Bryden Allen's Website

The Carrot Bolt Belay System

This picture shows my bolt system in use.

During 1963 and 1964 I developed and tested a bolt belay system (the bolts are now referred to as carrots). I produced an original blurb on the system (The Bolt Belay) but I have lost my copy (but Warwick Williams still has a copy). However my original guide contained some of the preliminary details.


These bolts are of course not as strong and convenient as the modern glue-in ring-bolts - but on the other hand they are much cheaper, require less work and they are not as obtrusive (and they can be put in by hand). Some of the bolts I put in 40 years ago are still being used and on the whole there have been remarkably few failures. {I tested them fairly extensively up to 2000 lbs and that crude test value has on the whole proved to be more or less correct (if they have been correctly put in – and this is usually self-evident).} So on the whole this was a good system for its time.


In 2003 I wrote the following description of my bolting system. Unfortunately developing safe bolting in a complex subject. So this will not be an easy read.










This picture shows the bolt and bracket

in more detail.

1.         History


When I started climbing in Australia in 1962 Russ Kippax and Dave Roots had just started to use “Terriers” as a bolt belay/runner system. The second bolt I clipped into (on Terrier 1 on Boar’s Head, Rhumn Dhu area) fell out so I thought their system might be a little suspect. Thus I lashed out and bought the bible of the time “Belaying the Leader” so see what it had to say on the subject. Terriers weren’t mentioned there but when one compared these things with the items that were described in detail (Loxins, Rawls and Dryvins) then the indications were that they would be suspect. So I thought I had better check out some of these more standard objects. This I did at Lindfield rocks. However as soon as I did this I became clear that a 3/8” th bolt bashed into a 5/16” th hole was likely to be better than anything else. Thus the “Bolt Belay” was born. {There is a nomenclature problem – I initially simply referred  to these things as bolts – now they are often referred to as “Carrots” (but then Steve Ahern for example refers to a plain glue-in bolt as a “carrot”) - I think it is now safer to refer to them simply as “bash-ins” (if there is any confusion at all).}


It ain’t real easy to test such things – but I did. The first method was simply to chuck a large rock which was tied to the bolt by hemp rope (nylon rope has too much give and so it is too hard to generate a big enough force) over a cliff. As one could adjust the hemp rope to be of a known strength if the bolt held before the rope broke it was stronger then the known rope strength. {Initially it was the karabiner that broke - but then we had some pretty awful karabiners in those days.} However this was terribly hard work. My next system was too use a good quality scaffolding bar as a lever between two bolts placed 6 ins apart ( see diagram below).


scaffolding bar lever


This system worked out quite well. The general result was that I found that a reasonably placed bolt put in normal Blue Mountains sandstone rock did not usually fail under a 1,000 kilo force (i.e. 10 kN or 2200 lbs). The full details of all these experiments was written up in a long article called “The Bolt Belay” which was circulated with Thrutch (Warick Williams I think has the only remaining copy).


Naturally there is a fair amount of technical detail associated with all this. I found that a bolt of 3 ½ inches length seemed to be about optimal and this needs to be filed down a bit in a tapering manner (I usually did this in a square profile) so that it will fit snugly and tightly in the hole (after being bashed in). The diagram below demonstrates a normally filed bolt.


carrot bolt


It takes a bit of experience to judge what degree of filing is necessary to fit which quality of rock (harder rock obviously needs more filing). Thus one always needs to carry bolts of varying degrees of filing to fit the varying qualities of rock. In granite or trackite (Warrumbungles rock) I used well filed bolts of size 5/16” x 2 ½ ” bashed into a ¼” hole. These days the old twist drill bits and holders are no longer available. Thus if you want to drill a hold manually then you will need to use an impact drill bit and make your own holder (or else import one from the US).
            To attach one’s self to the bolt I developed the key-hole bracket (as you can now buy at any climbing shop). This must be of the correct size. Some people have started to use slightly larger headed bolts and this means a standard sized bracket may not fit (and like wise a larger sized bracket (with a small karabiner clipped in) may come off a small headed bolt).
            I used mild steel bolts but I did experiment with high tensile bolts. However I found the strength gain for high tensile bolts was reasonably marginal. This is surprising because for example the strength of karabiners is very dependent on the quality of the materials used.



