While I firmly believe that pedicab trailers are inferior to purpose built tricycle style pedicabs, trailers can be improved. My main reasons for disliking trailers is that they are more difficult to operate due to the giant hinge between the 100 to 200 pound operator and the 250 to 750 pounds of trailer and passengers, and much harder on the operators body, because the gears are not low enough. That and almost universally they don’t have additional brakes to compensate for the added weight of the passengers (100 to 600 pounds) and the trailer itself (~150 pounds).
I have determined over the last 4 years of operating and building pedicabs that the lowest gear needs to be about 12 gear inches or lower to be used long term in Austin. This is simply not possible to achieve with currently available bike parts on a standard mountain bike, but is dead simple with a tricycle style pedicab drive train.
Further I believe it is a bad business practice to rent a trailer to someone and require them to bring their own bike. (A common practice in Austin.) This shifts the responsibility of maintaining two of the major safety systems (front light and brakes) away from the company owner to the pedicab operator. Additionally, the drive trains of a tow bike, being only designed to pull the weight of one person will wear out very quickly, leaving them more problematic and less reliable. Same is true of brakes of course.
All that being said, Austin’s current proposed updates to the pedicab ordinance require disc brakes on each wheel of a trailer style pedicab. This would be a huge improvement. This requirement was implemented recently in Houston, and previously in Phoenix, AZ.
Bruce Swan of Lone Star Cyclery built a new trailer several months ago. That trailer has 2 disc brakes, one for each wheel. The brakes are actuated by a single brake lever mounted on the handle bars in the place where the rear bicycle wheel brake lever would normally go. On his setup, the rear wheel of the bicycle has no brake, but this loss of stopping power is more than made up for by the addition of brakes on his trailer.
On Bruce’s rig a single brake cable goes back to the trailer. This cable then hooks on to a loop of cable that attaches between both brake calipers. By pulling the one brake lever, this then acts on both disc brakes.
Making all of this happen can be done with mostly off-the-shelf bike parts. Starting at the front and working to the back, the following items may be helpful. Of course other options exist, but this one is fairly simple and well supported by repair parts from a bicycle shop, and bicycle mechanics that will know how to work on these types of brakes:
1 Brake lever: http://www.jbimporters.com/web/checking_product_description.php?part_number=12225
1 Brake Cable and Housing: http://www.jbimporters.com/web/checking_product_description.php?part_number=14141 and http://www.jbimporters.com/web/checking_product_description.php?part_number=14338
1 Cable stop for the end of the front brake cable. This would be welded to the pedicab trailer where it would line up well with the rear brake cable loop. : http://www.cycle-frames.com/bicycle-frame-tubing/INVESTMENT-CAST-SINGLE-CABLE-STOP.html
1 Cable straddle hooky thingy: http://store.velo-orange.com/index.php/components/brakes/grand-cru-constructeur-straddle-wire-roller-hangers.html or: http://www.amazon.com/gp/product/B001CJZC1A/ref=pd_lpo_k2_dp_sr_1?pf_rd_p=486539851&pf_rd_s=lpo-top-stripe-1&pf_rd_t=201&pf_rd_i=B0029LD7QW&pf_rd_m=ATVPDKIKX0DER&pf_rd_r=0TDBTVZFEKT0ZDK4H25R
2 x Cable adjusters to tension the rear loop of cable between the disc brake calipers. These are also welded to the trailer so that they line up well with the rear brakes: http://www.cycle-frames.com/bicycle-frame-tubing/STI-STOP-FOR-DOWNTUBE.html and http://www.bikeman.com/BR4045i.html
1 x Brake cable and 2 sections of housing to go between the rear brakes and the “cable-straddle-hooky-thingy”. The middle section of brake cable is bare, allowing the “cable straddle hooky thingy” to grab on to the rear cable loop. The two cable housing sections then guide the rear brake cable to the disc brake calipers, thus forming the rear brake loop.
2 x Disc brakes: http://www.blueskycycling.com/view_product.php?pid=39 or http://www.jbimporters.com/web/checking_product_description.php?part_number=12966 I highly recommend Avid BB7s. They are relatively inexpensive, very effective, and the brake pads last a long time.
2 x Disc brake mounts of some sort. Some thing like the following may have to be custom made, and carefully positioned for each trailer depending on the wheel drop out spacing, etc. : http://www.cycle-frames.com/bicycle-frame-tubing/STEEL-ISO-DISK-BRAKE-MOUNT.html
2 x Bicycle hubs with disc mounts: http://www.choppersus.com/store/product/820/Wide-Hub—Freewheel-Disc-BLK/ or http://www.choppersus.com/store/product/814/Front-Hub—Single-Disc-Black/ or http://www.jbimporters.com/web/checking_product_description.php?part_number=38930
2 x 36 hole rims: http://www.jbimporters.com/web/checking_product_description.php?part_number=47629 or http://www.treefortbikes.com/product/333222363790/419/Alex-DM24-20-36h-Silver.html
72 spokes of the correct length: http://www.danscomp.com/435905.php?cat=PARTS