-it will increase distances. Then you do one with the leg straight. Another to the same points with it bent to where you want to go. Subtract the larger from the smaller. This is the articulating motion range. My experience and general knowledge of decent medival examples tells me to break down the rest of the pattern in pre determined ratios. There will be side widths at rivet points. Optimal rivet insets usually work out to be a ratio of about 2/10ths in from the edge by the center line. The base ratio of the pattern folded in two.

A cop needs to be wider on the sides than a lame. Enough to accomodate a strap to keep it from flopping. And wide enough to provide a base that keeps the side wing from bucking. 2.5 inches or so seems to work well. Average ratio in a cop from sides to center is usually about two to one. And that gets a bit narrower with the minimal one inch or more depth needed to let it swing.

About half of the motion is in the cop distance through the dome center. Measure top to bottom over the curve and subtract 3/16 to 1/4 inch. Most "Gaposis" is entirely attributable to the armorer not dishing lames, and not leaving enough underlap. A decent articulated knee will groan and *spread out* before gapping. And most medieval lames were very slightly bannana shaped.

Not straight on top-that's more something you see in guantlet articulations. The slight recurve allows then to open more and lets the leg straighten. A good joint will back bend about ten degrees from straight-keeping the demi greave from biting the calf bone.

[wcallen]

Thanks for the help everyone. I detached the homemade greave from the articulated knee assembly, and all works fine now. Out of curiosity, how far did articulated knees bend in period. The pair I have move about 90 deg., whereas my leg bends about 120 when kneeling on my back leg.

Here are some real examples of bend:

Farther than normal:
http://www.allenantiques.com/images/A-2 ... y-bent.jpg
More pictures of the same:
http://www.allenantiques.com/A-200.html

Pretty normal:
http://www.allenantiques.com/images/A-169-bent-2.jpg
and more pictures of it:
http://www.allenantiques.com/A-169.html

And another one where I was rude and didn't shoot a picture fully bent:
http://www.allenantiques.com/A-162.html

I bet when you are sitting on your backside you are bent more than 120 degrees. Just kneeling without moving, maybe.

Wade

[Stonekeep]

This is a pic of what I spoke of before, that I developed right before the economy tanked. All the joints made in this manner had a range of 180deg or more. I advertised them as bending further than a human leg could. The only takers were people looking for spring and spring stainless. After the economy tanked, we went three years without selling any. Its fun to make one every now and then, but the general SCA public is not in the market for them.

http://ep.yimg.com/ca/I/spiers-saddlery_2196_4497181


This was straight

http://ep.yimg.com/ca/I/spiers-saddlery_2196_5697311