Building a Strong Flexible Bicycle Trailer Coupler

Food

Living

Outside

Play

Technology

Workshop

Building a strong flexible bicycle trailer coupler. by weblar on June 20, 2009

Table of Contents Building a strong flexible bicycle trailer coupler. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

1

Intro: Building a strong flexible bicycle trailer coupler. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

2

Step 1: Determining or building an attachment point on your bicycle frame. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

4

Step 2: Building swivel attachment. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

5

Step 3: Attach trailer swivel to bicycle trailer. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

5

Step 4: Attach trailer to coupler. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

6

Related Instructables . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

7

Advertisements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

7

Comments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

7

http://www.instructables.com/id/Building-a-strong-flexible-bicycle-trailer-coupler/

Author:weblar Intelligent tinkerer who would rather design and build exactly what I want rather than purchase something designed for the masses.

Intro: Building a strong flexible bicycle trailer coupler. This Instructable will demonstrate how to build a coupler that can be used with a variety of bicycle trailers that will turn and rotate in all possible directions: up and down, side to side, and rotate to allow the trailer to "tip" from side to side during travel. I had seen a previous Instructable that relied on a single swivel caster to allow the bike trailer to turn from side to side and move up and down vertically, but then suggested a "pipe and sleeve" sort of coupler to allow trailer rotation (tilt). Although that proposed Instructable would work as suggested, it seemed to me that, with the investment in a second swivel caster mounted on a fixed frame at a 90 degree angle to the first swivel caster, you could very easily attain flexibility in all 3 planes of motion: (1) allowing horizontal turning side to side; (2) allowing the trailer tongue to move vertically up and down; and (3) allowing the trailer to "rotate" - to "tip" from side to side. The proposed plan allows this movement in the following ways: (1) one caster wheel is trimmed flush on one side to allow it to be bolted horizontally to a point on the bicycle, and then the caster wheel frame is again reattached to the wheel, allowing the caster to turn horizontally on the bicycle mounting point; (2) the caster swivel on this first caster also allows the trailer tongue to move up and down vertically; and (3) the caster swivel on the second caster allows the trailer tongue to "rotate/tip" from side to side during travel independent of the vertical angle of the bicycle. The parts you will need for this plan are simple: (1) Two swivel casters of sufficient size - I used 2" swivel casters that are available at local hardware or home improvement stores for about $4 apiece. (2) A frame to attach these casters at right angles to each other. I purchased a heavy duty right angle galvanized construction connector (i.e., Simpson), readily available from local lumber yards or construction supply stores, also for less than $4. (3) Sufficient short bolts and locking nuts to attach the caster to this frame. I used eight 1/2" long 1/4" bolts and nylon-insert lock nuts to bolt the casters to the galvanized construction connector. (4) Appropriate hardware to attach the coupler both to your bicycle and to the trailer frame. I fabricated an extended mount on my bicycle (see step 2) that is shown as the red square tubing in the picture illustrating this step. The trailer tongue is the black section of square tubing also shown in the same picture. I used the caster wheels as described in the following steps to attach the trailer coupler to both the mounting point on the bicycle and to the bicycle trailer. (5) Though purely optional, I wanted to be able to quickly attach and detach the bicycle trailer from the bike; and therefore replaced one of the two caster wheel bolts with a similar diameter and length locking hitch pin that slips through the caster wheel bolt holes and the caster wheel bushing (see ring on top of this locking hitch pin inserted through the caster on the right side of the accompanying photo). This is also a hardware store item and should cost less than $4.

Image Notes 1. By straddling the connected trailer with the caster wheel frame, and using the caster wheel cut to fill the remaining gap of the caster frame, you can make a hitch point that doesn't pivot. 2. By attaching the caster wheel to the bike (red) so that the caster frame can still rotate around the wheel, the caster can turn around the wheel and swing up and down on the caster swivel. The caster swivel on the trailer tongue(black) allows the trailer to swivel on its vertical plane.


Image Notes 1. After cutting the caster wheel, I drilled and bolted it to a fixed piece of 3/4" X 3/4" steel that was in turn clamped to the bike frame and extends slightly past the back wheel, allowing the trailer to turn a full 180 degrees behind the bike. The caster frame is attached to the cut caster wheel with a removable hitch pin (replacing the caster wheel bolt) to facilitate easy removal of the bike trailer.

