Archive for category Belt Drive

The Case of the Missing Bolts

Or, Don’t Try This At Home!

If you’ve checked out the Speedhound Dropout System, you probably know that the interchangeable dropouts are attached to the frame receivers with standard steel chainring bolts.  These fasteners have the benefit of a large surface area to contact the chainrings and crank spider, or in the case of the SDS, the dropouts and the receivers.  The threads on the bolts don’t come into contact with any of the mating surfaces, and the bolts do a good job of handling shear forces.

Think of a crank spider and chainring as the blades of a pair of scissors, trying to cut through the bolts.  As you jump on the pedals, your power is transmitted from the crank spider to the chainring, which pulls the chain forward.  A large, powerful rider could generate 500 pounds of pulling force at the chain, especially on a small chainring and long cranks.

Once in a while I like to do some sprints to rev up my heart and keep my legs sharp.  I’ll do hill sprints, on the bike or on foot.  Other weeks I’ll just make sure to include some focused accelerations during my rides.  During the winter, I get it done indoors on a trainer, rotating through five spinning CDs.  I aim to average 10 minutes of actual sprinting every week (not counting warm-ups and rest periods).

I rarely get on the “nowhere bike” during the summer, but last week a heat wave hit, and I was feeling short on sprints, so I went down to the cool of the basement to catch up.  I’ve got a fixed-gear Speedhound that I use on a variable-resistance fluid trainer.  It’s got a Gates Carbon Drive belt and 50X20 sprockets and it’s very smooth.

We’re finishing up the development of the production version of a slider-style dropout for the SDS (more on that in a future post).  I needed three chainring bolts for a meeting at the machine shop that’s helping us with the project.  I didn’t have time to go to Speedhound HQ, so I pulled the bolts from the Sugino RD-2 cranks on my Speedhound fixie.

The other day, a panicked thought crossed my mind – had I done my last 40 minute spinning session with only two chainring bolts in the crankset?   Yikes.  I ran down to the basement to look.  Here’s what I saw:

Missing Chain Ring Bolts

The two bolts were next to each other, leaving 288 degrees of the sprocket unsupported. But the sprocket ran true and there were no clicks or any other signs that parts were missing, other than three empty holes.  Nothing bad happened, no sprocket tacos, no noises, nothing different at all.  Why did it work?  Spot-on alignment between the front and rear sprockets, the lateral stiffness of the Gates Carbon Drive belt, the meshing of the teeth and sprockets, and the location of the sprocket centerline to the inside of the shoulders on the spider.  Oh, and the ability of those two chainring bolts to resist the shearing forces as I pedaled.  I’m back to five bolts now.  And please, don’t try this at home!

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Do You Like Messing Around with Bikes?

As a kid, I was always fascinated by how things worked.  A broken toaster was an invitation to explore:  I had to take it apart to figure out what made it pop.  Discarded TV sets, clocks, lawn mowers, electric mixers, and tape recorders were some of the subjects of my screwdriver autopsies.  With my knack for mechanical things, bikes were a breeze.  When I was 12, I assembled my new 3-speed right from the box.

Yes, I got my driver’s license when I was 16, and anything with an internal combustion engine had a certain allure.  But cars were too big, dirty and expensive to mess around with.  Now, a bike – I could store that in the kitchen or carry it into the basement.  I could clean the chain, disassemble and repack the bearings, or adjust the derailleurs just about anywhere.

My first real racing bike was a Gitane Tour de France, orange with chromed fork tips and stays and gaudy Mylar stickers.  That bike taught me what it means for a bike to be alive (especially compared to the Schwinn Varsity that I took on my first century ride).  Turns out those old European racing bikes from the 1970s were great all-around rides, which is partly why you see so many of them resurrected for duty around town today.

I was constantly experimenting with my gear, trading one bike for another, always searching for the “magic ride.”  I worked for awhile brazing frames at Trek, when all of their bikes were lugged steel, made in Wisconsin.  I made my way through school wrenching in bike shops, because I had a passion for bikes and a talent for fixing them.   I also loved to ride bikes, and working around them gave me the opportunity to try hundreds.  Later, when I could afford it, I began collecting lightweight racing bikes, many from the 1950s.

