Gear ratio of leading and driven stars
The sprockets on high-speed bikes are located on the right crank arm (driving) and the rear wheel hub (driven). Through the chain, there is a transfer of forces from the front gears to the rear. Interestingly, the rear wheel, on the contrary, is the driving wheel, and the front wheel is driven.
Gear ratio is the difference between the dimensions and the number of teeth on the stars. This parameter directly affects the travel speed and transmission power. A high gear ratio is provided by a large drive and small driven gears, a low gear ratio, on the contrary, by a small front sprocket and a large rear sprocket. Accordingly, the gears on the classic transmission in the first case are 3 x 8, and in the second 1 x 1.
The larger the chainring, the higher the speed. For example, there are 44 teeth on the front for the chain engagement, and on the back there are 11 teeth. For one revolution of the pedals, the rear gear will make 4 revolutions. If we take gear 22 to 11, then only 2 wheel revolutions will be made here per pedal rotation. At low gears, the opposite situation is observed: in front of the chain stands on a 22-gear gear, and at the back on 32. The gear ratio is less than 1, that is, for 1 revolution of the pedals, the wheels do not have time to turn completely.
High gears are designed for fast travel on a flat road. On hills, in headwinds and in poor road conditions, lower gears are used. the speed of the bike is lower, but more power and less energy consumption. Medium star ratios such as 2 x 5 and 2 x 6 are often used.
Each star in the system has its own range on the cassette. It can “float”, that is, the same reverse gear refers to two stars of the system at once, but, in principle, the pattern is as follows:
What do we have for single speed bikes? There are only a couple of gears, a classic gear ratio of 2. Corresponds to the average performance on high-speed models, intended for movement on asphalt, compacted soils, conditionally acceptable on short climbs.
You can increase the speed of a single speed bike yourself if you put a larger diameter sprocket in front. For frequent overcoming of slides, it will be more relevant to increase the size of the rear gear.
And finally, how the programs are numbered. In the system, the asterisks are arranged in descending order, on cassettes. in ascending order. The outermost gears are the highest gears, the innermost gears are the lowest. The smaller chainring corresponds to the first gear in the cassette, the last gear. According to the number of stars in front and behind, the gearing of the transmission is determined, for this we multiply the numbers:
- 1 x 7 = 7 gears;
- 3 x 7 = 21 gears;
- 3 x 8 = 24 gears;
- 3 x 9 = 27 gears.
Etc. Do you need so many “speeds” in practice? It all depends on the riding style and the area of use of the bike. However, it is important to choose the correct sprockets. this way they and the chain will be subject to less wear and tear, and travel will be more comfortable. And if the transmission allows you to select the gear with maximum accuracy, then this is how it should be done.
Sprockets are transmission units for the implementation of a chain transfer of forces from the cyclist’s legs to the rear wheel. Bicycle sprockets play a paramount role. without them, it simply will not go. Single speed models are supplied with a pair of leading and driven stars. Bicycles with multi-speed transmissions are equipped with speed kits front (system) and rear. ratchet or cassette.
The number and size of the sprockets determine the bike‘s flexibility in various road conditions. Thanks to the correct gear ratio, you can significantly reduce the energy consumption for the trip and move at a comfortable speed. The durability of parts depends on the quality of the material, the riding style and the quality of service. with proper care, even the “initial” stars will ride longer than professional, but neglected ones.
Types of fastening stars on a cassette
Let’s go back to the classic round cassettes. Unlike ratchets, they differ in the type of attachment to the drums. Bicycle cassettes are:
- collapsible on a single drum with separators;
- on a spider;
- on blocks (several spiders);
The first type of cassette is the simplest. all the stars are installed on a single spline drum. They are separated from each other by partitions. spacers. The disadvantage is the constant load on the drum. But the indisputable advantage is that they are easy to disassemble and change one asterisk. They are easy to clean, but the components are more likely to get dirty.
Spider. Lite version of the collapsible cassette. The load on the drum is not so big. here it does not come from each star, but only from the spline mount of the spider. These cassettes are lighter, less likely to get dirty.
The multi-spider design includes multiple pairs plus small stars individually attached to the drum. The model is very convenient because the new block is easy to pick up and, unlike a collapsible analogue, you don’t have to fiddle with spacers for a long time and lay out the entire cassette. The development of this thing belongs to the Japanese manufacturer of parts Shimano.
