Ken Tech : Euler




This is the freshman effort from a new company, apparently run by a guy named Ken. The cleverly-named Ken-Tech company has delivered its first model. The Euler is a bi-metal design that is not only a relatively risky design from a new company; but it is also a bold design in a growing arena of new, Bi-Metal yo-yo’s.

Bi-Metal is getting alot of hype these days; and for good reason. Bi-Metal yo-yo’s outperform their single-metal parents in a number of categories. These performance gains, thankfully, are in the categories that matter the most to yo-yoers like spin-time, stability and momentum.
The only drawback for many Bi-Metal designs is in the weight-distribution category. Here, the extreme difference between the body material and the rim material can give-rise to a yo-yo that resists movement more than it facilitates. By this I mean that you can get a ferociously-spinning yo-yo, that can also feel clunky as it moves from string to string. This is where a design like the Draupnir truly shines. The Draupnir is a rare melding of the best of both. You get the performance of the Bi-Metal, but the two materials do not feel like separate parts. The Draupnir feels like a single-material throw that just happens to spin for ever and ever…

It is into this treacherous virgin territory that Ken-Tech has chosen to put down its initial roots. To do this, Ken-Tech could have chosen a less-risky route. Yes, it would have been easy to just make a single-material throw with tried design. They could have copied an existing design. That would have kept it in the 55-57mm range; at around 67g - just like all the rest of them out there like the Draupnir, Agonist, Space Cowboy, Palpatation, Schnieder, TISS, Laser, etc. Instead, they chose to chart their own territory:

53mm x 43mm : 62.9g

The Euler has what I surmise is a blasted 6061 body, that has closely-machined Stainless Steel rims. The rims are bit larger in proportion to the body than the Draupnir, or the YYM Agonist. I assume that is to compensate for the decrease in diameter of the yo-yo itself. The rings are wider and flatter, but are machined to carry the curve of the yo-yo in a smooth curve. The fit, while not in the same league as the YoyoRecreation or YoyoMonster; is smooth and the gap between the body and the SS is minimal and flush. The Konkave bearing that it comes with it while expensive; is one of the best in the business. It is smooth, quiet and …concave. That is better than flat; for me. The spin is smooth and ferocious, the stability is stupendous for such a small diameter return top.

The result is a compact, super-fun, super-easy, superior performing yo-yo that is a pleasure to play with. I have not had the pure enjoyment of playing a yo-yo like this since the Hatchet from YYO. I think that the decreased diameter is one of its greatest strengths. Not only are there very few Bi-Metal designs that have such a small diameter, but the small size allows for more intricate tricks with more control. I just was not used to having such a small package be able to do the things it was doing - for as long as it was doing them. Awesome.

Because the Euler is smaller than most Bi-Metal designs out there, a few notable features about Bi-Metal and decreased diameter cropped-up. One area that the Euler does not do as well as some of its larger rivals is the stability category. Because the Euler is 2-2.5mm smaller than most other designs, it does tend to tilt a bit easier than other, larger Bi-Metal designs. This is NOT to say it is easy to tilt. What I mean is that it is not as rock-solid as the larger diameter throws are in this area. Where it does shine is that while single-material yo-yo’s that tilt are destined to spin-out, recovery is possible with the Bi-Metal performance of the Euler. Indeed this is one of the “fun” aspects of playing the Euler: you CAN recover from tilts to go on to do long combos and multiple tricks! This leads me into territory that I do not go with most yo-yo’s and brings a smile to my face when I can “save” something that I know mere mortal yo-yo’s would be rolling on the floor.



The Bi-Metal design with small diameter does have one consequence for the Euler: its is not as fast as I would have expected for both its size and weight. I think this is because the rings are fairly wide and flat.The contrast of the SS rings and the small, light 6061 body creates that feeling of two materials on the end of the string instead of one that may inhibit accelaeration just a tad vs. a single material. While the Euler is not slow, it is not the speed-demon, like the Sturm-Panzer Schneider with the same basic shape and weight. I would not call it slow, I would have expected the Euler to be in the 65-67g range given its speed.

I bought the Euler mainly to support the yo-yo community and those that are willing to take risks. In that regard I had few expectations beyond the glowing description on YYE. For taking that risk; I was well-rewarded. Ken-Tech has certainly taken risks with its first effort in the industry. For that; Ken-Tech has been rewarded by the yo-yo gods with a fun, high-performance yo-yo that can play with anything out there. It is a solid design with superior performance I would expect from a more experienced industry veteran. I would recommend this to anyone seeking a smaller Bi-Metal option. It is everything I would expect - but with a dash of pleasure on top.

These have been mostly sold - so finding one might not be easy. If you do find one; you will be well rewarded for your effort. I eagerly look froward to seeing what they come up with next.


Great review, and nice pictures as well :smiley:

The Euler is a bit outside my price range but I nonetheless always thought it looked like a great throw. Your review clearly confirms that.

There is one left in the YYE store as I write this so someone still has a chance to snag one!

Thanks for reviewing this! I’ve always been curious about this yoyo.

It is not just ‘you’. That is just the way the rims ‘mate’ to the body halves. Not the only Bi-metal like that.

About 4 years ago Northern spins released a short run of a yoyo named the ‘Helix’.

Not an identical twin obviously, lol. But a very similar concept: smaller diameter, 6061 body and stainless steel rims with borderline weight distribution.

The Helix like the Euler share similar fit. <a slight step down from rim to body. You can actually feel the deviation while holding the yoyo. But it has no negative effect on play.

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An excellent explanation. Some companies hide this by making changing the angle where the two metals meet making the part where they come together the hypotenuse of the angle.

I have talked to some companies that make bimetals and it is interesting how they do the over the aluminum joining. As it was explained to me by one company, they actually super cool the aluminum body so it shrinks a little and then they slide the steel ring over it. After the body warms back up it locks the ring in place. There is quite a bit of cool science that goes into putting one of these together and I would hazard to guess that a lot of math is required to get that joining point perfectly blended together.