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Old 9th July 2010, 12:35   #46
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robinson and inturn gogi got away with using only their brakes as the length of that decline was not more than 12-15 feet, and the tyres managed to find some grip. Doesn't mean they will get away with it every time.

One may use only the brakes only when you neeed to align your vehicle/make corrections before you actually decline. after that you have stay in gear, and Keep your foot on the brake pedal and apply pressure as and when required.

If the surface was a lil more wet/slippery and the length of that decline was longer or steeper the result could have been very different.

I find it hard to believe that you guys are discussing about how powerful the brakes on the invader are, and whether it has disc brakes on the front etc. All this is immaterial. what if the wheels locked up and the vehicle started sliding down? What good would the powerful brakes be at that point?

And coming to the invader not being able crawl because of it's final drive ratio... well ... what do you guys have to say abt the gypsies in such situations?
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Old 9th July 2010, 13:10   #47
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Originally Posted by siddartha View Post
robinson and inturn gogi got away with using only their brakes as the length of that decline was not more than 12-15 feet, and the tyres managed to find some grip. Doesn't mean they will get away with it every time.

One may use only the brakes only when you neeed to align your vehicle/make corrections before you actually decline. after that you have stay in gear, and Keep your foot on the brake pedal and apply pressure as and when required.

If the surface was a lil more wet/slippery and the length of that decline was longer or steeper the result could have been very different.

I find it hard to believe that you guys are discussing about how powerful the brakes on the invader are, and whether it has disc brakes on the front etc. All this is immaterial. what if the wheels locked up and the vehicle started sliding down? What good would the powerful brakes be at that point?

And coming to the invader not being able crawl because of it's final drive ratio... well ... what do you guys have to say abt the gypsies in such situations?
If your vehicle cant do it within the basic rules of off-roading - then dont do it - period. This is my thinking.

Risking your vehicle and your life is ofcourse each person's individual decision so they are allowed to take these calls. We must respect that and leave it there.

WRT the final drive ratio, if I had to climb over common sense and still attempt (well knowing that the final drive ratio is too fast for the decline), then I will still prefer to go down and brake and "stall" the engine rather than relying on brakes and de-clutch. Its much better to stall the engine and get out with your life intact than sitting inside and relying on brakes and the terrain.

In my books, stalling the engine and starting in gear (reverse/or first) is much better than riding the clutch and brakes when decsending. These are my views - and it does not matter which vehicle or which final gear ratio you are in.

PS: if you still use the clutch/brake technique, atleast switch off the engine. You will get better mileage :P

Last edited by Red Liner : 9th July 2010 at 13:11.
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Old 9th July 2010, 15:02   #48
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Dear all - as the currect discussions on off road driving techniques are proceeding mainly on "how to come down a slope", I would like to give my comments in totality.

Preamble - when you come down any slope and at that time if you are in gear in any car, the engine acts as a brake because the driven wheels are now driving the engine. Therefore, if you look at a typical TATA 1210SE truck plying the ghats in our country, you may be aware that it has a device called the "exhaust brake". This device is actuated by the driver by pressing a valve which is located on the floor of the truck between the brake and the clutch pedals. He presses this valve with his foot. This does two things. First, it cuts off the fuel supply to the engine. Second, it closes a flap valve located at the end of the exhaust manifold, thus trapping the exhaust gases of the last few fired strokes within the compression volume of the engine. Now the engine acts as a pump and retards the progress of the vehicle on a downward descent. A typical 12 tonne truck engine develops 100 BHP. I do not know the first gear ratio of the GBC30 / GBS40 transmissions fitted to a typical truck. However, the axle ratio is around 6.8:1. Now, with the "official" GVW of this truck at 15225 kg, please note that exhaust brake is essentially the main retardant besides the "power gear" used to bring the truck down a ghat road. The "brake" by itself only performs a secondary role. The truck cannot come down a ghat slope on the brake alone. It will plunge to its death.

Now if you interpolate our Jeeps within the spectrum of a similar brake system supplier, take a CJ3B / CJ340 with a 5.38 down a grade with "road Mu" able to hold its own (maybe tarmac to rubber, wet tarmac to rubber, certainly not dry sand), then you will observe that the vehicle is able to "crawl" down, or rather "clamber" down the slope in a very controlled fashion with no fuss in 4 wheel drive and in low ratio and in first gear.

