Bicycle Brakes???

[Nitrous-X]

Hello everyone,
I am the chief engineer for the frame group from the Marquette University team and I was wondering if any of you guys out there has used bicycle brakes as your FSAE car braking system. Some members in my team had the idea of using them, but brake fade concerns me a lot. This is our first time racing with a brand new team, and I know having a good braking system is very important.
These bicycle brakes are very light, only 520g total, like this one http://www.hayesdiscbrake.com/product_hyd_hfxmaghd.shtml
Do you guys think that could handle the different events or do you guys think it will start fading fast? I would prefer going to like a motorcycle braking system, but they are really into this bicycle system, any suggestions would be appreciated and we are all excited to be racing at Detroit this year, expect a ligt/ simple car from us.
-Victor

[TomF]

We've used a mtb brake on our last car in the rear. Mind you, the car only weighed 125 kgs. We did have problems with brake fading especially at higher speeds than is usual on a FSAE/FS competition. The discs were also bended after a while, so I would not advice you to use such a system. There is also a doubt on the quality of the calipers, so we decided to use motorcycle calipers on those discs. To be short:

Go with some rear motorcycle brakes, those will suit the general FSAE car perfectly.

[Kirk Feldkamp]

You're gonna die. Some teams have a hard enough time stopping with kart brakes... and a FSAE car is a lot closer to the intended use of the kart brakes.

However, don't take it from me. You should do the analysis for yourself and make decisions based on that analysis. That's all that really matters. I could be wrong and you could cause a revolution in FSAE design.

-Kirk

[Nitrous-X]

Thanks for the reply guys, I agree with you guys in that those mountain bike brakes wont do the job, thanks.

[murpia]

One of the FStudent teams (I forget which) used Hope MTB rear calipers this year.

They couldn't get any data from Hope to do their system analysis, in the end they had to reverse engineer and rig test everything to determine if they were stiff enough, could handle the expected hydraulic pressure, and if the available pad material was suitable.

So, it can be done, but it's not easy...
Regards, Ian

[drivetrainUW-Platt]

chief engineer??? dont you mean engineer in training...bike brakes work great on bikes, but so do pedals. They are way too thin for our loading and would fold up like a wet noodle

[Peter]

I don't think they are to thin to be used on a FSAE car. The only problems we had, was when we used the car for speeds way above design speeds, in combination with other problems concerning our brake system... I think you can use them, just be sure to calculate it through. It all depends on the total package, as does everything.

Peter
Delft

[formula_wally]

FTABP - Formula Teams Against using bycle Parts.

Haha, sorry, I don't want to contiunally follow this post with burns, but these cars aren't supposed to be made with components from Huffy.

The functionality of a bike disc brake is there, but not the performance. You could try and show up with them, but good luck making it to design semi's.

[mtg]

At first, I thought this was a ridiculous idea- then thought about it for a minute. It could actually work if applied correctly:

Modern downhill brakes are pretty beef, check these (http://www.hopetechusa.com/voir_MM6F.html) out.

If you made a really light car, and had beefy downhill bike brakes in the rear, it might work out well. That being said, I wouldn't put them on there without fully investigating if they'll hold up or not.

[Maverik]

Is it worth it to look into, sure if you really want to know why it wouldn't work. It really is a simple thermal analysis, how much heat will those small little pieces of aluminum be absorbing braking your 500 lb (light car with driver) car from 50-60 mph... make no mistake about designing your car for lower speeds. Brakes are the one thing on a car in my mind that ALWAYS need to be overdesigned. Its really basic, if you can't stop because the things are faded or worse, cracked and non existant, the driver will get hurt or die or things will get nasty real fast. I have seen wheel/upright assemblys torn off FSAE cars at comp because the brake rotor design wasn't beefy enough to absorb and dissipate the heat (luckily no one hurt)... and those rotors were much beefier than any mountain bike brake I have seen. Again, do the analysis and you should reach the conclusion, but seriously don't skimp on your brake system ever.

[Garbo]

Also, MTB brakes have spring retraction on the pads which is certainly not desirable for a race car. The largest rotors that I have seen for bikes are about 200mm dia. x 2mm thick which is pretty skimpy. It is about the same diameter as Waterloo's 2006 rear rotors but way thinner. The mass of the rotor is important for more than structural reasons.

