Build Thread: Roof Rack For a JK Wrangler

[S.Bartfast]

Current state of the project.

INTRODUCTION

I have been doing a fair amount of work on building a roof rack for my JK Unlimited and I've been maintaining a thread about it on a different forum. Thinking this project may well interest other Jeep drivers I thought it could be beneficial to reproduce the thread here.

I'm going to maintain the first few posts in this thread with updates to the Design, Fabrication and Result of the project, and of course keep up to date with the discussion at the tail end of this thread. The idea being that if you're new to the thread, or wanting to review something in particular, if I do my job right you should be able to find it in these three posts. If you want to ask something or discuss something in detail then the end of the thread is your friend.


INSPIRATION
I bought my first (and current) 4x4 a little over a year ago largely with the idea of using it to take my family and I places to go kite buggying.

This is what my current kite buggy looks like:


Working out exactly how to transport these buggers has long been a hassle for kiters, so when I finally bought a 4x4 my plan was to just get a roof rack and carry the buggy on the roof and be done with all that annoying disassembling and reassembling we all endure. It didn't take me long however to discover that simply slapping a roof rack on a JK wasn't as simple as I'd hoped. The main problem, as all Wrangler drivers will be aware, is that Wranglers have removable tops and that fibreglass canopy is in no way strong enough to support a decent roof rack. In fact all the racks with any reasonable load carrying ability actually have arms that come down the side of the car and bolt to the main body of the car itself.



This posed two problems...
First they were rather expensive (about $2000 for anything decent)
Secondly, they weren't very strong.

Here is an image of a "Congo" rack that a fellow forum member posted which vibrated itself apart on a Simpson crossing a little while ago:



The full thread can be found here.

Anyway, after months of searching and agonizing I finally decided to build my own!

[S.Bartfast]

DESIGN

I spent a lot of time researching mounting systems and general construction of Wrangler roof racks and by far the best looking rack I came across was a custom rack made by a German expedition team:


And the best example of a build I came across was the excellent build blog of the XXXpedition Project XXX rack:


Both these racks used a system where they were mounted on the "tub" of the Wrangler using mettle plates that were bolted in using the same bolts that hold the roof itself on:


And both these racks appear to have been welded together into one complete piece:






So with this in mind I started trying to learn how to use a CAD modeling package...

After a little searching and advice Google's SketchUp seemed a good place to get started.
Now I knew nothing about Computer Aided Design when I started on this project and to call getting competent in CAD a "steep learning curve" is quite an under statement!

After I don't know how many hours of clicking, dragging, searching and bashing my head against SketchUp I finally cam up with this design:

While this is now quite an embarrassment for me, at the time I was quite proud of my efforts

One problem I had was that it was almost impossible to get any good measurements of the Jeep. While it looks vary boxy and square when you actually take a tape measure to her you quickly discover just how squarish she isn't. Not only are the curves hard to envisage while you're at the computer it's almost impossible to get any good points from which to measure even basic dimensions. So I turned to Mr Google again and searched for a 3D model of a Jeep that I was hopefully going to be able to use to design my rack around, and I was in luck.

I came across this lovely 750,000 surface model:

While it was a bit large (the model measures about 1/2 a kilometer long in SketchUp) and it's agonizingly slow to work with I knew I was onto something. Scaling the model by 0.00725 makes it more or less the right size and I was able to reduce the 750,000 surfaces to a still respectable 190,000 with a great little open source program called MeshLab. While it still a little slow and looks a little rough it is quite workable. I also found I was able to delete parts of the model with MeshLab and made a copy consisting of only the roof and windscreen that was a lot easier to work with.

Anyway, once I had a model to build the rack around I was able to make a much better proportioned rack:

Notice how the lower part of the legs are wider than the top. Given I now had a model I was now able to identify and follow many more of the curves the JK has.

Here is what it looked like with the roof section around which it was built:


And finally a rendering with the full car:






From here it has undergone several variations...

The first was that I was concerned about where a snorkel might fit:



I had a couple of ideas, one of which was to built that little 'S' bend to bring the leg in over the windscreen pillar a little, the other was to make the whole top of the rack a little narrower, which kind of made it look a little "Landrover-ish":

In the end I decided the skinny rack just looked silly with the big fat back-end hanging out at the rear of the jeep, so I opted for the "squiggle-snorkel" design.

