The story of our 6633 Arctic Ultra Pulks

As many of you will already know, Tanya and I are on our way to participate in the 6633 Arctic Ultra. This race was Tanya's choice, and in April 2017, Tanya and I visited Martin Like and his team in Brecon. The aim of the visit was for us to learn as much as we could, about the cold, the race, the clothes and everything else about our visit to the "coldest and windiest" event on the planet.

Previously I had contacted Mimi Anderson, Edward Chapman, Roddy Riddle and some other 6633 finishers and individuals who unfortunately didn't make it. The aim was to understand what it took to complete this gruelling 350-mile (563km) race, which has now, with the new route, become the 380-mile (616,6km) race.

On a side note; 616km’s is the distance between:

  • Pretoria and Durban,

  • New York to Pittsburg,

  • Atlanta to Memphis, or

  • Bristol to Edinburgh.

In short, it is bloody far!

The length, however, is only one element, the combination of arctic winds, extremely low temperatures (-20 to -45 degrees Celsius: -4 to -49 degrees Fahrenheit), and a wheeled sled (pulk) that has ‘everything' you need out there, and which is pulled behind you through snow and ice, and over ‘undulating', all add to the 'toughness' of the race. The estimated weight of all the gear is somewhere between 23 to 27kg’s plus the weight of the pulk, water and some extras. In total probably a total weight of around 40 to 50kg’s – the final weight will be determined when we pack everything.

The one thing that was very clear and which was echoed by every person we spoke to, including Martin, was that you needed to have a system for everything and needed to be highly organised, and so the journey of the pulk started. My angel and I worked on the designs together and Tanya gave me the perspective I needed to adequately address her needs and fears. She drilled the first hole setting her 6633 Arctic Ultra dream in motion. Over the past few months, we were regularly asked, why are the pulks taking so long? Well, the finished pulks are version 6 and are the result of 11 previous models, each having been tested and found wanting at some level. The evolution of our pulk is not as much a story about the pulk, but rather the story about our preparation for this epic event, and the evolution of our understanding of the conditions out there.

Let me start by saying, as much as Tanya, and I know about running in extreme heat, we know absolutely nothing about participating in the extreme cold. Those that know Tanya will attest to the fact that my angel is often seen wearing a jersey or jacket when it is 30 degrees Celsius (86 degrees Fahrenheit) outside, so it would be an understatement to say that we have no cold weather experience. As novices in cold weather racing, our aim is primarily to finish. We hope to finish with a great experience, with as little as possible injuries and with all our toes, fingers ears and nose in-tact. For us to finish in the best possible time would, in all likelihood mean the maximum allowed time. Our lack of experience, inability to prepare for cold weather racing and the advice to be organised and have a system framed our need for a pulk within a particular context.

We decided that our pulk should not be a piece of kit, but must form that basis of our system and must provide the organisational platform from which we will manage our race, and so the journey started.

A clear problem statement; ‘we need a safe, workable, durable and light organisational platform’ gave rise to the following requirements:

  • The pulk must be able to withstand the most extreme cold weather conditions,

  • If the pulk malfunctions, it must be repairable in the field with minimal tools and with available spares,

  • If a repair is not feasible, an alternative option for pulling the pulk must exist to ensure that we can stay in the race,

  • The pulk must be small enough, and compact enough to make it manoeuvrable, yet big enough to hold all our kit (and there are loads of kit),

  • The pulk must be extremely light, comparable to the Snowsled Expedition pulk,

  • We must have various options when it comes to pulk configuration and pulling methods,

  • The pulk system must provide easy access to all our kit, without the possibility of losing items either in strong winds or at night,

  • As the race route follows the famous ‘Ice Road’ which is used by large trucks, the pulk should be visible during both daytime and at night,

  • The pulk must present the lowest possible wind resistance,

  • It must be as quiet as possible, and

  • It must be able to be deployed as a mobility aid in case one of us sustaining a severe injury, and help cannot reach us immediately.

Please note that the pulks Tanya and I will be taking to the 6633, is tailored to our own ‘special-needs' and to a great extent to counter the fear that stems from our lack of experience. So, if any of the other 6633 Arctic Ultra participants read this, please don't let our approach influence you in any way. Our approach to pulk and kit is just our way of addressing our unique race challenges. We have no experience in this, and our approach may work or may not, we will know soon enough.

It is this list of requirements that resulted in the construction of 11 different pulks over a 9-month period. I don't believe that nine months is coincidence, but instead that Tanya and I birthed this final design, which consists of the following:


Various options were considered; carbon fibre, Kevlar, and carbon-Kevlar. These space-age materials could deliver an extremely ‘strong' platform, but would not necessarily be able to handle the extreme cold or be field repairable with minimum tools and materials. The advantage, though, is that a pulk made from these materials would be extremely light. Next on our list was aluminium, an obvious choice, as sub-zero temperature tests showed that the tensile, yield and impact strengths of aluminium alloys increase at extremely low temperatures, while the material retained ductility and became more corrosion resistant without any increase in its brittleness. Our choice aluminium series 2219-T87 has the best combination of strength and fracture toughness, both at room temperature and down to -196 degrees Celsius.

