Applying Handbreak - Press Release button or Not

Joe_Horner

Samsonite1 wrote: »

Ok, yes not directly to the cable but the button prevents the ratchet adding to the resistance. Pulling with or without the button is not the same at all, full stop. There is more resistance using the ratchet, so you are less likely to pull it as hard - it does not pull as quickly.

By stretching - I know what the cable looks like, I have fixed them myself. I mean (to take my string, tooth removal analogy) the length of slack. Because the mechanism has an adjustable nut for the cable, that is what pulling too hard affects. I have done this myself as have many people I know on many cars. Try it for yourself - feel free to argue all you like my friend.

Sooo may misconceptions in one post!

(1) The resistance added by the ratchet pawl sliding over the segment is effectively zero - a few 10s of grams of force in a cable designed to take over a quarter of a million grams of force.

(2) On the vast majority of cars there should be no slack in the handbrake cable when adjusted correctly. You're confusing slack in the cable with free movement at the brakes themselves - there will be a certain amount of movement at the brakes before the shoes / pads contact the disks / drums but the cable itself should be tight enough that the operating lever at the brake end starts moving as soon as you start moving the lever - ie: no slack in the cable.

(3) If you really believe that you can affect a cable adjuster - usually around a 6mm threaded rod with a yield strength (ie: when it starts to stretch) of over 450 kg (from basic engineering tables for the weakest grade of threaded rod) by pulling on a handbrake lever then you're either over estimating your own strength or will be ripping the lever out of the floor.

(4) It's not me who's "arguing with you", it's basic physics and engineering.




eta: I see the problem - you're not actually reading. All the points in your "internet research" post above have already been covered and agreed by me with the exception of the matter of resistance from the pawl, which I cover above and is effectively zero in the context of the engineering margins concerned.

Samsonite1

So why have I on numerous occasions had to tighten the cable on cars? It may not be directly to do with the single components I have mentioned but it happens and that is real. I think you are simplifying how the entire system works and you are not taking into account the stress on the cable from the car. Cars are quite heavy you know.

Also "a quarter of a million grams" is 250KG - weight-lifters can lift more than that if you want to go into numbers.

Again, spouting out bits of stats is not really saying anything and does not explain what is happening to handbrakes. I would love to believe you (although I am not sure what you are trying to say), but I cannot really discount what has happened on my own cars where I have had to take the covers off the hand brake and tighten the cable. One time it was illustrated because the man moving my car at a garage gave the hand brake an almighty yank and when I drove off, there was no hand brake at the next set of traffic lights. I do concede that it would have been possible to do this by not pressing the button most likely, but going back to the other research points I have now put across, the sensory feedback tends to stop you over doing the hand brake.

Samsonite1

Also, some more official information: There is an MOT failure with the following description:

"When the brake is fully applied there is no possibility of further travel of the lever because the lever is at the end of its working travel".

Ironically this is what the garage did to my car after it passed its MOT. The hand break was all the way up, but the brakes were not engaged. Ironic because it would have failed an MOT immediately after passing one.

Also, it is quite common for people to suffer from "snapped" hand brake cables - there are even posts on this forum asking for advice on how much to pay for such an issue. Of course these people cannot be telling the truth because of physics and engineering... (I do understand that it may not be the cable, but another component that caused the "snap").

Joe_Horner

Samsonite1 wrote: »

So why have I on numerous occasions had to tighten the cable on cars? It may not be directly to do with the single components I have mentioned but it happens and that is real.

The normal reason for people tightening handbrake cables is that the auto adjusting mech on the brakes is faulty so that, as the shoes / pads wear, the travel of the handbrake increases because it has to move the shoes further before they do anything.

That's then commonly misdiagnosed as a stretched cable and, instead of sorting out the brakes themselves, people tighten up the cable to "remove the slack".

Samsonite1 wrote: »

I think you are simplifying how the entire system works and you are not taking into account the stress on the cable from the car. Cars are quite heavy you know.

You can't really simplify a (mechanical) handbrake system much - it really is about as simple as engineering gets already.

Two levers and a cable in between. You pull one lever, it supplies mechanical advantage according to its dimensions so that the load in the cable is greater than you could apply yourself. The other end of the able pulls another lever, which also provides mechanical advantage so that the force aplied to the shoes is, perhaps, 50 to 100 times the force you apply with your hand but acting through a few mm of travel instead of the 20 or so cm of travel your hand goes through

Samsonite1 wrote: »

Also "a quarter of a million grams" is 250KG - weight-lifters can lift more than that if you want to go into numbers.

