[SPIKE ARRESTOR]

Originally Posted by '72 Bullet

Does anyone have any idea how to make calculations to calculate the gradeability of the various 4x4s on this forum.

I have mentioned the formula for calculating grade ability in my earlier posts, please have a look,

Spike

[Samurai]

The following is an interesting twist. The front tyres face vertical wall, the rear is on level ground.

YouTube - Humvee Climbing Vertical Wall 2

[adc]

Originally Posted by adc

So with IFS system, listing the benefits with front locker in front with a good rear LSD [already supplied as OEM] at the back:

So with IFS system, listing the benefits with front locker in front with a good rear LSD [already supplied as OEM] at the back:

1. Keeping the front down, pulling action, solving the bad articulation of IFS.


2. Going through crawl motion over up obstacle rather than gunning up through pedal and momentum. As the IFS lands it takes up huge pressure, since the rear is giving all the momentum and traction, and the front wheel [right or left] which comes down first takes a huge impact, big obstacle, big jump something will break or at least will soon have to run to change tie rods and all.


3. Over a front LSD, a selectable locker will be proreactive, ie, before the situation develops where a front wheel is going on top.


But all said and done, with improving technologies a good auto locker is what is most required for a front differential of IFS system as a selectable locker [though the best] will require very good judgment all the time.

A front LSD will still act as a locker for quite sometime even in turning and steering should remain difficult, at least at the beginning of the turn?

This all theoretical for me, and definitely surely somewhere the argument of mine is not okay!. Please do give your views.

Originally Posted by ex670c

Hi ADC,

I think you need to go for a few OTRs.
Open Invitation from the Chennai JEEPers.

Please Do ONLY the Following

If You have ONE Locker & ONE LSD - LSD Front & Locker Rear.
Front with FWHubs.

If You have ONE Diff-Lock & ONE LSD - LSD Front & Diff-Lock Rear.
Front with FWHubs.

Arka

Thanks again, sure thats a good invitation, let me get a 4wd even first and as long as my active driving years there [max another 8-10 yrs], let me be the tourer for now.

But would have loved a patient explanation than head banging.

Why are you differentiating between locker and diff lock and taking selectable lockers as diff lock? Is there other rule about naming them?

Again for IFS system why not a front locker [auto or selectable] and rear LSD [already came as OEM] for those two options? For Safari even with weight, felt the front coming up and the weight with which it comes down again.

Will not a LSD [since it is aftermarket and good] at the front act as an auto locker which does not disengage quickly, in turns at least at the beginning?

But then, as said, I am all theoretical and that too not even a 4wd. But then mind over matter, lets leave it here!

[khan_sultan]

Originally Posted by ex670c

Hi ADC,

I think you need to go for a few OTRs.

Yes, that's the best learning ground for all things theory & practical. You see so you get to understand a lot better

....
Please Do ONLY the Following
....

If You have ONE Diff-Lock & ONE Locker - Locker Front & Diff-Lock Rear.
Front with FWHubs.
....

Any reason for this particular combo?

I would think that selectable diff-lock in front would be better than a locker up front. With FWH & 4x4 engaged, lockers would have steering complications at all times but that would not be the case with selectable diff-lock on front.

[ex670c]

Originally Posted by adc

Why are you differentiating between locker and diff lock and taking selectable lockers as diff lock? Is there other rule about naming them?

Again for IFS system why not a front locker [auto or selectable] and rear LSD [already came as OEM] for those two options? For Safari even with weight, felt the front coming up and the weight with which it comes down again.

Will not a LSD [since it is aftermarket and good] at the front act as an auto locker which does not disengage quickly, in turns at least at the beginning?

But then, as said, I am all theoretical and that too not even a 4wd. But then mind over matter, lets leave it here!

A Selectable Diff-Lock has 2 modes Locked and un-Locked which are user dependent for input irrespective of vehicle orientation (Straight line or Turning).

The Auto-Locker/Locker (Dog Clutch LSD) has 2 Modes which depend on Torque and Centrifugal Forces inside the Differential Carrier Assembly.
i.e Locked in Straight Lines and Unlocked/Free Wheel in Turns.