There is your answer. Try and use as much "non-brake system" provided braking available in your Jeep to clamber down dslowly and safely.

The fun starts with vehicles having lower axle ratios, where even the maximum use of non-brake system provided also does not give effective deceleration to clamber down. Then the "road Mu" may not hold. Then the answer obviously is to get as much retardation as you can, means low range, means first gear and then make very very judicious use of the clutch pedal as a last resort to prevent the engine from stalling. Going down in neutral is a strict no-no. Whatever happens, never ever allow the vehicle to go sideways. To prevent the tilt, go as slowly as humanly possible. If the tilt starts, try and bring the vehicle to a halt. It is easier to bring a slowly moving vehicle to a halt. It may still not halt but steer into the tilt, correct the stance and then proceed, keeping the axis of the vehicle in the line of travel as possible.

NEVER EVER TRAVEL CROSSWAYS ON AN ASCENT / DESCENT. IT'S NOT WORTH THE RISK.

Finally, if you think you can't do it, don't do it. Don't let your "machogiri" (ego) come in the way.

Best regards,

Behram Dhabhar
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Old 9th July 2010, 15:16   #49
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Quote:
Originally Posted by DHABHAR.BEHRAM View Post
Now if you interpolate our Jeeps within the spectrum of a similar brake system supplier, take a CJ3B / CJ340 with a 5.38 down a grade with "road Mu" able to hold its own (maybe tarmac to rubber, wet tarmac to rubber, certainly not dry sand), then you will observe that the vehicle is able to "crawl" down, or rather "clamber" down the slope in a very controlled fashion with no fuss in 4 wheel drive and in low ratio and in first gear.
What if the Jeep is sliding down in 1st low? That was the bone of contention.
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Old 9th July 2010, 15:27   #50
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Good to see quite a lot of discussion around the decline incident.

Let me add to it;

I definitely agree with engine breaking. But as we know, the crawling speed for a invader is high, so you got to rely on the breaks too.

@V-16,
I made you depress the clutch completely because the way you headed towards the dip felt bit fast. And I just guided you the way I took the decline. I really dint wanted you to tap the breaks hard with the released clutch to avoid engine cut off.


But in general, I dont agree to the fact that, ABC is the only way you can take a decline. It completely depends on the Vehicle you drive the surface of the track and the angle you are in.

In the Examm trail, there was a challenging decline, which I tried. And I had to completely rely on my breaks to correct the angle until I reached a straight stretch to release the clutch in 1 low. But if the decline is really really heavy, you dont crawl, you tap the breaks even more harder with the depressed clutch and move inch by inch, and thats exactly what I did without locking the wheels and skidding.

To the forum;
I feel off road techniques are more generic. It varies from vehicle to vehicle and drivers to drivers.
We can get a download of basic understanding by google search. But all it matters is your gut feel and confidence to over come the obstacle.
Same Terrain with different jeeps with different drivers will use completely different techniques to over come the obstacle.

The best example what I can remember are those drivers who carry close to one tone of load in their 4x4 major and climb the hill without any modification in their vehicles. The only change they do is, add more leaf springs to take that weight.
Let me blatantly put it actoss, with our modified jeeps, we struggle to do that.

So I guess its all about how well you manuever your vehicle in every obstacles.
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Old 9th July 2010, 15:56   #51
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I totally agree with you Robin and as i said, am not questioning your direction to me when we came down in my CJ. In fact it was like cheesecake and i would like to come down all slopes in this composed and easy manner but you are spot on when you say that each obstacle is tackled by different drivers based on their experience, vehicle, terrain and level of comfort and thats the way to do it.

@ Siddhartha which decline are you talking about? The decline we are referring to was definitely not just 10-15 feet. More like twice that distance in feet, IMHO.
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Old 9th July 2010, 16:07   #52
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BD Sir : excellent thread!


Quote:
Originally Posted by DHABHAR.BEHRAM View Post
I am only mentioning here, now you analyse - if I want to position only one front suspension into the ditch, what am I supposed to prefer? IFS or rigid axle? Of course IFS. The rigid axle will pull both ends simultaneously so you will not get the degree of angular freedom that you will want to independently exercise over the suspension without any constraint. I once again state that I have nothing against rigid axle.
How will the Solid Axle Coil Spring work in this situation? It has much more travel than the IFS.

