Poor mans locker, using the break.
Thread Starter
Senior Member
Joined: Jul 2010
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From: Long Island NY
Year: 2000
Model: Cherokee
I've got an idea; jack a rear tire off the ground in 2hi (open diff). Rev engine, observe no movement. Have friend rev engine while you grab spinning tire. Observe torque. Just because you can't see it, doesn't mean its not there. The fact that the tire is spinning is evidence to the fact that there is torque, because what is torque? Rotational force!
Regardless of who is correct in this situation, the method you are choosing to use will cause damage to your vehicle. It may get you unstuck, it may not.
I was never very good at math anyways, I just know its better to have 2 wheels on the ground instead of one.
Cheers
Regardless of who is correct in this situation, the method you are choosing to use will cause damage to your vehicle. It may get you unstuck, it may not.
I was never very good at math anyways, I just know its better to have 2 wheels on the ground instead of one.
Cheers
Read the above, I dont plan to do this.
I worked for them when they had the cross-axis diff, not the piece of crap parrallel axis they ended up adopting through one of their sales to other companies. The original had a 9 to 1 TBR. It was reduced down to about 5 to 1 in the Humvee application.
As for diffs, wasn't this thread started by a guy asking about applying the BRAKES to add traction? That's differential action to me.
As for diffs, wasn't this thread started by a guy asking about applying the BRAKES to add traction? That's differential action to me.
Thread Starter
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Joined: Jul 2010
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From: Long Island NY
Year: 2000
Model: Cherokee
This is a quote from a reply that I got from Quaife engineering.
http://www.taylor-race.com/pdf/under...ferentials.pdf
"The limitation of the open differential is that the thrust available is limited to the
maximum thrust (acceleration grip) of the wheel with the poorest grip. Again,
with a 50-50 split of torque, both tires have exactly the same thrust, limited by the
tire with weaker grip."
http://www.taylor-race.com/pdf/under...ferentials.pdf
"The limitation of the open differential is that the thrust available is limited to the
maximum thrust (acceleration grip) of the wheel with the poorest grip. Again,
with a 50-50 split of torque, both tires have exactly the same thrust, limited by the
tire with weaker grip."
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Joined: Nov 2011
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From: Manhattan, Kansas
Year: 1997
Model: Cherokee
Engine: 4.0L
This is a quote from a reply that I got from Quaife engineering.
http://www.taylor-race.com/pdf/under...ferentials.pdf
"The limitation of the open differential is that the thrust available is limited to the
maximum thrust (acceleration grip) of the wheel with the poorest grip. Again,
with a 50-50 split of torque, both tires have exactly the same thrust, limited by the
tire with weaker grip."
http://www.taylor-race.com/pdf/under...ferentials.pdf
"The limitation of the open differential is that the thrust available is limited to the
maximum thrust (acceleration grip) of the wheel with the poorest grip. Again,
with a 50-50 split of torque, both tires have exactly the same thrust, limited by the
tire with weaker grip."
It's saying that IT DOES NOT MATTER IF YOU USE THE BRAKES the tire with the poorest grip will STILL be the one to spin
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From: San Jose
Year: 89
Model: Cherokee
Engine: 4.0 I6
Guess you didnt read the last paragraph on my first post. I was using the braking idea bring up the idea of available torque and to relate to having a locker. I bought a locker Im installing soon. What I am wondering is if the torque is increased due to braking or a locker how does it affect the other axle. And if the the torque is increased equally to the other axle how much more of a benefit is dual lockers.
Jerry I didnt say there is no torque. Im saying the torque, the weight of the wheel and fraction in the bearing create a small amount of torque. What Im saying is there is only as much torque as there is a demand for. When you grab the spinning wheel you are demanding more torque and will get it, grab with enough force, in theory unless your superman and the other wheel will spin.
Read the above, I dont plan to do this.
I dont know what a Cross-axis diff is. But dont all limited slip differential without added into the design not work when a wheel is in the air? Because there is no torque to the wheel?
Your reply regarding a demand for torque, completely seperate from your original question and another conversation entirely.
If I'm climbing a hill in san francisco there is a demand for torque. If my engine can't put out enough torque to overcome the friction of the wheels, I won't move. My engine is still putting out torque, just not enough. If I lift one wheel of the ground, the torque to that axle goes to that wheel because there is no longer a friction force holding it back. There is still "a demand" for torque, my engine is still spinning and saying "send power to the wheels dammit!" The torque Its still there its just being wasted.
The weight of the wheel and the friction in the bearing don't make torque, they require torque to be overcome and create movement. That free wheel will spin until the amount of force acting against its torque is greater than the force holding the other wheel.