The LSD in 4WD is Torque Sensitive and works on Friction Wet-Clutch (Plate or Conical). It unlocks when the Torque bias is more than what the LSD is setup for.

Even in a straight Line the LSD will unlock if one wheel is on more slippery surface or if one wheel catches air.

Front Axle = Steering Axle.

In all 4x4 the Front Live Axle is the Weaker Axle as it is not expected to do more the 30% of the work.

In most cases the manufacturer uses a Smaller Differential in the Front Axle.
TATA uses Dana 35 on Front Axle and DANA 44 on Rear Axle.
JEEP uses Dana 35 on Front Axle and Dana 44 on Rear Axle.
M&M uses Dana 44 on Front Axle and Dana 44 on Rear Axle.

Even if the Differential is the Same the front is weaker Due to
i) Steering Components i.e Steering Knuckle
ii) UJ & CV Joints
iii) IFS

The Dana 44 SFRA is rated at 1600kgs.
Dana 44 FFRA is rated at 1800/2000kgs.
Dana 44 OKBJ is rated at 1400kgs.
Dana 44 IFS is rated at 1100Kgs.

When we engage 4WD the Torque from the T-Case is split 50:50; Front:Rear

If the Rear Diff is Locked then there is a further split 50:50; Left:Right for (Locker & Diff-Locks)

If the Front Diff is Locked then there is a further split 50:50; Left:Right for (Locker & Diff-Locks)

If the Rear Diff has an LSD there is a further split 50:50; Left:Right which depends on Torque and Terrain Conditions So it is as good as an Open Diff, with Benefits.

If the Front Diff is Locked then with an LSD in the Rear the Front Diff will provide more traction and end up doing more work, which it shouldn't, including steering and then you can guess where what will happen especially with an IFS and the additional UJ & CV Joint.

Regards,

Arka

Limited slip differential - Wikipedia, the free encyclopedia

Locking differential - Wikipedia, the free encyclopedia

[ex670c]

Originally Posted by khan_sultan

Any reason for this particular combo?

I would think that selectable diff-lock in front would be better than a locker up front. With FWH & 4x4 engaged, lockers would have steering complications at all times but that would not be the case with selectable diff-lock on front.

Hi Shahnawaz,

That is to Exploit the Diff-Locks to their ultimate potential.

i.e 90% of the usage is UNLOCKED for Road Use.

Regards,

Arka

[khan_sultan]

Originally Posted by ex670c

Hi Shahnawaz,

That is to Exploit the Diff-Locks to their ultimate potential.

i.e 90% of the usage is UNLOCKED for Road Use.

Regards,

Arka

He he. nice one.. And I thought we were adding locking capabilities to aid us in off-road situations

[ex670c]

Originally Posted by Samurai

The following is an interesting twist. The front tyres face vertical wall, the rear is on level ground.

YouTube - Humvee Climbing Vertical Wall 2

Hi Sharath,

What is the Twist, the Rear Axle is pushing the Vehicle Froward, the Approach Angle allows the Front Wheels to make contact with the 90Degree Wall.

If the Front Axle is Driven and in Low Ratio, the driver will have better control.

But it is a considerable achievement to get such ADR Angles.

We guys can try an experiment.

1 Jeep & 1 Slope (A Stock FFRA CJ3B )

i) Climb up in 4WD-HI.
ii) Climb up in 4WD-HI Reverse.
ii) Climb up in 2WD-HI.
iii) Climb up in 2WD-HI Reverse.
iv) Climb up in 4WD-HI Front Axle (Rear Axle Disconnected).
v) Climb up in 4WD-HI Front Axle (Rear Axle Disconnected) Reverse.

Lets see which attempt is successful or most efficient.

Spike, Sutripta & Samurai and other Scientific Minds can add to parameters.

Regards,

Arka

PS - Since we have to remove the rear Prop-Shaft, I already have a volunteer in mind

[headers]

Originally Posted by ex670c

I already have a volunteer in mind

May I volunteer Arka Ji, STGH...

