Homemade stuff

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Re: Homemade stuff

Postby Scott McCrea » Jun 14, 2014 12:05 pm

GroundquestMSA wrote:I am interested to know how much force is acting on a set of brake bars during use. How flimsy can they be before breaking? I'll have to play around some more.

The article starting on page 5 of this issue of Nylon Highway may give you some of the answers you seek. http://www.karstportal.org/FileStorage/ ... y/nh46.pdf
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Re: Homemade stuff

Postby tncaver » Jun 14, 2014 9:28 pm

I think you may be in virgin territory testing those wooden brake bars. Please be careful while testing them out. The top bar takes the most abuse. Maybe you should use
a metal bar on top and test the wooden bars below that.

GroundquestMSA wrote:
tncaver wrote:Maybe it's just me but seems as if wooden brake bars would not have the strength to last very many rappels before total failure. Every rappel would weaken the bars
by reducing thickness.


These weren't meant for serious use.
The areas I was most concerned about were around the holes/slots. This is one reason I used square blocks with a groove instead of dowels, to keep more material around the holes. Large dowels would be just as good, but I wouldn't have room for them on an 8" frame.

I am interested to know how much force is acting on a set of brake bars during use. How flimsy can they be before breaking? I'll have to play around some more.
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Re: Homemade stuff

Postby chh » Jun 16, 2014 6:22 pm

There's a device we use in SRT tree work called the "rope wrench". It's nothing more than a couple of bollards that introduce a bend into the rope. Though it's now made of metal and can be attached mid line and will also hold you, your truck, your inlaws, your inlaw's trucks, and an old radiator..... the prototype was made of a hickory tool handle. Wood has a deep and varied history as a friction/rigging device in the maritime industry as well. With the right species, wood diameters, rope diameters, and loads, I wouldn't hesitate to use wood as a friction device that I would trust with my life. Problem is this takes a lot of experience and judgment, which most cavers don't have when it comes to wood. It's safer to make it out of stainless and forget about it.

But, I like your style Jonah. Do be careful, but don't stop experimenting :grin:
Your words of caution are no match for my disaster style!
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Re: Homemade stuff

Postby GroundquestMSA » Jun 16, 2014 8:02 pm

I have lots and lots of experience with many species of wooden fenceposts, and of firewood... does that qualify me? I used an old tobacco stick because it was at hand, but seasoned locust and hedge apple are extremely hard, and would theoretically last a while. Everything has been tried before, but I'm trying to think of another way to made a wooden descender, other than the obvious wooden versions of existing devices like the atc.

Also coming soon: Bone brake bars. I rappelled on a set of deer antlers last year, and now I've got a nice clean ribcage ready for use. I'm not looking forward to the smell of cutting them.

I spoke too soon, by the way, concerning my socket brake bars. The machinist made them off of my blueprints, but when he realized what they were he refused to give them to me. He didn't want to be liable. Now I'll have to make some myself or forget it. For now I'll forget it.

Further off topic, the rope wrench reminds of an episode when I ascended an old seat belt with seat belt buckles. Fun, if pointless. I must admit that I don't understand the advantages of the rope wrench.
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Re: Homemade stuff

Postby Scott McCrea » Jun 16, 2014 8:11 pm

GroundquestMSA wrote:...reminds of an episode when I ascended an old seat belt with seat belt buckles. Fun, if pointless.

:rofl: :clap:

Pointless? I think not. Crazy stuff like that is where inspiration comes from.
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Re: Homemade stuff

Postby tamarmole » Jun 20, 2014 1:08 pm

Experimenting is really important even though 99 times out of 100 you will be reinventing the wheel. If it weren't for dangerous idiots (this is intended as a compliment) we would still be using ships style rope ladders.
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Re: Homemade stuff

Postby GroundquestMSA » Jun 20, 2014 1:42 pm

tamarmole wrote:Experimenting is really important even though 99 times out of 100 you will be reinventing the wheel.


Yep. I hope one day to have an original idea, but those are pretty rare. It is interesting to see all of the things people have tried. I had an idea for a nutcracker style brake for a descender, before I saw one on Dr. Storrick's site. It is obviously not a particularly useful concept, but I'm glad that someone has actually built and tried it.

Speaking of new ideas, have you seen these little lid dispensers at convenience stores that allow you to open a little door and grab an individual cup lid without fumbling with a stuck together stack of them? I had that exact idea about ten years ago, long before these dispensers were seen in my area. Oh well.

I'm not working, so I'm building a new, all wood descender today. I'll let you know how it goes.
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Re: Homemade stuff

Postby GroundquestMSA » Jun 20, 2014 4:08 pm

GroundquestMSA wrote:I'm not working, so I'm building a new, all wood descender today. I'll let you know how it goes.


It works, which is surprising. I expected too much friction. There are no advantages to this contraption, which is a dual ATC/fixed-bar micro-rack, and plenty of disadvantages. I discovered one big disadvantage when I went out to test it. I had forgotten to make an attachment point, and hadn't allowed enough material to add one. Eager to test the thing, I poked a small hole and used a prusik cord for attachment, making this not only a completely impractical, but wildly dangerous invention. And it isn't entirely wooden, I lied, it incorporates a carabiner. The ride was smooth and easy to control. I only rappelled 20' x2 before a thunderstorm started. Rappeling without a helmet down a metal ladder, hanging by a hairbrained wooden descender from the tallest tree around, in a thunderstorm, was even a little too much risk for me, so I took a break.

I'll add photos in a bit.
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Re: Homemade stuff

Postby GroundquestMSA » Jun 20, 2014 5:06 pm

Image


Image


Image
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Re: Homemade stuff

Postby GroundquestMSA » Jun 20, 2014 6:19 pm

While there may be no adavantages, it would be easy to make a metal version that would probably be safe. A metal version could be very minimal, 8" long and less than 1" wide and thick, with 3 welded or bolted on bars between metal plates. A carabiner could be added to a hole at the top, some do this on a regular rack, to add friction or to aid in locking off.This would be smaller than a bobbin, with plenty of friction and the option to use a wide range of rope diameters. However, you're still using a carabiner as two brake bars, an idea lots of people don't like. I would love to build this, just for fun, but I don't know how I would attach the bars to the plates.

I've sketched this imaginary device, but now the postimage tool isn't working for me. Maybe later.
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Re: Homemade stuff

Postby GroundquestMSA » Jun 20, 2014 8:34 pm

Here it is, somebody want to build it for me? :big grin:

http://i1241.photobucket.com/albums/gg515/GroundquestMSA/thing001.jpg
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