Brake system design

[packtim]

Can anybody give me some pointers on the braking system design for an FSAE car?

Ive have been looking at it for a month or so now, but keep going round in circles trying to figure out what is best. Ive decided on 4 outboard brakes for the car.

Ive figured out the force I need to stop the car is (using f=ma),
Assuming: car is braking from 60mph to 20mph (29.08m/s to 11.11m/s), 330kg is wet weight of car. Assuming it brakes in 15m, a=-24.1 m/s^2
f=330*-24.1

So force required to stop the car = -7950N

Ive been looking as discs and calipers quite extensively, and have decided on 4*200mm, 6mm thick scooter discs.I'm buying them in as we have to have all CAD and Spec for the car done in 2.5 weeks, so dont have the time to design them. However, i'm having real problems selecting the right calipers and master cylinder for the car. Ive had a look at Wilwood GP 320 brakes, as they will accommodate the disc it seems. I have worked out stopping forces previously for other systems first, but seem to be going round in circles.

What should I start with for the braking system? Factors i have considered so far that will significantly affect it is: Master cylinder size, Pedal ratio, caliper piston area, and brake pad Cf.

Any pointers would be much appreciated.

Thanks


Tim

[Cement Legs]

If you do a search for brake design you will find repeated reference to a book by Dr. Woods on brake design. It is a system dynamics textbook that he wrote and in chapter 10 he refers directly to the example of a brake system for FSAE. I believe all the formulas you need are there. Put it all together in a nice big spreadsheet and just change whatever contstraints you want for instant results on what effects it will have on your overall design.....

[kwancho]

I would recommend that you do your calculations based on the maximum decelerative capability of your tires, which is around 1.5gs.

[Ianthegypo]

If anyone is a bit stuck with the calculations for braking requirements, i have a fairly extensive excel spreadsheet that can work out a fair bit.

Leave a reply and ill email it to people
Cheers

[raska]

I hate to make it look like a F4i CAD thread, but I'd like to take a look at that. Thanks in advance.

email edited out for spam purposes.

[Agent4573]

I have a pretty nice spreadsheet that will estimate how hot your rotors are going to run for people designing them. I'm not to keen on sending it out, but if you want me to run your numbers just let me know.

[drivetrainUW-Platt]

Originally posted by Ianthegypo:
If anyone is a bit stuck with the calculations for braking requirements, i have a fairly extensive excel spreadsheet that can work out a fair bit.

Leave a reply and ill email it to people
Cheers

we have a number of freshman working on the brake team this year and I just dont have the time to coach them since I'm redoing the entire drivetrain again this year(among being a junior in the engineering program and some hard classes). I would love to get this spreadsheet over to those guys so they can get moving on telling the d-train guys what size brakes we need.
please email: duwem@uwplatt.edu
thanks

[packtim]

Originally posted by Ianthegypo:
If anyone is a bit stuck with the calculations for braking requirements, i have a fairly extensive excel spreadsheet that can work out a fair bit.

Leave a reply and ill email it to people
Cheers

I'd really appreciate it if you emailed me this too, emailhttp://fsae.com/groupee_common/emoticons/icon_razz.gifacktim@hotmail.com


Thanks a lot

Tim

[Homemade WRX]

while we are talking design, what types of deceleration rates do you guys shoot for?...just wondering what others are shooting for.
thanks, Micah

[packtim]

From reading this forum, it looks like people are assuming around 1.5 to 2 g's. Initially, I assumed the car would decellerate from 60mph to 20mph in 10 m, around 4 g's (i think this is very optimistic). Therefore I think 1.5 to 2 g's is a good guess.


Tim

[McFly]

Unless you guys have some sweet ass tires that I don't know about, I do not believe that you are going to be able to deaccelerate at 2 g's. Your normal race tire cf is going to be around 1.5, so with even weight distribution, no weight transfer and maximum tire grip your maximum braking is going to be around 1.5 g's. (That is saying you are not running an aero package with the extra downforce.) During testing last year we were seeing about 1.1 - 1.2 g's in braking at maximum. I would design to brake from 1 to 1.5 g's.

[packtim]

OK, thats great, I was just Guestimating the values. Thats helped me as well!


Thanks


Tim

[Agent4573]

i think most teams assume around 1.5 g's for the michigan parking lot, but some teams have reported right around 2 g's from formula student. Appearantly the track is much better.

[packtim]

OK, thanks. im having a fair few problems with the braking system so this has eliminated one of them!


Thanks

Tim

[B]

Check out UTA's webpage http://maepro.uta.edu/fsae/trackpages/incar30June04TXMS.html
They have a G-plot idicating 1.5G's for braking, 1.7G lateral, and 0.7 accel.

I can't emagine to many teams topping them, especially beginning teams. From memory they used hooster tyres.

[vandit]

Originally posted by Ianthegypo:
If anyone is a bit stuck with the calculations for braking requirements, i have a fairly extensive excel spreadsheet that can work out a fair bit.

Leave a reply and ill email it to people
Cheers



i already did some calculations.....our car weighs 300kgs(including driver)....with 45% front weight distribution .......i planned to use 2 outboard disc in front and one disc in rear mounted on diff.......since we r first year team rom india and i dont have any senior members to check my calculation and the only book which we have got in our library is Race Car Vehicle Dynamics which only gives formuls for weight transfer..........so i would be really thankfull if u can mail ur spreadsheet to me(goyal.vandit@gmail.com)

[Ianthegypo]

I will email the spreadsheet to the interested people tonight, ive had to make it a bit more user-friendly, so you can adjust figures and such. It will also tell you the max deceleration based on tyre friction coefficient, which I believe is the only ture way of determining this decel.