Quote:
I am only mentioning here, you further analyse - if I have to position my vehicle's front right tyre exactly where I want it within half an inch of positioning accuracy all through a serpentine course in real time, which steering gear will I prefer, one that is direct or one that has a lot of indirect linkages before the movement finally goes to the steering knuckles? Of course I will prefer a direct rack and pinion steering. I state that I have nothing against worm and sector or recirculating ball type steering.
Sir, I would NOT buy this one. Even the other steering types if setup correctly are pretty accurate.


Quote:
PS - I am a vehicle test engineer. I have the best job in the world.
The real difference is that you earn a living out of this job while we pass comments casually on HOW things could be better. NOW who has a better job



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Originally Posted by The Wolf View Post
Sir, you did not mention which gear you used to clear this one but Im sure you had to use Low ratio if you had to take it r..e..a..l slow. I doubt a turbo charged engine will let you crawl in 3rd/4th gears (High)without losing ground at the point of full spool. I would be surprised if its not so. Pls correct me if Im wrong.
Without the A pedal [Chamcha as BD calls it] pressed, there will be no turbo spool and no detrimental effect in crawling.

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Originally Posted by gsferrari View Post
Technique, in my view, is what will get me across to the other end without damaging the vehicle or the occupants.
..

For me the pinnacle of man-machine-trail relationship will be when I can do OTRs without assistance with a high degree of safety. I have never been stuck at any OTR until now...never needed towing out of any obstacle and I hope this run continues

.
welcome to REAL world GS.

Quote:
Originally Posted by robinson.s View Post
But in general, I dont agree to the fact that, ABC is the only way you can take a decline. It completely depends on the Vehicle you drive the surface of the track and the angle you are in.
...

To the forum;
I feel off road techniques are more generic. It varies from vehicle to vehicle and drivers to drivers.
...


So I guess its all about how well you manuever your vehicle in every obstacles.
Well Said Robinson - I agree
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Old 9th July 2010, 16:09   #53
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@V-16,
I really dint wanted you to tap the breaks hard with the released clutch to avoid engine cut off.
Robi, just a engine/technical point here. If your engine stalls when declining, you can start in gear - nothing will happen unless your gear slips into neutral. That is perfectly normal to do with our engines.

I did that decline so slow, that I purposely stalled viji's jeep thrice and just re-started in gear (it also had a small stalling issue during the event - can be corroborated by Siddu, in case you feel my skills are a moot point) and made it down.

The only issue with stalling will be, will the vehicle just slide down, if the terrain is extremely slippery? But that can happen when you lock the brakes + depress clutch as well, so this point remains equal between both methods.
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Old 9th July 2010, 16:13   #54
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Originally Posted by V-16 View Post
I totally agree with you Robin and as i said, am not questioning your direction to me when we came down in my CJ. In fact it was like cheesecake and i would like to come down all slopes in this composed and easy manner but you are spot on when you say that each obstacle is tackled by different drivers based on their experience, vehicle, terrain and level of comfort and thats the way to do it.

@ Siddhartha which decline are you talking about? The decline we are referring to was definitely not just 10-15 feet. More like twice that distance in feet, IMHO.

What I want to say is, every driver in different vehicle will handle the obstacle in different way. The same off road technique cannot be used at every level.
For Eg: Khan's Gypsy has low gear and low dif ratio, any major incline he will just crawl through, he doesn't need to gun the engine. Bt at the same time, a normal Gypsy will have to gun it earlier and use a different technique to climb that same incline.
That's all what am saying.
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Old 9th July 2010, 16:30   #55
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Robi, just a engine/technical point here. If your engine stalls when declining, you can start in gear - nothing will happen unless your gear slips into neutral. That is perfectly normal to do with our engines.

I did that decline so slow, that I purposely stalled viji's jeep thrice and just re-started in gear (it also had a small stalling issue during the event - can be corroborated by Siddu, in case you feel my skills are a moot point) and made it down.

The only issue with stalling will be, will the vehicle just slide down, if the terrain is extremely slippery? But that can happen when you lock the brakes + depress clutch as well, so this point remains equal between both methods.
I agree to your point. In both the situation in all probabilities you will slide.

