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Old 27th June 2015, 13:58   #361
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Default Re: Driving all four wheels: how is it done?

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Originally Posted by Sutripta View Post
^^^
If you have brake control over individual wheels, do you need a LSD?

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Sutripta
A very good question. Can I seek another answer, that probably is known to the experts here.

How is the condition of a free spinning wheel determined? And once the vehicle has moved, say a delta amount, what does the systems interpret as? What happens to the torque split right at that point.

On a Locking differential (by mechanical means - I dont necessarily mean MLD) one has the choice of keeping the diff locked till one can anticipate having no more need of keeping it locked.

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Originally Posted by roy_libran View Post
Imagine the jugglery you'd need to do the moment you're unstuck!
Wont that jugglery be controlled by a CPU?
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Old 27th June 2015, 14:12   #362
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Default Re: Driving all four wheels: how is it done?

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Originally Posted by 1100D View Post



Wont that jugglery be controlled by a CPU?
Yes, the concept is same. Individual brake control. Do it manually and you need jugglery, but have a CPU do it, its seamless
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Old 27th June 2015, 16:23   #363
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Originally Posted by shashanka View Post
.......... (depends on the pitch of the teeth of the meshing worm-to-worm internals), within the reach of enthusiasts with limited means !

I would like to make a correction to the above : It should read .... (depends on the pitch angle of the teeth of the meshing worm-to-worm internals),...

With apologies to the mods.
Shashanka

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Originally Posted by 1100D View Post
A very good ....keeping it locked.

Wont that jugglery be controlled by a CPU?

The question was "If you have brake control over individual wheels...". It seemed to me that perhaps Sutripto meant manual control rather than having a CPU (EBD) do it for you.

Last edited by khan_sultan : 30th June 2015 at 10:34. Reason: Making it as one logical post.
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Old 27th June 2015, 19:42   #364
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Default Re: Driving all four wheels: how is it done?

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Originally Posted by 1100D View Post
How is the condition of a free spinning wheel determined? And once the vehicle has moved, say a delta amount, what does the systems interpret as? What happens to the torque split right at that point.
Detecting, and handling the transitions is where you show (off) your engineering prowess.

Quote:
Wont that jugglery be controlled by a CPU?
+1. (But do check out fiddle brakes . Needs a navigator though, and only two wheels.)

Regards
Sutripta

Last edited by Samurai : 29th June 2015 at 21:13. Reason: typo
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Old 29th June 2015, 12:39   #365
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Default Re: Driving all four wheels: how is it done?

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Originally Posted by Sutripta View Post
Detacting, and handling the transitions is where you show (off) your engineering prowess.
Regards
Sutripta
Shouldn't that read driving prowess rather than "engineering prowess"!
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Old 29th June 2015, 12:51   #366
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Default Re: Driving all four wheels: how is it done?

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Originally Posted by Sutripta View Post
But do check out fiddle brakes
Thanks for mentioning fiddle brakes. Read about it. Learnt something new today. Reading continues.
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Old 29th June 2015, 13:24   #367
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Default Re: Driving all four wheels: how is it done?

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Originally Posted by Sutripta View Post
+1. (But do check out fiddle brakes . Needs a navigator though, and only two wheels.)

Regards
Sutripta
Fiddle Brakes or Fiddling with Individual Brakes:

It should be easy enough to determine and operate when you are clearly stuck, thus knowing which wheel has traction and which not!

But, what do you do, when for example, you are going up a steep incline, and need a 50-50 Torque split, to ensure that there is some available to whichever wheel needs the same. I don't think any contraption involving individual brakes will give a 50-50 split, will it?

Please correct me, if I have got it all wrong.
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Old 29th June 2015, 21:19   #368
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Default Re: Driving all four wheels: how is it done?

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Originally Posted by shashanka View Post
Shouldn't that read driving prowess rather than "engineering prowess"!
No, engineering it is. Was talking of an automated system.

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Originally Posted by tsk1979 View Post
but have a CPU do it, its seamless
Easier said than done.

Quote:
Originally Posted by roy_libran View Post
But, what do you do, when for example, you are going up a steep incline, and need a 50-50 Torque split, to ensure that there is some available to whichever wheel needs the same. I don't think any contraption involving individual brakes will give a 50-50 split, will it?
That is why I said

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Originally Posted by Sutripta View Post
Detecting, and handling the transitions is where you show (off) your engineering prowess.
Or talk to the marketing/ engineering team of say the Mercedes M series!

