Go Back   Team-BHP > Buckle Up > 4x4 & Off-Roading > 4x4 Technical


Reply
 
Thread Tools Search this Thread
Old 19th July 2011, 18:31   #166
BHPian
 
smsrini's Avatar
 
Join Date: Sep 2007
Location: Bangalore
Posts: 981
Thanked: 223 Times
Default Re: Offroad Driving Techniques

16) When ground conditions appear difficult, such as rocks, ruts, etc., it is advisable to select a path by foot prior to driving through, thus reducing
the chance of getting stuck or damaging your vehicle. The use of a spotter is also recommended. The use of a spotter is always a good idea.

17) Exercise care when applying the throttle. Excess throttle will cause wheel spin (digging) and could stop forward movement. Donít dig with your wheels, otherwise youíll be digging with a shovel!

18) Momentum of a fast moving vehicle will always overcome the drag and reduce the traction needed from the wheels. When it is clear that NO obstacle is in the way to cause damage, a fast approach to a steep hill, soft sand, mud, etc., can very often be effective.Keep wheel spin to a minimum, thus keeping
forward movement.

19) When crossing ditches, ruts, logs, etc., always try to keep as many wheels as possible on the same type of surface. Avoid getting the wheels airborne. Also ditch & log crossing should be done at 45-degree angles, not head on, thus keeping traction loss to one wheel only.

20) Always be aware of obstacles under your vehicle, keeping in mind you only have so much ground clearance. Avoid existing deep ruts, sudden changes in slopes, plus remember your approach and departure angles.Always be aware of where your Left-Rear tire is, and what it's about to contact.

21) Maximum advisable wading depth is approx 20-inches. If equipped, fit the bellhousing wading plug prior to setting out. Make sure your engine air intake does not suck water, otherwise great engine damage will occur. Though some vehicles are known for driving through deep water, we donít suggest it (you need specialized vehicles & equipment). If you have to cross that stream, survey it first. If the water is glass smooth and you canít see the bottom, a muddy bottom is usually the norm. If choppy and rough, rocks are then the cause. When surveying youíll have to check depth, current speed, condition of the stream bottom (does it offer traction or not?). Donít try driving against the current, and if you have to cross, take it a right angles, or angle your way down stream to the opposite bank, letting the current help you along. You are in... donít splash, this will normally cause an engine to be soaked (causing
it to quit, or suck water down the air cleaner). Begin slowly and create a "bow-wake", taking care to keep a steady speed.

22) After driving through deep water (or mud), make sure your brakes are dried out immediately, thus being fully operational when needed. This can be done by driving a short distance with the brake pedal applied lightly. You should also check your air filter for water.

23) When dealing with mud, refer to #10, 13, 14, 15, 16, 17 & 18 for starters. Now think about what gear youíll use, we normally try second gear low-range (possibly 3rd with a V8 & automatic), keep a steady speed, not too fast, and try not to spin the wheels, as if they are, you are not going forward. If you loose forward movement, lift off the throttle slightly, enough to stop the spinning and see if you regain traction, normally you well. Throttle control and traction is the key to driving in the mud.

24) Should you get stuck, careful thought and experience will usually provide a solution. However, the trick is not to get stuck in the first place.
The idea of having a winch is great, but just in case you donít have one, look at your situation, then clear any/all obstacles from in front of all four
tires. Adjust air pressure as necessary, then begin a rocking motion (forward-reverse, etc.). In most cases it will do the trick. If not, it may be
necessary to jack up the car and place rocks, matting, etc., under the tires for added traction. It may also be necessary to remove all payload from the load space area.

25) Driving in the snow can be a daily chore for some, or fun for others. The problem isnít the snow, but the ice under it. Letís talk freeway snow driving: Youíre headed east for Reno over Donner Pass, the summit is some 7300 feet above sea level, the snow line begins a 3000 feet, the CHP has a chain requirement up and is advising all to stay away. So what do you do? Head for the mountains no doubt. Whether you are going skiing for the weekend, or on business, if the CHP has warnings and requirements up, stay home! That cures that, right? No? Like most youíll go anyway, clogging the roads for all those that have to get across. Donít, stay home... please.

