How strong is an Aluminium Canopy?

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ThysdJ
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We have been asking this question for a long time now, and at the beginning of the year we decided that we are going to find out... And we did..

Here is how it went down...


Ever wonder about the structural strength of your aluminium canopy? Will it maintain its structural integrity in case of a roll-over? Well this weekend we incorporated an experiment into the first Dust Series Qualifier of 2019 to determine how long an all aluminium canopy will last when you drive huge 4x4 vehicles over it. Will the doors still open and close, will the windows pop out? Will the canopy collapse? Will we make complete fools of ourselves? Will there be a cold beer to celebrate afterwards? These were some of the questions in the forefront of the minds of our guys and the canopy manufacturer.

In order for the experiment to be successful we determined that only 1 or maybe 2 vehicles need to drive over the canopy without the structure collapsing. This would mean that more or less 2 rollovers should be survived.

So we went in search of an aluminium canopy manufacturer who would be brave enough to put their product up for this experiment. One of the bigger manufacturers were on board immediately with grand plans on how they will tackle the problem and even build custom ramps to make things easier for the vehicles to get up and down from the canopy. Unfortunately as the time grew nearer, it seems like doubts were creeping in and less than 2 weeks before the great event, they pulled out. This left us without a canopy, and the hunt for a new supplier began all over again.

This time we got hooked up with Juan Fouche from Razorback canopies. Juan was slightly apprehensive about our whole idea to start off with, but we reassured him that we will do a test before the day of the event as a "proof of concept". With that we got hold of some ramps, adjusted them to fit and we ran our test 1 day before the time. Juan was sent a video clip and he was satisfied we are not just messing around. For this test we used Charles Muller's very fine V8 Hilux D/C bakkie which weighs in at 2.3 tons! Relief all around, now we can let this concept loose on the masses out there!

How did we do it? Firstly we decided to focus on the canopy structure and not so much the roof skin. As the roof skin is only there to keep the rain off you luggage and not to support a bunch of weight, especially not concentrated weight like 2 wheels on an axle carrying more than 1 ton. That is a LOT of PSI right there concentrated on an area not much bigger that 2 (or maybe 4) hand palms. We eliminated that by letting the vehicle run on a set of fibreglass traction grids, slightly elevated (48mm) above the roof skin. To make sure the weight of the vehicle gets transfered to the sides, we bolted a 48mm thick beam along the length of the roof on both the entry and exit side, on which we rested the grids. That had the roof skin sorted.

As a further safety mechanism, we placed supports, in the form of wooden pallets, on the inside of the canopy leaving about 7cm of space between the inside of the roof and the top of the supports. This was done just in case the roof skin, or one (or both) of the grids collapse, and the vehicle falls into the canopy. With the supports in place the vehicle could still be driven off the canopy, without the need for heavy lifting equipment. The 7cm gap would still allow for some flex in the roofskin, and in our test this was also about the amount of flex the grids allowed.

Satisfied that we catered for a complete canopy failure and safe vehicle recovery we were ready for the big day.
The first "obstacle" of the day was a weigh bridge exercise. Every vehicle drove onto a mobile weight pad to detemine the weight on the front and rear axle and a combined mass. The drivers had no idea at the time what this was for, but we had a plan.
At the very last obstacle, the drivers were lined up to drive over the canopy, and as every vehicle passed over the makes, and combined mass was recorded on the roofskin of the canopy in black permanent marker. All the spectators were waiting in anticipation for a spectacular collapse as eavh vehicle drove up, and when Gert in his 3.1 ton Patrol pulled up everybody thought "This is it!!". But alas, it wasnt. The canopy lived on to fight another day.

After all the vehicles crossed over, and all the weights were recorded we tallied it up and came to the total of 35 tons. Juan decided that we should remove the top most pallets from the inside supports, increasing the gap between the roof and supports by 20cm. We called for volunteers to drive over and Kobus volunteered his 4.5 D/C Land Cruiser to do the final run. To everybody's surprise the canopy held up, and with the support of the grids, there was almost no difference in the amount of flex on the roof skin. But as they say in the classics, "prevention is better than getting a crane in".

