The Danger Cart



Building the Danger CartMichael D. DemchakCentral Connecticut State University“Get a bicycle. You will certainly not regret it, if you live.” – Mark TwainThe Danger Cart As a long time bicycle enthusiast and environmentalist, it always pains me to drive my car. For the past few years I have lived “car-lite” never being able to truly be car-free. Although to my dislike of the internal combustion engine, I have always lived a very active and adventurous life. Because of this adventurous life, many of my toys have always needed the infamous Thule rack. A Thule rack on top of a car is like gaining access to an exclusive club. This is a club that is marred in irony. For many, a Thule rack is a way to carry your outdoor gear into the outdoors. But the very vehicle used to facilitate your access to the outdoors does a great deal of harm to the outdoors. Instead, I wanted essentially a Thule rack for my bicycle. After much thought, I settled on the idea of a trailer for my bicycle. A trailer that would transport my kayak, mountain bike, rock climbing and backpacking to hauling lumber and making dump runs all while saving money on escalating gasoline costs, helping the environment, and keeping me in good shape. Commercial options: Currently, a trailer like the above doesn't exist. Commercially available trailers are broken down to their purpose. The first purpose is a general issue cargo trailer, usually with a flatbed, a variety of tie downs that are used for a wide variety of uses. Often cargo trailers are used with plastic storage containers for containment of smaller items. The second is a single design trailer, such as; child trailers, pet trailers, kayak trailers, grocery trailers and bikepacking/touring trailers. There are a wide range of options here, however many lack versatility. Trailers also differ dramatically based upon the number of wheels. Currently on the market, there are very few one wheeled trailers; however, they have their advantages. They are usually lighter, more streamlined, better handling (able to lean), and usually able to track 180 degrees around the bicycle. The disadvantages of a one-wheeled trailer are their cargo carrying abilities.Figure 1: B.O.B TrailerTwo wheeled trailers are more popular and there’s a wide range of choices that exploit their advantages. Two wheeled trailers are able to carry more cargo (wider cargo decks, open backs and two wheels to share the load) and keep cargo level. However, they must have a more complicated hitch to allow 360 degrees of movement and don’t track as effectively. (See examples Fig. 2 and Fig 3) (“Bicycle Trailer”, n.d.)Figure 2: Tony Trailer- 'Bin Picker'Figure 3: Surly 'Bill' TrailerHistory: The history of bicycle trailers is a rather simple history with the invention of Cannondale’s ‘Bugger’ trailer in 1971. The bugger was born out of Cannondale's space located in Wilton, CT (where the company got its name after the train station it sat across from). The Bugger trailer was essentially just a big backpack on wheels. What attributed to the Buggers success, besides being the first, was that it was able to transfer all of the weight to the trailer's wheels instead of the bicycle itself. Shortly after, the buggy was equipped with various accessories that increased the capabilities of the trailer. While bicycles have been used for carrying cargo besides their human occupants, Cannondale grabs the title as the first commercially available bicycle trailer (MOMBART, n.d., para. 3).Figure 4: Cannondale 'Bugger' TrailerThis is a surprising fact given the long history of bicycles. Bicycles were for many people indispensable tool for transportation since the 1800s and were a product of so many innovations that “in the last decade of the 19th century, at least one-third of all patent applications at the U.S. Patent Office were bicycle related.” (Franklin Institute, 2012) Design Considerations: The first design consideration that I had was cargo capacity. My intended cargo was the ability to carry a kayak, my rock climbing equipment, a person and my mountain bike. To accomplish this I had to look at some previously designed trailers and decide their applicability. I wouldn’t be able to use a single wheel system because of the rear wheels central location. Because of this, the kayak would have to be above the wheel, which would raise the center of gravity too high. After the decision to use two wheels, I looked at more designs for other possibilities. When thinking of the frame, the first wrinkle was what size wheel to use. A 16” bicycle wheel is lower to the ground than a 20”. However, I was able to find many more wheels/tires/tubes that use a 20” wheel given its popular size for many BMX bicycles. Next, was how would these two wheels would be supported? Most bicycles and their wheels are supported by the use of two axles. The downside of this set-up is that the frame would have to be slightly wider by design and heavier. However, the upside is an increase in carrying capacity, and a much more time trusted and widely available selection of wheels and hubs. While a single ‘stub’ axle is very popular with modern day trailers, I wasn’t able to find many quality wheels/hubs that were affordable. After this, I thought about frame materials...Materials:Pros:Cons:Wood1) Availability2) Easy to work with3) Aesthetics4) Wood-working experience1) Strength2) Weather resistance3) Intricate jointsPVC1) Availability2) Easy to work with.3) Weather resistance4) Variety of pre-formed angles/attachments1) Strength2) AestheticsSteel1) Good availability2) I have the tools