So you run into driving snow at 3000 feet, by 4000 Cal-Trans has the road blocked checking for chains or 4wds with snow tires (see #26). From this point on the road is white, your vehicle type will have a lot to do with whether or not youíll have an easy time of it. Lets take a Range Rover first, post-í88 with a viscous coupler transfer (these vehicles are full-time 4WD). Really you donít have to do a thing, just drive it. For example, if youíre in a Land Rover Discovery or Defender, or a pre-í89 Range Rover, these are fitted with a manual center-diff-lock (still full-time 4WD), and when encountering slick areas such as snow covered roads (or mud), the center-diff must be locked to obtain maximum traction. Leave it locked until blacktop appears from under the snow and traction has be regained (center-diff-lock may be operated at any speed). Now youíre driving a Ď96 Trooper with a V6, or a Honda Passport, now what? Itís in 2WD most of the time, and engaging 4WD on a snow covered road requires slowing and/or stopping in order to engage high-range 4WD (read your manual).
Now, some of these vehicles limit the speed in which you can travel in 4WD high-range (meaning highway speed ratio), thus youíll again have to research such things with your dealer. Anyway, 4WD must be engaged otherwise youíll have no traction, thus no control, and possibly no forward movement. In fact, the CHP could require you to fit chains, or worse yet, turn back. The Bravada, and vehicles like it, the owner should be concerned when in snow conditions, as though they are built as a street type 4-wheeler, and are not an off-road vehicle, and can do quite well in snow conditions (plowed) with the right tires fitted, they still have no low-range capabilities, thus in extreme conditions can be no better than the average car fitted with chains. As said earlier, the snow isnít so much the problem, except visibility (keep your lights on low-beam, no driving lamps, but fog lamps okay -yellow even better), its the ice under it. ABS braking is the current fad, and though "ORE" doesnít endorse ABS as a whole, this is one of the few times they show their worth. Driving in
the snow is like racing motorcycles in the rain... you have to be smooth. Donít use abrupt throttle openings, heavy braking, or quirky steering movements. Apply the throttle smooth and steady. Do all your braking in a straight line (release the pedal prior to making your turn). If in a bad situation, do not lock the wheels up with the brakes! Down shift as necessary, engine braking will slow the vehicle straight and smooth in most cases. Make your turns in a nice smooth arch, donít jerk the wheel. Think egg shells. Remember that braking distances have increased ten fold, thus youíll have to adjust your driving habits... donít follow so close (as you might do in commute traffic), stay off the brakes if at all possible - down shifting instead of constantly dragging on the brakes; stay in one lane - changing lanes can be deadly due to berms of built up snow between the lanes. If youíre spooked about driving in adverse conditions you have two choices; a) stay home, or b) take one of our classes that deal with such.

Hereís a little story.... A gentleman calls about our classes, says heís just bought a new Jeep, replacing the one he totaled out on Donner during the winter. "What happen?" I asked, "I was coming down the mountains, it was snowing hard, then all of a sudden it spun and I went down an embankment!" he replied. I asked one question of him... "Did you have the brakes on?" "Why yes, and it still wouldnít stop!". WRONG! No brakes! Lightly if you have to.

Hereís another one... The "ORE" crew is heading home on I-80, while Blain passes the Nevada City exit he finds a Toyota 4WD pickup sideways in the road stopped (very dangerous!). Blain stops, gets out and talks with the driver and his wife, both of whom are freezing cold inside, and Blain asks if they need help. They say they canít get up the grade, "the truck keeps going sideways". Blain asks if the driver has 4WD engaged, the driver replies "yes!". Blain proceeds to ask if the driver has any chains, which are quickly produced, then goes about fitting them (though the tires were marked "M&S", they were not the type that should be in such conditions). Blain completes fitting the chains and instructs the driver to proceed, that he would follow him up the grade, or tow him if needed. With that, the couple crank up their truck, but it wonít move, the rear wheels (one of them) was spinning, but no action up front. Blain has them hold up, then checks the locking hubs up front. Guess what? They werenít locked! When in doubt, stay home, or... take our class regarding winter time driving.

