BKs New Car

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watkins
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Re: BKs New Car

Post by watkins » Tue Oct 01, 2019 8:38 am

zajn wrote:
Mon Sep 30, 2019 6:16 pm
watkins wrote:
Mon Sep 16, 2019 3:28 pm
That is by no means a heavy clutch. If anything its a bit too light. It is responsive at least.
What exactly makes a clutch heavy vs. light? Is it as simple as the weight of the clutch disc? Or is it how hard the pedal is to push to the floor and keep there?
Generally when referencing a clutch, "light" or "heavy" does refer to pedal effort and isn't really something that has an actual unit of measurement applied, though it very well could.

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Re: BKs New Car

Post by Rope-Pusher » Tue Oct 01, 2019 8:40 am

zajn wrote:
Mon Sep 30, 2019 6:16 pm
watkins wrote:
Mon Sep 16, 2019 3:28 pm
That is by no means a heavy clutch. If anything its a bit too light. It is responsive at least.
What exactly makes a clutch heavy vs. light? Is it as simple as the weight of the clutch disc? Or is it how hard the pedal is to push to the floor and keep there?

The clutch is my Mazda 3 seems very light to me, because it takes very little effort to push to the floor. I've never experienced a different clutch though, except my dad's Dodge Dakota about 15 years ago and I have no memory of what that felt like.
Most people use the terms "light" and "Heavy" to describe the force required to actuate the clutch release pedal.

The actual weight / mass / rotational inertia of the clutch disk can affect the time / force required to shift into a given gear, but the force at the clutch pedal to disengage the clutch is more related to the clamping force of the clutch cover, the efficiency of the clutch release system, and the arc length of the clutch pedal. As a rule of thumb, engines that have higher peak torque output will require higher clutch clamping force. If so, then the force required at the pedal will also be higher, unless the pedal lever is lengthened or the pedal lever swings through more degrees of rotation.

....and then you have something like the Jeep Wrangler, where they add a second clutch disk in order to increase the torque capacity without requiring a "heavy" clutch pedal effort.
'08 Jeep Liberty 6-Speed MT - "Last of the Mohicans"

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potownrob
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Re: BKs New Car

Post by potownrob » Wed Oct 02, 2019 7:20 am

Rope-Pusher wrote:
Tue Oct 01, 2019 8:40 am
zajn wrote:
Mon Sep 30, 2019 6:16 pm
watkins wrote:
Mon Sep 16, 2019 3:28 pm
That is by no means a heavy clutch. If anything its a bit too light. It is responsive at least.
What exactly makes a clutch heavy vs. light? Is it as simple as the weight of the clutch disc? Or is it how hard the pedal is to push to the floor and keep there?

The clutch is my Mazda 3 seems very light to me, because it takes very little effort to push to the floor. I've never experienced a different clutch though, except my dad's Dodge Dakota about 15 years ago and I have no memory of what that felt like.
Most people use the terms "light" and "Heavy" to describe the force required to actuate the clutch release pedal.

The actual weight / mass / rotational inertia of the clutch disk can affect the time / force required to shift into a given gear, but the force at the clutch pedal to disengage the clutch is more related to the clamping force of the clutch cover, the efficiency of the clutch release system, and the arc length of the clutch pedal. As a rule of thumb, engines that have higher peak torque output will require higher clutch clamping force. If so, then the force required at the pedal will also be higher, unless the pedal lever is lengthened or the pedal lever swings through more degrees of rotation.

....and then you have something like the Jeep Wrangler, where they add a second clutch disk in order to increase the torque capacity without requiring a "heavy" clutch pedal effort.
fascinating
ClutchFork wrote:...So I started carrying a stick of firewood with me and that became my parking brake.

Rope-Pusher
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Re: BKs New Car

Post by Rope-Pusher » Wed Oct 02, 2019 8:08 am

potownrob wrote:
Wed Oct 02, 2019 7:20 am
Rope-Pusher wrote:
Tue Oct 01, 2019 8:40 am
zajn wrote:
Mon Sep 30, 2019 6:16 pm


What exactly makes a clutch heavy vs. light? Is it as simple as the weight of the clutch disc? Or is it how hard the pedal is to push to the floor and keep there?

The clutch is my Mazda 3 seems very light to me, because it takes very little effort to push to the floor. I've never experienced a different clutch though, except my dad's Dodge Dakota about 15 years ago and I have no memory of what that felt like.
Most people use the terms "light" and "Heavy" to describe the force required to actuate the clutch release pedal.

The actual weight / mass / rotational inertia of the clutch disk can affect the time / force required to shift into a given gear, but the force at the clutch pedal to disengage the clutch is more related to the clamping force of the clutch cover, the efficiency of the clutch release system, and the arc length of the clutch pedal. As a rule of thumb, engines that have higher peak torque output will require higher clutch clamping force. If so, then the force required at the pedal will also be higher, unless the pedal lever is lengthened or the pedal lever swings through more degrees of rotation.