[Draksia]

If you could cc me on that I would be thankfull.

draksia@gmail.com

[packtim]

Thanks very much I really appreciate this.Dont think my email address acme out quite right before, its

packtim@hotmail.com

cheers

Tim

[Homemade WRX]

I'd like a copy as well...
drummerboy1784@cox.net

I have a spreadsheet going but it's just of various set ups...doesn't do much with actual weight transfer etc...

[terra_dactile]

hi ian,
if you could email the spread sheets to tarradactle@yahoo.ca
it would be most apreciated
thank again
JUDE

[Alan S.]

if you could email me that spread sheet also
bigal_009@hotmail.com
im the freshmen at uwp trying to figure out the brakeing system so it would be a termendious help,
thanks

[Ianthegypo]

Ive sent the spreadsheet to everyone who asked. Any chance of some feedback on it, whether all the neccessary stuff is covered. Would be appreciated

[RiNaZ]

hey ianthegypo,
can i get a copy too mohdnurm at erau dot edu. Thanks

[Alan S.]

thanks a ton, this will help me out a lot in the cacluations

[DanHanara]

Can I get a copy of that spead sheet (from ianthegypo) thanks

[WALDOPIPE]

hi ian,
Im from venezuela from team formula sae UCV and we are having so mucho problems trying to calculate the rotor sizes and the master cylinders.
if you could email the spread sheets to waldopipe@yahoo.es
it would be a very big help
thanks

[Ianthegypo]

Ive sent it to as many people as i can, but Danhanara, you didnt leave your email address....

[Agent4573]

paul@hatespeople.com http://fsae.com/groupee_common/emoticons/icon_smile.gif

[Homemade WRX]

Originally posted by Ianthegypo:
Ive sent it to as many people as i can, but Danhanara, you didnt leave your email address....
you should just put it on a server to save yourseld time...

[Alan S.]

so you guys realise, this is useing a 2 piston caliper if you dont know how to change it to one and your useing single piston pm me and i can tell you what cells to change

[romkasponka]

romkasponka@gmail.com

[Homemade WRX]

Originally posted by Alan S.:
so you guys realise, this is useing a 2 piston caliper if you dont know how to change it to one and your useing single piston pm me and i can tell you what cells to change
for the formula I have it says a single piston has the same clamping force as a double of the same size. Floaters I believe were the ones that make a difference...I'll double check

[MoboostWRX]

I will take a copy.
pcsolomo@ksu.edu

Thank You very much.

[Ehsan]

ehsan.farkhondeh at gmail.com

Thanks

[Aegis Talons]

Hey Ianthegypo,
can I get a copy also of the spreadsheet.
aegistalons at gmail dot com
thanks,
Aegis Talons

[Ivo]

Please can you send me a copy of this spreadsheet. It would be very much appreciated.

my e-mail is ivo.nikolov@imperial.ac.uk

[Nick-7]

Could you send a copy of the spreadsheet to nshankins21@tntech.edu

Thank you

[James Morrison]

Could I please have a copy too? venomouscamaro@yahoo.com Thanks!

[Alan S.]

while it was nice haveing this to get me started i STRONGLY advise programing your own excel sheet, just to make sure you know everything thats going on and not just tryusting someone elses numbers

[Dr. Bob Woods]

My textbook "Modeling and Simulation of Dynamic Systems" from Prentice Hall has the entire analysis and design parameters for a FSAE car in chapter 10.

Dr. Bob Woods
UTA Faculty Advisor

[Marshall Grice]

There should be some sort of script that monitors any brake design threads and automatically replies with Dr. Wood's book. Seems like a waste of time for him to have to post the same reply every 2 months.

[Alan S.]

to awnser my previous question on floater
a floater 1.75" = a dual oposeing with 2 1.75", if you dont belive me look it up and find a sorce to prove me wrong,

secondly i STRONGLY recomened dr woods book, being as im a freshmen designing the break system at UWP it helped me out a ton even though i aproched the problem a differnt way then he did in the book just the equations for things like weight shift help a lot

[drivetrainUW-Platt]

too bad young Alan still hasn't learned how to spell brakes....freshman, I tell ya!

[Wren]

could I get a copy of the spreadsheet as well?

wren.keith at gmail.com

[Alan S.]

hey at least i can do the math....thats what matters right? guys 1+1 = 3 right?

[ClaytonA]

Originally posted by Ianthegypo:
If anyone is a bit stuck with the calculations for braking requirements, i have a fairly extensive excel spreadsheet that can work out a fair bit.

Leave a reply and ill email it to people
Cheers
would love a copyc.c.arms@bigpond.net.au

[hars orion]

hey can i get a copy of the spread sheet too

mail :harshal.shah@orion-racing.com

Harshal shah
brakes
orion-racing 09

[Zac]

probably not since that post is 4 years old.

[Adambomb]

Well, at least they used the search function and checked out what has been discussed already!

Honestly, I still don't understand why people seem incapable of designing a brake system on their own; sure, there are a lot of parts, but they aren't that complicated. In all honesty it's one of the more simple systems on the car.

Or maybe I've just seen too many of these "design brake system for me" posts this week... http://fsae.com/groupee_common/emoticons/icon_rolleyes.gif

[Adambomb]

...Furthermore, having picked apart the braking calculations spreadsheet we've used for years, in the long run you're probably better off making your own anyway! After much scouring I determined that ours was correct (although a bit confusing in its layout); I would never blindly assume a braking system calculations spreadsheet I got from a random student on a forum is correct!!!

Besides, even if it is correct, if you aren't intimately familiar with the assumptions that went into it, the proper range of conditions, etc., you could easily end up as another victim of "garbage in - garbage out!"