Torque is required to rotate an object. If I apply 177 ft/lbs of torque to a wheel, its going to spin unless there's a force acting on it that is greater than the torque in the opposite direction. I'm still applying torque to it, its just not spinning. If I lift that wheel in the air its going to spin with 177 ft/lbs of torque because there is little to no friction acting on it. I grab it and suddenly I'm holding on to 177 ft/lbs of force. If I'm strong enough I can provide the friction needed to cancel out the torque.
Thread Starter
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From: Long Island NY
Year: 2000
Model: Cherokee
To answer your question, no. Having a locker in the back won't apply more torque to a wheel on the other axle. All a locker does is supply the torque given by the driveshaft to both wheels on that axle at all times evenly. It doesn't change the amount of torque the other axle recieves.
Your reply regarding a demand for torque, completely seperate from your original question and another conversation entirely.
If I'm climbing a hill in san francisco there is a demand for torque. If my engine can't put out enough torque to overcome the friction of the wheels, I won't move. My engine is still putting out torque, just not enough. If I lift one wheel of the ground, the torque to that axle goes to that wheel because there is no longer a friction force holding it back. There is still "a demand" for torque, my engine is still spinning and saying "send power to the wheels dammit!" The torque Its still there its just being wasted.
The weight of the wheel and the friction in the bearing don't make torque, they require torque to be overcome and create movement. That free wheel will spin until the amount of force acting against its torque is greater than the force holding the other wheel.
Read the quote I posted. Torque is limited by that amount of trust needed to over come traction. No traction means no torque.
Torque is required to rotate an object. If I apply 177 ft/lbs of torque to a wheel, its going to spin unless there's a force acting on it that is greater than the torque in the opposite direction. I'm still applying torque to it, its just not spinning. If I lift that wheel in the air its going to spin with 177 ft/lbs of torque because there is little to no friction acting on it. I grab it and suddenly I'm holding on to 177 ft/lbs of force. If I'm strong enough I can provide the friction needed to cancel out the torque.
Your reply regarding a demand for torque, completely seperate from your original question and another conversation entirely.
If I'm climbing a hill in san francisco there is a demand for torque. If my engine can't put out enough torque to overcome the friction of the wheels, I won't move. My engine is still putting out torque, just not enough. If I lift one wheel of the ground, the torque to that axle goes to that wheel because there is no longer a friction force holding it back. There is still "a demand" for torque, my engine is still spinning and saying "send power to the wheels dammit!" The torque Its still there its just being wasted.
The weight of the wheel and the friction in the bearing don't make torque, they require torque to be overcome and create movement. That free wheel will spin until the amount of force acting against its torque is greater than the force holding the other wheel.
Read the quote I posted. Torque is limited by that amount of trust needed to over come traction. No traction means no torque.
Torque is required to rotate an object. If I apply 177 ft/lbs of torque to a wheel, its going to spin unless there's a force acting on it that is greater than the torque in the opposite direction. I'm still applying torque to it, its just not spinning. If I lift that wheel in the air its going to spin with 177 ft/lbs of torque because there is little to no friction acting on it. I grab it and suddenly I'm holding on to 177 ft/lbs of force. If I'm strong enough I can provide the friction needed to cancel out the torque.
Your right that if you input 177ftlbs you get 177 out. HOWEVER an engine only produce enough torque to over come the smallest load exerted on it. So one wheel on ice require 10ftlb the wheel on dirt require 100ftlbs. The engine is only goin to make 10 ftlb, the wheel on ice will spin because the force and friction are equal. The tire in the dirt wont spin because its on getting 10 ftlbs and needs 90 more. Adding friction to the spinning will require more torque, if you use enough brake to get 100ftlb on force on the spinning wheel the stuck wheel will no spin cuz its friction and thrust force are now equal.
Last edited by No4x4Yet; Mar 15, 2013 at 10:39 AM.
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From: schenectady, NY
Year: 1999
Model: Cherokee
Engine: 4.0
Your miss reading the quote. The quote says the amount of torque the engine can produce is limited by the amout of opposing force from the wheel with the least traction. It says nothing about brakes. However using the brake adds friction to the spinning wheel and increases the trust or torque required to sping the wheel, so more torque is sent to both wheels. Add enough friction with the brakes to to create enoguh thrust and overcome the friction force and you move again.
Read the quote I posted. Torque is limited by that amount of trust needed to over come traction. No traction means no torque.
Your right that if you input 177ftlbs you get 177 out. HOWEVER an engine only produce enough torque to over come the smallest load exerted on it. So one wheel on ice require 10ftlb the wheel on dirt require 100ftlbs. The engine is only goin to make 10 ftlb, the wheel on ice will spin because the force and friction are equal. The tire in the dirt wont spin because its on getting 10 ftlbs and needs 90 more. Adding friction to the spinning will require more torque, if you use enough brake to get 100ftlb on force on the spinning wheel the stuck wheel will no spin cuz its friction and thrust force are now equal.