Hereís another one for those with children out and about. During the same driving blizzard that Blain came across the Toyota, John and Michael would come need as well. Descending down the mountain a set of lights were spotted coming up, it is difficult to tell whoís doing what with all that
snow falling. As they approached said lights, they noticed the lights were stationary and off to the right. Moments later theyíd find an S10 Blazer backed down into a snow drift, three young college girls inside wondering what to do next. After checking on their health, the age old question of... "do you have it in 4-wheel-drive?" was asked, "I think so" was the reply from with in. "Okay then, put it in second gear and lightly touch the throttle and weíll see what happens", the rears spun. After engaging 4WD low-range and again applying throttle, the Blazer refused to move, its chassis hung up on the drift. With that now known, the only alternative was to winch them out. With the winching in progress John informed the young ladies of the "ORE" classes and handed them some information, to this day weíve never heard from them. Normal. Just think about what could have happened had circumstances been only slightly different. Letís not.

Off-roading in the snow can be a blast, though caution is the word of the day. Since your off-road, you can be sure no one has plowed the road or trail ahead. Snow packs quickly when in front, or under your vehicle, a drift of only minor depths can strand you, leaving you with digging and/or winching your way out. When in doubt, survey it. Walk through it, find out how deep the snow is before you drive 5000-pounds of 4WD into it. Though while driving in it, depending on depth and pack, again use smooth throttle, braking and steering methods. Remember that when on a dirt trail/road that the snow will freeze the puddles under it, and every now and again sheets of flying ice may appear as you tear across the surface.

26) Tires or Tyres... There are so many different types of tires available now days that choosing the correct one for you and your vehicle may get a bit confusing. Consider where you live (snow belt or sunny California). Think of your primary use first, then consider how much off-roading you really do. If youíre commuting everyday, you really donít need Mud T/Aís. Donít over-tire your vehicle either. Always remember that all wheels, including the spare must be of the same type, size and make. If your vehicle is equipped with a space-saver spare, get rid of it immediately. These so-called spares are more trouble than they are worth, in most cases all but useless. If youíre off-road, or worse, chained up, and you have a flat, now what? If youíre chained?...
Letís say your right-rear tire is flat, youíll first have to jack up the front and fit the space-saver, then transfer the proper wheel/tire to the right-rear, where the chains can then be refitted. A lot of work. If you didnít do so, and fitted the space-saver on the right-rear, youíll quickly find out that the chains do not fit. With only one wheel chained youíll go nowhere. When off-road, you will now have a tire smaller than the others, which isnít good for the axles and transfercase gears (this applies to any spare tire not of the same size as those fitted to the vehicle), nor is it very helpful when traction maybe needed to get back to pavement. A number of tires, though marked "M&S", are not legal by CHP or Cal-Trans standards, so beware! On a recent trip we spotted a number of 4wd suvís chained up while crossing Donner Pass, this was due to the type of tires fitted, i.e.; road bias type. This is something we donít understand. A number of 4wd owners (and dealers) have a nasty habit of fitting overly large tires to their 4wdís. It may look good, but chances are it has a number of draw backs. The larger the increase in tire diameter, the more the final drive gear ratio is effected, as is performance. Large tires also effect hub bearings, steering, as well as suspension and ride, the latter two relate to excessive un-sprung weight on the axles. Finally, the speedometer will no longer read correctly. Todayís electronic speed-oís are nearly impossible to re-calibrate. When considering changing the tires size and rim width/dia, check with a real expert, one that will give you the complete story (beware of those just trying to make a sale). As already stated elsewhere, tire pressures can be adjusted to increase traction (and improve ride), but they must be re-inflated prior to road use, otherwise heat build up can cause tire damage and/or blowouts, handling will also be effected. Excessive tire pressure will give a poor ride and poor handling. Check your owners manual first, then tire manufacturer specifications. Do not blow the tires up to their maximum for general road & off-road work, itís too high. Having the correct tires while off-road, and in the snow, will only benefit you.

27) Snow chains... How many of you own them? How many have used them? Believe it or not, chains are not only a benefit in snow and ice, but can work wonders off-road as well. If in very slick mud conditions and forward progress is near nil, try fitting the chains (correct sizes with rubber or spring straps, not cable-chains!), youíll be surprised. Which wheels do you fit them on? Normally on the rear, even more so when climbing up hill, or towing, as the weight transfers to the rear wheels, thus giving you maximum traction. In some cases it may be necessary to fit them to the front, or all four (4) wheels. Just because you own a 4WD, donít think youíre immune to chaining up while in the mountains, youíre not.
Even the best 4wd's need snow chains now and again. In the snow or mud, carry a set.

