Exclusive – Making the Xray NT1’15

Following our exclusive interview with Xray’s on-road designer Martin Hudy about the forthcoming NT1’15 nitro touring car we now have a more in-depth article from Xray in which Martin explains the challenges of making an already proven car even better.

A typical nightmare for any designer is to improve a successful proven product, a product that customers already have good experiences with, a product they already love as it is. In these situations, as a designer you are on very thin ice. It would be almost impossible to significantly shift the features of the product to make it even greater, but you can screw up easily and destroy a previously successful product.

Working to improve upon the NT1 has been exactly like this … skating on very thin ice in the springtime. The NT1 has been our most successful platform, having won many World, European, Asian, and USA Championship titles since it was first released 8 years ago. In the beginning it was my father Juraj who was responsible for development, and he was the one behind the car’s early successes. I was very honored and humbled to take over responsibility for NT1 development a couple of years ago. One of the reasons the NT1 has become one of the most popular nitro touring cars is, in my opinion, the fact that we have not made any radical changes and all the improvements were logical refinements which helped to improve either performance or reliability (or both). This strategy has helped us to build a strong core of customers that appreciate the small but steady improvements we continue to make while still keeping the same platform. However, not everyone shares this approach, and as usual there are always differences in opinions. Without fail, I continued to get questioned when an all-new NT1 will be made. This was quite an interesting perspective: despite the NT1 still being in the lead with respect to performance & reliability and winning the majority of races around, customers were voicing their opinions about there not being major changes to the NT1.

So as a designer you not only have to know how to skate on thin ice, but also to be a master of customers minds; you need to figure out the perfect balance between what is not enough news and what is too much news, and also find the perfect balance between continuing with the current product and when to bring out an all-new product. And in the end you need to accept that whatever you do, it will be still be impossible to make everyone 100% happy. Not an easy task, right?

For some time we have been playing around with the idea of making some major changes to the NT1 platform, but personally I was very happy with the performance of the car and we still continued to be successful at races around the world. In the last few years we have always pushed off the idea of some major update, as I had to consider the fact that the nitro on-road racing class is decreasing generally worldwide. Being always in touch with our sales & financial department, I was reminded that we needed to consider market development and the feasibility of investment into an all-new platform to forecast a realistic return on investment, too. So despite being a diehard racer, regardless of what I wanted to create I would still need to prove the case to our sales department so that all the new developments being considered could be analyzed for their potential impact on sales. Again … not an easy task.

However, sometimes things that are out of your control can change, which is exactly what happened in this case with the new EFRA tire rule which requires hard, large diameter tires.

The turning point for me was the last European Championship in Spain. Because of our extremely busy season with all other races, we decided to skip the Euros Warm-up. We had a great performing car, plenty of experiences and knowledge, and a great team capable to take the win if we had luck on our side. Coming to the Euros, I quickly realized that our prior decision to skip the Warm-up was not very good … In fact, that decision was quite bad. The new tire rule was a much bigger challenge than I ever expected, and the lack of warm-up time put us behind everyone else right away. Despite our working very hard on set-up, we were not performing at the same level as other teams that had gotten their starting set-ups from the warm-up. So instead of fine tuning the set-up like other teams, we had to make some pretty radical changes from run to run. I cannot recall any other nitro race where we worked so hard, literally sweating extensively from how hard we were wrenching. At the end we worked out all the details and Alex was finally competitive with everyone else, but unfortunately he ran out of good luck in the semi-final when he flamed out during refueling. So for the first time in several years, we did not have any car in the main final. In all honesty, it was a very frustrating moment for me as I felt responsible for this result. I had to accept the fact that with the new hard tire rule, the current NT1 did not perform as well as it did with soft tires.

As I was personally disappointed, we decided to stay with Juraj at the Euros track for few days for private testing. We worked extremely hard, we drilled a lot, cut a lot, dremeled even more, and we baked ourselves in the hot sun. After extensive work and testing dozens of different combinations, we were able to get the performance of the car to the same top laptimes from the Euros. So with all the changes and testing we did, we gained a lot of experience with the hard tires and had a clear idea of what we need to change on the car. Unfortunately this was all AFTER the Euros was over and done. After returning home from the Euros, there were no more internal questions but rather we had a simple, straightforward goal: to adapt to the new tire rule we had to make a major update to the NT1 platform. As usual we had to start defining what would remain and what would change, and considering the experience we had from the Euros we had a fairly clear ideas about these. The list of details to remain on the NT1 included the following:

• Suspension geometry
• Suspension materials & flex
• Drivetrain
• Gearing & ratios
• Clutch
• Shocks
• Fuel tank & electronics placement

All these were the things that were working great and did not require any changes. The highest priority was to find the optimal flex characteristics for the hard tires, while still keeping the proper balance and compromise between traction and steering while keeping the car easy to drive and stable like it has been until now.

