SPEED CHANGE CRANKSETAs you know, for different road conditions: descents, climbs — many types of bikes use a block of sprockets of different diameters for changing torque to the rear driving wheel. These mechanisms are relatively complicated, high cost structure, which does not allow to use the foot brake. But torque can be adjusted by changing the length of the connecting rod! And their mess is easy to exercise at home on all road bikes.

Figure 1 shows a “three-speed” rod. Every Dauch levers regular pedals securely welded steel plate with three blind holes. On the threaded end of the shaft nahodou pedals tightly screwed steel sleeve with a diameter of 18 mm, freely included in any of the three blind holes (with a gap of 0.3—0.5 mm). Every pedal is equipped with a homemade tulipson (see “modelist-Konstruktor” No. 5’2000), densely pressing to her foot. Remove the legs from tulips while riding and stops you do not need; if you need to “switch gears”, the cyclist removes his foot from pedal to the side, bringing a sleeve from one hole lining, and easily and quickly brings it (with end of chamfer 1,5×45°) and an adjacent hole, changing the torque. Then the same actions are taken with the left foot. The whole process takes no more than five seconds. When you stop any foot is on the ground with the pedal. Tulips besides help pull the pedal up, increasing the capacity of the drive.

Figure 2 shows a variant of the “two-speed” rod. The pedal with tulipson tightly threaded into the additional, shortened by using the abrasive cutoff wheel (or hacksaw) the connecting rod. In the middle of the drilled hole with a diameter of 8 mm, into which is tightly pressed and priaary the smooth part of the step proselki. The threaded part is screwed in freely (for possible rosarote threaded M14 additional connecting rod by 180°) into the threaded hole of the main connecting rod to the axis of the pedal. Since the thread on the left and right cranks in different directions, for the manufacture of polospieler better to use the respective axes of the pedals by cutting and protocel them on the machine. The thrust pin is pressed into the main rod and fixes the position of the additional rod in accordance with the requirements of the road.


“Three-speed” rod:

1 — staff rod; 2 — pad (steel 45); 3 — adapter sleeve (steel 45); 4 — pedal; 5 — a pedal; 6 — tulips (pedal and tulips shown schematically)

In figure 2A the total length of the connecting rod and the maximum is 210 mm, which is preferable when driving uphill, when you need considerable torque. Figure 26 shows the position of the pedal with the minimum length of the connecting rod lever (140 mm) — for fast pedaling on a flat road.

Pedals and feet during the rotation do not relate to any roads or wheels. (Although it is possible that in the first embodiment have a little vegnuti hammer the rear fork of the frame to the elongated connecting rod is not clinging to it).


“Two-speed” rod:

1 —staff rod; 2 — the thrust pin (steel 45); 3 — poluchili (modified pedal axle from an old bike); 4— further shortened the rod (from old bike); 5 — pedal; 6 — tulips; 7 — a pedal (pedal and tulips shown schematically)

The movement of the pedals in both end positions easy to carry out on-the-go. It is important that it is still foot braking for both positions. Tulips help not only “to pedal”, and push the pedal to hard pins. Here, the leg should easily be removed from toeclips when you stop, as in this embodiment, the pedal connecting rod connected rigidly.

As you can see, both options are simple, technologically advanced available in the manufacturer and effective that showed their testing.

V. GAVRILOV, Pavel Inozemtsev: on, Stavropol Krai

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