Upgrading the braking system - Hydraulic ideas ?

[MadMatt]

Hello guys,

I have a project to do and I would need ideas for it ! The aim is to re-do the braking circuit of a SHELL ECO MARATHON vehicle ! This is my school's vehicle :



Last year we finished 12th out of 86 competitors and 5th overall according to the fuel used. I was not part of the project last year, but this year yes, and we plan to do even better !

The plan to upgrade the brakes which are at the moment drum-type brakes, is to use discs from a bike.

However I have worries about the hydraulic system. 1 lever has to push the pistons of 2 different calipers. Of course the piston diameter of the lever or its stroke cannot be changed, so what guys would you purpose as ideas for me to investigate ?

I've got few ideas already but it is good to have external ideas/opinions, it gives more possibilities and can end up with a better finished product !

Thanks in advance !

[mep]

Why can't you change the piston diameter?
Why don't you use 2 circuits like it is done on a bike?
One for front and one for rear. You can make them operated by the same lever and even integrate some mechanism to change brake balance.

[747heavy]

I think mep made some vaild comments.
You would need to provide a little bit more info, as of what you would like to do.
If I see your vehicle, it looks like a three-wheeler (but maybe I see it wrong from the photo).

I assume (perhaps wrongly), that you are talking about a brake application for the two front wheels.
As mep suggested, the simplest way, would be to use two standard levers/master-cylinders in parallel and just join them mechanical together.

Then you would have one brake disc/lever/master-cylinder per wheel.
You would need twice the force to achieve equal braking at both front wheels, but I´m sure that this is not the main problem.

If you where to built/design your own master-cylinder/lever you could probably achieve a better/ligther system overall.

Are the brakes in your vehicle operated by foot or by hand?

Maybe you can describe/post some photos from the system you currently use.
This would make it easier for us, to give you some ideas/input.

Good luck for your project in any case.

[marcush.]

one idea I would like to float around is:

why not have a pull type master cylinder -this will avoid the problem of sideforce ,buckling of the rod issues and should offer potential in dimensioning.

a balance bar type of connection between the two master cylinders would solve the
the distribution of front rear braking .

Thought about fiddle brakes? (change of direction through applying one brake only?
so you would need two brake levers left and right and a possibility to apply them as a set as a balanced well...Mclaren was using something like that a few years ago.

Drumbrakes have better initial bite than discs.

[flynfrog]

Ive had good luck with this one on solar cars.

make sure you size your cylinder sizes

[Richied76]

I'm an avid downhill mountail bike racer and to be honest the braking force of most systems is so large there would be no reason to upgrade or enlarge any part of it.
If the car your making is a 3 wheeler with 2 at the front. just use brakes on the fronts. Adding a rear will only an weight and complication. AND most systems are routed through parts of the frame (at least on my GT bike) so removal of the rear could be difficult. Two front systems from two cycles will be enough and you wont have to have custom lenght lines made. Also worth noting is that most of the units i've used, ever so slightly drag on the disks. The less resistance the better in your case, not so much mine as gravity is on my side.

I would only use the fronts for braking. Your low down & weight neutral front to back, or there abouts, so i wouldnt bother with the rear. Tie the leavers together and your sorted. Avid ElixerCR's are great, VERY light and very compact. There standard on my bike. Not bad price either. Also get the smallest size disk. power is good and you hardly brake anyway in thoes things. Less spun weight and less overall weight


http://www.chainreactioncycles.com/Models.aspx?

PartnerID=79&ModelID=29728http://www.gtbicycles.com/gbr/bikes/mountain/a ... atte-black

[MadMatt]

Thank you guys already for reading/answering my post !

I'm gonna try to give you more information, but it is at the moment quite difficult since I am in Finland, and I will be back in Switzerland only in 1 month and I have never seen the vehicle closely since 2-3 years.

Yes it is a 3 wheels vehicle (2 at the front and 1 at the back).



The rules says :

- Vehicles must be equipped with two independently activated brakes or braking systems; each syystem comprising of a single command control (lever or foot pedal), command transmission (cables or hoses) and activators (calipers or shoes).
- Indirect and/or electronic braking systems are not permitted.
- One system has to act on the front wheel(s), the other on the rear wheel(s). When braking on two wheels at the front or the rear of the vehicle, two activators (calipers or shoes) have to be used (one on each wheel) commanded by only one command control. In addition, the right and left brakes must be properly balanced. Foot control operation is recommended.
- It must be possible to activate the two braking systems at the same time without taking either hand off the steering system. For single handed steering systems incorporating one braking system, the second system must be foot operated.
- The effectiveness of the two braking devices will be tested during vehicle inspection. The vehicle will be placed on an incline with a 20 percent slope. The brakes will be activated each in turn. Each system alone must keep the vehicle immobile.
- The use of an hydraulically controlled braking system is highly recommended. Cable operated systems are allowed as long as they are effective and pass the brake test.

