I want better/more brakes

[Pinecone]

11 minutes ago, A64Pilot said:

There is one really huge difference between Auto’s and Mooney’s.

An Auto at 70 MPH will have about the same braking effectiveness as it does st 30 MPH.

A Mooney will have very little effective braking at 70 MPH and its braking effectiveness increases rapidly with decreasing speed due of course to loss of lift. 

So I maintain that braking especially at high speed is very difficult in an airplane, it’s really tough to modulate the brakes to be just before the lock up point, so it’s very common to flat spot a tire if you brake hard, not wanting to flat spot tires, I don’t brake hard.

That is a big point of braking in an airplane.  And a Mooney, with the wing so close to the ground, is worse than some other aircraft.

[A64Pilot]

1 hour ago, Pinecone said:

Track/race cars have to deal with multiple hard braking events.   Airplanes don't.   

The reason you need to upgrade brakes on track/race cars is that stock car braking systems are not designed to deal with multiple hard braking events.  Which builds up heat, LOTS of heat.   As I stated before, my car with a pretty stock brake system (but a good one) I could boil 600 degree boiling point fluid.  But that occurred after getting off the track.  The easy fix was to drive around slowly for about 5 minutes to dissipate the extra heat

The initial cold bit is based on the brake pad compound, but good cold bite tends to loose performance when hot.

Don’t know about now with carbon brakes but back years ago particularity at night races you could see the disks glow a bright red, maybe even yellow.

 

[EricJ]

1 hour ago, Pinecone said:

The initial cold bit is based on the brake pad compound, but good cold bite tends to loose performance when hot.

Sometimes, but there you make the point that just different pad compounds can have very different behaviors.   So just the difference between two different pads, with different initial bite, and particularly the time to ramp up to initial bite friction or to peak friction, will make a difference in dry braking distance, with the same tire.   The faster a pad come up to a high friction coefficient, the faster the vehicle will start decelerating.   So even if everything else is equal, just that one characteristic will make a difference in dry braking distance.   There are many more parameters that affect dry braking performance, so even with the same tire on the same surface, dry braking distance can be significantly different from one system to another, on the same tire.   The same tire will have the same braking distance once locked, regardless of what system got it to lock, so the variance between locked and unlocked braking distance can vary significantly depending on the system.

All of that is for a single, cold braking event, just like airplanes do.

[A64Pilot]

Normally race pads don’t work well cold, they have to be hot to work well, as do the tires, they are “greasy” when cold

Normally stock pads don’t work well hot, but work well cold.

There are many other considerations like rotor wear, dust created and noise and pad life, everything is a trade off.

But I’m sure aircraft pads are very similar to auto stock pads, that is they work well cold, don’t chew rotors bad and give decent wear.

‘Oh, and another thing when stock pads and at least stock Cleveland on aircraft pads get real hot, upon cooling the are what’s referred to as glazed, they don’t work well after that. When racing show room stock many years ago I’d pull the pads and scrape the glaze off on concrete in between races, then put new ones on, we weren’t allowed to use race pads, stock only.

Get a stock Cleveland aircraft brake caliper hot and the silver paint turns color, I assume that’s intentional. Turns reddish maybe orangish from memory. 

Not sure why road racing motorcycle brakes don’t get hot like the cars, but they don’t. They will burn you if you touch them, but I’ve never seen one glowing.

[N201MKTurbo]

When my son was young we went quite a few monster truck shows. I really enjoyed the night shows because you could see the brake disks glowing white hot with sparks and glowing chunks flying off.

[Echo]

I would see ABS as a real improvement in aircraft brakes.  That is not happening for Mooney aircraft.  I get that you want a system to be functioning properly, but my brakes can hold my plane at full power.  They do what I need.  That is enough for me.  I do not pine in any way for improved brakes on aircraft.  My only concern is locking them and flat spotting a tire.  In Mooney's I have owned less use and never hard braking has been the way...The way has worked fine.  Motor vehicle brakes have improved trmendously over the decades.  Drive a 60's, 70's car and you need to plan ahead lol.  The weight reduction for fuel economy has helped in that department.

[Hank]

2 hours ago, A64Pilot said:

Not sure why road racing motorcycle brakes don’t get hot like the cars, but they don’t. They will burn you if you touch them, but I’ve never seen one glowing.

Racing bikes don’t weight much, call it 10-20% of NASCAR depending on displacement. 

[A64Pilot]

8 minutes ago, Hank said:

Racing bikes don’t weight much, call it 10-20% of NASCAR depending on displacement. 

However you would think that they would downsize the brakes to save not only weight, but much more importantly un sprung weight, the lighter you can make the suspension the more quickly it can react (less weight, less inertia) and that improves handling.