needed to work with3) Metal-working experience4) Strength1) Weight2) Weather resistanceAluminum1) Low weight2) Strength3) Weather resistance1) Cost2) Lack of experience/tools for welding3) Expense So after much deliberation, I decided upon a steel frame. There were a couple of sources for steel in my local area. Commercially, Steel and Aluminum are the two most popular options. In addition there are a wide variety of sizes in tubing. I decided on using 3/4” square tubing for its ease of use, smaller size and lighter weight. It’s located in 6 foot sections at my local Lowes for $17 per section. In addition, during high-school, I’ve made several electric scooters using steel tubing, so I have experience working with it in context of wheeled vehicles. Next, I needed to decide how much steel I would need. Thinking about the frame took quite a few hours of my life. I had never designed something quite like this, so I reverted to several designs online. My biggest resource was Pete Murrays bicycle trailer blog: . Pete Murray is a custom bicycle trailer fabricator out of the Austin Texas area. His ‘Square Style Trailer” in particular was something that immediately caught my eye. Figure 5: Pete Murray's "Square Trailer"While I wanted to change some things instantly about his trailer, it was a great launching spot for several ideas. The Square Trailer looks easy to construct, strong and utilitarian. Dimensionally I wanted something about that size. As I did many doodles and sketches, I couldn’t truly visualize the trailers size, so I went out and bought some 1x2” pine and decided to make a quick prototype. Initially, I planned on a three foot square trailer, but after cutting the wood, I soon realized that the trailer was simply a little too big for sharing the road. I later settled on a 32” version. This was the widest I felt I could get away with. So I bought three six foot sections and one three foot section of 3/4” square tubing. Procedure: After buying the steel, the first step was to make the external square of the frame. Since I wanted to make a square trailer, this made the cutting easy as all four members were all the same size. The cuts were made at 45 degree angles with a 14” cut-off saw. After the steel was cut and a slight chamfer was hand filed, the pieces were fitted with 90 degree clamps and tacked together with a small 110v MIG welder. After checking for trueness, I completed welding and then followed up with a grinder as the welds would need to be perfectly flat with the remaining tubing. Next, I measured and cut a piece of steel to fit between the frame elements. This member would sit inside the square and would hold one of the wheels axles and the plywood deck will sit on top of this element. Once cut, the member was measured with an inside measurement of 4 1/8th of an inch. The hub width of the BMX wheels were roughly measured at 4” however, because of my inability to accurately measure the hub, I added an 8th of an inch to play it safe. This tube was cut, slightly chamfered and welded. Again 90 degree clamps proved useful here as well as they ensured 90 degree angles. The next internal member proved to be a little more complicated. Firstly, I needed an arm to connect the trailer to the bicycle. This arm would house the flex connector which would connect to the forged hitch on the bicycle. The original idea was just to have two butt joints, but after completing the wood prototype, I decided that a lap joint would allow a single piece of metal to pass through. This would be much stronger and more professional. To accomplish the lap joint, I simply cut the notch out with a hacksaw for the more detailed outside cuts, then a Sawzall for the remaining interior cuts, then cleaned up the cuts with a file. I needed to accomplish two matching notches, so the interior steel tubing member would sit flush in the square frame. The members were then welded and ground to ensure flatness. The arm/internal member was left at its full six foot length and will be trimmed later. Before I put the welder away, I needed a way to hold the wheels. Bicycles typically use ‘drop outs’ to hold the wheel, yet enable removal quickly. Since my trailer isn’t as elegant as many bicycles, I simply drilled four holes in a piece of 3/4” angle iron spaced by an inch and a half between each hole. Each piece was cut out and welded to the underside of the trailer at the midpoint. Now the frame was essentially complete. Then I moved onto the plywood. I picked up two nice 2x4 foot 1/2” thick pieces of Birch plywood from Lowes. I cut the first piece of plywood to shape with a fine toothed plywood saw on my circular saw. I used an extra piece of 3/4” angle iron as a fence. After the wood was cut, I used a jigsaw to cut each radius on the corners. Then once again, put a slight chamfer on the edges. This piece would become the base of my trailer and sit in between the wheels. The second piece of plywood would become the adventure plate. This would have attachments for holding my mountain bike and kayak. This piece was cut to the same length as the base plate but a little bit narrower. The corners also received the same radius cuts and edges were chamfered. Four holes were drilled to accept 1/4” carriage bolts that would connect the base plywood to the frame. I also drilled four matching holes through both pieces of plywood along the front and rear. I next glued eight fender washers centered on each hole. This enables me to connect/release the adventure plate to/from the base. From here, I attached the fork mount to the adventure plate with two 1/4” carriage