Brakes

[DannytheRadomski]

The mythical WWU V8 car had a lot of advanced features on it (at least for the time) e.g. engine was a stressed member, suspension mounts on the transaxle, in hub brakes, etc. The one that doesn't make sense to me is the in-hub brakes. If you had to change a tire of wheel the brakes would just get in the way and become more of a nuisance than a benefit. Why wouldn't they just use normal discs? Is there a benefit to in hub brakes? Is there a "perfect" brake setup?

I think showing off is just as good a reason as any, but the more I read these forums the reasons for doing certain things are much more pragmatic than I expected.

http://dot.etec.wwu.edu/fsae/v30/image024.jpg
[IMG]

[dmacke]

Not a brake guy but one benefit I could see would be the larger brake rotor diameter. Using a typical setup the rotor diameter is limited by the caliper. With the hub motors, the rotor is limited by the wheel diameter.

[DannytheRadomski]

But if you brought the rotor outside the wheel hub then the only things limiting your rotor size is the suspension and steering

[DannytheRadomski]

Nevermind, I think I figured this out. Besides added rotor size, it would always be parallel to the direction of the wheel, which would reduce lateral run-off.

I hope that this isn't annoying to anyone, that I posed a question and then answered it myself (correct me if I'm wrong, i joined these forums to learn more about FSAE), but the other orginal question still stands. Is there a "perfect" brake setup?

[PatClarke]

Danny,
a few questions to ask about the UWW brakes.

1. What happens when you mount a caliper on stilts like that?
2. Where does the brake temperature go? and
2. What does that do to tyre pressure?

Pat

[Rex Chan]

Danny - I'd like to think there is no such thing as perfect/prefection, only the best compromise design, based on your team's goals and resources.

Have you seen the Hamburg 2012 car? The one with the big wheel bearings? That had a similar idea for the rotors. Running Snail RS12-LC4 - wheel carrier (front) (http://www.youtube.com/watch?v=9rbw-_6yTkw)

[Damon Pipenberg]

One piece of advice for this competition, and engineering design in general: Don't make the mistake of assuming that a trick design is better than a more traditional design just because of its uniqueness. I'm absolutely not trying to discourage you from pursuing unique solutions, just saying that doing a proper trade study is important to identify the best solution for a given problem.

Yes, a custom V8 and transaxle is a damn cool component to build, but unless your team has tremendous resources at its disposal, probably not the best design choice to make if your goal is to win FSAE. I'd venture to guess that other subsystems on that car suffered due to the amount of time sunk into the design of the powertrain.

Following on Pat's post, I'd spend some more time looking at the design of that corner assembly and discussing with your teammates. I think you'll identify a number of questionable design compromises.

[Kirk Feldkamp]

Originally posted by Damon Pipenberg:
Yes, a custom V8 and transaxle is a damn cool component to build, but unless your team has tremendous resources at its disposal, probably not the best design choice to make if your goal is to win FSAE. I'd venture to guess that other subsystems on that car suffered due to the amount of time sunk into the design of the powertrain.

Close... the engine subsystem suffered, actually. Haha. I was told that so much time was spent just designing, building, and assembling the parts that they didn't have a ton of time to actually develop the engine. IIRC, the connecting rod bearing selection was a major failure point, and connecting rod life was being measured in minutes, not hours. Ultimately, it never saw competition time because the engine didn't include an on-board starter. That was the first year where the rules required them, and for whatever reason, it wasn't integrated.

For what it's worth, there always seems to be a few design philosophy "camps" among FSAE teams. One camp views the comp as an engineering problem that focuses on generating points at comp (the "systems" approach)... while the other camp just wants to design and build the most bitchin' thing they can (the "dude!...sweet!" approach), with points (and actually winning) basically as an afterthought. There are definitely lessons to be learned either way...

-Kirk

[Buckingham]

Nevermind, I think I figured this out. Besides added rotor size, it would always be parallel to the direction of the wheel, which would reduce lateral run-off.

who says the orientation of the rim is always parallel to the spindle axis under load?

With wimpy wheels, you could actually see MORE misalignment between the rotor and caliper under heavy loading.

[Christian Amersbach]

Originally posted by Rex Chan:
Have you seen the Hamburg 2012 car? The one with the big wheel bearings? That had a similar idea for the rotors. Running Snail RS12-LC4 - wheel carrier (front) (http://www.youtube.com/watch?v=9rbw-_6yTkw)

Thats not Hamburg, but Amberg-Weiden ;-)

[Adambomb]

I remember that brake setup as a picture design judges will often show and then ask you describe "what is wrong with this picture." http://fsae.com/groupee_common/emoticons/icon_wink.gif

I don't remember which one came first, but it looks quite similar to the ZTL (zero torsional loading) setup on Buells:

https://sphotos-a.xx.fbcdn.net/hphotos-ash4/415215_10100412841020250_36104725_o.jpg

