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Old 27th April 2009, 10:52   #211
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@ APS Grewal
wonderful pictures!! Gurkha in its home teritory!! Would be an off topic, do you have the pics of invader beside your gurkha? The rear tyres had an interesting pattern there. Can you post some pics of it too? Both seem to have done a bit of offroading. Any comparison?

@ samurai
Wonderful test conducted under similar conditions to two legendary vehicles. Clearly Diff- locks here had an advantage!! This shows there is absolute nothing!! Gurkha failed in some conditions (earlier reports) and so does M&M.
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Old 27th April 2009, 11:20   #212
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Default Gurkha vs CJ340

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Originally Posted by Samurai View Post

Take this example, the steepest challenge in my trail is very slippery and powdery dust right now. Usually this climb needs a run-up. When I came up with little less momentum, I slipped and slided and had to reverse back and clear it in second attempt.

Attachment 129587

Look at the dust in my wake when I got across.

Attachment 129588
Hi Samurai,

Notice the picture of the CJ340 wheels spinning away, too much momentum and too much engine RPM and too Low gearing.

Try the climb from standstill and vary the engine RPM to maintain the flywheel RPM (momentum).

If a heavier vehicle can do it from standstill, a CJ340 can definitely do it.

Your cousin drove the Gurkha very well.....I guess he has been following up on TBHP.

Regards,

Arka
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Old 27th April 2009, 11:55   #213
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Originally Posted by ex670c View Post
Notice the picture of the CJ340 wheels spinning away, too much momentum and too much engine RPM and too Low gearing.

Try the climb from standstill and vary the engine RPM to maintain the flywheel RPM (momentum).
Arka, I have tried this hill in very possible gear and speed in my Jeep. Afterall, this is my backyard. BTW, there isn't too much momentum, how fast can you get at 2nd low with 5:38 axle ratio? It looks like that because the photo was taken at very low speed (1/15 sec), due to the lowlight.

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If a heavier vehicle can do it from standstill, a CJ340 can definitely do it.
The Gurkha did it by deploying both the diff locks. The hill is too slippery to do from standstill using an open diff vehicle. This hill is actually a landfill, not hard ground.

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Your cousin drove the Gurkha very well.....I guess he has been following up on TBHP.
Coming from you, he will be thrilled to hear that.
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Old 27th April 2009, 12:07   #214
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hmmn..
samurai, interesting to know that, your back yard seem to be testing ground of sorts. May be you should lease it to 4x4 manufacturers to test thier machines

Last edited by vinod_nookala : 27th April 2009 at 12:09.
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Old 27th April 2009, 14:21   #215
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Default Samurai on a Gurkha: now that's something to look out for.

@Samurai

It was good to read your piece with the photographs.

I read everything you or Sultan Khan writes on off-roading with almost religious fervour, for slightly different reasons. Very few have the knack of breaking down these exercises to their essentials, examining what works best for these essentials, and putting together a best practices kind of output. It was a treat to watch this being done in the broad light of day, with no hocus pocus or religious belief being shoved down our throats. For Sultan Khan, it was the unbelievable, systematic way in which he has been converting a simple little tin box on wheels to a superior rock-climber; I am not sure if he has got it doing its tricks on other surfaces because of my own difficulties in keeping up of late.

You will understand that I was surprised at your negative reactions the first time around, citing the lack of performance the vehicle showed. The general sense of the thread also was about the lack of alternative evidence other than old magazine articles. As it happens, I have been receiving kindergarten lessons in this from the old grouch himself, and what he and his Gurkha can do, and have done in front of me, is fearsome. You will say that that kind of statement calls for visual evidence; I know that this sounds like a lame excuse, but having lost my camera in April last, I was quite disheartened, especially in view of my personal circumstances, and have not really bothered to buy a new one. By the time hostilities broke out, it was too late.

I don't have a scale of comparison, so it is difficult to say much, but in the hands of the experienced off-roader, this monster was doing everything with what can only be described as somewhat casual ease. Choudhury is fussy about gears, but I got the feeling that even a relative newcomer would have been in for a treat. On the very, very few occasions I was allowed to put my grubby little paws on the sacred wheel, it felt like being on a turbo-charged feather mattress; Safari meets steam locomotive ke mafik.