[Samurai]

Originally Posted by ex670c

Hi Sharath,

What is the Twist, the Rear Axle is pushing the Vehicle Froward, the Approach Angle allows the Front Wheels to make contact with the 90Degree Wall.

There is a huge twist. None of the usual formulas work here. I'll let spike deal with the complex calculations. It is surely beyond me.

I would say, the rear axle is providing the downforce (or sideforce in this case) to the front tyre against the wall.

Originally Posted by ex670c

If the Front Axle is Driven and in Low Ratio, the driver will have better control.

If the front axle is not driven, it won't even climb. It will only push against the wall. The climbing power is coming primarily coming from the front axle. The rear axle is providing the traction via sideforce/downforce. Once the front tyre starts climbing, the rear alone can push it, very difficult at first, but it will get easier as it goes forward/upwards.

[SPIKE ARRESTOR]

Originally Posted by Samurai

There is a huge twist. None of the usual formulas work here. I'll let spike deal with the complex calculations. It is surely beyond me.
If the front axle is not driven, it won't even climb. It will only push against the wall. The climbing power is coming primarily coming from the front axle. The rear axle is providing the traction via sideforce/downforce. Once the front tyre starts climbing, the rear alone can push it, very difficult at first, but it will get easier as it goes forward/upwards.

Samurai, i agree with you, if the front axle is not driven, it will continue pushing against the wall. There is resistance from the wall to the forward movement of this vehicle, so at the beginning of the climb as the tyres cannot move down the reaction from the ground due to the power causes the wheel to lift slightly, at the same time the rear wheels are pushing the vehicle forward, once the vehicle begins to move the sheer momentum from the rear wheels propels the vehicle forward. This is what i feel.

Spike

[Sankar]

Originally Posted by Samurai

I would say, the rear axle is providing the downforce (or sideforce in this case) to the front tyre against the wall.

If the front axle is not driven, it won't even climb. It will only push against the wall. The climbing power is coming primarily coming from the front axle. The rear axle is providing the traction via sideforce/downforce. Once the front tyre starts climbing, the rear alone can push it, very difficult at first, but it will get easier as it goes forward/upwards.

Agree with samurai. H1 starts climbing at 0:13 secs and till 0:16secs the rear wheel does not move much but the vehicle is already more than half way up the wall. We can see that the climbing is done by the front wheels, vehicle is being pulled. At 0:16secs we can see the rear move forward.

Here is a related video. First he tries in RWD it doesn't climb, then he puts it into 4WD and it climbs. Rear end pushing does not work with a wall.

YouTube - 4X4 Golf Cart - D&D Motor

[SPIKE ARRESTOR]

if you notice, the guy uses the logs/planks kept their so that his front wheels are at a raised level when compared to the rear, this helps in the initial climb.

[Samurai]

Originally Posted by SPIKE ARRESTOR

There is resistance from the wall to the forward movement of this vehicle, so at the beginning of the climb as the tyres cannot move down the reaction from the ground due to the power causes the wheel to lift slightly, at the same time the rear wheels are pushing the vehicle forward, once the vehicle begins to move the sheer momentum from the rear wheels propels the vehicle forward.

Spike, you are the numbers guy. Can you calculate the amount of the force needed to make the front tyre move up by the push of rear axle only?

Just guessing here, I am not good at the mathematics and formulas involved here. Won't overcoming the traction of rear tyres (on ground) easier than lifting the front by lateral force only? Which is the easier path?

[SPIKE ARRESTOR]

Originally Posted by Samurai

Spike, you are the numbers guy. Can you calculate the amount of the force needed to make the front tyre move up by the push of rear axle only?
Won't overcoming the traction of rear tyres (on ground) easier than lifting the front by lateral force only? Which is the easier path?

Samurai, as you said overcoming the traction of rear tyres is the "easier path" but here it is a cumulative effect of front and rear wheels, if either one doesn't work i don't think it would have moved the way it did, i will try and come out with the formula, give me some time.

Spike