# creating friction in a fall arrest device

by tommy060289
Tags: arrest, creating, device, fall, friction
 P: 22 Hey Everyone, I'm currently looking at designing a device that would allow people to escape from working at heights quickly and safely in the event of an emergency (up to 33 m) I know there are some products on the market already but since I don't have a great deal of experience with them I'm not overly familiar with how they work but what I'm hoping to achieve is to design a device which can be used for a set range of weights (as if the device is specific to a certain weight range, it is easier to create the amount of desired friction) which would allow a working to step off a platform in an emergency and just lower down the rope unassisted, so the device is controlling the friction force. the downward force will be equal to m*a and since mass is constant Im going to want acceleration to be 0 after an initial acceleration to get the person to a safe desending velocity. Therefor, what I need is an equation that would give the friction on the rope according to the velocity of the rope passing through this. Is there anyway to do this or does velocity have no bearing on the friction between the rope and the device? If so, does any one know of a device I could research that would allow me to control the maximum speed at which the rope could pass through a device. At the moment I'm thinking more electric motor with chain but if I can keep it all mechanical (and thus probably cheaper) that would be preferred. On closing I would like to say this is ONLY a theoretical project, so Im not going to go jumping off building or anything so no one is any danger:) Thanks for your help!
 PF Patron P: 1,739 Why limit your device to 33 meters hieght? You may get some ideas from this: http://en.wikipedia.org/wiki/Abseiling
P: 204
 I know there are some products on the market already but since I don't have a great deal of experience with them I'm not overly familiar with how they work
go learn how they work. engineering is 20% research, 10% innovation, and 71% perspiration.

PF Patron
P: 1,739

## creating friction in a fall arrest device

tommy060289, just in case you do come up with a NOVEL idea and you consider applying for a patent to protect your invention, have a look at some basic patent requirements. One requirement is to include in the “Specification” section this:

“Background of the invention. You must include the field or subject matter of the invention and a description of all relevant prior inventions. Here's where thorough research pays off. When you refer to earlier inventions, point out specific problems that your invention solves.”

http://www.nolo.com/legal-encycloped...ons-29661.html
P: 31
 Quote by jehan60188 go learn how they work. engineering is 20% research, 10% innovation, and 71% perspiration.
Haha, that's an awesome saying.

I like the type of escape chute instead. You know the garbage chutes they use on highrise construction?

http://construction-garbage-chutes.h...s/a1ygxzgy.jpg

Ropes suck when it comes to safety, having broken many in my childhood I can tell you they dont age well.