Read the quote I posted. Torque is limited by that amount of trust needed to over come traction. No traction means no torque.
Your right that if you input 177ftlbs you get 177 out. HOWEVER an engine only produce enough torque to over come the smallest load exerted on it. So one wheel on ice require 10ftlb the wheel on dirt require 100ftlbs. The engine is only goin to make 10 ftlb, the wheel on ice will spin because the force and friction are equal. The tire in the dirt wont spin because its on getting 10 ftlbs and needs 90 more. Adding friction to the spinning will require more torque, if you use enough brake to get 100ftlb on force on the spinning wheel the stuck wheel will no spin cuz its friction and thrust force are now equal.
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From: San Jose
Year: 89
Model: Cherokee
Engine: 4.0 I6
Your miss reading the quote. The quote says the amount of torque the engine can produce is limited by tire with the poorest grip (least friction). It says nothing about brakes. However using the brake adds friction (an automtive engineering student should know this) to the spinning wheel and increases the trust or torque required to spin the wheel, so more torque is sent to both wheels. Add enough friction with the brakes to create enough thrust and overcome the friction force and you move again.
Read the quote I posted. Torque is limited by that amount of trust needed to over come traction. No traction means no torque.
Your right that if you input 177ftlbs you get 177 out. HOWEVER an engine only produce enough torque to over come the smallest load exerted on it. So one wheel on ice require 10ftlb the wheel on dirt require 100ftlbs. The engine is only goin to make 10 ftlb, the wheel on ice will spin because the force and friction are equal. The tire in the dirt wont spin because its on getting 10 ftlbs and needs 90 more. Adding friction to the spinning will require more torque, if you use enough brake to get 100ftlb on force on the spinning wheel the stuck wheel will no spin cuz its friction and thrust force are now equal.
According to you a lawnmower only puts out enough torque to spin the blade? What happens when you hit a large rock? Torque keeps moving and bad things happen. There's a difference between what happens in the world and what happens on paper. Stop looking at numbers and formulas and start looking at mechanisms. You'll learn a lot more about how things function rather than why they function. I took a friend from a physics class to one of those indoor skydiving things. He kept trying to analyze the **** of it. You know what I did? I enjoyed it because I was flying, he was freaking out about the 200 mile an hour wind being strong enough to hold his fat *** up. Thanks for the intellectual conversation by the way, I've been dying for some real mechanical talk.
CF Veteran
Joined: Aug 2011
Posts: 1,994
Likes: 8
From: San Jose
Year: 89
Model: Cherokee
Engine: 4.0 I6
This is a quote from a reply that I got from Quaife engineering.
http://www.taylor-race.com/pdf/under...ferentials.pdf
"The limitation of the open differential is that the thrust available is limited to the
maximum thrust (acceleration grip) of the wheel with the poorest grip. Again,
with a 50-50 split of torque, both tires have exactly the same thrust, limited by the
tire with weaker grip."
http://www.taylor-race.com/pdf/under...ferentials.pdf
"The limitation of the open differential is that the thrust available is limited to the
maximum thrust (acceleration grip) of the wheel with the poorest grip. Again,
with a 50-50 split of torque, both tires have exactly the same thrust, limited by the
tire with weaker grip."
limitation of open differential= natural flaw
limited= maxed out,
thrust available= torque output of the engine
maximum thrust=acceleration grip of tire with poorest grip
in a normal sentence that would read that the natural flaw of an open differential, is that the torque given, goes to the tire with the poorest grip. which is exacly what everyone has been saying here and were all on the same page.
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Joined: Jan 2013
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From: Denver
Year: 1998
Model: Cherokee
Engine: 4.0
Think about it in terms of an electrical analogy. The left tire, on ice, is like a short circuit. The right tire, on the dirt, has some resistance in the circuit. The electricity will follow the easiest path, and all the current will go through the short. Same thing with an open diff.
Now you apply the brakes, which effectively adds the same resistance to both circuits. Some of the current will now flow to the right tire, although more will still go to the left because the resistance is lower. The left tire will still spin, but the current to the right has gone from zero to something, and it will start trying to turn.
As you add more resistance (brakes) to both sides, the difference between left and right will decrease. A greater percentage of the current will begin flowing to the right. Maybe you have gone from a 100/0 split to 60/40. Then you can add more current (gas pedal) and hopefully you will send enough current to the right tire to get it rolling. A greater portion of the current would still be going to the left tire and making it spin, but the current to the right tire has gone up from zero to something.
