Rack alternative for long drops?

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Re: Rack alternative for long drops?

Postby gdstorrick » Mar 9, 2012 8:45 pm

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Re: Rack alternative for long drops?

Postby ON_ROPE » Mar 9, 2012 9:19 pm

The problem with heat build up on long drops is that once you reach that certain temprature threshold your rappel device essentially loses its ability to create friction because the nylon in the rope is turned into a liquid when the device touches it. You accelerate rapidly usually stopped by sudden impact with the bottom. Same phenomonom when you drive your car around a corner to fast and begin to skid. The tire begins to melt (that black on the pavement) and the car accelerates into the ditch.
When you see that glazed finish on your rope after a fast/ or long rappel you need to realize just how close you came to total loss of friction. In a rack type device the friction is produced in logarithmic incriments from the top. If your number one and two bars get too hot then all you have left are 3-8. If you are on a 4 bar micro rack and one and two get too hot, you are in deep do-do. If you are incredibly lucky and love life on the edge ANY rappel device will work. If you survive, write an article describing how great it is on long drops. Lure some other unlucky fool in.
Obviously, you can see I have an opinion on the matter. Open frame rappel racks are the best device to safely rappel long drops. The rest are lucky.

Safe Cavin,

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Re: Rack alternative for long drops?

Postby gdstorrick » Mar 10, 2012 6:04 am

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Re: Rack alternative for long drops?

Postby Cody JW » Mar 10, 2012 12:22 pm

I own a mini rack with hyper bar and have found that if you are going over a tricky lip and the rope is dirty or stiff it is easy for the rope to jump over the hyper bar. For me at 220 lbs. when that happens I will not have enough friction and had to have a bottom belay the first time it happened. Other times I have watched it almost go over. Once you are clear of the lip it will be fine. At the time I was caving with a guy who was around 150 lbs and he was just fine without the hyper bar. With the hyper I get a nice smooth ride. Without it I am toast. Because of that I am not a big fan of mini racks. If it is a short drop where a regular rack is overkill I will use the steel 8. This is just another example of what works for the average or light person may not work for a heavy guy.
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Re: Rack alternative for long drops?

Postby LukeM » Mar 11, 2012 12:44 am

Cody JW wrote:I own a mini rack with hyper bar and have found that if you are going over a tricky lip and the rope is dirty or stiff it is easy for the rope to jump over the hyper bar. For me at 220 lbs. when that happens I will not have enough friction and had to have a bottom belay the first time it happened.


What length is the frame?
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Re: Rack alternative for long drops?

Postby Cody JW » Mar 11, 2012 2:32 pm

Not sure I would have to dig it out to measure it. It is called a transitional rack that OR1 used to sell. It has 4 bars and all bars open like a regular rack, the only mini rack I have seen like it.You do not open every other bar and use the bight of the rope. Threads just like a regular rack. It appears to be about the same size as most other mini racks I have seen. I bet Storrick has one.I have also tried other mini racks with the same result so I do not think it is anything specific to that rack. It is more specific to my girth and not enough friction with 4 bars.
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Re: Rack alternative for long drops?

Postby Cody JW » Mar 11, 2012 6:10 pm

Actually, only the lower 3 bars open. The top bar does not. Just now remembered that.
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Re: Rack alternative for long drops?

Postby LukeM » Mar 11, 2012 7:31 pm

The only reason that I ask is that a shorter rack will provide more friction. For their micro rack BMC offers two different lengths, and the shorter provides a good deal more friction. As a skinny guy I need to use the longer version. If you ever get a chance to play around with it the short version may be the ticket for you...or maybe not.
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Re: Rack alternative for long drops?

Postby gdstorrick » Mar 11, 2012 7:50 pm

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Re: Rack alternative for long drops?

Postby Cody JW » Mar 11, 2012 8:16 pm

gdstorrick wrote:
LukeM wrote:The only reason that I ask is that a shorter rack will provide more friction. For their micro rack BMC offers two different lengths, and the shorter provides a good deal more friction.


More precisely, AOTBE (&TNA), a longer rack can provide less friction. Rack length below the bars doesn't change friction, and one can push the bars together on a long rack. If you need more friction, changing to a shorter rack won't help (unless it is so short that there isn't room for the rope :big grin: ).

If you check the tabulations on my web site, one of the important ones is the "usable" length for bar movement. Good rack users control their descents with bar motion. If someone has enough bars and a long enough rack, and they are either braking or feeding with their braking hand on free drops, they aren't controlling the bars as well as they could.

I find it amusing that my 1994 BMS Mini Rack is shorter than my 2009 BMS Micro Rack.
I agree with you on the bar movement thing. Most standard rack set ups do not allow ample movement of the lower bar to give much friction adjustment. Five bars on a regular 6 bar rack usually will. If you use all 6 bars you better get an 18" frame or longer. My mini rack gives me no room to move the lower bar with caving rope.
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Re: Rack alternative for long drops?

Postby gdstorrick » Mar 12, 2012 3:50 am

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Re: Rack alternative for long drops?

Postby LukeM » Mar 12, 2012 7:54 am

gdstorrick wrote:More precisely, AOTBE (&TNA), a longer rack can provide less friction. Rack length below the bars doesn't change friction, and one can push the bars together on a long rack. If you need more friction, changing to a shorter rack won't help (unless it is so short that there isn't room for the rope :big grin: ).


Thanks for clearing that up Gary. Looks like what I was taught about short micro racks being especially useful for heavier people (vs shorter) isn't necessarily correct. More like the longer version is especially helpful for lighter people and the shorter version is nice to save space/weight as long as you are heavy enough to rappel effectively without needing more bar spacing.
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Re: Rack alternative for long drops?

Postby Scott McCrea » Mar 12, 2012 8:34 am

LukeM wrote:longer version is especially helpful for lighter people and the shorter version is nice to save space/weight as long as you are heavy enough to rappel effectively without needing more bar spacing.

Exactly. More spreading space=more variable friction.
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Re: Rack alternative for long drops?

Postby PeterFJohnson » Mar 13, 2012 10:03 pm

I appreciate the info - especially Allan and Gary's info on device temperature. Helpful stuff.

ON_ROPE wrote: Obviously, you can see I have an opinion on the matter. Open frame rappel racks are the best device to safely rappel long drops. The rest are lucky.


The original questions still remains though - and I imagine it isn't one that can be hashed out on an internet forum - what would you define as a "long drop". Is it the 200m that ACT lists? or perhaps something far less? And again I realize this is conditional on experience, gear etc.
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Re: Rack alternative for long drops?

Postby gdstorrick » Mar 14, 2012 4:01 am

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