SRAM


SRAM Corporation is a bicycle component manufacturer founded in 1987 in Chicago, Illinois, USA. The name is almost an acronym based on the founders names: Scott, Ray, and Sam. Starting with the invention of a twist-grip shifter for derailleur-equipped bikes, they went on to build more components, and then to acquire other bicycle component companies, including vid, RockShox, Truvativ, Quarq, Sachs, and Zipp.

SRAM is a major supporter of bicycle racing events.

Among their many products are multi-speed internally-geared hubs via their acquisition of Sachs. SRAM has announced in 2017 that they’ll be discontinuing their internally-geared hubs due to competition from conventional derailleur-equipped and electric bicycles.

Their first product was a twist-grip shifter.

SRAM has managed remarkable growth since 1988 by acquiring other bicycle component manufacturing companies including Avid, Fichtel & Sachs, QUARQ, RockShox, Sachs-Huret, Truvativ, and Zipp.

They have donated more than $10 million to improving bike paths and lanes throughout the world.

Pawl


Have you wondered what is that tick-tick-tick you hear when a bicycle is coasting?


Photo by Keithonearth

A pawl is a small flipper device that engages a ratcheted surface so rotary movement is possible in one direction only. Freewheels typically have two pawls. Most pawls are spring-loaded, but they can also be centrifugally actuated. The images above and below are Sturmey-Archer 3-speed hubs containing pawls. The picture above is spring-loaded. The pictures below are from an older style hub that are centrifugally loaded.



Below are pictures of a Shimano freehub, also known as cassette hub. These are very common freewheeling systems found on most derailleur equipped bicycles. These contain a ratchet pawls within the hub.


The Difference Between a Screw and a Bolt

Whether a fastener is a screw or a bolt is not determined by its head. Some people think that anything you turn with a screwdriver is a screw, and anything you turn with a wrench is a bolt. Not true. A bolt fastens into something that’s threaded, such as a nut, or a pre-threaded component. A screw makes its own threads, such as into sheet metal or wood. Whether a fastener is a screw or a bolt is not determined by its head.

bolt

Metric and Inch

Two sizing systems are in common use among bicycles: Metric and Inch. Metric sizes are more common, with inch being found mostly on American-made bikes. However, there are some legacy sizes that have remained in modern bikes, especially those manufactured in Asia: Some of the larger threaded components are still measured in inches, such as bottom bracket and fork steering tube threading, and pedal threads. The metric system is based on millimeters. There are exactly 25.4 millimeters in an inch. Ten millimeters is also known as a centimeter, and a hundred centimeters is a meter. To take that to the extreme, 1000 meters is a kilometer, which is around six-tenths of a mile. For those of you in countries outside the USA, an inch is 25.4 millimeters. There are 12 inches in a foot, and 3 feet in a yard. 1760 yards make a mile, which is approximately 1.6 kilometers.

Getting back to nuts and bolts, inch-based sizing is controlled by the Society of Automotive Engineers, and sometimes inch-based sizing is referred to as “SAE.” That organization sets the standards for machine parts, such as thread per inch on nuts and bolts, head sizes, and thread pitch angle (60 degrees).

Metric nuts and bolts also use 60 degree angles, except for the Italian standard, which is 55 degrees.

55 degrees was also used in an old British standard called “Whitworth” or “British Standard Five,” also known as “BSW” and “BS5.” Most Whitworth wrench sizes are not interchangeable with SAE. In Whitworth, nuts and bolt heads are 5/3 of the major diameter of the bolt. You’ll only find Whitworth nuts and bolts on old bicycles made in the United Kingdom.

See also: Standards

How To Ride a Penny-Farthing


Ordinary racer, bicycle, penny-farthing
via Agnieszka Kwiecień, license: CC-BY 3.0

The fellow riding the replica in the picture is making it look easy, but these were far from easy to master.

First, there was the matter of getting started. If you look carefully at the picture, a few inches above the rear wheel fork, on the far side, is a little footpeg. The rider would run with the bicycle to gain some momentum, then place a foot on the peg while holding the handlebar. The rider could stand on the peg and coast along, but most of the time, the rider would complete the mounting process by essentially jumping up into the saddle, then letting the feet find, or catch up with the pedals. This had to be done quickly, before the bike lost much momentum. Without enough momentum, the bike would start pitching wildly to one side or another. You can imagine a modern bicycle at a very slow speed. When you get down to around walking speed, it is very hard to steer a straight line. But with the tall, heavy bike, it really becomes an exercise in careening if you are way up there, with your head nine feet (275 cm) off the ground. Furthermore, if you turn more than just a few degrees, that big old wheel starts rubbing on your thigh. Anything beyond that, and you simply have to fall off.

So finally, there you are mounted on your ordinary, and you come to hill. You’d better pedal really hard, because you can’t gear down. Worse, when going downhill with the first ordinaries, the techniques for slowing down were all harrowing.

The first option would be to resist the pedals. But, you’re geared up, and have not only your weight to resist, but the 60 pounds (27 kg) of the bike as well. If that is not sufficient, you can rub the palm of your gloved hand on the top of the solid rubber tire – until your hand gets too hot. Some of the later ordinaries came equipped with a spoon brake. That’s a metal bar that could be operated from a hand lever that would rub on the top of the tire.

If you have to make an emergency stop, there’s only one ‘safe’ option: Jump backward off the seat, landing with one foot crosswise on the top of the back tire. This jams your foot against the fork, and skids the rear wheel. It costs rubber – and those tires wore out fast, but it could save your life. Otherwise, if something comes up where you stop quickly, such as hitting a pothole, you pitch forward. Not only will you find yourself flying forward, but the bike will very likely be caught up with you.

Tires for the ordinaries – and all sorts of other contraptions such as children’s wagons and baby strollers were sold in bulk rolls called “cab tiring.” You’d pick a width, and buy perhaps 50 feet of tire. It was a fat-walled rubber tube with a hollow middle. The rubber was quite basic by today’s standards. It had carbon mixed in, so that it wouldn’t wear out in the first mile or so. That’s why tires were always black. You’d cut off a length of cab tiring just the right length to go around your wheel. You’d insert a solid steel wire all the way through the tire. Where the tire material joins, you grab the ends of the cable and twist them together. Finally, you cut off the extra length of twisted wire, so the seam in your tire doesn’t have metal sticking out.

Some of the earliest ordinaries didn’t bother with rubber at all. They had wooden wheels, iron wheels, and sometimes wooden wheels surrounded with an iron tire. These were the true ‘boneshakers.’

See also: Odd Fact About Replica Penny-Farthings.

See also: The Safeties.

Health


“One of the key studies of cycling has found that people who cycle to work experienced a 39% lower rate of all-cause mortality compared to those who did not even after adjustment for other risk factors, including leisure time physical activity.” – CyclingEngland

According to at least one statistical study, the health benefits of cycling outweigh the risks by twenty to one.

Allen Wrench


Typical Allen wrench


Allen bolts, and the wrenches to turn them are quite common in bicycle technology. They have the advantages of being lightweight, and secure. The wrenches get a good grip and seldom slip. Allen wrenches are made in metric and SAE (Society of Automotive Engineers – “inch”) sizes. The most common sizes used on bicycles are 4, 5, 6 and 8mm.