Fun with Compass Brake Parts: Twin-Blade Skates


My daughter’s science project this year was an interesting one. She had seen a photo of a scooter with two front wheels.


She wondered whether she could make an ice skate with two blades. Would it offer better grip in corners than a single-blade skate? There was only one way to find out…


There already are twin-blade ice skates, but they have limitations (kind of like training wheels on a bike): the blades don’t pivot, so the skater cannot lean into turns. My daughter wanted to make a twin-blade skate that can lean into turns. “Can we do it?” she asked. That is not such a far-fetched question in a household where metalworking and prototyping are a part of everyday life…


In her project proposal, she listed under resources “fully equipped machine shop” and “welding equipment”, as well as “9 centerpull brake pivots” and “metal bars”. Not to forget an extra ice skate and an extra pair of ice skate blades.

We talked about how to keep the blades parallel, and decided that on the rear, only a single link was needed to keep the blades spaced correctly, since the two links on the front already kept them parallel.


And then we headed to Hahn’s machine shop. She got to work with files, and watched how angle grinders and milling machines work. She donned a dark mask as Hahn welded the pivots onto the blades.

As so often with these projects, they take longer than planned, and the work is too hard or too dangerous for children, so parents tend to do a lot of it. But in the end, she was glad to have a working twin-blade leaning ice skate.


She developed the protocol of testing it all by herself, with no adult input at all. She found that the twin-blade skate does feel more stable when skating one-legged (probably due to the friction in the pivots), but it’s harder to come out of turns and get the skate upright again (probably for the same reason). The main issue is weight – the extra blades make the skate very heavy. It was an interesting exercise for all involved, but like many prototypes, it’s probably going to remain a one-off.

Acknowledgments: Thank you to Hahn Rossman for the use of his machine shop for making the skate.

About Jan Heine, Editor, Bicycle Quarterly

Spirited rides that zig-zag across mountain ranges. Bicycle Quarterly magazine and its sister company, Compass Cycles, that turns our research into high-performance components for real-world riders.
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17 Responses to Fun with Compass Brake Parts: Twin-Blade Skates

  1. Lyle Bogart says:

    Fun! I’m sure she learned even more than she realises!

  2. Edwin says:

    And just like with bikes… so many improvements can’t beat the tried and true.

  3. Maybe fabricate the blades from carbon fiber to save weight? 😉 Then the skates would also be latererally stiff and vertically compliant!

  4. Bryan Willman says:

    That’s great. In more ways than the obvious ones, but I won’t yammer on about it here. But I’m always really glad to see people (young or old) having such experiences.

  5. Chris Lowe says:

    Please tell me she got an A for this! 😉

  6. I am impressed. The principle reminds me of shaving technology, starting off with a single blade back in the dark ages, then going to Trac II twin-bladed razors, then escalation to Mach III, Quattro, and now five or more blades, god knows! And I’m sure BQ contained lots of good examples of credible test protocols. Chapeau!

    • marmotte27 says:

      Yeah, and all the smart guys going back to double edge and even straight razors these days. Like so many other so called innovations, a lot of the latest, greatest etc. stuff actually is just a big rip off.
      But being Jan’s daughter, there is no danger of us seeing huge billbords proclaiming “Mach 4 Twin-Blade Skates provide the smoothest shave… I mean skate” in history anytime soon.

  7. Bill Gobie says:

    Very cool and original! The skates might have come out of turns easier if the blades had a tiny amount of toe-in — arranging the blades slightly closer together at the front. Two-track machines like cars and tadpole trikes need toe-in for stable and self-centering steering. Toe-in adds a bit of drag but it is a necessary evil.

  8. Geoff Hazel says:

    Even harder than manufacturing the skates would be the test equipment to objectively measure results.

  9. N. Zornitta says:

    Well done!

  10. Paul says:

    Design a BB with adjustable valve springs for variable planing.

  11. starground says:

    Love it! Fighting evolution is a tough job, and sometimes it pays off. She must have learned a lot! 🙂
    Btw weight is not that big a problem, my 10-year-old daughters skates weigh more than my hockey skates. It helps to accelerate the spins!

  12. Jon Gehman says:

    I bet we could take 400 grams off the pair without resorting to other materials… it’s at this point that these projects spiral out of control and my children end up learning more lessons about strange adult behaviors and psychology than physics or design…

  13. David Pearce says:

    First of, congratulations on your wonderful, creative children.

    And now for something somewhat different, and yet somewhat the same, TODAY is the day the frigate Hermione departs from Île d’Aix, France (off of La Rochelle), beginning its voyage memorializing Marquis de Lafayette and his voyage in 1780 commanding the original Hermione, which brought military aid to the American revolutionaries and allowed Lafayette to join the Continental Army. The website is:

    (and yes, there is an English page clickable there, although I notice it has not been updated since the sea-trials of last October!).

    Imagine the greatness of learning to build a tall wooden ship all over again, and this whole idea, at least two decades in the making!

    I call the trip a “memorial” and not an exact retracing of Lafayette’s voyage, because I think his trip took 38 days, directly from France and he landed in Boston, while the itinerary for this voyage takes the Hermione to Las Palmas in the Canary Islands, and then also taking 38 days, coincidentally, to land at Yorktown, Virginia. Then it will make gallant calls to ports up the east coast, Alexandria, Philadelphia, culminating in a gala celebration of the Forth of July, in New York City!

    I hope, perhaps, the BQ family and team might be able so meet this great ship at some point this late June / July. I know that La Rochelle is not exactly on the same path as Brest, but at least it IS on France’s west coast, and we owe a lot to our French amis!!

  14. VincentB says:

    The same idea, but with a different construction was on Dutch (where else?) television some years ago: Perhaps she likes to have a look at this site?
    Lovely how young people have the creativity to think out of the box, and then just do it !


  15. Garth says:

    Any thoughts on adding springs to modify lean tendencies?

    Or perhaps consider how bushings are utilized in roller skates to deal create steering through lean? Perhaps the blades would have flexibility to accomplish this? Does one need to more carefully consider the front curve of the blade and it’s effect on turning?

    What other research has been done in this regard?

    Is this line of thinking a dead end or are there still possibilities to try out?

    Your daughter has definitely picked out an interesting question remarkably related to the physics of cycling…

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