Riven, a hypocycloid clock

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Project by Derek Hugger posted 01-26-2014 04:03 AM 7565 views 34 times favorited 26 comments Add to Favorites Watch

Riven is a motor driven wooden clock aimed at tearing apart traditional horological reduction methods. It is the first clock to use a system of dual stage hypocycloid reducers on a single shared rotation axis. With a design aesthetic inspired by tourbillons, Riven’s name applies also to its forms. For a brief moment at both noon and midnight, every gear, support, hand, and frame will align. An instant later, the forms split apart as each follows its own unique eccentric motion.

The idea to use hypocycloid reducers as a means of reduction in a wooden clock came about roughly two years prior to the idea of Riven. My first successful implementation of a dual stage hypocycloid reducer was in my Voor Vander clock. Admittedly, the number of pins and lobed gear teeth used to create Voor Vander’s 12:1 reduction was a once in a lifetime lucky guess on my part. I made up some numbers, put them together, and serendipitously happened to stumble upon the exact ratio I needed. I knew I would not be so lucky in coming up with Riven’s geometry, and so I had to take a step back to truly understand how these mechanisms worked.

I spent several hours generating a handful of hypocycloid designs in CAD, testing their reduction ratios by creating 3D animations of the motions each design would produce. I then had to determine from a mathematical standpoint why they moved the way they did. Frustration ensued. I came up with dozens of equation variations, but none of them worked with all my tested designs. After weeks of failure, I was finally successful in generating an equation that described the motion of all the designs I had created and tested. From there, I built a small software program that would iterate through all possible gear tooth combinations and return back only those combinations whose output matched the desired reduction ratio. After that, the design work began.

From a technical achievement standpoint, I could not be happier with Riven’s end result. Its mechanisms and the math behind them proved to be challenging problems, and as such, they gave me an even greater sense of accomplishment when finally solved. I am thrilled to be able to share the mechanisms and the design of this unique clock.

More information about Riven, including woodworking plans are available on my website:

A video of Riven in action is here:

If you’d like to learn more about hypocycloid reducers or would like to create your own, check out my tools page:


26 comments so far

View oldnovice's profile


7757 posts in 4650 days

#1 posted 01-26-2014 04:32 AM

Outstanding piece of work from design, fabrication, and build! You sir, are in a class by yourself on this sit; these designs standout from the rest as they are not static pieces of wood and seem to be “alive”!

-- "Facts do not cease to exist because they are ignored." -- Aldous Huxley

View wseand's profile


2796 posts in 4324 days

#2 posted 01-26-2014 04:37 AM

Just spectacular, an incredible amount of designing involved.

Very nice piece.

View Kryptic's profile


294 posts in 2943 days

#3 posted 01-26-2014 04:40 AM

u tube it


working ?

View Kryptic's profile


294 posts in 2943 days

#4 posted 01-26-2014 04:43 AM

please : )

View Derek Hugger's profile

Derek Hugger

48 posts in 3241 days

#5 posted 01-26-2014 04:51 AM

Kryptic, I did. The link is above.

View LeTurbo's profile


234 posts in 2868 days

#6 posted 01-26-2014 07:16 AM

That is bizarre, and I love bizarre! I’m impressed at the background research you did … “I built a small software program” ... yowza. I’m happy if I can manage to put a basic jig together.

View TonyWard's profile


748 posts in 5611 days

#7 posted 01-26-2014 07:45 AM

Not sure I understand what you’ve achieved, but it looks great and an exhibits your craftsmanship, well done!

View stefang's profile


17040 posts in 4617 days

#8 posted 01-26-2014 12:54 PM

Quite an accomplishment and also very pleasing to the eye.

-- Mike, an American living in Norway.

View MalcolmLaurel's profile


303 posts in 2906 days

#9 posted 01-26-2014 12:56 PM

Very cool…

-- Malcolm Laurel -

View Derek Hugger's profile

Derek Hugger

48 posts in 3241 days

#10 posted 01-26-2014 01:18 PM

Thanks for the kind words, everyone. Tony, if you’re interested have a look at this file. It gives an overview of what the mechanism is and how it works.

View Derek Hugger's profile

Derek Hugger

48 posts in 3241 days

#11 posted 01-26-2014 01:28 PM

There are a few more things about the clock I forgot to mention…

The minute hand “floats” around the perimeter of the clock using ultra high pull neodymium magnets. The ring the hand rides on does not move, and the part that does is over 1/4” away from the hand.

There is also a mechanism to help prevent mechanically overloading the motor that drives the clock. It is a combination clutch and fuse that uses magnets. If any of the hypocycloid mechanisms in the clock bind, if they require higher torque than normal, or if somebody decides to stick their finger in the clock, this clutch/fuse mechanism breaks free, temporarily stopping the time, but saving the motor. A few seconds later, the mechanism automatically attempts to reengage to start the clock back up again.

View steve_in_ohio's profile


1195 posts in 2893 days

#12 posted 01-26-2014 01:43 PM

Wow, that is amazing, looks very time consuming, great work

-- steve, simple and effective

View Oldtool's profile


3351 posts in 3473 days

#13 posted 01-26-2014 01:56 PM

Outstanding creativity and mind bending to say the least.
Have you ever considered a medium other than wood for these clocks? This clock would look fantastic in all clear plexiglas.

-- "I am a firm believer in the people. If given the truth, they can be depended upon to meet any national crisis. The point is to bring them the real facts." - Abraham Lincoln

View Katzenhammerz's profile


1 post in 3536 days

#14 posted 01-26-2014 02:07 PM

Love this! Outstanding!

View TimWood's profile


196 posts in 3524 days

#15 posted 01-26-2014 02:20 PM

You should QUIT woodworking…now….no more saw dust for you! [Soup Nazi] if your mind can wrap around a project like this, woodworking is not for you….you should be working on the country’s energy situation.
A government van will pick you up in the morning.

-- Tim Harrelson

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