Ok, finally finished with the Harbor Freight trailer project. Here's a write up that I mentioned I'd post.
EDIT: All of the links in this thread broke so I've tried to fix it after several JF members have sent PMs asking about the pix. Due to a move to a new computer a couple years ago I lost some of the original images. I've attempted to recreate some by modeling up the trailer frame in 3D and reconstructing other images. I hope it is enough to help clarify the thread again.
Harbor Freight Folding Trailer Project
1) Vehicle Setup
2) Overview / Performance Review
3) Assembly / Fabrication Process
1) VEHICLE SETUP BEFORE INSTALL
The trailer can be used with a stock Jeep provided it has the following:
- trailer receiver and 1 7/8" tow ball
- 4-wire flat plug trailer wiring harness
2) OVERVIEW / PERFORMANCE REVIEW
The Harbor Freight folding trailer is a light-duty, bolt-together utility trailer with a 1,450 lb. GVWR rating. With the trailer weight itself around 275 lb. this yeilds a usable cargo limit of 1,175 lb. While not great this trailer does offer several benefits to the Wrangler owner:
- Improved cargo volume capacity
- Compact storage solution when not in use
- Relatively inexpensive cost.
With some modifications this becomes a good (not great but good) compact trailer kit at budget prices.
Improved Cargo Volume:
The primary benefit seen in the Harbor Freight trailer is the ability for the Jeep owner to carry things such as 4x8 sheets of plywood, lumber, yard debris, general junk, an ATV or motorbike, or other bulky items that cannot otherwise fit inside the Jeep.
The load weight capacity of the trailer is not great and at 1,175 lb. for the kit with the 12" wheels it's slightly more than half the Wrangler's rated towing capacity of 2000 lb.. The actual total capacity one gives up when getting the Harbor Freight trailer is approximately 475 lb. when compared to a typical 2000 lb. GVWR rated utility trailer with a load capacity of 1650 lb.
For home owners short on storage space the trailer can fold up and store in 1/6th the area of an equivalent 4x8 utility trailer. Unfolded the trailer measures approximately 12 ft long x 5.25 ft wide. Folding reduces the foot print to a 2 ft x 5.25ft area. With the modifications made to the trailer, it can be folded up in a matter of 2-3 minutes without tools. The trailer also features built-in "feet" and casters so it can be rolled into storage once folded.
Typicall the trailer kit sells for $300 from Harbor Freight Tools. However, it occasionally goes on sale for $240 which was the price the author acquired it for. This price gets you a rolling, street-legal trailer chassis and includes:
- all frame steel
- std 1" bearings / hubs
- hitch and safety chaings
- grade 8.8 metric hardware w/ nyloc nuts
- wiring and lights
- complete instructions
- VIN plate number
- manufacturer's certificate
What it does NOT get you is the plywood deck, deck hardware, receiver mount and ball hitch, trailer receiver (steel bar on tow vehicle), license and registration, ratchet straps, tarps, bungee cords, or any "extras" you might want to add (which the author did, more later).
All told the cost nearly doubles when everything else is factored in. Still economical, but not the best $$$ : GVWR ratio.
Some places sell axle upgrade kits (hubs, axles, wheels, etc.) but these can end up costing close to the cost of the entire trailer kit and are not a good "value" in this author's opinion. If you want a stronger trailer, get a pre-made, fully-welded trailer for $600-700 dolars. If you want a cheap(er) trailer that can fold up, get this one.
Extras and Modifications:
The trailer kit is "fine" as-is from Harbor Freight and likely to offer good service. However, after looking the kit over prior to purchase it was felt that some modifications would go a long way to make this a better trailer. They are:
- welding the frame
- improve hinges
- devise tool-less folding process
- add tie-down points
- add latches for fold-up storage
Usage / Foldability:
The trailer tracked down the highway in a very controled manner with minimal bouncing and hopping when empty. Qutie surprising since the springs are stiff. With a load the Jeep had no problem towing and again the trailer tracked nicely with only the roughest bumps to cause a slight hop. Given the stiff suspension, it's not certain adding shocks would do much good.
Folding the trailer was a snap once the modifications were made. Just undo the latches, fold the rear section over the front, un-couple the hitch and tilt the trailer onto its casters, then remove two pins and fold the tongue down. That's it. Total time: 2-3 minutes. Without the latch modification a pair of wrenches are required to undo four bolts, two on each side, that secure the rear section in the down position. Getting the wrenches and unbolting everything could add another 10-15 minutes on each end of a towing operation.
Not surprisingly there was some rattling from the folding chassis. It was difficult to eliminate all rattles in such a cheap kit. However, most of them are coming from 2 locations, one is the receiver mount that fits into the tow bar on my Jeep. The tolerances are a bit loose here but it "works". The other point is the attachement for the trailer tongue. The tongue mounts in four places: two bolts that act as the hinge pivot points and two hitchpins with sping clip retainers that can be quickly popped in or out for folding. Again, this is due to the tolerances. Perhaps some sticky sided foam/rubber might quiet this down. Or just live with the noise, which happens only over rough patches of road.
Since I originally posted this build thread I've used the little HF trailer quite a bit over the last 4 years. There have been several hauls made with the trailer maxed out on weight and it's come through just fine. This includes a full loads of concrete form panels, crushed rock, concrete chunks, dirt, old sod, and lots of construction debris. I try to carefully calculate the weight of the load and then not exceed the 55mph posted limit when it's maxed out. For lighter loads I have no issues traveling at 60mph. So far the trailer is in excellent mechanical condition.
