Step 8: Bike/Trailer Connection (The Hitch)

This was the most difficult part of the project. I scratched my head for a good week or so in trying to figure out how to connect the two before I even started this project. While I had a general idea on how to connect them, I didn't have a specific solution. I knew I would use the rear triangle of a mountain bike as I needed it to fit around the rear tire of my mountain bike.

With that in mind, here's how I made what I've come to call...The Hitch.

I originally settled on using a rear axle used for the B.O.B. Yak and Ibex trailers (what I used as inspiration) and ordered a couple online. This would allow us to switch the trailer between bikes on the trail and share the load. After they arrived, however, I realized this wouldn't be feasible as the dropouts were too small and, even after enlarging them, they still got in the way of the rear derailleur.

I also tried opening up the angle of the arms of the hitch, but that caused a reduction in the length and the wheel ended up rubbing against the frame. It's never good when that happens.

I've since packaged the axles back up and sent them back to the store.

It finally came to me when I realized I could use the braze-ons to connect the two.

As I said earlier, I cut off the rear triangle of the junker bike as close to the seat-tube as possible and used the pipe bender to bend the bottom portion of the frame so that it was similar in length to the top of the frame. A picture is worth a thousand words here. Please see below.

As you may recall, I originally had three vertical supports for the trailer. I came to the realization that it would be easier to attach the hitch to the trailer if I used the center post as the pivot point. (This appears to be similar to how the B.O.B. trailers are connected as well.)

With that in mind, I cut a length of the seat post (from the junker bike) so that it would fit between the top and bottom frames of the trailer. I then cut two notches on either end of the seat post so that it would be cradled by the top and bottom frames.

I brazed the head tube to the hitch and then slid the seat post into the seat tube. I placed the washers on top of the seat post and fit the assembly between the top and bottom frame. (The washers served as to keep debris out of the down tube as well as to take a little pressure off of the joint between the seat post and the top frame.)

Before attaching the hitch to the trailer, I finalized how to attach it to the bike. (I figured it would be easier to do this before it was attached to the trailer as grinding the hitch by itself would be much easier than grinding it with the trailer attached!) I ended up having to cut off one of the dropouts so that it didn't interfere with my derailleur. I also had to drill the braze-on hole a little larger so that the screws I was using could fit into both the hitch and my bike.

After finishing the hitch/bike connection, I attached the hitch to the trailer by tilting it and sliding the seat post so that the notches were in the center of the trailer (a hammer came in handy here). I used a pair of vise-grips to flatten the notches (again, to increase the surface area with which the brazing material can form a bond) so that they were somewhat snug against the top and bottom frames. I then brazed the top and bottom frames to the seat post (allowing the down tube to pivot around the seat post).