Yes, a power lifter using both arms on a stage can lift that. But that's kind of irrelevant to what the average driver, sitting in a seat, and pulling his arm upwards by his side can do!

Samsonite1 wrote: »

Again, spouting out bits of stats is not really saying anything and does not explain what is happening to handbrakes.

They're not "bits of stats", they're very simple examples of applied mechanics calculations which are the basis of all engineering. Without them bridges would collapse, aeroplanes would fall from the sky, and cars with handbrakes would never have been invented!

Joe_Horner

Samsonite1 wrote: »

Also, some more official information: There is an MOT failure with the following description:

"When the brake is fully applied there is no possibility of further travel of the lever because the lever is at the end of its working travel".

Ironically this is what the garage did to my car after it passed its MOT. The hand break was all the way up, but the brakes were not engaged. Ironic because it would have failed an MOT immediately after passing one.

Also, it is quite common for people to suffer from "snapped" hand brake cables - there are even posts on this forum asking for advice on how much to pay for such an issue. Of course these people cannot be telling the truth because of physics and engineering... (I do understand that it may not be the cable, but another component that caused the "snap").

As above, almost all "no reserve travel" fails come down to poorly adjusted back brakes (assuming a rear handbrake, of course). That doesn't affect the foot brake performance much because it just makes the pedal move down a little further, but it can easily leave you with too much movement on a handbrake lever.

Snapped cables are an entirely different thing. cables snap because (a) they've reached the end of their fatigue life (they're being bent backwards and forwards round bends every time you use them) or, more often, because they've corroded somewhere and bee weakened by rust to the point that they fail. they do NOT just "stretch till they break"!

Samsonite1

Joe_Horner wrote: »

As above, almost all "no reserve travel" fails come down to poorly adjusted back brakes (assuming a rear handbrake, of course). That doesn't affect the foot brake performance much because it just makes the pedal move down a little further, but it can easily leave you with too much movement on a handbrake lever.

Snapped cables are an entirely different thing. cables snap because (a) they've reached the end of their fatigue life (they're being bent backwards and forwards round bends every time you use them) or, more often, because they've corroded somewhere and bee weakened by rust to the point that they fail. they do NOT just "stretch till they break"!

By the way, let me reiterate I am not focusing on a particular cable and I explained stretching was not actually stretching, but more straining the whole assembly - but having seen for myself, via others and you can find it posted all over these forums along with motoring forums - pulling the hand brake excessively does weaken the hand brake assembly. Anyway,

Also by the way, I gave you a thank you for this post as I understand that you are not being personal, but providing information - I feel you are not understanding my points and being transfixed on specific details - that is probably a failure to be clear on my part.

This guy has obviously had similar issues with MOT testers "gorilla-ing" the hand brake:
https://forums.moneysavingexpert.com/discussion/1688623

It always seems to get knackered when the MOT tester gets their hands on it anyway. When parking the car don't use the handbrake excessively, only use it as is enough to secure the car (2 to 3 clicks when properly adjusted), and keep it in first gear when parked. If you pull hard all the way up you just stretch the cable.

I DID cringe at the word "stretch"...

enfield_freddy

struggling to answer , as my car has an alternate thing fitted , its called a handbrake

Samsonite1

enfield_freddy wrote: »

struggling to answer , as my car has an alternate thing fitted , its called a handbrake

You can use the words concatenated or not, but you are referring to break?

Edit: and the manual says parking brake - let's not mention e-brake.

reeac

What a lot of confusion! I don't know how you lot could cope with the concept of the fly off handbrake such as my 1958 MGA sports. With this you engage the ratchet by pressing the button when the brake is fully applied and release it by simply lifting the lever a bit further without touching the button.

Car_54

reeac wrote: »

What a lot of confusion! I don't know how you lot could cope with the concept of the fly off handbrake such as my 1958 MGA sports. With this you engage the ratchet by pressing the button when the brake is fully applied and release it by simply lifting the lever a bit further without touching the button.

I am reminded of Godwin's law: "As an online discussion grows longer, the probability of a comparison involving Nazis or Hitler approaches 1".

There must be a corollary involving motoring forums, and Morris Minors, MGs or Austin 7s.