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After building my first bike trailer (using 12" stroller wheels with a homemade 3/8" threaded rod axle with 1/2" pipe spacer, a 1/2" plywood frame bed with a 3/4" steel conduit tow arm hitched to the rear bike basket handle with a folded bike tire secured with a hex head bolt) I wanted to explore some other designes, methods and materials.
The first was a 3/4" horizontal bend steel conduit tow arm with a caster wheel hitch.
For this instructable I wanted to try a different configuration for the swivel caster wheel and to explore the use of weatherproof and good looking PVC conduit for the tow arm. As it turns out PVC is much too flexible. Even when filled with hot melt glue it is not safe, so I abandoned the idea of using PVC beyond testing schedule 40 filled with hot melt glue. I am curently replacing the PVC with 1" steel conduit, painting the bed and adjusting the spokes.
I did not want to use a semi-trailer design but in testing the trailer with a heavy load of 20- 42", 2 by 4's it became apparent that a longer tow arm was needed and a semi-trailer design would necessary for some loads which requires 1" or better steel and not PVC.
To carry a heavy load I used 2 pieces of 1/2" plywood sheet glued together for the bed and a 5/8" firewood cart stub axle with 20" hollow hub wheels. The resulting one inch thick plywood bed is strong enough to double as a frame and the axle, bearings, wheels and tires of the firewood cart are rated for 200 lbs. It can easily carry over 300 lb. and I expect that my intended load of concrete block, cement and lumber will come close or surpass that weight.
The first was a 3/4" horizontal bend steel conduit tow arm with a caster wheel hitch.
For this instructable I wanted to try a different configuration for the swivel caster wheel and to explore the use of weatherproof and good looking PVC conduit for the tow arm. As it turns out PVC is much too flexible. Even when filled with hot melt glue it is not safe, so I abandoned the idea of using PVC beyond testing schedule 40 filled with hot melt glue. I am curently replacing the PVC with 1" steel conduit, painting the bed and adjusting the spokes.
I did not want to use a semi-trailer design but in testing the trailer with a heavy load of 20- 42", 2 by 4's it became apparent that a longer tow arm was needed and a semi-trailer design would necessary for some loads which requires 1" or better steel and not PVC.
To carry a heavy load I used 2 pieces of 1/2" plywood sheet glued together for the bed and a 5/8" firewood cart stub axle with 20" hollow hub wheels. The resulting one inch thick plywood bed is strong enough to double as a frame and the axle, bearings, wheels and tires of the firewood cart are rated for 200 lbs. It can easily carry over 300 lb. and I expect that my intended load of concrete block, cement and lumber will come close or surpass that weight.
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Signing UpStep 1Materials and tools
1. Axle, wheels and tires.
While there are many axle and wheel options I decided to use the ready made firewood cart recently on sale at Harbor Freight for $29.95. The width and strength are right and I had been looking for a 20 inch wheel with a butt or stub axle to build a recumbent tadpole in case this setup did not work out.
I could have used twenty inch bicycle wheels for the trailer if I only planed on loading groceries. The difference with using bicycle wheel axles is that the frame must surround the wheels to support the axle from both sides. There is a certain advantage in building a trailer this way, especially if you are going to be pulling your trailer through narrow passages or close to objects, walls or fences where the wheels can snag or scrape. The enclosing frame surrounds the wheel and doubles as a heavy duty fender. (You can make one of these by following this instructables.)
2. Plywood sheet
I'm using two 31" by 21" pieces of half inch plywood glued with construction adhesive and screwed together with drywall screws. The resulting one inch thick bed means an integrated frame.
3. Steel electrical conduit
Instead of PVC as shown use 1" or 1-1/4" metal conduit. 1" or better steel plumbing supply line pipe is stronger if you avoid threaded fittings and use a bender to make the angles instead.
A single three foot length of conduit is long enough for a short tow arm with enough room to clear a 26" wheel with the pivot point location shown but a five foot length will allow you to carry lumber. A stick of 10' 1" steel conduit costs about $7 and will provide enough length for two or three tow arms.
4. Steel air hose quick connector
The male part is used as a pattern for shaping the end of the carriage bolt. A quarter inch connector will require a three eighths carriage bolt to make the male fitting, while a three eights connector will require a five eighths carriage bolt. You can also add a quarter inch or three eights inch threaded pipe plug.
5. Carriage bolt
This will be used to replace the male part of the quick connector with the size depending on which size connector your get. Get one that is six or seven inches long with only an inch or so of thread. If the rounded head will not slide snuggly inside a one inch piece of PVC pipe then you will have to grind it down.
6. Caster wheel
You can get two inch caster wheels at Wal-Mart for $2.24 (12/1/2007) but the local flea market where I shop sells them for $1.