But rather than have one side "squiggle" in to give clearance for the snorkel I decided to "squiggle" both sides and kept it symmetrical. I also moved the "squiggle" further back such that the whole front of the rack became narrower just above the driver's door:


This meant that the top rail would need to have an 'S' bend as well:



While moving the 'S' bend like this seems like a fair bit of efferent the reason I did it was to make the front part of the rack narrow enough for the rear wheels of my buggy to be able to straddle the rack nicely:

If you looked closely in the previous image you would have also noticed that the 'sloped' where the upper rail met with the lower rail at the front had been rounded down into more of a "bull-nose" look, and the vertical rails that ran down the windscreen had been extended to intersect where the top rail bent down to meet the bottom. This was to provide a nice little notch for the axle of the buggy to snug into
Another adaption made at this point was to make a small gap in the top rail at the back. This was added for the front wheel of the buggy to nestle into.

And this is how the final design has ended up:




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Next is to start on the fabrication!

[S.Bartfast]

FABRICATION
(this is proving to be quite a long post, so buckle up)

The first thing I started working on was the mounting plates (or "Feet") that rest on the tub of the Jeep. I made these out of the largest piece of square hollow section I could find:


I won't bore you with the details, but these feet were incredibly annoying to make.
Basically it involved a bit of cutting with an angle grinder then lots of bending with leavers and clamps in the vice and a hell of a lot of bashing with a hammer:


The hole in the upper right is where the bolt that holds the hardtop goes through. The "window" in the bottom left is because the hardtop has a join in the back corners and a seam bulges out such that the plate wouldn't fit snugly unless I gouged out the window (sorry don't have a photo to explain).

I lined the underside of the plate with vinyl to protect the Jeep:

This is the same vinyl they use in hospitals where the wall meets the floor to save the wall getting scuffed.
If you look closely you'll be able to see that I gouged out a channel in the vinyl to enable the plate to snug up closer to the tub.

And this is how it fits on the Jeep itself:

Again, if you look closely you can see the lip of the tub nestling into the channel I gouged out.



Next was to work on the frame of the rack itself.

The ProjectXXX rack (with the excellent blog) was actually built using straight sections of pipe and welding in elbow joints. Originally I intended to do the same but ended up opting for tube and bends instead. My reason for originally opting for "pipe and elbow" construction was mainly because I didn't have access to a tube bender, and I wasn't even sure all those bends were going to be possible with a bender anyhow. I did however have access to a good welder (boiler maker by trade) and he was willing to spend a few days swinging welding rods for me (:

I ended up however deciding against the "pipe and elbow" construction for a few reasons. One was the incredible amount of work it would require. If we were to opt for elbow joints all told there were 40 but joins that would need to be welded. Another concern was the weight. Using pipe I would be after 2" schedule 10 which had a wall thickness of 2.769mm, which has a weight of 4kg/m. It would be an option to drop to schedule 5 (with a 1.6mm wall thickness) but the welding would be a lot more difficult, so I ended up deciding to opt for bending instead. After a bit of searching and a few phone calls I landed on BDL Holdings who have a "Mandrel" bender and were happy to sell me 2" tube at $10/m and bend it for $10 per bend. I was set!

After pulling apart the model I concluded there were 8 lengths of steel I would need to have made:

In total I would require 22.6m of tube consisting of 24 bends.

The bender BDL have is capable of bending 2.25" tube in a radius of either 87mm or 110mm. So I modified the design to employ 87mm and 110mm bends and sent off the plans for the first piece of steel.

I wanted to get just one piece first to make sure I had the dimensions rite, so I ordered the "Rear Hoop" first:



Here is a copy of the actual diagram I gave them:



And sure enough, a while later it was ready to collect:

It was really exciting to actually have the first piece of the rack proper in my hand

There is a bit of "green" on the ends of that first piece, but after lobbing them off it fit perfect so I ordered the "Front Hoop" and "Ladder Rungs":


This gave me enough to build the first free standing section:


The "Hoops" where easy enough to trim to fit. Then came the scalloping of the ladder rungs.

