Project West: Part 5 – Pimp My Trailer

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Now we come to the part of the project where the cherry gets put on top. All the dirty and nitty gritty stuff is done and there needs to be something that really takes what is a bit of a humdrum trailer and makes it truly something unique and different. 

Easytrailer/Harbor freight folding Trailer reassembled and about to go for registration inspection.
Easytrailer (Harbor Freight) folding trailer, having had rust fixed and repainted

There is a fine balancing act between spending money on what is worth replacing and upgrading, and just potentially buying something better for equivalent money. What holds that statement back from being true when applied to this particular model of utility trailer is that there really is no equivalent new trailer available on the market, Easytrailer and Harbor Freight have this market to themselves it would seem. There is no ‘premium’ manufacturer of folding trailers, and why would there be? These little red trailers are incredibly cheap to begin with, trying to make an up-market version would most likely prove to not be financially viable for a manufacture, this being based purely on the purchase price. As a result with nothing ‘better’ to spend money on in place of an Easytrailer, it can definitely be made better!

The fact that this trailer is cheap, and nasty (in some places) doesn’t discourage people from improving upon what comes from the factory. Instead, they see the potential in what is a good base to work with, something to be built upon and this is exactly the way I am choosing to look at it also. While I’m not going to go crazy with modifications, effort would instead be focused on what will improve the quality, strength and durability for this specific trailer and its intended use.

In fact, it is popular in North America to take the cheap as chips Harbor Freight trailer and turn them into something epic! There are heaps of write ups about upgrades and modifications for turning these folding trailers into something more capable. 

Popular mods include, turning the flat-top trailer into a tear drop camper, or maybe putting the tub from a Jeep onto the frame so as to have a trailer that matches the Jeep that is towing it. However, some of the most simple and popular mods are those to increase the strength of the drawbar and frame, most will even go so far as to remove the folding functionality all together, turning it into a fully ridged tilt trailer better suited to loading motorcycles. There’s also the trend of replacing the tiny standard rims with massive off-road wheels and tyres for the purpose of, you guessed it, taking it off road. 

For weeks, there was plenty of elbow grease and hard work put in, taking this rust bucket and returning it to a state close to what it looked coming from the factory. This next stage was to take it beyond the factory and to a standard that reflects my design ideas and practical needs.

Alloy Wheels

A decent set of rims can make or break the look any vehicle, be that a car, bike or in this case a trailer. Often the difference between an alright looking [insert vehicle here] and a great looking one is what wheels its rolling on. It can be tricky picking something suitable that goes with the look and feel of what the wheels are being bolted onto and obviously like with anything, it’s easy to go overboard, ending up with something that is well executed but done with horrible taste.

Back in part 2 of the series, the original 12-inch steel rims where taken off the trailer and given a thorough clean. They were caked in dirt, mud and all sorts of other gunk and when all this crap was washed off using a specialty wheel cleaner, not only did it rinse off all the baked on road muck but also some of the white paint was also washed down the drain. Despite this good clean, these wheels were looking flat, dull and drab. Given the age of the trailer and exposure to direct sun, the paint had been damaged by UV and was breaking down. They obviously weren’t looking in the best shape, hence it was the perfect excuse to put new set of alloy rims on to improve its overall look.

Wheels off the trailer drying out in the sun having been thoroughly cleaned to remove built up dirt.
Original 12-inch steel having been wheels washed and cleaned.

However, putting a different, larger set of wheels on the Easytrailer did serve a function of more than just looks and flexing. As the trailer is predominantly going to being used for trundling up and down the high-way and at high-way speeds, the small diameter wheels were going to have to work harder to keep up with the speed of the tow vehicle. Simply put, smaller diameter wheels must turn more times (high RPM) than an equivalent larger diameter wheel would at the same speed (low RPM). By putting larger wheels on, it would result in is less friction on bearings and hubs and, in theory, prolong the life span of these components. Along with this, larger diameter wheels have less rolling resistance, beneficial for the vehicle doing the towing, especially over long distances as is intended.

At the time, the plan was to simply replace the 12-inch Sunraysia wheels with a larger wheel and tyre combo. Increasing the wheels rolling diameter and hence reducing wear on the bearings and reduce rolling resistance while being towed. 

Comparison of sizing between one the 16 inch alloy wheels and the original 12 inch steel wheel that are on the Easytrailer (Harbor Freight) folding utility trailer.
Comparison of size of the 16-inch alloy wheel and the original 12-inch steel wheel.

The used 16-inch no-name brand alloy wheels were bought on eBay for not too much cash at all. The no name, 8 spoke, alloy wheels were originally on a Ford Festiva and had the required 4×100 stud pattern (same as the hub of the trailer) and came wrapped in no name 195/50/16 rubber, still with plenty of tread left. While not in the best of shape, with various dents, scratches, and plenty of curb rash, they are perfectly suitable for use on the trailer, the two wheels which were in the best condition with the least damaged were picked out of the set, the remaining two being kept as spares (in case I feel like making another trailer in future).    

However, there was some unexpected trouble when trying to get the wheels on the trailer. Having the correct stud pattern is one thing, having a hub that can take big alloy wheels is quite another. What I had failed to consider was the center bore diameter of the wheel and if it would fit the center bore on the hub of the trailer. Which it didn’t. Hence new hubs were required to get these new dope wheels to fit on the trailer.

Hubs and Axle

The initial assumption was that changing over the old wheels with nice big alloy wheels was going to be straight forward and simple. However, in the real world, things don’t always happen as simply as we would wish them to.