But what is the probability that you will kill your engine in a decline than locking your breaks?
I guess it depends how well you are using your breaks to control the engine to cut off and locking your breaks.

But believe me we don't cross any obstacle based on such probabilities. You holding the wheels and you have control on the pedals. Take decision on the spot.

Last edited by robinson.s : 9th July 2010 at 16:36.
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Old 9th July 2010, 17:28   #56
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Originally Posted by DHABHAR.BEHRAM View Post
Dear all - as the currect discussions on off road driving techniques are proceeding mainly on "how to come down a slope", I would like to give my comments in totality.

Preamble - when you come down any slope and at that time if you are in gear in any car, the engine acts as a brake because the driven wheels are now driving the engine. Therefore, if you look at a typical TATA 1210SE truck plying the ghats in our country, you may be aware that it has a device called the "exhaust brake". This device is actuated by the driver by pressing a valve which is located on the floor of the truck between the brake and the clutch pedals. He presses this valve with his foot. This does two things. First, it cuts off the fuel supply to the engine. Second, it closes a flap valve located at the end of the exhaust manifold, thus trapping the exhaust gases of the last few fired strokes within the compression volume of the engine. Now the engine acts as a pump and retards the progress of the vehicle on a downward descent. A typical 12 tonne truck engine develops 100 BHP. I do not know the first gear ratio of the GBC30 / GBS40 transmissions fitted to a typical truck. However, the axle ratio is around 6.8:1. Now, with the "official" GVW of this truck at 15225 kg, please note that exhaust brake is essentially the main retardant besides the "power gear" used to bring the truck down a ghat road. The "brake" by itself only performs a secondary role. The truck cannot come down a ghat slope on the brake alone. It will plunge to its death.

Now if you interpolate our Jeeps within the spectrum of a similar brake system supplier, take a CJ3B / CJ340 with a 5.38 down a grade with "road Mu" able to hold its own (maybe tarmac to rubber, wet tarmac to rubber, certainly not dry sand), then you will observe that the vehicle is able to "crawl" down, or rather "clamber" down the slope in a very controlled fashion with no fuss in 4 wheel drive and in low ratio and in first gear.

There is your answer. Try and use as much "non-brake system" provided braking available in your Jeep to clamber down dslowly and safely.

The fun starts with vehicles having lower axle ratios, where even the maximum use of non-brake system provided also does not give effective deceleration to clamber down. Then the "road Mu" may not hold. Then the answer obviously is to get as much retardation as you can, means low range, means first gear and then make very very judicious use of the clutch pedal as a last resort to prevent the engine from stalling. Going down in neutral is a strict no-no. Whatever happens, never ever allow the vehicle to go sideways. To prevent the tilt, go as slowly as humanly possible. If the tilt starts, try and bring the vehicle to a halt. It is easier to bring a slowly moving vehicle to a halt. It may still not halt but steer into the tilt, correct the stance and then proceed, keeping the axis of the vehicle in the line of travel as possible.

NEVER EVER TRAVEL CROSSWAYS ON AN ASCENT / DESCENT. IT'S NOT WORTH THE RISK.

Finally, if you think you can't do it, don't do it. Don't let your "machogiri" (ego) come in the way.

Best regards,

Behram Dhabhar
Behram Sir,

All your points are very well taken, appreciate the concern and the direction you have given for safe OTR's

But, correct me if am wrong, when we cross a obstacle, (no matter how difficult it is) its all about conquering with your skill and testing your machines limit.
So why do we call as machogiri for that. I would rather call as passionate.
If we see in competative OTR's people go to the extreme to conquer every trail.
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Old 9th July 2010, 18:26   #57
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Dear Robinson - I totally agree with you that we go offroading because it is our passion. But passion and machogiri are as different as chalk and cheese. Overcoming an obstacle using your vehicle's capability and your skill is passion. Trying to prove to all and sundry that you can do something which obviously cannot be done or is not safe to do is machogiri. Our hobby is such that a little bit of machogiri manages to creep in sometimes. I used to suffer from this syndrome in my early years but now I have disciplined myself not to indulge in it at all. That's why you may now remember that I was standing next to you when your vehicle was in the last waterlogged ditch before lunch on the first day but I did not take the Thar through it because I was mentally not comfortable with that damn ditch, so I just did not do it (I have absolutely hated water crossings all these years, well, I am like that only). If I were to succumb to pressure from others (oh come on yaar and all that), it would not be passion, it would be machogiri. Passion will reward you, machogiri will break your vehicle. If a person does not want to go, he should not go. Its his vehicle so its his decision, period. Everybody must understand and respect it. I think in our forum, everyone understands and respects, which is why all of us enjoyed ourselves.