bolts. The plan is to disconnect the front wheel of my mountain bike, connect the fork to the mount then simply have the rear wheel drag behind the trailer. This will enable the lowest center of gravity as my mountain bike has 29” wheels. I needed to do some testing so I had to complete the trailer arm. After some head scratching, I decided I needed to cut down the 3/4” arm from the trailer down a few feet. From here the plan was to weld at an angle a 1” piece of square tubing over the 3/4” arm from the trailer. The main reason for this was to house the flex connector that would attach to the hitch. I found the midpoint of the trailer, then offset another mark 4 1/4” away (measured to offset the distance from the hub and the center of the hitch), then clamped a large piece of steel to guide the arm into place. From here, I angled the 1” tubing at an angle to intersect with the guide piece of steel. I generously welded the tube into place, and then ground it down to smooth out the intersection. Next, I moved on to the hardest portion of the entire build- pulling a 17 foot long sea kayak. I had various plans and ideas to accomplish this. The first idea was to mount a lazy Suzan to the adventure plate. Then have another plate with a foam block attached. A two wheeled trailer would be attached to the rear of the kayak. However, I soon realized that the lazy Suzan would only be able to swing 5” in either direction before interfering with the trailer. Back to the drawing board, I decided that a large caster wheel might enable better maneuverability just like a shopping cart. I went out to Harbor Freight and bought a nice 10” pneumatic caster wheel and mounted a piece of plywood with a foam block and two U-bolts for straps. To finish I simply attached another foam block fixed to sit right in front of the fork mount. I wanted to locate as much weight as possible to the axles instead of the hitch so both the kayak block and fork mount sit as close as possible. After this, I decided I wanted to include some wheel protectors and borrowed an idea from the ‘square trailer’ from Pete Murray. I bought some 3/4” electrical conduit and instead of buying a bender, I simply used an old mountain bike wheel and some good old-fashioned elbow grease. Conduit is a nice choice because it’s very cheap, is easy to bend, corrosion resistant and strong enough for moderate weight bearing purposes. After the bends were made, I cut out two notches using a hacksaw to facilitate a great physical connection. After removing as much as the galvanized coating as much possible, I welded it to my frame. The last feature I wanted this trailer was to be able to tow a friend or pick-up hitchhikers. Luckily, I already had a kayak seat that would work perfectly! I didn’t want the kayak to sit right on the plywood base (scratch the finish and would provide a bumpy ride), so I cut out a piece of 1” closed cell foam the exact shape of the plywood base. This looked a little ugly and raw, so I was lucky enough to have some ugly imitation grass outdoor carpet that would be perfect! I traced the base on top of the carpet and traced another line 1 1/2” away from that. This second line would fold over and under the foam giving it a clean look. I then glued the carpet to the foam using a combination of 3m spray adhesives, Gorilla Glue and a little bit of rubber cement. Weight was added to apply uniform pressure and after 12 hours of drying, the mat was complete. Next, I added four pieces of 2x8” industrial Velcro to the top side of the mat and 5 pieces to the bottom of the chair. I stuck the female (soft) Velcro to a centered location that would facilitate the rider’s weight under the axles and still provide enough legroom. Now that everything is done (wohoo!) I threw on a coat of flat black enamel and took her on the open road!Below is an itemization of the major components needed to complete the project: Item DescriptionQuantityCostTrailer structural3/4” steel tubing21 feet$503/4” angle iron3 feet$81” steel tubing3 feet$81/2 Birch Plywood 2’x4’ 2x$25Trailer movement20x1.5 Diamondback front wheel2x$5420x1.75” Maxxis Holy Roller tire2x$4020x1.5-2.125” Slime treated tubes2x$15Burley flex connector 1x$20Burley Forged hitch1x$22Trailer accessoriesDelta bike fork mount1x$16SportRack 12” Foam blocks (2)1x$2055 mm quick release seat post 4x$2010” Pneumatic caster wheel1x$15Conclusion:As a soon to be Technology Education teacher, this project was invaluable. Its applicability to my field cannot be discounted. The project has improved my ability to think critically, better manage my time, improve my tool usage abilities, better manage my workspace, a better understanding of different materials and an understanding of setbacks and failures. It’s been the largest projects I have undertaken while in the program at Central Connecticut State University and I have seen some major improvements in my abilities since entering the program. The lessons I have learned throughout this project I will take forth and pass on.. “A smart man learns from his mistakes. A wise man learns from the mistakes of others” Latin Proverb. I hope also that this will provide future cyclists/adventurers and tinkerers that there are other transportation options that can improve the world around you! So step out of your car and over a saddle!ReferencesBicycle Trailer. (n.d.) In Wikipedia. Retrieved May 10, 2012, from Institute 2012. Retrieved May 10, 2012 from (n.d.) In Museum of Mountain Bike Art And Technology. Retrieved May 10,2012 from ................
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