After all was said and done, all the windows were still in tact, and the doors openend and closed as per usual. There were some scuff marks on the sides where the ramps rubbed against it, and the roofskin was slightly warped, but after enduring 36 tons that is to be expected. The rivets holding the roofskin in place were all still 100 in tact as well. The only other damage was the sealant between the roofskin and the frame. That was destroyed as it pulled loose. So maybe the canopy will be slightly leaky, but it is still structurally intact.

As a world first, we can proudly say that the Razorback canopy passed with flying colours. The experiment was a huge success. With these results one can safely prove that an aluminium canopy will perform the same and even better in a roll over than a roll bar. Obviously this depends greatly on the manner of fitment, so that it does not seperate from the vehicle, but with sturdy fitment with the proper brackets and nuts and bolts, it should stay in place.

So here we have proved beyond a shadow of a doubt that a Razorback Aluminium Canopy can withstand the forces of 15 vehicles and a combined mass of almost 36 tons driving over it without structural damage. With the heaviest vehicle weighing in at 3.1 tons.

Well done to everybody involved, from Razorback for the canopy, Massametric who supplied the weigh bridge, Burnco and Allbilt for the use of their ramps and then the Team Offroad team who tested and executed the experiment. We cannot thank you guys enough.

Somewhere I heard a little birdie whistle in my ear that we might do this again next year.. with a newer model canopy.... We will keep you guys posted.


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Thys de Jager
CEO and Refreshments Manager at Team Offroad.

2010 Hilux 3.0 D4D D/C 4x4 with GOMAD "Brood" Canopy. Tripod.
1997 Jeep Wrangler TJ 4.0 Sport. The original SFA. AGA... Gooi kole
email: thys@teamoffroad.co.za

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Because of it's light weight, one expects aluminium to be weak whereas it's a lot stronger than we sometimes think. I have for some years had a pair of sand tracks that are nothing more than a couple pieces of 6mm chequer plate and although admittedly have only had a few occasions to use them, they are still straight as a dye.

So ja, your experiment is interesting, but I would have to wonder what would happen in the case of a genuine roll-over where the stresses are not directly down on the canopy from above, but from the side as well. That said, there is no way a glass-fibre unit would fare as well, whatever the test.

Thanks for the post. :winkx:
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Interesting Thys, and certainly an eye-opener.

Well done to the test drivers, Team Off Road and most certainly Razorback, the Manufacturer of the ali canopy! I guess we all know which company to support when purchasing an ali canopy. :thumbup:


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Johan Kriel
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No doubt that alu canopies can and are strong enough. Metal fatigue is actual the issue with aluminum in the long run.

However SS canopies are not more heavier than alu canopies as it don't require a frame to provide structural strength.



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Dowe Koos
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Very interesting post, well done to all players.
Just want to say something of what Johan said. Anybody who had stainless steel trailer or canopy will in the long run find that it was never a good idea to have it. From my experience, I had see that under stress SS is really the worst of the three, meaning SS, aluminium and mild steel.
If I can find a sponsor to build a canopy like mine, I will do the same test as Thys has done without any support or help. Will only use the ramp to get the trucks over it. This is from my experience with mild steel frame and aluminium cladding. Only the basic " dop" had the same weight as a fiberglass canopy.
As Edge had said, Namib gee niks nie, hy vat net. Last year on that trip lot of things come loose or get crackings, but the canopy is still in good condition. Well everyone had it's own preferences.
Have a nice evening
Ecc 1:9 Wat gewees het, dit sal daar weer wees; en wat gebeur het, dit sal weer gebeur, en daar is glad niks nuuts onder die son nie.
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Dankie vir die interesante onderwerp en toetse wat ons nou meer op ons gemak sit in die type kappie.
Ek wil byvoeg, dat dit altyd my opinie was, dat die kappies nie almal ewe sterk gebou is nie,
dus het ek altyd voorgestel dat die kappies goed deurgekyk word, en die sterkste een te koop wat jy kry.
Die is vir al die goed wat op die dak gelaai word, son paneele ingesluit.
Dis reg Hennie, gee niks, maar vat net...
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Allie Smit
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Amazing post and test!! A friend of mine rolled his DCab, and the Alu Canopy saved some lives that day!
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Dit is nou baie interessant en 'n baie nuttige toets. Dankie vir die moeite.
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