Saturday, September 1, 2012

Broken Moment

Back in the spring I mentioned I was trying to make my muni lighter, but I never got around to posting the details, until now.

Weight matters because it affects acceleration, deceleration, hopping, and the response of the uni.  The most critical location to remove weight is on the wheel.  This rotational weight is the biggest contributor to the factors I mentioned.

So back in March I took my my unicycle apart, down to the nuts and bolts, and weighed everything on an electronic scale.  I didn't want to make any assumptions about where I could remove weight.
(Google spreadsheet of part weights)

I researched and purchased lighter weight parts.  Here's what I replaced and the weights:

Old PartWeightNew PartWeightSavings
Odyssey Trail Mix pedals566 g / 1.25 lbsWellgo MG-1 Ti pedals300 g/ 0.66 lbs266 g / 0.59 lbs
KH Moment cranks - 125mm/150mm585 g / 1.29 lbssame, but aggressively milled444g / 0.98 lbs141 g/ 0.31 lbs
Duro Razor 24x3.0 tire1421 g / 3.13 lbsPanaracer Fire FR 24x2.4850 g / 1.87 lbs571 g / 1.26 lbs
24x3.0 DH stock tube425 g / 0.94 lbsSchwalbe A 10 24x1.5/2.5165 g / 0.36 lbs260 g / 0.57 lbs
KH two bolt seat clamp67 g / 0.15 lbsWoodman Deathgrip SL Ti11 g / 0.02 lbs56 g / 0.12 lbs
1294 g / 2.85 lbs

That brought my muni weight down from 17.91 lbs to 15.06 lbs... almost 3 lbs!  And all but 0.12 lbs of that was rotational!

The tire and tube change removed 1.83 lbs of weight at the outside wheel, where weight is the worst. That's huge. But the tire is less wide, has weaker sidewalls, and the tube is thinner and more prone to flats (I got one in June).

The pedals and crank changes removed 0.9 lbs of weight.  I love my magnesium pedals with titanium spindles.  When I held one in my hand it the lightness was incomprehensible.

When it came to the cranks, I had seen a few examples online of people drilling and milling material away to make them lighter.  I remembered a friend of mine had a milling machine in his garage and he was willing to do some work for me. Thanks again Mike!!

Here's the before and after:

We went extreme.  It should be clear to anyone that removing so much material would significantly weaken these cranks.  But I'm lighter than the average rider and I don't do big drops, so I figured they had a good chance of working for me.  And they did... for about 5 months.

This morning I went back to Whiting to power up some more hills.  On the White trail I was on attempt four of a hard climb when PING!  I stepped off as if I was stopped by a root and found my pedal was on the ground.

When I first rode these cranks I feared if they broke I might get cut in the leg by the resulting sharp spikes.  My Achilles tendon was going to get severed.  Thankfully that didn't happen.  I'm also thankful I wasn't in a race or out of town.  In fact, I was at the trails closest to home.  Though, I was about as far away from the parking lot as possible.  I jogged back to at least get some exercise out of the trip.

On a positive note, I got home and ordered some new cranks.  This year Kris Holm replaced the Moment cranks with Spirits.  They're made of 7050 aluminum instead off 6000 series aluminum, making them lighter.  In fact they're 424 g / 0.93 lbs per pair, which are actually a bit lighter than my crazy milled Moments!  I got a few other goodies too.

Muni at Whiting and Webster Park - 2012-09-01

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