The Open Glide is a one-piece set that fits onto the largest gear. Unpretentious model: thanks to high-quality material, less wear and tear, long service life, low weight. True, cleaning a heavily soiled cassette is problematic.
The X-Dome system is represented by a similar design. Here, both the big and the small stars are in contact with the drum. A solid-milled block of 7-8 stars is mounted on them. Both Open-Glide and X-Dome are SRAM.
Oval stars, different from round
Oval Star. New Or Retro Splash? We can say both. Experiments with the shape of gears for a chain drive (namely, giving it a flattened shape) began in the nineteenth century. Then it was somehow forgotten, and in recent years it has returned and is actively introduced into the modern cycling life.
The eccentricity of the star is slightly greater than zero, so the shape is close to a circle, by analogy with the Earth’s orbit. The maximum constriction can be up to 30%. They are not popular in our time, the release is more aimed at racing models.
The ellipse rotating around the axis redistributes the loads in its own way and changes the efficiency of the transfer moment.
Consider what are the features of ellipsoidal gears:
- jumps in the gear ratio of the stars;
- more even distribution of loads. a decrease in them with the horizontal position of the connecting rods and an increase in the vertical one;
- overclocking is pronounced;
- additional loads on the carriage shaft.
In accordance with this, we will analyze the pros and cons of such stars in comparison with round ones:
|The bike will roll up the hill faster||Faster rear cassette wear|
|Better low cadence pedaling in high gears||Increased load on the carriage|
|Acceleration by additional pushing torque (system)||Need to pedal more often in low gears|
|Even distribution of muscle stress, less fatigue on flat areas||–|
|Easier to ride MTBs with powerful cushioning||–|
An elliptical drivetrain pays off when you have to pedal at low cadence. Compared to the round counterpart, it provides some advantage in accelerating the bike from a standstill. There is also a change in the gear ratio without switching.
- front. horizontally, back. vertically;
- in front. vertically, driven. horizontally;
- only horizontal position;
- only vertical position;
- deviation: for example, the leading sprocket is strictly vertical, and the rear sprocket is at an angle from a straight line.
Thus, the oval system and cassette leave prints of fundamental differences on the bike: both in appearance and in ride quality.
How to clean and lubricate sprockets
Rubbing mechanisms require periodic lubrication and cleaning from dirt. This will improve ride quality and extend the life of the transmission. Chain guards are often included with the classic single-speed models. It is recommended to leave it. It also protects the chainring from excess dirt.
Already after a few rides through forests, cross-country and off-road, the mountain bike is overgrown with mud. And if it is clearly visible on wheels and frame, then in mechanisms it is not always. Therefore, more often you need to inspect your two-wheeled horse and take action in time.
Cleaning the bike cassette: 1. Release the rim brake (remove the caliper on the disc brake), remove the rear wheel.
Inspect for dirt. If everything is very bad, you will have to remove and disassemble the cassette. For light dirt, can be cleaned directly on the wheel.
For cleaning, it is better to use special narrow brushes. They allow you to crawl into the deep gaps between the gears and find a lot of interesting things there. And it is much more convenient than getting into the gaps with a rag.
You can clean the teeth with an old toothbrush or wipe off the abrasive with a soft cloth.
After that, wipe the surfaces with kerosene, allow to dry and apply grease to the teeth and pits. It is recommended to clean and lubricate the chain at the same time as the cassette. This is the only way to achieve the desired result.
Cleaning the system is done by analogy. Everything is simpler here: you don’t need to remove the wheel, just a few stars. True, you need to work carefully so as not to damage or upset the switch.
Sprockets are the most important components of the transmission, without which movement is impossible in principle. Correct selection of gears, periodic cleaning and timely replacement of worn components will avoid unpleasant surprises on the road, and a high-speed bike will really be high-speed, and not only ride in one gear.
Drive sprocket switch adjustment
Over time, the chain flip worsens, the gears shift poorly, or even fail altogether. Since there are few stars in front, it is simply impossible not to notice the malfunction.
