THE HOTNUT: TECHNICAL

The purpose of the following Supplementary Text is to more fully describe Hotnut cam features of design and use summarised in other illustrated Webpages. It is recommended reading for Hotnut users.

Hotnut body design (Patented)
Basic functional design parameters and geometry are common over the Hotnut projected range of six sizes, covering crack widths 23 to 100 mm. An important aspect of this commonality is that for all Hotnut sizes placement and holding characteristics are similar.

Body design is based on a solid one-piece ‘H’ section, with the side web ends of the ‘H’ profiled into twin cams, and an opposed projecting end of the cross-web of the ‘H’ being centrally profiled to form the pivotal nose. The section inherently provides low body bulk combined with rigidity, strength and light weight, with the facility for additional weight saving by metal removal in the larger sizes. A unique feature of the Hotnut, carried forward from its predecessors (see About us/ history Webpage) is that the nose is not merely a pivot point within the rotational plane of cam action, but a specifically designed pivotal surface working in conjunction with the cam profiles to provide optimum jamming, disturbance resistance, and stability in both parallel- sided and flared placements. Holding properties of the Hotnut have been further enhanced by the selection of a low cam design angle.

Hotnut control rig (Patented)
This long sought after, yet simple, crucial addition transforms the Hotnut from a typically awkward-to-place tripodal cam nut into a precision soft-feel protection device without any loss of camming performance and without the springs and other mechanical paraphernalia of the SLCD. Essentially, the control rig comprises a ‘string’ and a ‘slider’, one end of the string being pivotally mounted close to and below the Hotnut’s nose, and the other end connected to the slider, the latter being free-sliding on the Hotnut’s attached sling. The ‘string’ is conveniently provided as a looped, tough, flexible, monofilament plastic, and the ‘slider’ is a short, abrasion resistant, wrapped and sewn webbing sleeve. To facilitate free slider movement on the sling whilst maintaining good sling flexibility, the two sides of the sling are lightly sewn together over the distance of slider travel in Hotnut use, the sling being captively retained in position on the Hotnut’s loading bar by a sewn cross seam.

Hotnut control rig functions
In all, the rig provides four functions in Hotnut control, as described below, but only three of these are routinely applied by the climber in device use, the fourth being automatic.

Automatic control function
The control rig automatically retains the pre-deployed Hotnut in cam mode whilst carried on the ‘gear rack’ and during selection, the presumption being that the Hotnut will be used as a camming device, only. This feature obviates the irksome need to pre-manipulate into cam mode prior to placement as necessary with previous tripodal nuts.

Note The control rig tolerates manual override of the default cam mode pre-disposition, into wedge mode. However, the practice is neither intended nor recommended because it is fiddly, and therefore contrary to the very purpose of the Hotnut, whose usefulness as a cam greatly outweighs that as a wedge. So, an advised procedure is to place a simple wedging nut when functionally adequate, and save the Hotnut for a potentially more demanding non-wedge placement later in the pitch. (The point is made that the Hotnut in cam mode provides a sound placement in most constriction, i.e. ‘wedging’ cracks). Hotnut rated strengths given in Hotnuts Technical Info are based on tests with the Hotnut loaded as a camming device.

Routinely used controls
(1) Remote manual cam retraction.
Achieved by pulling the slider along the sling in a direction away from the Hotnut body, or equivalently, feeding the sling through the slider towards the Hotnut body.

(2) Remote manual cam expansion.
Achieved by pushing the slider along the sling in a direction towards the Hotnut body, or equivalently, feeding the sling through the slider away from the Hotnut body.

(3) Remote manual cam positional locking.
Achieved in any cam rotational ‘size’ position between minimum and maximum by finger-thumb pinch-locking the slider onto the sling. (Alternatively, with the larger Hotnut sizes, this control can be equivalently and often more readily exercised by pinch-locking the string onto the sling at a convenient point above the slider).

The manner in which the above-defined Routinely used controls are applied in the placement/removal of Hotnuts is described in the following ‘Hotnut application procedures’.

