Choose your location and language

Episode 20: Rubber - the heart of the coupling | KTR Systems


Text of the current episode:

Julia Ures: Good to have you here! Welcome to a new episode of "In Sight KTR"! Our motto today is "Give rubber!". We already have a rubber ball like this, which if you're following our video, you can see here in my hand right now. A small rubber element, about three centimeters in diameter, which I think actually works as a rubber ball. If you're tuned in to us on the podcast, you may have just heard that as this little rubber ball tits up on the table. That's because our topic today is "Rubber, the heart (piece) of the coupling."


It's good to have you with us. I'm Julia Ures, and I'm here to guide you through these 20 minutes. 20 minutes, that's always the time frame in this podcast and video cast that we give ourselves to answer these questions that have come from you on the topic, to answer as many questions as possible. And as always, I have guests for this here in the studio and I would like to welcome very warmly, Martin Kricke. He is Thinktank Manager Technology and has been with KTR for three years. Nice to have you here in this studio today.


Martin Kricke: Thank you for the invitation!


Julia Ures: And sitting with us in the middle is Stefan Berndt, Head of Calculation and Standardization. How long have you been with KTR now?


Stefan Berndt: I started in May 2008, so not quite, 13.5 years, so a little more than 13.5 years.


Julia Ures: Quite a while now. Mr. Kricke, how did you actually get here to KTR? Have materials always been your topic?


Martin Kricke: Yes, I actually completed a relatively unspectacular degree in mechanical engineering, specializing in automotive engineering, in Cologne. And at that time, of course, Ford Cologne is obvious, I was already working at Ford as a student. Yes, fate or not? Even then I came into contact with elastomers, and that was almost 40 years ago. And I haven't been able to get away from it since. So even during my studies I came into contact with rubber and the development of rubber products.


Julia Ures: What was it about this material then that made you stick to it, so to speak, that you said, this is something I'm particularly interested in?


Martin Kricke: The exciting thing about this material is that, even today, relatively little research has been done on it compared to metallic materials. Sure, there are many development teams working on it, but you're still very, very far away from the knowledge you have about metallic materials. And personally, I'm thrilled that this material keeps surprising us, both positively and negatively.


Julia Ures: We might come back to that later. I would like to know more about the extent to which the material surprises you.


Mr. Berndt, I just said that you are the head of calculation and standardization. When we now think of couplings and rubber and think about it, perhaps the first thing that comes to mind for many is elastomers in couplings. Probably most also think directly of the ROTEX with the spider.


In connection with today's topic, however, quite different product inquiries land on your desk. Can you take us along a bit and explain which products we are talking about and how the process works when a customer inquiry reaches you?


Stefan Berndt: First of all, you have to explain the classic tasks of a coupling. Primarily, the coupling must transmit torque and compensate for misalignments. But the couplings we are talking about today have to do even more. In particular, they are used in diesel engine applications, where the coupling strongly determines the dynamics of the entire drivetrain. In other words, a properly designed coupling also means that everything basically runs very well within the powertrain and no problems occur. To get there, you first have to perform a calculation. And, of course, this is done by us.


Julia Ures: You also frequently come into contact with very special applications. What kind of special applications are we talking about here and what special challenges do they bring for you?


Stefan Berndt: For example, I came here this morning via the highway, and there are a lot of construction sites there at the moment. There we mostly see aggregates that are used for earthmoving, i.e. the excavator, the wheel loader, for example. Of course, there are diesel engines in them, which then drive something and, of course, our coupling in between. At a construction site, for example, a compressed air supply must also be guaranteed. This compressed air supply is also provided by an internal combustion engine, which in turn drives a compressor. If we now leave this subject area of construction sites and take a completely different one, then that would be, for example, the emergency power supply at a hospital. A hospital is also regularly connected to the normal German energy grid. If it has a problem, an emergency generator has to start in the background. Of course, there is also the structure, combustion engine, KTR coupling and generator. And so each application has its own special characteristics. I would say that in the medical sector in particular, it is very easy to imagine that it must be ensured that special incidents are also covered. And these must be taken into account in the design.


