Friday, October 5, 2012

Park the Gas Guzzler - Scooter Mounted Bike Rack

I admit it - I drive an SUV - a big one.  As painful as it is at the pump these days, its utility necessitates its presence in my garage.  I love the cavernous amount of space inside the rear liftgate, large items being easily enveloped within its weather-proof lockable walls.  A few months ago I even bolted a bike fork mounting block to the floor of the cargo area making trips with the bike a breeze. 

On the eco side of my garage resides my 125cc scooter.  70mpg with a 55mph top speed make the shorter trips a bit less taxing on the wallet.  The far wall of my garage is reserved for green transportation options - yep, the bike wall.  I'm a big bike commuting proponent and would love it if more of my trips could be made that way, and in a perfect world more of them probably would.  But, as a realist, I'll acknowledge that sometimes there's not enough time, too much distance to cover, or it's just too dangerous out in the AZ desert heat to make some of the trips under pedal power - that's why I love my scooter.  Those mid-range non-highway trips are a quick and easy, more fun, and definitely more cost effective on the scooter than rockin' the 15mpg SUV to go pick up a DVD. 

As the fuel costs continued to rise I tried to find more ways to leverage the scooter for my regular trips around the area.  One hurdle always needing acknowledgement was what to do when you couldn't just bungee the stuff you needed to carry to the cargo rack.  A couple of my weekly trips included this conundrum - namely my group road and mountain bike rides.  At 14 miles each way to the ride meeting point, my SUV was costing me over $6 per ride, and as I ride with that group 2-3 times per week the dollars were starting to add up.  How could I make this commute more efficient?  Now, you hardcore types will probably say something like "just ride your bike there!", etc.  That might work for some of the road bike rides (given enough time), but 28 miles of pavement on a mountain bike just hurts my head (and legs) to think about.  Enter the scooter.

I don't know how many hours I spent staring at that scooter, holding bikes up to it at various angles and in various ways, but it took a long time before an idea started to emerge.  I determined that there just wasn't enough space on the scooter itself to mount the bike on the side near the back.  Bikes are too tall and long, interfering with seating position and access to controls on the scooter in that configuration.  That left the only option as the back cargo rack.  Since the route to the bike rides followed quieter back roads and the scooter didn't go THAT much faster than a fast downhill run on my road bike, I thought "why not just tow it?" - and soon after Scooter Bike Rack 1.0 was born. 

A fork mounting block was bolted to the scooter's rear cargo rack, the road bike's fork was secured (rear wheel rolling along behind) and I was off.  It really rode quite well back there - especially once I mounted the fork block so it could pivot vertically allowing for undulation in the road surface so as not to scuff up the bike's fork dropouts.  But, as I was zipping my way at a little over 50mph I began to do some math - focusing primarily on the fact that I had as much invested in my bike's wheelset as I had paid for the scooter and wearing that wheelset out prematurely to save on fuel costs was definitely NOT cost effective.  Return to drawing board.

Alright, so if we need the wheels off the ground, let's just use one of my Yakima roof-top racks mounted to the scooter's cargo rack!  Begin Scooter Bike Rack 2.0.  Yakima has specific guidelines on how close the front and rear rooftop crossbars can be together before you find yourself pushing structural integrity boundaries on their components.  I figured there must be some over-engineering built into the racks, so I managed to mount some crossbar towers to the cargo rack, cut down a crossbar to fit so as not to look crazily wide, mounted the front of my fork-mount tray-style to the crossbar and attached the wheel tray directly to the furthest aft point on my cargo rack.  It looked beautiful. 
I proceeded to mount my 30lb. mountain bike to assess the functionality and noticed a bit more flex in the hugely cantilevered wheel tray than I'd hoped.  Not to be deterred, I took apart a second rack, commandeering its wheel tray which I bolted underneath the wheel tray of the first rack - effectively doubling its strength.  Mounting the bike once more, I was a bit more confident of its adequacy in carrying the heavily leveraged weight.  It's maiden voyage did a bit to reverse my confidence as I watched the shadow of the bike/rack flex to an unnerving extent with every road imperfection I encountered.  After safely traversing the roadways home from the group ride, I removed the mountain bike and replaced it with my 20lb. road bike.  As expected, much less flex.  While challenges still needed to be overcome to transport the mountain bike, at least I could zip cost-effectively to the group road rides... or so I thought. 

Half a dozen trips across town with the bike found me zipping along my regular return route a mile or so from home when I hit a particularly rough patch of pavement.  Snap.  Scraaaaaape.   Sparks.  Not good.  Pulling quickly to the shoulder, I realized a stress point in the rack system had been overlooked in my construction.  The point at which the wheeltray bolted to the fork mounting block had experienced such stress from the cantilevered arrangement that the area around the bolt hole snapped, allowing the wheel tray to pivot freely on its one remaining attachment point, rotating downward until it contacted the pavement below.  Thankfully a minor scuff or two were all the bike suffered for the ordeal and I managed to limp the rig along the last mile home using version 1.0's "towing" style.  Drawing board anyone?