While the ‘new’ rims have the same 4×100 stud pattern as the original 12-inch wheels, trying to fit them to existing hardware presented two problems which prevented this being a quick and simple switch-a-roo. 

Leaf springs removed from the axle.
Original axle, hubs and wheels

Firstly, as was just mentioned briefly before, was the centre bore of the standard hubs: while the stud pattern was the same, the centre bore on the hub was a tiny bit larger than the centre bore of the alloy wheels. As a result, the big rims could not fit over the existing hubs, if the centre bore of the alloys were but 2 or 3mm more in diameter it would have fit. A possible solution that was being tossed around was to take to the centre bore of the wheel with a half round file, opening it up just enough for it to fit. As this would have been a hack job to say the least it was decided not to pursue this option.

The second obstacle to using the standard trailer hardware was the sheer size of the new rims, as these were considerably wider, 195mm compared to 115mm, and along with their 30mm positive offset, it meant the axle was going to be too short to accommodate for this extra width meaning the inside of the rim would not clear the trailers frame by several centimetres.

Comparison between the original square axle (below) and the replacement heavy duty, round axle (top). This is a good representation of the added length on the new axle to accommodate for the extra width of the wide alloy wheels.
Comparison between the original square axle (below) and the replacement heavy duty, round axle (top). This is a good representation of the added length on the new axle to accommodate for the extra width of the wide alloy wheels.

What all this meant was to get the wheels fitting properly on the trailer both the hubs and the axle had to be replaced. The hubs with a variant featuring a smaller diameter centre bore and the axle with something at least 150mm longer in length over standard.

All the replacement parts required, axle and hubs along with bearings, were off the shelf items and were not required to be specially manufactured or modified in any way for them to fit the trailer. As the sizing was so much more different from that of the standard parts, none of the original hardware (axle, hubs or bearings) could be reused for the purpose. All the drive-train componentry was replaced and is brand new. 

The new 4x100 hubs, along with bearings, and dust seals. All necessary for fitting of the new aftermarket alloy wheels.
The new 4×100 hubs, along with bearings, and dust seals. All necessary for fitting of the new aftermarket alloy wheels.

The replacement hubs are simple cast steel, rated at 650kg load capacity, with a 53mm boss and a 4×100 stud pattern (same as standard) to suit the rims. To go along with the new hubs there was also a new set of bearings (outer and inner), along with seals and dust caps. This proved a timely upgrade as was later discovered as the existing bearings on the trailer were pretty much dead and needed to be replaced anyway. By putting new bearings in while doing the hubs it turned out to be two birds with one stone. 

As the axle was not long enough, this could only be resolved by replacing the original 1440mm axle with something longer, in this case a 1605mm axle provided enough length for the extra width of the new rims. Not only this, but it was too good an opportunity to pass up replacing the ‘light duty’ square axle with something that could handle more weight, hence the replacement axle selected is a heavy duty, round axle capable of handling heavier loads. How much more? To be perfectly honest I’m not sure, but if sheer weight is anything to go by, as the new axle is significantly beefier than the standard, it will be a decent amount more.

Once hubs, axle and bearing were all sourced, it was a case of putting all the pieces together with the bearings going into the hubs and then the hubs being slid over the stub axles of the new longer axle. Personally, I had never put together a hub like this before, but the assembly process was straight forward, even though at times the bearings needed some encouragement with a hammer to get into the hubs, it was still easy enough to get everything together.

the factory setup of the standard square axle, mounted underneath the leaf springs.New suspension setup of the heavy duty round axle, mounted on top of the leaf springs.
Comparison between the original overslung square axle (left) and the new underslung round axle

One slight difference with this new axle configuration is the change to being underslung, with the axle itself being held in place on top off the springs, as opposed to the standard arrangement which had the square axle overslung and underneath the springs. 

The reason for the change was to do with the diameter of the new 16-inch alloy wheels versus the standard 12-inch steel rims. As the alloys are so much taller, it meant the centre of the wheels are higher compared to that of the original steel wheels. If the suspensions setup was to remain in an overslung configuration the trailer would have been raised up higher and had a server rake angle, with the front being much lower than the rear. By moving the axle to an underslung position, on top of the springs, it is almost parallel to the road surface. There is still unfortunately a small amount of rake angle when hitched to the tow vehicle but is only minor. 

One possible way to correct the unlevelled platform would be to use lowering blocks in-between the springs and axles. This would definitely be the easiest and simplest solution to the problem, but due to the Easytrailer design this is not possible as there would not be enough space left for suspension travel. As the trailer currently sits there is only approximately one inch worth of travel for the suspension to move before it hits the bottom of the frame, meaning there is no room for lowering blocks without serious modifications to underside of the frame. The only alternative solution to this would be to use a drop axle, however isn’t a simple solution and would most likely require something to be custom fabricated. Maybe in the future this could happen but for the time being the new longer axle being underslung is a practice and workable solution.  

Axle Spring Seats

As you will have just read, the original square axle was replaced with a nice, shiny, new, round axle as part of the upgraded wheels and subsequent hub replacements. The axle having to be upgraded as a matter of course as the length on the original wasn’t enough to accommodate the width of the new wheels.

Axle spring seat as designed and modelled with Fusion 360
Axle spring seat as designed and modelled with Fusion 360

However, one adaptation that needed to be considered, when changing from a square to round axle, was how to mount and hold in place the axle onto the existing leaf springs, this came with its own challenging set of problems to overcome. 

