Technology in wheel time

DN Staff

August 2, 1999

29 Min Read
Technology in wheel time

Innovative design solutions require custom materials and components, right? Not always. Engineers can often save money and design time by sticking with what's already available. That's especially important when designing products that are price-sensitive, like recreational equipment for the common folk. Design News editors tried out some new sports and recreation equipment to find out how off-the-shelf materials enabled design innovation. Bruised but unbowed, they lived to tell their tales.

Patented mechanism packs convenience into folding bike

By Paul E. Teague, Chief Editor

Pedaling up the rock-and-branch-strewn mountain was hard, chest-heaving, leg-screaming work, especially on those stretches where the incline was greater than 60 degrees . But, the exhilaration of the fast ride down the other side, with its quick turns and deft maneuvers around trees and boulders, made the experience well worth the effort, and gave the new Montague X-Series mountain bike a worthy workout.

Ah, the thrill of rugged mountain biking! It's good for your heart, good for your soul, it restores the vitality that the daily work grind robs from your spirit. It it oh, how would I know what it does?

The truth is, that mountain was just a relatively small hill. Sure, my chest was heaving and legs screaming, but that's what happens when you haven't ridden for awhile. And the exhilarating ride down? My most deft maneuver was getting up somewhat gracefully after falling down twice on the simplest turns.

The Montague X-Series Mountain Bike incorporates folding technology that increases the convenience while leaving performance and torsional rigidity unaffected

But, hey, none of that was the bike's fault. It's a sturdy, responsive, high-performance machine that can take all the punishment the average weekend cyclist like me can give it. And it gives something back convenience.

The convenience is in its transportability. Normally, when I take my bike anywhere, I have to wrestle it onto a trunk or roof rack. With the Montague X bike, I just folded the bike and threw it into the back seat of my Taurus.

Now, folding bikes have been around for a long time, but this one is truly different. Traditional designs require several folding steps and place the folding axis in the middle of structural members, resulting in a bike that's complicated and structurally weak.

The Montague X-Series' patented design moves the folding axis back to the seat tube. It's actually a tube within a tube, and that's the primary design innovation. The tubes can be either steel, aluminum, or both. Graphite-impregnated nylon bushings prevent metal-to-metal contact, thereby avoiding corrosion and other problems from the joining of dissimilar metals. The concentric tubes eliminate the need to cut or hinge any structural tube that would affect torsional rigidity.

To fold the bike, you simply remove the front wheel by activating a common quick-release lever, loosen another quick release on the front oval "boom'' tube, push down on its locking mechanism, then, using the concentric tubes, swing, or fold, the front of the bike around so it folds into the rear triangular frame. Less than a minute's worth of work. No tools required.

Geometry was among the design considerations. The X-Series frame is actually two frames, front and rear. Two counter-tightened nuts join the two frames concentrically at the seat tube. One design challenge was to maintain conventional locations of the rider contact points (the seat, pedals, and handlebar) for different-sized riders while using only one size of rear frame combined with various sizes of front frames. Engineers accomplished that by using AutoCAD software and manual design to manipulate the angles and lengths of the "boom" tube.

The single-size rear frame enables use of a single production jig, which saves on up-front tooling costs. Using off-the-shelf aluminum keeps the weight and cost of the bike down.

Montague designs and manufactures these and other folding bikes for the U.S. military, and for automaker BMW in Germany.

Other potential applications for the folding technology: Truss members for bridges, to ease transport of the members to a construction site.

Key to the design of the newest hot wheels: trail and error

By Paula Porter, Internet Editor

I was the first "kid" on my block with inline skates back in the late '80s. It was love at first whirl.

But my Rollerblade Macroblade skates haven't been used much lately. I just can't deal with the packed trails. So, instead I spend my free time hiking the rough trails at state parks.

Imagine my delight when asked to try the latest innovation from Rollerblade, the Coyote(TM) all-terrain skates.

Band brake assures steady stops even on the steepest slopes.

So what's different with the Coyote? Well, this purported "sports utility vehicle" has three 6-inch pneumatic tires.