28) Rocks, these can be tricky, and itís almost an art, either of getting through, or smashing your car (ala Rubicon). When off-road however, youíll always encounter rocks of some sort or another. Careful driving and spotting can help you avoid vehicle and wheel/tire damage
(be careful with the sidewalls on your tires, rocks can tear them open). Survey the area chosen first. Walk it. Use your spotter as necessary. Find that path through. Drive slowly and with caution, remembering your ground clearance, approach/departure angles, plus your break-over clearance. If rocks are too large to put under your car, youíll have to go around, or... over them. Be careful. Hereís another story weíd like to share with you. Daddy buys young son a new 4WD for graduation, $35K kind of money. One day vehicle arrives at our shop on a tow truck. With only 4000 miles on the clock it has four flat tires, four damaged rims, a bent front bush guard, rear lamp guards ripped off, the front axle bowed, and paint scratched to death. We asked what and where this had happened, the reply being "we were on the Rubicon!". "What part?", we asked. After a chat, it seems the young 4x4 driver had sped into a large rock field, not having a clue that heíd have to walk the vehicle up and over the immovable obstacles, the expensive damage was the end result of his lack of experience and knowledge.

29) Hill climbing, some think, is a sport in itself. When you see off-roaders rushing up a particular hill for the sole reason of getting to the top,
you can be sure trouble isnít too far behind. In most cases this is a useless sport, damaging the trails, and usually the vehicle (everything from broken
axle shafts from excessive wheel spin, to roll overs). If you have to go up, refer to #14 & 18 for starters. Should your vehicle stall part way up, donít
panic! Quickly hold the brakes, engage reverse (re-start engine if needed) and release all pedals, letting the vehicle back down in gear via engine braking, stay off the brakes! With the engine now above you, and the weight shifted onto the rear axle, your vehicle is quite unstable and can go into roll-over-mode very easy. If... the front end begins to slide to one side, quick use of the throttle will straighten the vehicle out, as soon as its once again straight with the trail, release the throttle, DO NOT touch the brakes, as the front end will try to pass the rear when the weight shifts further. Weíve seen what happens to a number of these types of off-road wrecks, sometimes with nasty and deadly results.

When coming down front first, engage low-range/first gear and then nose it over the edge. Let the engine and gearbox do all the work (engine braking).
Donít panic, try and stay off the brake pedal. If it starts sliding, touch the throttle enough to overcome (out run) the slide, then release the pedal
once again letting the engine do its thing. Easy really.

30) Side slopes are another hazard of off-roading. Some vehicles can operate on a 45-degree side slope, but only with traction. Basically, try to avoid such dangerous situations when possible.

31) Donít overload your vehicle. Keep in mind that loads should be distributed evenly within the vehicle if at all possible. Loads behind the rear axle will sag the rear of the vehicles, thus limiting departure angle/clearance. When a roof rack is fitted be extremely aware of weights and how they are distributed. Excessive loads will change the center-of-gravity, thus making the vehicle less stable. Also, beware of the additional height of the vehicle with the rack fitted.

32) Once clear of your off-road area it is most important that you check over your vehicle completely before commencing with your highway travel.
It is important that the vehicle is checked over completely for leaks or brush hanging from the frame, or anything else that could prove hazardous to you and your vehicle or other drivers before commencing freeway speeds and travel. Be sure to check & inflate the tires.

33) A quick and brief reminder...

Remember to Check out difficult or unfamiliar terrain.
Remember to drive smoothly with throttle, brake and steering control.
Remember to use common sense, it may be all you have.
Remember to always wear your seatbelt.
Remember to drive with in your abilities, not over your head.
Remember to never go out alone.
Remember to use 1st gear/low-range on down hills... engine braking.
Remember to always check your car afterwards, re-inflate tires, etc.
Remember to TREAD LIGHTLY!
smsrini is offline   (1) Thanks Reply With Quote
Old 19th July 2011, 18:34   #167
BHPian
 
smsrini's Avatar
 
Join Date: Sep 2007
Location: Bangalore
Posts: 981
Thanked: 223 Times
Default Re: Offroad Driving Techniques

Now the question that bugged me to search for these techniques:

If you have to drive thru a badly rutted ( deep ruts with a hump in the middle ) trail, what is the best option ?

