Crash Testing Beds

Crash Testing Beds

Rock and Roll bed safety: what is a “Pull Test”?

With the advent of the T4 and T5, driving a bus is no longer a matter of tootling around at 50mph. These are modern vehicles, capable of high motorway speeds and, as such, require seating that will save your life, if it ever comes to it.

It’s not just common sense telling us so. As of 2014, the department of transport has ruled that all seats in vehicles built after 2006 must at least be fitted with lap belts.

Tests, tests and more tests

The M1 pull test

With so many seat/beds on the market, from the well-known brands of Rib and Reimo, to new kids on the block like Smart beds, Bebbs and the Cambee Flex, it can be difficult for the humble bus owner to know where to begin. Let us offer you a hand: if you’re planning on having passengers use your seat/bed belts while the van is in motion, you should always start with the question: “is it tested?”.

Sure, this may sound simple enough, but with such a catalogue of test types, from sledge to in-vehicle crash tests and pull testing done with and without the use of a vehicle shell all used by manufacturers, it’s a question that needs better understanding.

The draw of the Pull Test

For the vast majority of the camper and motorhome market the Pull Test is the assessment of choice. Costing a fraction of the other tests, it lends itself to the ranks of manufacturers who can only expect to produce a relatively low volume of seats before new models of vehicle require a redesign and more testing.

The Pull Test is designed to prove that a seat can reach M1 standard, the measure set out by the European Union for passenger-carrying vehicles with no more than 8 seats. Other standards include M2, N1 and N2 and vary as to loads used and function of the vehicle. Legally, all of the seats used while the van is in motion must be tested to this standard, single passenger swivel, R & R or otherwise.

In the simplest terms, the M1 pull test simulates a crash at 30mph into solid concrete, pulling the seat with the resulting force of such a collision: 3 tonnes per passenger for 0.2 of a second.

So, how does it work?

Before the test can be carried out, a seatbelt position test using an SAE ‘manikin’ determines whether the seat belt fixing points are in the correct positions in relation to an adult’s hips and shoulders. This helps to reduce the risk of spinal and pelvic damage in an accident and is a paramount part of the test, given the regularity in high-speed collisions of pelvic fractures and bleeds with a real risk of fatality.

Once the Cambee Flex’s easy-fit subframe is secured to the rig, the double seat is pre-tensioned and pulled for a total of just over 3 seconds to ensure that the rig is fully straining all components of the bed i.e. the seat anchorage and head restraints and anchorages of seatbelts. The total load used amounts to an unforgiving 7 tons (6 tons for the two passengers combined with a multiple of the weight of the seat).

For the Pull Test proper, the seat can either be mounted inside a vehicle shell (an “in-vehicle test) or fixed to a “rigid structure” or “frame”, usually the base of the test rig, as shown here with Cambee’s two seat “Double’ and three seat “Triple” beds being carried out at STATUS (Specialist Transport Advisory & Testing Utility Society).

Rigid frame vs in-vehicle testing

While a “rigid frame” Pull Test (the most commonly used) assesses the strength of the seat frame and belt mounting points, it does not, like a crash test (where a van is physically made to collide with a surface at a set speed), put the bed through all the variables of a real crash. Nor, as an in-vehicle Pull Test, does it determine the strength of the mechanism attaching the bed to the chassis.

Current legislation states that only seats fitted to brand new, unregistered campers need to have passed an in-vehicle test. For vans that are already registered and issued with a number plate no testing is required by law (but seats must at least have lap belts fitted).

It’s up to you to decide whether you can live with this. For most, the rigid frame Pull Test suffices: the frame and belts have shown they can withstand the exertion of 3 tonnes per passenger and many companies, though they don’t have the means to prove its effectiveness, go to great lengths to attach their beds to the van, which it’s worth asking them about.

n.b. It’s also worth noting that even if a bed or car seat is sled or crash-tested it will still need to face the Pull Test to be certified “safe”, so these always provide the final stamp of approval.

If at first you don’t succeed…

The Pull Test doesn’t always go to plan, especially if, like Cambee, you’re trying to keep the weight of your bed to a minimum. As the wise old saying goes, a chain is only as strong as its weakest link. During our first attempt, the chink in our armour was the buckle mount:

Matt says: “ it was a real gut wrenching moment to see the bed fail, but it was important to us that we didn’t just throw loads of metal at the bed to ensure it passed. This was to keep weight down but also to ensure that the bed has some flex, so that it soaks up some of the shock of an accident”.

Fortunately for us, the second round of testing was a success for both the “Double” and “Triple” seats. Read more about our design here.

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