exspelio
11 years ago
"Tamarmole" wrote:

"Tocsin" wrote:

Thanks for the write up, I have some Kong gear and rate it very highly.

Rack or bobbin seems to be a generational thing. I go out with a mix of people and the rack devotees are all just a few years older than me and swear by them for a smooth ride and a much easier time on long pitches with a rope of 200' (and several kilos) hanging beneath you.

I was tempted to try a micro rack but this advantage is diminished if it's a short frame design (hence easier in change overs) and you cant spread the bars enough for a smoother ride.

I think your assessment bears that out, so i'll be sticking with my current setup for now.



The Rakong with stainless bars would be a total winner.



Stainless bars are not necessarily a good thing, heat dissipation on duralloys reduces the likelyhood of the rope contact (friction) area becoming hot enough to "glaze" the rope.
Always remember, nature is in charge, get it wrong and it is you who suffers!.
Graigfawr
11 years ago
How about mild steel?
Tamarmole
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11 years ago
"exspelio" wrote:

"Tamarmole" wrote:

"Tocsin" wrote:

Thanks for the write up, I have some Kong gear and rate it very highly.

Rack or bobbin seems to be a generational thing. I go out with a mix of people and the rack devotees are all just a few years older than me and swear by them for a smooth ride and a much easier time on long pitches with a rope of 200' (and several kilos) hanging beneath you.

I was tempted to try a micro rack but this advantage is diminished if it's a short frame design (hence easier in change overs) and you cant spread the bars enough for a smoother ride.

I think your assessment bears that out, so i'll be sticking with my current setup for now.



The Rakong with stainless bars would be a total winner.



Stainless bars are not necessarily a good thing, heat dissipation on duralloys reduces the likelyhood of the rope contact (friction) area becoming hot enough to "glaze" the rope.



Interesting point.

I reckon the overheating problem can be overcome by using stainless tube rather than solid bar.

My understanding is (and I may well be talking out of my nethers) that ally absorbs heat very well but isn't too great at dumping it - once you get ally hot it stays hot. Conversely whilst stainless isn't the best conductor of heat the greater surface area of stainless tube compared with solid ally bar means that it dumps heat fairly well.

Secondly there is less friction and hence less heat with stainless than with ally.

I seem to recall reading something along these lines in the first edition of On Rope. If I get time I'll hunt it out.
Tamarmole
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11 years ago
"Graigfawr" wrote:

How about mild steel?



Rust and corrosion.
exspelio
11 years ago
Er... would less friction on a descending device be a good idea? :confused:
Always remember, nature is in charge, get it wrong and it is you who suffers!.
Tamarmole
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11 years ago
"exspelio" wrote:

Er... would less friction on a descending device be a good idea? :confused:



Yes, provided you can drop in extra friction by either moving the bars closer together or running the rope over a hyper bar.
Tamarmole
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11 years ago
"Tamarmole" wrote:

"exspelio" wrote:

"Tamarmole" wrote:

"Tocsin" wrote:

Thanks for the write up, I have some Kong gear and rate it very highly.

Rack or bobbin seems to be a generational thing. I go out with a mix of people and the rack devotees are all just a few years older than me and swear by them for a smooth ride and a much easier time on long pitches with a rope of 200' (and several kilos) hanging beneath you.

I was tempted to try a micro rack but this advantage is diminished if it's a short frame design (hence easier in change overs) and you cant spread the bars enough for a smoother ride.

I think your assessment bears that out, so i'll be sticking with my current setup for now.



The Rakong with stainless bars would be a total winner.



Stainless bars are not necessarily a good thing, heat dissipation on duralloys reduces the likelyhood of the rope contact (friction) area becoming hot enough to "glaze" the rope.



Interesting point.

I reckon the overheating problem can be overcome by using stainless tube rather than solid bar.

My understanding is (and I may well be talking out of my nethers) that ally absorbs heat very well but isn't too great at dumping it - once you get ally hot it stays hot. Conversely whilst stainless isn't the best conductor of heat the greater surface area of stainless tube compared with solid ally bar means that it dumps heat fairly well.

Secondly there is less friction and hence less heat with stainless than with ally.

I seem to recall reading something along these lines in the first edition of On Rope. If I get time I'll hunt it out.



From On Rope (1st ed.) p.120:

"Aluminum bars tend to wear and leave a black aluminium deposit or streak on the rope. To slow down bar wear and keep a clean rope, stainless steel bars were developed. . These bars were hollow to reduce weight and to increase bar surface area to form an excellent heat dissipater. Acting like a radiator, this hole keeps the bar cool. Aluminum bars are better heat sinks than steel bars. This means they can absorb more heat away from the rope, but once the bar is hot the heat cannot be dissipated further. The steel bar cannot grab as much heat, but it can get rid of it better."
Tamarmole
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11 years ago
Having consulted with colonials (Americans) I have decided to put my money where my mouth is and have ordered an appropriate length of stainless tube.

For those of a technical bent it is 1/2" NB, Schedule 40, 316. This has an outside diameter of 21.34mm and a wall thickness of 2.77mm.

Drillbilly.
11 years ago
I'd go for 2 tube bars, in my estimation, it's the top one which wears dramatically and the second which gets stupidly hot. I'd be inclined to run a bigger second bar. (What do the yanks do again?-have a look at the storrick website). On a 4 bar rack, bigger bars are likely to run faster!!!!

Also, I'm going to get quotes on importing a pmi chest roller and harness. 2?
Tamarmole
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11 years ago
"Drillbilly." wrote:

I'd go for 2 tube bars, in my estimation, it's the top one which wears dramatically and the second which gets stupidly hot. I'd be inclined to run a bigger second bar. (What do the yanks do again?-have a look at the storrick website). On a 4 bar rack, bigger bars are likely to run faster!!!!

Also, I'm going to get quotes on importing a pmi chest roller and harness. 2?



I am planning on doing all four bars in stainless tube.

PMI roller - provided it is not stupid money I could be interested. If you are doing a reasonable size US import I would be really interested in a BMS long micro rack

When I get a moment I will post an update on my exploits with my homemade chest roller.
Drillbilly.
11 years ago
Looking like £120 (ish) for both single roller and harness

(I think I'll use their harness and then bodge it to the top of my croll)
Tamarmole
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11 years ago
For the sake of a few quid/dollars get the double roller version - it will give you much more flexibility. It will allow you to run a QAS through the spare roller. It will also allow you to experiment with the Mitchell system.

My home brewed box is twin roller - you are more than welcome to borrow it to try it out (on the understanding that I take no responsibility if you kill yourself using it).
Drillbilly.
11 years ago
I am waiting on some quotes. The one thing I really dislike about the previous attempts is *&^%ing around with meccano on a pitch.
J25GTi
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11 years ago
If only importing small quantities of anything get them to send it in individual packages, if it is under £120 inc p+p you dont pay import duty
exspelio
11 years ago
"J25GTi" wrote:

If only importing small quantities of anything get them to send it in individual packages, if it is under £120 inc p+p you dont pay import duty



Or get them to post you the specs and get someone to make them under license :confused:
Always remember, nature is in charge, get it wrong and it is you who suffers!.

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