NOTE: Make sure you use strong screws to attach the trailer to the bike. The braze-ons aren't very large so having a screw made of zinc or copper (or other soft metal) might cause failure if the stress from the trailer causes them to sheer off. I splurged on some stainless steel screws and they worked like champs.
Ahoy me HEARTY! Going to work on my conduit trailer right now. 2 wheeler. I am going to build one like yours next. Thank you for your adventurous spirit.
First off have to say thank you for posting this trailer it is great and works. I just finished my trailer this afternoon and I took it for a 7 mile ride with 25 lbs of gear on it for the maiden run and it was on/off road and it held up great. I made a few design changes from the original and have included a few pictures to help. First I did not use a front fork for the rear tire assembly I just bent the conduit to form the rear end. I flattened the ends of the conduit and drilled a 3/8 inch hole to install the 16" tire. The front assemble was the front forks from a little princes bike which is where I also go the tire from. I included the whole neck assemble so that was the bracket to hold the top rail in place and this way could also use the original bearings to keep a very tight and smooth operating system to connect the trailer to the bike. As you can see I used a few braces for the bed of the trailer. The conduit cost $1.65 at home depot and all together the supplies cost a total of 25 dollars. I did go to Craig’s list and get the little princes bike for 7 dollars and a free mountain bike from the local bike store that was being scraped. I really love this trailer and find it very easy to tow and hardly realize it is behind me. Thanks again and hope this helps.
Clean work. Love your use of an old head tube and goose neck. Post it as a slide show. PLEASE!!!!
Great job on the trailer, it really looks good! How did you connect the trailer to your bike? I can't tell from the pictures what the hitch looks like that clearly. Could you post a picture or two of the front assembly?
Sorry for the long wait on pics been out of town will get to it this weekend and post some more details. So far it is a great trailer and have used it with 50 lbs on it and everything is going great.
 Any chance on getting the pics of the hitch?  I'm thinking about refining mine and would love to see how your did yours.
Hey there. I really like what you have done with this trailer. I am preparing to build one based on this design. Can you send me any pictures of how you attached the trailer to the bike. I think I have come up with a plan that is both simple and elegant, but I would like to see what you did too.
What about arc wielding it.
Sure. You'd probably want to use >1/8" e6011 rod. That conduit tubing is generally pretty thin stuff. Also be sure to grind off the zinc and do your welding in a place with plenty of ventilation. A respirator probably wouldn't be a bad idea either. Best of luck.
Breathing zinc can actually KILL YOU VERY EASILY. <br> <br>Please take more precautions! <br> <br>Ventilation is a MUST. <br>Having a fan blowing the dust away from you is a MUST. <br>Knowing what to look for is a MUST. <br> <br>(If you've been working with zinc like this and develop a cold, go to the hospital THEN. If you wait until it's progressed to more pneumonia-like symptoms you're dead. They can't do anything for you.) <br> <br> <br> <br>Better yet, don't use galvanized metals!
I think you did a fine job and saved a bundle of dough too. The only improvement I can think of would be to make the pivot removable (for storage, when not in use) with a extra head pipe brazed to the current one and pipes between connected with removable pins. <br>Did you paint it since you did the pictures for this instructable?
I am beginning the project of making one of these myself, I dont think I can mount directly to the frame of the bike because my bike is made of aluminum and would likely break if I were to do so. Im thinking of finding a way to mount to the rear axle but Im forseeing problems with this. Anyone have success mouinting to a rear axle? Also I have quick release....
this instructable Has an axle mount:<br><br>http://www.instructables.com/id/Bicycle-cargo-trailer--200-lb-capacity%2c-%2430-for-pa/<br><br>http://www.instructables.com/id/Bicycle-cargo-trailer--200-lb-capacity%2c-%2430-for-pa/step13/Hitch-creation/<br>
I built a similar trailer for my bike.&nbsp;&nbsp; My biggest concern was that I wanted the weight to be evenly distributed by the mounting system.&nbsp; I used an old fork to mount to the bike.&nbsp;&nbsp; I got hardened nuts that fit the back axle that had a flange on them.&nbsp; I then got thick walled round&nbsp;steel spacers that the hex of the nut fit tightly into.&nbsp; On the other end of the spacer another nut fit tightly that had the right threads for a hex head bolt.&nbsp; I welded (or you could braze) these nuts to the round spacer at both ends.&nbsp; Then I put a hex head hardened bolt through another round steel spacer whose&nbsp; outside diameter&nbsp; is the same as the fork slots.&nbsp; First you screw these on your back axle in place of your axle nuts.&nbsp; Then you screw in the hex bolts. (with a washer on the end)&nbsp; Now you&nbsp;slide the fork slots over the hex bolts.&nbsp; I drilled holes through the forks to put in quick release pins.&nbsp; They are not too big or ugly to leave on the bike at all times and it only takes two minutes to attach the trailer. I've gone hundreds of miles and had over 125 lbs on this with no problems.&nbsp; It also rides very stable this way.&nbsp; My camera is down, so I'll try to borrow one to take pics and post.&nbsp; I hope you understand my description&nbsp; as this is a fast, strong, stable way to mount your trailer.