Dear Sharath - if the Jeep is built with such a driveline ratio that you are apprehensive that it will slide down even in low 1st, the best option is to winch it down in reverse (because most Jeeps have the winch in the front). It is always better to have a winch at the back also. See the photograph attached, something I did some time back. Without a winch, I agree with Robinson's comment of going down inch by inch. If it still slides, PRAY!

May our tribe increase.

Best regards,

Behram Dhabhar
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Last edited by DHABHAR.BEHRAM : 9th July 2010 at 18:38. Reason: add info
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Old 9th July 2010, 21:32   #58
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Just thought I'd add one more off road technique in the light of some great discussions here...

Always try to ford against the stream diagonally cutting it. This way even if the currents are a bit strong you are allowing a relatively smaller surface area of your water fording vehicle to it. Smaller the surface area offered to the toward flowing water the lesser the impact/push it can have on the vehicle, which inturn might help one avoid being washed off. Simple technique, might save your day...

Beware of what is hydro-block and how it can destroy your internal combustion motor before lunging into the waters. Rest, let the common sense prevail.

If the vehicle gets washed off or falls sidewards or worst case turtles in the water, ensure you unbuckle your seat belt, quickly open the door and stay away from the vehicle if its tumbling through with the current, but, if the vehicle is not tumbling stay close to the vehicle climb and over it as fast as possible. Remember, your vehicle is your highest and the closest possible vantage point. Dont forget to stay clear of the hot exhaust pipes while climbing on top of a vehicle that has turtled

Wearing water proof gloves and high ankle boots is always recommended.

Behram Sir, that scorpio pull looks scary. What exactly is happening out there?

Last edited by The Wolf : 9th July 2010 at 21:50.
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Old 9th July 2010, 21:52   #59
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Quote:
Originally Posted by DHABHAR.BEHRAM View Post
Dear Sharath - if the Jeep is built with such a driveline ratio that you are apprehensive that it will slide down even in low 1st, the best option is to winch it down in reverse (because most Jeeps have the winch in the front). It is always better to have a winch at the back also. See the photograph attached, something I did some time back. Without a winch, I agree with Robinson's comment of going down inch by inch. If it still slides, PRAY!
Behram, I am not talking about an extreme case. Often it is possible to slide down in 1st low if the terrain is slippery. I am referring to the long steep slope on EXAMM day one where I provided some excitement. Jeeps with AT or HT tyres were sliding in 1st low while coming down. Applying brakes while sliding won't work. Later Jayesh (jack33) recommended pressing the chamcha whenever there is a slide. What would you do, and what did you do there?
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Old 9th July 2010, 22:35   #60
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Behram, I am not talking about an extreme case. Often it is possible to slide down in 1st low if the terrain is slippery. I am referring to the long steep slope on EXAMM day one where I provided some excitement. Jeeps with AT or HT tyres were sliding in 1st low while coming down. Applying brakes while sliding won't work. Later Jayesh (jack33) recommended pressing the chamcha whenever there is a slide. What would you do, and what did you do there?
Hey Sharath, theoretically and from what I have learnt from several sources- the best is the technique Jayesh suggested...but there is a subtle knack to it. Accelerate only when you feel that he vehicle is going sidewards. If the vehicle is sliding slowly in straight line you can wait for a fraction to see if the vehicle will regain traction after traversing a couple of feet. If its completely evident that the traction cannot be regained and the vehicle is gaining too much momentum and will crash land into something in front, well, no choice again, squeeze the throttle till you believe is necessary and immediately pump &release the brakes at tandem quickly ...and alternate this technique till you regain traction. If not of this works, upgrade to better tires next time.

While doing the above ensure as much as possible turn into the slide holding the steering firmly...coz you dont want a piece of rock to flip-turn your steering in the wrong direction when most is already lost!!!
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