The speeds seen with our cars as well as the frequency of brake application are quite a lot higher than what bikes see. Based on the temperature data that we have for our brake systems, I would think that even the beefiest MTB system is undersized.

[Nitrous-X]

Thanks all for the comments, I totally agree with you guys. I myself don't want to run bicycle brakes. Yesterday, we had our weekly meeting and I told them that we should discard this idea, but they are still into it. We would have a factor of Safety of like .5 if we use this sort of brakes. I mean, they might work for like a turn and that's it. Its pretty much common sense stuff here. I think finishing the competition would be a big accomplishment for us, and I think these brakes would compromise our chances of doing anything.
-Victor

[Bill Kunst]

It would obviously be a multiple piece caliper, so putting in a spacer and running a bigger disc would be possible. Six pistons are sweet, and done correctly, with the right compounds, this would look really cool as well.

On another note, how many teams run brake ducting? It formula cars were built "beefy" enough, they wouldn't need it either. Just food for thought, and further discussion.
Bill

[Maverik]

I actually thought about mentioning brake ducting but figured it would open up the age old can of worms about whether aero is worth it. I could see higher end "juicy" style bike calipers (just hydraulic vs pull cable) working with slightly larger rotors (diameter and thickness) with ducting as long as there is adequate time to really cool the rotors on the track. I just don't know how many teams would devote enough time to develop brake ducting to work efficiently on top of figuring out how to make the bike brakes work with a decent factor of safety.

[brent_e]

Originally posted by Maverik:
I actually thought about mentioning brake ducting but figured it would open up the age old can of worms about whether aero is worth it. I could see higher end "juicy" style bike calipers (just hydraulic vs pull cable) working with slightly larger rotors (diameter and thickness) with ducting as long as there is adequate time to really cool the rotors on the track. I just don't know how many teams would devote enough time to develop brake ducting to work efficiently on top of figuring out how to make the bike brakes work with a decent factor of safety.

you could just double up on them.
is that reasonable??? put 2 of the 6 piston hopes on each rotor, or use 2 rotors instead of 1? might be a clusterfrig....might be lighter than a larger singe??

[Mike Cook]

Run a PS1. You can have a 6", .15" rotor drilled to high heaven if you'd like. I'd feel more comfortable with that than bike brakes.

[Chris Boon]

Tom,
125kgs seems like a really light car. Did yous decide to go Flintstone style and throw away the engine? We could only dream about getting near that figure!

[drivetrainUW-Platt]

Originally posted by Chris Boon:
Tom,
125kgs seems like a really light car. Did yous decide to go Flintstone style and throw away the engine? We could only dream about getting near that figure!

Naw this is a bicycle forum....put pedals, could you imagine a 21 speed formula car???
I heard that Micigian Tech ran a 7 speed honda F2 back in the day

[TG]

Originally posted by mtg:
At first, I thought this was a ridiculous idea- then thought about it for a minute. It could actually work if applied correctly:

Modern downhill brakes are pretty beef, check these (http://www.hopetechusa.com/voir_MM6F.html) out.

If you made a really light car, and had beefy downhill bike brakes in the rear, it might work out well. That being said, I wouldn't put them on there without fully investigating if they'll hold up or not.

Phenolic pistons... mind the glass transition temperature (Tg). I'd highly suggest looking into remanufacturing the pistons out of steel or titanium.

[Bill Kunst]

What is the glass transition temp for phenolics. If memory serves me correctly, they are used in many high temp situations, like the space shuttle nozzles? Or so I was told, but they use them on automobiles in ALOT of parts. Spacers for intakes, cap and rotor in distributors, etc. I am just curious what the trans temp is just so I can think about it for no apparent reason.
Bill

Bill

[KU_Racing]

um.. from the point of view who rides bikes competitively... stay away from bicycle brakes. They are designed to be high maintenance, and the brake pressures are extremely low. put 1000+ psi on one and all the seals will probably blow out.

