Science 101: Navigation Tower Design

Well, the time has come, to talk about the most important part on a rally bike. The navigation tower. We have been involved in that area since the birth of Aurora, and it’s been a long journey with data that one cannot put in such a post. To that end, read on. ‼️

From early on we had the pleasure of working with some of the best (#HighwayDirtbikes, #RallyAdventures, #PalAndersUllevalseter, #Nifontova) and the feedback was, and is, always a critical part of our development. So! Experience shared, is double the experience ?

Data. Let’s gather some! We have used a 3-axis G-Force datalogger to get the exact forces that a navigation tower experiences. Exact numbers cannot be revealed, but this is double figures. Think that a Dakar navigation tower, with the rider carrying spare parts on the tower as well (the worst place to put them…) may reach (hold on…) 10 kilograms, and you get a rough idea of the forces involved. Data from the accelerometers can be used, then maths can do the rest and different data analysis strategies can be performed, (transforming time into frequency) to allow us to see the frequencies and with time, gather data to check different bikes, terrains, rider styles etc. Frequencies will allow us to design for fatigue, which is the process that most metals will fail. Especially aluminium which does not like vibrations. This way we can design for infinite life (if only we could do it for ourselves…). That concept is not new, there are parts in our everyday car which are designed for infinite life and we drive/ride over some bridges that were designed with the same concept as well.

Weight. While everybody is going bananas about the weight of the tower, factories included, unless the geometry of the tower is perfected and the center of gravity is calculated in multiple situations (with or without navigation gear etc.), then the result can be from bad handling at best, to dangerous situations at worst. Imagine a 140 kilogram bike with 100 kilograms on the front wheel and 40 on the rear. That would be interesting eh? So next time you read ‘The lightest kit out there’ , think about the details and ask other users about the rideability of the bike. We have all read about bikes that ‘hide’ their weight because of the mass centralization. Similar situations arise here. The best example is a very light tower, with heavy lights and heavy top because of the navigation gear. In reality, one would need the opposite. Very light lighting structure and navigation gear, and then the tower can be light, or medium weight. So, a structure with the center of gravity as close to the headstock of the bike as possible, is the best case scenario. Yes, all the weight will be carried by the suspension, and marketing will dictate that lighter is better and that the lightest bike will win, but hang 5 kilograms half a meter from the headstock, ride in sand and then come back to tell the tale. Attach these five kilograms to the headstock and come back again. People tend to clone OEM designs. When you see a bike racing Dakar, you will see a blue box, called iritrack, usually inside, on the side, or below the navigation tower. That unit alone is close to two kilograms. So, next time you are thinking of getting a tower like this in your bike, remember that this was designed to operate at its optimum, when a devise of 2kg is inside it (or wherever this bike has it in Dakar). These 2kg, not only will change the total behaviour, but they change the center of gravity of the assembly, making the bike easier to ride. This is important, as cloning usually means that designers play with scissors. It’s not that the OEM got it wrong, it’s the replicators that missed an important aspect. Two kilograms of importance to be exact…

Ergonomics. While a tower is designed, important ergonomic decisions take place. How will the rider see important information? What do we want him to see? In Dakar racing tower models, the information display is such that the rider sees only the most important stuff. Important information is the oil pressure for example, the fuel reserve light. These can actually cause a bike to be immobilised, which is not good in any way. For example, the 701 Enduro has lots of electronics on-board, one of them being the ABS button. Now this electronic gizmo, if you take off the rear ABS, it keeps blinking distracting the rider every five seconds (or thereabouts). So you are riding, and then your eyes pick up an orange blink. Down you look. After five seconds the same. It’s really difficult to re-train your brain, which is hardwired after all these years to look the orange warning light. So it’s better to hide this button, and put that out of sight. Still reachable by hand, but not in your line of sight. This is not big news in anyway, car industry is doing it for the last decade at least. All you need is to be trained to use different technologies and ideas from different areas and incorporating them with your own to make something unique. We all remember cars that used to have 10 warning lights, each meaning a different thing, temperature number indicators etc. These days, we get an LCD screen, but the detailed information is hidden from the driver (we will not see actual temp. gauges anymore for example in most cases). One reason behind this is that we are trying to let the rider/driver focus to what matters the most, minimizing the mistakes that can happen because of him being over-informed or overly stressed. You don’t want to keep seeing the neutral light. You know where that neutral is. Continuing with ergonomics, we are all familiar with incandescent light bulbs. From time to time, these need to be replaced. Imagine a tower that you need to take it off, undo all the cabling, take the back plate with speedo gauges off the tower, undo everything, put your arm inside the tower, take the bulb off, hope you can reach it, then do the reverse. All that in the rain, in the field. Yes, there are navigation towers out there requiring that effort (honestly, you can buy one of those!). In the #Xplorer, obviously not! There are actually multiple ways to assist the rider, depending on how he did the wiring. Thought has been put to this part as well. Should the wiring is kept above the light, there is an opening below the light to allow the rider to take the bulb out. Should the wiring is below the light, closing this opening slot, the user can reach the bulb from the top. Blocking both entries (top and bottom) and then with four M6 bolts the front light is out, exposing the bulb. It is designs like this, which will allow you to enjoy your trip/race, instead of quickly turning everything onto a nightmare. Yes, you need to remove the fairing, but again quarter-turn bolts are used in our rally kit. Allows you to take the fairing of in seconds. One should be able to disassemble the tower easy. So we have used not just plain rivets everywhere we could, a tedious work for the manufacturer, because each rivet is manually put in place, but we also used rivets that are impossible to rotate and come loose. And impossible, means just that. An interlocking design, making it impossible for them to rotate and cause havoc in the process. Every single detail and part has man-hours of design work. Nothing left to chance.

Having finished with the ergonomics, we get to decide the materials. Aluminium? Steel? Stainless Steel? Polymers? Composites? They all have different abilities, strengths and weaknesses. They can be combined, or used alone (a solid aluminium tower for example). When choosing the materials, the method of manufacturing is decided. Sheet metal? CNC? 3D printed? These will play an important role of what materials we choose. Aluminium can crack when bent, so the correct tools need to be used. Stainless Steel is more resistant to fatigue, while a polymer can give the required ‘spring’ effect to the tower. Since the tower is designed back to back with its head clamp, they are matched pairs. Remember the center of gravity? Using headclamps for other towers, may work. But it may not, and it’s always best to ask the manufacturer, or you may be up for a surprise.
Up till now we are not a composite company in anyway, but we excel in using traditional materials. #Xplorer tower is made out of aluminium, stainless steel and polymer all in multiple thicknesses and geometries, to allow the navigation tower to flex when needed, but be solid when riding/racing. Materials to the extreme ends of the tower are different, making a tower which is ‘braced’, while aluminium is used for the core tower, keeping the weight low. Remember the center of gravity? Our navigation tower has a thicker lower brace, from stainless steel to lower the center of gravity, just for that reason. A hard shell from braces that are made from tougher materials, with a soft core made from aluminum. There is always a plan, and it’s of great pleasure to tell you that it actually works (stay tuned when we get to the ‘accidents’ post…).
Joakim Lundby raced twice in Morocco Desert Challenge, crashed once or twice and on his second try he won his class. We have two cases of crashed 701 Rally Replicas with our kit on, and in both cases the towers did their job. Allowed the riders to return home, no electrical cables snapped and the equipment was well protected. The idea is that you reach home/bivouac. Then you can take care of everything, but we have to evacuate you from the situation as soon as possible.

Have a #goodriding weekend.

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