Braking the rear is okay, but that's for the front I would need ideas. The main thing is that a single lever has to be connected to 2 different calipers which will brake 1 wheel each.

I have to ask the project manager if components can be changed such as brake lever, but I think he first said quickly it was not possible. Will have to investigate why.

I'm also a mtb biker (cross-country) and yes the braking is really huge. I don't know what's the weight on this vehicle but will find out with the project manager. I don't have more details at the moment but I will keep you updated ! For now I'm just taking ideas !

So thanks for posting up ideas, I hope the small bit of development here will help !

[747heavy]

apart from the proposed mountain-bike mastercylinders/levers
and Flynfrogs Kart brake system (which I quite like), you may have a look
at motor cycle master cylinders.
Especially rear ones, as they will be easier to mount/combine two together if you want to use a foot pedal brake.

They are quite light and come in different sizes.
They should cost around 50€, but you may get them cheaper from a wrecker somewhere.
If you want/can spend more money, go and look at parts from race/offroad bikes (KTM/Honda CFR etc).
They will be made from lighter materials (Magnesium etc.), and optimized in design for lightness.

Do your calculations in relation to your brake caliper piston size, the max force and max travel you would like to see/need, and this should give you a master cylinder size(bore). Then you can go and look at something in this range (bore size)
As a rule of thumb a smaller mastercylinder (bore size) = less force needed, but more travel for a given brake line pressure/braking performance.
Larger master cylinder (bore) more force / stiffer pedal feel and less travel.

If you are adventurous and really into weight saving, you can look at some clutch master cylinders, maybe in combination with a mountainbike disc brake.
They are made from plastic, therefore are very light.
But I would not encourage you to go down this route, unless you do some seriuos testing (max pressure/destruction etc.) and do your maths.
I´m not sure what the size(bore) of them are, and if they fall into the interesting range.
But they are neat, and cheap, so depending on your requirements maybe worth a look.

Depending from the speed and the weight of your car/vehicle, I would maybe aim for a moto cross/enduro bike rear brake configuration (disc, caliper,masterscylinder), rather then a mountain bike one.
It maybe is a tad heavier, but will have some safety margin in terms of termal stress/fading, keeping the weight and speed of a motorbike in mind.
A Kart system, as proposed by Flynfog, is also worth a good look - IMHO.

But it´s up to you, do the maths, and then try to find a good&safe solution, it´s part of the challenge.

Good luck

Some photos of the parts I had in mind.





these are BMW clutch mastercylinders (keep in mind that clutch line pressure is much lower then brake line pressure)
Use/try at your own risk !!


http://www.autohausaz.com/bmw-auto-part ... ement.html

[marcush.]

http://www.apracing.com/info/products.a ... _2554_1096

http://www.apracing.com/info/products.a ... _2549_1094



going with MTB style parts is in my view a bit like ultralight aircraft a cloud of doubt ..maybe I´m too suspicious there but an industry calling deep groove ball bearings -industrial grade bearings- is at least something I would not carry over without thorrow consideration...
bikes are in the 9-25KG range + rider ,ok downhill is severe but grip levels are low ...

[Richied76]

Great idea 747. Plus you can put banjo hoses from most with a front mastercylinder nut it it were the correct size. Good pic to because if you turn the whole rear brake assembly 90 degrees anti clockwise its a brake peddal with mastercylinder under foot. I'll look at my bike in the morning and see if the bolt and threads are the same size

[flynfrog]

they have the exact dual brake system for solar cars that's why we went with that MC. Simple to mount low profile already has a splitter.

Word of waring the threads are British pipe thread. Pegasus racing sells fittings

[Richied76]

I dont doubt for one second that the bike rear master is anywhere near as ideal as the MC system but what kind of weight does it have and what how much do they cost? There a nice bit of kit to look at though. And also flyn do they come with compatiable calipers? i may have a project coming up where i need to get hold of some like the ones you recomended. If you have a link to a supplyer you've used i would be greatfull.