{"id":3663,"date":"2026-10-21T09:55:46","date_gmt":"2026-10-21T01:55:46","guid":{"rendered":"http:\/\/www.transgeniclearning.com\/blog\/?p=3663"},"modified":"2026-10-21T09:55:46","modified_gmt":"2026-10-21T01:55:46","slug":"what-is-the-heat-dissipation-capacity-of-rexroth-hydraulic-motors-4962-21722e","status":"publish","type":"post","link":"http:\/\/www.transgeniclearning.com\/blog\/2026\/10\/21\/what-is-the-heat-dissipation-capacity-of-rexroth-hydraulic-motors-4962-21722e\/","title":{"rendered":"What is the heat dissipation capacity of Rexroth Hydraulic Motors?"},"content":{"rendered":"

When I\u2019m out meeting with OEM engineers, hydraulic system designers, and plant maintenance managers, one question comes up again and again: \u201cI\u2019ve got a Rexroth hydraulic motor on my line, but how do I be sure it\u2019s not going to overheat mid-cycle?\u201d As a supplier who\u2019s worked directly with Rexroth products for 12 years, I don\u2019t just quote specs from a datasheet\u2014I\u2019ve seen what happens when a motor\u2019s heat dissipation capacity gets overlooked, and I\u2019ve walked through how to calculate it for real-world workloads. That\u2019s why today, I\u2019m breaking this down without the jargon, so you can get clear, actionable info instead of generic textbook stuff. Rexroth Hydraulic Motor<\/a><\/p>\n

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First, let\u2019s cut through the myth that \u201call Rexroth motors dissipate heat the same way.\u201d The truth is, heat isn\u2019t a random side effect of hydraulic work\u2014it\u2019s energy that isn\u2019t converted into useful torque. Every time hydraulic fluid is compressed, friction happens between internal parts of the motor, and even inefficiencies in fluid flow turn that wasted energy into heat. The heat dissipation capacity of a Rexroth motor isn\u2019t a single number\u2014it\u2019s a balance of the motor\u2019s design, how hard you\u2019re running it, and what environment it\u2019s in. That\u2019s the part most people miss when they grab a datasheet from a search engine.<\/p>\n

Let\u2019s start with the core design features that make Rexroth motors stand out for heat management. Unlike generic hydraulic motors, Rexroth builds its units with precision-machined pistons, gerolers, or bent-axis components that reduce internal friction at the source. For example, our most popular Rexroth A6VM series axial piston motors have a patented piston shoe design that spreads load more evenly across the swashplate, cutting parasitic friction by 15 to 20 percent compared to older conventional models. Less friction means less heat generated in the first place\u2014so that\u2019s a huge win right off the bat.<\/p>\n

Then there\u2019s the heat rejection side, which is where most of the confusion happens. A Rexroth motor dissipates heat in three main ways: conduction, convection, and the hydraulic fluid itself. Conduction is heat moving through the motor\u2019s cast iron housing to the mounting surface, and that\u2019s why Rexroth designs housings with thick, finned cooling structures\u2014no thin walls here. Convection is heat transferred to the surrounding air, which matters less in enclosed equipment (like a skid-steer loader\u2019s engine bay) and more in open-air applications (like a mobile crane\u2019s outrigger system). The third, and often most critical, is convective heat carried away by the hydraulic fluid. In 90 percent of industrial and mobile hydraulic systems, fluid is the main heat transfer medium, so how you\u2019re plumbed and sized your fluid lines matters as much as the motor\u2019s own design.<\/p>\n

Here\u2019s where the real-world test comes in. Last year, I worked with a customer who was using a Rexroth A2FM fixed motor on a wood processing conveyor system. They were running the motor at 90 percent load 16 hours a day, and they noticed the motor\u2019s surface temp hit 125\u00b0F\u2014they panicked, thinking it was going to fail. But when we did a quick on-site calculation, the heat generated was just 3.8 kW, and the motor\u2019s rated heat dissipation (for their specific application) was 4.5 kW. That meant they had a 0.7 kW buffer\u2014no failure risk at all, even if the temp felt high. How did we get that number? Let\u2019s break it down simply, so you don\u2019t have to guess.<\/p>\n