If the problem of a tight jump of the chain or its absence is caused only by a detuned switch, then it is quite possible to save the situation on your own. Why is the switch not working properly? The main reasons include:
- mismatch of the gear with the planes of the stars;
- poor tension in the drive cable;
- the switch is loose.
As practice shows, these problems do not come one at a time, so you will have to adjust everything at once, and not just, say, the tension of the cable.
At the first stage, we wipe the body of the device, as well as the sprockets and the chain from adhering dirt and dust. We check the mounting bolts of the switching device housing, tighten it all the way if necessary. Important: tweaking a loose switch does not make sense!
Next, we find the screws “L” and “H”. adjusters of the position of the shifting gear. We loosen them, but do not unscrew them completely. Our task is to tighten them in such a way as to achieve the coincidence of the gear with the planes of the outer stars.
- Switch the chain to position “1” at the front and “maximum” at the rear. If the system works very badly, the chain is installed manually.
- Tighten the adjusting screw to achieve full alignment of the shifter gear with the plane of the first chainring. Deviation up to 1.5 mm is not critical.
- Loosen the cable fastening nut, tighten it a little.
Front derailleur H setting:
- Set the chain in reverse position: “maximum” in front, “1”. behind. For system 38, this will be “3” and “1”, respectively.
- Tighten screw H until the shifter aligns with the large sprocket.
- Tighten the cable in this position.
When the limits are set, the chain swap should be restored. If the screws are clearly set, and the system does not work well, we try to tighten or loosen the cable. How to determine? Gears go tight from high to low. tighten, on the contrary. loosen the tension.
How to properly shift gears on a bike?
Even in the distant past, singspeed was the only bicycle option among the mass of the population. Happy bike owners felt great on smooth asphalt, but had to adapt to rough terrain: to forcefully pull the pedals up on the slopes, accelerate from descents to “take off” to the next hill, lower the tires to drive on uneven dirt. Sometimes the skills were no longer enough, and the cyclist left the saddle to go through an unfavorable area on foot.
Over time, everything changed: manufacturers began to produce a large volume of “highly specialized” bikes. road bikes, mountain models, hybrids, sports, etc. The former leader in the person of single speed has noticeably receded into the background and is bought exclusively for trips on highways and light dry primers.
Most modern bicycles are equipped with so-called speeds. The most common variant is an open sprocket transmission. It is used on all types of bikes, including city bikes. Shifting gears on a bicycle allows the cyclist to adapt his transport to specific traffic conditions, as well as to rationally use his own strength.
The presence of speeds, of course, gives an advantage over the single-speed version, but the benefits are manifested with skillful use of it on the road. There are simple principles that will tell you how to properly shift gears on your bike and not collapse with fatigue after each ride. But even with proper operation, the speed system fails over time, so you need to be able to configure it.
Speed Bike Transmission Sprockets: Recommendations for Use
Bicycles with an open gear system have two derailleurs, which are responsible for the chain jump from one sprocket to another on the drive and driven cassettes, respectively. For reference, the driving sprockets are the front or “connecting rod” sprockets, the driven ones are the rear ones, at the drive wheel. There is a small paradox, as in the numbering of asterisks.
The front ones are counted “from small to large”. The standard cassette set is three stars. The first is the smallest or lowest gear. Next comes the second, middle gear and the system is completed by the largest, “highest” star.
Reverse gears are counted in reverse: the largest sprocket corresponds to the first gear, and the smallest gear corresponds to the highest gear. The number of sprockets is several times greater than the set of front ones, therefore, for each gear in the front cassette, several rear ones are selected.
The chain switching devices are controlled by shifters on the steering wheel: left. front, right. rear. The first rule of changing speed is not to confuse them with each other. Chain jump occurs only when the bike is moving forward by pedaling. It is unacceptable to change the gear ratio in the reel, as on the planetary hub.
A few more important recommendations for switching:
- sequentially, through each asterisk;
- before entering the rise, select the gear in advance;
- avoid excessive pressure on the pedals when throwing the chain.
And one more thing: we never experiment with the transmission, pedaling in the opposite direction.!
Now let’s touch directly on the question of how to choose gears for specific driving conditions. The general rule of thumb is: on a flat road, we increase the gear to the maximum at which we can maintain a suitable cadence and ensure the maximum travel speed. When driving downhill, against a strong wind or off-road, we lower the gear, ensuring the bike’s cross-country ability and uniform load on the legs.
