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The testing machines test each wheel individually, so they can do a pretty good job of working out if the vehicle is going to slew sideways, lock the rear wheels or demonstrate other poor behaviour under brakes.
Have a look at this as an example - [ame=http://www.youtube.com/watch?v=TSPMYP2Mdiw]Platetronic SafeTstop - YouTube[/ame]
In under a minute you get vehicle weight, mass distribution, brake force distribution, shock absorber condition and a handbrake force test.
It seems (according to Miraz above) that there are specific brake testing rolling roads. In relation to the coasting to a stop, I think you will find that is the momentum of the rolling road rollers and vehicle running gear momentum not the momentum of the vehicle itself.Quote:
Originally Posted by Ratel10mm
The vehicle momentum will involve factors like vehicle gross mass and centre of gravity (incluning it's tendency to roll over). It is this last factor that is important for significantly lifted vehicles, if the braking line is not straight ahead then the momentum may be turned into a force rolling the vehicle over.
There are several types of machines
- The plate type devices use the momentum of the vehicle, it doesn't need to be moving quickly 5-10km/h is enough to assess the weight transfer under braking
- There are powered roller dynos with electrical motors turning the rollers that simulate the inertia of the vehicle
- At the top of the scale are inertia brake dynos that spin up big lumps of metal attached to the rollers to simulate the inertia of the vehicle.
None of the ADR tests include any swerve or vehicle dynamics validation! But it would seem sensible to consider some consideration of the relationship between CoG, Roll Center and Roll Resistance in the suspension design with some sort of validation test.
The ACT RTA have used a rolling road to test brakes for a very long time. I can remember when I first came to the ACT in 1990 having to take my Series 3 in for its roadworthy and being concerned about passing the brake test - put it on the machine and watched the numbers come up with the brakes applied - passed with acceptable force and even relatively consistent across all four wheels and here was me think the series 3 brakes were not good. The handbrake even passed with flying colours.
This was 23 years ago and the machine had been there a long time then.
Garry
The RTA mermaids have brake testing rollers in their scale trailers, but they only test the efficiency of each of the brakes at relatively low speeds, not any of the momentum related effects of vehicle dynamics under high speed braking.
The Council of Motoring Clubs (veteran, vintage and classic vehicles) is concerned that under the current testing many of the vehicles will not be able to get to the speed required for the test. The sensible test would be something like 80% or the particular vehicle's V-Max, even if the VMax is only 80KPH i.e. the brake test at 64KPH.
Remember this is the same RTA, that wants (wanted) to consider a replacement body fitted onto 1920 Chev, because the original had wood worm, as a new individually constructed vehicle and have to comply with 2013 ADR.
You can use a set of rollers to simulate the higher speed behaviour relatively easily - about the only thing that you can't do is high temperature fade testing.
The test speeds are all capped at 80% of the maximum vehicle speed - even in the ADR's - the main concern that we have for historic vehicles is the attempt to retrofit current fade performance tests onto all modified vehicles.
Sometimes it's best not to tell them, if possible . . .Quote:
Originally Posted by Lotz-A-Landies
A 1920 Chevrolet ? a 490 model :) predating a Superior K, Ooh! it would give the RTA blokes something to think about,2 wheel brakes (rear) contracting bands :eek: they were only ever designed to slow the vehicle down and the hand brake used to stop it.
The neighbour has one up on the farm,his grandfather bought it new in 1923 a buckboard ute 1/4 eliptic springs,and it has not been a non-goer,on full rego he now uses it to go and get the Sunday papers.
We took it to the Nambour Swap a few years ago,up the Bruce Highway @ 28 miles per hour lovely.
Maybe we need to get Roothy and 4wd Action Magazine to organise a protest on this issue.
:Rolling::Rolling::Rolling::clap2: