Double Trouble.

Making a bike to carry two small children originally started out as an idea to modify a conventional mountain bike. Carrying a child to the rear and also at the front of the bike. This idea raised questions and concerns about the strengths and possible failings of such an arrangement. We decided to come up with something better suited to the job.

The primary function of the machine is to carry the two children safely. The way in which we chose to deal with the design criteria has produced something that is essentially a modified tandem. This feature has been purposely exploited so that the eldest passenger can eventually swap the central bucket seat for a bike saddle and a pair of handlebars.

The distance between the two seat tubes, the length of the tube connecting the bottom bracket shells, is considerable. It is longer than a conventional tandem and joined with an array of tubes specifically designed to accommodate the front child seat. The seat attaches via a customised carrier and two 8mm stainless bolts fastening through reinforced conduits in the tubes. The generous length of this part of the frame ensures that the riders feet clear the seat and passenger behind during pedal strokes. It also ensures the rear passenger is not too cramped up against the seat in front. The latter is also assisted with the rear carrier being positioned a little higher and offering the rear passenger a view over the top of the front seat.

All of the tubes used to construct the frame are steel mountain bike and tandem tubes. One or two of them are relatively thick walled plain gauge tubes whilst the two seat tubes are double skinned. The chain stays and seat stays are both 531 mountain bike single cranked tubes that have been further manipulated to accommodate the big rear tyre. Fillet brazed together with a variety of custom made threaded fittings and coupled with heavy duty trials bike forks, it certainly is beefy.

36 hole rims with a tandem gauge spoke and gloriously balloon like continental tyres offer comfort, traction and strength. 8 speed Shimano gearing, Stronglight chain wheels and V brakes finish off the specification with an aluminium blank filling the rear seat tube until such time it requires a seat pin and saddle.

A lot of thought and calculation ensure that cables pass carriers and all of the transmission runs freely. Everything works without interfering with anything else. Despite such great ideas and clever solutions, we knew we were going to end up with a very long bicycle that was heavy and cumbersome. It was also a concern that the rider would struggle to keep the thing upright whilst negotiating obstacles. Our project appeared successful in the workshop but it remained to be seen just how practical it might be outdoors.

Will, our family cyclist who's idea all of this was, does have the advantage of being a strong bike rider and was well aware of the problems that he may encounter from the outset. Riding the machine without the passengers in their seats is a nervous experience at first. It's turning circle is big and without any weight at the rear it behaves like one of those trolleys you get at a DIY store. You soon get the hang of it though and with a pair of children loaded into their seats, stability and steering is greatly improved.

It didn't take Will too long to get used to it. The loading of the children is of course a bit of a procedure and requires some help. It wasn't long before a hybrid mounted Sunday cyclist cruised past only to be trounced shortly after as the machine flew by at 27mph.

The weight of the machine with its two passengers on board makes it impractical to negotiate gates and stiles. You do need to have some idea of your route before you set off. Will has stuck to the trails and parks that are traffic free and the youngsters have not yet encountered any problems. However, all children can find an oily chain.  CR 

Will Wright--Concept and funding.

Tangerineted--Design and production.

Emily and Megan--Passengers.