When using a square axle, it has a nice flat surface for the leaf spring suspension to be seated on, not only this but the flat surface had a predetermined hole being used as a positioning guide for where the axle needed to be seated upon the leaf springs. This meant the head of the bolt going through all the individual leaf springs and holding them together, had a place to be recessed into, holding the axle in place while on the springs. 

A detailed angle of the 3D printed, axle spring seat to be used with the new round axle on the Easytrailer/Harbor Freight folding
A detailed angle of the 3D printed, axle spring seat to be used with the new round axle.

Unfortunately, this positioning hole does not exist on the new round axle and trying to balance a round axle on top of a bolt head is an impossible task, effecting the geometry of the suspension. Not only this but it is dangerous, as the axle isn’t really being held securely in position by anything other than U-bolts, having the potential to slide of the bolt head and move around on the spring.

The designed solution was a set of leaf spring axle seats, these would keep the round axle in place by matching its round profile and utilising the bolt head in the leaf spring to hold everything in a stationary position. The design is relatively simple, essentially being a solid block with a semicircular section cut out on top for the axle to sit in, and then a slightly curved bottom surface to match the profile of the arc of the leaf springs. On this curved bottom surface is the positioning hole for the bolt head of the leaf springs, holding the axle stationary and in place.

3D printed axle spring seat, for use on Harbor freight folding trailer, on printer bed having just completed being printed using Tevo Tarantula
3D printed axle spring seat on printer bed having just completed being printed.

Usually leaf spring axle seats are manufactured from steel and then welded into place on the axle itself. This axle seat has been 3D printed in PETG (Polyethylene terephthalate glycol). The material has a flexibility and shock absorbing characteristic meaning it can handle bumps and impacts without being damaged or deformed. 

Axle spring seat mounted onto new round axle for Easytrailer (Harbor Freight) folding utility trailer, shown from hub looking inwards with trailer folded out and on the ground.
Axle spring seat mounted under the new round axle, shown from hub looking inwards with trailer folded out and on the ground.

Thankfully the 3D printed axle spring seat works as well as could be intended for holding the new axle securely in place while mounted on top the leaf spring. It stops any potential movement caused by the round axle sitting directly on top of the flat leaf spring, therefore keeping the axle lined up and squared to the trailer.

Mud Guards

As a result of the increased wheel and tyre combo, the standard mud guards, that are designed for a 12-inch rim, were woefully too small to cover the new 16-inch wheels. Not only were they too small, but the quality of the original guards were just plain rubbish. Made from the most cheap and nasty steel, the quality left much to be desired. There weren’t even any welds in the corners to strengthen the part. What resulted was a guard that was floppy and would vibrate, bend and flex constantly while being towed. 

condition of fenders as taken off and after a minor clean
condition of original mud guards as purchased

Quality of the original guards aside, the most pressing problem still the size. In order to accommodate for the larger wheels, custom guards had to designed and manufactured. It was a great opportunity to upgrade the existing part to something that was not only big enough to cover the new wheels but also something that wasn’t a cheap, piece of crap.

3D Render of the custom guard for the Easytrailer (Harbor Freight) folding utility trailer
3D Render of the custom guard

The new guards are based heavily on the original guards that came with the trailer and are a simply a scaled-up version of these factory fenders albeit large enough to entirely cover the big alloy wheels. It has a four-sided profile with a flat, horizontal top, two sloped surfaces going down at 45 degrees and a single vertical surface that extends down to the centre line of the wheels on the rear of the guard acting as a mud flap. On this ‘mud flap’ surface there is allowances for attaching additional rubber should the need arise for extending the mud flap in the future, but at the time of publishing it is felt there is no need as the vertical section of the guard works well for the purpose.

Custom designed and manufactured, aluminium mud guard going on the road side of the Easytrailer (Harbor Freight) folding utility trailer. Curb side guard in background. Both have been lightly sanded and are shown prior to being etch primed and painted.
Custom designed and manufactured mud guard, shown folded and unpainted.

Longitudinally along each side there is a lip, folded at 90 degrees to the surface of the main body. The lip on either side is at a different depth, on the outside face the lip is 30mm deep whereas the opposite lip on the inside is double this at 60mm. The reason for the inside lip being deeper was for allowing enough material for a point of attachment for the mounting brackets to hold the guard onto the trailer. 

There are six holes, two at the front, two in the middle and two at the rear all of which are for the purposes of mounting the guards to the trailer frame, with each hole being 11mm in diameter allowing for use of M10 nuts and bolts. The intention is only to use the centre two bolt holes, copying the standard mud guard mounting setup, the additional fixing points at the front and rear were included as a ‘just in case’ design option. That being, should the need arise for additional mounting points, could be utilised for extra support.

Custom aluminium mud guard compared to original off easytrailer (harbor freight) folding utility trailer.
Custom aluminium mud guard (top) compared to original from trailer (bottom)

Material used for the remade guards is 2mm, 5052 aluminium chequer plate. The basic shape was laser cut and then folded on a hydraulic press to the required shape. Each corner has been welded to improve the overall strength and rigidity and unlike the crappy stock guards, there is no chance of the same bending and flexing happening, these things are super strong. The guards are painted in satin black, matching the finish of the other custom parts and components that are also painted in the same standard satin black. 

