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Build: Frame Trial

Bench Seat

Bench Seat [+]

Flanged Tube

Flanged Tube [+]

To make sure I was on the right track with the camper’s design and to give these nylon connectors a good test out, I decided to build a part of the camper that will be frequently used and one susceptible to quite heavy dynamic loads – the chairs!

The layout of the chair’s structure is highlighted in red in this design to show you what we’re testing out.

The measurements for the bench seat framework are 750 x 450 x 750mm (L x W x H). At both ends of the chairs are cupboards/access doors, for both inside and outside access.

In the close up, you’ll notice I’ve used Flexliner’s 15mm winged/flanged extrusion which allows for a 19mm board to be placed flush inside the frame.

Putting it together

Chair Frame

Chair Frame [+]

I put in an order for all the connectors I’d need and the special flanged tube. The standard 25 x 25mm tubing for the legs I just sourced locally.

After a few mitre cuts and a rubber mallet on the job, I quickly had the frame up.

I wanted to keep the frame simple at first, to see where it needed reinforcing the most.

Testing it out

The first test was then of course, to sit on it! Hopping on I could tell it had a lot of movement at the joints, obviously some stiffening was needed (& expected). Apart from that though, strength/compression wise, it felt more than up to the task.

Chair Test 2

Chair Testing [+]

Next I wanted to see if having the aluminium sheet walls fitted to all sides of the frame would stiffen it up enough.

Since the front & back of the chairs will be covered in sheet metal & riveted on anyway, these would act like large gussets and prevent the frame leaning & twisting (at least on the X axis).

I didn’t have any sheets large enough for this test so I had to make do with using strips of flat steel (& a thousand clamps).

The difference was like night and day! Both my wife and I were quite comfortable on it together and could easily hop on and off as we pleased without the frame leaning or twisting in either direction.

Final tweaks

Chair Corner Brackets

Chair Corner Brackets [+]

All that said, we can’t actually have sheet or anything covering the two open ends of the chairs, since these are the cupboard/access doors, but we do need it to be reinforced or it will lean & twist. I figured some corner brackets should do the trick and it was a bonus that they would also act as little door stoppers for the internal cupboard doors.

3D Corner Bracket

3D Corner Bracket [+]

Since I built this, my wife has bought me a 3D Printer (from Winplus) and I have been able to come up with my own printable designs for the corner brackets (& lots of other parts). Here’s a little teaser pic.

Drop a comment below if you want me to tackle a particular part of the build next. Happy building!

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Design: The Tailgate / Platform

Tailgate / Platform

Tailgate / Platform

I have been investigating many different methods & materials to build the drop down platform. I haven’t decided which way to go yet, but I do know which way other camper manufacturers construct their drop down platforms.

First off, as you’d expect, most of them use aluminium. As far as the construction goes, this is usually an outside box frame with 4 or 5 internal supports, all made from 40mm aluminium box tube. Cover the frame with aluminium sheeting (tread plate or normal) at around 3mm thick, to act as the floor, you then have a sturdy platform to walk on. This seems like the common construction method and if you didn’t want to spend too much time figuring out the various load spans & ratings of other materials, I would recommend going with this approach.

Platform Box Frame

Platform Box Frame [+]

However, if you wanted to dig a little deeper into the engineering sides of things, I think there may be some improvements to be made here. According to my rough calculations, a box frame & sheet described as above would weigh around 35kg. That’s not terribly heavy, but if you were planning to manually lower & raise the platform yourself (like I am), plus have a storage box attached to the back, you may start to wonder whether you’ll need assistance from another person just to lower or raise it (not ideal in my opinion!).

Composite Panels

Composite Panels [+]

The box frame and aluminum sheet would both weigh around 15kg+ each. So I’ve looked at alternative flooring materials to compare the weight and performance (e.g. load spans) to that of aluminium sheet. Composite materials are of course available (at a price) but do offer many advantages (i.e. thermal breaks, etc). Some of the sheet/panels I’ve researched had high enough load ratings that you wouldn’t even need as much support underneath, which would save us considerable weight in the box frame itself also.

