But inevitably, children keep growing and it wasn’t long before Ira wanted to be pedalling too. Edgar’s children were beginning to outgrow their U+2 as well, so over several cups of tea and the odd pint of beer a plan was hatched to build a pair of electrically assisted child-carrying bikes to do the school run.
The Stringers Following the closure of the village school, our morning run is now a three mile trip along a busy ‘B’ road to the local market town, competing with frustrated motorists in their daily scramble to work. The school entrance traffic chaos is policed by the lollypop lady, who does a great job of separating kids on foot from irate commuters and late parents who choose to drive their little darlings as close as possible to the classroom door. Initially we used a modified tandem with added ‘kiddie-cranks’ to shuttle kids to school or play group. They both loved the adventure of clinging to the handlebars and having their little legs going nine to the dozen. When both started school we upgraded to a double trailer attachment, the ‘U-plus 2’. I had already seen two other local parents using this setup for their school run. This solution worked well for us, but the return journey was a heavy slog with no little helpers to pedal. The time and effort this required always made the car option tempting. I’d seen the Thompson ‘bike buses’ and decided to add electric-assistance to my bike, too. I bought a 250 W Heinzmann hub motor kit. Although it wasn’t fast, it made the school run quick and easy enough not to find excuses. On the bike the children and I chat (or shout) about what we see and wave to familiar faces. We are generally in high spirits despite usually being a bit on the late side. In comparison, the driving option always feels like poor quality time, with the inherent stress of finding a parking space near the school. As they outgrew the trailerbike we needed something which would allow us to keep cycling to school without risking the danger of young children on busy roads using their own bikes. So thinking caps on…
DESIGN We soon agreed that we were going to build a pair of child-back triplets to keep with the single-track format and avoid articulation. Initial design brainstorming centred around joining the front of one scrap bike to the back of another, with planks of wood to check what was the maximum length of bike which could get around the corner of the Thompson’s house. Once we had our maximum length the design was developed on the computer using simple twodimensional CAD to check essential geometry. Was the front end large enough for Edgar and the back small enough for Ira? Would all those rotating pedals avoid each other and any motorised bits? And was there room for the kids to grow? If we were going to all this trouble, it would be nice to get several years’ use out of the bikes, subject to them not becoming too ‘uncool’! This process gave us a basic shape for the frame and, using experience gained from the earlier bikes, we put together a shopping list of required bits. Cromoly mountain bike tubes were purchased
from Ceeway frame building supplies here in the UK, along with braze-ons – we bought lots to allow for changes of heart later. Components were gathered from salvaged bikes (our stock of chainsets is much diminished!) or purchased on Ebay, which just left the main frame tubes. To avoid a forest of little tubes and to preserve the clean lines of the design we needed large diameter yet thin-walled tubing to cope with the loads that we knew a triplet would impose. After some searching we sourced one 6 m length of T45 alloy steel and another of 316 stainless steel. If you are tempted to try this at home you should know that the stainless steel was significantly cheaper than T45, but it made up for it later by proving to be a whole lot harder to braze. Both bikes were built at once to allow the simple steel box section jigging to be shared during each stage of construction. As the bikes grew and space in the shed diminished it became increasingly challenging to manoeuvre around, and we both began to wonder whether the finished bikes were going to be too long to be manageable.
VELOVISION ISSUE 32 DECEMBER 2008