cargo bike: steering rig

So a big part of the coolness of boson's cargo bike, for me, is the way that the handlebars turn the front wheel in order to steer. on many bakfietzen, you will see a long rod going from the bottom of an extended steerer tube to attach to a pivoting mount on the fork crown up front. it is effective, but i've always thought it was a little crude and a lot heavy. josh muir's small haul is remarkable for many reasons, but especially because of its very slick integrated cable steering. my version is slightly more complicated than josh's, but i am a sucker for pulleys. here is the basic layout:

as you can see, two brake cables are routed through pivoting barrel adjusters that are attached to the bottom of the steerer tube that the handlebars are mounted to.

here they are! next, the cable is routed through the horizontal long members of the cargo bay by a pair of pulleys:

note the cable retention nail by the first pulley. safety first, kids. after threading through the internally routed upper cargo bay members, the cables are turned around by 2 more pulleys that direct them to the clamps on the "stem" that i fabricated to mount in the steerer tube that holds the front wheel.

here you can see the forward end of the cable steering rig against the picturesque industrial trash-chic backdrop that is the alleyway to my workshop. just after i took this picture i chased away a rat the size of my shoe. moving along. here is the forward cable clamp assembly:

it is basically a quill stem style expansion plug that holds the forward t in place for the pivoting cable clamps. the clamps themselves are pretty slick too, if i say so myself. i took a pair of water bottle bosses, capped them, brazed them in the end of 1/4" tubing, drilled a lateral hole through the hole affair, and then pinch the brake cable with a set screw that threads into the water bottle boss. tidy and tight.

the cable cradles and pinch bolts at both ends pivot on salvaged derailleur pulley bushings brazed to 1/4" tubing. there it is! when you turn the handlebars, the cable pulls on one side of the t-stem up front, turning the front wheel. the cable is pulled tight over the pulleys by adding tension to the barrel adjusters at the handlebar end. 

here it is in action! from here, the only task left is to increase the range of travel that the wheels and bars have. at the moment, it is perfectly rideable in traffic, but it would be nice to have more motion possible for negotiating tight turns when storing or parking the bike. my plan is to rotate the handlebar end mounts forward by a couple of degrees to give them a longer travel. it should work out great. i will also tidy up the front end cable routing by scooting one of the forward pulleys down to prevent the cable from dragging over the other pulley on its way to the cable clamp. i am pretty pleased with how will it rides even now, and i think it will be great once i tidy up those details. i anticipate that boson will have to replace the steering cables about as often as he would ordinary brake cables, and it is easy to keep an eye on the wear on those cables as the pulleys are all exposed. 

  the bike is almost ready for paint, at this point. i still will do some work to polish up some of the brazes, make the minor adjustments to the steering, and add the panel mounting tabs that will allow me to bolt the wooden paneling to the cargo bay. almost there!