Image Notes 1. This picture shows the inside of the Simpson right angle connector and the nylon-insert lock nuts on the ends of the bolts holding the 2 casters to the outside faces of the right angle connector.

Image Notes 1. This caster, attached immediately to the bike trailer, can still rotate (and thus allow the bicycle trailer to "twist", but by using the caster frame to straddle the trailer tongue and the cut caster wheel to fill the remaining gap between the axle bolt and the trailer tongue, the caster "axle" will no longer allow turning. 2. This caster wheel was drilled and bolted to the bicycle frame extension and the caster frame attached over the wheel, and allows the caster to turn horizontally, and the caster swivel still allows the trailer to "bend" up and down.


Image Notes 1. Caster wheels can be cut and drilled to use either as fixed "blocks" to attach the caster swivel (shown) or as pivot points that allow the trailer coupler to turn.

Step 1: Determining or building an attachment point on your bicycle frame. Although many bike trailers attach to the left rear hub of the bicycle, this attachment point prohibits the trailer from turning a full 180 degrees around the rear of the bike. I have a long wheelbase recumbent bicycle that already is difficult to turn in a tight radius - I did not want a trailer coupler that was not fully flexible and would not be able to allow my bicycle trailer to turn freely behind the bicycle. In order to move the pivot point between the bicycle and the trailer to a point where it would allow the trailer to turn from side to side as far as possible, I attached a 3/4" X 3/4" length of square channel steel tubing that fastens behind the main chainwheel of the bicycle, and is firmly clamped with several coaster brake frame clamps along the left chainstay to the left rear dropout (hub), and then extends past the rear dropout past the rear tire of the bike. I painted this piece of tubing the same color as the bicycle and it remains on the bike at all times. At the very end of this piece of added tubing, before it was installed, I drilled and attached one of the two caster wheels. This caster wheel was cut flat on one side with a Dremel tool cutting wheel to facilitate its attachment to the tubing, and was drilled though vertically to allow it to be bolted to the tubing. The caster wheel frame is then attached over the caster wheel and turns around the caster wheel (much in the manner it was originally designed) and allows the trailer to turn left and right freely.

Image Notes 1. After cutting the caster wheel, I drilled and bolted it to a fixed piece of 3/4" X 3/4" steel that was in turn clamped to the bike frame and extends slightly past the back wheel, allowing the trailer to turn a full 180 degrees behind the bike. The caster frame is attached to the cut caster wheel with a removable hitch pin (replacing the caster wheel bolt) to facilitate easy removal of the bike trailer.


Step 2: Building swivel attachment. The swivel attachment itself is very simple. It consists of two 2" swivel casters that are bolted with half inch long 1/4" bolts and lock nuts to the outside faces of a right angle Simpson construction connector. You will have to drill holes in the appropriate spots in the right angle connector to match the holes in the corners of the casters.

Image Notes 1. This picture shows the inside of the Simpson right angle connector and the nylon-insert lock nuts on the ends of the bolts holding the 2 casters to the outside faces of the right angle connector.

Image Notes 1. This caster, attached immediately to the bike trailer, can still rotate (and thus allow the bicycle trailer to "twist", but by using the caster frame to straddle the trailer tongue and the cut caster wheel to fill the remaining gap between the axle bolt and the trailer tongue, the caster "axle" will no longer allow turning. 2. This caster wheel was drilled and bolted to the bicycle frame extension and the caster frame attached over the wheel, and allows the caster to turn horizontally, and the caster swivel still allows the trailer to "bend" up and down.

Step 3: Attach trailer swivel to bicycle trailer. Now you need to attach the coupler to your trailer. Here you are going to have to be "inventive" and consider the design and geometry of your trailer tongue. My trailer, constructed from the frame of a push-pull golf cart, consisted of 3/4" X 3/4" square tubing (similar to the attachment point I fabricated for my bicycle). I needed the rotational ability of the second coupler in order that the trailer could turn on its "third plane" - to be able to rotate (tip) from side to side - but decided that I didn't want the trailer to be able to turn left to right from a second joint in the coupler. So when I attached this second caster to the handle of my bike trailer, I used the wheel frame of the caster wheel to straddle the tongue of my bicycle trailer, cutting the caster wheel with a Dremel tool cutoff wheel to fill the gap between the width of the trailer tongue and the bolt hole in the caster frame for the caster wheel. Although I filled this gap tightly with the cut caster wheel and it was probably sufficiently "friction fit", I did not want to take a chance with the wheel slipping off the trailer tongue so I also drilled this second caster wheel and bolted it to the trailer tongue (you can see the bolt hole in some of the pictures of the caster wheels - I drilled a hole through the wheel in the diameter of the bolt, but then use a larger drill bit to countersink the bolt head into the wheel).