The largest star and several of the smallest are responsible for the highest gears in front. This position of the chain will provide a minimum acceleration time, high speed and roll-off. For standard 37 (8) transmission systems this will be position “3” at the front and “1” through “5” at the rear. Faster, more precise gearshift systems have a wider range of sprockets.
The middle chainring is activated when small obstacles appear in the path: wind, sand on the road, gentle hills, and bumps on the road. In system 38 for the second sprocket, the lower limit of the rear cassette is shifted one, and the highest. two stars back. Recommended positions are 23, 24, 25 and 26. The second front, third rear chain position brings the speed bike closer to single speed performance. Lower gears reduce speed, increasing flotation.
On a mountain bike, gear ratios are actively used with the position of the chain on the first front sprocket. Rear sprocket ranges from 6 to 8. Low gears are used in tough conditions: winding trails, mud, sand, bumpy dirt and steep climbs. Movement speed is minimal, while cadence and leg loads are maintained.
It is strongly discouraged to use higher chainrings and lower rear sprockets, and vice versa. Overuse of such experiments will quickly destroy the stars, circuitry, and very expensive switches. In general, the chain skew between the front and rear cassettes is present even in the normal position, so aggravating it is more expensive.
If we talk about sensations, then the cyclist with the wrong position of the chain will feel one discomfort from the high-speed bike. Correct use of gear ratios is the key to successful riding and a long service life of the transmission!
Rear gear setting
The next step is to adjust the chain travel along the rear sprockets. Most often, it is there that problems are observed, and it is no coincidence: there are more stars, plus a tensioner. First, carefully clean the mechanism of dirt.
- Checking the cock and bolts.
- Gear Limit Adjustment, Cable Tightening.
- Selection of the optimal chain tension.
A bent cock must be replaced. Simultaneously checks if the switch is loose.
- Loosen both screws.
- Throw the chain to the highest (smallest) chain (front to maximum).
- Tighten the bolt “H” until the derailleur idler is aligned with the sprocket in one plane.
- Engage first gear (largest, and in front. first).
- Turn the “L” screw to match the roller with the star.
- Check switching accuracy.
- Tighten or loosen the drive cable. Determined according to the same principle as with the front derailer.
Is the gear not shifting quickly, the limits are set correctly, and the cable is well tightened? Then it’s time to work with the chain tensioner. Find the special screws “A” and “B”. The first adjusts the position of the frame relative to the smallest, and the second. to the largest asterisk.
Adjustment is carried out according to the principle: change to the appropriate gear and tighten the screw. By turning the knob “A”, the tension force is increased by raising the frame to the higher sprocket. Conversely, screw “B” lowers it to the large sprocket. An incorrectly set tension does not make it possible to easily select the desired gear: a too loose chain can hang in the space between the sprockets, and an overtightened one can break due to excessive tension.
Periodically adjusting the derailleurs on a speed bike is considered normal. It will be invaluable when the chain and cassettes are in good condition. Setting up the gearshift system in combination with the rules of use when cycling will significantly increase the resource of all components of the transmission, as well as use its resources to the maximum.
Bicycle gear shifting
Any cyclist should know how to properly switch speeds on a bicycle. When they buy a bicycle for children, they are always interested in how many speeds it has. And the higher the number of speeds, the better. But experienced cyclists know that the speed of a bicycle depends on the rider, or rather, on the work of his muscles. And the art of competently changing gears is the quality of cunning professionals, which allows you to squeeze the maximum possible resources out of the car in rough terrain.
It used to be simple: the road bike had one speed. Therefore, on the plains, everything depended on the skills of the cyclist himself, and to ride in the mountainous terrain, one had to adapt to the terrain conditions: while riding downhill, the cyclist accelerates the car as much as possible in order to enter the next mountain by inertia. If the ascent is protracted, then the cyclist rides uphill until he can pedal. Then he dismounts his bike and proudly walks alongside to the top to continue his journey down again.
Modern bicycles have two sets of gears. front (sprocket) and rear (driven sprocket). It is extremely important to learn how to choose the right gear depending on the nature of the ride. First, you need to learn a few simple rules for shifting gears:
How to Choose the Right Gear Ratios for You and Your Bike
- There is no need to change gears when the bike is stationary. This could damage the switches.