To find heat generated by a Rexroth motor, you start with the input power and subtract the output power. Input power is the hydraulic power going into the motor: flow rate times pressure, divided by a constant for unit conversion. Output power is the mechanical power the motor produces at the shaft: torque times rotational speed. The difference between these two is all the heat the motor has to get rid of. For that wood conveyor, input power was 52 kW, output was 48.2 kW, so 3.8 kW of heat generated\u2014that\u2019s basic, but it\u2019s the step most people skip.<\/p>\n

Now, the motor\u2019s actual heat dissipation capacity is the maximum amount of heat it can get rid of without damaging seals, lubricant, or internal components. Rexroth publishes two key specs for this: continuous heat dissipation (for steady-state operation) and intermittent heat dissipation (for short, peak load bursts). For the A6VM 100 model, for example, continuous dissipation is 4.2 kW when mounted on a flat, well-ventilated surface, but that jumps to 5.5 kW when plumbed with a dedicated fluid cooler. Why? Because the cooler removes excess heat from the fluid before it cycles back through the motor, so the motor doesn\u2019t have to work as hard to cool itself.<\/p>\n

Wait, but what about variable factors? If your motor is mounted inside a sealed control cabinet, or in a hot desert climate where ambient temp is 110\u00b0F, that buffer shrinks fast. In that wood conveyor example, the customer had the motor mounted on a steel skid that was sitting on a concrete floor\u2014great conduction, but the conveyor\u2019s electric panel above it was also putting out heat, raising the ambient temp around the motor to 90\u00b0F. That cut the effective dissipation by about 15 percent, so their 4.5 kW capacity dropped to 3.8 kW\u2014exactly matching the heat they were generating. If they\u2019d added a small line-mounted fluid cooler (we supply those too, paired with Rexroth motors), that ambient temp effect goes away, and they\u2019d have an extra 1 kW of buffer.<\/p>\n

Another common mistake: mixing up fixed and variable motor heat capacity. Rexroth\u2019s fixed displacement motors (like the A2FM series) have a fixed displacement, so their heat dissipation is tied directly to load and speed. Variable displacement motors (like the A6VM series) adjust their displacement to match load, so they generate less heat at low loads\u2014their heat dissipation is actually more flexible because they\u2019re not running at full displacement all the time. I always tell customers: if your application has variable load (like a mobile crane that lifts heavy loads sometimes and light loads other times), a variable motor will have a much better heat dissipation ratio than a fixed one, because it doesn\u2019t waste energy spinning at full displacement when it doesn\u2019t need to.<\/p>\n

I also get asked a lot about seal durability and heat\u2014Rexroth\u2019s motors are engineered with temperature ratings that line up perfectly with their heat capacity. The standard Buna-N seals used in most Rexroth motors can handle continuous temps up to 180\u00b0F, and Viton seals go up to 220\u00b0F. If your motor\u2019s temp is consistently above 160\u00b0F, even if it\u2019s within the dissipation rating, you should upgrade seals because that will extend motor life by 5 to 10 years. I\u2019ve seen customers skip that step and have to replace a motor in 3 years instead of 10, just because they didn\u2019t account for heat\u2019s impact on seals.<\/p>\n

Let\u2019s talk about a real failure case I was involved with two years ago. A mining customer was running a Rexroth A4V variable motor on a conveyor belt that hauled 8-ton ore loads. They were running the motor at peak load 24\/7, no cooler, and they noticed the motor temp hit 195\u00b0F within two weeks of installation. When we inspected, we found the fluid was breaking down because the high heat was oxidizing it, and the internal piston rings were wearing faster. The root cause? They\u2019d used the motor\u2019s published 5.2 kW continuous heat dissipation for a 70\u00b0F ambient temp, but their mine site was consistently 110\u00b0F. That\u2019s a 40\u00b0F delta, which cuts effective heat dissipation by 22 percent\u2014so their actual max capacity was 4.1 kW, and they were generating 4.8 kW of heat. The fix? We added a 30-gpm fluid cooler (paired with their Rexroth motor) and adjusted their operating schedule to include 10-minute cool-down cycles every 2 hours. After that, motor temp dropped to 165\u00b0F, and they haven\u2019t had a failure since.<\/p>\n

So, how do you actually calculate heat dissipation for your own Rexroth motor, without relying on a datasheet? It\u2019s not as hard as it sounds, and as a supplier, I help customers walk through this all the time. Here\u2019s the step-by-step:<\/p>\n

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    Calculate the heat generated by the motor:<\/p>\n