I would like to show everyone some new tech I've developed.

It involves using a spring to help cushion a spear's blow.

A video showing the spear's build is linked below.

https://www.youtube.com/watch?v=bB2SfEWz_ew

The spring helps to soften the spear's blow by adding distance over which the spear decelerates when it strikes a target. Because it takes more pressure to depress the spring than the foam it helps the transition when the foam in the spear head fully compresses and force is moved into the spear pole so you don't feel as much of the spear's punch.

I've already built a spear on this setup with the spring in the spear's head and it works well. Over the winter I'll be building another with the spring on the pommel end.

The spring has a rate of approximately 25 lbs. Initially, I thought the spring would be too stiff; however, it bottoms out on the high end of a medium stab. I added the spring to the spear to make it hit more safely on hard stabs because I know it can be uncomfortable to be on the receiving end of one. It was a very interesting project; by having something to measure how the spears hit, I was surprised to discover how hard normal stabs have become in this sport.

I like the hell out of that design. For securing the nut, I'd use two nuts and red loctite. The nuts and bolt are my only concern. How would you plan to cover/pad them at the head?

You cover it the same way you would build a normal spear head. The only difference is you have to make some grooves in the foam so that the head can slide underneath.

There's a guy in Amtgard who has done this already, named Oznog. He made a spring loaded spear that, according to his wiki: "you can stab as hard as you want and not hurt the person you hit except it may send them flying."

I don't know if that sounds like a particularly safe idea to me.

It's an interesting concept, but how is it different/better than using a higher density open cell foam for the head? Furthermore, how will the design utilize haft padding at the head? If you put the spring at the pommel, how will it be useful to reduce force at that point? If uncovered, how will the moving parts potentially endanger other players or the wielder?

I think it's also important to remember that a compressed spring returns with about 1/4 of the force of the initial load(dependent on several variables of course). So, if you exerted 25lbf of force into a stab, the spring would return with 6.25lbf. I'm not sure about how that stack up to the return force of fully compressed foam, but I'd be relatively certain it was less than that.

spring calculator: http://www.efunda.com/designstandards/s ... _force.cfm

The problem I run into is that if I add more foam to the head of the spear I increase the risk of the head folding over. The spring gives me an extra inch of compression without having to bother with any foam issues.

Haft padding at the head just needs a little overlap to cover the gap that's caused by the movement.

A spring at the head absorbs energy more efficiently than it does at the pommel. However, my hardest stabs are actually when I'm one-handed (because of the increased body mechanics) which should still allow the spring to compress. Also, since I can bottom out the spring a little too easily, having it work a little less efficiently at the pommel end may be just fine.

I see no risks with the spring at the head end because it's covered so well. If it's on the pommel and if it were uncovered you would have to worry about catching the moving bold ends in your palm or you would have to worry about pinching your skin between the band shop pole and the slide.

It does kind of throw you off of itself at the end.

Any update on this? How has this held up/been received at events?