I had never thought about it before, there must be a reason.

[Hank]

15 minutes ago, A64Pilot said:

However you would think that they would downsize the brakes to save not only weight, but much more importantly un sprung weight, the lighter you can make the suspension the more quickly it can react (less weight, less inertia) and that improves handling.

I had never thought about it before, there must be a reason.

Brakes are sized to the wheel. Can't put our Itty bitty Mooney brakes on a racing bike. I'd guess the bigger bikes' front wheels are close to NASCAR diameter, even if not as wide. Some of the back tires look like they would fit the cars. Brakes have to fit the wheel . . . .

Also, momentum is mass x velocity squared, and the big bikes run faster than NASCAR. That's a lot of energy to dissipate. 

[A64Pilot]

I don’t think I made my point well

It wasn’t about anything except unsprung weight, that’s the part that moves when you go over a bump, the lighter you can make that the faster it will react and better it keeps contact with the pavement.

Rear wheel on any race bike does about zip braking, because under hard braking there is almost no weight on the rear tire, back when I was racing having a thumb lever for your left thumb to put just a bit of rear brake wasn’t uncommon, when cornering hard if the rear were to start coming out, a tiny bit of brake could bring it back, that’s all the rear brake was used for and modulating that with your foot was tough.

However it’s possible that with carbon that a larger diameter rotor could be made as light or maybe even lighter than a smaller diameter one. I’m real sure every possibility has been tried and what they are running is as good as it gets with current technology.

The other unusual thing about bike brakes was the rotor was floating, that is to say it was loosely mounted and could move a few millimeters side to side to keep perfect alignment with the calipers, which of course had opposing pistons, unlike the primitive one sided floating caliper like our aircraft have.

https://www.brembo.com/en/company/news/brembo-motogp-world-championship-2022

Our aircraft brakes are thankfully very primitive, about as primitive as possible. This makes them very reliable and easy to repair, I can’t unfortunately say inexpensive

[EricJ]

1 hour ago, Hank said:

Racing bikes don’t weight much, call it 10-20% of NASCAR depending on displacement. 

Bikes are much different not only because they don't weigh much, but the brakes are in open air to shed heat rapidly.   Cooling brakes on race cars is always challenging, not so much on bikes.   Airplanes are a little challenging this way, too, because the brakes can get hot from the required deceleration event, and then they go slow with not a lot of cooling air.
 

[A64Pilot]

A lot, most maybe racing cars brakes are ducted so that they actually get more cooling air than a bike, but I suspect that the swept area of a bikes brakes per lb of bike is much greater than most cars, due in part to diameter of the wheel, and of course a bike has two brakes on the front wheel, so larger per weight and twice as many. I think possibly that tradition is as much a reason why they have two as opposed to saving weight and going with one

But airplane brakes cooling under any kind of normal use isn’t an issue, if you use them hard yes they get hot, but then they have a long time to cool off so long as there is enough mass to absorb the heat formed from converting kinetic energy, cooling isn't as issue, now if you jumped on them hard every few seconds then yes it would very quickly become an issue.

Years ago I think it was Road and Track tested the then new VW Diesel Westfalia camper, they commented that it was the only vehicle they ever tested that they couldn’t get the brakes to fade. It wasn’t that the Westie’s brakes were so good, it was because the thing was so terribly underpowered that by the time they could get it back to speed the brakes had cooled off. 

[Pinecone]

16 hours ago, EricJ said:

Sometimes, but there you make the point that just different pad compounds can have very different behaviors.   So just the difference between two different pads, with different initial bite, and particularly the time to ramp up to initial bite friction or to peak friction, will make a difference in dry braking distance, with the same tire.   The faster a pad come up to a high friction coefficient, the faster the vehicle will start decelerating.   So even if everything else is equal, just that one characteristic will make a difference in dry braking distance.   There are many more parameters that affect dry braking performance, so even with the same tire on the same surface, dry braking distance can be significantly different from one system to another, on the same tire.   The same tire will have the same braking distance once locked, regardless of what system got it to lock, so the variance between locked and unlocked braking distance can vary significantly depending on the system.

All of that is for a single, cold braking event, just like airplanes do.

Initial bite is based on hitting a given braking force with a certain pedal pressure.  Push harder, they stop better.

But most pads for street cars, and I am sure for airplanes, are designed for good cold performance.  They don't need to be able to deal with high heat of hard braking multiple time.

My track pads are streetable, with reasonable cold bite.  Other track pads need a lot of pressure on the first few brake applications, but that is why there is a warm up/pace lap before the racing starts.

[geoffb]

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