[TG]

Originally posted by Bill Kunst:
What is the glass transition temp for phenolics. If memory serves me correctly, they are used in many high temp situations, like the space shuttle nozzles? Or so I was told, but they use them on automobiles in ALOT of parts. Spacers for intakes, cap and rotor in distributors, etc. I am just curious what the trans temp is just so I can think about it for no apparent reason.
Bill

Bill

Tg is 300C... not something you'll see a lot on the brakes, but is possible. Being that phenolics are a thermoset, they will just burn off, not exactly something you'd like to see on your pistons. Notice how none of the parts you described above are not exposed to direct high heat source. The pistons are on the back of the brake pad.

Space Shuttle rocket nozzles are made of carbon fiber reinforced carbon ceramic matrix composite coated with a gold alloy. They see thousands of degrees in the nozzle.

[Bill Kunst]

TG-
I will start thinking.
Bill

[McGuyver]

I think the bikes use cooking oil for fluid. Two of the most durable bike brakes may be adequate on the rear but,as was said previously, the pressure would be totally incompatible with normal brake systems.

These days, pedal power has exceeded 80 mph on level ground. The brakes used are probably good for one stop after a long coast to reduce speed.

I expect using a geo metro/suzuki swifts front brakes, uprights, and two of the short side cv shafts would be way too heavy to be competitive, despite swapping to billet calipers, drilled rotors, and grinding away any additional material. Fine for a feather weight street car though.

[jdstuff]

Originally posted by McGuyver:
I think the bikes use cooking oil for fluid.

To my knowledge, most bike brake systems (like Hayes, for example) use regular DOT approved brake fluid. Shimano hydraulic disks use mineral oil. Not sure about cooking oil though...but I've been out of the bike industry for a few years so I could be mistaken?

[Bacon117]

to quote an earlier post, you're going to die. lol

[McGuyver]

There are DOT approved vegetable based fluids. I found this while looking for the bike brake reference:

http://www.airflex.com/distributor/tech_info/H-05.htm

I agree with Bacon though. You are going to die. It's only a matter of time.

[Ehsan]

Are bicycle brakes super light? Yes

Are you gonna die? Yes.

There are far better places to save weight than the brakes. Intake, frame, uprights, A-arms, etc. Hell, build your exhaust from Titanium.

Places to not save weight: Brakes, seat belt, seat, rollbar. That just pisses off tech inspectors and design judges.

[repeatoffender]

Originally posted by Ehsan:
There are far better places to save weight than the brakes. Intake, frame, uprights, A-arms, etc. Hell, build your exhaust from Titanium.

Places to not save weight: Brakes, seat belt, seat, rollbar. That just pisses off tech inspectors and design judges.

It depends on how you define 'saving weight'.

If its to remove unneccessary material in the chase for optimised component geometry and safety while minimising component weight then whats the problem?

Removing weight just for the sake of it while comprimising function and safety is stupid.

If your not looking to optimise the car in terms of weight, cg height and polar moment of inertia everywhere then why are you even 'designing' the car the car to begin with? (with the exception of the learning experience) http://fsae.com/groupee_common/emoticons/icon_smile.gif

Also if you were to show judges that there was no need for that extra weight on the component then why would they be pissed off? If anything they should then be blowing sunshine up your arse for the fact you made the effort, learnt something and optimised it.

Im not having a go at you if it comes across antagonistic, thats not my caper. :P

[Ehsan]

No problem repeatoffender. Totally understand your point. By "saving weight", I mean pushing the limit/Factor of Safety.

To clarify my point, I am saying that in the real world FSAE, you only have time to really optimise a certain number of parts. And every year there are are a few parts that are probably a little more risky than others.

What I am saying is to not push the limit on those fundamental safety parts. Once you have optimised a lot of the rest of the car, then look at the safety systems. But at that point you should have some experience under your belt and probably a pretty good car. But if you show up with a mediocre car and you try to cut weight from the safety stuff, you will not get sunshine blown up your arse.

And with absolutely no attempt at insulting any team, someone who is on the boards asking about using bicycle brakes probably isn't on a team with a 350 lb car that finishes in the top 20. Probably more of a younger team, or at the very least a younger member, hence my advice.

[drivetrainUW-Platt]

Even the best teams have trouble with the braking event, it is 1/4 of a race car in my mind, going, stopping, turning and reliability.