Team-BHP - Off Road Driving Techniques

Quote:

Originally Posted by Samurai (Post 2593370)

Exactly. If you consider the basic physics, the rotational momentum of the flywheel is directly proportional to the mass of the flywheel. I think it also depends on the radius of the flywheel, but my science gets shaky at that point. So my point is, if you have bigger/heavier flywheel combined with higher revvs, you may not have to pump/modulate the A-pedal to maintain the flywheel momentum. The lighter flywheel or lesser gear ratios (say 4.27) may need the modulation/pumping action. Newton's first law actually.

Not really, I have climbed with constant throttle in really long inclines in Munnar, Coorg, Beltangady, etc.

Yes, it is neither obvious or visible. So I wonder whether this effect exists.

Yes, pumping will work in every gear. But constant throttle won't work beyond 2L in a 5.38 ratio axle.

This probably explains why Peugeot at 5.38 ratio may not need modulation in 1L or 2L.

What I am saying is simple. Constant throttle works if you are at 2L or below in a 5.38 ratio diesel Jeep. In Jeeps with lighter ratios or lighter flywheel, pumping/modulating might be necessary.

Thanks, as I mentioned before I don't know what Prado did, let's hope somebody else will pitch in with the details.

Hi Sharath,

This is a trick not some hard and fast rule.

I will answer, try to explain in points.

1) Pumping the throttle is a trick it
i) Prevents extra torque at the wheels where it will again start slipping.

ii) Allows you higher engine RPM without sufficient speed gain.

iii) Allows you to drive a higher RPM, with out redlining the engine.

2) The effect exists because the Entire Mass (especially concentrated at the belt of the tyre) of the Tyre speeds up and slows down in Fraction of a second, this is obvious in muddy terrain where this technique allows the MT Type tyres to self clean.

3) Depends on what constant throttle is if you again aim to hold a steady 1100-1200 rpm with the A-Pedal input you will achieve similar results to pumping the throttle.

4) Throttle Modulation is trick not a necessity.

5) Try the throttle modulation especially on a CJ500D and the results will surprise you.

Regards,

Arka

Quote:

Originally Posted by Jaggu (Post 2593442)

Theory aspect i could also relate but what am talking about is what happens in real life, since flywheel weight is just one of the many factors.

But whatever happens in real life should have a theoretical explanation. That is what I am seeking.

Quote:

Originally Posted by Jaggu (Post 2593442)

How can you say that the other method is NOT more efficient?

In the initial days of getting my Jeep, I did try the pumping action since it was fresh in my mind from the training. But I didn't gain any extra advantage, so I left it alone. The only times I pumped and found it useful was in 1st High. That is probably because 1st high is a lighter gear than 2nd low. That is I why came to the conclusion that 2nd low can maintain flywheel momentum without pumping in my Jeep.

Quote:

Originally Posted by Jaggu (Post 2593442)

And wont the revs vary inspite of steady throttle from you, based on the traction offered? So modulation of rpm is anyways happening.

No, when I say constant throttle, I mean constant rpm. Constant/steady rpm means constant flywheel speed.

Quote:

Originally Posted by Jaggu (Post 2593442)

The CJ3B manual should have some facts researched to mention it right?

Sure, I want to understand why.

Quote:

Originally Posted by Jaggu (Post 2593442)

On the contrary with modulation you would have superb capabilities at low speed crawling, especially on rocky terrain.

Never had issue in low speed crawling until now.

Quote:

Originally Posted by ex670c (Post 2593493)

1) Pumping the throttle is a trick it
i) Prevents extra torque at the wheels where it will again start slipping.

When you have barely enough traction, if you pump, won't you lose traction?

Quote:

Originally Posted by ex670c (Post 2593493)

ii) Allows you higher engine RPM without sufficient speed gain.

Automatically taken care in 5.38 ratio. And thanks to heavier flywheel, the momentum is not lost easily.

Quote:

Originally Posted by ex670c (Post 2593493)

iii) Allows you to drive a higher RPM, with out redlining the engine.

This may be true. But I have never redlined so far.

Quote:

Originally Posted by ex670c (Post 2593493)

2) The effect exists because the Entire Mass (especially concentrated at the belt of the tyre) of the Tyre speeds up and slows down in Fraction of a second, this is obvious in muddy terrain where this technique allows the MT Type tyres to self clean.

Still having hard time with this one.

Quote:

Originally Posted by ex670c (Post 2593493)

3) Depends on what constant throttle is if you again aim to hold a steady 1100-1200 rpm with the A-Pedal input you will achieve similar results to pumping the throttle.

Obviously I mean rpm. Hmm, what else can I mean? When the Jeep bouncing and bobbing, there is no way I can manage to keep my foot angle on a-pedal absolute. I use the engine noise to gauge the rpm and maintain that noise volume. I don't even have a tacho meter.

Quote:

Originally Posted by ex670c (Post 2593493)

4) Throttle Modulation is trick not a necessity.

Thanks, that is what I am trying to say.