Flat pattern design of the mud guards on the Easytrailer (Harbor Freight) folding utility trailer
Flat pattern design for the mud guards

Mounting the guards onto the trailer, a simple 2mm mild steel bracket was designed and manufactured for the purpose. These mud guard backings were heavily influenced but the stock mounting brackets with the main difference being that the original parts were too short and could not clear the large alloy rims. Essentially the idea of mounting the guards are the same, only upsized to suit the new larger parts. The only real deviation from the original design was to include a longer horizontal flange along the top, almost the same length as the internal width of the mud guard. This was included for additional support for the guards so as the entire width of the aluminium guards had some for of mechanical support. 

Custom aluminium chequer plate mud guards fitted on the Easytrailer (Harbor Freight) folding utility trailer, outside view also showing the new hub and axle setup.
Custom aluminium mud guards fitted on the trailer, outside view also showing the new hub and axle fitted.

Again, these mounting brackets were primed and then painted in satin black, matching the colour of the mud guards along with all the other custom bits and pieces on the trailer. 

In an attempt to help dampen any vibrations caused when going over bumps, a few strips of foam rubber tape was placed on the surfaces where the mounting bracket and mud guard would be coming into contact with each other. Not only was this to dampen the vibrations, but also to stop noises, such as rattling or squeaking, from the two metal parts rubbing against each other.

Mounting bracket for mud guard fitted to frame of Easytrailer (harbor freight) folding utility trailer. Foam tape strips installed along top surfaces to help reduce vibrations.
Mounting bracket for mud guard fitted to frame of trailer. Foam tape strips installed along top surfaces to help reduce vibrations.

While the mounting bracket holds the mud guards in a good enough position on the trailer, it does still unfortunately have wobble and vibrations over the bumps as the standard guards did, although nowhere near to the same level as did the stock guards. This is mainly due to the thin steel being used for the mount itself, at only 2mm thick, there just isn’t enough structural rigidity in the metal to prevent the bumps from the road transferring up through the mount and into the guards. Added to the this the increased mass of the guards themselves and it’s no wonder there is still some movement. 

Obviously, there will need to be additional bracing and support for the new mud guards however at time of publishing this was still a work in progress, once a solution has been designed and manufactured the post will be updated.

Toolbox Cradle and Jerry Can Cradle

As part of a weekend of karting, many additional items must be brought along. Among the most important items that must be brought along to a race meet is a full set of tools, for working on the kart and fixing things when they break. In addition to tools, enough petrol to fuel a days driving must also be brought along. Up to this point, transporting all these items was simply a case of putting them (tools and petrol) into the back of the van along with everything else that had to be taken to the track. This is a perfectly acceptable and reasonable way to go about moving these items. However, there were a few factors which lead to the design of these cradles for these particular auxiliary items.

Sketches of the initial concept for the toolbox and jerry can cradles. A crude diagram as to the mounting system swell as gussets.
Sketches of the initial design concept for the toolbox and jerry can cradles. A crude diagram as to the mounting system as well as gussets.

The toolbox: in the workshop there is most tools for doing any number of different tasks, every tool has a purpose and ever tool has its place in the workshop. On a karting weekend, that system gets thrown out the window. Tools are here, there and everywhere. It becomes chaotic and unorganised, moving tools from the workshop, to the van to be taken to the track and then back again. This doesn’t sound like a big deal but the one thing that shits me more than anything in my workshop is going to go grab a tool and it not being in the place where it should be when I need it. This practise of taking tools out of the workshop is not good for time management or efficiency on the job and need to be stopped. All the workshop tools need present and accounted for, not mixed in with go karting tools that are taken to the track. 

The 6 Drawer toolbox to be mounted into the custom designed cradle and mounted to the side of the Easytrailer (Harbor Freight) folding utility trailer.
The 6 Drawer toolbox to be mounted into the custom manufactured cradle and mounted to the side of the trailer.

What resulted was is a dedicated, six drawer toolbox filled with the tools needed for working on karts, either in the workshop or at the track. This toolbox stays with the trailer, the idea being that the trailer could be loaded up with all tools, along with one of the karts, the night before and just hitched to a tow vehicle (whatever that tow vehicle may be) the morning of a race meet. 

Toolbox cradle mounted in position on the side of the frame of the Easytrailer (harbor freight) folding utility trailer. The aluminium chequer plate floor panels have yet to be installed at this stage.
Toolbox cradle mounted in position on the side of the frame of the trailer. The floor panels have yet to be installed at this stage.

When either in the workshop or at the track, the toolbox could stay either in the cradle on the trailer or be taken out and moved to a more convenient location. Regardless, when the toolbox is in the cradle all the drawers can still be opened as normal, this means that once the trailer is parked in the workshop or next to our pit garage, it can remain on the trailer while still allowing access to all the tools needed if required.

Jerry cans: While it is easy enough to simply put jerry cans into the back of a van or car, there remains one main problem – petrol smells bad, really bad and is bad for your health. When stuck in a van full of stinky petrol fumes, it makes an already long drive even longer. Not to mention if not properly secured, it can spill and get into places it’s not meant to. 

Jerry can cradle mounted to the frame of the Easytrailer (Harbor Freight) folding utility trailer.
Jerry can cradle mounted to the frame of the trailer.

The purpose of the jerry can cradle was therefore to have somewhere secure where two 5 litre cans could be strapped safety in place and not expose the occupants to all those lovely smelling fumes that go along with the petrochemical.

Probably the greatest design challenge for these cradles was how to actually mount them to the trailer. This presented several problems. A typical location of additional toolboxes is on top of the drawbars of the trailer. This normally would be a perfect spot for a toolbox but due the way the trailer was going to be parked in the paddock and while still allowing for easy access to the drawers of the toolbox, it meant it had to be mounted onto the side of the trailer. 