Hey Eagle, could you explain that a bit clearer? Im trying to build my own single wheel trailer and I am having a hard time figuring out how I will mount it to the bike. I feel like it should mount to the rear axle but I cant see how that is going to happen. I imagine that where you mount the trailer at the rear axle you have to allow the trailer arms to swing up or down so that your trailer is not completely fixed on the horizontal axis. otherwise if your back bike wheel were to travel over a dip in the road it would be airborn supported by the front wheel of your bike and the back wheel of your trailer(though that is unlikely as the weight of your body would likely cause something to break or move in an unwanted way) So you see what I mean I hope, how do I overcome that problem? - mattrevesz@msn.com
that is really funny i cant amagen riding that thing
I'm inspired.<br>Knowing that you have a similar kind of skill base as I do regarding brazing and the like and then seeing the result of your efforts I feel very confident that I could recreate this excellent design.<br>Thanks a lot for posting.
How much would it cost to hire someone to do the brazing, as I don't have the equipment?
It would cost more than to buy the trailer pre made. I suggest looking at renting a welder from a local tool rental shop. Maybe look at borrowing a welder from a friend.
You might consider buying a brazing torch. You can get a torch for less than you can rent equipment. One of the off the shelf, $20 Can+Torch combos should do you fine.
How hard would it be/what changes would you have to make to add a shock to it (like a Fox float)? Do you think that wold be worth it? If things tend to rattle around a bit, would that keep more fragile things safe? I'd use mine for transporting computers around. Thanks so much for the idea!
I'd suggest putting springs in the 4 contact points (the forks and where it attaches to the bike) This could be welded or clamped, I suggest welding in reversed polarity to keep the heat off the spring.
hey can you build me one please i have looking and trying to make one but i dont know how
Take Metal Shop in school, they will teach you how to do this stuff.
just my opinion but instead of have to lean it against something, why dont you put a kickstand on the trailer? or something similar.
&nbsp;Sweet! thanks, i was trying to figure out how to attach my trailer to my bike.My first thought was the same as yours, but i looked at pictures and saw the bob trailers had a lockpin setup. So then i though of attaching it to the &nbsp;rack mount, but the drop outs were in the way, but seeing now that you did it and it worked fine ill be sure to do that tommorow! Ill send you a picture of my finished trailer if your interested, not as nice as yours but I also just rigged it together from a old bike frame and an old aluminum cot. Its strong though!
&nbsp;There's another single-wheeled trailer with a metal plate that connects to the frame. &nbsp;The hitch then connects to the metal plate. &nbsp;This looks like the best way of doing it so that you don't have to worry about grinding your cassette should the screw come loose.
if i useda 26 inch (or what ever it is) wheel for the back would that work?? its a standard size i think?<br /><br />also was wondering if it will feel liek alot on there, and up hills is it hard or good?<br />
&nbsp;Sorry about the delayed response...I must've missed this notice.<br /> <br /> Anyway, if you use a 26&quot; wheel, you'll need to adjust the fork in such a way so that the trailer is still parallel to the ground. &nbsp;While you *could* roll with a tilted trailer, running it parallel is probably better.<br /> <br /> As for going up hills, they weren't a problem as long as you had the speed, were in the right gear and didn't bonk halfway up.&nbsp;<br /> <br /> Going downhill wasn't too bad as long as you kept the bike somewhat slow for better control.<br /> <br /> The worst handling was in the mud. &nbsp;The front tire hit the mud, causing the bike to slow down. &nbsp;The trailer's momentum then pushed forward, causing a the bike to feel squishy. &nbsp;After a few times, I learned to peddle through the mud vs. coasting. &nbsp;That helped.<br />
AAAHHHH!<br /> <br /> No shop class at my school!<br />
awesome build, this is exactly the type of trailer i want to build. even unpainted it looks great. thanks for sharing, if it didnt fall apart with all you had packed on it, then id have to say you did something right, im going to start building mine today. and i want to eventually incorporate a way for it to haul a kayak on it. agian thanks for the great info on your trailer.
thanks for the kudos...how did yours come out? (like jeffreywelch's I hope!)
I wish to build a trailer too but I want to build for one task the collection of AL cans to transport to point of sale. A dual frame that is collapseable so when trailer is empty is will have a low drag. Have the system to fit the bags to make transfer at POS a breeze. Not everyone wants to be involved in this but rather than go to a gym to loose my 100 lbs I wish to do something that will pay me back with $ something that has more than one objective. I use to like to ride my bike but as a trucker the pounds have accumulated over the years I want this to change with in a year. I like your design it works well all you need to do is rig dual kick stands so you can stop your bike on the plains. Went to a police auction and bought so much bike crap it needs to be fashioned to other things. I have quite a few bikes that are ready roll they need to get cable replaced and the usual adjustments but it would not kill me to augment one for this task. I could have my good MB and factory AL trailer for grocery trips and the other home made and yackydy bike for industrial use. Great for fishing too who wants to get their food grade trailer nasty.
would it be possible to avoid all of this and use some other sort of structural support? I know that conduit is probably the most sturdy choice, but I cannot braze it because i do not have immediate access to a torch... any suggestions?
Great project! Can you drive any passenger in bike trailer, example your wife!? How kg you can drive in your trailer, max kg!?!