Quote:

Originally Posted by ex670c (Post 2593493)

5) Try the throttle modulation especially on a CJ500D and the results will surprise you.

I won't be surprised. Doesn't CJ500D have 3.73 axle ratio? While climbing at low speeds, there is no choice but pump that A-pedal. If not, it might just stall within seconds.

Quote:

Originally Posted by Jaggu (Post 2593824)

Thanks for agreeing, thats where it started. Santhosh was given a "trick" to conquer an obstacle. Trick is not evil, its just another smarter approach. :Cheering:

And I only said it depends on the vehicle. Check the first post on this thread, which started it all.:)

Quote:

Originally Posted by Jaggu (Post 2593824)

Maybe you can try it in your backyard this weekend and update us if this really helps, atleast you are lucky to have such an area right where the jeep is parked.

Arrey boss, I am not unfamiliar with the technique. Arka taught that to me in rocky terrain of Kellambakkam four years back, I have used it in MM540 and even in 1st low in my Jeep. And I know it is very useful Gypsies since I see Sachin always pumping the A-pedal. But I find it useless in 2nd low in my Jeep, that's all I really wanted to say. And 90% of my of offroading happens in 2nd low. Check my first post in this thread. There I have also mentioned constant rpm at least twice.

I guess you have to drive my Jeep in 2nd low while climbing to understand it. For example, I didn't pump A-pedal while climbing Robi point in Avalakonda. I know you were right there, what problem did you see in my climb?

Quote:

Originally Posted by Samurai (Post 2593854)

And I only said it depends on the vehicle. Check the first post on this thread, which started it all.:)

Agree it depends on the vehicle! and it will work in almost ALL vehicles also! in different situations with varying results.

Quote:

Originally Posted by Samurai (Post 2593854)

I guess you have to drive my Jeep in 2nd low while climbing to understand it.

What made you think that i have NOT driven such a combination? Had the exact combo (not exact it was a 3 speed) in the LHD Willy mentioned in the DwArF thread opening post. Drove it for years, why do you think i never was keen on diechel CJ's and opted for a petrol? ;)

Still i would definitely take up your offer and try out in one of the OTR's.

Quote:

Originally Posted by Samurai (Post 2593854)

For example, I didn't pump A-pedal while climbing Robi point in Avalakonda. I know you were right there, what problem did you see in my climb?

I was on top (IIRC) and very honestly dont have a clear memory of your climb. But i really want to understand why you are so hell bent on thinking that i believe your climb or technique is wrong or does not work?

When did i ever say that?!! :D

All i am saying is maybe you can try some other techniques also, instead of repeating again and again that its not needed or its absolutely useless, maybe in your CL but works wonders in most of the other vehicles.

Maybe we can have a one on one challenge next time, your vehicle same obstacle same gear but different driving style he he he

One of the topple at that very exact spot was a result of a pointless constant rpm climb, and i guess thats when the marshals decided to step in and prompt the drivers. Oh by the way, we had one another thing which we were watching, which tyre the vehicle were running.

EDIT: In my endeavor to find the truth, i used google to find this from guruji!

Quote:

Originally Posted by Jaggu (Post 2593895)

Not the same. Lighter flywheel, in fact 1/3rd times lighter. It will lose momentum lot faster. Now, who has a diesel SWB with 5.38 axle ratio and open diffs in BODA? Try with that vehicle.

Quote:

Originally Posted by Jaggu (Post 2593895)

Well, you keep saying modulation is always the better technique. And I am saying it depends on the vehicle and gears. That's the difference.

Quote:

Originally Posted by Jaggu (Post 2593895)

instead of repeating again and again that its not needed or its absolutely useless

I only said it is not needed in 2nd low of my Jeep. When did I say it is absolutely useless? I do use it in higher gears and would use it in other Jeeps.

Quote:

Originally Posted by Jaggu (Post 2593895)

Maybe we can have a one on one challenge next time, your vehicle same obstacle same gear but different driving style he he he

Sure, I have driven my Jeep enough to know what works in 2nd low.

Quote:

Originally Posted by Jaggu (Post 2593895)

One of the topple at that very exact spot was a result of a pointless constant rpm climb, and i guess thats when the marshals decided to step in and prompt the drivers.

Now constant rpm is a pointless thing? :eek: See what Arka said a while back:

Quote:

Originally Posted by ex670c (Post 2593493)

3) Depends on what constant throttle is if you again aim to hold a steady 1100-1200 rpm with the A-Pedal input you will achieve similar results to pumping the throttle.

He feels steady rpm is same as pumping the throttle. So where does it put us?

Quote:

Originally Posted by Jaggu (Post 2593895)

EDIT: In my endeavor to find the truth, i used google to find this from guruji!

And what does Arka say there? Use Throttle Modulation to achieve high flywheel speed. That is the objective, flywheel momentum.

Quote:

Originally Posted by Samurai (Post 2593926)

Not the same. Lighter flywheel, in fact 1/3rd times lighter. It will lose momentum lot faster. Now, who has a diesel SWB with 5.38 axle ratio and open diffs in BODA? Try with that vehicle.