- You should change gears even before your speed drops in front of difficult-to-pass areas (for example, sand or loose snow) or on the rise.
- You don’t have to pedal hard when changing gears. Switching is easiest if there is no load on the circuit and there is a speed margin.
- When switching, you need to make sure that the chain is not strongly skewed. That is, you should not use a large chainring and a large rear sprocket. In reality, you should use the following gears: with a small star in front to 4-5 stars in the back, from the second front. from 3rd (2nd) to 6th (7th), and with a large front. from 5th to last 8th (9th).
Now let’s talk about choosing stars. It is impossible in advance to accurately match a particular gear to specific road conditions. Of course, there are many formulas, graphs and tables, but most of them are calculated for road bikes, fair weather and smooth asphalt. Should the conditions change, and all the calculations are down the drain. The choice of gear depends on the road or lack of it, the slope of the track, temperature, soil conditions, tire pressure, wind, the physical condition of the cyclist, adrenaline and blood sugar levels. There are other criteria that cyclists can be guided by. One of them is cadence. It is known that the optimal cadence when driving on a horizontal surface. for example, on road bikes. is an average of 95.115 rpm, while for cross-country riders this value will already be 70.90 rpm. But for amateurs and cyclists, this is just a guideline, not a rule. There is no need to try to start immediately from high gears, first in low gears we warm up the muscles, unwinding to optimal gears. When choosing a gear, as in any business, the cyclist needs to stick to the “golden mean” and not go to extremes. A slow pace of driving in large gears is very detrimental to the condition of the knee joints. Pedaling too often will reduce riding efficiency and fatigue more quickly. In difficult road conditions (driving on mud, sand, grass or snow), the gears are lowered due to the need for a torque reserve. The technical capabilities of the switches do not always allow the chain to be dramatically shifted from small stars to large ones. For mountain hikes with backpacks, a set of chainrings, for example, 48, 38 and 28 teeth, is usually sufficient.
When driving against the wind or uphill, you need to switch to “lower gears” close to 1: 1). This set of gears increases cadence but decreases speed. When driving on flat terrain, the gear ratio can be 4: 1 to maintain speed. In a motorcycle race, a speed of over 100 km / h can be achieved. In these record-breaking rides, cyclists use a gear ratio of 8: 1 or more. However, usually the muscle strength of the legs is not enough to spin such gears from a place. Even athletes do not use gears greater than 5: 1, but rather increase their cadence.
Sprocket ratios. Part 2
In 1985 in the United States, John Howard set a speed record of 245.077 km / h. For the first time he covered 241 kilometers on a bicycle in one hour. Ten years later, Rompelberg Fred from the Netherlands broke his world bicycle speed record with a result of 269 km / h.
Many novice cyclists avoid frequent gear changes and even when riding upwind, leave the chain on the large drive and small driven gears. Their ride is more like the maneuvers of a sailboat against the wind. As a result, after such a ride, knee pain can naturally occur. Meanwhile, a competent cyclist when riding upwind, having reduced the gear ratio to 2-3: 1, will be able to maintain a higher speed with less effort. In small gears, pedal at a frequency of 80-90 rpm.
Thus, some recommendations can be made:
- At the beginning of the season, it is recommended to drive at least 200-300 km in low gears and with a high pedaling frequency.
- Morning “rolling in” is better to start with lower gears for 15-20 minutes.
- Long-term cycling is aided by an even cadence at a pace that is comfortable for the cyclist. With the right gear selection, this can be achieved even on a hilly track.
Assessment of the general condition of the bike
If the pedals on the bike are scrolling, before moving on to disassembling its components and thinking about repairs, it is worth assessing the general condition of the bike. First of all, you need to check how correctly the rear and front derailleurs are set, which are responsible for changing the speeds. A failure in the settings will be indicated by an uncharacteristic annoying crackle while driving, as well as a fairly regular hit of the chain between the sprockets when pedaling.
Sometimes the problem affects bikes that do not have a gearshift system installed. In cases where the pedals on a bicycle of a similar plan are scrolled, first of all, you should pay attention to the condition of the chain. It may just take a thorough cleaning and lubrication to fix the trouble.
