Weird automotive engineering solutions

[homeforsummer]

Let's get back to Automotive oddities, people!!!

Care to offer any?

 

[Tornado]

Care to offer any?

Did you know that Chevrolet once sold a Nova that was actually just a Corolla in drag?

 

[neanderthal]

It's funny how you say that, yet the post of mine you quoted didn't have a single reference or even hint that I was talking "specifically" about Mercedes. All I did was quoted a picture of a Merc that you'd posted, but my post, with complete lack of mention of Mercedes, was talking very generally. So when you say this:

Do I r e a l l y need to quote every single post when I'm making a point? You said it right here.

I have to agree with Leo, I hate the foot pedal parking/e-brakes. I can see how they'd be okay in an automatic once you'd got used to it (but even then you'd still not be able to use it in an emergency situation) but Mercedes are dim enough to use them in their manual cars too. Can you imagine a hill-start in a manual-transmission car with a foot-operated parking brake? What a faff...

And I rebutted a different point, but alluded to your earlier statement above with the pertinent part bolded. I'm pretty sure that suffices for my argument. You. specifically. mentioned. Mercedes. Then you said they suck because of the nightmare of hill starts. I pointed out that its hand released, negating your point.


The scenario is simple;

*rev slightly,
*ease off the clutch until you can feel the driveline tension,
*hold the clutch and accelerator in that position,
*release the handbrake with your hand while keeping your feet in the same position,
*as the car moves off, ease off the clutch and add petrol/ gas/ acceleration as needed.​

Is that really any different than it would be in a car with a handbrake between the seats? If so, at which step?

 

[Jim Prower]

Care to offer any?

I did. Chrysler's Semiauto. That got ignored nicely...

Did you know that Chevrolet once sold a Nova that was actually just a Corolla in drag?

Oh, quit being a pain...

 

[Leonidae]

how about Felix Wankel's creation that works in cars, motorbikes, boats and light aircrafts?

 

[Tornado]

Oh, quit being a pain...

Anyways, I've always been fascinated by the things GM pulled off with the C4 Corvette in the effort to make it the coolest Corvette ever. I especially like how the cooling system worked:
Instead of pulling air through a grill (as there wasn't one), the radiator pulled air from ductwork underneath the car to cool things down. It did the same for the brakes. Its quite hard to explain without pictures, and it is quite hard to find pictures.

 

[Duke]

What surprises me most is that a Moderator has allowed the thread to get this far off topic.

Enough about Brakes, who's right or wrong, dazzling people with your taillights, etc. Let's get back to Automotive oddities, people!!!

It grew out of a discussion of idiosyncratic parking brake designs.

 

[Philly]

For another interesting design thing, I've never been able to confirm it, but I'm under the impression that VW runs a fair amount of rear brake bias in around town driving in the GTI. There is always significantly more brake dust on the rear wheels than the fronts whenever I wash the car, and the rears are always warmer after driving around.

It makes sense that when people are doing easy stops that the car would redirect some of the brake bias to the rear tires in an effort to take a little stress off the poor fronts that already have to do all the going and turning.

 

[Perfect Balance]

I checked this with Milford before I posted - neither of us is a professional mechanic, nor have had the volume of cars pass through our hands that you have, but we have both worked on our vehicles' brakes specifically. No car we've ever seen has any contact twixt either pad and disc without the brake pedal pressed.

Think about how brakes work, especially sliding calipers. They only apply pressure, and then release pressure, they never actually pull back. When you apply the brakes, the brake piston pushes one pad into the rotor, and pulls the outside one in. Once you release the brake, the pressure is simply relieved, the piston doesn't pull back into the caliper. Even if it did, the pad would have to be somehow attached to the piston in order to be pulled back as well. Then, in a sliding caliper, the outside pad should still be touching the rotor anyways.

I'd go as far as to say if your pads actually pull away from the rotor when you release your brakes, then something is wrong, not the other way around.


The only thing I can think of would be if the rubber seals on the piston were strong enough to pull the piston back. In which case it would have to push all that brake fluid back up through the lines and stuff. Unlikely.

