here's a no-weld trailer i built a while ago. it's based CLOSELY on the one that's depicted in the back of Aaron Weiler's fantastic bookelet/zine, Community Bike Cart Design. the zine, more pics, and resources on diy bike trailer building are available here:
http://bikecart.pedalpeople.com/

Microcosm Publishing also sells the zine. 

here are some photos i took of the trailer i built. once the image loads, you can click on it to zoom:

the full trailer:
http://i.imgur.com/n8ZxE.jpg

the hitch, which is basically three links of normal/loop chain. one is bolted to the trailer. one is bolted to the derailleur hanger. the middle link provides the swivel in 3 axes. you can't see the chain because i covered it with inner tube to make it look a little more slick and to provide a little bit of stiffness. and yes, it's a bolt-on trailer. i wanted it to be as usable for as many types of bikes as possible, including bmx and big box types. 
http://i.imgur.com/XSSox.jpg
http://i.imgur.com/XyAhZ.jpg

the hitch arm connected to the trailer body. the bolts are standard carriage bolts, but you could use any number of nuts+bolts from a bike. i clamped the rim to the tubing where the bolts go through in orrder to both drill out the spoke holes in the rim as well as line up the tubing.  
http://i.imgur.com/VVZ3F.jpg

more hitch arm closeup:
http://i.imgur.com/nCRho.jpg

wheel connected to fork/handlebar. this is the one thing i'm not completely stoked about. if you have to replace a tube or tire, you have to unbolt the frame of the thing. for the handlebar ends, i flattened them with a hammer/anvil, and then bent them to 90 degrees in the vice. obviously you'll want to use steel bars for this. 
http://i.imgur.com/h7DH8.jpg

i've been asked about how it tracks when you ride, and i think i just lucked into getting it right the first time. my plan was to use the stems where the forks connect to adjust one wheel or the other if the tracking was off, but once it was assembled, i found that it didn't need any. your mileage may vary. 

i have a commercial trailer that i've used for cargo for a long time, and it has a floor and sides and a regular hitch that fits the one on my bike, and is much better suited for hauling cargo quickly/easily, so i didn't really use this one to haul anything other than to try it out around the block when i first built it. i did lend it to a friend for a bike move, and got good feedback from the person who used it for that. 








On Sun, May 20, 2012 at 9:24 AM, <christopher@holisticcycles.com> wrote:


I have a no weld trailer, I made it with a Tubing benders, Drill, Bolts, 1",3/4", 1/2" conduit, solid axles and stroller wheels and a little imagination. This design can be made small or big, If you ask for photos I can show you the large one is supporting 600 LBS +2-200#men 1-200# sofa sleeper. Try to stop that on a down hill!!!!

Christopher Wallace
Holistic Cycles
140 Harrison St
Oak Park, IL. 60304


-------- Original Message --------
Subject: Re: [TheThinkTank] Trailer Rental Suggestions
From: Ron Kellis <ron.kellis@velocitycoop.org>
Date: Mon, May 14, 2012 12:29 pm
To: The Think Tank <thethinktank@lists.bikecollectives.org>

If you are considering trailers that if lost won't be a deal breaker, get a copy of  The Cart Book by William L. Sullivan ISBN 0-8306-0512-6 ~ $17 Amazon or Half.com Tubing cuter ~ $20. Tubing bender ~ $40 parts ~ $30 Total investment: <$100 Cost of cart parts <$30 plus salvaged wheels and no welding. Hardest part is making the hitch. The snap components for the ones used by the Bike at Work are available from McMasters. Worst case purchase the hitch adapter from Cycletote if you can't get one made local. I have also seen threadless stems adapted. Another option is to bend out the frame and have patrons do the assembly thus assuming the risk. Using a length of 2 X 4 with a grove in it facing the floor screwed to a 2 X 2' 3/4" plywood can help to keep the bends square. I suppose you could also use two 2 X 2" pieces as a sandwich to keep the bends square, I just thought of that . . . Tubing is also bent by starting at the end/last bend though with a rectangle it doesn't matter.
 