- Drive thru with wheels in the ruts, straddling the hump ?
- Drive with the wheels on the humps on either side of a rut ?

Offroading gurus, please share your experience. Please feel free to correct any of the techniques mentioned in the previous posts based on your experience.

thanks
smsrini is offline   Reply With Quote
Old 19th July 2011, 20:10   #168
Distinguished - BHPian
 
dhanushs's Avatar
 
Join Date: Oct 2009
Location: Bathery/BLR
Posts: 3,407
Thanked: 3,930 Times
Default Re: Offroad Driving Techniques

Quote:
Originally Posted by smsrini View Post
Mods: I could not find a thread on this topic, and hence have started a new one.
Hey smsrini, a thread with the exact same title exist - http://www.team-bhp.com/forum/4x4-of...echniques.html
dhanushs is offline   Reply With Quote
Old 11th November 2011, 15:37   #169
BHPian
 
Join Date: Sep 2009
Location: Bangalore
Posts: 46
Thanked: 3 Times
Default Re: Off Road Driving Techniques

Note from the Team-BHP Support Team: Post deleted. Please post this on the right thread of 4X4 section. Go through all the thread headings and see where your post fits.

Last edited by Rudra Sen : 11th November 2011 at 16:31.
parashakthi is offline   Reply With Quote
Old 28th November 2011, 18:31   #170
Team-BHP Support
 
Samurai's Avatar
 
Join Date: Jan 2005
Location: B'lore-Manipal
Posts: 22,052
Thanked: 13,500 Times
Default Modulating engine rpm while climbing slippery slopes

Quote:
Originally Posted by svsantosh View Post
I dont recollect exactly, but I think it was Jaggu/Vijay Reddy who said what needs to be done to clear this challenge - PUMP the A-Pedal. Keep the momentem up. Even flooring it all the while will result in RPM dying slowly on you...
I guess that depends on the vehicle. In my Jeep I never have to pump when I am in 2nd low. I can maintain a steady pace during the climb while holding the A-pedal steady, may because of my 5.38 ratio, revvs are pretty high even at lower speeds.

Lot of people make the mistake of letting go or ease on the A-pedal, if the vehicle slows down during a climb. It is an on-road habit, shouldn't do it offroad during a climb. I keep the rpm steady no matter how my Jeep is moving. If I am stationary due to slippage, I still keep the rpm steady and turn the steering each way until some traction can be obtained. Once I told a bystander to put some weight on my left side foot step, and I took off since my rpms were steady.

This is from a 2 year old OTR report:

Quote:
Originally Posted by Samurai View Post
So I looked out at the front tyre on my side, it was stationary despite my revving. That means, front right tyre had traction, so the left front tyre must be spinning thanks to the open differential. That made sense because I had nobody in the passenger seat. I looked beyond the passenger seat and saw a marshal standing there. I shouted “weight, weight… give me weight” while pointing at the left side. He instantly understood and put his one foot on the left foot rest of the Jeep. And… Wow, the Jeep got the traction it needed and I crawled out of the gravel and reached the top within seconds. It felt nice to overcome the hurdle by understanding the problem and applying the right technique, and see it actually work!

Last edited by Samurai : 28th November 2011 at 18:35.
Samurai is offline   Reply With Quote
Old 28th November 2011, 21:54   #171
Team-BHP Support
 
Jaggu's Avatar
 
Join Date: May 2004
Location: Bangalore
Posts: 17,498
Thanked: 6,782 Times
Default Re: Avalakonda OTR 2011 : A Late report

Samusan i feel a slight modulation of throttle actually helps in getting that traction, just like steering but much more effective. I still remember one of the climbs in last to last AKC, steady throttle was not helping me in the Invy, steering left to right also did not do much. But the modulation from the throttle got the tyres gripping on-off-on-off and could get out of the situation. Mind you that climb was much more challenging though the danger was much much lesser. Same with the super slippery Somwarpet climb where the stock gypsy climbed up without any external help.

By modulation am not saying cut the throttle, just lil bit of variation of RPM's and one would definitely know the range where the power range is.