Image Notes 1. Caster wheels can be cut and drilled to use either as fixed "blocks" to attach the caster swivel (shown) or as pivot points that allow the trailer coupler to turn.


Step 4: Attach trailer to coupler. Of course, the appearance of the trailer as attached to your bicycle will vary, depending on the design of your bicycle trailer. The first two pictures depict the frame of my bicycle trailer attached to the attachment point of my recumbent bicycle, using the simple and very strong bicycle trailer coupler explained in this Instructable. To that frame, I added a large plastic tub with a locking latch lid to shelter what I am carrying in my bike trailer from the elements. In order to attach the plastic tub to the frame, I used two short sections of 1" X 3" dimension lumber that fit into the bottom of the plastic tub perpendicular to the trailer frame, attached the boards in place with Liquid Nails glue and through the bottom of the plastic tub with short wood screws, and then attached the plastic tub to the frame using 3/4" conduit clamps that bolt through through those short pieces of wood, the bottom of the plastic tub and the "ears" of the conduit clamps using 1/4" X 1 1/4" carriage bolts and nylon-insert lock nuts. I used two short pieces of board in the bottom of the plastic tub and two conduit clamps to create two attachment points for the plastic tub. I also reinforced the lid of the plastic tub using a piece of 1" x 3" dimension lumber that spans the top of the plastic tub under its lid. I glued this board in place at its ends using the Liquid Nails and a short wood screw at each end, but also used 4 small eye screws that go through the side walls of the plastic tub and into the ends of this board. These eye screws will provide anchor points for bungee cords if I were to strap items to the lid of the trailer that is reinforced by the extra 1" X 3" board attached immediately underneath the lid.

Image Notes 1. The 5 gallon bucket is NOT part of the trailer, but is here for photographic purposes ONLY. 2. The trailer coupler remains attached to the trailer when it is detached from the bicycle. 3. Two eye screws provide attachment points for bungee cords that can be used to attach additional items to the top of the plastic tub.

Image Notes 1. Two short pieces of 1" X 3" dimension lumber (one at each end of the plastic tub) provide attachment points to attach the plastic tub to the trailer frame. The plastic tub is attached by 1/4" carriage bolts through these short pieces of board to conduit clamps that attach the plastic tub to the trailer frame. 2. This piece of 1" X 3" dimension lumber reinforces the lid of the plastic tub, allowing me to use the top of the plastic tub for addtional storage.


Image Notes 1. Detail of attachment point for 1" X 3" board that reinforces the lid of the plastic tub, showing short wood screw that initially attached this board and the two eye screws that will provide anchor points for bungee cords that can be used to attach items to the top of the plastic tub.

Related Instructables

Bike rack, panniers, adventures: 4 Packs, Trailers and fun. by mikerushford

Bike trailer hitch Single wheeled bicycle trailer (Photos) by (Photos) by adamg16 camping crazy

Another Bike Trailer Improved teardrop trailer's by the (Photos) by bicycle surgeon onemoroni1 (Photos) by thunderbolts

Convert a Child's Bike Trailer into a Cargo Trailer. by bertus52x11

Advertisements

Comments 30 comments Add Comment

3366carlos says:

Mar 29, 2013. 5:34 PM REPLY

nice.

plasticorange says:

Mar 13, 2012. 3:53 PM REPLY do you have a photo of the attachment to the bike? you mentioned you have 3 separate axes ---- I assume the 3rd axis is at the attachment to the bicycle? Thanks!

billy508 says:

Aug 24, 2011. 7:20 PM REPLY

Good job. Your idea offers a effective solution to a difficult problem. Simple,Cheap, and effective. I like it Thanks.