Drop me a note if you have any questions about The Cart Book.
 
Ron

On Mon, May 14, 2012 at 2:44 PM, Jonathan Morrison <jonathan@bicyclecollective.org> wrote:
Another thing that is possible to lower the risk, is to lower the cost of the trailers -- by making your own.  The Bike at Work trailers are nice ( http://www.bikesatwork.com/bike-trailers/features.html ), but there is a pretty crazy margin in there and most community bike shops have enough fabricating ability to produce something of this quality.  If not, you would be surprised what a local welder / machine shop will do for $20.

Sincerely,

Jonathan Morrison
Executive Director
Bicycle Collective
2312 S. West Temple
Salt Lake City, UT 84115
w: 801-328-2453
c: 801-688-0183
f: 801-466-3856
www.bicyclecollective.org

The mission of the Bicycle Collective is to promote cycling as an effective and sustainable form of transportation and as a cornerstone of a cleaner, healthier, and safer society. The Collective provides refurbished bicycles and educational programs to the community, focusing on children and lower income households.



On Mon, May 14, 2012 at 12:33 PM, Jonathan Morrison <jonathan@bicyclecollective.org> wrote:
Well, I think you made it clear that your low-income customers don't have any traditional collateral (money or valuable assets) to guarantee safe return of the trailers.  I would just accept that fact -- you are going to loose some.

Given that, I would suggest one of the following:

(1) Get your money's worth first -- in time.  AKA the required number of volunteer hours they must contribute BEFORE HAND in lieu of adequate traditional collateral should generate enough actual revenue for your community shop that you could buy a new trailer.  Also that investment in time might 

(2) Give them ownership.  Make them part owner of a trailer, which means they would get a commission off future rentals.  If the trailer represents residual income, they are more likely to protect it (and turn each other in).  Obviously you want to be careful not to fund someone's drug habit or inadvertently spawn other negative behaviors just for the sake of overpriced metal and rubber.

(3) Have an easy way to recover the trailers.  Lojack systems with GPS and other things have a fundamental flaws in that these 'digital' systems require some serious battery power and footprints (too big).  However, old school 'analog' systems like those used for "Radio Tracking for Wildlife Animals" are the size of a grain of rice, have a 5 miles range, and don't need to recharge for up to 5 years.  One of our mechanics does wildlife management in the summers and used gear from Teleonics and Blue Sky.  Here are some suppliers: http://nhsbig.inhs.uiuc.edu/wes/equipment_suppliers.html

Sincerely,

Jonathan Morrison
Executive Director
Bicycle Collective
2312 S. West Temple
Salt Lake City, UT 84115
w: 801-328-2453
c: 801-688-0183
f: 801-466-3856
www.bicyclecollective.org

The mission of the Bicycle Collective is to promote cycling as an effective and sustainable form of transportation and as a cornerstone of a cleaner, healthier, and safer society. The Collective provides refurbished bicycles and educational programs to the community, focusing on children and lower income households.



On Mon, May 14, 2012 at 11:13 AM, Dan Hock <dan@bikerecycle.localmotion.org> wrote:
Hey All,

I work at Bike Recycle Vermont, a community shop specifically designed to serve the low/no income population in Burlington VT and beyond.  We get a ton of use out of our Bikes at Work trailer.  We are currently trying to design a rental program so that we can lend our trailer out to the low income customers we serve.  Our only reservations come from not being able to ensure trailers safe return.  Loss/damage is an obvious assumed risk when anything is rented out.  Generally, that risk is shared between the customer and the org, but our challenge in renting to low income customers is what acts as collateral if customers have no ID or access to money?  We are planning to offer a day-time only rental to coincide with our daily hours along with substantial locks for both the trailer and bike.  Any suggestions or models that exist elsewhere that may be helpful.  Thanks,

Dan

--
Dan Hock
Bike Recycle Vermont Program Manager
w. 802.264.9687
Bike Recycle Vermont
664 Riverside Ave. Burlington


Learn to ride a bicycle. You will not regret it if you live.
                                                                           ~Mark Twain



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