They weren't that hard, just annoying.
Basically it just involved a lot of this:


I did manage to find a cute little program called "Tube Miter".
It's a simple little program that creates templates for you to print out and follow when scalloping tube:


Anyway, when all was said and done I had 12 nicely scalloped lengths of steel ready for assembly:


Next was to break out a welder...
First thing we did was to suspend the "Rear Hoop" from a pulley mounted to the roof of the garage. I then backed the Jeep up to where the hoop was suspended and we tack welded the hoop to the mounting plates (feet) that were bolted on the car. We then did the same with the "Front Hoop" and tacked the "Ladder Rungs" in. Once it was all tacked together we removed the rack from the car and welded the joins properly:

And a rack is born.

Once all was done we did indeed have the first free standing section and it looks pretty much exactly as I expected from the rendering:





Flushed with the success of this first section I thought I'd try my hand at swinging the welding gun myself
I decided to cut a couple of links from a chain and weld some lugs onto the rack so I could raise and lower the rack with the pulley:


It works fairly well.
I can now hook a chain onto the lugs then raise the rack up to the ceiling with the pulley:





However, as can be seen in the "ground level" photo of the rack on the back of the car above, the rack looks to ride a little higher than expected and kind of looks a little odd. The gap between the roof and the rack is between 75mm and 80mm (which I thought would be a good amount of clearance) but when on the car it appears to be too high:


Another issue was that the gap between the lower and middle ladder rungs is larger than the gap between the middle and upper rungs:

Most people wouldn't notice but it annoyed the heck out of me!

And the ladders of the rack kind of protrude out the side of the car more than is necisary (particularly at the bottom):


All this led me to decide to remove 50mm from each of the 4 vertical sections that connect the top of the rack to the mounting points (which I refer to as 'legs').

To accomplish this I decided that rather than simply removing 50mm cylinders of tube from the 'legs' I would remove "chevrons" instead. This I thought would not only make the join stronger but would also make the join itself less noticeable in the finished product.

So I set about drawing up a template:


And cut it out:


Using the template I then marked each of the 4 legs:


And cut them:




As you can see I also 'staggered' the cut so as to try and obscure the joins in the final product:



When putting the 'legs' back together I decided I would make internal 'gussets' to give the ends something to weld to. I made the 'internal gussets' out of the same tube I used to construct the rest of the rack:


I slit these down the side and removed a strip of material to enable them to contract and fit inside the other tube:


Then hammered them into the 'legs':


As you can see this makes quite a good looking join:


And here is the rack 50mm lower that it was before:



While removing these sections from the 'legs' does indeed lower the rack by the desired amount it also brings the 'feet' closer together:




This meant the feet had to be cut off, the ends of the tube trimmed a little then the feet welded back on.


The next part to work on was the lower 'S-Bends':


These required tube to be bent with the larger 110mm radius:


Now the whole purpose of the 'S-bend' is to enable the rear wheels of the buggy to straddle the front part of the rack. After a few measurements the width of the rack, from outside face to outside face proved to be 1330mm, and the distance between the rear wheels of the buggy (from inside face to inside face) proved to be 1265mm. This means both sides of the rack will need to come in 32.5mm in order to accommodate the buggy.

After a bit of scratching on the pavement with a stone (and not to mention scratching of my own head) I managed to calculate that the tube needed to be cut at the arcsine of (110 - 32.5)/110, or 44.8 degrees:

As an aside, at this point I would like to thank Mr Forsyth (my year nine geometry teacher) and acknowledge (begrudgingly) that yes indeed
trigonometry is useful in the real world and that it does indeed show up in the most unlikely of places

Anyway, with the drop saw set to approximately 44.8 degrees:


I was ready to start cutting:



After joining the two ends of the 'S-bend' and a quick check for fit:


It was time to fetch another piece of tube for the front cross member:


And put on the rack


Then things slowed down for a bit...

First there was this:


Which was followed by this:


And eventually resulted in this:


But eventually, when I had a good friend over from Finland and I once again found myself between jobs, with a new set of wheels under her, the roof rack finally started to progress again.

We started working on the project in earnest and things were looking good again, but then we hit a problem...
You see, this was a primary design constraint of the original design:



350mm between the roof of the Jeep and the top of the garage entrance.

