vetical bungee system

[Joe biebel]

I tried a new system two weeks ago and like it a lot. I Had the chance to make a video this weekend and thought I would try my hand at putting something on Yoututbe.

I have uploaded a video (http://www.youtube.com/watch?v=Memt4391kMo) to youtube that shows a good design for a bungee system. The advantages are: The cable feeds (safety) out at the floor. The resistance (cable drag) is low even when cable is extended due to long bungees. The system mounts vertically instead of horizontally. This means that there are no obstacles (ceiling interferences) and since the cables move vertically there is no "bounce" to contend with.

The system allows a 4:1, length of cable to height of ceiling ratio. The system shown is 11’ high yielding approximately 44’ of cable payout. A 15’ ceiling will yield approximately 60’, etc. The system is quiet, smooth, highly reliable and easy to maintain. It is designed for “dedicated” facilities, and not intended to be portable.

Putting the anchors, pulleys, etc. on the 1 X 3 wood pieces allows you to prefabricate the assemblies ahead of time and then screw the assemblies to the ceiling and floor.

The system uses a lot of pulleys, but they are cheap. Have not, as yet, found a "down" side to this design.

[fencerbill]

Originally Posted by Joe biebel

The system allows a 4:1, length of cable to height of ceiling ratio. The system shown is 11’ high yielding approximately 44’ of cable payout. A 15’ ceiling will yield approximately 60’, etc.

A payout of 44 ft sounds like you can't get to the far end of the strip?

[Joe biebel]

Originally Posted by fencerbill

A payout of 44 ft sounds like you can't get to the far end of the strip?

The strip in this room is 38' long and the room is 40' long. This system (as it is shown in the video) would not work on a full length strip. If 50-60 feet is desired, a taller ceiling or another set of pulleys would be necessary.

[PeterGustafsson]

Hi!

Originally Posted by Joe biebel

The strip in this room is 38' long and the room is 40' long.

One foot of run-off??? Does it not get cramped, and have you not have accidents when people don´t stop themselves from running into the walls?


Have a nice time!

Peter Gustafsson

[DanInMI]

That really does not look like a good system.

[Joe biebel]

Originally Posted by PeterGustafsson

Hi!




One foot of run-off??? Does it not get cramped, and have you not have accidents when people don´t stop themselves from running into the walls?


Have a nice time!

Peter Gustafsson

The area this system is in, is a training area. It is used mostly to work with children. We have special rules, like, one foot over the end line touch against. It is not adequate space for a tournament or competition. In several years of use, no one has ever run into the wall. If someone did retreat into the wall, I doubt that they would hurt it too much.

[fencerbill]

Originally Posted by PeterGustafsson

Hi!




One foot of run-off??? Does it not get cramped, and have you not have accidents when people don´t stop themselves from running into the walls?


Have a nice time!

Peter Gustafsson

People learn quickly.

Joe's setup is not ideal. While adequate for instruction it is less than ideal for practicing and inappropriate for formal competition.

There are always tradeoffs between practical and ideal. The advantages of having a dedicated facility rather than having to carry and setup equipment every time you want to fence means that sometimes we accept non-ideal facilities.

[Mergs]

Joe,

Contrary to those who just throw rocks and run, I want to say that it looks like an excellent system as long as you have a wall close to the end of the strip.

That said, there is nothing that prevents you from doing a mulitple sheeve arrangement that can get you any length that you want and putting the excess length between the end of the strip and wall under the sub-floor, if you have one.

[Joe biebel]

Originally Posted by Mergs

Joe,

Contrary to those who just throw rocks and run, I want to say that it looks like an excellent system as long as you have a wall close to the end of the strip.

That said, there is nothing that prevents you from doing a mulitple sheeve arrangement that can get you any length that you want and putting the excess length between the end of the strip and wall under the sub-floor, if you have one.

Thanks. It is a very good system and as you noted adding multiple sheaves can extend the length of payout. I had thought about putting this by the wall, but imagine if you will, a long facility with consecutive strips. No reason I can think of not to have them out in the middle of the floor, back to back, just beyond the safe runoff distance. Certainly, if the unit was mounted away from a wall, say 5' or so, in order to provide a walkway, it would cause no one harm and no one would harm the sytem that might bump into it.

Unlike a reel however, you are going to want to place it right the first time you set it up. It's a fair amount of work, so getting the placement right is important.

[PeterGustafsson]

Hi!

Originally Posted by Mergs

Joe,

Contrary to those who just throw rocks and run, I want to say that it looks like an excellent system as long as you have a wall close to the end of the strip.

That said, there is nothing that prevents you from doing a mulitple sheeve arrangement that can get you any length that you want and putting the excess length between the end of the strip and wall under the sub-floor, if you have one.

There is one drawback with a more extensive pulley system: the telephone wire will be going around more bends, and the wire strands will therefore be subject to more wear. This can be counteracted by using larger pulley diameters.

Joe: in the video, you show what happens when the fencer end is let loose, so that it smacks into the end. Have you thought about putting in some kind of damping component to lessen the shock? If so, what?

Anyway, I think that it looks good on the video.


Have a nice time!

Peter Gustafsson

[Mergs]

Peter, you bring up a good point, however, the cable Joe is using is solid wire, not stranded. Stranded would be more flexible but given the amount of tension on the wire, it seems to work well. What I would be concerned about is not so much fatigue failure, but work-hardening of the copper and becoming brittle. But that would take so long and given the relative cost of phone wire, is a very economical alternative.

[Joe biebel]

Originally Posted by PeterGustafsson

Hi!

There is one drawback with a more extensive pulley system: the telephone wire will be going around more bends, and the wire strands will therefore be subject to more wear. This can be counteracted by using larger pulley diameters.

Joe: in the video, you show what happens when the fencer end is let loose, so that it smacks into the end. Have you thought about putting in some kind of damping component to lessen the shock? If so, what?

Anyway, I think that it looks good on the video.


Have a nice time!

Peter Gustafsson

Peter, I have not thought about that point as I have been trying to work out the mechanical bugs and logic. Basically, I tie a knot in the phone cable that stops the cable from retracting past (the pulley) a certain point. The one thing that has occurred (if this proves to be a problem) to me is to take a small, soft rubber ball, drill a hole through it and put it between the knot and where the cable pays out. Before I would do that though, I would probably want to see the need demonstrated.

As to the pulleys. I don't think larger pulleys on this system will help. The cable I use is telephone cable. At this point, it is necessary to correct Merg's assumption that it is solid core. It is multistranded, four conductor flat wire, like the kind that goes from the wall socket to the telephone. This cable is very light, highly flexible, strong and inexpensive. The individual strands are so fine, that in scale, a 2.5" diameter pulley is huge. An important factor in fatiquing the strand of wire is the ratio of the diameter to the length over which it is bent. The wires I am currently using were recycled from earlier bungee systems and have been in use for several years. The reliability of this wire, used thusly, is amazing. I set up these wires 4 years ago and still have not had to use a spare. The only questionable thing about this wire is that it has a slightly higher resistance over say a 60' length than heavier cable. I use two of the conductors for the ground and it reads about 1.5-2 ohms over the 60' distance. The single conductors show twice as much resistance over the same distance. Perhaps it's not FIE, but the resitance is so low, and without the slightest fluctuation, that it is fine for this purpose.

[brtech]

I think solid copper is going to break a whole lot sooner than stranded. It's much less able to handle the stress either around the sheaves or at the fencer end, which works the wire back and forth quite a lot. I think you want 22-24AWG stranded, and high strand count would be good if you could get it.