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Old 18th October 2010, 21:12   #91
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Originally Posted by Sutripta View Post
Thanks. If the diagram had been rotated slightly so that the input and output shafts were horizontal, I think people would more easily equate it to the gearbox, and differential, and the connecting shaft to the propeller shaft.
Dada, here it is!Driving all four wheels: how is it done?-1.jpg

Spike
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Old 18th October 2010, 21:33   #92
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^^^
Fast work. Thanks.

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Sutripta
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Old 18th October 2010, 23:12   #93
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Originally Posted by sudev View Post
Should we not delve in to connection between gear box and differential?
Thanks, Spike - simple and crystal clear diagram of the U-joint setup. Any other types of connection apart from this?

Now, what's next? Subject to Sutripta-da's approval, may I suggest...
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...types and designs of shafts (axles) joining differentials to wheels?
As Sharath said...
Quote:
Oh, that tiny thing. When you say axle, I can only think of solid axle.
Arka, would you do us the honour of talking about this? Solid beams as well as tiny things? Let this be basic tech class #3.
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What about the CV joints? Beyond my competence.
Spike, would you be so kind as to tell us about CV joints? Basic tech class #4.
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Originally Posted by Sutripta View Post
I think a section on different hubs should also be included.
Sutripta-da, apnakey bolteyi hobey (amader dabi mantey hobey type request! ).
In translation: We're demanding that Sutripta-da take basic tech class #5 on different types of hubs! BTW, those who haven't met and talked to him won't know what a wonderful teacher he is.

Last edited by SS-Traveller : 18th October 2010 at 23:14.
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Old 19th October 2010, 10:19   #94
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Originally Posted by SS-Traveller View Post
As Sharath said...
Arka, would you do us the honour of talking about this? Solid beams as well as tiny things? Let this be basic tech class #3.
Hi SS,

I think only Samurai, can do justice to this topic.
Regards,

Arka
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Old 19th October 2010, 11:06   #95
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Lets talk about hubs first.
MY knowledge is limited. I know 3 basic types
1. Always locked hubs - New gypsies, Full time 4WD vehicles like fortuner
2. Manual locking hubs, eg WARN. You get down and lock hubs
3. Auto locking hubs which Safari/Scorpio/Endeavor have
The can be of
1. Vacuum type i,e, ford
2. Pin type i,e safari/scorpio etc., These require reversing to unlock hubs
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Old 19th October 2010, 11:16   #96
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Originally Posted by ex670c View Post
I think only Samurai, can do justice to this topic.
Not really, I know so little about internals of 4x4. I only know about their behavior, and not the technology behind it. That is why I refuse to accept any title as expert, guru, etc.
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Old 19th October 2010, 22:16   #97
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Now, what's next? Subject to Sutripta-da's approval, may I suggest...
You are the thread owner!
Actually I think its time to move onto the characteristics of FWD, and RWD, and what extra 4WD brings to the table.


Spike, would you be so kind as to tell us about CV joints? Basic tech class #4.
Till Spike, or someone else chips in, I think we can proceed knowing that CV joints exist!

Sutripta-da, apnakey bolteyi hobey (amader dabi mantey hobey type request! ).
Sounds like a Puja bonus gate meeting. (Sorry non WB residents. Can't be translated. )
In translation: We're demanding that Sutripta-da take basic tech class #5 on different types of hubs! BTW, those who haven't met and talked to him won't know what a wonderful teacher he is.
A large number would disagree!
To do justice would require a lot of diagrams. What is most important, IMHO, is knowing PRECISELY when the hub engages and disengages.

Going to be rather busy this week. Result of loafing around last week.