....and then you have something like the Jeep Wrangler, where they add a second clutch disk in order to increase the torque capacity without requiring a "heavy" clutch pedal effort.
fascinating
Image
Yes Mr. Spock, but only to a select crowd of people. The others are just wishing their vehicle would drive itself and rid them of the burden of shifting from Park to Drive, checking for traffic in the next lane, looking up from their cell phone screens, etc..
'08 Jeep Liberty 6-Speed MT - "Last of the Mohicans"

zajn
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Re: BKs New Car

Post by zajn » Wed Oct 02, 2019 3:49 pm

Rope-Pusher wrote:
Tue Oct 01, 2019 8:40 am
Most people use the terms "light" and "Heavy" to describe the force required to actuate the clutch release pedal.
Ok, that's what I thought! Thanks for the explanation.
Rope-Pusher wrote:
Tue Oct 01, 2019 8:40 am
....and then you have something like the Jeep Wrangler, where they add a second clutch disk in order to increase the torque capacity without requiring a "heavy" clutch pedal effort.
This is crazy! How does that work? This might be a silly question, but where would the second disk be located? Is it just stacked on top of the first one? Couldn't they just make the first disk thicker to achieve the same purpose?
Rope-Pusher wrote:
Wed Oct 02, 2019 8:08 am
Yes Mr. Spock, but only to a select crowd of people. The others are just wishing their vehicle would drive itself and rid them of the burden of shifting from Park to Drive, checking for traffic in the next lane, looking up from their cell phone screens, etc..
Sadly I think I'm getting to that point. I love learning about cars (and how best to drive them), and am happy for the short experience I've had with a manual, but damn does it make me anxious.

Rope-Pusher
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Re: BKs New Car

Post by Rope-Pusher » Thu Oct 03, 2019 8:24 am

zajn wrote:
Wed Oct 02, 2019 3:49 pm
Rope-Pusher wrote:
Tue Oct 01, 2019 8:40 am
Most people use the terms "light" and "Heavy" to describe the force required to actuate the clutch release pedal.
Ok, that's what I thought! Thanks for the explanation.
Rope-Pusher wrote:
Tue Oct 01, 2019 8:40 am
....and then you have something like the Jeep Wrangler, where they add a second clutch disk in order to increase the torque capacity without requiring a "heavy" clutch pedal effort.
This is crazy! How does that work? This might be a silly question, but where would the second disk be located? Is it just stacked on top of the first one? Couldn't they just make the first disk thicker to achieve the same purpose?
Rope-Pusher wrote:
Wed Oct 02, 2019 8:08 am
Yes Mr. Spock, but only to a select crowd of people. The others are just wishing their vehicle would drive itself and rid them of the burden of shifting from Park to Drive, checking for traffic in the next lane, looking up from their cell phone screens, etc..
Sadly I think I'm getting to that point. I love learning about cars (and how best to drive them), and am happy for the short experience I've had with a manual, but damn does it make me anxious.
The automotive clutch disk, as we know it today, has friction material on both faces. This is an improvement from earlier clutch designs, like cone clutches, because it doubles the available surface area, doubling the friction for a given amount of clamping force. Consider an Oreo cookie. The cookie wafers are like the flywheel and pressure plate. As you squeeze the wafers together, they press on the creme filling from both sides. The clutch cover has a spring, or springs that press the pressure plate toward the flywheel, leaving the clutch disk stuck between a rock and a hard place. the clutch cover, including the spring(s) and pressure plate is bolted around the edges of the flywheel, so they spin together whenever the engine crankshaft is revolving. The clutch disk has a hub that is splined to the transmission input shaft. It can slide a bit along the shaft, but the shaft and the clutch disk must spin at the same speed. When you depress the clutch pedal, you are spreading the distance between the pressure plate and the flywheel, so the clutch disk is no longer clamped between them and can spin independently. When you lift your foot off the clutch pedal, the spring(s) in the clutch cover again presses the pressure plate toward the flywheel, clamping the clutch disk between them and eventually, the clutch disk and the transmission input shaft will be forced to spin at the same rate as the crankshaft of the engine.

A dual-disk clutch has a second pressure plate in the clutch cover and a second clutch disk, located between the two pressure plates and also splined to the transmission input shaft. The clutch cover spring presses this multi-layer stack up against the flywheel and the friction surfaces on both faces of both clutch disks transmit the engine torque to the transmission input shaft. Using two clutch disks can double the available friction, but it does take up more space along the axis of the crankshaft and transmission input shaft. If the transmission bellhousing cannot be made "deep" enough to provide this extra space, then maybe the clutch cover spring needs to be stiffer, or the diameter of the flywheel, clutch disk, clutch cover, and bellhousing can be increased to provide more surface area (there is an advantage to increasing the diameter of the clutch disk beyond just that of the increased surface area....like having a longer handle on a socket wrench applies more torque to the fastener for a given force applied to the handle).

Many times, there is no room available for a second clutch disk and pressure plate, and no room for a larger diameter flywheel, etc., and increasing the clamping force of the spring in the clutch cover is the only option. Then, you either accept the pedal force will be higher, or find a way to lengthen the arc length of the pedal pad. A canna change the la's a' physics, Zajn.
'08 Jeep Liberty 6-Speed MT - "Last of the Mohicans"

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