2.         My Comparison with Modern Bolts


Since I developed the “bash-in” bolting system many people have tested it and written about it (e.g. Mike Law). However I have never said anything. Thus this is my chance for me to have my little say.


In Australia various commercial expansion bolts have at times been used and as far as I can see my simple “bash-in” bolts are still the better than these. The trouble with expansion bolts is:-
1)         there is less metal present to fill the hole  - so for a shear force (the normal force) they are fundamentally weaker,
2)         they are much more prone to rust inside. Moreover if this happens the problem is not evident to a user and so they can fail disastrously. {As opposed to a “bash-in” where it is usually self evident if a bolt is bad e.g. it sticks out too far.}
              More recently stainless steel commercial climbing expansion bolts have become available. However these are very expensive and in general the modern “glue-ins” bolts are  better in most ways. Thus my comparison here is basically with “glue-ins”. These come either in “hoop” form, “ring” form or plain form (i.e. they need bracket like mine). “Glue-ins” are stronger than “bash-ins” and as  they are usually made from stainless steel they are less liable to corrode. The “hoop” and “ring” forms are obviously more convenient to use. Thus I, like everyone else, would prefer to clip in to a ”glue-in” than a “bash-in”. However the situation is not quite as simple as this and I think sometimes the old-fashioned “bash-in” can still be a more appropriate solution. You need to consider very carefully the following three points.


a)         Strength
I am now going to become terribly old-fashioned and talk about actual strengths. This is what old-fashioned books like “Belaying the Leader” always did whereas good modern books (e.g. “Rock-Climbing – Getting Started” – the standard introduction for Australians to climbing) avoid the subject like the plague. However I think that all climbers need to have a rough appreciation of the relative strengths of all our various protection devises (and also know when this strength is necessary).
            Now you probably know that most karabiners and ropes have strengths in excess of 2,000 kilos (20 kN) and thus the request that a bolt has a strength of a similar order seems reasonable. However what is less well known is that the strength of natural pro (cams and wires) rarely exceeds 1,000 kilos even in perfect placements in good rock (look up the “Black Diamond” catalogue if in doubt of this fact). Thus if you claim that a bolt must of a strength of 2,000 kilos then you are also implying that the strength of natural pro is inadequate. In fact these days a normal leader fall rarely generates a force on a runner in excess of 300 kilos and even then most natural pro fails because of poor placement or poor rock. Thus even smallish wires which have only strengths of few hundred kilos rarely fail because of their fundamental low strength. The reason runners in general are not required to have such a high strength is that a person’s life is rarely dependant on just one runner (as it often is with a rope or a karabiner). Thus if you wish to regard bolts to be like normal runners (e.g. cams and wires) it is ridiculous to require that such a bolt always has a strength of the order 2,000 kilos. {In general I think a climber has to be capable of thinking how big a force a fall is likely to generate and then to place their protection accordingly.}


b)         National Park Requirements
It seems likely that fairly soon much of the climbing in NSW will be under the administration of the various National Parks. It could well be then that these bodies will follow the example of the US and restrict bolting activities and so they will only allow bolts to be put in manually. This is not a bad law because it is simple, it reasonably easy to implement (you can here the row from a power drill from quite a distance), it is consistent with the practice of restricting the access of powered vehicles in National Parks and is what people always did many years ago (e.g. I have put in several hundred bolts in my time but have never used a power drill).  Thus at some time in the future the use of power drills may become considerably more restricted.


c)         Manual Drilling Times
If we are going to be restricted to putting in bolts by hand then the time and ease by which this can be done now becomes important. Thus the drill hole size becomes important. The difference between imperial and metric sizes can be confusing here and so the following graphical comparison may help.


drill depth figures


Now “glue-in” is usually a 10 mm diameter bolt put into 12 mm diameter hole but a “bash-in” is a 3/8 ins bolt put into a 5/16 ins hole. A simple calculation then shows that for similar length bolts (which is normally the case) there is more than twice as much rock to drill out for a “glue-in” than for a “bash-in”. Thus at times you do need to consider is the extra strength of the “glue-in” worth twice the effort of putting it in when a “bash-in” is already stronger than the best natural pro (which is normally adequate). Thus there still may be circumstances when the old “bash-in” is still the best option. {And this is particularly true when you are on a big face (i.e. Bluff Mt) and when lugging up a power drill is difficult and time is of the essence.}