Now what I want to do is to get into the local Kolkata off-roading scene. With U. B. Singh in the neighbourhood, this should not be a Himalayan task (I love my sense of humour, I do), and I would like Godzilla to do its stuff there. It's too much to hope that I can get this buggy down south complete with its expert driver (he doesn't seem to travel well, like some vintages), and I can't afford to buy it myself, not at this stage, so all that is possible is nice pictures from Kolkata.

If you get to fling the beastie about on one of your regular o-r exercises, it'd be a treat. I'll wait for that.
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Old 27th April 2009, 14:41   #216
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Samurai,
Surely your engine was not under powered for the incline or the lenght of the slope.
What if your jeep had the differential lock advantage too, how do you think it would compare against the Gurkha on this track?
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Old 27th April 2009, 14:51   #217
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Quote:
Originally Posted by Samurai View Post
...
The Gurkha did it by deploying both the diff locks. ...
By any chance, did you further try this with ONLY one (the rear) diff locked? Curious to know what happened in that scenario.
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Old 27th April 2009, 15:11   #218
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Arka, I have tried this hill in very possible gear and speed in my Jeep. Afterall, this is my backyard.
Could the tires be a factor here (larger contact patch on the Gurkha)?

PS: Your backyard brings back fond memories. Is this terrain near "end point" - the opposite bank of the river ?
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Old 27th April 2009, 15:16   #219
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Quote:
Originally Posted by bonobashi View Post
I read everything you or Sultan Khan writes on off-roading with almost religious fervour, for slightly different reasons. Very few have the knack of breaking down these exercises to their essentials, examining what works best for these essentials, and putting together a best practices kind of output. It was a treat to watch this being done in the broad light of day, with no hocus pocus or religious belief being shoved down our throats.
Thanks for the wonderful compliment bonobashi. This is a habit I bring from my profession, where I analyze everything to individual components until I understand it entirely.

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Samurai,
Surely your engine was not under powered for the incline or the length of the slope.
What if your jeep had the differential lock advantage too, how do you think it would compare against the Gurkha on this track?
Quote:
Originally Posted by fazalaliadil View Post
Surely your engine was not under powered for the incline or the length of the slope.
What if your jeep had the differential lock advantage too, how do you think it would compare against the Gurkha on this track?
I never said it is underpowered for the hill, in fact, it has climbed this hill lots of times, under varying conditions. But never by starting at the base of the hill. It always needed the momentum to overcome the slipperiness of the hill. If it had diff locks, it would have climbed with the same ease as Gurkha, that I am sure. I mentioned the power because Gurkha went up most of the hill without me touching the accelerator.

At one place I was stuck when the skid plates sat on the ground, with one wheel spinning in each axle. I had to get the Jeep pushed back and retry it with little extra momentum to go over it. The Gurkha, despite having a longer wheelbase, merely glanced the mound, didn't get struck due to higher GC.

Now, none of you have really seen the terrain first hand, and you all know you can't judge offroad terrain from photographs. I drove both my own CJ340 and an unfamiliar Gurkha on the same track around the same time, and found Gurkha performing better. We are comparing a 1994 CJ340 with 2007 Trax Gurkha, the latter costs 4-5 times more in the current market. Gurkha is factory built for offroad purpose, and equipped with offroad essentials. Being a Jeep owner I have no reason to give undue credit to Gurkha. I am calling it as I see it, the only bias here is my limited experience in offroading.

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Originally Posted by khan_sultan View Post
By any chance, did you further try this with ONLY one (the rear) diff locked? Curious to know what happened in that scenario.
No, we were running out of daylight.

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Originally Posted by CrackedHead View Post
Could the tires be a factor here (larger contact patch on the Gurkha)?
No, I had fatter AT tyres, the Gurkha had narrower highway tyres.

Quote:
Originally Posted by CrackedHead View Post
PS: Your backyard brings back fond memories. Is this terrain near "end point" - the opposite bank of the river ?
No, this is inside my office campus.

