Air Brakes and 7.5 tonne entitlement

Do air brakes work differently to hydraulic, other than pumping on compressed air rather than using fluid from a reservoir? And why do they feel the way that they do, compared to a hydraulic system on a car or bike?

I rented a DAF LF 45 7.5 tonne like this when I moved house



First vehicle I've driven with air brakes, and when empty the brake pedal just felt completely solid and unresponsive compared to a car, and with car amounts of pressure the truck didn't slow down at all, when you gave the pedal some more shove, it seemed to give way under your foot and start to depress more easily, then the truck suddenly stood on it's nose and tried to send you through the windscreen. I managed to drive smoothly once I'd got used to them by applying a lot of inital pressure to get the pedal to depress and get over that solid feeling, but backing off once they started to work and readjusting pressure according to how quickly I wanted to slow down.

When fully loaded they made more sense and you could feel what the brakes were doing a bit better, but I'll never pull out in front of a truck again 'cos they can't stop particularly quickly and need a lot of forward planning.

Why do they have air brakes? I understand it's easiler to engineer to get air pressure to a trailer than hydraulics, but this is a fixed bed. Why would a hydraulic assisted system not work?

The whole vehicle took some getting used to, but the brakes took more time than anything else. After a weekend I was managing with it no bother, but I'm usually quite good with that kind of thing, I was smooth and controlled with an excavator after few hours practice, but plenty of drivers who have 7.5 tonne entitlement on their licenses can just go and rent one of these things and would be a complete liability. Driving one made me think it should really require some HGV training and a test to get the entitlement.

[yorkie_chris]

Ready supply of compressed air from a diesel engine perhaps, many diesels bleed air from the cylinders to aid engine braking.

[timwilky]

firstly brakes.

Many types of operation. spring operated using air pressure to hold the brakes off. That way should their be a leak/loss of air pressure the brakes come on.

Air over hydraulic, vacuum, etc.

I have been out of truck braking systems since I left Leyland trucks 25 years ago, but before that spent plenty of type testing them. S cam operation where a cam would be rotated by an air actuator to force the shoes apart, wedge operation. Pull rods from air cylinders all sorts of simple mechanisms.

All the trucks we built had separate engine mounted compressors to fill the tanks. permanently operated with blow off valves when the tanks were full.

Generally air braking systems are very efficient, but do lack the "feel" a car driver would get from s simple hydraulic system. You need the extra force air pressure will apply in order to make the damm things stop. It isn't like driving a car.

the C1+E is going to get very messy in the near future when they start treating it like a HGV entitlement and you will have to renew every 5 years or loose it.

AS for driving under this entitlement. It is easy. Then again I had an old fashioned class1 when I was 21 but surrendered it rather than renew with all the medical agro that went with it. as I hadn't driven under that entitlement for 25 years.

Most rental firms now won't rent anything over 3.5tonnes to private people (for moving house etc etc), without seeing a Vehicle Operators licence, and proof of commercial vehicle insurance. Ie- you have to be running a trucking firm now, before you can even hire a 7.5tonne truck. Trucking firms can hire trucks, then add them to their policy on a daily basis...

It's all to do with insurance, tachograpgh laws, and so forth. If you hire a vehicle with a digitach tachograph, it must be used by someone who has a truck digicard for tachograph purposes. Even the trucks with the analogue tachos fitted must be used with a paper chart for the day... You try and explain all the tacho rules to a private punter who only wants a truck for a day. Too much hassle nowadays. 3.5tonner non tacho that's your whack now..

The most you can hire now on a car licence is a 3.5tonner ford transit or similiar..

The good days of hiring the big toys 7.5tonners, then driving them without a tacho for private usage, and not requiring a speed limiter set to 56mph are long gone.....

Originally Posted by -Ralph-

Do air brakes work differently to hydraulic, other than pumping on compressed air rather than using fluid from a reservoir? And why do they feel the way that they do, compared to a hydraulic system on a car or bike?

I rented a DAF LF 45 7.5 tonne like this when I moved house



First vehicle I've driven with air brakes, and when empty the brake pedal just felt completely solid and unresponsive compared to a car, and with car amounts of pressure the truck didn't slow down at all, when you gave the pedal some more shove, it seemed to give way under your foot and start to depress more easily, then the truck suddenly stood on it's nose and tried to send you through the windscreen. I managed to drive smoothly once I'd got used to them by applying a lot of inital pressure to get the pedal to depress and get over that solid feeling, but backing off once they started to work and readjusting pressure according to how quickly I wanted to slow down.

When fully loaded they made more sense and you could feel what the brakes were doing a bit better, but I'll never pull out in front of a truck again 'cos they can't stop particularly quickly and need a lot of forward planning.

Why do they have air brakes? I understand it's easiler to engineer to get air pressure to a trailer than hydraulics, but this is a fixed bed. Why would a hydraulic assisted system not work?

The whole vehicle took some getting used to, but the brakes took more time than anything else. After a weekend I was managing with it no bother, but I'm usually quite good with that kind of thing, I was smooth and controlled with an excavator after few hours practice, but plenty of drivers who have 7.5 tonne entitlement on their licenses can just go and rent one of these things and would be a complete liability. Driving one made me think it should really require some HGV training and a test to get the entitlement.

People were hiring these things, never having driven them before, and causing accidents, bringing them back with damages, etc etc. Thats why they don't hire them out to non commercial people nowadays.

The C1+E entitlements now are treated as HGV entitlements, and you now need to get a medical, theory and practical test before you can get a C1, or even a D1 (Minibus - vehicle with anything over 8 seats).

Yes - when 7.5tonners are empty, they fly on (or they did before speed limiters were forced onto them in 2005), (they used to be able to sit all day at 80+mph on the night shifts down the motorway)and the air brakes don't work quite as well when empty compared to fully laden.. You need to adjust your driving style, and think truck, not car or van....

I take it you did use the tacho when you hiring that DAF Ralph???

Originally Posted by jimmy4237

Thats why they don't hire them out to non commercial people nowadays.

I take it you did use the tacho when you hiring that DAF Ralph???

I'm not commercial, but I hired from these guys in April this year

http://www.thomassgroup.com/selfDrive2.php

I didn't use the tacho, they didn't ask me to and I wouldn't know how. They did ask if the truck was to be used for commercial purposes in which case I would need an operators license, but since it was for a house move the were happy with my standard C1 entitlement. I can see how private people have accidents with these things though, but I couldn't have done my house move with anything smaller and two trips in a Luton van from Scotland to Birmingham would have been a complete ball ache, so I'm glad I have the entitlement and the truck was available. I moved in a 750 mile return trip for about 350 quid including diesel, can't get that price from Pickfords!!

Surely no need for tacho when its personal use. Its only hire or reward. Horse boxes have tachos, and the original K seal must be in place and undamaged but they dont need regular calibration and they dont need to use tacho discs, same would apply to a truck hired for personal use

It is all getting very strange.

Mind you, I borrowed a 7.5ton Ford cargo horsebox years ago, it was bad enough getting used to the airbrakes (nothing, nothing, nothing, full brakes) but NO power steering!

My mum and her husband hired two of these for their move to Scotland, Mum normally drives a Mini Cooper, respect is due!

you can get 3.5 tonners almost the same lenghth thoh

Originally Posted by blue curvy jester

you can get 3.5 tonners almost the same lenghth thoh

That's good to know, which makes/models? Can you post a picture of one?