One thing I always wanted was a bike frame that could do just about anything on the road or a light trail.  A kind of universal bike.  About 10 years ago, I noticed that people started buying cyclo-cross bikes, but not for racing.  The extra clearance in the frames for muddy knobbies also made them suitable for fenders and puffy road tires.  Like the old racing bikes from the 1950s, 60s and 70s.  Although a C-X bike is a lot better than a contemporary road racing bike for the riding that 99% of us do 99% of the time, it still involves some compromises.  There must be a better way, I thought.   How might a bike frame be made to work for every rider in a variety of situations?  I decided to design a frame that could be a flexible platform for any type of drivetrain and a wide variety of riding styles.  A frame that would expand a rider’s choices now or in the future.  I thought, “What if we made it modular?”  I began experimenting and made a prototype of an interchangeable dropout system that would meet the particular demands of belt drive, but could also be used with derailleur gears.

All those years of experimenting inspired me to create Speedhound Bikes.  Our patent-pending Speedhound Dropout System is a unique departure from conventional thinking.  With this system, the ONLY ONE offers a degree of flexibility not found in any other bike frame.  Now, you no longer have to settle for one type of drivetrain or brake system.  You aren’t stuck with a track frame when you decide you want gears.  Want to go low maintenance, ditch the chain and go belt drive?  Be our guest.  You pick the drivetrain you want and build your Speedhound in any configuration you like.  Cantilever brakes or calipers?  We don’t make any decisions for you.  And if you want to repurpose your Speedhound to do something completely different, the choice is yours.  If you like tinkering with bikes, you get it.  “Go Your Own Speed” is our motto and the principle we live by.  The quest for the magic ride never ends.

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What Length of Belt Should My Bike Wear?

A lot of well-dressed bicycles are wearing belts these days.  They make a clean, crisp fashion statement on the runway, the road and the bike path.  Unlike a chain (or the belt on your pants), though, the length of a bike’s drive belt can’t be adjusted.  The length of the belt depends on the size of the front and rear sprockets, and the distance between them.

Gates Carbon Drive Belt Drive Belt Length CalculatorSo how does the well-heeled bicycle owner decide what is the right belt length for his or her bike?  Fortunately, our friends at Gates have created a handy belt length calculator.  It’s an easy to use Excel spreadsheet you can download to your computer.  You can find it here. Once you arrive at the Tech Info Page, select “Belt and Sprocket Size Calculator” under the heading “Technical Manual.”  (Skip the Carbon Drive Systems Calculator also appearing on that page – it’s not nearly as useful.)

If you are setting up a single speed, calculate which combination of front and rear sprockets will give the ratio you want.  In general, a smaller front sprocket will give better clearance with the chainstay.

For internal gear hubs, consult the manufacturer’s data on ratios.  Select a combination of front and rear sprockets so that you will have the low gear you want.

Make sure your combination of sprockets and belt length work for your bike’s chainstay length.  The calculator will give you the required range of adjustment to take up belt slack.

With the right belt length, your bike will be well-appointed and give you years of carefree riding.

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News Flash: Belts Are Now As Efficient As Chains!

The diamond-framed “safety” bicycle replaced the high-wheeled “ordinary” by the end of the 1800s.  Apart from a few shaft-driven bikes, chains have ruled since those early days.  Although belts have been used to transmit power since at least the 1870s, when flat leather belts linked steam engines to farm equipment and industrial machines, it’s taken over 100 years since then for belts to be successfully adapted to bikes.  The reason has to do with efficiency.

The human engine doesn’t develop much power, and when we jump on a bike, we want our pedaling effort to translate into maximum forward motion.  Until the development of modern cogged belts, nothing could compete with the transmission efficiency of roller chains.

Often called timing belts or synchronous belts, cogged belts are popular in applications that require precision, durability and efficiency.  Many cars use a timing belt to drive the camshafts that control the opening and closing of the engine’s valves.  In 1962, the German Glas 1004 became the first mass-produced vehicle to use a cogged timing belt in place of a chain.

CenterTrack on the OUR Blue Speedhound

CenterTrack on the OUR Blue Speedhound

Our two-wheeled friends in the motorcycle world are also fans of cogged belts.  In 1980, Harley-Davidson introduced a Gates Kevlar reinforced belt as a replacement for its chain drives.  That year, they debuted the FXB Sturgis model featuring the belt drive in honor of the iconic motorcycle rally.  Other motorcycles, including BMW and Victory, use final drive belts.  Snowmobiles are almost all driven by belt transmissions.