Last edited by Samurai : 27th April 2009 at 15:19.
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Old 27th April 2009, 15:45   #220
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@Samurai: Would have loved to see you go at it with GV too 8-) I am merely curious as to how much diff lock works/helps on the GV. Last year I had occasion to use it during trip to Leh when I took "short cuts" up and down with 4x4LowLock and was very suprised at the difference it gave in its aptitude to climb in 1st and 2nd gears.
Again used it to climb a really steep dune during Desert Storm in similar gear settings. This is a slow that another Jeep with lockers was not able to do.
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Old 27th April 2009, 15:51   #221
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AFAIK, GV does not have DIFF locks. It just has a lockable center diff. That means if you get stuck, one front and one rear wheel without traction will slip.
However on Gurkha, you can lock front and back diffs, so even if you have 3 wheels in air, the one wheel on ground will spin alongwith.
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Old 27th April 2009, 15:56   #222
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Sudev, I don't want to tear apart the rear bumper any further. The GV rear overhang can't handle this incline.

That said, the GV diff lock is merely a central diff lock, the front and rear diffs are still open. Therefore, GV with diff locks on is same as any part-time 4WD vehicle with 4WD engaged. If it also had rear diff locks, then it is something else.
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Old 27th April 2009, 16:04   #223
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Default Diff-Locks & Wheel Spin

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Originally Posted by Samurai View Post
Arka, I have tried this hill in very possible gear and speed in my Jeep. Afterall, this is my backyard. BTW, there isn't too much momentum, how fast can you get at 2nd low with 5:38 axle ratio? It looks like that because the photo was taken at very low speed (1/15 sec), due to the lowlight.

The Gurkha did it by deploying both the diff locks. The hill is too slippery to do from standstill using an open diff vehicle. This hill is actually a landfill, not hard ground.
Hi Samurai,

The terrain I will leave it to you.

The CJ340 had the advantage of Lighter Weight and More aggressive tyres, better power to weight even a better torque to weight advantage.

at 2nd Gear X Low Ratio X Diff-Ratio = 35.73

For a 29" Tyre (Circumference 2.3m)

at 1000 RPM distance travelled = (1000/36) X 2.3 X 60 = 3833m (3.8Kmph)
2000 RPM X 2 = 7.6 (Kmph)
3000 RPM X 3 = 11.4 (Kmph)

We have not calculated acceleration .

Why did the Gurkha not spin a wheel?

1) Weight

2) Slower Speed

3) Engaged Differential Locks

Do you think that just differential locks will make such a difference

A few dis-advantages of higher momentum.

1) Suspension jars i.e wheels hop = no grip

2) Under acceleration the especially on a incline the vehicle squats thereby lowering the belly.

3) Wheel Spin

Also the wheels don't seem to be digging in, just slipping of the shale.

Regards,

Arka
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Old 27th April 2009, 16:15   #224
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Quote:
Originally Posted by ex670c View Post
....

The terrain I will leave it to you.

The CJ340 had the advantage of Lighter Weight and More aggressive tyres, better power to weight even a better torque to weight advantage.

.....

A few dis-advantages of higher momentum.

...
Hey, a very interesting post man. throws up some quite nice points about ways to tackle an incline.

To be honest, I always have had a doubt on how "torque to weight ratio" is applicable in off-road. I always thought of the torque @ RPM part.

Now you need to help me understand this better.
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Old 27th April 2009, 16:24   #225
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Quote:
Originally Posted by ex670c View Post
at 2nd Gear X Low Ratio X Diff-Ratio = 35.73

For a 29" Tyre (Circumference 2.3m)

at 1000 RPM distance travelled = (1000/36) X 2.3 X 60 = 3833m (3.8Kmph)
2000 RPM X 2 = 7.6 (Kmph)
3000 RPM X 3 = 11.4 (Kmph)

We have not calculated acceleration .
Arka, since I have done this hill numerous times, I have videos to show.

I succeed when I do it at this speed (2nd low), now do you think this is very fast?



If I go slower or start from base of the hill, I tend to slip and slide.
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