Oh, I admit being a bit skeptical about being able to roll across a dirt path. But with my cross country ski poles in hand, and safety gear on, I found cross country inline skating to be a good cardiovascular workout, as well as relaxing away from the crowded trails. The skates worked best on hard-packed dirt trails and one definitely needs the poles to "assist" with hills.

According to Lloyd Keleny, concept engineer manager at Rollerblade and one of the developers of the Coyote, this monster skate took three years to design and is the beginning of a new world of inline skates.

The wheels are a big factor in the design. "Big tires are a given for going off road," Keleny continues. "To go over roots and rocks, the larger the tire, the better the ride. Other skate designs have gone with big tires fore and aft of the boot, but we went with wheels under the skate to provide maneuverability and that true skating experience."

One of the rejected designs, this version featured internally adjustable damping, internal floating piston, and gas-pressurized rebuildable and adjustable spring preload. But it lacked maneuverability and stability, according to testers.

Designers tried a variety of wheel sizes from eight inches on down, as well as pneumatic tires, different types of urethane, and a wheel that was a solid air-filled tire, which is used on the Outback(TM) skate.

"That wheel being harder had a faster roll while the air gave it a more pneumatic feel," Keleny explains. "But in the end, we couldn't beat the feel of a pneumatic tire. And with these tires, we didn't need any extra suspension on the frame."

The frame is made of Duralite(TM), a lightweight aluminum that provides support without being too bulky.

The design team originally focused on a frame that's called a low-rider, a plate that extends beyond the toe and heel with a wheel at each end, much like a short ski with two wheels. "We found a skate of this design was hard to maneuver. While the skate offered more stability over rough terrain, it had no ground clearance and bottomed out," Keleny says.

Coyote also features Rollerblade's ABTXtreme(TM) adjustable cuff-activated braking system. I found this the best feature. I could slow down easily and steadily without fear of losing control.

"By incorporating a band brake between the two back wheels we got the added advantage of more stopping power with static friction."

The skate boot is a molded polyurethane from Bayer that, says Keleny, offers flexibility but is extremely abrasion and tear resistant. In addition, the boot features what I originally thought was a bit of overkill a four-part fastening system. The skate has laces, a Velcro belt over the ankles, a powerlock buckling system, and a top Velcro belt.

Check out the listings at Rollerblade's website, and see where you can try out the new skates.

Website Exclusive...

Skating sites

Skate manufacturers Alpina Sports Bauer Chicago Skates Convertible Skates Dalbello Dalbello Sports USA Great Group Harlick Hypno InLiners Inter Sonic K2 Skates Lotuskate North America Nike Oxygen ProMotion Skates Roces Roll Skater Rollerball Rollerblade Rollerblade Europe Rossignol Roxa Salomon Sports Seneca Sports Shockz Skater Starway StreetSki Swheels Sports Tecnica UltraWheels V-Line Variflex Aero Wheels The Wheel Hog Inline Wheel Zephyr Inline Skate Tours Hudson Bay Inline Kryptonics

Skating glossary

ABEC - Annular Bearing Engineer Council rates bearings. ABEC-1, ABEC-3, ABEC-5 are indications that the bearings meet specifications of a certain precision level with ABEC-5 being the best.

Aggressive skates - Made for grinding, rail sliding, ramp/vert use, these skates are built tougher than recreational/fitness skates. Front wheel doesn't stick out as far and there is a gap between the 2nd and 3rd wheel for grinding.

Anti-rocker - A wheel configuration with the larger wheels on the toe and heel and smaller wheels in the middle to allow for easier sliding on rails (as in handrails).

Armor - Protective pads and helmet

Bearings - Inline skate use the standard 608 bearings with the inner being 6mm and the outer ring being 8 mm. Each wheel has a set of 2 bearings.

Bearing spacers - These go between the bearings, and are either plastic or metal. Some spaces are threaded so that the axles screw on to the spacers themselves.