7. Adapter plate
You can use a three inch by three inch by one eighth inch or thicker piece of steel plate. This plate will be used to make the bike frame to caster wheel base plate adapter. I used a five eighths anchor bolt washer.
8. Machine screws and u-bolts
The dropout eyelets on my bike take a quarter inch, 32 pitch machine screw. You will also need four one quarter inch, 20 pitch hex head bolts that are three quarter inches long and one that is one and one half inches long to replace the caster wheel rivet axle.
The axle and tow arm are attached to the bed using 1/2", 3/4" and 1" u-bolts.
Tools
You will need a drill with a one quarter inch bit, a rotary tool with a metal cutoff wheel, hack saw, hot melt and PVC glue and a one quarter and a three eighths inch wrench. A lathe would be helpful but I used a 1/2" drill to hold and turn the bolt in place of a lathe proper and a rotary tool instead. Don't forget the micrometer. If you use a half inch drill securely mount it on your work bench to spin the carriage bolt for consistent shaping. You will need access to an assortment of other common shop tools such as a bench grinder and a 1" EMT conduit bender.
While there are many axle and wheel options I decided to use the ready made firewood cart recently on sale at Harbor Freight for $29.95. The width and strength are right and I had been looking for a 20 inch wheel with a butt or stub axle to build a recumbent tadpole in case this setup did not work out.
I could have used twenty inch bicycle wheels for the trailer if I only planed on loading groceries. The difference with using bicycle wheel axles is that the frame must surround the wheels to support the axle from both sides. There is a certain advantage in building a trailer this way, especially if you are going to be pulling your trailer through narrow passages or close to objects, walls or fences where the wheels can snag or scrape. The enclosing frame surrounds the wheel and doubles as a heavy duty fender. (You can make one of these by following this instructables.)
2. Plywood sheet
I'm using two 31" by 21" pieces of half inch plywood glued with construction adhesive and screwed together with drywall screws. The resulting one inch thick bed means an integrated frame.
3. Steel electrical conduit
Instead of PVC as shown use 1" or 1-1/4" metal conduit. 1" or better steel plumbing supply line pipe is stronger if you avoid threaded fittings and use a bender to make the angles instead.
A single three foot length of conduit is long enough for a short tow arm with enough room to clear a 26" wheel with the pivot point location shown but a five foot length will allow you to carry lumber. A stick of 10' 1" steel conduit costs about $7 and will provide enough length for two or three tow arms.
4. Steel air hose quick connector
The male part is used as a pattern for shaping the end of the carriage bolt. A quarter inch connector will require a three eighths carriage bolt to make the male fitting, while a three eights connector will require a five eighths carriage bolt. You can also add a quarter inch or three eights inch threaded pipe plug.
5. Carriage bolt
This will be used to replace the male part of the quick connector with the size depending on which size connector your get. Get one that is six or seven inches long with only an inch or so of thread. If the rounded head will not slide snuggly inside a one inch piece of PVC pipe then you will have to grind it down.
6. Caster wheel
You can get two inch caster wheels at Wal-Mart for $2.24 (12/1/2007) but the local flea market where I shop sells them for $1.
7. Adapter plate
You can use a three inch by three inch by one eighth inch or thicker piece of steel plate. This plate will be used to make the bike frame to caster wheel base plate adapter. I used a five eighths anchor bolt washer.
8. Machine screws and u-bolts
The dropout eyelets on my bike take a quarter inch, 32 pitch machine screw. You will also need four one quarter inch, 20 pitch hex head bolts that are three quarter inches long and one that is one and one half inches long to replace the caster wheel rivet axle.
The axle and tow arm are attached to the bed using 1/2", 3/4" and 1" u-bolts.
Tools
You will need a drill with a one quarter inch bit, a rotary tool with a metal cutoff wheel, hack saw, hot melt and PVC glue and a one quarter and a three eighths inch wrench. A lathe would be helpful but I used a 1/2" drill to hold and turn the bolt in place of a lathe proper and a rotary tool instead. Don't forget the micrometer. If you use a half inch drill securely mount it on your work bench to spin the carriage bolt for consistent shaping. You will need access to an assortment of other common shop tools such as a bench grinder and a 1" EMT conduit bender.
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I did have an accidental decoupling at low speed due to the coupling I used being screwed together rather than permanently press fitted, so the ball bearings could be replaced. The solution I used was to apply JB Weld on the threads and to check the coupling before and after each trip.
Although I thought about including a safety chain or cable I decided against it since it is a lot more dangerous for the rider to have the trailer attached if it becomes unstable or flips over. The picture that came to mind was the trailer dragging me over a cliff.
(somehow I could not paste the link)