Next came the choice, to weld or not to weld? Although welding the Aluminium would deliver solid joints and would save weight by eliminating fasteners, it would not afford us the ability to do a field repair, so the choice was made to, not weld the aluminium but to bolt all the pieces together. The next step was to identify what fasteners to use. It would be of no benefit having a material that can handle sub-zero temperatures if the nuts and bolts can't handle extremely low temperatures. It was decided to use 316 Stainless Steel, rated as suitable for cryogenic purposes (-269 degree Celsius), so -40 degrees Celsius should be no problem for either our aluminium or the stainless-steel fasteners.

Taking into consideration the impact of temperature (expansion and contraction variations between aluminium and stainless steel), continuous vibration over a 617km distance (which is roughly 382,500 plus wheel rotations), the loading effect of the cargo and the vibration on all fastening joints caused by the wind, meant that the design had to include a double fastening point for each "joint" which is further strengthened by a washer, a spring washer, threat lock and a lock nut. At critical points, the locknut is further supported by a double nut.

This material combination means that we are meeting three of the eleven requirements, these are:

  • The pulk must be able to withstand the most extreme cold weather conditions,

  • If the pulk malfunctions, it must be repairable in the field with minimal tools and with available spares, and

  • The pulk must be extremely light, comparable to the Snowsled Expedition pulk.

Design and Function

Next, we turned our attention to meeting the remaining eight requirements.

Alternative Pulling Options – here we experimented over time with the conventional two pole configuration but found this to be extremely jerky, especially if one does a slow jog. Turning with two poles also felt strained, with lots of force being applied to hips and lower back. We then tried a single pole configuration and found that it was much better, and by loosening the hip-belt of our harness, we could do a reasonable trot (not run) with minimal discomfort. However, our cautious nature meant that we retained both options and I had to find a solution to use the same poles for both options. We retained aluminium as the material of choice for our pulk poles but covered these with rubber to minimise the possibility of a cold injury if we would accidentally touch the metal without gloves.

Pulk poles can also be used in a free, or unrestricted vertical mode, or can be fixed at five different gradient settings between 10 and 60 degrees. Fixing a gradient is done with a simple retention clip.

Alternative Options to Wheels – for snow or, if the wheel(s), would become dysfunctional we included two snow rails. For the rails to be used the front wheel and two side wheels are clipped out to lower the pulk onto the rails. Each rail has been covered with XHBLACK QCR plastic runs which are extensively used in dog sled racing. If the plastic would separate, then the sled can continue to run on the aluminium rails.

We also decided to retain multiple wheel configuration options, and the pulk is designed to run on two, three and four wheels. Two and four-wheel configurations make use of a 20-inch wheel with easy clip in/out capability. The three-wheel option retains two 20-inch wheels with a smaller nose wheel that clips in or out using two retention pins.

The two wheels and three-wheel configurations require the pulk to be rebalanced to prevent strain on the hip, lower back and shoulders. This is done, pre-race, or in the field, but does require the use of an Allen key and a number 10 spanner or socket. The axle can be moved in 3.25 cm intervals across the entire length of the pulk which means that the balance point can is reached to within an accuracy of 98.75%.

Size – The length of our pulks is dictated to by the primary kit groupings we have. To understand the choices, we have made is important, here is a brief explanation. Before I continue, it is worthwhile knowing something about Tanya. My angel is, for the most part, a calm, collective, kind and reserved soul, but she does not like to battle, and patience lost is to be avoided at all cost. Patience lost means many things, but mostly it means that my angel requires a great deal of time and effort to re-focus, and to find the lost patience and put it back in its place. I think you all get the picture. It just so happened that December 2016, we holidayed in Bloubergstrand. In some ancient language Bloubergstrand probably means the place where the wind never stops. This did not make for a great holiday, but it did have one benefit, experience which provided much-needed context. During our visit to Martin and his team in early 2017, Martin explained the bivy process, and I immediately knew that bivying, per se, was not going to work – ‘n moer gaan gestrip word’ (sorry guys, this only works in Afrikaans). Two things stood out for me during the conversation, and that was the time it would take to deploy and break down the bivy and the limited options a bivy provided.

Therefore, besides our clothes, which Martin and his team sourced and shipped to us in South Africa, our first real decision was to opt for quick deploy tents, but I also knew from our Bloubergstrand excursion that anything with poles was not going to work. Trying to fit a pole into a hole while the wind is blowing was no small feat, nor was trying to stuff the little beach tent back into its sack afterwards. This means that we went for the Heimplanet inflatable tents. These tents go up in under a minute and come down in even less, all with minimal effort. We also decided not to try and stuff the tent back into its travel sack but opted to rather drop it quickly into a 65 liter Osprey duffel bag. Two folds and a loose role is all that is needed, and the entire Cave three-man tent fits into the duffel bag without any effort, so even in the wind, this should be a 'smooth' operation.