The Harbor Freight folding trailer is an acceptable, light duty utility trailer which lives up to its price point well. It offers a rather complete rolling chassis, instructions and documentation need to get it street licensed. When needed it can haul bulky cargo and fold up for compact storage when finished with the hauling task. Just don't expect world class performance from this model and keep in mind that no amount of modification can overcome the basic load limitations of the trailer. The author views it as a good pre-cut weld-together trailer kit.
3) ASSEMBLY / FABRICATION PROCESS
For the "normal" kit assembly everything is straight forward and the instructions are surprisingly clear and well written. However, for some of the above modification some extra steps were taken.
Preping the Steel:
Loosely fit the frame steel pieces together. Start with the main front section. Observe where welding will be done and grind the paint off to bare steel within 1" surrounding these areas (Fig 3). While the grinder is out knock down the sharp corners of the spring mounts, and other tabs and sharp edges (Fig 3). This will make it safer to manipulate.
Bolt First, True Frame, Then Weld:
Next, bolt the front frame section together with the supplied hardware to hold it while welding. Losely attach it until all the pieces are in then start snugging things down. Before welding the pieces make sure the frame is trued up and square by checking diagonal measurements (fig 1). If the diagonals measure out the same then the frame is square. If not, keep adjusting until they are equal.
Once things are true, start tack welding pieces together to keep the frame from shifting. Next go back and finish welding the connections. Once the front section is done fit the tongue pieces into place after grinding and prepping the steel), again keeping things loosely bolted together (Fig 2). And again the typical snug-the-bolt-down, tack weld, then weld procedure.
Fig. 1 - Square up the frame by measuring diagonally across each section.
Fig. 2 - Fit tongue to the front frame section before welding
to ensure proper fitment, the legs of the tongue need to be set
with in close tolerance to the sides of the frame.
Fig. 3 - Frame modification details showing prepped steel,
rounded corners on tabs, and welded connections.
The procedure is the same for the three primary frame sections: the front frame comprising the square frame spring perches, and caster feet, the rear frame which is a basic square, and the tongue.
Fig 4. - Ultimately, both frame sections need to be square. And the
tongue legs adjusted in or out for good fit before everything is welded.
The stock hinges are functional but flimsy. They are cheap stamped pieces of sheet metal with a bolt and nut as the hinge pin and operate in a single-shear application. The big concern was the poor tolerance of the hinge and it's single-shear nature and how this might work against the bolt holding it all together.
After being unable to located a pre-made hinge thin enough and of the proper design, the proposed alternative (Fig 5) was to fabricate a new hinge with a double-shear design that places minimal stress on the bolt. However, there were a number of factors that needed to be accounted for. There needed to be enough clearance so that when the trailer folds it does not bind up on the decking, it needs to be strong, preferably of higher tolerance, it needed to accomodate the width of a sheet of plywood, and finally it needed to be buildable by the author's skills and home equipment.
Fig. 5 - Sketch of stock and proposed hinge. Note the
distance from frame to hinge centerline is 1". This allows plenty of
clearance for the 3/4" plywood deck and carriage bolt heads.
The main body of the hinge was constructed out of 1 1/2" steel flat stock in 1/4" and 1/8" thicknesses. One side of the hinge was a basic 1/4" thick piece. It's shape was determined by careful measurement with a carboard template against the trailer. The other side was made of a shorter 1/4" piece sandwiched by two 1/8" pieces with about 1/4" of space to allow for some over exension of the hinge if needed (180* + of movement). The pieces were cut to length fist, the centers of the pin holes were found and marked with a punch and then drilled on a drill press to fit a 1/2" O.D spacer with a 3/8" I.D. opening found at the local home improvement store in their specialty hardware department. Next the corners were rounded off. The spacer was then inserted and all the pieces loose fit and clamped together. Finally, the 1/8" ears were welded to the shorter 1/4" piece (Fig 6). The spacer was cut to fit just slightly longer than the hinge assembly was wide. A 3/8" x 1.25" bolt, washers, and nylock nut sandwiched the spacer (now hinge pin) in the hinge assembly. By making the spacer slightly longer than the hinge was thick the bolt could be properly torqued down without binding the actual hinge. All radial load is taken up by the steel spacer. The bolts sees very little force at all and simply keeps the pin from slipping out. While the hinge looked crude, the tolerances were very tight and surprised the author.
Fig. 6 - Modified hinge assembly and components
Finally, the hinges needed to be welded to the frame section. Careful fitment of the frame pieces together and some steel spacers and clamps kept things in place until the pieces could be tack welded.
Note: it is of particular importance to get the proper spacing on the ENTIRE hinge assembly so that the trailer can accept a 4x8 sheet of plywood flat on its deck. That is, the bolt head, washer and hinge face need to have approximately 48 3/8" of clearance between each side. This required building up the hinge mounting location with steel shims and welding the whole she-bang together.
Given the pain in the neck nature of fabricating hinges, if I were do do this project over again I might just pick up some heavy duty gate hinges and welded them between the two frame sections. The center of the barrel of the hinges would need to stick up above the trailer deck slightly, about 1/8" - 1/4", but that might be an acceptable trade off for an easier and more accurate hinge assembly.
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