It’s the same situation for the jerry can cradle albeit on the opposite side of the trailer. The added bonus of putting the jerry cans on the opposing side, the same side as the petrol filler cap on the tow vehicles, meaning when filling up the van there would be no need to swap over sides to fill up the jerry cans.

As the locational requirement for the cradles was to be on the sides of the trailer, the next issue was how to actually mount them to a relatively thin cross-sectional area. The ‘C’ section of the trailer doesn’t have a great deal of meat on which to securely mount something tall and heavy. The toolbox is 340mm and a jerry can is 280(ish)mm in height respectively. The mounting face on the side of the trailer, by contrast, is only a pissy 70mm. Not to mention, the steel itself only being 2.5mm thick, way too thin to simply mount a heavy toolbox or containers full of liquid. Bolting or screwing solely into the frame was not going to be an option that would work out in the long term. The weight of the objects acting on such a small and thin area, amplified by the bouncing up and down while travelling on uneven surfaces on the road would eventually cause it to fail, most likely deforming the thin steel so much to a point that the fixings being used would eventually be ripped out from the side.

Another design consideration and constraint was to use only existing bolt holes and fixing points that come standard on the trailer from the factory. These points are relatively strong, some being reenforced in places with thicker steel or overlapping steel sections. With that in mind the design of the cradles bolt directly to these locations, utilising the strongest fixing points on the trailer.

To further support the mass of the cradles, there are additional mounting reinforcements to ensure they could be securely mounted and not end up falling off while driving down the road. 

The first are small set of supporting brackets. As both the cradles hang below the frame, there was potential for there to be a pendulum effect caused by the unsupported mass bouncing up and down. The supporting brackets simply take up this unsupported mass and stop any potential movement. The brackets are bolted to the frame from underneath, at a junction point of two of the frames C sections. This is then bolted to the back of the cradles using two M10 bolts. This holds the cradles in place and reduces vibration and movement.

The second complimentary solution, is a set of cantilever gussets, 400mm in length, that are extensions off the back the cradles, traversing in towards the centre of the trailer. These gussets are designed in such a way as to rest against the bottom side of the flooring panels, taking up part of the weight of the toolbox and jerry cans respectively and then transferring the mass, by means of a cantilever action, to the floor panels. While the gussets are not actually bolted to the floor panels, they are firmly pressed up against the underside of the floor. 

Toolbox cradle mounted to the frame of the Easytrailer (Harbor Freight) folding utility trailer.
Toolbox cradle mounted to the frame of the trailer, support gussets can be seen to the right of the frames C section.

While fundamentally the design of each cradle is based on the same concept, there are slight differences to the respective designs and also dimensionally, accommodating for their respective cargo. The toolbox cradle is the larger of the two, being longer and deeper than that of the jerry can cradle. The toolbox cradle holds the six-draw toolbox which is 595mm long, 255mm deep and 340mm heigh. In addition to the toolboxes dimensions, there is 3mm clearance on all side for rubber to line the inside of the cradle and stop the tool box from potentially moving about while in the cradle, preventing any scratching of the lovely shiny red paint on the toolbox itself. There this also an extra 10mm in depth to allow clearances for the bolt head that actually hold the cradle onto the trailer. With all these little additions, the external dimensions start becoming rather large. In fact, the tool box cradle measures in at (not including the gussets on the back) 615mm long by 280mm deep. 

Despite the toolbox being 340mm in height, the cradle is only 140mmtall with this dimension being dictated by the positioning of the handles on the sides of the toolbox. This is to have clear and unobstructed access to the handles, with the sides of the cradle come up to the bottom most part of the handle insert on either side of the tool box.

The front face of the cradle has a cut out profile to allow for the drawers to still be opened while in the cradle. This cut out leaves just enough clearance on each side of the drawers allowing them to be opened and used as normally would be when not in the cradle. It means the toolbox can also be left on the trailer either while at the track or while in the workshop allowing unobstructed access for opening the drawers.

The Jerry can cradle is closely related to the toolbox cradle, in fact it is a modified version of the toolbox cradle, simply having been resized for two 5 litre jerry cans instead of a toolbox. As you’d expect, because the intended cargo is physically smaller, so is the cradle that carries it. Dimensions are smaller than the cradle on the opposite side of the trailer, at 400mm long and 220mm deep (not including gussets). Height is the same however, this was purely as a result of the cradle (jerry can) being a scaled down version of the toolbox cradle and thus it retained the same height. By keeping the height the same, it also allowed to keep the gussets the same size also, with the gussets adding 220mm to the overall depth dimension of this cradle. 

Jerry can cradle mounted to the frame of the Easytrailer (Harbor Freight) folding utility trailer. with two 5lt jerry cans in the cradle.
Jerry can cradle mounted to the frame of the trailer with two 5lt jerry cans in the cradle.

Unlike the toolboxes cradle, there is no cut out or open face on the front as there is no need for one on this side of the trailer. While the toolbox still needs access to the drawers, the jerrycans just need to be securely held in place, hence the front face of the cradle is solid and unbroken. 

Running along the top edge of the front face is a tie down rail for securing the jerry cans in place. This perforated rail is at 45 degrees to the top edge and runs its full length with eleven 12mm holes spaced approx. 50mm apart. The design of this tie down rail on the cradle is based on the profile of the main tie down rails running along the sides of the trailer (more on these shortly), the tie downs on the cradle will complement the tie down rail on the trailer and allow for an occasional strap to be used in holding the jerry cans in place.  