 

[eiriksmil]

The piston pushes the inside pad outwards. The inside pad is also locked to the piston (caliper makers use different techniques), so that it'll retract when the piston does. The outside pad is connected to the inside pad via the spring, so the outside one follows the inside one when it's pushed out - or is is retracting by itself (as in when you release the brake pedal).. So yeah, they do pull away..

I've had a car with contact between pad and disc when the brakes were released: One of the calipers had stuck.. Ended up by almost burning me' hand on the wheel, it smelled miles away and if I had continued it would've started smoking. Pads and discs are separated when you're not having your foot on your brake pedal - sensibly enough

 

[Perfect Balance]

The piston pushes the inside pad outwards. The inside pad is also locked to the piston (caliper makers use different techniques), so that it'll retract when the piston does. The outside pad is connected to the inside pad via the spring, so the outside one follows the inside one when it's pushed out - or is is retracting by itself (as in when you release the brake pedal).. So yeah, they do pull away..

Ok, but you've got one major thing wrong. The piston doesn't retract, it simply releases pressure. Ever had to push the piston back in with a C-clamp after changing pads?

Also, the only cars I've ever worked on that actually had the pad attached via a spring mechanism to the piston were Jeeps, much less connected to each other. (Have a pic of this? I've never seen both pads connected to each other. Maybe in drum brakes.)


EDIT: Ok, let's say you're correct. What exactly makes the piston retract? The brake fluid isn't going to magically move back into the lines, pulling it in. If it was a completely sealed unit, then when the master cylinder plunger moves back it would pull the pistons in, but it's not.

 

[homeforsummer]

And I rebutted a different point, but alluded to your earlier statement above with the pertinent part bolded. I'm pretty sure that suffices for my argument. You. specifically. mentioned. Mercedes. Then you said they suck because of the nightmare of hill starts. I pointed out that its hand released, negating your point.

Show me where I disagreed that Mercs used a hand-released parking brake. I wasn't aware they had hand-released ones in the first instance so on that I stand corrected, but you appear to be making the assumption that I'm continuing to bash Merc in particular, which is untrue.

And regardless of how they're released, having a little lever roughly where a bonnet release would normally be (have a look in any modern Merc cos that's where the handbrake release is) is much clumsier than having a normal lever. And it seems pointless to me having two different levers (a foot pedal and a hand release) to operate the same function when a single lever would suffice. That'd be like having two steering wheels, one to go right and the other to go left.

 

[eiriksmil]

Ok, but you've got one major thing wrong. The piston doesn't retract, it simply releases pressure. Ever had to push the piston back in with a C-clamp after changing pads?

Also, the only cars I've ever worked on that actually had the pad attached via a spring mechanism to the piston were Jeeps, much less connected to each other. (Have a pic of this? I've never seen both pads connected to each other. Maybe in drum brakes.)


EDIT: Ok, let's say you're correct. What exactly makes the piston retract? The brake fluid isn't going to magically move back into the lines, pulling it in. If it was a completely sealed unit, then when the master cylinder plunger moves back it would pull the pistons in, but it's not.

I'm unsure of the last part, but I do remember two things from my caliper story below. One was that I pushed the inner piston out from the disc and I saw less and less of the piston. Second, when I loosened the bleeding screws, more fluid came out as I pressed the piston back..

I remembered wrong about the inside one being connected, it was the outside one. Don't ask me how that works though, I just remember I had a living hell out of these rusty calipers I can however show you the spring, here's my old caliper, the spring was out here but you can see what it's connecting:

When I got the calipers repaired, I got the wrong springs. I made one out of paper clip for a 15 mile drive (very temp in other words), the outside pad then touched the disc from time to time because it didn't go off the disc like the inside did.

I feel like you're either testing me, or you're as clueless as myself Either way I feel dumb, haha

 

[Perfect Balance]

But it does physically go into the caliper when it releases pressure, doesn't it?

Not really, it just releases enough so that there is no more pressure acting on the pads(at which point they would still be touching, but without any load applied to them), but it can't actually pull it back any more than that.