Julia Ures: Now I imagine your job a bit like this: that you are a collector, a collector of information. Does that work?


Stefan Berndt: That is correct. Yes. We maintain huge libraries of information in the background so that we can also respond quickly and effectively to customer inquiries.


Julia Ures: Mr. Kricke, when Mr. Berndt has collected enough information on a certain topic area or a certain task or challenge, the whole thing ends up with you. What happens then?


Martin Kricke: Then, first, if it is a non-existing product, a design is created, specific with the connection to the customer aggregates. If an existing coupling, an existing coupling size can be used, then it is ultimately a matter of selecting the elastomer material. Of course, this depends crucially on the customer's requirements. For example, temperatures, high temperatures, low temperatures, other environmental influences, chemicals, ozone, sunlight. These are all basically disturbance variables that have to be taken into account when selecting a suitable elastomer. Of course, all of this runs parallel to pure mechanical strength. First of all, the coupling must of course drive the machine, i.e. transmit the torque. But of course it also has to do this for a certain time. And this time factor in particular has been increased enormously in recent years or decades. In the generator sector, we are talking about 15,000, 20,000 operating hours. That is, to compare it with a passenger car: Your vehicle, or at least at the time when I was still in the automotive industry, was designed for 1000 hours. So what I'm saying is, a machine for which KTR provides a coupling has to work about 20 times longer. And that's actually what makes it so difficult, these long-term effects.


Julia Ures: In other words, that is also the challenge for the elastomer, to last that long without becoming brittle and leaking, what else can happen?


Martin Kricke: Exactly. It can fail completely, it can decompose mechanically, it can dissolve when it comes into contact with chemicals. It can crack, as one or two people know from the car tire that has to be replaced after a few years, you know, because it just cracks. And there are all kinds of different failure mechanisms with elastomers. But this time effect is actually what makes it so difficult. Checking mechanically whether anything works or holds, that's relatively quick, but these long-term effects. And that is, even today I would say, the highest demand, the engines or aggregates or construction machinery, it doesn't matter, it is encapsulated more and more, the exhaust standards are stricter and stricter and that all leads to the fact that one builds more compact, smaller and that essentially the temperatures continue to rise in the engine compartment.


Julia Ures: Now you have also brought us such a beautiful rubber example here. Two such black balls, diameter three centimeters approximately.


Martin Kricke: Exactly!


Julia Ures: What is this, what are you planning to show us now with this?


Martin Kricke: That's actually where I want to test you. Take it in your hand and maybe you, as a non-expert, tell me what you notice, if you notice anything.


Julia Ures: Now I have to ask: are they different?


Martin Kricke: Yes, they are different, of course.


Julia Ures: Okay. That's probably what your question is aimed at.


Martin Kricke: That is the purpose of the question. Whether you find out now where the difference is.


Julia Ures: Okay! I'll take them, so I've just, for those who only hear us,them up in my hand, thrown up a few centimeters, I don't notice such a big difference in behavior now. This one is a little bit firmer, this one is a little bit softer, I would say.


Martin Kricke: And now drop them on the ...


Julia Ures: The right one is a little firmer, I think. Now let's make them bounce on the glass table. Oh! Now something interesting has happened. You've seen it if you watch us in the video now. For the podcast: One ball bounced, as you would expect a bouncy ball to do, the other one didn't bounce at all. Let's do it again. Jo. It falls down like a sack of flour.


Martin Kricke: Exactly! That's exactly the effect we actually want to show here.


Julia Ures: I would have expected otherwise. So it really was a surprise.


Martin Kricke: You can't feel it, you can't see it. Nevertheless, the material is fundamentally different. Experts talk about damping behavior or rebound elasticity. I don't want to go into any more detail about what that is, but Mr. Berndt naturally knows at least as well as I do what influences this has on a torsional vibration-sensitive drive. And that is a very decisive factor, and that is why we actually want to attach importance to it, yes, you say rubber or you say elastomer, but basically it is an umbrella term that has to be specified very, very precisely. And then one customer needs the elastomer that is contained in the rebound-elastic ball and the other customer needs exactly the opposite. And this is designed in conjunction with the calculation and then later implemented in the product. This is of existential importance. If the design is wrong, there will be considerable problems.


