Among the participants of the traditional velometer in the city of šiauliai, this bike stood out primarily for its unusually large capacity. Still, relatively compact and lightweight machine are just four people: two adults and two children! And the “passenger” seat only one, and the other three designated “working”. So that the rest of the family velotandem becomes most active.
Its original design represents the author — kievlyanin Sergei COWETA.
Velotandem consists of a General frame with two foot runners and a synchronous transfer to the rear wheel, front swivel wheels with individual wheel drive and a lightweight trailer to transport the marching of the property and products on long-haul routes.
Let’s start with the main element of the frame. It is assembled from two identical Velor from pedal cars of type “Tourist”, “Satellite” or similar. One cut off the upper and lower front rear fork, the other cut along the axis of the steering column. After that, both of the workpiece is mounted at the butt each other strictly in the same plane and weld (you can use brass brazing). To ensure accurate alignment I recommend to use a pair of corners, pre-strengthened them tightly on both sides of the carriage bushings. Obariv splice, corners removed, and then also by welding is fixed a tubular spacer between the BB nodes.
Hard boot made from previously cut off the top and bottom of the rear struts, privativa them to the frame. On the trunk is mounted a folding child seat, allowing the baby to take as sedentary and polulezhachee position. The front lower part of the frame of the chair there are two special grab, by which it is secured to a transverse tube of the frame and back strap with a hole through it, “passenger” seat is fixed threaded stud. High upholstered backrest with headrests attached to the seat frame with a hinge. The angle of the seat back adjust safety strap with attached metal carabiner clip and three rings. To the child’s foot is not caught in the spokes of the rear wheels on both sides establish a special Shin guards-foot pegs.
For easy transportation of velotandem and storage in the apartment, the frame is made collapsible, with special couplings (see Fig.). In scheduled areas the frame cut, the slices are cleaned from the paint on the length of the coupling parts. The compression ring and the bearing bushing at the inner diameter should match the diameter of the frame tube in the cross section (in the figure as an example, shows a coupling for pipe Ø 25 mm; pipe frame Ø 26 mm and Ø 28 mm size increases linearly). Both of these items and tightening of bushing wear on the pipe frame, after which the ends of the pipe flare. In tightening the coupling, it is advisable to drill four holes diametrically under a special key. In General, the design of the couplings provides a strong and reliable fastening of the frame elements, as evidenced by a respectable mileage of my vehicle.
In the area of the front Dobby unit frame reinforce the two steel rails. Should also strengthen and the tips of the rear wheels, privaris additional strip thickness of 3-4 mm.
Front fork it’s best to borrow the bike “Tourist” or “Satellite”. To use this detail from the models for “Start”, “champion road” and track machines are undesirable: they do not meet the required qualities. The plug must be modified. To do this, smooth out the inside of the crown and using a gas burner of hollow space is filled with brass. Perform this operation carefully, without overheating the feathers.
1 — frame, 2, 6, 19, 22 — couplings, 3 — foot star, 4 — reinforcing solitaire, 5, 8 — tensioning rollers, 7 — sprocket, 9 — tips mounting the rear wheels 10 is a cargo truck, 11 — backpack Ermak, 12 — ball joint hitch, 13 — rear child seat 14 neck support 15, 24 — harness, 16 — plate-side step, 17 — brake-spark, 18, 21 — seat for adults 20 — fixed wheel 23 — the back of the front child seat, 25 — bracket of the front seat 26 and the steering column, the 27 — crown steering fork, 28 — bracket-front carriage (seat tubes), 29 — the front carriage of a 30 — strut front carriage (lower front rear fork), 31 — pen of the front fork.
Frame Assembly and its component elements.
Frame Assembly and its component elements:
1 — frame serial bike 2 — remove elements (shaded), 3 — trunk, 4 — bushing, rear wheels, 5 — strut.
Scheme a synchronous chain transmission.
The scheme of a synchronous chain transmission:
1, 3 — a synchronous pedal sprocket, 2 — bracket with roller chain tension, 4 — sprocket, 5 — sprocket driven rear wheel.
The model coupling frame.
The model coupling the frame:
1, 5 — upper frame tubes, 2 — compression ring, 3 — compression sleeve, 4 — bearing bushing.
Bottle cage:
1 — belt guide 2 — clamp, 3 — clamp 4 — mounting bracket.
Installing the front carriage of a node requires special care: in no case be allowed to skew or deviation from the plane of rotation of the wheel. So first all the elements better a little tack weld, mount the hub as a whole, and only then finally to brew all joints. Also mounted rear fork.
Assembling the wheel, you need to make sure that he at turns did not touch the bottom of the pipe. Behind the helm set another chair for children aged from 5 to 10 years. The seat base is attached to the steering rod so that you can adjust its height position. It should be remembered that the child needs to get foot to pedal in the lowest position. The seat is also equipped with a safety belt.
The second fixed wheel is welded to sedately. However, here it is better to use brass brazing with a gas torch.
Brake better to install only on the rear wheel, but it is necessary to strengthen, even preferable to combine the two in one spark. The cables of the brake levers should be displayed on one yoke to the center of which attach to the main cable with a diameter of at least 3 mm.
The chain transmission device is clear from the figure. Synchronous pedal sprocket needs to be strictly identical, and the leader is selected depending on the upcoming operation. If you plan trips on dirt roads, the sprocket should have 28-48 teeth, if on asphalt, then a little more: 30-51 (lower value — for very hilly terrain with steep ascents; more for plains). Driving sprocket is attached directly to the second pedal through bolts.
Driven sprockets of the rear wheel it is advisable to make easily removable, and have at hand a set of five units with a number of teeth from 13-15 to 28-30. For chain tension rollers are used.
Given that the load on the wheels of velotandem compared to ordinary bicycles will increase significantly, is to increase the number of spokes to 71. To this end, the rim and flange wheel bushings between existing drill additional holes, Ø 2,5 mm. If the jumper wire between the holes are too small, then you can arrange them in a checkerboard pattern. In addition to the spokes I recommend to use additional flanges of sheet aluminum thickness 2.5—3 mm, which are appropriate to rivet to the existing flanges of the sleeve: it will also increase the life of the wheel.
Tandem trailers equipped with a trunk, it can be performed on the base of the backpack “Ermak”. For this purpose, the lower part of the frame of the backpack is attached with special self-made trolley with two pneumatic wheels, track width 800 mm, and is welded to the trunk bracket with ball joint hitch. The trailer can be worn behind the back like a regular backpack.
Because velotandem is a road vehicle must be equipped with light reflecting elements, security and alarm (“rotate”, “stop”, “backlight”) on the basis of the electronic relay. On the steering column install anti-theft device locks the steering. Do not forget about first aid kit and tool kit.
Not to take up unnecessary space in the trunk, I recommend to make a cage for drinking water and secure it to the frame using two clamps.
If necessary, the entire velotandem disassembled and Packed in a special cover size 900X900X800 mm.
And now a few tips on maintenance. Making machine, do not rush to sit on her own family. You must first run the new most — as long as the feeling of “tail” will not be for you familiar. Only after that give us a leg up partner. Rotate the pedals at first have command of the leader: “forward”, “stop”, etc. And only when adult members of the crew learned to work together, we can bring the children. But be doubly careful. Remember that the tandem has an increased acceleration time and braking distance.
In conclusion, our tandem has proven itself not only in the walks of the day, but in the long journeys — such as, for example, the mileage of nearly 500 km along the Northern Caucasus and the Crimea, successfully passed the us in 12 days. And just a five-year operation velotandem overcome 30 thousand km without major breakdowns.

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