While we were at it, we tested our Snowy Owl Expedition sleeping bag rated at -60 degrees Celsius. Trying to stuff this monster into its travel sack resembled something like a WWE wrestling match, and one emerges sweating like a sprinter on the other end of the process. We decided to apply the same logic as we did with the tent and stuff the sleeping bag, its sleeping mat and blow-up mattress into another 65-liter Osprey duffel bag. The entire process takes less than 30 seconds with no wrestling (this might take a little longer out there).

This approach means that we don't have one big duffel bag, like most participants, but smaller purpose full bags. This does mean that our duffels weigh slightly more than the single duffel, but from a process perspective, we have very fast deploy, breakdown and pack-away capability, something that is important in a race where sleep comes at a premium. We decided to make every second count during the 6633 Arctic Ultra, whatever we do must have one of three benefits for us; it must either fuel us, or progress us up the course, or regenerate us. The less time we waste on actions that don't deliver one of these three benefits for us, the more efficient we will be out there and the more likely we are to finish a race where only one-third of competitors typically finish. In life and business I have learned that it is the small things that make the big impacts.

Keeping with the multiple duffel bag option, we have two more duffel bags, one for clothes and kit (first-aid, survival, etc.), and one for food, with cooking fuel, and to hold all or warm water flasks. So, four duffels placed next to each other, food in the front, next is clothes, then sleeping bag and lastly tent. Our clothes bag has some dry sacks inside, each containing a clothing group, so one for base layers, one for mid-layers, and one for outer layers.

It is this combination of pulk, multiple duffels, dry-sacks, tent etc. that created a unified system. I was able to fit all four bags onto a pulk that is [134 cm’s long and 57 cm’s wide]. It was a close call but being able to fit all four bags next to each other on the pulk meant that Tanya had to buy me dinner one evening.

Access to Kit – the next big step in our system was to be able to gain quick access to everything in our duffel bags without having to loosen multiple straps, or having the possibility of losing items. We developed a rapid access system and integrated this as part of the pulk. It allows us full access without the risk of losing piece pulks. We also chose duffel bags with top d-type access so that we can work inside the bag with easy access to everything.

Safety – this is a significant concern for both of us. Our pulk design has many safety features, reflective tape, rear reflectors, rear red light, and if an accident would occur scannable QR-codes that links to an online information sheet of emergency contacts, insurance, and medical history etc. We also have luggage guard rails that ensure that the transported items don't get tangled in the wheels.

Low Wind Resistance – due to the design and the choice of duffel bags we were able to limit the pack height 32cm which reduces the overall wind resistance to within an acceptable limit.

Low Noise Factor – we were both cognizant of the fact that metal is a noisy medium and a mixture of Gorilla double sided gel tape, rubber lugs and felt is used to minimise rattles etc. The clips used to attach the third wheel, pulk poles etc. have been heat shrinked to eliminate metal on metal rattles. This is important to Tanya, I have it on good authority that the day I start to rattle, that I stand a good chance to be traded in for a newer model.

Mobility Aid – finally our pulks are capable of carrying a load of 50kg/axel. This means that if something happens and immediate evacuation is not possible that we can tether the two pulks, transfer all kit to the second pulk, lower the second pulk onto its skids, and attach its wheels to the first. The first can then be used as an emergency mobility stretcher with an emergency bivy bag, and sleeping bag deployed.

Designing and building the pulk was not an isolated function but was done in conjunction with our training, kit acquisition, kit familiarisation and getting to understand the ‘arctic problem’. Every one of our training sessions over the past 12-months (a total of 85-6633 Arctic Ultra-specific training sessions during the past six months, and 110 training sessions in the 6-months before that) we came back with a better understanding of what we were going to do, how we envisaged doing it and conceptually what problems we may encounter. All of this was translated back to our system, the pulk, our kit and ultimately our strategy.

In closing, our 6633 Arctic Ultra saw us do 390 hours of training (this translates into roughly 3,200km’s) much of this in the past six months focused on walking with lots and lots of hills as the staple diet of our training. Chest colds meant that Tanya and I could not train over December, the time we planned to do our 12, 18 and 24-hour training runs. After four weeks of little to no training, we decided not to play catch-up as experience taught us that this typically leads to injury. We continued with the remainder of our training program but refocused our attention on hills, and lots and lots of hills. We adopted the Wim Hof method of preparing our bodies, and mind, for the cold. This started with cold showers, then cold pool sessions and eventually ice baths. Core development, some weights, lots and lots of reading about sleep cycles, cold weather injuries – its prevention and treatment, and a great deal of organisation around food, visas, travel arrangements, insurances, communication (it is Tanya's birthday out in the Arctic, so Tanya and Arielle need to speak to each other on the 12th of March). We also started eating all the wrong stuff to gain weight for the race and although we feel the additional cm’s, these should melt away during the race. Race logistics such as batteries, poses a few headaches and needs very creative solutions, our medical arrangements, assessments, prescriptions and briefing on what to do when is freely provided by our longstanding physician who has gone through numerous race planning sessions with us over the years, and finally, we are hoping to fit in a few quality time visits with Arielle and Larry before we leave them to man the fort while we are gone.

Next time I post something on the 6633 Arctic Ultra, it will be about the race itself. What we did right, what we did wrong, what worked and what did not. Fingers crossed that everything goes as planned.

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