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Sutripta
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Old 20th October 2010, 11:15   #98
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Quote:
Originally Posted by Sutripta View Post
You are the thread owner!
No one owns a thread like this! I don't know or expect to be able to explain all the aspects of drivetrains and FWD/RWD/4WD/AWD all by myself. This thread belongs to all of you who are actively participating and contributing to its knowledge base, and is dedicated to those who stand to gain from it.
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Originally Posted by Sutripta View Post
Actually I think its time to move onto the characteristics of FWD, and RWD, and what extra 4WD brings to the table.

To do justice would require a lot of diagrams.
Here's a diagram that explains the different ways all four wheels are driven.
Driving all four wheels: how is it done?-drivetrain.jpg
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Old 21st October 2010, 10:25   #99
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Default Types of Wheel Hubs

Hi Guys,

What is the purpose of a Wheel Hub?
i) Carry the weight of the vehicle

ii) Carry the Bearing/Unit Bearing

iii) Connect the wheels to the Differential

Hubs can be classified depending on their construction
i) Semi-Floating - Jeep Wrangler YJ/TJ Cherokee/XJ

ii) Full-Floating - Willys MB/CJ3A/CJ3B/MM550XD/Bolero

or they can be classified according to their purpose
i) Normal Hub

ii) Reduction Hub, have a set of gears in the Hub, this can be of two types,
a) Planetary Reduction - Magirus-Deutz/Tatra
b) or a Reduction Drop Box (Portal Axle). MB-Unimog/Volvo C303

The Free Wheeling Hub is basically an axle disconnect, its a modification of the Front Drive Flange.

In some systems, the the front axle has a disconnect mechanism on the axle instead of the drive flange.

Diagnosing 4WD Engagement Problems on Dodge Ram pickups

Regards,

Arka
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Old 21st October 2010, 11:57   #100
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Default RWD vs. FWD vs. AWD

A comparison summary of the various drive systems.

Driving all four wheels: how is it done?-rwd-vs-fwd-vs-awd.jpg
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Old 23rd October 2010, 22:14   #101
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Quote:
Originally Posted by ex670c View Post
Hi Guys,

What is the purpose of a Wheel Hub?
i) Carry the weight of the vehicle

ii) Carry the Bearing/Unit Bearing

iii) Connect the wheels to the Differential

Hubs can be classified depending on their construction
i) Semi-Floating - Jeep Wrangler YJ/TJ Cherokee/XJ

ii) Full-Floating - Willys MB/CJ3A/CJ3B/MM550XD/Bolero

or they can be classified according to their purpose
i) Normal Hub

ii) Reduction Hub, have a set of gears in the Hub, this can be of two types,
a) Planetary Reduction - Magirus-Deutz/Tatra
b) or a Reduction Drop Box (Portal Axle). MB-Unimog/Volvo C303

The Free Wheeling Hub is basically an axle disconnect, its a modification of the Front Drive Flange.

In some systems, the the front axle has a disconnect mechanism on the axle instead of the drive flange.

Diagnosing 4WD Engagement Problems on Dodge Ram pickups

Regards,

Arka
Thanks. Talking of hubs in the context of 4WD, I meant emphasisng the drive connect/ disconnect part.

@SS Nothing much to add to your post, except that why essentially two types (FEFD by far, and to a much lesser degree, FERD) are the norms today. Anything else can be considered an exotic. And what are the needs/ issues which cannot be answered by these two systems, but can be answered by 4WD. And whether all those needs can be answered by one kind of 4WD system, or do we need different types.

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Sutripta
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Old 25th October 2010, 22:22   #102
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Hi SS,
Thread seems to have stalled. So let me ramble on a bit more. (I can always bump your thread!) (NB. These conclusions are the result of my (mis)understandings, and gross oversimplifications. May it lead to heated debate!)

Let me go backwards. We have different types of 4WD systems. Do they all address the same needs, or different ones. And what can these needs be which cannot be met by the standard (2WD) configurations.

The standard today is Front Engine Front Drive. The reason for its predominance is that it is economical of resources, (though the big three said no for years), does some jobs really well, and most others reasonably well. It is economical because it gives the best usable volume/ overall volume. Less material= lighter= better FE. It is easier to fit machinery between the two front wheels, than it is to fit humans or luggage.