I remembered wrong about the inside one being connected, it was the outside one. Don't ask me how that works though, I just remember I had a living hell out of these rusty calipers I can however show you the spring, here's my old caliper, the spring was out here but you can see what it's connecting:

That spring is just there to keep the pad positioned correctly and in contact with the piston. It reduces noise basically. Do you really think that that little spring is going to push the piston back into the caliper, pushing the fluid in the caliper back up the lines into the master cylinder, when it requires a c-clamp to do it otherwise?

Pistons don't really move that much either. A gap of 1mm or so would require a full pedal stroke before they even contact the rotor.

EDIT: If you guys really don't believe me I'll start getting a video of every single car's brakes that I work on, I'm that sure of myself.

 

[eiriksmil]

Do you really think that that little spring is going to push the piston back into the caliper, pushing the fluid in the caliper back up the lines into the master cylinder, when it requires a c-clamp to do it otherwise?

**** no, I'm not stupid either.. But I remember now, it's the outer that's connected and the inner that's loose. When there's no more pressure on the piston and you have no spring attached between the pads, the inside pad will have a life of its own. The spring makes the inside pad not grind on the disc..

Man, I've used SO many words on something I could've explained far shorter.. Expressing owns me

 

[Perfect Balance]

That works.👍

 

[Duke]

The piston pushes the inside pad outwards. The inside pad is also locked to the piston (caliper makers use different techniques), so that it'll retract when the piston does. The outside pad is connected to the inside pad via the spring, so the outside one follows the inside one when it's pushed out - or is is retracting by itself (as in when you release the brake pedal).. So yeah, they do pull away..

Spring? What spring? There aren't any springs on disc brakes I've seen. There is nothing connecting the inside pad to the outside except the body of the caliper itself.

There is also nothing to retract the piston. It just ceases to squeeze, as PB mentions above. If the piston sticks, it will keep some pressure on the rotor, and that's a problem. But otherwise, the pads will sit just off the face of the rotor, with virtually zero clearance.

[EDIT] OK, I see your picture above, but that's really just a rattle clip, or maybe something to make assembly easier.

 

[niky]

I've driven only three automatic cars (Ford Explorer 4.0, Jaguar XJ 3.2, Jaguar S-Type R) and none were that stressy to stop. Though the S-Type had a bloody stupid pushbutton handbrake (because a LIGHT is going to stop you, right?).


Incidentally, all three were also my dad's cars and we both went to press imaginary clutch pedals - moving our hands over to the gear lever at the same time - at various points while driving them. I also have gone to change up to 6th and caught myself in time in both my own MX-3 (that I've had for 6 years) and daan's 406 Coupe, which only have 5 speed boxes, but only after owning the 6-speed ST220 for a while

I only drive 6-speeds occassionally, when I get a press hack.. but I've gotten so used to super-low rpms at cruise while using 6-speeds and using our 5-speed AT CR-V, that I often look for 6th gear on our other cars. My Mazda redlines at its top speed, while the truck does a buzzy 3000 rpm at 100 km/h. Which wouldn't be so bad, if it weren't a diesel.

I thought of something yesterday, while we're on this.. Do auto drivers go through more pads than manual drivers?

In my experience, yes, but experiences vary. On some modern AT cars, emissions-compliance gives them throttle over-run when you let off the gas, so they don't decelerate as quickly as you'd expect.

Which leads to much brake-tapping, which probably leads to more wear, unless you re-train yourself to get used to it.

-

Column versus stalk... I prefer column... easier to maintain... easier to use... and I quite like Honda's way of doing it on some of their cars... mount it high up off the floor, nearer the steering wheel... why this doesn't become more common is beyond me.

Having driven a few cars like this, it really is more convenient... as long as you're not sitting five feet away from the steering wheel.

 

[nobuffalo]

I prefer this setup.

Also another good reason for the foot-operated parking brake.

Edit, nevermind, that's a hand operated parking brake.

 

[niky]

See... my problem with a column-shifter is that you have to reach behind the steering wheel to get at it. And wade around in that mess of stalks that most manufacturers have there, already.