Both the cradles are manufactured from a single piece of 3mm mild steel. The flat profile having being laser cut, then formed by folding on a hydraulic press to the required shape. The corners have been seam welded for extra strength and rigidity. Both cradles have been primed and painted in the same satin black finish as with everything else.

Jerry can cradle (left) and toolbox cradle (right) for the Easytrailer (Harbor Freight) folding utility trailer. Folding and welding completed and about to be etch primed and painted.
Jerry can cradle (left) and toolbox cradle (right) in raw steel. Folding and welding completed and about to be etch primed and painted.

While the finished product turned out as good as could be hoped for, there was an oversight because of the choice of material. Once all cut, formed, welded and painted, the weight of the boxes was substantially more than was originally anticipated. They needed to be sturdy for sure, but by opting for 3mm thick steel, it proved to be somewhat over kill for what it’s designed to do. A bomb could go off nearby and not put a dent in these things, such is their structural strength. However, by this stage, all the fabrication was completed and too late to revise the design. If the need arose to manufacture again, a thinner gauge steel would be used along more cut outs and voids to further reduce the weight without compromising too much the overall structural strength. 

Tie Down Rails

While there are points to securely tie down a load onto the Easytrailer (Harbor Freight) trailer, they are few and far between. Most owners of this style of folding utility trailer, myself included, would utilise the side stake brackets, of which there are eight on the trailer as standard with two on each side. While these brackets resemble something similar to a tie down point, their intended use is to have a piece of 2 by 4 slotted in for the vertical supports of timber sides to go on the trail. However, these brackets were not really meant to be used as tie down points, this becomes even more evident when trying to secure a ratchet straps hook into the part. It will go in eventually, not as easily as it should and only after a struggle accompanied with much profanity. 

3D render of tie down rail (high lighted in grey) shown in its relative position on the frame of the Easytrailer (Harbor Freight) folding utility trailer.
3D render of tie down rail (high lighted in grey) shown in its relative position on the frame of the trailer.

Consequently, there was another reason the brackets could not be relied upon as tie down points. As the cradles, for toolbox and jerry cans, are using the mounting points originally occupied by the brackets, it meant the sacrifice of one (side stake bracket) on either side of the frame. Losing two of the brackets reduced the potential locations to tie down loads, especially at the front of the trailer. 

Apart from these brackets on the side there are also four eye bolts, one at each corner, that can be used for tying down a load. These eye bolts would be the preferred method of securing loads, however due to their location in the very corners of the trailer, it severely limits the ability to choose an appropriate anchoring point for whatever is being hauled on the trailer.

The solution for adding more tie down and anchoring points came from existing products on the market. There are a good number of utes and trucks on the market that have a simple tiedown rail system design built into their trays. In essence, it is a long strip of metal with holes at regular intervals, this is run longitudinally, the whole length of the tray, allowing for any number of positions to tie down a load securely. This is the simple, yet effect solution is the concept on which the tie down rails for the trailer is based. 

These custom-made tie down rails are manufactured from the same grade 3mm steel as with the cradles. They have been laser cut to ensure a correct and accurate sizing, press folded at 90 degrees and then painted in satin black, matching all other custom made components on the trailer.    

close up detail of the tie down rail on the curb side of the Easytrailer (Harbor Freight) folding trailer
close up detail of the tie down rail on the curb side of the trailer

There are four of these tie down rails in total, two for each side at 1150mm in length, and with a left hand and right hand variation. The reason for there being two on each side and not just one single 2.4 meter long rail on either side, was to maintain the trailers folding functionality. By splitting the tie down rail in the centre, it allows for the hinge action of the trailer to still work and be folded. 

The rails themselves are sandwiched in-between the frame of the trailer and the flooring panels. Each rail sits directly on top of the longitudinal C section of the frame, then has the floor panels placed directly on top of that. They are then secured into place with shared M10 bolts that also hold the floor panels in place. The rails have accurately cut holes which line up with that of the standard hole locations on the trailer, meaning that once the flooring has be correctly positioned and then securely fixed in place, so have the tie down rails. This method of mounting the rails ensures that they are extremely well affixed to the trailer, with no doubts about how much strain they will be able to take when securing a load.

The four tie down rails, for the Easytrailer (Harbor Freight) folding utility trailer, having been primed and now ready for painting.
The four tie down rails having been primed and now ready for painting.

To maintain the floor panel size of 1220mm x 2440mm (two individual panels of 1220mm x 1220mm), the rails were folded in such a way that they extended past the edge of the flooring panels by approx. 4mm, this meant the standard sized floor panels could be used and installed normally without the need for alterations or modifications to either the part or the way they were to be mounted to the trailer frame. However, by including this offset there would be compromises that would need to be made elsewhere as we will shortly find out.

Hinge Brackets (Revision 2)

In order to accommodate for the new tie down rails installed on either side of the trailers length, the original size of the hinge brackets, which had already been redesigned once prior (See part 3 of this blog series), needed to be altered once again. As this new feature (tie down rails) was never part of the original design, the standard hinge brackets would not have been tall enough to allow the clearance need when in the folded position, they would in fact been fouling on each other and impede the ability to fully fold the trailer.

Painted hinge bracket and spacer to replace the original brackets on the trailer
First revision hinge bracket and spacer

To overcome this potential issue, a new revision of the hinge brackets was designed and manufactured. While the basic shape of the hinge brackets remained the same, the biggest alteration was in its overall size, being they have a taller profile to accommodate for the height of the tie down rails. The overall height increase is only 30mm when compared to the sizing of the original part, but this additional height raises the pivoting point, putting its centreline on the same plane (or close to it) as the top of the rails. What results is the tops of each of the tie down rails sit parallel and on top of one another when in the folded position.

