Box Dog Bikes Pelican Randonneur -- Finally on the Road!
2013 BDB Pelican, a set on Flickr.
It's been a long time coming, but I finally finished building my Winter-Bicycles-built 2013 Box Dog Bikes Pelican frameset, and took it out for a first ride yesterday. We did ~70 miles on the SFR Lucas Valley Populaire, and the bike performed quite well. Any ride on a brand new bike is bound to have a high probability of problems or require adjustments, but I'm happy to report that -- aside from a very minor seat-height adjustment that I made at the end of the ride -- there were none. The custom rack, decaleur, and headlight performed flawlessly. I do need to think about getting those powdercoated sooner than later since some of the spray-paint is already wearing off at some contact points, but this is minor and expected. There is some very minor fender rub at the bottom of the front fender while going over bumps that I need to sort out. Odd for a low-trail bike is the fact that I get a small bit of shoe/front-fender-bolt interference.
I have a long history of problems with shimmy on rando bikes, so I was curious to see whether the Pelican would have this problem, too. Even though I installed a roller-bearing headset (which has a higher-than-normal amount of friction and therefore is purported to help dampen out the oscillations), this bike does shimmy for me when riding no-handed at 15-18 mph. It is milder and more controllable than on my other rando bikes -- if I just lean forward slightly I can make it stop, and I can ride the bike no-handed confidently. Also, the bike feels solid and confident during high-speed descents -- there was no hint of speed wobbles coming down White's Hill at nearly 40 mph.
The big question for this bike was "Does it plane"? Planing is the name given to an esoteric/mysterious synergy between the natural flex or spring of a bicycle frame and its rider's pedaling motion. This phenomenon is not unlike bouncing on a trampoline at just the right amplitude and frequency so that you go higher with each jump. An overly stiff bike frame may only plane for a heavy rider, and likewise a very light rider may only experience planing on a very flexible frame. When this interaction is harmonious, the bike can feel like it has a slight turbo-boost, which is quite marvelous.
Of the many bikes I've owned, the one that planed the best was a 1993 Bridgestone RB-1. That frame was made with Ishiwata quad-butted tubing, a close approximation of which can be made by simplifying it to 8/5/8 top tube and 9/6/9 down tube. That's exactly what this Pelican frame is supposed to be made from, so I was eager to see if I'd experience the magic. Did I? The jury's still out, although I can say that the bike encouraged me to ride harder and faster during yesterday's ride than I should have, because I was cooked for the second half. The frame overall definitely feels more lively than my 1992 Trek 400 650B conversion. I need to ride the bike more.
Overall, I quite like it.
posted by jim g at 6:49 PM
2 Comments:
Shimmy is a mysterious phenomena that only puzzles the thinking randonneur slightly more than that newly discovered phenomena of planing. I suspect that much of the cause of shimmy is the weight balance of front to rear on either side of the headset/tube fulcrum. Shimmy may be attenuated by shifting one's body forward or shortening the length of the rear lever by placing one's knee on the top tube. High trail bikes utilize the self centering caster of the trailing wheel to minimize any influence on wobbles on the front of the pivot at the expense of light handling and poor acceptance of front loads. High trail cycles do little to stabilize the front oscillations but allow the greater benefit of a convenient front load and lighter handling. Other factors such as toe clip overlap and length of nose and ear hair are much discussed but with little real benefit to knowledge or understanding of shimmy. Clearly more study is required. Read all about it in next month's issue of Randonneur-Poet Gazette
We also neglected to mention that your handlebar bag is placed slightly more forward than optimal for reduction of shimmy. The forward positioning of the bag is similar to the rearward positioning of your body. placing the bag closer to the center of the headset/headtube pivot minimizes the amplitude and leverage of the weight shimmying back and forth.
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