Also relying on that ratio and diesel engine is not completely bullet proof, in certain boulder ridden steep climbs one has to modulate or you will land up in very awkward angles with the shifting stones. Especially since you have such low ratios and diesel engine, first gear modulating throttle would give super "rock climb" capability. Same would be a pain in slippery surface like slush or loose soil, where second gear and modulation would make it very easy to cross over. The second obstacle where you found it difficult to climb that boulder, modulation would definitely would have helped. Me feels.

Maybe Arka and others can explain better.
Jaggu is offline   Reply With Quote
Old 28th November 2011, 22:14   #172
Team-BHP Support
 
Samurai's Avatar
 
Join Date: Jan 2005
Location: B'lore-Manipal
Posts: 22,052
Thanked: 13,500 Times
Default Re: Avalakonda OTR 2011 : A Late report

Quote:
Originally Posted by Jaggu View Post
Samusan i feel a slight modulation of throttle actually helps in getting that traction, just like steering but much more effective.
Four years back when I attended the offroad training at Kellambakkam, pumping the A-pedal was one of the things that I was taught. But the purpose was different. Arka called it fly-wheel driving or something like that. It was done to keep the fly-wheel momentum higher than usual for that speed. But if you have a ratio that keeps your revvs high or flywheel momentum high enough, pumping may not be necessary. That is my understanding.

If am not mistaken, pumping the A-pedal will actually makes you lose traction than gain it. Pumping tends to send more torque than required, making the tyres slip.

If I am wrong, I want to understand exactly why.
Samurai is offline   Reply With Quote
Old 28th November 2011, 22:49   #173
Team-BHP Support
 
Jaggu's Avatar
 
Join Date: May 2004
Location: Bangalore
Posts: 17,498
Thanked: 6,782 Times
Default Re: Avalakonda OTR 2011 : A Late report

Quote:
Originally Posted by Samurai View Post
Four years back when I attended the offroad training at Kellambakkam, pumping the A-pedal was one of the things that I was taught. But the purpose was different. Arka called it fly-wheel driving or something like that. It was done to keep the fly-wheel momentum higher than usual for that speed. But if you have a ratio that keeps your revvs high or flywheel momentum high enough, pumping may not be necessary. That is my understanding.

If am not mistaken, pumping the A-pedal will actually makes you lose traction than gain it. Pumping tends to send more torque than required, making the tyres slip.

If I am wrong, I want to understand exactly why.
Am not saying you are wrong.

My question is, Isn't it (power being delivered to wheels/flywheel momentum needed/speed of the wheels) dependent on the kind of terrain?

In a terrain which offers very less traction (impossible to find grip), pumping helps in reducing the slip momentarily (especially in a high torque scenario) and then regain the traction, to move forward?

Yesterday we had a similar situation where a certain CJ3B, it was slipping around that i was But when the throttle action was different it performed very differently, that everyone else was

EDIT: To give you some idea have another video which i will share, you need to increase the volume to listen to the engine note and how its being varied. Trust me now its a high torque machine


Last edited by Jaggu : 28th November 2011 at 23:23.
Jaggu is offline   (1) Thanks Reply With Quote
Old 29th November 2011, 09:15   #174
Team-BHP Support
 
Samurai's Avatar
 
Join Date: Jan 2005
Location: B'lore-Manipal
Posts: 22,052
Thanked: 13,500 Times
Default Re: Avalakonda OTR 2011 : A Late report

Quote:
Originally Posted by Jaggu View Post
My question is, Isn't it (power being delivered to wheels/flywheel momentum needed/speed of the wheels) dependent on the kind of terrain?
Yes, it does. Torque is the minimum force required to rotate the wheels. If the terrain is too slippery, the wheels can be rotated with lot less torque. That reduces the work needed to be done by the engine, lowers the revvs, lowers the flywheel momentum. If you let go the A-pedal at this point, the engine will just stall. That is why you pump the A-pedal and over-revv the engine, to keep the fly-wheel momentum high. The tyres will lose traction and slip, but as soon as you get some bite, the vehicle will just take off thanks to the high fly-wheel momentum. That bite will come not from pumping, but from moving to-n-fro, lateral motion, by additional weight from somebody jumping on your vehicle.