The problem is that you have a circuit breaker in the system (your spider gears, etc.) prior to the split. Apply too much resistance and current, and you will blow the breaker before you ever get enough current through the right tire.
Now you apply the brakes, which effectively adds the same resistance to both circuits. Some of the current will now flow to the right tire, although more will still go to the left because the resistance is lower. The left tire will still spin, but the current to the right has gone from zero to something, and it will start trying to turn.
As you add more resistance (brakes) to both sides, the difference between left and right will decrease. A greater percentage of the current will begin flowing to the right. Maybe you have gone from a 100/0 split to 60/40. Then you can add more current (gas pedal) and hopefully you will send enough current to the right tire to get it rolling. A greater portion of the current would still be going to the left tire and making it spin, but the current to the right tire has gone up from zero to something.
The problem is that you have a circuit breaker in the system (your spider gears, etc.) prior to the split. Apply too much resistance and current, and you will blow the breaker before you ever get enough current through the right tire.
Thread Starter
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Joined: Jul 2010
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From: Long Island NY
Year: 2000
Model: Cherokee
Unless you brake ONLY that one wheel thats on ice it will have no gain. The power will be distrubited to the wheel with the least amount of traction. Thats it. If you brake with an open diff and think that its as good as a locker you have never driven with a locker. Get a locker and offroad and see how different it is.
Even if you gave it 100 lbs of torque it wouldn't go anywhere, that ice tire still has no traction. And that's where the power is going to go because that is the flaw in an open differential. The whole purpose of using the brake is to make that tire stop spinning so that the power can go to where its needed.
Read above and below on this.
According to you a lawnmower only puts out enough torque to spin the blade? What happens when you hit a large rock? Torque keeps moving and bad things happen. There's a difference between what happens in the world and what happens on paper. Stop looking at numbers and formulas and start looking at mechanisms. You'll learn a lot more about how things function rather than why they function. I took a friend from a physics class to one of those indoor skydiving things. He kept trying to analyze the **** of it. You know what I did? I enjoyed it because I was flying, he was freaking out about the 200 mile an hour wind being strong enough to hold his fat *** up. Thanks for the intellectual conversation by the way, I've been dying for some real mechanical talk.
Read above and below on this.
According to you a lawnmower only puts out enough torque to spin the blade? What happens when you hit a large rock? Torque keeps moving and bad things happen. There's a difference between what happens in the world and what happens on paper. Stop looking at numbers and formulas and start looking at mechanisms. You'll learn a lot more about how things function rather than why they function. I took a friend from a physics class to one of those indoor skydiving things. He kept trying to analyze the **** of it. You know what I did? I enjoyed it because I was flying, he was freaking out about the 200 mile an hour wind being strong enough to hold his fat *** up. Thanks for the intellectual conversation by the way, I've been dying for some real mechanical talk.
Actually I think you misread the quote. Lets break it down.
limitation of open differential= natural flaw
limited= maxed out,
thrust available= torque output of the engine
maximum thrust=acceleration grip of tire with poorest grip
in a normal sentence that would read that the natural flaw of an open differential, is that the torque given, goes to the tire with the poorest grip. which is exacly what everyone has been saying here and were all on the same page.
limitation of open differential= natural flaw
limited= maxed out,
thrust available= torque output of the engine
maximum thrust=acceleration grip of tire with poorest grip
in a normal sentence that would read that the natural flaw of an open differential, is that the torque given, goes to the tire with the poorest grip. which is exacly what everyone has been saying here and were all on the same page.
I using your words minus limited.
The natural flaw is that the torque output of the engine is limited to the
acceleration grip of tire with poorest grip. Again, with a 50-50 split of torque, both tires have exactly the same thrust, limited by the
tire with weaker grip."
Last edited by No4x4Yet; Mar 15, 2013 at 12:23 PM.
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From: Long Island NY
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The dyno is loaded to give resistance to the wheels to simulate it driving down the road. This is why you may have heard of dyno operators "playing" with the dyno to change the numbers. Also why Dynojets and mustang style dynos read differently. They apply the loads differently.
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From: San Jose
Year: 89
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How bout a vertical mill or a lathe? The thing I cant understand is this whole idea of demand that you have, I can understand an engine or motor under load. but like with the mower, torque isn't instantaneously created the moment the blade hits the rock, it's always there. I already answered your question, anything beyond is just a pointless argument. If it is rotating, then there is torque. not just enough to overcome the weight of the pieces involved, but more than that. some greater unspecified amount. if you were to suddenly apply friction, with your brakes your hand or little bunny foo foo you will observe that amount. It's this sudden shock that causes the damage not the sudden appearance of torque, the sudden appearance of load that was not there before. Its like gravity, it isn't the fall that kills you, its the sudden stop.
