Stephenjp:
An easy visual guide I use, are the front spray/mud flaps, if you can get your foot between them and the road surface, your generally ok, if not its more than likely overloaded!!
Are you sending this from 1976?
switchlogic:
Stephenjp:
An easy visual guide I use, are the front spray/mud flaps, if you can get your foot between them and the road surface, your generally ok, if not its more than likely overloaded!!Are you sending this from 1976?
Eerm well no…
I was still at school then, It was just from my experience driving 18 tonners and now a 26 tonner, my 26 tonner has a pto compressor fitted which adds more weight on the front axle!!!
justpassing:
Carryfast:
Franglais:
Carryfast:
Feel free to explain the supposed mechanics which make air suspension any different to steel in that regard.If it reduces air on axle 3 that obviously lifts even more weight off the steer axle and overloads axle 2.If it reduces air on axle 2 that obviously then overloads axle 3.
The fact is axle 2 or axle 3 can be the relative load pivot points affecting steer axle weight either way.6 wheelers are always flawed in that regard it’s why the 8 wheeler was invented.Preferably with longer wheelbase than shorter.(I`m gonna regret this)
Putting it very simply*.…On a 26T truck the rear axles will have different ratings.
Often, it is a single drive axle, with twin wheels, and a trailing axle (possibly steered) with single wheels.
Just going with that, the drive might be rated 10T and the other axle 8T.
The weight distribution between the two axles is not done through fancy control methods, just by the design of the suspension. With a constant pressure of air in the bags, the size of the bag (specifically the cross sectional area) affects the amount of weight that pushes onto the road.Think of an hydraulic jack: the pressure in the little tube you pump is the same as the wider tube that raises the vehicle. You push down at 50kgs onto a small cylinder to raise a 5,000kg axle on a wider cylinder.
So with air suspension for a given pressure if the cross section of an air bag is 10 units and another is 8 units then one will transmit 10 units of weight, t`other will transmit 8 units of weight.
Unlike mechanical springs the amount of weight transmitted through an air spring, is not dependent upon the deflection of that spring. That is why air suspension is “road friendly” and so higher weights are permitted.
The air in axles 2 and 3 is at the same pressure. Even if on uneven ground the relative loading of the two axles retains the same differential. (10 units and 8 units). The quantity of air will change between the two axles, but not the pressure**.
*I know I`m being naughty in not talking about masses, normal reactions, etc, just calling it all “weight”.
** In a stable situation. In a dynamic situation it is indeed the pressure difference (caused by moving over bumps) that causes air to move between axles.None of which makes any difference whatsoever to the fact that weight placed behind axle 2 but forward of axle 3 still lifts weight from the steer axle either way.
Here we go boys CF theory of relativity on axle loads time to bale out
[emoji1787][emoji1787][emoji1787]
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Carryfast:
Franglais:
Carryfast:
Feel free to explain the supposed mechanics which make air suspension any different to steel in that regard.If it reduces air on axle 3 that obviously lifts even more weight off the steer axle and overloads axle 2.If it reduces air on axle 2 that obviously then overloads axle 3.
The fact is axle 2 or axle 3 can be the relative load pivot points affecting steer axle weight either way.6 wheelers are always flawed in that regard it’s why the 8 wheeler was invented.Preferably with longer wheelbase than shorter.(I`m gonna regret this)
Putting it very simply*.…On a 26T truck the rear axles will have different ratings.
Often, it is a single drive axle, with twin wheels, and a trailing axle (possibly steered) with single wheels.
Just going with that, the drive might be rated 10T and the other axle 8T.
The weight distribution between the two axles is not done through fancy control methods, just by the design of the suspension. With a constant pressure of air in the bags, the size of the bag (specifically the cross sectional area) affects the amount of weight that pushes onto the road.Think of an hydraulic jack: the pressure in the little tube you pump is the same as the wider tube that raises the vehicle. You push down at 50kgs onto a small cylinder to raise a 5,000kg axle on a wider cylinder.
So with air suspension for a given pressure if the cross section of an air bag is 10 units and another is 8 units then one will transmit 10 units of weight, t`other will transmit 8 units of weight.
Unlike mechanical springs the amount of weight transmitted through an air spring, is not dependent upon the deflection of that spring. That is why air suspension is “road friendly” and so higher weights are permitted.
The air in axles 2 and 3 is at the same pressure. Even if on uneven ground the relative loading of the two axles retains the same differential. (10 units and 8 units). The quantity of air will change between the two axles, but not the pressure**.
*I know I`m being naughty in not talking about masses, normal reactions, etc, just calling it all “weight”.
** In a stable situation. In a dynamic situation it is indeed the pressure difference (caused by moving over bumps) that causes air to move between axles.None of which makes any difference whatsoever to the fact that weight placed behind axle 2 but forward of axle 3 still lifts weight from the steer axle either way.
That’s not a fact, with compensating axles you just have a theoretical point of the bogie.
For weight calculation you basically treat it like 1 axle and depending on several factors it could be anywhere from in the middle of the 2 axles or close to 1 of them.
That is why on a midlift unit, sliding the 5th wheel forward from the middle of the 2 axles, so closer to the centre of the midlift, will actually reduced the weight on the midlift and drive axle and increase it on the steer
Did similar in a 26 tonne curtainsider on Forfarmers, loading powdered milk pallets which weighed 1250 kg each. As the load bed was configured for 14 standard 1 tonne pallets of feed, we used to put two stacks of pallets up as a dummy headboard to keep the weight back. The milk powder pallets were slightly wider than a standard 1200 x 1000 so we could only get ten on, and it weighed out just under 26000 with the Moffett on.