I have long wished I owned one of those fancy B.O.B. Yak trailers. I pedal at least a couple thousand miles a year on my bike. As much as I would love to own a Yak, I have other things I would rather spend $300+ on. This is my first instructable so bear with me if I miss anything. I tried to take photos along the way and I have missed a few at the end. The grinding and prep work for paint and the process of painting itself did not get documented. I trust most people know the steps to do that... Now on with the build!
Step 1: Parts
I used 3 10' pieces of 3/4" EMT pipe for this build and I have a little bit left over. I also bought a small section of 1/2" allthread, 4 brass bushings, and 2 locknuts for the allthread to fashion the hinge. I also picked up a 17"x21" wire basket that is used in closet organization kits. I did order the actual B.O.B Yak skewer attachment from REI.
EMT pipe $10.50
Brass bushings $10
Wire Basket $8
Skewer plus shipping $30
So for roughly $60 and a day and half of time, I think I made a good decision.
The wood piece was made as a jig of sorts that I used to help position the top and bottom pieces. I drilled 7/8 holes then cut through the center of each.
Step 2: The Plans
I found several images of the actual trailer online. Combine that with what little information I could find on actual dimensions and it's possible to draw a plan of approximately what it looks like. I just loaded the photos up on photoshop, then used a projector (InFocus IN24) to shine it on the wall. I played with the distance until the projected image was close to actual size. I then taped a few pieces of paper together and traced the outline. This turned out to be somewhat of an issue with scaling width and height properly. I ended up having to stray from th original plan because somewhere, somehow, I had a slight miscalculation when I bent the top section.
So basically, I used the tracing as the form for my bends.
Step 3: Bending the Pipe
Using my bender, I bent the sections for the top and bottom of my trailer. It was a tedious process of bending and checking against the print, then bending some more and repeat....
The last pics show the wood block and the first mock up.
Step 4: Cutting and Prepping for Brazing
The basic idea here is to cut the pipes so they fit a tightly as possible together. This will make the brazing process much easier. This is also where the pics sort of stop until the end product. I started by brazing a horizontal support in the bottom section to set the width. I then brazed the top and bottom sections together where they meet at the rear of the trailer. Then I measured and cut the 2 supports for the nose and brazed those in place.
Once I had the form set, I used a hammer on a block of wood to flatten the trailing sections where the wheel mounts. I sourced a set of dropouts from the boneyard located in the rafters of my garage. I brazed these in place, then played with the spacing until the wheel fit.
Step 5: The Steering
This is where I had some problems. The top rail sticks out a bit further than the bottom making for a iffy swivel point. I decided to bend a section of pipe and make a support to hold this hinge point a little closer to plumb. The hinge point was built with a section of emt and a brass, collared bushing brazed to either end. I used a bolt to make sure the bushing didn't deform from the heat of the torch. For the other part of this hitch, I sourced the rear section of another frame. I cut just behind the seatpost and right at the bottom bracket. In the space between the frame rails, I brazed in the other two brass bushings so the collars of these rest on the collars in the other section.
Step 6: Finishing
I cut and bent one end of the basket and cut a few sections out of the nose end to get it to fit just right. The basket is steel and I was able to braze it right to the frame. I added a Bell handlebar bag, a red reflector, and a few bungees just for the picture. I have yet to receive the skewer. It is supposed to be here in a couple days. I have hooked this to a bike and rode it up and down the street. It tracks just fine. It was a bit stiff since I didn't have the right skewer and I just pinched it between the skewer that is on the bike. I plan to add a flag and a fender as well...
Step 7: Updates and Skewer Attachement
The skewer is in and installed. I loaded up a tote and filled it with junk till I got a weight of 70lbs. Seems to handle it fine. The missus and I are planning a camping trip. We live about 25 miles from a campground and that will be a good road test me thinks...
The trailer dimensions are as follows:
Bottom frame is 24" from apex of the front bend to the rear horizontal brace and 16" wide. The top frame is 28" from apex to the bends that go down to attach to bottom frame. This is where I made my mistake and it should have been the same size as the bottom. That would have meant I wouldn't have needed to modify the swivel bracing. As for the where the wheel attaches, that can be any length as required for whatever wheel you plan to use. I just happened to have a spare 20" wheel laying around so I made that work. The height from the bottom frame to the top at the nose of the trailer is about 9". This is really close to the dimensions of the actual B.O.B Yak. The numbers I had for that was 62cm by 35cm. The length of the swivel point on a Yak is 26cm
Step 8: More on the Hitch and Pivot Points
Here are some good closeup shots of the hitch attachment and the pivot points. The skewer was $27.50 from REI including shipping cost. I used some brake parts and a couple wheel spokes to fashion the retaining system.