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I was designing a cart for personal use. I live in an area with elevations on the road, and I fear braking might be an issue for the cart I have behind my bike. Can anyone suggest a good mechanism they might have experienced or seen for brakes on a cart attached on the back of a bicycle.

Also, How is there a Hitch which is flexible enough for absorbing the force during braking.

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How much mass are you hauling? –  whatsisname Oct 28 '13 at 21:29
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I think I'd just salvage a brake lever from somewhere and arrange it so the sliding-forward trailer tongue would press against the lever. –  Daniel R Hicks Oct 28 '13 at 23:33
    
I have had no issues bringing my bike to a stop while pulling my kid trailer (70lbs total) while traveling 30+ mph on a downhill. My bike has v-brakes. I have even had to do a emergency stop from 15mph and still pulled the back wheel off the ground. A bike with front and rear disc brakes should be enough. –  BPugh Oct 29 '13 at 19:33
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2 Answers 2

This site describes a prototype flexible hitch for pulling carts that includes an automatic braking system. It describes using a spring loaded rod inside an outer tube, with a segment of brake cable attached to the tube:

The simple brake cable design will make use of the force of the trailer moving towards the bike, which also moves the housing with the brake cable towards the bike. This force pushes the cable into the rod, which causes tension on the cable and engages the brakes.

enter image description here

(I believe it's ok under the CC license to republish their diagram by attributing it to the authors of the original article, Matt Ramirez, Chris Carvalho, and David Hernandez)

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As a concept not bad, but I doubt the cable would last long. Better to use a lever to provide a near straight line pull on the cable. The lever ratio can be used to control the amount to cable movement vs override. Aim for about 50mm to 100 (2-4inch) to fully apply brakes, or adjustment will be too hard and brakes will judder as the come off and on. Careful selection of lever and spring tension would be needed, and this will change with weight on trailer. –  mattnz Oct 28 '13 at 22:22
    
A lever might be superior, but makes the design more complex with more moving parts. For a homebrew design, keeping it simple is likely better than designing the optimal, yet more complicated, design. Since the cable would be protected by cable housing giving it freedom to slide, I'm not sure that it would experience undue wear from the sideways force exerted by the rod -- it's acting kind of like the straddle cable of a cantilever brake. –  Johnny Oct 29 '13 at 0:11
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You could run a long mechanical disk/v/canti- brake to the rear wheel(s). It probably wouldn't be too hard to do since you can buy housing and cable by the length.

As for making a flexible hitch, I can think of a couple options:

  • Ball hitch: Just like a car/truck hitch where you've got a ball, this will give you a smooth range of motion, but might be kind of bulky when figuring out a way to attach it to the bike.

  • Dual cotter pin: Having a horizontal joint followed by a vertical joint will give you the two major axes of movement, and it'll be simple to work on, but less range of motion.

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Thanks! Do you happen to know of any exisitng carts or trailers which have a cable attached between the bikes and cart for braking? –  user8502 Oct 28 '13 at 18:56
    
I can't really find/think of any with what I'm thinking of, but here's a link to a chart of trailers (denotes ones with brakes): twowheelingtots.com/bike-trailer-comparisons –  Aaron Oct 28 '13 at 19:27
    
All those trailers listed in that chart don't have "trailer brakes" on them. They are either parking brakes or jogging brakes. Either way the ones with the most bicycle like brakes will have the cable running up to the jogging handle. That cable will have to be re-routed. –  BPugh Oct 29 '13 at 19:26
    
As for a hitch goes, I suggest using the Burley hitch. I replaced the hitch on my non-Burley child trailer with one and it is doing very well. I have bent it around many ways over the years and it is showing no signs of failure. It doesn't have a tugging effect like some that uses a spring for flexibilty –  BPugh Oct 29 '13 at 19:29
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