Damage to sprocket cranks
As for the reasons why the cranks of the sprockets are damaged, this is most often caused by the implementation of excessive pedal pressure during driving. Notches on them can “lick” naturally as a result of friction. The end of the life of the sprockets is bound to cause problems with the cranking of the pedals.
In some cases, the trouble can be eliminated by flushing the sprockets from accumulations of old oil, debris and adhering dirt. To remove these impurities, it is enough to carefully wipe the parts with a piece of material moistened with kerosene.
If the problem is serious and there are not enough teeth on the sprockets, you need to dismantle the functional unit, disassemble it and, if possible, replace the damaged elements with intact ones. Naturally, the most reasonable solution in this situation is to install a new set of stars. However, this option requires significant cash costs.
Old bike chain slips
She stretched out to a critical level. If you want to be sure. purchase one of the control devices and estimate the degree of elongation:
- Special Chain Gauge. The meter is simple and convenient.
- Calipers. From the point of view of accuracy, this tool is preferable to the caliber.
- Roulette. The most inaccurate device.
A new chain slips
It would be nice to replace the cassette. If the previous chain did not jump over the stars, then you can leave everything as it is. the “novye” will roll in and the smoothness of the course will be restored. Depending on the degree of “stretching” of the teeth, running-in will take from 50 to 150 km.
Attention! Remember to inspect the system sprockets and ratchets. Please note that leaving everything as it is, the chain resource in km will be lower.
Why Mountain Bike Chain Slips Under Load
There are, in fact, only two reasons. The rear derailleur is incorrectly adjusted or the chain and sprockets of the system and / or cassettes are worn out.
How to fix the trouble? The root cause here may be the stretching of the cables, the presence of dirt on the gaskets. The solution is to remove them from the jackets and flush the connections from rust using a special WD40 tool. In the event of a break or critical damage to the sections of the cables, you will have to replace them with new ones.
Should I lubricate the ropes with oil? Experts do not recommend resorting to such actions. It may be easier to change gears at first. However, over time, the grease-coated cables will adhere to dirt, making them much more difficult to move.
5 Minute Gear Adjust | How To Set Up Your Mountain Bike Gears Correctly
It is necessary to lay the cables in shirts so that their bending angle remains minimal. This will avoid excessive friction.
After servicing or replacing the cables, it remains to re-adjust the gear selectors. Finally, you will need to ride the bike, checking if the pedals are cranking as before.
The problem may be due to the overstretching of the chain. In this case, it begins to sag unnecessarily, which leads to a weak grip of the sprockets and, as a result, pedaling. How to tension the chain? To do this, you will have to shorten it. So, on one of the links there is a special latch that opens the ring connection of the chain. Having removed the part, it is enough to remove one or more links, knocking out the bushings from them with a hammer and a metal breakdown. In conclusion, it will be enough to connect the circuit back to the same latch.
If the above actions did not solve the problem, you will have to replace the chain with a new one.
Bicycle belt drive and its features
A belt-driven bicycle is an unusual type of transport. It got the name Gearbox Bike, which means “bike gearbox“. Gearbox Bike has been growing in popularity lately, and sales are increasing at the same time.
Before choosing just such a bike, it is better to know a little more about it. On its advantage over a chain-driven bike. It also does not hurt to study the shortcomings and design features of this type of transport.
Belt drive bike. what is it?
Bikes equipped with a belt drive look like ordinary bicycles. What distinguishes them is the presence of a belt that replaces the chain. But such a change leads to some changes in the design of the bike and the functionality of the ride of the vehicle.
It is not equipped with a “rooster”. an adjusting tension roller. A rather vulnerable part located close to the road surface. Classic gear shifting doesn’t fit on these bikes.
The main advantages of the belt drive:
- Durability. There are no rubbing parts on the belt, it does not rust or shrink. Material. composite. durable and reliable. The service life of the belt is several times longer than the service life of the chain.
- The part does not need constant maintenance. For example, in lubrication. Accordingly, there is less dirt and less money spent on finance.
- Easy maintenance. just wash the belt with water.
- Light weight. The material of the belt is much lighter than the metal from which the chain is made.
- Quiet ride, as well as a smooth ride.
