Trailer Build June 2010

This is a project to build a decent-looking and inexpensive cargo trailer which will be pulled by a motorcycle.

More pictures on page 2.  Click on picture to enlarge.   Click again for even bigger!

I started with a Harbor Freight 1090 lb. capacity 40 1/2" X 48" Mini Utility trailer with 12" wheels.  This trailer was chosen after reading on the web about others who used this particular HF trailer to build a motorcycle cargo trailer.  Most liked the 12" wheels as compared to the other HF trailer that has 8" wheels.  As of this writing,  June 2010, the trailer has a MSRP of $259, but is often on sale for less.  I had been watching the pricing for awhile, and one weekend they put it on sale for $179 and I used one of their 20% off coupons, which brought the price down to $144.

Cargo topper
Next step is to find a cargo topper.  Sears has several to pick from and I picked the least expensive one which is 18 Cu. ft and is side opening.  Normal retail is $119 and again they had a special one weekend and I ended up paying $71 for the one Sears calls "turtle shell".  There were numerous cargo toppers on Craigslist but no one would call me back...oh well.

I began by laying out the frame portion of the trailer and then putting the bottom part of the cargo topper on it to determine how much frame to cut off to make the cargo trailer look better.  As others have done, I cut off 4 inches from the cross members (2" from each side so that some existing holes could be used) with a 10 inch miter saw.  I found a 10 inch steel cutting abrasion blade at Northern Tool for $2.   After further measuring, I cut 9-3/4 inches off of the length of the trailer, cutting from the front of the long frame members.  I have cut a fair amount of wood in my time but never have I cut steel.  I took my time, letting the blade do the work and letting the saw motor cool down every 10 minutes or so.  It took about 2 hours to make the 10 cuts (6 cuts on cross member, 2 cuts on side members and 2 cuts on the axle).  One blade was all that was needed.

After looking at other trailers put together in the same manner, I decided to paint the frame and the bottom half of the car topper the same color to enhance the look.  Since the cargo topper is hard plastic of some kind, I decided upon Krylon Fusion paint for plastic, metal, wood etc.  Using medium sanding blocks from HF (around $3 for a big pack) I scuffed all of the metal frame.  By scuffing, I mean I sanded it down so there was no gloss from the paint showing.  This should be good enough for the primer to stick to and then the Krylon Fusion.  It took 2 rattle cans of primer and 2 rattle cans of Krylon Fusion to paint the frame rails and tongue.  Preparation for painting the bottom half of the car topper consists of wiping it down with paint thinner/mineral spirits.  No primer is used on the plastic.  I used 1 1/2 rattle cans to paint the areas that will show.  Read the directions well, as multiple coats can be put on during the first 24 hours or wait 7 days to recoat.  It takes a full 7 days for the paint to reach its full strength.  I hung the frame parts from a board set between two ladders in the shade in the yard to paint.

Now it's time to weld the axle back together.  I have no experience in welding so I'm reaching out to a son that has some welding equipment at his office.  Again, as others have done, we're putting a 1" galvanized pipe in the axle frame and welding it in for additional support.  A small length of steel angle or something along those lines could be used also and might be better.  Along with welding the axle, we assembled and squared the frame and welded it together.  Others have put decking material like outdoor plywood or diamond plate on the frame, but I'm trying just welding for structural strength and to reduce weight.  Of course, I'll have to prime and repaint the weld areas.  I suppose I could have waited and painted the whole thing once assembled but was afraid I couldn't get to all the nooks and crannies.  I  ended up doing the welding on the frame myself after watching some You Tube videos.  They are some ugly welds...hopefully the welds hold but I also left the bolts in the bottom of the frame in case they don't.  I had a professional weld the axle back together.  ha

Leaf springs and bearings
I took the leaf springs apart and I'm only using the one big leaf.  This should be sufficient for the weight I intend to carry.  Next I assembled the frame, leafs, axle etc.  I installed the rear bolts that hold the leaf to the frame through a 5/8 inch heater hose to lessen the rattle of the leaf spring.
As everyone else has indicated, the bearings should be repacked.  Again, this is something I've never done.  So I took a 1 1/2  inch socket and drove the inside bearings out. There is no apparent damage from getting them out of the hub.  The outside bearing was just loose so it came out easily.  After cleaning the existing grease out with a can of spray brake cleaner, I pushed as much good grease into the bearings as I could, then reassembled the bearings into the hub and mounted the wheels.  The wheels have grease fittings to add a little more grease once assembled on the axle.

The HF trailers are 4 wire and my bike is 5 wire.  This is a common situation where the bike has separate turn and brake signals and the trailer uses one light for both brake and turn.  Standard wiring is to use the frame of the trailer for ground.  I opted to run a separate ground wire so I wouldn't have to trust a screw to metal connection at various points.  To convert the 5 wire to 4 wire I purchased a U-haul converter for $16.95. All of the wires placed into a flexible split tube purchased at Lowes for $5 and soldered all connections before taping.  The trailer came with standard bulb type lights but I decided to use a set of LED trailer lights HF had on sale for $25, which should be much brighter.  Going from the bike wiring through an isolator circuit and then to a converter can be confusing.  I made a wire chart and everything worked well the first time.