Hinge brackets of own design. Initial revision of the bracket (left) and the first revised version (right), manufactured from Hardox, shown in a side by side comparison. Hight difference between the revisions is plain to see, this additional hight is for clearing the new tie down rails installed along both sides of the trailer.
Hinge brackets of own design. First revision of the bracket (left) and the second revised version (right), manufactured from Hardox, shown in a side by side comparison. Hight difference between the revisions is plain to see, this additional hight is for clearing the new tie down rails installed along both sides of the trailer.

Now cast your mind back not all that long ago, to part 3 (Project West: Part 3 – Replacement Parts) of the project. I mentioned in this post, relating to my own remake of the standard hinge brackets: “For the subsequent revision, a higher grade of steel, such as Hardox, will be the material of choice” And as promised, the material for this new revision is indeed 3mm Hardox. 

Hardox, is a wear resistant steel, manufactured by SSAB (Swedish steel), that wears slowly even when under heavy mechanical loads (more info about Hardox available from SSAB website). It was chosen as the preferred material as the original brackets which came on the trailer were so badly worn the bolt holes were no longer round but oval. By using the more wear resistant steel it should ensure the longevity of these hinges, especially considering how frequently the trailer will be opened and folded.

Revised Hardox hinge bracket and spacers mounted onto the frame of the Easytrailer (Harbor Freight) folding utility trailer.
Revised Hardox hinge bracket and spacers mounted onto the frame of the trailer.

 As the tie down brackets protruded out from the edge of the floor plates of the trailer by approx. 4mm on each side, there needed to be additional spacers added to offset the hinge brackets enough to allow clearance away from the tiedown rails. This requirement is somewhat of a knock on effect from multiple different new parts being added. The hinge brackets had to be offset to clear the tie down rails and the tie down rails had to be offset to clear the new floor panel. 

To get to the required offset distance, multiple sets of spacers are used on the front and rear frames. On the front frame, one 3mm and one 4mm while on the rear frame a single 3mm. Both the 3mm and 4mm spacers have the same shape and being manufactured from the same grade of steel, with the only difference being their respective thickness. These are then sandwiched in-between the hinge bracket and the side of the frame of the trailer.

Revised Hardox hinge bracket and spacers mounted onto the frame of the Easytrailer (Harbor Freight) folding utility trailer, shown from above.
Revised Hardox hinge bracket and spacers mounted onto the frame of the trailer, shown from above.

Without the use of these spacers, the tie down rails themselves would have had to have had their design and profile altered to allow for the required clearance. Most likely it would have resulted in 40-50mm being removed off the end of the upright section and hence losing several tiedown points in the process.

Tie down rails while trailer is in folded position being parallel to each other.
Tie down rails while trailer is in folded position being parallel to each other.

Once all mounted up, this spacing configuration worked perfectly in giving the required clearance for the hinge brackets around the tie down rails and as before a single M10 nut and bolt was used as the pivoting point for the two halves of the hinge. With these brackets now being made from Hardox and not the cheap and crappy steel as was before, hopefully this will give some longevity and reliability to the part.

Finally, along with all the other auxiliary items and custom parts, even these rather inconspicuous little brackets and the various spacers were all painted in the same satin black as to match the running colour scheme for the trailer.

Floor/Frame Packers

With any alteration or change there has to be adaptations made to allow for the usage of new and custom parts to work with the existing design. In this case, these Floor/Frame Packers were a necessity addition. 

With the inclusion of the new tie down rails running along the sides of the floor of the trailer, it created an issue which wasn’t allowed for in the original design. As the tie down rails sit under the floor panels it raises the panels up by the thickness of the steel (of the tie downs rails), which in this case is 3mm. In addition to this 3mm, there is also an inherent 2.5mm gap from where the transverse C sections slot into the longitudinal C sections and not being levelled. This leaves an unsupported gao of almost a 6mm (5.5mm) under most of the floor panels width.

3D render of the frame/floor packer for use with the Easytrailer (Harbor Freight) folding utility trailer
3D render of the frame/floor packer

This gap wasn’t too much of an issue prior to these new items being added, in fact at only 2.5mm, and being the floor material was plywood it could bend without being deformed too noticeably. However, with the additional rails increasing the gap and a new floor panel material, 6mm this is simply too great. 

The concern was that if the gap was not filled and supported, over time the floor panels would bow out of shape, after all the edges would be sitting on top of the tie down rails being the high points and then sagging in the middle. It would be inevitable, especially after carrying heavy loads, that if not addressed the aluminium floor panels would no longer be flat. 

To rectify this abscess between the floor and frame, a simple ‘packer’ was designed to resolve this potential problem. The packers, six in total, are manufactured from 6mm mild steel, again laser cut for greater accuracy, and then sandwiched in between the top of the frame and the bottom of the chequer plate floor panel and at 1150mm in length they almost span the full length of the floor. 

Profile of the packer/space and how it fills in the gap between the top surface of the frame and the underside of the floor panel.
Profile of the packer/space and how it fills in the gap between the top surface of the frame and the underside of the floor panel.

As weight always has to be considered for each of the custom designed parts, the packers are cut down in such a way to maintain the absolute minimum functional profile, that is removing as much of the steel from the part as possible while still maintaining its primary purpose, to pack out the gap between trailer frame and floor panel. 