- A belt-driven bike is good for year-round riding, when owners of a bike with a chain sometimes do not risk driving into the snow.
- Clearance (ground clearance) is greater. Increased permeability.
- It’s easier to move up. This is facilitated by the lack of inertia, which was created by the mass of the chain.
- The planetary hub, which is installed with the belt and sprocket, is more reliable than the cassette.
- Nice appearance, assembly. Some cyclists prefer the design of these particular bikes.
Belt drive design features
Fitting a belt drive system to a conventional frame is very difficult. Even in the case of a decision to replace the frame, other changes need to be made. It is necessary to install the hub (planetary) on the rear wheel. Ahead it is necessary to change the cables, as well as the pins. If you like a belt drive, it’s still easier to get a new bike with it.
The gearbox includes 7 to 9 pairs of gears. A nine-pair bike is equivalent to a 24/36 chain drive vehicle and an 11/34 cassette. The box structure consists of three shafts. The first one receives the torque, after. it transfers to the second.
The task of the secondary is gear shifting. Consists of a movable sleeve. When it moves, the splines engage. The third shaft contains a toothed belt gear. Since the second shaft does not carry any additional load, this design is considered durable and also reliable.
After examining the design features, it may be believed that bicycles with a strap are heavier than with a chain. After all, the number and thickness of the gears are greater. But the chain is much heavier. In addition, the classic model is equipped with two switches, one of which (rear) has a lot of weight. Therefore, the manufacturer’s statement that the weight of bicycles with different types of gears is approximately the same does not make sense.
There are several disadvantages to using a belt drive:
- Such vehicles are not suitable for competitions and aggressive driving.
- The price of a bike with a belt drive is higher than with a chain. But the difference can be compensated for by saving lubricants, high service life, and therefore repair costs.
- Non-standard parts as well as tools. In the event of a breakdown on the go, repairs are more difficult. over, not all workshops will be able to help yet.
- The inability to open that exists on the circuit. To install or replace a part, there is a need for a special frame.
- A good belt tension is required, which cannot be passed through a regular sports system. It means either a bicycle with one gear, or a hub shifting system. In the latter version, the bike is slightly heavier.
- Weight gain due to bushing weight. And the increase in the mass of the rear wheel makes itself felt when driving.
Chain drive benefits
The gearless drive itself works very efficiently on slopes and flat surfaces. But at the same time, a cyclist, starting from a flat surface without a speed switch, or starting an ascent with the wind moving towards him, is forced to pedal while standing, spending considerable effort on this. At the same time, the driving pace drops to a minimum. The chain drive with gears allows the rider, regardless of the terrain, the direction of the wind, to pedal throughout the ride at a pace that suits him. On the first bicycles with high wheels, the pedals were located on the wheel itself, that is, one wheel revolution was equal to a full pedal rotation.
The ratio of gears can be changed by the cyclist himself at his will. For example, when conquering a steep slope, the rider can choose a gear in which the pedals will rotate more easily and more often, while the wheel itself will rotate more slowly. That is, an easy transfer will be performed. Heavy gear is selected when it is necessary to cross flat terrain or when going downhill: several wheel rotations occur per full pedal turn. In the transmission, a large sprocket is in the front, a small one in the back. To spin the wheel, a certain effort is required and the more you create it, the more revolutions the wheel will make.
Chain drive in transmission and its action
A chain mechanism is a mechanism that connects the pedals to the driven wheel. Thanks to the chain mechanism, the force acting on the pedals is transformed into the rear wheel. Thus, the bike is set in motion.
In order to have a minimal idea, as well as to understand the essence of the chain transmission, you need to prepare the following items:
- several spools of thread. One coil should be either larger or smaller, and the other pair should be of the same size;
- rubber bands;
- flat boards made of wood;
- a pack of nails.
On a wooden plane, with the help of nails, spools of threads are fixed at a considerable distance from each other. It is necessary to strengthen them in such a way that when they are connected, the elastic does not stretch, and the coils themselves can move freely and easily. After that, connect the two coils with an elastic band.
Observe how one coil behaves in relation to the rotation of the other coil. What is visible? They move in unison, with the same speed and direction of rotation.?