lol -- I don't think I'd want to carry a person back there -- for their safety and mine! When we did the C&O trip, I started with about 70 lbs or so of gear. We added some as the trip went on (offloading from the panniers due to too many flats), but we also ate/drank some of the load. I've never tested it to the point of failure, so I can't say what the max would be. I don't think I'd want to put much more than 75 lbs on it.
Great idea for a low cost trailer.With the problem with thw zinc on the condiut,you can use vinegar to remove the zinc from pipe so that you don't have to worry about the fumes.What about a floor for the trailer like the ones on other trailers?It does look it will hold up really well.Great job.
I was thinking about using a perforated metal sheet, but after seeing the price at Lowes, decided against it (it ran from $25 - $50 for what I would need). If I had some extra, I might have gone that route, but the bins do the trick (as well as keep their contents out of the elements). Thanks for the vinegar tip; I didn't know that and will have to keep it in mind.
Great Instructable! A fix for the rear wheel guard would be to braze two supports between the guard and each of the forks.<br/>An alternative for the connection to the bike would be to go up and over the rear bike wheel up to the seat post as seen on the Atomic Zombie site here: <a rel="nofollow" href="http://www.atomiczombie.com/product-cyclebully.htm">http://www.atomiczombie.com/product-cyclebully.htm</a> You could also do a U joint from the seat post from a block of metal. <br/>One last suggestion: Use a 2x6 the width of the trailer and stood on end for support of the trailer/bike so you don't have to lean it up against anything at all.<br/>
I think I'm going to stick with connection I've got now (e.g., through the braze-on points) vs. trying to jimmy rig it to connect elsewhere. As for the 2x6, that would work, but I've decided to create a trapezoid-shaped kickstand out of conduit and attach it to the first horizontal spar via a pair of hinges, if only to keep the materials in the same family.
You could make a sort of frame stand like a motor cycle.Put it near the trailer wheel and use a cable to actuate it,just stop reach down grab a handle pull to contact the frame stand to the ground and push the bike back. And an extention spring holds it up when not in use.
Your first picture in the intro shows the fork with the bend of the fork facing away from the road surface. I would turn that around so that the bend faces down and that helps put gravity in your favor. It looks like you can do that by the way you assembled it. I am working with conduit too. I use a 110 volt welder to build a seat for a recumbent I built. I suggest using a fan or working in a breeze. Wearing a welding helmet helped prevent me from inhaling any toxins, thank God.
Regarding the front fork, I tried it that way (e.g., with the fork pointing down), but it caused the trailer to ride at a funny angle. If you look in the 2nd picture in step 11, you can see how having it pointing up lends to an even trailer. In addition to the fan I had blowing across the work space, I also had both garage doors open and the side door open as well to create a good cross breeze.
Great instructions and pictures! I was thinking maybe the connection bar from a baby tow trailer might work?
Nice build. I'm looking at doing almost exactly what you've done here, keeping your building changes in mind (ie thing i would do differently next time) I'm wondering how its holding up lately? The design and support point seem to take all the directional stresses and forces into account (I'm no engineer myself) But sometimes time takes advantage and points out structural flaws. Your instructions were really good. Thanks for taking the time to share with everyone! I'm planning to do the same, but maybe on the second build after I figure out if and where it might break. Any other suggestions would be great, Again much appreciated for the share of experience and knowledge with this build. Happy trailing
I'd have to agree w/ you regarding the directional stresses (but then again, I'm no engineer either) but, so far at least, time hasn't shown any flaws. (Of course, I also haven't subjected it to anywhere near as much stress as I did on the trip.) Like I've said elsewhere, I need to work on a better connection between the bike and the trailer. A couple of nice to haves would be a stand of some sort so it can stand up on its own (vs. having to lean it -- and the bike -- against a post or something similar), a fender (to keep the top of the pack somewhat clean) and some kind of lighting for folks to better see it -- either reflective tape or real, honest to goodness lights. That and a decent paint job. Even a grey primer would look better than what it does now. ;-)
great creation and great 'structable! The whole thing looks fun to build and looks strong like a tank. One suggestion, really just something to keep in mind for projects to come, is to use triangular geometry (like the bike frame itself!) on stress points.
I was thinking of incorporating triangular geometry on the frame where ever possible. I'm not familiar enough with that to know the specifics of that subject though. Thinking back to school, I remember that there are some key "rules" to triangular geometry make it work as it should. Any suggestion as far as how this frame might be improved through geometry would be welcome! cheers
could this same shape and idea of trailer be made out of pvc??
this is super cool. im gonna talk to my dad about making one........ then ill look into any long distance trails in CA.......... i think there is one following the American River going from folsom to sac........... i dont think that is nearly as long though....... its only about 5-10 miles.,............easily done in one day..........maybe me and my dad can ride to reno or somting.........anyway nice instructable..........the trailer looks durable..........probably is if you could ride with it 184.5 miles.........nice job

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