Here are a few of the flooring panels I’ve come across so far:

I’m currently still reviewing viable options & costs for the platform flooring material. If anyone has experience in this area or ideas that could help with the design & construction of this platform, please leave a comment!

Engineering Design
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Design: The Frame

Having more or less decided to stick to my 4th revision design from my previous post, here are some pictures of my first attempt at the tube frame design of the camper:

The frame is made from 25 x 25 x 1.6mm aluminium tube and the tube connectors are from Flexliner’s large range of various multi-direction/angle connectors.

You may note from the pictures, most of the connectors are black, these are normal nylon connectors whereas the green and red connectors would be the steel core & steel core with thread, respectively. I was thinking the threaded connectors (designed for feet, castors & the like) could possibly make for a good fastening point with the floor. For the floor I was thinking of 12mm marine plywood.

Drop Down Tailgate / Platform

Design Tailgate / Stairs - Potential stair and cable positioning.

Suspended Tailgate / Platform [+]

Unfortunately I have doubts whether I can use this type of framing system for the drop down tailgate/platform. The loads it would see could be up to 300kg (3 or 4 people) and without proper support underneath (as it will be suspended by cables) the frame would simply cave in on itself. I may need to look into a stronger (perhaps welded?) solution for this.

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Aluminium Framing: A new hope!

One thing that’s been on my mind for awhile is the Qubelok tubing which is only 1.2mm thick. We’re going to have some pretty decent stress loads on this frame with the drop down tailgate & the fold-over bed hinges, etc, which was always a bit of a concern for me.

On a visit to my local Aluminium supplier Aluminium Express, I noticed they also sold Qubelok connectors and something else there that caught my attention. They looked like extra long tube connectors and were more like nylon than plastic. I enquired about them and found that they are actually a different type of tube connector altogether and made by Flexliner!

Flexliner Connectors

Flexliner Connectors [+]

Flexliner’s tube connectors are longer and made for 25 x 25 x 1.6mm tubing which is a standard size, more readily available and cheaper than most Qubelok suppliers! They are made from a stiff (but flexible) nylon and are much more vibration & stress proof than Qubelok which can snap on corrugations, etc. They even have welded steel-core versions available for applications requiring a bit more compressive strength (click the photo to expand).

For me, this was an amazing & timely find that’ll provide that extra bit of security knowing the frame will be that little bit stronger being 1.6mm instead of 1.2mm.

As you would guess the connectors are a little bit more expensive. Qubelok connectors are around $2.50 each whereas these Flexliner ones are around $4~ each but I think it’s every bit worth it. Another big advantage is designing the frame in 25mm tube sections instead of 25.4mm!

Stay tuned for my tube frame designs coming soon…

Engineering Design
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Design: First drafts

Here are a few of my initial design concepts whipped up relatively quickly in Sketchup (3d design software).

These give us the general layout idea(s) and help alleviate any major design flaws at this early stage (before moving onto the frame design):

Once we get deeper into the design there will be a lot of issues to overcome. This has a lot to do with what parts we’ll be putting in (& where to fit them), such as water tanks/heaters, sinks, cookers, gas bottles, batteries, etc, which will likely change the dimensions of some of the storage areas, but you have to start somewhere!

Aside

A detailed look at construction: #2

I recently came across these photos 1 & 2 of the construction of a camper. You can see how the frames are constructed and wouldn’t you know it? They use Qubelok!

That means no welded frames, all plastic connector joins and the outside aluminium sheet/skin holds it all firmly together.

They’ve also managed to have the fibreglass lid (likely around 20~kg) attach to the frame with a piano hinge (aka continuous hinge) with seemingly no ill consequences (they’ve sold a lot of these units over the years).