Mounting car topper
I used 4 eye bolts in the corners of the bottom of the topper to attach it to the frame of the trailer.  This seems like it will be sufficient but I may add two more bolts near the front of the topper to secure it further.  Next is assembling the rest of the topper.  Definitely takes two people to put the top on the bottom.  Then  assemble all of the other latches and hinges to hold the top open.  The std hinge holds the lid open about 30 degrees.  I may need to move the hinges back or install struts for a wider opening.  We'll see....

I really don't like the looks of the std HF square fenders.  I purchased some plastic round fenders from etrailer for $30 total including shipping.  They look much better.

Cooler rack and cooler
Others have made their own or purchased a variety of racks on the market.  I found a camp grill from Wal-mart that looks like a cooler rack for $26.  Outside dimensions of the grill/rack are 26 in. X  15 in.  Then I used a Dremel tool to cut the legs off and its ready to mount - or so I think.  Finding square u-bolts to hold the rack to the tongue is a big pain.  Looked at HF, Northern Tool, Lowes, Home no avail.  Finally found a great selection at a big Ace Hardware (Blackhawk) in Charlotte.  Each 3 inch square u-bolt was $4.25 and certainly nothing on the web is less expensive once shipping is factored in.  Trying to find a 5 day cooler to fit the rack is another huge challenge.  The physical dimensions listed on the web for Igloo and Coleman 5 day coolers is the max dimension and is not the slimmer part that fits in the rack.  More running around town didn't find exactly what I was looking for but I did find a 5 day extreme Coleman cooler on wheels for $30 at Wally world.  The more I think about it the more I think having a cooler on wheels is a good idea.  The only problem is the wheels on the cooler stick out past the rack by about 1/2 inch on each side.  No problem, just modify the rack.         
THIS is where the cooler rack portion of this project goes awry.  I decide to cut the back portion of the angled steel on the cooler rack so the cooler will fit.  Out comes the chop saw and minutes later a back portion of the rack is gone.  Then I need to clean it up a little more so out comes the Dremel tool.  Now the rack is one of a kind modified to fit the cooler.  I drill some holes through the angle for the square u bolts to hold the rack to the tongue.  In my hurry I measured the ID of the u bolts instead of center to center.  Ok so now my holes are too close together, no big deal just get a larger bit and drill the holes out.  Well this bit jammed, the drill goes flying out of my hand across the garage.  My hand is numb...did I break my hand?  After feeling returns and I determine my hand is not broken, I use the Dremel tool to finish the holes.  To steady the rack, I have it in the grass to help hold it while I finish drilling the holes with my non hurting hand.  A little grinding and it's ready for primer and paint.  I'm frustrated at this point and just want to get the rack finished so I can mount it tomorrow.  I hang it from a tree and begin priming.  In my hurry I didn't notice that the end of the rack that was in the grass is wet.  Now I'm wiping wet grass off of the just sprayed rack.  Good grief!!!!!!  The trailer has turned out great except for the cooler rack.  I'll mount it until I can find a better solution. ha

Other technical info
When hitched to the bike the trailer is angled slightly downward which is appropriate.
Trailer with topper and cooler rack weighs 155lbs.
Tongue weight before cooler and rack is 2 lbs.
Tongue weight after mounting rack is 13 lbs.  With trailer loaded tongue weight should be around 25 -35 lbs or so.  I bought a luggage scale from Amazon to check wt. for less than $8.  This scale works really well.  It has a built in indicator that stops at the weight you're measuring so you don't have to look at the dial while holding the trailer.
Wheels are stamped max speed of 55 mph.  Tire rating shows they are good for 87 mph.
I think the same bearings are used by HF in the 8 inch wheel version of their trailer.  Not sure why the wheels are marked for 55 mph max.

Total cost
Trailer                $144
Topper               $71
Paint                   $30
Fenders              $30
Led lights           $25
Cooler rack        $26
Misc                    $25

Total                  $351

Total does not include state tax or gasoline used for running around looking for stuff.

What I would have done differently.
Cut an additional 1 inch off of each side of the trailer cross bars reducing the overall width by 2 more inches.  The appearance of the car topper on the trailer would be better.
Done something different with the cooler rack.  (Sept 2010 update - the cooler rack works well and doesn't look bad, so no need to change anything)
I don't like the bicycle kick stand I'm using to hold up the tongue.  It is not very stable.  Summer 2012 - replaced the bicycle kick stand with a real jack stand that looks and works great.

September 2010 update
I've pulled the trailer for 1000 miles with no problems whatsoever.  It pulls nicely on all types of roads at various speeds.  At this point, I see no need to lengthen the tongue.  When loading the trailer, I put the heaviest stuff at the back and that has worked well in keeping the tongue weight appropriate.  Went camping last weekend with the trailer loaded to the max (guessing 125lbs) and another 35lbs for the cooler.  Total tongue weight was 40lb.  With a passenger and a total weight of a loaded trailer which weighs about 300lbs, you definitely know you're pulling something.  Total weight on bike with 2-up and gear is around 425lb, plus 300lbs for the trailer.  I've scoured the web looking for a tire pressure to weight chart to no avail.  I'm running 25lbs in the tires and that seems to work OK.

Hand injured by the drill, highlighted in an earlier paragraph, is still a little sore. 

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