As you can see instead of having two smaller rotors you have one f-massive one with an 8-piston caliper that looks like it came off the front of a new Corvette. The buttons are mounted to the outside of the rim so the spokes see no loading other than supporting the bike (note how spindly they are). Now compare that to an "inside the suspension" rotor where your loading goes through the spokes, through the hub and spindle, and then to some type of inboard rotor mount... I haven't seen a real by the numbers comparison regarding unsprung weight or rotating inertia, other than most tend to claim it is "less," and most reviews I've read speak highly of its brakes and handling response. A couple caveats though; as you can see this implementation is a lot cleaner without any cantilevered caliper mounts, etc. As for cooling, I would guess there is not enough contact with the rim for it to really affect tire pressure, although the new EBR 1190rs now includes brake cooling ducts:
http://image.motorcyclistonline.com/f/newsandupdates/motorcycle_news/122_1107_erick_buell_racing_1190rs/32988562++w760+ar1/122-1107-01-o+eric-buell-1190RS-front-brake+.jpg

[Warpspeed]

It works on a bike, because the front wheel slides out vertically from the fork.

Changing a wheel on a car with a system like that would require unbolting the caliper.

[DannytheRadomski]

His point is still valid. With the greater surface area and the wheel being able to be lower weight, this might be a pretty good setup. Having to change a wheel would be its downfall, but there might be a clever solution to that.

Actually, in the TV special about Carroll Shelby after he died, they had a solution for changing the calipers on the GT40 that had something with a few pins because the brakes were getting destroyed at the speeds the GT40 could do at LeMans.

[Adambomb]

Originally posted by Warpspeed:
It works on a bike, because the front wheel slides out vertically from the fork.

Changing a wheel on a car with a system like that would require unbolting the caliper.

Actually it still isn't that simple (just changed the front tire on my Buell last week!). The caliper is a very tight fit to the wheel; so tight that you have to unbolt the caliper, then partially remove the axle and fender so you can rotate the RH fork leg CCW 90º to clear the mounting tabs, then align the clearance grooves in the rear of the caliper with the spokes, unbolt the brake hose clamp to get more brake hose clearance, then fanagle the whole thing apart http://fsae.com/groupee_common/emoticons/icon_wink.gif But then again on most bikes you have to remove the front calipers to clear the rims anyway.

I'd imagine you could do it relatively simply on a car if you simply had the brake floaters mounted to the inside of the rim and allowed the rotor to slide off the rim, although aside from that challenge I'd still be worried about camber compliance...floater design in itself could possibly get a little tricky.

[Warpspeed]

Another interesting little problem is that conventional calipers all have the mounting lugs on the inside of the arc of disc travel.

You would need calipers that curve the opposite way, which means you get to design and fabricate your own calipers, which opens up a whole set of interesting new problems to overcome.

I am not at all convinced that this is the very best way to go about impressing the design judges, the scruitineers, or to win races...

[PatClarke]

Actually, in the TV special about Carroll Shelby after he died, they had a solution for changing the calipers on the GT40 that had something with a few pins because the brakes were getting destroyed at the speeds the GT40 could do at LeMans.

Danny, the LeMans Fords weighed almost two tons and were doing more than 200mph on the Mulsanne straight before having to stop for the Mulsanne corner. The braking load was enormous! You had to be there to appreciate it!
Incidentally, the drivers did not come down through the gearbox to use engine braking, they simply stood on the brakes and when the speed was low enough, cluncked down into first gear and hammered out of the corner with all that 7 litre torque.

FSAE imposes nothing like that on the brake system.

The Ford LeMans brakes had a recirculating brake fluid system, dry break connectors on the calipers and quick detach calipers and brake rotors. The calipers and rotors were changed out at each pitstop.

Pat

[DannytheRadomski]

I wasn't trying to compare the GT40 to an FSAE car. I was just trying to think of an easy way to get the calipers off for wheel changes on an in-hub brake set-up. THey didn't really explain the set-up on TV. They simplified it by quite a bit.

I'm extremely jealous that you got to see the GT40 at LeMans. THe GT40 is among my favorite cars ever. The fact that it unseated Ferrari is amazing but, three years is even more incredible.

[PatClarke]

Actually Danny, I think it was the Mark 2 and Mark 4s, not the GT40 that had the quick change brakes.

BTW, officially, they were Ford GTs, the GT40 moniker came from the press.

The cars were designed and built in the UK from a design based on the Lola GT.

Of the original 105 GT40s built, only 1287 still exist today!

Pat

[PatClarke]

If you are new to FSAE Danny, you should know that the late great Carroll Smith who recruited and mentored most of the senior FSAE judges, including yours truly, was the race engineer on the Ford GTs when they delivered the 1-2-3 coup de gras to Ferrari!

Pat

PS, ALL Carroll's books should be in your personal library (edit)

[Warpspeed]

Originally posted by PatClarke:
PS, ALL Carroll's books should be in your personal library
Only two problems with Carroll's books.
1/ They fall to bits after being constantly read about 10,000 times.
2/ When loaned out to buddies, they very rarely ever come back.

[AxelRipper]

Originally posted by PatClarke:

The Ford LeMans brakes had a recirculating brake fluid system, dry break connectors on the calipers and quick detach calipers and brake rotors. The calipers and rotors were changed out at each pitstop.

Pat

Though you Aussies have found a bit better system in the 40 years since... http://www.youtube.com/watch?v=8XrFs3LJz4k