0
$\begingroup$

For a project that I am a part of, we are in need of a brake pad material for use against an aluminum surface without causing any damage to it. So far through my research, the only safe alternative that I have found is 100% graphitized carbon brake pads.

What type of material composition should I be looking at which provides a reasonable coefficient of friction against aluminum while also limiting the wear to the pads and not the aluminum surface? Where would I find the physical properties of such a material?

$\endgroup$
  • $\begingroup$ Please define "no damage." Further, how many cycles of operation are required, what's the range of forces to be applied, length of an applied force, etc.? $\endgroup$ – Carl Witthoft Oct 4 '17 at 15:53
  • $\begingroup$ Is it possible to sheath the aluminum surface with a harder, more suitable material to handle the wear/heat/surface quality issues? If so, a conventional braking system may work for your situation. $\endgroup$ – Donald Gibson Oct 4 '17 at 17:03
  • $\begingroup$ I realize now when reading all answers and comments that I was very bad at explaining the situation. The goal is to create a braking system that is weight efficient and power redundant with the contact material being a continuous aluminum rail/surface. Unfortunately nothing can be done to the aluminum. The brakes are needed for high speeds (>500mph) and should preferably last at least 5 times. When further thinking about this a frictional brake system may not work due to the speeds it needs to operate at. Any help/idea is welcome. $\endgroup$ – Gustav Oct 4 '17 at 17:14
  • $\begingroup$ And ‘no damage’ is probably the wrong way to put it. The requirement is that minimal damage is done to the aluminum rail/surface and the brake pad material needs to be of a lower hardness than al6061. $\endgroup$ – Gustav Oct 4 '17 at 17:17
  • $\begingroup$ I should think the owner of the rail would be supplying you with very specific requirements. $\endgroup$ – agentp Oct 5 '17 at 13:42
2
$\begingroup$

Just remember that "soft" materials wear "hard" ones : brake pads on cars wear the steel discs... So, the aluminium will wear as it is friction based.

Edit : What about a water dynamometer? Ie basically pumping water and loading the pump to increase the resistance?

One brake that won't wear is a non-friction one : an eddy brake based on electrical current : used on buses , coaches, heavy goods vehicles may be worth considering...

Here is a link to Telma one of the manufacturers, explaining its function.

| improve this answer | |
$\endgroup$
  • $\begingroup$ Thank you for the answer but I realize now that I probably expressed myself wrong, because as you say, any frictional based braking system will cause wear to both parts of the system. The main requirement that the system has is that the brake pad should be of lower hardness than the aluminum that we are braking against (6061). Yes, I am aware of eddy brakes (both active and passive) however our wish is for this system to be power redundant (which could be done with passive eddy brakes but it doesn’t suit our design). Any help at all is welcome (maybe you know of another method of braking?). $\endgroup$ – Gustav Oct 3 '17 at 17:02
  • $\begingroup$ What about a water dynamometer? Ie basically pumping water and loading the pump to increase the resistance? $\endgroup$ – Solar Mike Oct 3 '17 at 18:01
1
$\begingroup$

Depending on the loads rubber might work, often used for bicycle brakes on alloy wheel rims.

Another option might be to use rubber rollers or wheels which contact the rail and fit them with a braking system much like road wheels on a car. The advantage of this is that as long as you don't lock them you are braking vial rolling contact rather than sliding friction directly onto the rail itself which should cause much less wear.

Obviously it is also important that the contact surface is kept reasonably clean as any grit that gets between the rail and the braking surface will accelerate wear. One way to achieve this is semim-rigid 'wipers' such as you see on a lathe saddle to keep out swarf.

| improve this answer | |
$\endgroup$
0
$\begingroup$

If your aluminum surface is like a traditional rotor or drum, and significant braking force is required; aluminum does not have good elevated temperature strength and may fatigue/crack.

| improve this answer | |
$\endgroup$
  • $\begingroup$ So a problem of aluminium - what solution do you offer? $\endgroup$ – Solar Mike Oct 3 '17 at 18:40
  • $\begingroup$ Unfortunately nothing can be done to the aluminum and it is a continuous rail/surface. $\endgroup$ – Gustav Oct 4 '17 at 17:15
0
$\begingroup$

a vehicle going 500 MPH will contain a huge quantity of kinetic energy which the brakes will need to dissipate. This will be difficult to do without affecting the 6061 aluminum either by heating it to the point where its alloy characteristics are lost or by rubbing material off the aluminum component. for example, consider a large airliner. at full gross weight for takeoff, a panic stop from the decision (takeoff or abort) speed (about 150-200 MPH) down to zero will leave the brake discs on the main landing gear red-hot, blow out the tires, and set them on fire. it is unreasonable to require a stop from 500 MPH to not damage the aluminum part.

| improve this answer | |
$\endgroup$

Not the answer you're looking for? Browse other questions tagged or ask your own question.