[Samurai]

Originally Posted by Sudarshan

P.S. dear mods please delete this if not worth ( but only after a few people have read it )

No need to delete anything. Sudarshan, any mention of My Cousin Vinny is hardly Off-Topic in any discussion involving LSD, solid axle and IFS. I am very surprised you haven't heard of this movie.

The following is a scene from the movie My Cousin Vinny:

Originally Posted by IMDB

Mona Lisa Vito: The car that made these two, equal-length tire marks had positraction. You can't make those marks without positraction, which was not available on the '64 Buick Skylark!
Vinny Gambini: And why not? What is positraction?
Mona Lisa Vito: It's a limited slip differential which distributes power equally to both the right and left tires. The '64 Skylark had a regular differential, which, anyone who's been stuck in the mud in Alabama knows, you step on the gas, one tire spins, the other tire does nothing.
[the jury members nod, with murmurs of "yes," "that's right," etc]
Vinny Gambini: Is that it?
Mona Lisa Vito: No, there's more! You see? When the left tire mark goes up on the curb and the right tire mark stays flat and even? Well, the '64 Skylark had a solid rear axle, so when the left tire would go up on the curb, the right tire would tilt out and ride along its edge. But that didn't happen here. The tire mark stayed flat and even. This car had an independent rear suspension. Now, in the '60's, there were only two other cars made in America that had positraction, and independent rear suspension, and enough power to make these marks. One was the Corvette, which could never be confused with the Buick Skylark. The other had the same body length, height, width, weight, wheel base, and wheel track as the '64 Skylark, and that was the 1963 Pontiac Tempest.
Vinny Gambini: And because both cars were made by GM, were both cars available in metallic mint green paint?
Mona Lisa Vito: They were!
Vinny Gambini: Thank you, Ms. Vito. No more questions. Thank you very, very much.

[Sudarshan]

Originally Posted by Samurai

No need to delete anything. Sudarshan, any mention of My Cousin Vinny is hardly Off-Topic in any discussion involving LSD, solid axle and IFS. I am very surprised you haven't heard of this movie.

The following is a scene from the movie My Cousin Vinny:

Hmm , I have seen it , don't exactly remember everything .

anyways you will have many surprises with me

but thanks

Sudarshan

[svsantosh]

At this rate there would be another movie called 'My Cousin Jimny' with many scenes abridged from TBhp and we would be still head banging over the IFS/Thar.

Just trying to deviate, Is the Jimny solid at both ends, at least??

[Jaggu]

Originally Posted by The Wolf

If Im not wrong totally the top 3 teams that won the Dakar this time are running IFS.

Originally Posted by ex670c

The Suspension & Space-Frame Chassis, the Dampers alone cost a few Lakhs EACH!!!!!

Also check how many times they get the suspension changed during the raid (Dakar).

We all know competition vehicle, be it ones prepared for WRC or events like Dakar are custom built with custom parts "most" of the times. They don't run anything close to stock in the vehicles when it comes to suspension bits.

Originally Posted by svsantosh

Just trying to deviate, Is the Jimny solid at both ends, at least??

Yup solid axle and that is why its respected. Basically a SWB Gypsy but with better mechanical and modern interior bits.

[siddartha]

Originally Posted by Samurai

No need to delete anything. Sudarshan, any mention of My Cousin Vinny is hardly Off-Topic in any discussion involving LSD, solid axle and IFS. I am very surprised you haven't heard of this movie.

The following is a scene from the movie My Cousin Vinny:

awesome! thanks sharath for citing ms vito and the movie. its my fav movie!

[The Wolf]

Originally Posted by ex670c

Hi Wolf,

The Race VW Toureg and BMW's are totally different beasts, compared to their more civil avatars.

The Suspension & Space-Frame Chassis, the Dampers alone cost a few Lakhs EACH!!!!!

Also check how many times they get the suspension changed during the raid (Dakar).

Also in the Same Paris-Dakar, please check out the Kamaz vs Tatra.

Regards,

Arka

Im sure each one has their own reasoning and confidence by virtue of lessons learned(over decades) behind their set-ups right? Some go supercharged and some go Turbo...both have their strengths and weaknesses...like ways mate!

Speaking your language: Do you think cost is the constraint for either teams or is it that the Tatra folks like to break it for fun??!!

Finally if you are speaking about the number of victories in the solid axles bucket, yes they are more in this category but I refrain from believing that the suspension alone is the differentiator between the victorious and the non-victorious. BUT, as a final-final touch if you consider the overall number of victories (all categories) the IFS is far ahead of the SFA if Paris-Dakar is the absolute context of discussion here

[Sutripta]

Hi,
My question was not in trying to determine winners (and losers) but to find out the characteristics of IS vs solid axle systems, and the reason for those characteristics.

Disclaimer - All ramblings that follow are strictly my opinion only.

And Spike who are you sulking at? We all NEED you!