Stefan Berndt: We really have to take a close look at the customer's situation, analyze what he wants to do with it, and then decide exactly which elastomer is the most important. Which elastomer do we have to use here so that the customer's requirements work and can be implemented? Because if you make a mistake, for example if you use this one rubber ball in an application that actually requires the other rubber ball, then it can lead to massive problems.


Julia Ures: Now, as a non-professional, I actually fell for this effect, too, so to speak, that you think, oh look, they first give the impression of being pretty much the same. Would you have known, if you just got them in your hand, ah, they fall down like a sack of flour and don't bounce?


Stefan Berndt: These are effects that you can't see and are also difficult to feel. You can only see them later on the test bench.


Julia Ures: Even you as an expert, I am relieved.


Stefan Berndt: Yes, of course.


Julia Ures: The process that you have already described for developing new products sounds very complex to me. And you've already given us a little insight into what it takes. This only works if the departments work hand in hand with each other. And it's probably also relatively expensive. Now let me ask you simply: Why should you do it the way you've described? And what are the advantages for the customer and what are the advantages for the company KTR?


Martin Kricke: The advantage or the requirement for KTR is to respond to these needs of the customer. Mr. Berndt has mentioned that this is very important. And this, of course, also distinguishes KTR from its competitors on the market. I also mean that anyone can produce this ball, this rubber ball, in any place in the world, but the interaction within the product development, the calculation and then also the realization is what makes KTR stand out.


Julia Ures: Can you give us an overview of the time frame, approximately how long does it take? If you get a request on the table and find out that the customer has an application, he has a need, then you first determine what exactly he needs. How long does it take to get the finished solution to the customer?


Stefan Berndt: I've been at it for a good few days now. That means that when I read a customer inquiry, the shortlist is actually already playing out in my head. That means that when a normal inquiry comes in, within a few minutes I already have a pretty clear idea of which coupling solution would be the right one here. Of course, you then have to back this up with a design. In other words, you have to collect a bit of data, take data into account, and then check whether the prediction made in your head is really correct. That means that the pure design time is somewhere in the range of a few minutes to a few hours. So we are not usually in the process for days, but it actually happens relatively quickly. But also because we know this situation, we know the customers, we know the customer's requirement profiles and can therefore also easily deduce that a similar customer already has a similar request, what is really needed and how we have solved it. So that actually happens relatively quickly.


Julia Ures: Mr. Kricke, you just dropped in the beginning, this is a material that surprises you again and again. Of course, this self-experiment here also surprised me, because you really rather expect the Flummi effect. Or that's how it went for me now, that I thought: Now I'll throw it on the table somehow, and it will come up again. And the other one just fell down and didn't react at all or was very sluggish. What are some of the things that still surprise you after you've been working with these materials for so long?


Martin Kricke: One of these balls is natural rubber. This is, as the name says, a natural product, grows on the rubber tree, is harvested. It is a material that is constantly subject to fluctuations. That is, it is not a material like the others, a synthetic one, which comes out of some chemical process, but it is a natural product, which is subject to weather, humidity, temperatures. To always have the same parameters or always the same properties for this ball, it means that you have to constantly control the process and also intervene. So there is not one elastomer compound on a natural basis, that is natural rubber, which is realized once and then it is like that for 20 years, but it changes and you have to start again from scratch every time and intervene to eliminate these natural variations.


Julia Ures: Can you tell from the material, if it is a material that is actually subject to fluctuations, can you tell in advance to what extent it will fluctuate in its properties? Or do you have to examine it intensively for that?


Martin Kricke: Every rubber batch, every production quantity goes through a release process. Even if it has been done a thousand times before, every rubber batch, which is usually around 50 to 200 kilograms in the rubber industry, goes through a relatively complex approval process, in which precisely these fluctuations are determined and then counteracted. That is a considerable amount of work. There are many laboratory technicians who do nothing but this process control all day long to guarantee that the product has the same properties as it did a week or a year ago.