MuggsinSD says:

May 24, 2011. 2:57 PM REPLY Weblar, I'd love pictures of how you attached this to your bicycle. I looked at your other posts and didn't see one and am not happy with most of the other ones I've seen. I love this design, and can only imagine how cool your attachment point is!!!

Salvage Steve says: VERY SLICK!


Apr 15, 2011. 11:11 AM REPLY

spark master says:

Apr 3, 2011. 7:05 AM REPLY

elegant, off the shelf parts

KWHCoaster says:

Feb 18, 2011. 9:03 AM REPLY Great idea to use what appears to be a folding golf cart for the trailer chassis & wheels. I haven't golfed in 15+ years and I have a folding golf cart in my storage locker that now can be re-purposed!

weblar says:

Feb 18, 2011. 11:03 AM REPLY

Good deal. Folding golf carts are relatively sturdy and are well-suited to make undercarriages for bicycle trailers.

BillBiker says:

Jan 22, 2011. 9:39 AM REPLY This is the 2nd I have came across by you weblar! Indeed yet another awesome 'able. I'm currently working on a project having to do with a bike trailer. I may use part of this in my project. Thanks

weblar says:

Jan 23, 2011. 6:54 PM REPLY I hope that you can make use of anything I post here on Instructables. This is a great website and I start many of my projects here, looking to see what others have invented rather than simply buying something off the shelf.

BillBiker says:

Jan 24, 2011. 5:22 AM REPLY

Yes definitely and my other half likes the idea I do not have to go buy "new stuff" lol. This site is invaluable!!!

yel3an_ha says:

Dec 4, 2010. 7:28 AM REPLY

U Could've Done It With 1 Wheel Only!!

felmont says:

Mar 7, 2010. 3:51 PM REPLY I love the design!!! Question - before I embark on building this hitch, I'm a bit sceptical about the amount of load that will be put on the the "swivel" part! Since the whole trailer will be pulled on the pivot, it will be pulling "through" one of the swivels (the swivel on the second caster, which provides the rotational movement)... Is the ball bearing mechanism and plates holding it together really strong enough to hold out over long distances and time? Seems like it might just bend and give out!! Which inclines me to use the D-bolt and eye-bolt hitch instead. See my progress so far for pics of both of my hitch ideas (second one is inspired from this page!) www.flickr.com/photos/48007949@N03/sets/72157623536962194/

weblar says:

Aug 30, 2010. 2:02 PM REPLY I do understand your concern; and perhaps my experience is reflective of the quality of the casters I bought; but I have had no separation problems at all between the ball bearing mechanism plates. I guess if you stop and think about it for a second (and I must admit, I haven't done this until now), the caster is designed for use, not just to hold its "load" off the floor and swivel when pushed, but also to withstand a fair degree of lateral force when the load is pushed around the floor. Therefore, the ball bearing mechanism/plates assembly would have to be reasonably strong to withstand those same lateral forces. In any event, I have not had any problems in actual use with separation or failure of the caster ball bearing mechanism.

weblar says:

Mar 9, 2010. 8:22 PM REPLY With some regularity, I pull loads with this trailer, probably up to 75-80 pounds at a time, on the chat-covered Katy Trail State Park here in central Missouri (US). In spite of the moderately rough surface and the amount of use, I have had no problems whatsoever with this coupler or the plates holding it together. I do occasionally lubricate (with spray lube) the ball bearings and pivot joints in the two casters to ensure free motion. I can grasp either side of the right angle building connector and cannot bend or open the angle any further - and I am a relatively strong individual. I have no real concerns with the strength or durability of this trailer coupler; and in light of the length of my recumbent bicycle and the narrow trail where I often ride, do really appreciate the wide range of motion that this coupler design allows.

bo88y says:

Aug 29, 2010. 4:13 PM REPLY These casters are designed for eccentric loading-- when used in the usual way, the caster axle is offset from the swivel axis, and these casters look like they're rated in the 200 lb. range. And while towing subjects the bearings to more jerks and shocks, I doubt you're getting anywhere close to the rated load on the bearings. The weak link, I think, is the attachment of the caster to the red square tubing, but even that seems strong enough.

bikerusl says:

