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!

Monday, October 1, 2012

Stop the Slapping! A budget-friendly DIY chain guide.

This summer I bought a new mountain bike.  Ok, so it wasn't really "new," in the strictest sense of the word, but I did buy it from an actual bike shop.  I just happened upon a left-over Trek Remedy demo bike with a small frame that only a vertically challenged rider could love.  With a little TLC, it was riding and shifting smoothly, eating up bumps my hardtail would have had me in tears over.  I soon realized that this all-mountain machine with 6" of front and rear suspension travel was a LOT more bike than I was used to, and that it quickly boosted my confidence in quickly descending very rugged terrain. 

As I barreled down yet another boulder-strewn old jeep trail, I noticed how the tranquil sound of rocks bouncing off my spokes was rudely interrupted by the annoying clatter of chain striking chainstay.  I began my investigation with the rear derailleur.  As I hadn't had this problem on my other bikes, I assumed the tensioning system must be askew.  Spinning on the work stand, there seemed to be adequate tension on the chain to keep it in line, so maybe I was mistaken in my previous supposition.  Maybe the problem resulted from my new-found love for rocky descents and technical terrain?  While the cockpit of this new burly all-mountain beast afforded a place of smooth security as the earth undulated underneath, the rear wheel and drivetrain experienced a much more violent interaction with terra-firma.  It would seem that my chain slap symphony was due to hurling my drivetrain mercilessly down the rugged fall line. 

Ok, source located - now, what do I do about it?  My good friend Google had quite a few wonderful solutions to my predicament, but the price tags ranged from a low end of $50 to a high end over $300!  When I added "DIY" to my search engine query, some interesting ideas began to emerge.  Riders were using all kinds of materials they had lying around the house to keep that chain where it was supposed to be as they danced with gravity down the slopes.  Some were using zip ties, others bushings and spacers, some using bolts and a few even fabricating with wood.  The one thing most of these ideas had in common was the basic premise that the shorter the unsupported length of exposed chain, the less deflection the chain will undergo when the driveline deflects rapidly (due to a bump, obstacle, etc).  As I set out to scrounge up some materials for my own version, I began to think about the various recumbent bikes/trikes that I'd owned and how most of them had extremely long chains run across long spans between supports.  Some of the bikes I'd owned were plagued with chain slap issues (my vintage RANS Stratus was one of the worst offenders), while others seemed to manage the chain effectively regardless of how rough the road became.  Many of the quieter drivetrains used chain tubes to support and guide the chain along its long (and sometimes circuitous) journey.  Could it be as simple as adapting a recumbent bike product for a diamond-frame implementation?

Idea hatched - time for parts gathering.  The core of this idea involved a chain tube.  These are typically made from PVC or Teflon tubing (1/2"?) and can be found either on recumbent bike supply websites or in the yard irrigation aisle at your local home improvement store.  I wanted a length short enough to minimize friction, but long enough to ensure a smooth chain entry/exit impervious to twisting and binding - in my case, I guessed about 2" long.  Now, one thing I learned riding recumbent bikes with chain tubes: they are not the easiest things to secure.  The up-side to this type of tubing is that it is quite low-friction.  The down-side is that this low-friction property makes it a pain to securely affix.  I've had more than my fair share of chain tubes sucked into my front derailleur when the zip tie I had securing it slowly slipped further and further down the tube's length.  I thought about using a hose clamp, but the thought of an unsightly silver clamp on this beautiful bike was more than I could bear.  As I rummaged through a parts drawer I came across a piece leftover from the installation of a rear cargo rack on one of my other bikes.  Some racks come with universal C-clamps to wrap around the seat stays and anchor the cargo rack in cases where the bike doesn't have rack mounting bosses brazed on.  These small metal clamps have most of their surface coated in an anti-slip rubber or vinyl material - perfect for our implementation. 

Once the chain tube was securely bolted in the C-clamp, the attention turned to securing the apparatus to the chainstay.  Since I'm not one of those single-speed-riding monsters I've been passed by on the trail, the chain guide had to be able to move and pivot to accommodate my triple front crankset and 10-speed rear cassette.  Enter my ever-present pals, the zip ties.  The simplest part of the project, one zip tie around the chainstay and another from that zip tie to the bolt securing the chain tube's C-clamp.  The tie around the chainstay should be secured VERY tightly so it doesn't allow the tube to "migrate" forward along with the chain and risk contacting the front derailleur.  The tie connecting the chainstay tie with the chaintube c-clamp bolt should be left as an open circle, in my case about 1" in diameter.  This allows the chain tube to pivot on the zip tie and to deflect left and right as the chain is shifted through the various gears. The optimal size of this connecting zip tie "O" will depend on the specific bike geometry and how far the chainstay is from the lower return path of the chain from crankset to rear derailleur.  Some contact with the chain tube in all but the smallest of gears (granny gear + smallest rear cassette cog) quiets the chain, but too much (i.e. tube pulled too far up toward the chainstay) creates additional friction and noise when in the large chainring and could limit lateral deflection, creating difficulty in shifting smoothly between the front three chainrings.

I will include a side note about guide positioning fore-n-aft.  Some DIY-ers reported issues with the guide deflecting sideways and contacting spokes or knobby tire treads, sometimes with not-so-great consequences.  I anchored my guide so as to bump into the smooth sidewall of the tire, should the chain & tube ever deflect sideways to that extent.  Chain slap most likely would be further minimized by moving the guide further aft toward the center of the chainstay, but I didn't want to risk that positioning for a prototype run.

Last step: threading the chain through the tube.  I was in luck as I had a removable master link in my chain - popped that open, threaded the chain through the tube and snapped it back together.  No master link?  Get out the chain tool, I guess.  Theoretically I suppose one could cut the chain tube down one side along its axis allowing it to be wrapped around the chain before attaching the C-clamp, but I'd worry that the tubing would spiral in on itself, coming out of the C-clamp and lodging itself in the rear derailleur - probably at the most inopportune time.  If I hadn't had a master link in my chain, I would probably have removed a link from my chain and put a master link in - but that's just me.

Maiden voyage: success.  A couple rides around the block and it was off to the trail.  The thing that struck me was how unnoticeable the chain tube apparatus was.  In many gear combinations I couldn't hear the chain passing through the tube at all, and in others it was just perceptible.  Going up the trail the bike performed as usual - shifting as smoothly as ever through the range of gears.  At the top, I opened the rear shock up to its full range and began the descent.  The difference was immediately evident.  I would estimate an 70-85% decrease in chain clatter, the rest of which can probably be attributed to drive-side chain slap (to which I have no solution thus far).  My descent was now (mostly) peaceful and serene again, the gentle ping of displaced stones rocketing off the tensioned spokes (and occasionally the aluminum frame) and the chain silently and dutifully propelling the bike downward.

A final note on durability.  In any system - especially one of inherent contact and friction between two surfaces (chain and chain tube) one would expect one or both components to exhibit wear.  The soft plastic of the chain tube will need periodic inspecting and eventual replacement.  The time between tube replacements (at a cost of about $0.05 if you bought the 20' irrigation tubing roll!) can be extended (probably up to 400%) by periodically loosening the C-clamp and rotating the chain tube 90 degrees.  Simple, basic, cheap and effective.  Probably one of my favorite "little" projects yet.

Happy riding!

*** Disclaimer: Once again, if you use this idea or a part of it in a project of your own, you do so at your own risk!  If your chain tube breaks loose, jams in your rear wheel causing you to fly off a cliff, don't blame me - I've lost plenty of perfectly good bike components (and skin) to hairbrained ideas such as these.