Julia Ures: That' s right, exciting! Mr. Berndt, from the outside one might think that you work with materials in the same procedures and processes and that everything can be planned from start to finish and that it can be played out on the drawing board exactly how everything will react. But it remains exciting for you, too.


Stefan Berndt: Yes, of course! As Mr. Kricke has already mentioned, there are certain deviations. And of course, we also have to take these deviations into account within the interpretation. This means that we usually make a min-max consideration and the truth will then be found somewhere in the middle. As long as you keep to this consideration, you can also carry out the design very reliably.


Julia Ures: Mr. Kricke, is natural rubber actually a material that will eventually run out?

Martin Kricke: No, that is not to be expected, because it is still irreplaceable in certain applications, for example in a large part of our couplings. It has certain dynamic properties that cannot be replicated with synthetic elastomers.


Julia Ures: And does it grow back enough?


Martin Kricke: Yes, there is enough growing back. I did a little research on that in preparation for our meeting here today. Believe it or not, that's 2 billion trees that are in the world, rubber trees that are harvested to produce the feedstock. That of course, like all natural raw materials, is subject to fluctuations. For example, palm oil, cocoa, rubber tree, these are all products that are essentially harvested in Southeast Asia, and are of course dependent on current prices. If the prices are low, the farmer goes and cuts down his trees and plants palm trees to get palm oil. And so it goes back and forth every few years. That means we also have fluctuations in raw materials and, of course, fluctuations in volumes.


Julia Ures: We are approaching the announced 20 minutes, which means that we are also slowly coming to the end of our episode today, which has dealt with the topic of rubber up to this point and a very little bit longer. At the very end, I would like to ask you about the trends. Mr. Berndt, what trends do you see in this sector in which you are active? Where is the journey heading?


Stefan Berndt: We are all familiar with a generic term called downsizing. Martin has already touched on this. It's the same in the private sector, where you might have gotten a car with a six-cylinder engine in the past. Today, the same engine is produced with the same power but with four cylinders. This means a higher level of dynamics for the coupling. Along with a smaller engine comes less installation space. This is simply because the connection then has to be more compact, because basically everything becomes smaller. A smaller installation space then also leads to a higher ambient temperature. In other words, each step in itself is actually relatively small, but in total there are of course a lot of steps that our product has to take. And in the near future, there will be more inquiries about regenerative fuels such as hydrogen. We already know that a hydrogen engine generates about 20% higher dynamics than a comparable diesel engine. Our components must also transmit these higher dynamics. So there are a lot of exciting topics that are not all that relevant individually, but taken together they play a major role.


Julia Ures: Mr. Kricke, is that also your view for the future or your perspective, ...


Martin Kricke: Yes, of course!


Julia Ures: ... these trends that we have heard now?


Martin Kricke: Absolutely!


Julia Ures: Or is there something missing?


Martin Kricke: Absolutely! As a result of this downsizing, as we said earlier, the demands on the elastomer are also increasing, temperatures for example. There is also another factor that is very important, and that is legislation, environmental legislation. Whereas 20 years ago we had many chemicals in elastomers that are now banned, this trend is continuing. In the meantime, we are at the point where elementary components of an elastomer compound are threatening to be put on the index. And so we are always on the lookout for substitute materials without weakening or even destroying the performance of the elastomer.


Julia Ures: That was our episode on "Rubber, to the heart (piece) of the coupling". And we learned that this is a very, very highly interesting material, an exciting material, and also sometimes quite difficult to plan, which always presents you with challenges and, I think, also does not make the work boring. A very big thank you to both of you for coming here. Now the ball does drop. It's the one that bounces a little bit, the one that's a little sluggish and then just stays there. I would like to thank both of you, Martin Kricke and Stefan Berndt, and of course you for watching and listening, for your interest in our episode. Please keep sending us your suggestions, your questions for this format "In Sight KTR - quick questions, concrete answers". We look forward to your questions that you send in, perhaps on very specific topics. Maybe you also say, "In Sight KTR", take on this and that topic, that is also welcome to See you next time! Take care! Bye!

We look forward to your questions and feedback! Mail to!

KTR Insight