Braking - Different brands offer different types, including the Active Braking System of Rollerblades, the Power Brake System of Oxygen skates, Bauer's Force Multiplers and Roces Tartaruga. Some are pads on the rear of the skate, some are cylindrical brakes oriented to roll the same direction of the wheels, some are a disc-braking system. Currently, there is no industry standard and some brakes have to be replaced often.

Bunny - A new skater who needs to grab onto stuff to stay upright.

Closure system - It's important for the skates to fit properly. Skates use buckles, velcro closures, laces or a combination. Buckles can't be tightened as much as laces or velcro. Buckles can be ratchet-style with notches in the pull-through strap, while some are ski-boot style with a metal T-bar that hooks into round notches on the shell.

Diameter - Most production skates come with 72 or 76 mm wheels, with other sizes available. The shorter the wheel, the more stable and maneuverable the skate, although it will be slower. Taller wheels let you go faster, but are less maneuverable. Not all skates can take the larger wheel, depending on the chassis and runner design.

Duckwalk - Skating on the toe wheel of one skate and the heel of the other.

Durometer - A rating for the hardness of polyurethane the primary material for wheels. Wheels generally have a rating of 78A or 85A with the higher number indicating a harder wheel. Softer wheels absorb rough roads better. Some skaters mix their wheels to have the better shock absorption of softer wheels and the durability of the harder wheels.

Flat rocker - A wheel setup where all four wheels touch the ground. Outside wheels are generally larger than the inside wheels, but the middle two wheels are rockered down so all touch. Lends more stability to the skates, but response suffers.

Frame - The part of the skate that holds the wheels and where the boot rests. Generally made of plastic, some are metal or aluminum.

Frame spacers - Parts on your skates that go between your wheels and runners. Most skates have oval-shaped frame spaces so that skaters can flip them 180 degrees to rocker the skates.

Grind plates - Flat metal or hard plastic plates bolted to the runners for sliding or grinding along rails. These protect the runners from being shredded.

Hockey skates - Usually made of stitched leather or nylon much like ice hockey boots. There are generally production models and components where the skater puts a boot from one company and adds a frame from another.

Hop-up kit - Upgrade kits that include frame spacers, bearing spacers and axles made of a metal such as aluminum or brass. Some incorporate threaded spaces. The kits allow skaters to put more pressure on the wheels without compressing and cracking the plastic spacers.

Liners - These are foam rubber inserts most often found in the molded plastic skates. Liners are not necessary for speed boots.

Monocoque - A skate including the boot and runners that is manufactured as on solid piece which allows for more skate stiffness.

Multipurpose skates - These are labeled cross-training, fitness or recreational skates. Usually made of plastic boots with foam liner and buckles, laces or a combination of both. Plates are usually plastic to keep them lighter.

Rockering - Arranging the wheel heights on the skates to allow the wheels to curve much like an ice skate blade. Done by raising the front and rear wheels, lowering the center wheels or doing both. Some stability is lost, but the skates become more responsive.

Shell - This is the boot. Some have vents, some don't. Vents make the skates lighter, but lose in strength and durability.

Speed skates - Typically made of leather with short boots that do not go over the ankle. The skate come with a longer frame to accommodate five wheels. These usually come as component skates only and are not an off-the-shelf item. The frames are usually aluminum alloy or fiberglass/carbon. The extra length in the wheelbase makes the skates more stable a higher speeds, but less maneueverable.

Wheel rotation - Much like rotating the wheels on your car, skaters flip or rotate their wheels that wear down faster.

Safety on wheels

Before doing anything, check the skates out.Wiggle the wheels for axle tightness and to see that the nuts are secure.

  • Inspect the braking system.

  • Roll the wheels to make sure the bearings aren't binding.

  • And don't go out without protective gear -- wear a helmet, wrist guards and knee pads, elbow pads. Wrist guards come in two forms as a half glove with plastic bars below and above the hand, the other is a glove with the fingers removed.

  • Wear long sleeves and long pants to keep from getting road burn when you do fall down.

  • The right socks are important to keep from getting blisters. Socks over the ankle bone provide more protection. Polypropylene sock liners under socks help prevent blisters.