But if you have a ratio like 5.38 that keeps your engine revvs unusually high, the pumping is not necessary. That is from driving a CJ340 since 3.5 years. I never have to pump while climbing slippery inclines in 2nd low. It may be required if I climb in 3rd low, but I seldom do that.

Quote:
Originally Posted by Jaggu View Post
In a terrain which offers very less traction (impossible to find grip), pumping helps in reducing the slip momentarily (especially in a high torque scenario) and then regain the traction, to move forward?
This I do not understand. How does pumping help reduce slip?

Last edited by Samurai : 29th November 2011 at 09:25.
Samurai is offline   (1) Thanks Reply With Quote
Old 29th November 2011, 10:07   #175
Team-BHP Support
 
Jaggu's Avatar
 
Join Date: May 2004
Location: Bangalore
Posts: 17,498
Thanked: 6,782 Times
Default Re: Avalakonda OTR 2011 : A Late report

Quote:
Originally Posted by Samurai View Post
This I do not understand. How does pumping help reduce slip?
Please read that ^^^ as modulating, not exactly pumping, within the power band. Varying wheel spin typically offers some grip, am quite sure. What you refer as rocking etc also does the same.

Am still not very convinced about the constant throttle, mind you DwArF has the same ratio and its a torque monster and a varying throttle offered better performance. Maybe DwArF has seen very little offroad but if you remember DKG was one of the smoothest in AKC and EXAM and his only weapon was the modulating right foot.

If an not mistaken the 3B offers more torque than 340? Its lighter so slips like crazy also.

Last edited by Jaggu : 29th November 2011 at 10:08.
Jaggu is offline   (1) Thanks Reply With Quote
Old 29th November 2011, 10:24   #176
Team-BHP Support
 
Samurai's Avatar
 
Join Date: Jan 2005
Location: B'lore-Manipal
Posts: 22,052
Thanked: 13,500 Times
Default

Quote:
Originally Posted by Jaggu View Post
Am still not very convinced about the constant throttle, mind you DwArF has the same ratio and its a torque monster and a varying throttle offered better performance. Maybe DwArF has seen very little offroad but if you remember DKG was one of the smoothest in AKC and EXAM and his only weapon was the modulating right foot.
Isn't there a difference between the flywheel of hurricane and Peugeot engines? Which is heavier?

Quote:
Originally Posted by Jaggu View Post
If an not mistaken the 3B offers more torque than 340? Its lighter so slips like crazy also.
When you are slipping, torque doesn't matter. Torque is a function of available traction. When the traction is good, more torque really helps. But if there is no traction, having more torque isn't useful.

Quote:
Originally Posted by Jaggu View Post
Please read that ^^^ as modulating, not exactly pumping, within the power band.
Same difference. When modulating, you are changing the revvs, but for what purpose, that is my question. I feel it is for keeping the flywheel momentum up, nothing more.


Where are you Arka? Need some clarification here. <running back to my professor>
Samurai is offline   Reply With Quote
Old 29th November 2011, 10:30   #177
Team-BHP Support
 
Jaggu's Avatar
 
Join Date: May 2004
Location: Bangalore
Posts: 17,498
Thanked: 6,782 Times
Default Re: Avalakonda OTR 2011 : A Late report

Quote:
Originally Posted by Samurai View Post
Isn't there a difference between the flywheel of hurricane and Peugeot engines? Which is heavier?
But what does that result in? ie a heavier flywheel?

Quote:
Originally Posted by Samurai View Post
But if there is no traction, having more torque isn't useful.
Yes so you reduce the torque by modulating towards lower torque.

Quote:
Originally Posted by Samurai View Post
Same difference. When modulating, you are changing the revvs, but for what purpose, that is my question. I feel it is for keeping the flywheel momentum up, nothing more.
Partially yes but also for changing the torque curve which is transmitted to the wheels. I think constant throttle works best in level or small long inclines.

Quote:
Originally Posted by Samurai View Post
Where are you Arka? Need some clarification here. <running back to my professor>
Guruji please sort out this confusion!
Jaggu is offline   Reply With Quote
Old 29th November 2011, 10:40   #178
Senior - BHPian
 
ex670c's Avatar
 
Join Date: Nov 2004
Location: Chennai
Posts: 2,454
Thanked: 1,789 Times
Default Throttle Modulation

Hi Guys,

This is definitely not my original Trick but goes back to the Willy CJ3B 4x4 Driving Manual.