Here are some of the construction features I’ve been able to determine from photos and other sources:

  • The Foldover Lid/Bed is a made from foam-cored fibreglass (Check out ATL Composites for some examples of foam core sandwich panels)
  • The upper tent is made from Billabong Dynaproofed 10.9oz canvas – (Wax Converters Textiles)
  • EPDM Rubber Sponge dust/weather seal is used for where the edges of the fibreglass lid and body of the camper meet when closed up.
  • The entire internal frame is made with Qubelok and if you look closely at the photos linked above, you’ll see the connectors are held in place by either rivets or clamped with a nail punch/pinching tool.
  • The benchtops act like large gussets for two of the corners and the other side has two small triangle shelves to strengthen those corners.
  • 100mm Aluminium ‘I’ Beams are used as the support base with a 12mm plywood floor.
  • You’ll also notice the thick aluminium angle on the inside edge of all 4 corners of the camper, allowing the bolts for the jacking points to go straight through, making for a stronger brace.

The other construction methods are fairly straight forward and can be determined from the various photos available online.

Next post will be about some of my early concepts of various Qubelok/Aluminium Frame camper designs. Happy building!

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Aluminium Framing

What are some aluminium framing methods?

During my research into ‘weldless’ aluminium framing methods I came across many techniques and products that could be used to build a camper. Some of which I have mentioned before but will repeat for completeness.

8020 Framing System

8020

8020

The most impressive would be the 8020 framing system which is basically extruded aluminium profiles that through the use of various fastening methods can be joined together to form a strong, vibration proof join in many different angles. The system is available from a few different suppliers under a few different names but they are essentially the same concept.

The pros:

  • Quick to assemble
  • Easy to use
  • Strong and Vibration Proof

The cons:

  • Price
  • Weight could be a factor, they would definitely weigh more than hollow square tubing

Gussets and Rivets

Gussets & Rivets

Gussets & Rivets [+]

Another method was that used on air plane fuselages. This uses mainly rivets and gussets to join tubing together. It’s an effective method of fabrication and relatively easy for the DIYer. This would probably be the cheapest method of fabricating an aluminium camper frame.

The pros:

  • Cheapest method I’ve found
  • Only basic tools needed

The cons:

  • The gussets may be in the way when installing walls, bench tops and cupboard doors.
  • Extra care/planning would be needed to ensure you don’t have gussets in the way of moving parts or where a nice flush finish is required.

Qubelok

Qubelok / Connect-It

Qubelok / Connect-It [+]

The easiest method I’ve come across so far is something called Qubelok or Connect-It depending on local suppliers. It’s a framing system that uses plastic connectors that slot into 25.4mm (1″) tubing. It is surprisingly strong, especially when building in cube-like structures. The plastic connectors are around $2 each and are available from 3 to 6 way connectors.

The pros:

  • Fairly cheap connectors
  • Easy to build (just hammer it together)
  • The Qubelok extruded tubing is available with an offset lip so you can mount bench tops or glass ‘flush’ within the frame (pretty cool actually)

The cons:

  • The aluminium tubing isn’t really a standard size and the anodized finish makes the price of tubing a little higher than you’d expect. Especially the lipped tubing.

A little more on these tube connectors

I wondered whether these plastic connectors would be strong enough for building a camper. Especially one like the Wedgetail or similar with the fold over lid.

Qubelok 4x4 Storage

Qubelok 4×4 Storage [+]

The Qubelok/Connect-It system is actually really popular in the 4x4ing and touring communities. They use them a lot to make slide out drawers and shelving for their camping and 4×4 equipment (fridges, cooking, winch gear, etc).

I’ve heard of a few reports though where these plastic connectors will crack over corrugations or if you put too much weight on them, which gave me a few concerns.

I pondered over this and thought that as long as you didn’t overly stress any particular join and if you reinforced some of the joins with gussets it may be the best of both worlds. (E.g. Easy to build & still strong)

So that’s where I’ve started. I would design a Wedgetail style camper out of Qubelok/Connect-It components and where I had to reinforce it I would use gussets.

On to the design!