The composite bulkheads we used until now were of course softer than the aluminum bulkheads that most of the competition has been using, and the soft composite created a great amount of the flex which was great for soft, small diameter tires but has become one of the main obstacles for hard, large diameter tires. So in this respect the task was very clear: change the flex of the car by changing to aluminum bulkheads and redesign the main framework of the car which is the main source of chassis flex. Sounds easy, right? Not even close! If I was designing the car from scratch it would have been much quicker and easier since there would be no limitations. But considering that we wanted to keep most of the working parts the same, it was quite a big challenge as I had a lot of restrictions and limitations to consider. I spent a considerably longer time behind the computer screen than I normally would, however I had very clear idea of what I wanted to achieve and had a lot of previous experiences with the aluminum framework from the T4 platform. So fortunately, the main challenge for me was to combine existing parts with the new ones.

With the hundreds of hours I spent designing various T4 aluminum bulkheads and having long-term experience with manufacturing possibilities, I had a very clear idea of what I needed to do for the NT1 aluminum bulkheads. I had to make bulkheads that allowed easy access to diffs & other parts, but I also had to remove the suspension holders from the bulkheads and mount them directly to the chassis. The independent suspension mounts in front ensure the best flex while providing maximum steering, while the independent suspension mounts in the rear provide maximum traction to the car. And of course, having suspension mounts separated from the bulkheads allows for more flexibility when it comes to further development, since I can play around with the position of all the suspension mounts to determine the best placement.

The more complicated area, which was also fairly challenging and required several prototypes, was the front suspension arm mounting system. Front upper arm mounting on a pivotball suspension has a significant influence on the flex of the suspension. I wanted to ensure that the holder would be easy to mount and easy to work with, but most importantly it must have the proper flex. When brainstorming about what else I should incorporate to the new suspension mounts, I recalled last year’s Euros and Worlds when we were looking for less caster but reached the limits. At that Euros we needed a certain amount of caster to gain better steering response and more in-corner steering, but at the Worlds we needed a different amount of caster to eliminate traction roll. So I knew we needed to make the suspension mount a few millimeters longer so the upper arm could have a greater range of caster angle adjustment to cover any special situations like those we encountered.

I created several different upper arm mounting designs which we produced in several pieces, and sent them to the team for testing. Luckily all the drivers confirmed my favorite design which I expected to work best … so I could finalize the front suspension. Then to control and adjust the flex at the front of the car, I wanted to find a way to mount the suspension holder to the bulkheads and connect it to the radio plate but still give it the ability to adjust how stiff or loose the flex of the assembly would be. Again I did several different prototypes and tested the influence on steering and forward traction; I was seeking the design that would be the best compromise of both these characteristics. In the end I chose the design where the suspension mount was mounted with one screw from the side to the bulkhead, while at the same time the suspension mount was connected with two screws to the radio plate. That design allowed me to change the flex very quickly, since I could easily remove one of the upper screws which had an immediate influence on flex.

While the early stage of NT1 development was running fairly quickly, I got into the familiar but unfortunate situation where my priorities had to be shifted between multiple projects. I had to finish up some details of the new T4’15 which had to be ready on time for the winter season, and after that I was locked for a long time on the X1 project which had a definite deadline to get the car to customers before Xmas. So NT1 development had to be postponed, but any time I could find a small amounts of time in my schedule I would dive back into working on the NT1.

After the release of the T4 in autumn, we had to make a serious decision on whether to work ultra-hard on the NT1 to get a full pre-production car ready for the coming World Championship – which would mean postponing the X1 project – or travel to the Worlds with the current car and continue the work on the X1. At first I was not completely satisfied (or happy) that we decided to put the priority on the X1 and to go to Worlds with the current NT1, but considering the fact that we would run small-diameter tires at the Worlds I was easily convinced. At the end I was very happy that we made this decision, as Alex was able to win the World Championship with the current, soon-to-be-retiring NT1 platform. That was a very nice farewell to the previous platform.