Hmmmm, apparently too much cantilever effect.  So, can't hang the bike fully off the cargo rack and can't tow it because of speed/heat/friction issues.  What if we create a 1-wheeled "trailer" that would support most of the bike's weight?  Scooter Bike Rack 3.0?  When my son was smaller he rode on one of the tag-along or trail-a-bike systems.  Due to my variety of interestingly-shaped bikes/trikes, I had opted to purchase a Burley Piccolo system that attached to a rear cargo rack rather than the traditional seat post attachment point.  This seemed like a good starting point for the design as the tag-along-to-cargo rack attachment was quite secure and it had a built-in two-way pivot allowing the trailing wheel to follow its own arc around a corner or pivot upward if encountering road undulation (plus, it was laying around my garage collecting dust).  I cut one of the tag-along bike cargo racks down to just the attachment interface which I then U-bolted to my scooter's cargo rack allowing the tag-along to be attached or removed quickly without tools. 

The next issue was in mounting a bike rack to this tag-along trailer.  There just wasn't enough length to the trailer to effectively mount a bike, so I made the trailer a bit longer.  Xtracycle makes a longtail cargo bike conversion kit that will turn most any traditional diamond-frame bike into a cargo bike.  I had purchased one of these to use on a TerraTrike Rover (see my earlier post for the details) and it was currently sitting on a shelf, just waiting for a new application.  With a bit of finagling, I managed to attach the kit to the tag-along frame, moving the 20" rear wheel back and extending the trailer by over a foot.  I clamped on a fork mounting block (as low as I could find a mounting spot) and popped the mountain bike on to inspect the finished product.  As I'd hoped, there was very little weight resting on the scooter's cargo rack and the primary forces would be primarily torsional, keeping the trailer upright and in line.  A ride around the block convinced me of the proof of the concept and the next morning I headed for yet another group ride via scooter.

Anyone who has ridden with a child using a tag-along knows that they can exhibit an amazing amount of leverage on the bike making it very important to maintain a tight grip on the handlebars keeping the bike upright and going straight.  You also very seldom exceed 15mph... for a reason.  The trailer did fine at 20mph, and even about 30mph.  When I hit 35+, the trailer began to sway back and forth and begin a resonant wobble from the leverage the high-mounted mountain bike was exerting on the long attachment arm of the tag-along trailer.  After a very slow (and slightly harrowing) drive to the group ride and back, I retired the trailer from its bike carrying days, regaling it to the duty of low-center-of-gravity cargo carrying for nearby scooter trips (e.g. grocery runs).  I'm really starting to dislike this project's drawing board, but back we go.

With the stresses on the bike carrying system I'd encountered, I began thinking I'd need to purchase a small motorcycle cargo trailer or the like in order to safely transport my pedal-powered friends.  Most of these solutions were heavy and/or expensive and weren't easily constructed with materials lying around my garage.  Flipping sadly through a mountain biking magazine, my jaw dropped when I opened to an article reviewing a motorcycle-mounted bike rack!  Amazingly enough it looked suspiciously similar to Scooter Bike Rack 2.0 (though obviously much more solidly built).  2x2cycles ( produces a beautifully designed bike rack for the cargo area of motorcycles, cantilevering the bicycle off the back of the motorcycle.  As I poured over the photos of this design I realized they had incorporated on extremely important thing I had not (beside proper engineering and design) - a load distributing strap countering the effects of the cantilevered mounting position and relieving much of the strain on the arm supporting the bulk of the bike and transferring it to the front fork. 

Armed with this revelation, I set out to rebuild Scooter Bike Rack 2.0 - better... stronger... faster... ok, maybe not faster (am I dating myself with Six Million Dollar Man references?), but definitely more robust.  I reused the double wheeltray, but attached the trays to the fork mounting block with a larger bolt/washer combination that would add some strength to the system.  The rest of the mounting system was similar to version 2.0's.  Since building version 2.0 I had acquired a new mountain bike with a front through-axle design.  This required an adapter be added to the fork mounting block.  This adapter also had the added benefit of moving the mounting point for the fork forward a few precious inches.  A couple of additional cantilevered inches were saved by rotating the front fork 180 degrees allowing the wheel mounting point offset to face rearward, in essence shortening the wheelbase.  Then, for the finishing touch, a trusty old ratchet strap was passed over the bike's frame just behind the headset and anchored near the base of the front of the scooter's seat.  The strap was snugged up, each click of the ratcheting mechanism bringing the bike's weight forward onto the fork and lifting away the stress on the wheeltray.  Scooter Bike Rack 4.0 was finished.  Time to hit the road.

As I rolled out with fear and trepidation recalling the last disastrous voyage of this rack configuration.  Eyes darting back and forth between the road in front of me and the shadow cast by the morning sun allowing me to see the movement of the system behind me, I watched as the load distribution strap did its work minimizing the flex of the rack and its wheeltray as I rolled over road imperfections and undulations.  Working my way up to top speed, the rack performed flawlessly - the bike unmoving behind me as I zipped down the road.  I ride with a much greater level of confidence these days, knowing that 4 versions and many hours have (thus far) finally paid off - though I still watch my shadow out of the corner of my eye...  Back to the drawing board again, this time only to smash it to pieces - project complete... done... success.  Next!

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