3.         Some Recent Advances and Proposals


1)         One important deficiency of “bash-ins” is that they are not suitable as abseil points. {Initially we simply put in slightly longer bolts (with large washes) and abseiled directly from them. However even I wouldn’t recommend this now.} Two “ring glue-ins” or one or two “hoop glue-ins” is clearly very much the preferred solution. However if one is protecting a long route mostly by “bash-ins” the extra equipment associated with “glue-ins” becomes tedious. In the old days some people overcame the problem by setting up abseil points using 4 “bash-ins” with heavy chain and a large ring between them. However this is expensive in time and the extra weight becomes a problem on a long climb. My solution is shown in the diagram below (and I have used it on climbs on Bluff Mt).


chain belay system


As you can see, in this arrangement one abseils directly off the lower bolt. The chain from the top of the lower bolt to the higher bolt means that the rope cannot come off and adds substantially to the strength of the lower bolt (the system is similar to that used for the guy ropes of circus tents). In fact the bolt is now approximately three times as strong and hence is of the order of 3,000 kilos (i.e. 30 kN) and thus it is similar to the strength of one’s rope or a good solid karabiner. It is not suitable as a regular abseil point but it is OK for an occasional abseil point (i.e. abseiling of Bluff Mt because of bad weather). It is certainly much better than the usual things we always had to abseil off in the old days. Like all such things you need to check everything before you use it (e.g. that the rock is not fractured or the bolts are loose). The chain should be in tension. To attain this what I did is to get the distance roughly correct and the twist the chain a little until it was slightly under tension. Another advantage of this arrangement is that the abseil point is reasonably visible.




2)         Another deficiency of plain bolts (either “bash-ins” or “glue-ins”) is that they are more awkward to clip i.e. they take at least twice as long to clip as ring bolts do. However this problem could be overcome by replacing the top karabiner of a quick-draw by a bracket with a latch. Two forms are possible (A) where the latch is external to the bracket and (B) where the latch is internal to the bracket. In both forms the bend in the bracket only needs be fairly slight as only the thickness of the  quick-draw tape needs to be taken care of (instead of a karabiner).


(A)       In this form the latch would made of thin metal (i.e. tin), be folded over the bracket and then held by a pin. A spring inside would normally keep he latch closed. The following diagram demonstrates its operation.


latch operation


Using this one would slip the bracket of the quick draw directly over the bolt and the spring loaded latch would open and close as you pulled it on (figs 1 and 2).  To take it off one would push the latch to the side (fig 3) and then slide it off (slightly more awkward but then it is always slightly more difficult to take a karabiner off as well).


(B)       In this case the bracket would look like  more an ordinary karabiner because it must be thicker (so that there is room for the inserted latch) and hence not as wide. It is convenient now to make the latch a little smaller. The following diagram shows its operation.




This would be very much the preferred form but it suffers from two disadvantages.
1)         It would be significantly harder to manufacture. Thus it might be as hard to make as a karabiner.
2)         It would be thicker so it may not fit behind some of our current bolts. This is probably not all that important because a climber would still continue to carry some normal brackets for cases like these.


I have experimented a little with such devices but the materials I have used (plain aluminum and mild steel) aren’t adequate and the spring loaded latch is awkward to make. However such devices could be made commercially if there was sufficient demand and they could be simpler lighter and stronger than the karabiners they replace. Thus it is  possible that plain bolts could be used everywhere, they would be just as easy to use as a ring bolt and of course they are much less obtrusive to the public (important if they are placed in the public areas of National Parks).  This is a particularly suitable time to develop new bracket forms because people are starting to put in stainless steel metric “glue-in” bolts. These are slightly larger than the old standard “bash-ins” bolts and the old brackets are difficult to fit. So this is an appropriate time to develop something new.



You might now also like to look back at:

either my "Home Page" (which introduces this whole website and lists all my webpages),

or  “Bryden’s Inventions(which introduces this major set of webpages).


My next normal webpage is A High 3-rope Swing.


Updated on 11/11/2016.


































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