Timeline for skates

Sometime in the 1700s in Holland - an unknown Dutchman nailed wooden spools to strips of wood and attached them to his shoes so he could ice skate in the summer.

1760 - Joseph Merlin attached metal wheels to boots and showed them off while playing the violin. Unfortunately, he couldn't stop and crashed into a wall-length mirror.

1819 - First patent for a roller skate issued to Monsieur Petibledin made of a wood sole and fitted with two, three or four roller made of copper, wood or ivory arranged in a single line.

1823 - Robert John Tyers of London patents the Rolito skate with five wheels in a single row. These skates were impossible to follow a curved path.

1840 - Barmaids in Germany works skates to serve beer faster.

1863 - James Plimpton of Massachusetts put two parallel sets of wheels, one under the ball of the foot and one under the heel on a boot. The wheels were made of boxwood and had rubber springs to allow the user to skate in a circle.

1884 - Invention of pin ball bearing wheels lightened up skates.

1902 - The first public skating rink opened in Chicago with more than 7,000 in attendance on opening night.

1960s - Plastic wheels and polyurethane floors were introduced, replacing wooden wheels and maple floors.

Later 1970s-1980s - Disco and skating hit the movies. Skateboards were reborn. Also introduced were sneaker skates and wider wheels taken from skateboards for skating outdoors.

1979 - Scott and Brennan Olson from Minneapolis found an antique pair of roller skates with inline wheels. They put some polyurethane wheels on their hockey boots so they could play their favorite sport all year 'round.

1983 - Rollerblade, Inc. was founded by Scott Olson and the first inline skates hit the market.

1999 - There are now more than 30 companies manufacturing several hundred styles of inline skates.

All-terrain board materials and practical design keep costs down

By John Lewis, Northeast Technical Editor

Summer snowboards, and some aren't. The Mongoose UniCamb 117 All-Terrain board (ATB) isn't exactly a snowboard. But it's the closest thing to it without the snow. The board, from Hyline All-Terrain Board Co. (Anaheim, CA) simulates snowboarding on grassy slopes, dirt trails, or asphalt streets.

Sitting on the pavement, the board resembles a snowboard with a pair of 8-inch diameter pneumatic tires hanging off each end. It's 117 cm from tire tip to tire tip, and weighs 17 lb. Two-ply rubber tires grip the riding surface. Injection molded tri-spoke, nylon glass hubs roll over precision bearings that mount to 4130 chromoly-steel axles.

UniCamb 117 ATB simulates snowboarding without the snow.

The cambered deck articulates to almost 45 degrees (thanks to a channel-truck system that uses opposing stainless steel compression springs on either side of a central pivot. Riders can customize board stability, ride, and handling by inserting urethane elastomer, spring damper inserts into the rear, front, or all four compression springs.

Other Hyline board designs mount the trucks to a chromoly-steel sub frame. Brackets support the deck. "These boards last longer, and can take more abuse than the UniCamb design," says Hyline President Evan Lipstein. All decks are 14-mm thick, 9-ply Canadian maple, with grip-tape on top and a slick, ABS plastic bottom for rail slides.

In a rail slide, Lipstein explains, the rider jumps the board onto a curb or handrail and slides with his feet on opposite sides of the rail. Low-profile, T-nut binding mounts also make for better rail slides. Rubber coated, stainless steel binding posts hold the Nylon-strap bindings in place. Easy-in, easy-out bindings use Velcro for closure and adjustment.

Before mounting the board, I watched the instructional video intently. She makes it look so easy, I thought to myself, as I watched the young girl on the video safely skid to a stop. I imagined my attempt at a controlled-skid stop would start with a shudder, followed by a lurch or two, a slip, then a stagger, and finally a fall. So I paid up my life insurance, donned a pair of leather work gloves, a helmet, elbow and kneepads, and, literally, hit the street.