Arre it was a diesel motor only! Only the box was 3 and iirc yours is 4 speed, same diff ratio.

Quote:

Originally Posted by Samurai (Post 2593926)

Well, you keep saying modulation is always the better technique. And I am saying it depends on the vehicle and gears. That's the difference.

Yup and i really dont have more science right now to prove it, so let it be.

Quote:

Originally Posted by Samurai (Post 2593926)

I only said it is not needed in 2nd low of my Jeep. When did I say it is absolutely useless? I do use it in higher gears and would use it in other Jeeps.

Thanks for clarifying :D

Quote:

Originally Posted by Samurai (Post 2593926)

Sure, I have driven my Jeep enough to know what works in 2nd low.

Goodie it would be a great challenge for me to see if the belief holds up.

Quote:

Originally Posted by Samurai (Post 2593926)

Now constant rpm is a pointless thing? :eek: See what Arka said a while back:He feels steady rpm is same as pumping the throttle. So where does it put us?

:eek: you are becoming like indian journo's. He said constant rpm at around 1100-1200 RPM also. When i meant constant RPM i never said the rpm, am not that good to figure out the rpm standing below a climb, but am sure it was much higher. Atleast sounding much much higher, and i guess your CL was also in a higher RPM on that climb? 1100-1200 in 2L in CL = what kind of speed?

Quote:

Originally Posted by Samurai (Post 2593926)

And what does Arka say there? Use Throttle Modulation to achieve high flywheel speed. That is the objective, flywheel momentum.

Yeah and your jeep holds high RPM in 2nd gear so far. I guess you are good enough driver to always be in the right gear.

Quote:

Originally Posted by Frankenstein (Post 2594203)

The 3 speed gearbox + 5.38 combo does not give so much torque like a KMT90+5.38 or that matter KMT90+4.88.The ratios in the 3 speed 1st and 2nd gear are tall.
I tired pumping on climbs , but lost momentum and had to go full throttle .

Quote:

Originally Posted by Frankenstein (Post 2594203)

Pumping helped me in slush .

Absolutely, it helps the tyres from getting stuck in pasty wet mud. I do use pumping in heavy slush, but I switch to 1st High in such cases. My 2nd low is not really pumping friendly.:) I had to do it in Somwarpet this time.

Quote:

Originally Posted by Frankenstein (Post 2594203)

where in our XD3p,G1/307 we need to pump and rev more.

XD3P with what axle ratio?

Quote:

Originally Posted by Sudarshan (Post 2594232)

This May be:OT
But IMHO Listening can be quite deceiving ---I have experienced it twice

That may be, but I am not aiming for a particular rpm value. I know at what engine loudness I can safely avoid stalling, so I stick to that. I really don't know what is that rpm value.

Quote:

Originally Posted by Samurai (Post 2594361)

That's interesting. What are the ratios of the 3-speed gearbox?

For my XDP engine CJ340 with 12kg flywheel, these are the crawl ratios in descending order:

1st Lo - 52.75 - Don't need to pump A-Pedal to maintain flywheel momentum
2nd Lo - 31.34 - Don't need to pump A-Pedal to maintain flywheel momentum
1st Hi - 21.44 - Need pumping to maintain flywheel momentum
3rd Lo - 19.49 - Need pumping to maintain flywheel momentum

Let's not worry about the rest, they are no good for offroading.

Absolutely, it helps the tyres from getting stuck in pasty wet mud. I do use pumping in heavy slush, but I switch to 1st High in such cases. My 2nd low is not really pumping friendly.:) I had to do it in Somwarpet this time.

XD3P with what axle ratio?

That may be, but I am not aiming for a particular rpm value. I know at what engine loudness I can safely avoid stalling, so I stick to that. I really don't know what is that rpm value.

The 3 speed ratios are

1ST GEAR , 2.9:1
2ND GEAR, 1.5:1
3RD GEAR, 1:1

So the crawl ratio in 1st gear is 37.4 with 5.38 ratio.

XD3P with the standard 4.88 in the MM550.

Hi,

I tried to attempt a mini OTR kind of driving over small stones on the empty stream-bed near Puthur. While I switched over to 4WD H, 1 Gear and started the drive

Off Road Driving Techniques-thar_stone_1.jpg

in the middle, got struck at one point, with a big rock below my left rear tyre - see photo below:

Off Road Driving Techniques-img_rock_1.jpg

I tried to switch to 4WD Low, 1st Gear and tried to accelerate. This only resulted in the front wheels spinning and getting into the gravel:

Off Road Driving Techniques-img_rock_2.jpg

Finally, I reversed the vehicle, and then went further straight ahead of the rock that was getting below the left tyre and then moved out.

I believe that it is something with the technique, due to which the vehicle did not climb over that rock & the wheels spun.

can someone please comment on what would have been the right way to tackle this position?

I am planning to re-visit the same place in April 21/28, and would try out whatever is recommended.

thanks
Siva