Aluminium was considered as a possible material but would have required more secondary processing for becoming a finished and usable part. This includes cleaning and deburring edges (due to aluminium not cutting cleanly on a laser cutter, compared to mild steel which will cut in such a way that almost no cleaning is necessary), and surface prep for painting such as lightly roughing up the surface prior to etch priming. 

Test fitting of floor packers/spacers, loosely placed on top of the frame of the Easytrailer (Harbor Freight) folding utility trailer.
Test fitting of floor packers/spacers, loosely placed on top of the frame of the trailer.

Given the size, shape and profile of the parts cutting in aluminium was going to be lighter than steel but not by much, hence all the additional work after being cut would not be worth the minimal weight savings.    

As the intended location for these parts was on the underside of the trailer, each of the six packers painted in satin black to help protect from the elements and any potential rust. While the paint job of each was by no means perfect, they are for the most part going to be out of sight, enough coats of paint were used to hopefully prolong the life span and make them capable of enduring harsher conditions such as rain and road grime.

With the inclusion of these packers, each of the floor panel is now supported along it’s full width at each of the C section locations on the frame, that being front, back and in the middle making the entire floor incredibly strong, level and with no play or give at all.

Aluminium Floor Panels

As purchased, the trailer came with timber floor panels, unfortunately these timber pieces had also seen better days and were thrashed. Not to the point where there were big holes in the panels or falling to bits but rather were damaged with the edges being swollen and water-logged, a result of not being sealed and allowing moisture and water to expand the fibres of the timber. They were out of shape too, being bent and bowed from years of having heavy loads, usually motorbikes, put on them over their life time and finally they were faded, chipped and cracking, put simply they looked like shit.

The original timber top platform are put back onto the folding easy/harbor freight trailer.
The original timber top flooring panels on the trailer.

These two identical floor panels  must have been made by a pervious owner rather than being the factory floor panels, as the optional factory floor panels are 17mm Formply not 16mm ply as came on the trailer at time of purchase. 

Easytrailer do offer the flooring panels as an optional extra when buying new. These panels are 17mm Formply plywood, a timber material used predominantly in concrete formwork, it is strong and durable hence its use for concret forming. Because it also has sealed edges it means moisture cannot enter into the panelling itself making it a suitable choice for trailers which, believe it or not, may sometimes get rained on or get wet from time to time. 

This trailer, as purchased, came with 16mm builders ply that was not sealed and as a result caused water damage with swelling along the edges and corners. This was not helped either when, while towing my go-kart back from a day at the track, got caught in the middle of a torrential down-pour. The ply that came on the trailer really is not great in the rain. 

While floor panels were an issue that could have possibly been left alone, the look of the shiny new red frame with tired and busted plywood panels bolted on top, looked mismatched. They had to be changed for something better!

Aluminum tread plate after being painted with two coats of satin black drying in the sun.
Aluminium chequer plate floor panel after second coat of satin black.

Yet again, this was a chance to make something better and improve on an existing part. After further measuring followed by session on autoCAD, the replacement floor panels drawn up and ready for laser cutting. Unlike some other parts that were drawn up on AutoCAD and then laser cut (i.e. hinge brackets), these panels were a like for like design sharing the same size and all the same hole layouts.

For the replacement floor panels, the timber was dumped in favour of something with greater durability and strength. 3mm 5052 aluminium chequer plate is the material used. It is super strong, relatively light weight and best of all can go in the rain with getting water-logged.  

Aluminium chequer plate floor panels mounted on the Easytrailer (Harbor Freight) folding utility trailer.
Aluminium chequer plate floor panels mounted on the trailer.

Once the new floor plates were laser cut, there was consideration about putting them straight onto the frame, bolting them down and saying that’s that. But instead in keeping with the theme of repainting and making the trailer as visually pleasing as possible, the two panels were painted in satin black prior to being installed.  

Once painted the floor panels were good to go and ready to be mounted onto the trailer. The panels are held inplace by the same M10 bolts (fifteen per panel) and as the profile was a copy of the original panels, the bolt holes remained in the same locations as from the factory.

Conclusion and final thoughts

Finally the project is completed, it has taken the best part of 5 months to take this hum-drum folding trailer and make it into something that doesn’t look like it was found at the bottom of a lake. The final look and overall quality of the new custom parts is impressive and turned out as good if not better than could have been hoped for. This was a huge relief as sometimes when a design goes from being in ones head and then turned into something tangible, the idea somehow becomes distorted and changes along the way. Luckily for me, this trailer project came to life as I’d hoped it would have, and the results exceed my own expectations to say the least. 

Go Kart loaded onto the Easytrailer (Harborfreight) folding utility trailer and at the track
Go Kart loaded onto the trailer and at the track

For me personally, there were many firsts. The first time having something of my own design being manufactured, the first time painting aluminium and the first time putting together a wheel hub are just a few examples that spring to mind. Along with many lessons learnt too, such as it always takes longer than expected to have something manufactured by a third party. All valuable information that can be carried over to the next project.   

In the end it has been a worthwhile assignment and one that I am glad that I was able to undertake. The trailer now looks great, it is well made and put together, and should easily last another ten years plus. And of course, it serves its primary function of taking my kart to the track more than adequately. 

In closing, thank you dear reader for following along with this build and I hope that you have taken some valuable inspiration from these posts for your own projects. 

See you on the next one!  

If you have enjoyed the project so far please share on social media, while you’re there don’t forget to follow me, RB42, on Twitter, Instagram and Facebook for updates and new releases. 

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