Hotnut application procedures
These procedures are given in explicit form, because they have been found to result in quick, reliable single-handed application of the Hotnut.

Retraction/locking prior to placement.
As explained above, the Hotnut is primed in cam mode, and on selection from the gear rack will usually be in a state corresponding to approx.fully-open (i.e. similar to an SLCD). The first task is to retract the device. There are alternative ways of doing this, method (a) is best suited for smaller Hotnut sizes because of their lower expansion range and weight, while method (b) lends to the larger sizes. Both methods are easy and quick.
Method (a): The sling is held in the open hand, and the thumb used to draw the slider to full Hotnut retraction.
Method (b): The slider is gripped lightly between thumb and forefinger with Hotnut body downwards, and the device given a shake (or two) causing Hotnut body inertia to draw the sling through the slider to full retraction.
The Hotnut is kept locked in retracted position by pinch-locking the slider against the sling for smaller Hotnut sizes, or often more readily, by pinch-locking the string against the sling above the slider, on larger Hotnut sizes.

Placement
With the Hotnut retracted and pinch-locked, the nut body is readily guided and located (even ‘threaded’ if necessary) into the selected placement and aligned with the anticipated direction of pull from a fall. Since the Hotnut is fully retracted at this stage it will generally speaking be a loose fit in the placement, and the best way to ensure a good secure three-point contact fit is to rotate the locked Hotnut about the position of pinch-lock, in the direction of increasing cam size, until the nut completely fills the placement with both cams engaged. Then, whilst retaining side pressure on the Hotnut nose via the held sling, pinch-lock is released, and a pull on the sling completes the placement. At this stage a check can be made to confirm three-point contact, by wiggling the looped (carabiner) end of the sling transversely to the plane of camming action – there should be no resultant rocking of the Hotnut.* Finally the Hotnut is set in place by a firm tug on the sling to ensure sufficient holding friction is generated, to prevent accidental loosening e.g. as caused by subsequent climbing rope movement disturbance.

* Footnote
It should never be presumed that a placed tripodal cam nut will automatically self-locate into three-point contact with the rock when there is initial fitting clearance between nut and crack. The best way of ensuring three-point-contact is to pre-engage both cams with the crack before nose engagement, because once the cams are seated, the nose will naturally find its own position. If this sequence is not followed, there is the possibility of mal-placement, resulting in unstable two-point contact, with one of the cams not engaged. The above recommended Hotnut placement procedure, utilising its unique control system to ‘size’ the nut to the crack before engagement, minimises the risk of such mal-placement, but to be certain, transverse wiggling of the sling tests conclusively for the condition, because two point contact is clearly evidenced by nut gyration, which no amount of sling tugging will remove. The recommended action to rectify such a mal-placement is to remove and re-position the nut. (But depending on the degree of nut gyration present in the above test, it may be possible to correct the situation by slowly rocking the nut via the sling alternately in each transverse direction until in one direction stable three-point contact is made, as indicated by the nut’s placement feeling solid. However, it could be that in the latter position the nut is now too much misaligned with the anticipated direction of pull from a fall, to be relied upon). It is worth remembering that risk of mal-placement is increased if/when the Hotnut – or indeed any other protection device – is placed blind, i.e. without a clear view.

Removal
A Hotnut well set, as it always should be, will require loosening before extraction, because the lightly constructed control rig is not intended for, and will be damaged by, excess forces generated in attempted direct retraction of a tightly jammed nut.
Hotnut loosening is readily accomplished by either transversely wiggling the pinch-locked device, or in the case of a really well-set condition, by alternate transverse tapping of the top and bottom areas of an accessible cam lobe face, with a suitable tool, to break the friction bond.

Once the Hotnut is loosened, the sling/slider is rotated towards the Hotnut nose, and pinch-locked. Then, locked sling/slider rotation in the opposite direction causes the string to tension and the Hotnut to retract, giving easy removal. Even if the Hotnut has been ‘threaded’ into place removal is still single-handedly straightforward, because in the locked state the Hotnut cannot re-engage the rock, and removal is simply a matter of reversing the placement path.
See more information about the Hotnut use