If the heavy machinery is over the front axle line, we get very good traction. Most people felt the need for traction in snow and ice covered roads. In these conditions, FEFD was way superior to FERD.

But FEFD has a very major drawback- handling. A fixed patch of rubber on the ground can generate only so force, which now has to be shared between steering and traction duties. Also the steering and tractive forces interact in nonintutive ways. Thus into our jargon list came terms like torque steer, lift off tuck in, terminal understeer etc. Over the years, cars have become more and more powerful, outpacing advances in tyre technology. And the more powerful the car is, the more prominent these failings become. And the person who buys/ drives a powerful car is going to demand more from his car than point to point transport. It is best not to use Front WD for the ultimate driving machine.

So we separate the the steering and driving wheels. RWD. Our goal is handling finesse, the ultimate driving machine. So also a 50/ 50 weight split. Oh my, we are now loosing traction. Bigger tyres, bigger tyres. (Ok, problem apparently solved, but in adverse conditions of rain, let alone ice, it might be better to leave the gumball equipped all prancing all snorting machinery in the garage and shift to humbler modes of transport).

So next we have to discuss what are the conditions where we will find the traction afforded by these two configurations is insufficient, and what can be done about it.

Regards
Sutripta
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Old 25th October 2010, 22:54   #103
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Originally Posted by Sutripta View Post
Talking of hubs in the context of 4WD, I meant emphasisng the drive connect/ disconnect part.
Found this interesting webpage with some info on Warn hubs, with diagrams - Warn Hubs.
Quote:
Originally Posted by Sutripta View Post
Let me go backwards. We have different types of 4WD systems. Do they all address the same needs, or different ones. And what can these needs be which cannot be met by the standard (2WD) configurations.
That is the moot point of this thread - are all 4WD systems alike and do the same job? We have a thread running here (Used XC90 or Santa Fe), where the member is looking for a vehicle capable of handling moderate off-roading, but his choice of vehicles is least suited for moderate off-roading - both vehicles he talks about are on-demand 4WD systems, designed to handle slippery/snowy tarmac surfaces.
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4. Can handle moderate off-roading.

It seems Santa-Fe is matching all my requirements (still waiting for a TD). However I came across few deals where used XC90 is also available...
And Sutripta-da, this thread was just taking a break because the thread starter was busy here (Hawk-On-Fours® (H-4®) Roadtrip - Amritsar & Pathankot).

Last edited by SS-Traveller : 25th October 2010 at 22:57.
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Old 30th October 2010, 12:24   #104
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Mitsu Evos and Nissan Skylines are AWD vehicles, like the Audi Quattro, with every new generation incorporating more and more electronic wizardry to put down the phenomenal power their engines generate, on to the road. But in the end, they are best suited for smooth tarmac or at most, bad-road/snowy-road situations, not mud-plugging or rock-climbing. Watch this video and imagine a Thar there - where the Quattro struggles, the basic Thar would move like a Sunday walk in the park.
Thank you SS-Traveller. I have learnt a lot from this thread.

However, I’m confused about your Audi Quattro example. Not sure how a 4WD would help in that situation. The problem is that of friction. Snow-chains or Studless tyres may certainly help.

Cheers.

Last edited by bliss_now : 30th October 2010 at 12:26. Reason: misquote
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Old 30th August 2011, 00:27   #105
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Default Re: Driving all four wheels: how is it done?

I was researching crawl ratios for 4Wd vehicles, and have a question for the Gurus: what are the factors that go into deciding the transfer case low range ratio? E.g. why would a Safari have 2.68, but Vitara and Pajero around ~ 1.9? The latter cars are more expensive, and a higher number means more torque in low range, so why would a Safari have a higher number than a Pajero's, say (1.925, if I am not mistaken)?
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