After I finished the X1 project and handed it over to our marketing and sales department, I could finally jump back into the NT1 project. Meanwhile, plenty of things had gathered in my mind so I had an even more clear vision of where I wanted to go with the next development and actually that made development run that much faster.

While finalizing the design of the bulkheads, I could not miss the opportunity to integrate the ball-bearing equipped anti-roll bars mounts directly into the bulkheads. We had a lot of positive experiences with this anti-roll bar system from the T4, and I really wanted to have this great feature in the new NT1. The ball-bearing equipped anti-roll bars makes working on the car so much easier, and you can quickly adjust the anti-roll bars (which also work much more precisely). What used to be a pain was now super easy; using only a 2mm hex tool you could install and adjust the anti-roll bar without need to disassemble anything. I redesigned the bulkheads which hold the ball-bearings so the anti-roll bars move smoothly and ultra-precisely; all wobble and excess play of the anti-roll bars has been removed.

 Once the bulkheads and upper and lower suspension mount designs were chosen, I had to finalize the radio plate. There were several different radio plate designs, with the only differences being the different amounts of flex and how the flex was achieved. I still recalled the recent Euros where we were looking for more steering and thus removed the screws which connected the radio plate to the front bulkheads. We also experimented with loosening the screw that connects the radio plate to the steering system, and I remembered how much significant change that made to the car. As such, one of the designs changes of the new NT1 radio plate was to introduce a new flex bushing to mount the steering system to the radio plate. When you need to have the car stiffer, you use the flex bushing which eliminates the radio plate flex; however if you were looking for more steering, you could give the car more flex by removing the flex bushing and connecting the steering post directly to the radio plate.

 All these changes were immediate improvements with the large-diameter hard tires, so I was very confident and satisfied with the progress. However, I was still not perfectly happy with the steering; the new aluminum framework made the car react differently than I was used to with the composite bulkheads and the steering was still not according my liking. From my electric touring car experience I knew that I needed to work on Ackermann and bumpsteer. I wanted to keep and use the original steering blocks and steering system, but when working with these I always hit a limitation or restriction somewhere. One of the solutions was to update the bulkhead design but that would have influence on many other parts so I decided on an easier way – to update the steering block design and remove the rear fixed part and replace it with graphite extensions so I could have flexibility in moving the Ackermann position and the linkage position. I ended up with 4mm lower bump steer positions, three Ackermann positions, and adjustable bump steer which had great influence on steering characteristics. This combined with the new steering system finally made me happy, and the car had the same responsiveness and reactive steering that I was used to on the previous NT1.

To ensure that it was not just my personal impressions, I arranged for new steering system prototypes to be sent to the team and I anxiously awaited their feedback. Thankfully, everyone liked this configuration so I could approve the mould modification for mass production. Since we had to rework the mould – which is by the way the most expensive part of any project – I decided to take the opportunity to integrate Aero Disk mounts to the steering blocks. The Aero Disks, which we successfully used on the RX8, make the car more stable and increase traction. With this new feature I was forced to also update the rear uprights to integrate the Aero Disks there as well. This meant that I had to defend the requirement for more investment into the moulds, but I was convinced that in some particular track conditions, the Aero Disks would greatly help the performance of the car.

With time running down very fast, I needed to quickly finish the specs of the new kit so production could start. The prototypes were still running and I was collecting feedback and some other ideas and suggestions from the team. Most of the ideas were tiny, but they resulted in nice features that make it much easier to work on the car. I was very happy that the parts I put into the “do not change” list went successfully through the testing phase on the new prototype, and everyone confirmed my early predictions. By the end of February I had approved production of most of the parts, and by early March we finalized the last details. Production has now been running at full capacity, with a scheduled deadline to start shipping the kits first week of April. It seems to us that this is another industry record when it comes to speed of production!

I am satisfied with the overall specs of the new car and I am sure that once we get into the 2015 season there will again be new ideas and things to try; now with the aluminum bulkheads, I will have greater flexibility to test new ideas. So I am very confident that with the new platform we will be even stronger and faster with everything, and as such will be able to provide our customers with the best of the best. I am very excited to see you all at the race tracks with your new NT1 … and please know that I am always ready to help you with your questions or comments.  A lot of thought went into the design of the new NT1, and we are sure that you will notice the improvements as you make your way to the Winners Circle.