In what ways can you investigate the transmission:
- It is necessary to make notes using a special marker on both coils, and then turn them. For this, two coils are used, one of which is larger in size than the other. So, how one coil rotates relative to another?
- Make one rotation on the elastic so that it describes an eight. How this circumstance affected the rotation speed and direction of movement of the coils?
- Inspect the bike chain and derailleurs. Is there a similarity to a bicycle drivetrain? What is their difference?
Diagnosis of the transmission system.
Gears help the cyclist to pedal most efficiently, allowing him to easily and quickly conquer the steepest climbs and some obstacles.
What do you need to take to demonstrate the work of the programs? What materials should be prepared:
- a bicycle equipped with gears;
- a bar of soap and a roll of duct tape;
- a sheet of paper and a simple pencil.
Frens twist and penny farthing
Paul Dougherty claims that this method of calculating the gear ratio is one of many similar ones. In the UK, gear ratios are calculated based on the diameter of the large wheel of bicycles called Penny Farthing. It was stated above that Paul Dougherty used a 2: 1 ratio. That is, when transforming, it was necessary to double the diameter of the rear wheel. This means a 2: 1 chain drive with a 27-inch rear wheel would be considered 54-inch. So, having determined the circumference of the wheel, we multiply it by the gear ratio. That is, if we use Paul Dougherty’s method with a gear ratio of 2: 1 and a driven wheel circumference of one and a half meters, we get the drive wheel circumference. It is equal to three meters. This method, unlike the English system, helps to determine the value of the distance traveled, or to understand how far you have gone.
The metric system was used in France. Metric is called the decimal system of units (SI), which is based on the application of the gram and the meter. Today the SI system is called upon all over the world. In this system, the conversion consists in the product or division by the number 10, that is, in the decimal fraction, the comma is simply shifted.
When it comes to threads, the metric system indicates its pitch and diameter. The thread pitch is the distance between the threads. Take, for example, the popular thread size M5, which is used for the anchor bolts for attaching the cable, for attaching the bottle cage, in the holes for attaching the wing or trunk, speed switch levers, is denoted M5.0X0.8, that is, the diameter is 5 mm, and the distance between threads is 0.8 mm.
Required number of teeth
Exploratorium scientist Paul Dougherty explains the gear ratio using his personal bicycle as an example. This method allows you to determine the number of leading (front) and driven (rear) teeth. For example, Paul suggests considering a transmission where the gear ratio is 54:27. Based on this ratio, it becomes clear the number of teeth of the front sprocket is 54, and the rear sprocket is 27, that is, with a full revolution of the front sprocket, 54 teeth pass around the drive sprocket. At the same time, the driven sprocket makes 54:27 = 2 turns, that is, the rear wheel turns twice. This ratio can be reduced to 2: 1. But if the driven sprocket has 11 teeth, then the gear ratio will be closer to 5: 1.
It is worth paying attention to the fact that with each full revolution of the drive sprocket, the driven cassette rotates twice as much.
It is necessary to set the gear so that the driving sprocket is the smallest and the driven sprocket is the largest. Use a piece of tape or chalk to mark the top of the rear wheel. At the same time, the pedals should be locked. Now you need to complete a full revolution of the pedals and count, as well as record the number of rotations made by the rear wheel.
At the next stage of the experiment, put a large star in front, and a small one in the back. How many revolutions did the rear wheel complete with a full pedal revolution? Which of the two combinations is the most suitable for tackling a steep climb? And which one is effective for sprinting on flat terrain?
Conducting an experiment with a medium range of gears.
To do this, you need to draw a table where the gear ratios will be entered, the number of full wheel revolutions per pedal revolution. Why, in your opinion, the development of a mechanism such as a chain drive contributed to the improvement of bicycles?
Using moving machinery
In the 15th century, Leonardo da Vinci worked on the development of the idea of the joint work of teeth and a mechanical chain. Surprisingly, this idea sounded long before the design of the first bicycle and only four centuries later found practical application. In order for the transmission to function effectively, the force created by the rider’s legs must be correctly transmitted to the rear wheel of the bicycle. The structure must be designed so that the pedaling effort does not create discomfort for the rider.
For this, engineering and technological developments were introduced, durable materials were used, which allowed the chain transmission to become an ordinary mechanism by the end of the 19th century.