Jun 25, 2010. 12:13 AM REPLY At this point you might as well go for something purpose built that will be cheaper and less work: http://www.midwestcontrol.com/catdisplay_short.php?pg=119 Use 12mm or 0.5" for heavy duty trailers (>300lbs) and you could use smaller like M10 for a more average 200lb trailer. The only problem with midwest is you have to buy bulk. Center for Appropriate Transport Eugene has these kind of hitches http://hpm.catoregon.org Also if you are in Vancouver, BC I just boult 15 of them and I don't need that many so I could sell a few to anyone interested at cost - or I am going to make a kit like HPM CAT has which has some pre-made parts (less DIY) bicyclefamily.ca


weblar says:

Jun 27, 2010. 2:27 PM REPLY Of course the problem is that you have to buy bulk........ The purpose of this website is to assist people to build what it is they need for themselves without relying on the market to "purpose build" what commercial interests decide they can sell to you for a profit. My purpose in offering my ideas and publishing these plans is to allow others who don't want to buy this item in bulk to build a perfectly acceptable alternative at a greatly reduced price. I paid less than US $25 for the parts constituting this coupler and got a much more satisfactory result than the products for which my local bicycle shop charges twice as much.

joshfromga says:

May 1, 2010. 9:49 PM REPLY hmm... i like your design. it looks effective, but i saw something on the road a few months ago that was a bit simpler and gave an additional axis of rotation for the trailor. it was an older fellow who took 2 large casters, took the wheels off, and ran a single axle through both of them. it looked like the quick mock-up below. anyways its just an ideayou can play with and see if it meets your needs.

weblar says:

May 13, 2010. 6:31 PM REPLY That's an interesting twist (no pun intended) on using casters for a bike trailer coupler. I'm not sure that you're adding an additional axis of rotation, because my design also turns/swivels/rotates on 3 separate axes. However, depending on the design of your trailer tongue and/or the point on your bicycle where you intend to attach the trailer coupler, the design you propose could allow some different attachment options.

joshfromga says:

May 22, 2010. 5:48 AM REPLY yeah, the older fellow who built it had it attached to the cargo rack over his rear wheel. he offered to sell the whole setup (minus the bike of course) for 80 dollars. didn't have the cash at the time though.

godspiral says:

Oct 2, 2009. 6:28 PM REPLY a big improvement would seem to be able to get rid of the wheel and dril the caster axel directly through the red bar. Stress is amplified the further the pivot point from the caster bearing, and its not obvious the caster will stay bolted.

weblar says:

Oct 2, 2009. 6:52 PM REPLY Though I (think I) understand your concerns, I've given the trailer coupler design plenty of use under load since I built it and it seems to be holding up quite well, with no bolt failures (can't really see how its going to come unbolted with 2-1/4" bolts with lock nuts holding them in place). Moving the caster axle slightly away from the red attachment bar allows a greater range of motion, though I agree that you shouldn't move that pivot point any further away from the attachment bar than is necessary to allow that full range of movement.

Tinworm says:

Sep 30, 2009. 1:48 PM REPLY

very clever indeed! :)

depotdevoid says:

Jun 23, 2009. 11:50 AM REPLY

Nice idea! I like the final product, and wish I still had my bike trailer to try it on!

weblar says:

Jun 23, 2009. 1:45 PM REPLY

It seems to work very well for me, and it sure was simple to put together from readily available parts.

lieuwe says:

Jun 23, 2009. 5:46 AM REPLY

heh, the commercial bike trailer i have just uses a spring-thingy with a rope as backup for when the spring fails...

weblar says:

Jun 23, 2009. 8:42 AM REPLY Yeah, I saw semi-flexible plastic sorts of couplers that the bike trailer makers offer - like that plastic won't eventually fatigue and crack over time. Swivel casters have ball bearings in the swivel joint and sleeve bearings through the wheels - they are better engineered than the junk that the bike trailer makers offer to connect their overpriced trailers to your very expensive bike. Its very easy (and in fact, less expensive) to make a trailer coupler yourself that will get the job done better than what they'll sell you for much more.


rimar2000 says:

Jun 22, 2009. 5:53 AM REPLY

Very good idea.

weblar says: Thanks. This is why I like this website - you can read other peoples' good ideas and then build upon them.


Jun 22, 2009. 9:05 AM REPLY

Building a Strong Flexible Bicycle Trailer Coupler

Recommend Documents