Caravan MOTs......... maybe?
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I'm still struggling to understand this. If as said they move the rollers forward (in effect the whole caravan) as the brakes apply what's to stop the caravan climbing out the rollers which counteracts what was being done to apply the brakes in the first place. The natural reaction when a brake is being applied when roller tested is to climb the driven roller at the rear of the wheel throwing the vehicle out backwards, this is why in some cases you see the operator put a chock behind one of the front wheels when testing the rear brakes.
Is there any more info available about the machine used Lutz ?
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Not when I used to do it DD, admittedly it was Trucks, Buses and Coaches.
Found these pictures of equipment made by VLT. both moving the coupling and rollers remain stationary.
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Some 13 years ago as a special contsable I jumped at the chance as a caravaner to take part in a spot check of caravans pulling into a motorway service area to be cheked over and advice given, drivers were asked to apply the caravan handbrake and then pull away and a few did with ease and the state of some the tyres! others were asked to adjust the loading of their caravans these of course were not allowed to procede till they were rectified. I would like to think things have vastly improved since then
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Thanks to Lutz for the post but, like Milo, I'm struggling to understand what the described method proves.
Milo's photographed system is what I envisaged, but didn’t know existed, and it is controllable.
It would appear that German test rigs are different to the UK variety as our brake test rigs are not normally drive through and have fixed rollers. Our test stations are privately owned and run with many in small workshop units.
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I'm still wondering how a caravan is issued with a pass (not just given a certificate) and how is it enforced? We have number plate recognition, are all caravans over there all recorded and identified, is it just a case of check points?
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No, I don’t believe it does fully test the braking system but I’m willing to be proved wrong.
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Have to agree, to my mind caravans are not that heavy and as I said the rollers will start to move the caravan backwards counteracting the action described, thus reducing the barking force applied.
Only way I can see it giving read out of braking force as a percentage of the vehicles weight (same as cars etc are tested) is to temporarily secure the caravan in the rollers by some means. This is the same principle that i stated earlier for HGV's where they are artificially loaded or tested physically loaded, at the very least, chocks placed behind wheels not being tested to keep the axle being tested in the rollers to prevent vehicle movement,
As a further point of interest what is the pass % criteria ?. to generalize service brakes in the UK have to be 50 or 58% or more, efficient, dependent on vehicle age, it gets a little more complicated for park brakes and secondary system (half of your dual circuit system)
Interesting thread
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I'm guessing here goes - the German rig appears to have van hitched, so as the rollers are run and moved forward the overun activates. Or possibly the hitch rig pushes on the overun plus there's probably a sensor in the hitch part of the rig so they can measure overun force vs brake efficiency.
Much needed with the Alko brakes fiasco. If you're van is 2017 onwards and brakes squeal you probably have severly scored drums = low brake efficiency. I had 2 sets of drums and 4 sets of shoes in the last year!!!
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Ah found this on vlt website
overrun-brake-simulator overrun-brake-simulator
The original Caravan Roller Brake SimulatorThe VLT Caravan Roller Brake Simulator operates the brake mechanism on the triangle of the caravan. The Brake Simulator also holds the caravan in the roller sets of the Brake Tester.
The mechanism in the Brake Simulator, which is activated by hand, causes force through the coupling device on the overrun brake. This force is measured with a gauge and is displayed on the LED display of the Roller Brake Tester0 -
You seem to think you know more than Milo, MM and I so prove me/us wrong by contributing something positive.
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What? Three of us have doubted the ability of the scheme described by Lutz to test braking efficiency. I named those three.
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Your close up picture backs up what I have said. It appears from the photo that the A frame is chained to the testing machine to stop the caravan climbing backwards out the rollers as the coupling is pushed inwards to apply the brakes.
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I said it made sense when Milo posted it on page 7……
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You’re very transparent, DD. Cop out🤣🤣🤣🤣
I think you’ve overlooked the fact that the VLT is not what Lutz described.
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For the last few pages we, and that includes you, have been debating how the system in Germany can test over-run brakes.
With regards to the OP who essentially asks if we are heading towards caravan MOTs and is it time we should, then no I don't think so. As somebody else suggested, more emphasis should be given to publicising the law with regard to driving licences, legal weight limits and so on.
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............. maybe