TQ's Harmonic Pin Ring Motor is Simpler Than it Seems - Eurobike 2022

When Trek launched the Fuel EX E just a few days ago, the biggest news was not the Fuel EX E itself. It was the motor that drives it. Trek likes to use the right tool for the right job, having chosen the minimalist Fazua motor for their cross-country Supercaliber and the full-power Bosch for the heavy-duty Rail. Problem is, there weren’t a compelling option in between the two that would suit the Fuel EX E. But there is now.


Hidden among the countless wholesale e-bike-component booths that tessellate Eurobike 2022’s remote Hall 8, TQ Systems started buzzing with activity the moment the show opened. With experience in industries like robotics, aerospace, and medical technology, the Munich-area engineering firm may seem like they’d be a little above making parts for electric bikes. But one of their specialties happens to be just too perfect not to be on a bike.


Despite the very futuristic name, ”harmonic pin ring,” TQ’s motors aren’t new to bikes. They actually entered the market over a decade ago with this beast first featured on some models from Haibike. It offered 120 Nm of torque. By comparison, the full-power Shimano EP8 offers 85 Nm. The new IQ motor used on the Fuel EX E is the result of dialing back that overkill with the benefit of 10 years of experience. You can read what all that means on the trail in Matt Beer’s review of the Fuel EX E. It covers loads of details that we won’t cover here, including the most important one: how it rides. But what we wanted to understand, at the most basic level, was how it works.


Thankfully, there were a couple bits and pieces of TQ’s motor at their booth, though by the time we got there, TQ had hidden them because too many suspicious competitors were taking too many high-resolution photos. The exploded version of the whole motor, to an untrained eye like mine, just kinda looks like… a motor. But what it doesn’t look like is an e-bike motor. Traditionally, an e-bike motor needs a device that offers “reduction,” which I put in quotes because I needed TQ to explain it to me. In the case of an e-bike, it’s the method used to get a front chainring spinning at the desirable speed and with the desirable amount of torque. This is usually done with a belt or a chain or a stack of cogs. But TQ does it with its harmonic pin ring. And because it’s concentric to the rest of the motor components, it’s almost hidden among them. That’s why the Fuel EX E’s motor unit is so small and light.


While electric motors are good at spinning fast, they need reduction to turn their natural talent for speed into something more useful on an e-bike. The TQ e-bike motor’s approach to the harmonic pin ring concept does this in a unique way. There is an inner gear that is on an eccentric, which is driven by the motor. It is one tooth smaller than the outer gear, which will be what drives the chainring. Because that inner gear is not rotating around its own center, but around the center of the bearing to which it is attached, it forces the gears of the outer ring to move, just much slower than it does.


There are benefits to this beyond light weight and small size. It creates an instant, direct relationship between input and output. That’s why it’s so useful in robotics. This is similar to the mechanisms used in robotic open-heart surgery. It’s why the power comes on so naturally on the Fuel Ex E. It’s also why it’s so quiet. There’s no slop like there is when there are gears on gears on gears. In fact, the teeth of the inner gear don’t ever really leave the teeth of the outer gear. They almost just slide over each other. And that’s fine, because there’s very low friction between the two. The inner ring is aluminum, but the outer ring is a sort of polymer. But still, TQ has tested their motors to over 20,000 miles, and they still behave like they were designed to when they were new.


It just takes a very high degree of precision to make a system this durable and this efficient, so despite its simplicity, it’s still a pretty pricey little gadget. But time will tell if that changes down the road. The TQ booth was filled with representatives from other brands, ready to get in line. And though, like Fazua, Bosch, and Shimano, the motor itself will stay more or less the same as we see it pop up on other bikes in the coming years. But it could also be scaled up, or even scaled down to fit other applications. And when it does, now you won’t have to wonder how they did it.

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