Regards
Sutripta
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Old 29th June 2015, 21:41   #369
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The wisdom of keeping your engine in optimum power band answers question of why gypsy with momentum is able to take the incline.
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Old 30th June 2015, 02:35   #370
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Default Re: Driving all four wheels: how is it done?

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Originally Posted by Sutripta View Post
..............Or talk to the marketing/ engineering team of say the Mercedes M series!

Regards
Sutripta
Or perhaps Alan Wenbourne of meccanoscene, who, though not as exalted as the M series team, is sufficiently lucid on the esoteric nature of the Torsen and the Ferrari diffs!

Regards,
Shashanka
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Old 6th July 2015, 15:06   #371
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Default Re: Scorpio VLX 4x4 Review: 1000 kms in Lahaul-Spiti

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Originally Posted by DirtyDan View Post
For those of you who STILL wish to dispute the rather obvious short-comings of the Scorpio mHawk VLX 4WD, I would like to refer you again to B.D.'s post #32 in this thread. Can there be any question that B.D. is in complete agreement with Eric (RINGOISM) on this matter?

Auto transmissions also give some degree of protection from drivetrain "windup" in 4x4 vehicles (without center diffs) as the mechanical connection between front and rear axles is lacking. The auto transmission takes up the friction between axles turning at different speeds....to a point anyway. That being said, I would rather drive a MT....it's more manly and tends to awe de womens.
Hear hear Dirty Dan !

Never heard a truer word! I am 63+ and I am all for "awing de womens"!
Tho' most of them - specially the new rally participants awe de hell outa me!

And to be frank, so much hair-splitting & semantics over torque-wind-up & center diffs & torque-splitting is getting a bit long in the tooth! Apart from folks like 1100D, Blackpearl and a few other genuinely brave enthusiasts in these columns, I suspect most others are like me - Sunday off-roaders, for whom the weekly jaunt to Naukuchiatal & surrounds give me bragging rights!
Regards,
Shashanka
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Old 16th July 2015, 21:12   #372
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Default Re: Driving all four wheels: how is it done?

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Originally Posted by 4x4addict View Post
I think they did away with the center differential. I hope this is not the case.
And consequences would be...?

I mean, can some one please explain this a bit?
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Old 17th July 2015, 11:00   #373
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Default Re: Driving all four wheels: how is it done?

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Originally Posted by Sheel View Post
And consequences would be...?

I mean, can some one please explain this a bit?

Hello Sheel,
Since so many others before this have discussed the topic threadbare, it may be presumptuous of me to butt in - but there is really no great mystery to it.

With the 3rd diff. (or central differential) in place the problem of drive-line or transmission wind-up (very noticeable on smooth tarmac, particularly while making steering-lock turns, and caused by the different rotational speeds of the front & rear prop. shafts/drive-lines) is eliminated. The central differential allows for different relative input speeds to the front/rear differentials, while still maintaining torque to both front & rear.
In place of the 3rd/central diff. there are also different kinds of couplings (viscous/hydraulic) used which fulfil the same function - allowing different input speeds to front/rear diffs while maintaining torque.
All this nuclear science allows the vehicle to be labelled "AWD", meaning it has permanently engaged 4WD. In addition to this basic set up one can have all sorts of fancy frills as discussed ad nauseum earlier in the thread.

A 4WD vehicle without the central/3rd diff (Scorpio, Thar and a whole army of others) is hugely competent in off-road conditions where its 4WD capability is quite apparent. And on smooth tarmac, as mentioned earlier, it is not advisable to engage 4WD and let it continue as a normal 2WD highway cruiser.

Comments and corrections to the above - from all pundits in the forum - are always welcome.
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Old 17th July 2015, 13:28   #374
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Default Re: Driving all four wheels: how is it done?

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Originally Posted by SS-Traveller View Post
Vehicles with part-time 4WD systems do not have a centre differential.
.
Why? Because of design or any limitation?
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Old 18th July 2015, 00:11   #375
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Default Re: Driving all four wheels: how is it done?

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Why? Because of design or any limitation?
Design limitation governed by cost factor.
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