But with the new car (which has a 2.5" lift and 33" tyres) the picture looks more like this:


This roof rack was designed with very tight constraints and 250mm clearance was just not going to go, so I had to improvise a little redesign.

As a start I decided to make the entire lower level one height and leave the "basket" for a later time and have been toying with ideas on how to make a 'detachable' basket. Unfortunately opting for a detachable basket means that I have had to for go the double front side arms and just have single side arms:


This was a real shame as I very much liked the look of the double fronts and had spent a significant amount of time perfecting there look. But dems are the constraints

This is what the lower section should look like now:



Then came the next hurdle...
I had always intended to weld up the rack as one complete unit (much like the ProjextXXX guys did) and lift it on and off with the pulley, but I then realised there is no way my garage roof would be high enough to lift the whole rack atop the car. Previously to get the back section on and off the car I would hoist the rack up a little higher than the back of the car then back the car in underneath it. With the front arms on it wouldn't be possible to back the car in any more, so I had to come up with a design to allow the front arms to be removed.

In the end I decided to have the front sections as "hockey stick" shaped pieces and bolt them to the main rack using internal plates.

The way the joins would work is to cut a short section of tube and slit it in half lengthwise. I would then compressed the halves in a vice so as to bend them such that they were able to fit inside the original tube, then drill holes in the tube of the rack as well as these internal plates such that they could be bolted in place.

Here's a prototype I made while thinking things over:

In this photo the connecting plate is on the outside of the tube but in the final design it was on the inside.

And here is what it looks like with the bolts attached:


Here's a photo of the inside of the tube:

Note that the bolts do not quite reach to the centre of the tube which means you can have bolts in both sides with out fear that they will hit in the middle.

After being satisfied it would work I started making the real ones:


And welded the nuts to the inside:


Then drilled holes in the main frame for the bolts to go through:



Next it was time to make the front legs (or 'hockey sticks' as we call them)...
My plan was to simply buy replacement Y-brackets and weld the 'hockey sticks' to those removable brackets one removes to lower the winsheild:


Once these 'hockey sticks' and joiners where made all that was needed was a quick coat of paint and she was ready to go on the Jeep:


And here it is as she now stands:

[S.Bartfast]

Result
(Still to come)

[aydanrogers]

Nice build. Just a Q, it looks like it sits pretty high off the roof. Did you design it like that or is it just the angle of the picture?

[S.Bartfast]

Originally Posted by aydanrogers

Nice build. Just a Q, it looks like it sits pretty high off the roof. Did you design it like that or is it just the angle of the picture?

Yer, it does appear to be sitting a bit high from that angle. In reality it is a little high but not quite as much as that angle makes it look. Those uprights also look to be too vertical in the photo but in reality the uprights in fact lean forward such that the forward uprights follow the slant of the leading edge of the window in the hard top.

The gap between the roof and the rack was intentionally made to be something in the order of 100mm to give enough clearance to slide the hardtop in and out without taking the rack off. If the gap does prove to be too big I do have the option of cutting the "feet" off and making new longer feet that extend down the side of the Jeep further thus lowering the point the legs attach and hence reducing the gap. But I really don't want to have to do that

I thought a lot about how high to make the rack. The hardtop is 680mm high and the distance between the centre of the tube at the top and bottom is 833mm. If the tube were to be attached to the feet such that the top of the tube is just below the bottom edge of the hardtop the bottom the the tube should clear the top of the hardtop by 833mm - 2.25", which is 77mm, but that gap is looking a bit large.

As it is we mounted the rack as low as we could on the feet so they are mounted significantly below the bottom of the hardtop:


But still the rack is too high, so I can only assume the bends were off by a bit.
I'll have to get a measure out to check exactly what is going on :s

[Lim@]

well done mate. you're doing very well with sketchup. i don't even know how to do angles in it yet! HAHAHA

do you think you actually needed to put the kink in the tub mounts? what was stopping you just have right angles and having a little gap between the body and the corner of the angle iron?


i really like it though. i was considering a much simpler design but if you keep putting all your plans up then i'd be crazy not to atleast use them as a baseline! HAHA

the bit i was dredding the most was actually the scalloping of the tube but that program looks the biz!

why wouldn't you use a die grinder to scallop it? be a fair bit easier wouldnt it?