In about 1985, Bridgestone introduced a belt-drive folding bike for the Japanese market.  The STRiDA folding bike was designed around the same time and also uses a cogged belt drive.  But despite all this cogged belt history, high performance belt drive for bikes only became available in 1997, with the Gates Carbon Drive system.  http://www.carbondrivesystems.com

According the U.S. Department of Energy, cogged belts are about 98% efficient.  http://www1.eere.energy.gov/manufacturing/tech_deployment/pdfs/replace_vbelts_motor_systemts5.pdf This means that 2% of the input power is lost, which is about the same efficiency as a roller chain.   Kidd, Matt D.; N. E. Loch, R. L. Reuben (1998). “Bicycle Chain Efficiency”. The Engineering of Sport conference. Heriot Watt University.

Belt drives have been used for decades to drive vehicles much heavier and more powerful than Speedhounds.  Now that belt technology has finally caught up with bicycles, we think belts are a perfect choice for getting you up those hills and through the rain and snow you might encounter on your rides.

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Mary Queen of Scots Had a Speedhound!

Speedhound fans know that our mascot is an Italian Greyhound (IG) named Cooper.  His ancestors have been a popular breed for millennia.  Evidence has been found of IGs at Pompeii! Mary Queen of Scots was a big fan of the little speedsters too.

Speedhound BadgeIGs are light, quick and nimble.  They’re a perfect mascot for Speedhound bikes.  In fact, Cooper, who weighs in at only 10.4 lbs (4.7 kg), is still over twice as heavy as an ONLY ONE frame!  That’s what we call light and nimble!

Our inspiration from IGs goes beyond our need for speed, though.  IGs are agile sporting dogs – our “running dog” graphic is inspired by an IG competing in a lure coursing event.  And since we insist on making our own forks that match the frame geometry, both parts of a Speedhound frameset have matching serial numbers starting with the letters “IG” for Italian Greyhound.  You can find the serial numbers stamped in the bottom bracket and on the fork steering tube.

Speedhound Serial Number

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The JenNastix Experience

One of the most impressive things about the patent-pending Speedhound Dropout System™ is that it allows you to easily and elegantly use a belt drive.

For our second video, we recruited fixed gear enthusiast (and Banjo Brothers model) Jenn ‘JenNastix’ Gallup to put the Speedhound OnlyOne™ frameset with a Gates Carbon Drive to the test. And, oh yes she did!

Rider:
Jenn Gallup

Shot and Edited by:
Paul Moehring (www.paulmoehring.com)

Produced by:
Bicycle Theory (www.bicycletheory.com)

Wearing a Belt in the Cold

We’ve been wishing for some old-fashioned, sub-zero Minnesota winter weather lately.  The kind where your bike tires squeak on the hard-packed snow and there’s no point to carrying a water bottle, because it’ll be frozen just about the time you want a drink.  The kind where the biggest challenge is keeping your feet warm, so you ditch the clipless pedals and bike shoes and wear your roomiest boots with extra socks.  The kind where your face mask freezes stiff with your own breath and you hope you don’t get a flat, because your hands will be too cold for a roadside repair.

Speedhound with Belt Drive

Our beloved Speedhounds out for some winter fun

So why would we want that?  To test the cold weather performance of a belt drive Speedhound!  Gates says that “the technology behind the Carbon Drive belt has a published temperature range of -65 to +185.  If you’re riding somewhere colder or hotter, we’d love to hear your story.”  Well, so far in 2012, we’ve had exactly ONE sub-zero day in Minneapolis, with a low of -11F (-24C) and a windchill at a balmy -23F (-30C).  It was perfect, so I wheeled out our original Speedhound test mule, with a single speed 50X22 belt drive.  I let the bike sit outside for several hours and bundled up for a ride around town.

Belt Drive Speedhound on a winter ride

One of these Speedhounds loves the cold. The other, not so much.

So how did it go?  After a brief warmup, I jumped on the pedals at varying speeds and ground up the steepest hill in the neighborhood.  I spun as fast as I could with my stiff legs.  Underway, the belt felt – normal.  I thought I detected a slight clacking sound from the belt engaging the cogs, but maybe it was my teeth chattering.  Off the bike, I rotated the pedals backward by hand.  The drivetrain was stiffer than in warm weather, but it was difficult to say how much of the drag was from the grease in the bearings and how much was the belt.  I didn’t perceive any added resistance when riding.    With the bright sun, I could almost imagine it was a July day, except by the time I got back to Speedhound HQ, my toes felt like frozen peas.

Check out the full photo set on Flickr.

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