the danger cart - mr. demchak! · web viewthe last feature i wanted this trailer was to be able to...

Running Head: Building The Danger Cart 1

Building the Danger Cart

Michael D. Demchak

Central Connecticut State University

“Get a bicycle. You will certainly not regret it, if you live.” – Mark Twain

Building The Danger Cart 2

The 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 Trailer

Two 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' Trailer


History:

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' Trailer


This 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:

Wood 1) Availability2) Easy to work with3) Aesthetics4) Wood-working experience

1) Strength2) Weather resistance3) Intricate joints

PVC 1) Availability2) Easy to work with.3) Weather resistance4) Variety of pre-formed angles/attachments

1) Strength2) Aesthetics

Steel 1) Good availability2) I have the tools needed to work with3) Metal-working experience4) Strength

1) Weight2) Weather resistance

Aluminum

1) Low weight2) Strength3) Weather resistance

1) 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: http://www.bicycletruck.blogspot.com/. 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 Description Quantity Cost

Trailer structural

3/4” steel tubing 21 feet $50

3/4” angle iron 3 feet $8

1” steel tubing 3 feet $8

1/2 Birch Plywood 2’x4’ 2x $25

Trailer movement

20x1.5 Diamondback front wheel 2x $54

20x1.75” Maxxis Holy Roller tire 2x $40

20x1.5-2.125” Slime treated tubes

2x $15

Burley flex connector 1x $20

Burley Forged hitch 1x $22

Trailer accessories

Delta bike fork mount 1x $16

SportRack 12” Foam blocks (2) 1x $20

55 mm quick release seat post 4x $20

10” Pneumatic caster wheel 1x $15


Conclusion:

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!


References

Bicycle Trailer. (n.d.) In Wikipedia. Retrieved May 10, 2012, from

http://en.wikipedia.org/wiki/Bicycle_trailer#By_number_of_wheels

Franklin Institute 2012. Retrieved May 10, 2012 from http://www.fi.edu/learn/sci-

tech/bicycle- tech/bicycle-tech.php?cts=instrumentation

MOMBART (n.d.) In Museum of Mountain Bike Art And Technology. Retrieved May

10,2012 from http://mombat.org/Cannondale.html

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