A floor shifter provides less clutter at the wheel, and can be placed so that it's within your reach without having to change positions or stretch.

Honda's compromise, one that I'm seeing on many newer minivans and crossovers, puts the shifter close to the steering wheel, so you don't have to take your hand very far away to shift... but still out of that mess behind the wheel.

 

[Thatman]

See... my problem with a column-shifter is that you have to reach behind the steering wheel to get at it. And wade around in that mess of stalks that most manufacturers have there, already.

A floor shifter provides less clutter at the wheel, and can be placed so that it's within your reach without having to change positions or stretch.

Im really trying to think of when there was a clutter of things....I dont know the 94astro,89Buick,02buick,89Chrysler, and 00Expedition have no clutter but the steering wheel in front of their column shifters. Could I see like a picture of what you speak of?

 

[Rotary Junkie]

Almost anything with a column shifter will be devoid of any other stalks etc on the same side as the shifter.

 

[nobuffalo]

Perhaps you guys know but that's a manual shifter, and that to me is why I like it. Nothing like cruising in my dad's 56 and shifting that way. Three on the tree.

 

[eiriksmil]

How cool ain't that, manual gearing on the column.

There is nothing connecting the inside pad to the outside except the body of the caliper itself.

[EDIT] OK, I see your picture above, but that's really just a rattle clip, or maybe something to make assembly easier.

Without it, what would hold the inside pad so it doesn't grind on the disc? The inner pads and the pistons aren't physically connected..

 

[Rotary Junkie]

Simple... Nothing would. And generally wouldn't be necessary, seeing as little to no pressure would be applied to the pad, meaning negligible to no wear.

 

[nobuffalo]

How cool ain't that, manual gearing on the column.

It may have been a common thing back in the day, but I still like it.

 

[Famine]

But otherwise, the pads will sit just off the face of the rotor, with virtually zero clearance.

Exactly. They're not touching it.

Then, in a sliding caliper, the outside pad should still be touching the rotor anyways.

Except it seems they are...

Nothing I've ever read would suggest to me that either pad is ever in contact with the disc unless braking. No experience I've ever had with the braking system on cars suggests to me that either pad is ever in contact with the disc unless braking. Even, and I'm loathe to quote it, Wikipedia doesn't agree that a pad should touch a rotor:

a piston on one side of the disc pushes the inner brake pad until it makes contact with the braking surface, then pulls the caliper body with the outer brake pad so pressure is applied to both sides of the disc.

Floating caliper (single piston) designs are subject to sticking failure, which can occur due to dirt or corrosion entering at least one mounting mechanism and stopping its normal movement. This can cause the pad attached to the caliper to rub on the disc when the brake is not engaged, or cause it to engage at an angle. Sticking can occur due to infrequent vehicle use, failure of a seal or rubber protection boot allowing debris entry, dry-out of the grease in the mounting mechanism and subsequent moisture incursion leading to corrosion, or some combination of these factors. Consequences may include reduced fuel efficiency, excessive wear on the affected pad, and friction-induced heat warping of the disc.

(I left the last sentence in just to wind Scaff up )

Nevertheless, sure as I am that the pads do not contact the disc at rest, I've passed this one upstairs to my tame Bentley mechanic. His decision will be final

 

[TheCracker]

There's a Lancer Evo VII that sits on the street just around the corner from my work. I often pass it whist sat in slow moving traffic waiting at the traffic lights. Now this car is used because it changes the direction it faces and sometimes it isn't there at all. The one thing that is constant is the fact that the disks have always got a layer of surface rust on them.

If pads do touch the surface of the disk, the disk surface would always be shiny and clean from the constant contact wouldn't they, even if the car is used infrequently (which is pretty criminal with the sort of car it is).

 

[nobuffalo]

Not really, moisture on the rotors can cause a slight amount of surface rust, especially if the car is used infrequently. Once the car is driven and the brakes are used the rust will wear off but after sitting for a while they can rust up again. Possibly even over night or a few days.

 

[Famine]

Except for the part where the pads touch - if they DO touch - which aren't exposed to the air. Remember, rust need iron + water + air...