Why do Volvo trucks have park brakes on the front axle? I have seen it on some other European trucks as well. On a tandem drive truck with three axles, they will have park brakes on the front steer axle, and the front-rear drive axle, but only service brakes on the rear-rear drive axle. It seems a bad idea to me because if you lose your air and your brakes come on, your front wheels will lock up and you can't steer. The other thing I am wondering is why the exhaust brake comes on automatically when the park brake is applied? There is an air pressure switch right by the park brake control which does nothing else apart from activate the exhaust brake. For the most part you would never notice, as you are not trying to drive the truck while the park brake is applied, you only notice if you try to rev up the engine while it is in neutral with the park brake on. I have disconnected the air pressure switch and now it just works with the foot switch on the floor as you would expect. But I am still wondering why it was supposed to do this?
My guess it is an EU directive of sorts, remember in Euro land most prime mover are single axle drive. I dare say that there might be a system that stops the front wheels from locking in case of drastic air loss.
Are the front axle "park" brakes air applied or spring applied? They sometimes put manually actuated, air applied holding brakes on the front of fire ladder trucks for better braking at the scene....
I don't think there is any system in place to stop the wheels from locking on. I was driving a Volvo N12 once and ran out of air, front brakes locked up and no steering. The F10 looks to be the same. They are spring applied, air release, park brakes.
This is applied automatically so when the engine is sitting there idling the engine brake applies some load resistance so the engine is less likely to glaze the bores. Even our later model FM12 and NH12 do the same thing.
Thanks for the reply, any ideas about the park brakes on the front axle?
In the U.K. and Europe the rear tag axle is a common feature also the mid lift axle, Foden trucks used to have 3 out of 4 axles on a rigid 8 wheeler fitted with spring brake packs, that is with no or low air 3 axles are locked up with springs, it was a big safety feature of this truck builder, the latest style is to have spring brakes to axles that are constantly in contact with the road surface with the ignition key turned off,giving the required park brake effect needed to hold the loaded vehical at the Design Weight of the truck, double drive tractor units are not the common set up only being used on heavy haul 80 ton (80'000kgs) upward or for rough site work as double drive is seen as double trouble and more cost and is not needed.
I've noticed all of our VOLVO trucks have what we call 'MAXI's' on the front drive axle and the front steer axle. All of our trucks are Bogie drive and are B-double rated....whether it's part of the heavy hauling they add them i'm unsure. I've always thought that if a 'Maxi' hose was to let go on the front steer it would pull the truck sideways without warning!
The ones I have seen are bogie drive rigid trucks, I can't comment on prime movers but from what you say sounds like they are the same. I haven't had a maxi hose let go on one front axle and I hope I never have to find out what its like if it does happen.
Both our Volvos, NL12 and F12 have maxi brakes on the front axles. We have never had a hose come off or blow on the road, but we have had them come off when we have been backing around in yards for tipping. It locks the front wheel up real quick. I have often wondered what would happen if a hose came off at 100 kmh, but I don't really want to find out. RnR.
Most people seem to agree that it is not a good design, others find it hard to believe that such a system even exists. But nobody has ever been able to tell me a reason for it.
What about calling back to France or wherever they are designed and seeing if you can get ahold of an engineer or somebody from the manufacturer? I have sometimes had success with this route when curious about a design.
This is mounted on the LHS mudguard, behind the front wheel, on a Volvo F10. Does anybody know what it is or what it does? It's empty. It seems to be something to do with the air compressor governor, but I can't work out what. Is it just yet another Volvo oddity?
Looks like a container you add brake line anti freeze to.
oarwhat, is correct it is a Methanol dose tank, this would contain an anti air freezing aid to keep the brake system from becoming ice bound in low temps.
No wonder it's empty in Australia ........ can't see much use for an anti-freezing additive in the air system down there....!!
I was starting to think that it may be a reservoir for plutonium to power the flux capacitor. But thankyou for putting me on the right track, I'll get some anti air freezing aid to try to stop the air from freezing. Frozen air has given a lot of trouble on this truck so it will be good to sort it out.
Well maybe I shouldn't say a lot of trouble, but a bit. Sometimes on a really frosty morning the air system acts a bit funny, and I had blamed it on a valve freezing because it comes good when it warms up. Methanol might help a bit but it is probably treating the effect and not the cause, most of the valves have a fair bit of gunk in them from not having the tanks drained often enough. Certainly won't be a problem for a while as we are just heading into summer. Thanks for the replies.
Does this thing have an air dryer? Here in California I have never had a lick of trouble (or drained a drop of water from the tanks) on a truck that had a good air dryer and a compressor that doesn't blow a ton of oil. It rains a fair bit here too, and it also freezes.
Our N10 behaved a little strange in the cooler weather aswell. The less moisture in the air system the better as it gums up valves etc. Our N10 would build up air but wouldn't engage the auxiliary's such as the Air throttle, clutch and gearbox....so she'd sit there for 40minutes until she got some heat into her before she decided it was time to go. and no they dont have Air dryers unfortunately....it's good practice to drain all the tanks every morning or afternoon to eliminate as much water as possible.
I was told in Bendix air brake school that it is basically water displacing the super expensive barium grease that comes in brake valves that causes them to fail, and that until that happens they can work basically forever. With any amount of water sloshing around in the tanks, you know that the system air has to be basically saturated with water which means that any point where it is a little bit colder, it will start condensing out and causing potential problems. With an air dryer, (and a good compressor not blowing oil) the air is so well dried that it will quickly pick up and dry out any leftover water in the system, and you will find nothing to drain in short order. I think retrofitting an air dryer is a good idea for any truck that you care about very much at all. I think alcohol evaporators went out of favor for other reasons too, such as interaction with the grease but mainly because compressors began to be turbo boosted.
Thanks for the replies, sounds like an air drier might be the way to go. Not so much of a problem coming into summer.
Maybe a little of topic. We run a bunch of old snowplows. We used to use alcohol to unfreeze air lines. It worked great but they froze up even more after that. I think the leftover alcohol attracts water like drygas would. An old timer told me to use regular green anti freeze and it work great on problem trucks. It must sit in the low spots in the line and prevent the water from freezing.
The only thing about the air dryer is it might need to be the "Discharge Line Unloader" type, DLU for short, as some of those European compressors have no unloaders in the head, instead they just dump the discharge pipe to atmosphere so the compressor is pumping at all times. For a Bendix air dryer this is accomplished by changing something in the purge valve, I think.
This one has a regular governor that unloads the compressor, like you would find on an American truck.