I may be goofy, but I'm not "goofy" footed. So I planted my left foot on the front end of the board, intending to push off with my right. Unlike a skateboard, the large wheels extend beyond the ends and outside edges of the board. So keeping my push foot wider than the wheels, I pushed off and rolled slowly down the street.

After a few hours, covered with bumps, bruises, and road rash, I had mastered basic heel and toe side turns, and managed a controlled-skid stop. Flexing under my weight, the board's articulating trucks feel loose. Light toe or heel pressure rocks the board back and forth. I glide quietly along the street, carving turns from curb to curb. The pain was fading away, so I took it off road where the large tires cushioned the ride down a gradual grassy incline.

By this time, I was really enjoying myself. Then I noticed the crowd of neighborhood skateboard punks, the ones I usually chase away, had gathered around. This board has serious sex appeal. Reluctantly, I let a couple of them try the board. "It's addictive,'' they agreed.

Hyline makes several ATB models. The UniCamb 117 freestyle board retails for $230. The Giant Slalom 152, Hyline's largest and most expensive board retails for $299. While these prices aren't exactly cheap, they are when compared to other all-terrain board products. "What really differentiates us from other companies making all-terrain boards, is that we maintain performance, while trying to keep the prices within the reach of kids," says Lipstein.

Buzz all-aluminum electric scooter has some real pickup

By Karen Auguston Field, Managing Editor

Let me preface things here by saying that I live in Cambridge, MA, where we have a commissioner whose job is to protect the rights of trees. So any alternative to the internal combustion engine is met with welcome arms in this town.

While that wasn't exactly the reaction I got test-driving the new Buzz electric scooter from Huffy, I did raise a few eyebrows as I zipped past the local police station. That might have been because I failed to check out the local requirements to find out if this type of vehicle is street legal here. On the other hand, as the first-ever, sit-down electric scooter, it's bound to turn some heads no matter where you ride it.

It's also the first folding scooter, and in fact, portability was the driving force behind the entire design says John Fowler, an engineer and director of product management for the Buzz scooter. "Two key design goals were that the scooter had to fit into the trunk of a compact car and weigh less than 50 lb, including the battery," he says.

Huffy's Buzz Scooter folds to a footprint of just 39 x 10 inches, compact enough to fit in trunk of a compact car

In fact, at 20 lb, the battery weighs nearly as much as the vehicle. Cost constraints ruled out more advanced technologies than the conventional lead-acid battery designers opted for. But what they sacrificed in range (average distance between charge is about 13 miles), engineers more than made up for in cost savings. "We didn't want the battery costing more than the scooter," jokes Fowler.

The frame itself is made of aluminum. And while not as exotic as other lightweight materials such as titanium or magnesium, it's on the order of five to six times as expensive as steel on a per-pound basis. Fowler explains that due to the complex geometry of the latch mechanism that allows the steer tube to fold flat, aluminum extrusions were actually cost-competitive. "The main mechanism is a U-shape with varying wall thicknesses. Extruding this shape in aluminum is quick, easy, relatively cheap, and amenable to low production volumes," he says.

In designing the scooter's running board, engineers were able to take advantage of the fact that stiffness is a function of aluminum's mechanical properties and part geometry. Using hollow aluminum extrusions, they were able to match the stiffness of steel using less weight.

Because of size constraints, the wheelbase could be made no longer than 34 inches. Design engineers compensated for this shortcoming by lowering the vehicle's center of gravity ground clearance is a mere 3 inches. As a consequence, the scooter has good stability, but riding is limited to hard, dry, flat, relatively smooth surfaces. Potholes, I learned, are not a good thing.

Powered by a 24V dc, 0.39-hp motor, the scooter reaches a maximum speed of 14 mph in about 50 yards, and it really feels like it has some pep to it. So much so, in fact, that engineers designed in a delay time before the throttle can be activated to compensate for the high torque output (21.28 kg-cm at 4,500 rpm).

Overall, the scooter responded well as I put it through its paces. The only difficulty I ran into was practicing tight turns in a parking lot. But as Fowler politely pointed out, with a turning radius that is effectively zero, the only limitation here in practical terms is the rider's own ability.

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