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Old 2nd March 2013, 18:25   #16
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Default Re: How do Multi-axle Trucks Turn?

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Originally Posted by norhog View Post
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I guess these trucks and now multi axel volvo buses will be laying down some rubber on our ghats.
If you have differential in non-steerable axle, there will be no additional wear. But in case if the truck or bus is with non-steerable rear axle, you will have more tyre wear.

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Originally Posted by dhawcash View Post
..
Also, You must have noticed Multi axle Tata trucks which have 4 axles in total. The second one- right behind the front axle is supported on air springs and can be raised or lowered depending on the vehicle load. Guess how this one steers?

It has no direct connection with the steering wheel, and is supported on follower wheels- much like a wheel-chair's front wheels - so they turn to follow the trajectory of the front wheels. Some trucks in which this axle cannot be raised, have the second axle connected to the steering system as well.
These are the same front axles (with same axle arm, king pin, axle beam etc,) but there will be a stopper and due to which it can't be steered. Also since this is freely supported you can note that even during straight line coasting, the tyres will somewhat have a move in a zigzag manner.

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Originally Posted by dhawcash View Post
..
While searching for an image, i came across this tata truck which has the follower wheel arrangement in the rear most axle. As you can see the axle is raised above ground and seems to be turned slightly- that is because its not connected to the steering mechanism and will follow the axle in front of it by design when it is lowered. Also notice that the steerable last axle is only a helper axle. the main heavy duty axles still dont have steering to keep costs and reliability in check.
37T has two types of arrangement. Tata has a tag lift axle and AL has a pusher lift axle. Both are not steerable. I think Tata will have additional advantage of reduced tyre wear.
How do Multi-axle Trucks Turn?-371804.jpg

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Originally Posted by norhog View Post
...I saw some kind of hydraulic Ram connected to the second axel from front on a Ashok Leyland truck. Also the Ashok Leyland system has leaf springs and not air bellows as in case with TATA. Another point here since the second axel being a follower, during reversing it needs to be lifted up or some other thing is at play here??
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Originally Posted by silversteed View Post
...... AFAIK, the lift axle is lowered automatically when the GVW exceeds some limit (not sure if it was 19T or 21T). While reversing, this axle has to be lifted, or else they drag and make it difficult. Since haulage trucks don't have to reverse very often, truckers live with this handicap to enjoy the savings in terms of tyre wear when the truck is not loaded.
The axle lifting is auto when the GVW is less than 25T.
Also during reversing its obviously necessary to lift the axle. If not the truck will only drag and will not steer.This feature is present and truckers need not compromise. Plz note haulage trucks will have to reverse more often than passenger cars every now and then when they are to be parked / unloaded.

Also there is no marked improvement in tyre performance in case of lift axle. The tyre saved during lifting is compromised with the additional wear during running. The proven advantage is improved fuel performance when the return load is empty.

Quote:
Originally Posted by dhawcash View Post
Im not too sure about the hydraulic ram thing in ashok leyland- maybe they implemented hydraulics to steer the axle. But in tata trucks with the follower wheel arrangement, there is a spring and damper attached to the wheels to keep them from dangling here and there while raised.
Quote:
Originally Posted by silversteed View Post
All trucks use hydraulic power steering, hence what you are referring to might belong to the PS system.
The hydraulic ram connects two front axle steering knuckle / track rod and facilitates steering. The two front axles will turn equally and hydraulic ram does this job.
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Old 2nd March 2013, 23:01   #17
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Default Re: How do Multi-axle Trucks Turn?

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Originally Posted by Ashley2 View Post
37T has two types of arrangement...Tata has a tag lift axle and AL has a pusher lift axle. Both are not steerable. I think Tata will have additional advantage of reduced tyre wear.
What about the AMW? And, what is the weight at which the lift axle is automatically lowered?


OT: Is the AL 3718/23 available commercially?
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Old 2nd March 2013, 23:16   #18
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Default Re: How do Multi-axle Trucks Turn?

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Originally Posted by silversteed View Post
OT: Is the AL 3718/23 available commercially?
AL 3718il has been commercially launched recently and few trucks have been delivered. Refer the below link:
http://www.team-bhp.com/forum/commer...gid-truck.html
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Old 3rd March 2013, 10:09   #19
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Default Re: How do Multi-axle Trucks Turn?

I know this question is about multi axle buses, but is there a steering mechanism in the volvo "PX" series rear axle? Also the extra axle in the 9400xl can be lifted when the bus is not loaded. However I haven't seen a single bus till date whose extra axle has been lifted.

Also what is the steering mechanism in the vestibuled bus run by BMTC?
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Old 3rd March 2013, 11:29   #20
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Default Re: How do Multi-axle Trucks Turn?

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Originally Posted by silversteed View Post
What about the AMW? And, what is the weight at which the lift axle is automatically lowered?
AMW mechanism is like AL only and its still not in market.
The problem for AMW is still they don't sell in sizeable numbers in rigid haul models. Their 31T itself is yet to see limelight.

Quote:
Originally Posted by audioholic View Post
I know this question is about multi axle buses, but is there a steering mechanism in the volvo "PX" series rear axle? Also the extra axle in the 9400xl can be lifted when the bus is not loaded. However I haven't seen a single bus till date whose extra axle has been lifted.

Also what is the steering mechanism in the vestibuled bus run by BMTC?
The rear most axle in 9400PX steerable. Pusher axle in 9400XL can't be lifted but the bellow pressure can be reduced.

AL Vestibule buses have linkage mechanism from vestibule coupling connected to the rear axle. This linkage in turn connects to track rod and hence it steers.
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