Pumping the throttle/Modulating the Throttle has a few advantages

1) Like Sharath mentioned a higher Flywheel Speed/Engine Speed compared to the Wheel Speed. When you keep varying the engine speed (Up & Down) the Flywheel will tend to keep the engine running a the average speed.

this results in

2) Like Jaggu mentioned on-off-on-off effect at the Tyres, but this is not visible/obvious.

This works in all the gears.

IIRC the Peugeot Flywheel is 12kgs Hurricane is 8Kgs.

Regards,

Arka

Last edited by ex670c : 29th November 2011 at 10:42.
ex670c is offline   (2) Thanks Reply With Quote
Old 29th November 2011, 15:08   #179
Team-BHP Support
 
Samurai's Avatar
 
Join Date: Jan 2005
Location: B'lore-Manipal
Posts: 22,052
Thanked: 13,500 Times
Default Re: Avalakonda OTR 2011 : A Late report

Quote:
Originally Posted by Jaggu View Post
But what does that result in? ie a heavier flywheel?
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.

Quote:
Originally Posted by Jaggu View Post
Partially yes but also for changing the torque curve which is transmitted to the wheels. I think constant throttle works best in level or small long inclines.
Not really, I have climbed with constant throttle in really long inclines in Munnar, Coorg, Beltangady, etc.

Quote:
Originally Posted by ex670c View Post
2) Like Jaggu mentioned on-off-on-off effect at the Tyres, but this is not visible/obvious.
Yes, it is neither obvious or visible. So I wonder whether this effect exists.

Quote:
Originally Posted by ex670c View Post
This works in all the gears.
Yes, pumping will work in every gear. But constant throttle won't work beyond 2L in a 5.38 ratio axle.

Quote:
Originally Posted by ex670c View Post
IIRC the Peugeot Flywheel is 12kgs Hurricane is 8Kgs.
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.

Last edited by Samurai : 29th November 2011 at 20:37.
Samurai is offline   Reply With Quote
Old 29th November 2011, 16:01   #180
Team-BHP Support
 
Jaggu's Avatar
 
Join Date: May 2004
Location: Bangalore
Posts: 17,498
Thanked: 6,782 Times
Default Re: Avalakonda OTR 2011 : A Late report

Quote:
Originally Posted by Samurai View Post
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.
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.

Quote:
Originally Posted by Samurai View Post
Not really, I have climbed with constant throttle in really long inclines in Munnar, Coorg, Beltangady, etc.
How can you say that the other method is NOT more efficient? And wont the revs vary inspite of steady throttle from you, based on the traction offered? So modulation of rpm is anyways happening.

My point is making use of this further, by more modulation from the A pedal, which is a technique one can easily master.

Quote:
Originally Posted by Samurai View Post
Yes, it is neither obvious or visible. So I wonder whether this effect exists.
The CJ3B manual should have some facts researched to mention it right?

Quote:
Originally Posted by Samurai View Post
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.
On the contrary with modulation you would have superb capabilities at low speed crawling, especially on rocky terrain.

Quote:
Originally Posted by Samurai View Post
In Jeeps with lighter ratios or lighter flywheel, pumping/modulating might be necessary.
It will help more, true.

Last edited by Jaggu : 29th November 2011 at 16:02.
Jaggu is offline   Reply With Quote
Reply


Thread Tools Search this Thread
Search this Thread:

Advanced Search


Similar Threads
Thread Thread Starter Forum Replies Last Post
OTR & Paragliding: Palakkad Off-Road Adventure's "Off-Road Extreme 2013" JeepCaptain 4x4 Excursions 7 2nd March 2013 12:45
Drift Techniques !! varun_patra Indian Motorsport 8 7th April 2010 14:50
Any new techniques for the old gashes Speedme Technical Stuff 3 12th January 2007 19:52
Launch techniques v1p3r Technical Stuff 29 9th July 2005 22:11
rally driving techniques manticore Indian Motorsport 29 26th May 2004 17:45


All times are GMT +5.5. The time now is 16:22.

Copyright ©2000 - 2017, Team-BHP.com
Proudly powered by E2E Networks