Myth or Fact - Air Tanks?

OK wise ones
I was recently told that B models and possibly others of that vintage had to have two separate air tanks for the brake system. Was something to do with the Truckies blockade on the Razorback many years ago.
Myth or Fact?

Well modern trucks have at least 4 air tanks or compartments in the air system. Count the number of drain cocks and that will tell you. There is the wet tank, first from the compressor which gets most of the oil and water, then one for front and one for rear brakes ( the dash gauges refer to these tanks ) and another "service" tank which works the air clutch, range change, air horn and other bits. Because that last tank doesnt usually have a gauge or buzzer the pressure can be low there and the truck will start acting up ie defaults to high range and power clutch wont work.
Dont know much about the B61, Swishy or Baz should be able to tell us.

Even my old 1954 Thornycroft with full air brakes has two tanks. Similar reasons as what atkipete mentions.

First tank gets the "Wet" air and runs at high pressure. This then goes through a pressure reducer to the second tank where the brakes are plumbed into.

This I assume would have been done due to the small capacity of the engine driven compressor so as to assure plenty of air in the tank for muliple applications if needed.

I also assume that the B models would run a similar system first tank high pressure. Then a reduced pressure tank for the actual brake systems etc. Especailly for those running air starts. But again Swishy and the other Mack guys would be able to clarify.

Don't know anything about a blockade creating this situation!

Howdy,

The B61 was a single circut brake system with I think only the one tank for the braking circut. The air start tank was a seperate affair.
I went and had a look at the R700 and it only has the one big service tank and the seperate air start tank.
Gearbox, honker, wipers etc come of the service tank also.
There is no connection from the air start tank to the service system for backup either.
What is the differance between maxi's and the normal garden variety 30/30 spring brake ?...or is there no difference.

Basil

So how do you charge the air start tank?

After starting do you need to remember to recharge the tank prior to switching over to the main air tank?

Could be very embaressing if you forgot to recharge the air start!

So how do you charge the air start tank?

After starting do you need to remember to recharge the tank prior to switching over to the main air tank?

Could be very embaressing if you forgot to recharge the air start!

Ok. My air start tank normally holds about 120psi. The other service tank bleeds slowly down to zero psi over time.
Being on a separate circuit (ie there is a ONE WAY VALVE that allows air from the service tank to the air start tank)
So immediately after engine start, the air start tank will have dropped to about 100-110psi, the service tank is zero psi.
With my system, once the engine is started, obviously the compressor pumps air into the single tank that provides air pressure to everything.
This will be pressurised until it is equal with the pressure in the air start tank - the one way valve opens and then BOTH tanks increase to approx 120psi. You can actually see the air pressure gauge slow down when this valve opens.
Clear as....

Yep same as how the R700 is setup. Check valves on inlet to service tank and the start tank.
The 190 has dual circut and when one tank is lower than other it fills until pressure in both tanks reaches equilibrium then the gauge climb slows down as both fill.
Same as what ya described.
Air system in 190 is out of an ACCO. 4 Tanks, front and rear service, wet tank and cling on things tank, honker, clutch, gearbox and fan clutch etc.

Basil

HeyRodMan
GuddayM8

sum good advice from up above

Az I no it
Wet tank, Truck brake tank, Trailer brake tank, Emergency brake release tank, Air start tank (when applicable)
they fill in th@ order
have also seen mack with air start th@ used the air start tank as a normal type air tank n @ the end of each day U swithed the air start tank off so it kept air for the next start n when started U flick it back over to anormal used tank
{me thinks they used this idea to cut down on weight n plumbing also less area taken up on a short wheelbase truck
ButEyeDoSt&2BCorrected!
cya


[ch9787]

Another dumb question. On these modern prime movers ie without a trailer brake handle, how do you know when picking up a trailer if the brakes are working properly ?
When I would pick up a trailer, would always do the tug test and then at low speed see if I could pull it up with the trailer brake alone.
Otherwise the trailer brakes can be right out of adjustment and you wont find out till you have to stop in a hurry.

Maybe this should be in the modern truck section, must be someone out there knows more about this than I do.