EXTEND THE LIFE OF THE BIKEAssociate Professor of the Department “Technology of mechanical engineering” of the Mari state technical University M. L. Popov, having a great experience with Bicycle sport, sent a letter to the editor which described and theoretically substantiated his view on the problem of improving the reliability of the bearing unit of the carriage. Today we publish only constructive and technological proposal of the author. More than 20 years of experience continuous all-weather and all-season operation of my bike model-542 “Sport” issued in 1974, the total mileage of which amounted to about 100 thousand km, as well as analysis diary entries have led to the conclusion that the bottom bracket for reliability is in fourth place after floreina, driven sprocket and drive chain.

The nature of the failures is always the same: chipping treadmill on the shaft of the right (facing the bike) of the bearing unit of the carriage, and in the same area relative to the axis of the connecting rod.
Attempts to explain this phenomenon theoretically gave the following results: real angular position of the ruined bearing raceways accurately corresponds to the theoretically defined. Reaction forces in bearings of the carriage of a Bicycle can have a value in excess of the force on the pedal on the right…2.33 to 3.09, and the left — 2.13 times. That is, the bearings of the carriages of the considered structures, the static load of the corresponding bearings “100” and “200” in peak mode the motion of the bike (starting, acceleration, off-road driving, etc.) are much overloaded. The situation is exacerbated by the extremely low quality of bearing assemblies, assembled directly on the shaft of the carriage of several parts, precision machining which in conditions of mass production of bicycles leaves much to be desired.
This explains the quite frequent fracture site. To avoid such trouble, instead of teams of bearings were applied to standard bearings, ultralight series and 1000903 1000905. The shaft of the carriage, heat-treated in the factory, a little protochen. It has high bearing capacity, besides the neck it allow you to use regular cranks.
Updated the shaft of the carriage carriage is installed in the host Bicycle frame by means of two threaded housings and the intermediate sleeve. The right housing is secured to the stop, the one on the left is locked with a Bicycle lock-nut, enabling the adjustment of its axial position relative to the carriage.
To seal the bearings and protect them from dust and dirt, the slide closes on the right side of the threaded cover, and the left — with a special bushing pressed on the shaft.
All additional parts are made of steel grade of SOHGS, in extreme cases, you can use 45 steel.
At completion of the shaft it is necessary to provide alignment of the bearings (diameter 17 mm) and the common axis of the ledges under the connecting rods (diameter 16 mm). Practically this is feasible, if the “native” shaft bike has at the ends of the center hole, otherwise, you will have to make a adapter with center holes and install them on the connecting rod shaft neck carriage with a diameter of 16 mm. However, in this case, the cervical groove under the bearings perform in a single clamping position, using the right and left turning. The final operation is to grind the grooves with a cloth.
It is possible to make the shaft of the carriage again on standard technology, but in this case you will need harvesting from a fairly scarce material (e.g. steel 12ХНЗА), as well as performing a number of complex technological operations (including heat treatment of the necks under the rods).
Streamline Bicycle carriage
Upgraded Bicycle carriage:
1 — shaft, 2 housing-left bearing, 3 – lock nut 4 — sleeve o -, 5 — left side bearing 1000903, 6 — housing bearing right, 7-right side bearing 1000905, 8 – intermediate bushing, 9 — cover.

The right building should sharpen two mounting using a special threaded mandrel М35х1 ensuring the alignment of Seating surfaces. Technology of mechanical processing of the remaining parts is uniquely identified by their design and does not require comments. It is only necessary to accurately perform the mounting surface of mating parts in accordance with specified on the drawings tolerances.
When assembling the carriage, the main attention should be paid to the preparation of bearings (rinse thoroughly with gasoline “Kalosha” with solvent type.”Nefras or white spirit”; to blow the compressed air; to fill with grease “ciatim-201”, “ciatim-203” or “Litol”). After Assembly you need to check that there are no distortions, the axial and radial parentage and clearances as the bearings are very sensitive to blockage and parentage (maximum diametrical interference — not more than 5…8 µm). Ignoring these requirements leads to premature damage to the bearings. When properly assembling the shaft freely rotates by hand without appreciable gaps, and with attached connecting rods (pedals) on the overrun makes 10 to 12 complete turns.
Upgraded the bottom bracket of the proposed structure made according to the above technology, completed sea trials in the harshest conditions year-round two seasons (a quick trip on the highway in the summer, riding in the winter at temperature to — 30°C with increased load on the chain drive bike with studded or the rear wheel with a load up to 25 kg on snowdrifts, ice, snow Kiddle, ice porridge). The total mileage of the bike was about 12 thousand km No maintenance was carried out. The failure site were recorded.
Well established itself, and other variants of the node of the carriage. For example, instead of one of the right bearing 1000905 established couple 1000903. This design is implemented and tested on the machine “Start-highway” for two training seasons, has never failed me.
M. POPOV, candidate of technical Sciences, Yoshkar-Oops

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