The diversity of comments/ thoughts/ opinions are, I feel, simply a reflection of the complexity of suspension design. There are so many interacting variables that suspension design is an art, backed by engineering. This is why only a handful of companies get it right consistently. (For those who don't it is not always the beancounters fault). It is also the reason why trying to analyse each aspect individually is less than satisfactory. But satisfactory or not, that is the only too in our hands. So I think the things we will not be discussing (wrt my question) will be things like cornering behaviour (sacrilege), track changes, camber changes, anti sway bars etc. Concentrate only on weight transfer on the wheels, and orientation of suspended mass wrt wheels.

To deal with the (I think simpler) questions first.

CG higher in a SFA vehicle:- Result of packaging. The vehicle components and masses perforce have to be above the wheel centre line. In an IS, these masses can (and are) placed between the wheels. (@AutoNoob We are not talking of weights of the drivetrains, and their contribution to the CG. Also my question started off with 'assume equal suspension travel')

(These posts were not wrt my post, but still..) Thar (again!) and antisway bars. Yes, disconnecting will help achieve better articulation. Also with the massive increase in oversteer, would make for a very 'entertaining' drive. Might even take you off road when you dont want to! And no, the antisway bar is not the primary member (if at all) in maintaining wheel geometry.

Track changes are important from tyre wear PoV, if nothing else, but I don't think are important in our discussion.

Ground clearance, CV joint angles etc important practicalities. Not within the present scope of my question.

Important question: Often a statement to the effect that 'In a SFA, as one wheel is pushed up, the other wheel pushes down harder. Not so in an IS'. Can someone please explain what and why.

Regards
Sutripta

[madhkris]

Food for thought and some eye candy : A few articulations I have shot from the Avalokonda OTR 2011.

[Jaggu]

Please dont even look at the first 550 pics for articulation, the owner himself is very unhappy with it and would have exchanged those tyres by now

[svsantosh]

^^ I think he was trying to emphasize the 'lack' of it. But, seriously, it made the whole trail without a fuss, shows that 35" tyres do help a bit :P

[Jaggu]

Oh that 35" tyres are SUPERB while climbing! While using 1st low instead of this 2 low jeep thingie to compensate the changed ratio.

Only when he goes down hill or any place where articu (not completing, coz that is all it will do) vehicle virtually comes to a stand still.

[karizma9292]

Guys attaching some crazy , jaw dropping articulation pics of a Suzuki samurai

[ex670c]

Originally Posted by Sutripta

CG higher in a SFA vehicle:- Result of packaging. The vehicle components and masses perforce have to be above the wheel centre line. In an IS, these masses can (and are) placed between the wheels. (@AutoNoob We are not talking of weights of the drivetrains, and their contribution to the CG. Also my question started off with 'assume equal suspension travel')

Important question: Often a statement to the effect that 'In a SFA, as one wheel is pushed up, the other wheel pushes down harder. Not so in an IS'. Can someone please explain what and why.

Hi Sutripta,

wrt to your 1st question, I would like to share an observation

Швед�кий портал : Land Rover Defender на редукторных мо�тах Laplander : Off-road drive

The much heavier and wider portal axle; increasing the GC by 5 inches scores higher on the "Bank" platform.

wrt to your 2nd second question, my guess is due to Axle Tramp, due to the Solid Axle setup.

Regards,

Arka

[Sutripta]

^^^^
Hi,
Cant read Russian (Google translate zindabad), but infer they are referring to portal axles. You are right. But portal axles are so exotic that these are excluded from normal thought processes! (Incidentally, one thing I've always wondered about was the thought process behind Shaktiman's driveline. Any illumination?)

Axle tramp is a dynamic phenomenon. Reaction when one pushes too much of torque through a solid axle setup. (Most noticeable on smooth roads during start of a drag involving Ambassadors or Premiers.) Is that what people are referring to? When one is precision guiding ones ride through hostile terrain?

Regards
Sutripta

[SS-Traveller]

Disclaimer first: Have been reading this thread from the beginning, and off-road articulation is something I have a lot to learn about yet. Thank you all for sharing the knowledge.

Now for a few silly questions, @ Sutripta , ex670c , Spike , Jaggu etc., based on the following discussion:

Originally Posted by Sudarshan

think what will happen if the Thar's ,anti roll / stabiliser bar is removed .

Originally Posted by Sudarshan

...my feeling is ,if that bar is removed both sides will be acting independently .
...need to think deeper here...

Originally Posted by pjbiju

...removing the anti-roll bar will seriously affect the Thar's on-road characteristics.

The Range Rover came in its original guise in the '70s and '80s without any anti-roll bar, and purist off-roaders as well as the company refused to fit any saying articulation would be compromised. However, on-road behaviour was sometimes compared to a hippopotamus by non-off-road-enthusiasts, and a specialist tuner (IIRC it was Overfinch) offered a suspension upgrade that included the anti-roll bars - and these could be removed easily for improved articulation when going off-road.

Now my questions are: Why did Rangies start having anti-roll bars factory-fitted after the early nineties? What was the change in suspension geometry that allowed the company to believe that the car retained its original articulation and off-road ability, despite the anti-roll bars? Also, would removing anti-roll bars from the Thar (or any other anti-roll-bar-equipped 4x4 vehicle's suspension) really make it articulate better off-road (or really terrible on-road, like a hippo - depending on where you are driving)?