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One Horsepower

March 31st, 2011 · 2 Comments

Tonight was the maiden voyage of the world’s first horse-themed three-seat bicycle. Like all great projects, it isn’t done; a mane and tail (made of wool yarn), saddlebags, and maybe a few flowers for decorative accent and better visibility are planned. But the seat, rack, and mechanical systems all cleared the rigorous engineering test of holding 100 pounds of giggling six year old, and so she was cleared for launch.

And launch she did, and successfully make the commute to and from a meeting tonight. Why a bike? The jogging stroller’s days are numbered and weight limit is fast approaching (or, um, past). We need a way to get the aforementioned six year olds to the store, plus bring home a few bags of groceries. Walking works (and we do it often), but with so many acorns and spiderwebs to look at, the pace can be slow and the cargo carrying capacity limited. How about a bicycle rated to carry 200 pounds (plus rider), with room for two seats and space for additional cargo bags to boot? And compared with a real pony, just think of the savings in hay alone!

The bicycle is a used hardtail mountain bike. Bolted to the back is an Xtracycle longtail extension. That was the easy part. The hard part was figuring out how to get the two six year olds on, safe and comfortable.

Longtail bicycles are not new, and there are lots of examples of people who have used them to carry a single adult passenger, or one or two little kids in special seats. To my knowledge, ours would be the first pair of seats designed for two six-year-olds, and we would have to do some custom engineering. Bicycles handle best when most of the weight is between the wheels (cars do the same thing, which leads to race cars with wheels as far to the front of the engine as they can get). As much as possible, both passengers needed to be in front of (or, at least, close to) the rear axle.

This is tougher than it seems. If I built two seats like chairs, there was no way for this to happen; chairs are long, and putting one behind the other would leave the back passenger flapping in the wind. So instead of seats, the pony has saddles, which are short and leave the rider’s legs to fall straight down. The two saddles can be close together…but where to put the handlebars? There’s room for the front passenger to hold a traditional handlebar (or, um, a rocking horse head). The rear passenger’s handlebars, however, end up being right beside the front passenger, and have to be attached to the side of the seat.

To lay it out, I used GIMP to manipulate a photo of the bike and kids; the photo below was taken before the Xtracycle shipped, and so the magic of computer graphics was used to pencil in the bike rack and rear wheel. The photo includes a tape measure; once everything was in place, I used the tape measure to scale distances and start building.

The majority of the pony deck is 1/2″ plywood. It’s cut based on the same template used for the official Xtracycle Flightdeck, with some extra length in both the front and the back. The horse head and tail are cut from a 2×10; it’s not as lightweight as plywood, but really – once you load up the rear of the bike with 100 pounds of passengers, will you really notice a couple more pounds of wood? The horse head is long and thick, and hardware could be used to mount it securely (and allow for future removal, if needed). Similarly, the back seat could lean against the tail and use it for support. But the front seat was a big challenge – it had to be strong enough to support the weight of one passenger leaning against it, plus another passenger holding on to the handlbars on the side of the seat. But at the same time, there was no space available for a big support to be bolted to the deck. Instead, it’s built like a box, with glued dovetail connections on all sides for rigidity.

The passengers needed a place to put their feet. Xtracycle sells footrests for the front seat, but not the back. Like some others have done, I used 3/4″ copper pipe with soldered connections to build a wrap-around footrest. The kickstand nicely rotates around the copper. A couple of screws keep the pipe from falling out of the Xtracycle.

One last accessory is a relatively inexpensive pully systems that can lift a bike for storage in the garage. This works great with the longtail; one pully attaches to the front handlebars, and another to the bridge at the back of the bike. A few pulls and the pony is safely stowed; one more, and it’s lowered and ready to use.

The goal is for the pony to be as convenient as a car, maybe more so – even if the engine has a bit less than one horsepower.

Tags: Bigger Pictures · Crafty · Dynamic Duo

2 responses so far ↓

  • 1 Sabrina // Apr 1, 2011 at 7:46 pm

    Wonderful! I am so impressed with the ingenuity!

  • 2 Grandma and Grandpa Reisdorf // Apr 2, 2011 at 8:06 pm

    Designed by a true Engineer! We really like the picture with the 2 Carmens! Happy riding! Love, Mom & Dad

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