Combined braking system using hydraulic bike brakes

wrightguy

Hello guys,

I am currently undertaking a project where I am using bike brakes on a small race car. I have a hydraulic disc brake on each of the front wheels but I need a method of applying both front brakes while pulling only one lever.

Is it possible to join hydraulic brake pipe lines together with a fitting so that I can actuate both brakes (would require more force) or is that out of the question.

I am also open to any other methods you can suggest.

Thanks for your help.

lennymc

would you not be better off using a motorbike set up, i wouldnt imagine that bike brakes would be up to stopping a small race car, and you could buy a complete front brake system with two calipers and matching master cyclinder.

Lumen

Hygia Multi?

http://www.hygia.com.tw/prod-brake01-4.html

Or some other system designed for trikes.

Alek

Hygia Multi?

Read this first:

http://endless-sphere.com/forums/viewtopic.php?f=3&t=54119

Lumen

I'm not sure a bike brake calliper is going to be able to handle the heat dissipation requirements of a racecar, even a very light one.

I used to own a <400kg race car and it would have murdered a set of bike brakes in the first couple of corners.

Alek

I've been touring with 80kg of stuff (180kg with me) in Spain recently and went halfway through a set of resin disc brake pads on one 10km descent, just slowing... Rotor must have been glowing, its blueish now here and there. The brake hasn't stopped working though!

I have used the rear only. If i was alternating with the front, I guess there would be no problem.

With a caliper for each wheel, 203mm rotors and very lightweight design I believe it may be possible to have it working reliably. The problem may be how to equalise the braking power?

lennymc

I wouldn't like to try stopping 400+kg from any kind of speed. The pads and disks are simply not designed to deal with that kind of repeated stopping.

I had a 60 kg track car, standard calipers but uprated lines, disks, pads and fluid. Brake fade was still a problem after a number of hard stops.

Lumen

lennymc wrote: »

I had a 60 kg track car, standard calipers but uprated lines, disks, pads and fluid. Brake fade was still a problem after a number of hard stops.

60kg?

lennymc

Lumen wrote: »

60kg?

yeah. *



*Not really. - it was of course 600 kg. stripped out fiat cinquecento with about 65 hp.

wrightguy

Guys,

I probably should have mentioned the car we are discussing here is an ultra fuel efficient vehicle and the completing the 'race' is only half the scenario. Myself and my team are competing against other teams to see how can travel the length of the race using the least amount of fuel (petrol, diesel, hydrogen etc)

The top speeds the car will go are only 20-30 mph and the brakes are only a safety feature and will be used as little as possible i.e. braking is wasting fuel. The brakes will suffice for the car's weight (including driver), I am sure of that.

I just wanted to know is it possible to link two hydraulic brake lines so let's stay on topic here.

Thanks.

Lumen

Just use cable-operated brakes then?

If you absolutely must use hydro calipers you can get a cable-hydraulic conversion system.

lennymc

If they are going to be used very little why not go with a single disk on the rear, or non hydraulic disks. They would be a bit lighter.

Alek

I just wanted to know is it possible to link two hydraulic brake lines so let's stay on topic here.

Yes.

wrightguy

Cable brakes are risky and trying to balance cable brakes on two front wheels would be bit of a nightmare.

This car's weight will be approx. 100 kg and both the front braking system and rear braking system EACH must hold this vehicle on a significant incline to be deemed safe to race - if front holds and rear doesn't during this pre-race inspection, you won't get to race. Hydraulic is tried and tested while cable has failed before on this test, with lighter vehicles

Has anyone ever heard of hydraulic brake lines joined together before? I'm pretty sure it's a matter of applying a fitting to it but wanted clarification on this.

Peter T

You could join the lines no problem but you might not get enough pressure from the leaver.

Mefistofelino

Splitting the hydraulic line to feed two calipers isn't a problem. However a bicycle brake lever won't displace enough hydraulic fluid to actuate two calipers through their full travel. You might need to consider a motorbike lever with a larger master cylinder.

Is this for the Shell Eco-Marathon?

wrightguy

Mefistofelino wrote: »

Splitting the hydraulic line to feed two calipers isn't a problem. However a bicycle brake lever won't displace enough hydraulic fluid to actuate two calipers through their full travel. You might need to consider a motorbike lever with a larger master cylinder.

Is this for the Shell Eco-Marathon?

Thanks for your reply. Are you sure? I have just been talking to someone who did this using a banjo coupling and the master cylinder could handle two callipers. Might possibly have been a high performing brake set for mountain bike racing under high loads and high friction tyres.

Yes it is, you follow the event?

Keep_Her_Lit

wrightguy wrote: »

Thanks for your reply. Are you sure? I have just been talking to someone who did this using a banjo coupling and the master cylinder could handle two callipers.

The previous poster makes a valid point. A brake lever designed to operate a single caliper will, when pulled through a normal amount of travel, displace enough fluid to bring the pads into contact with the disc. At that point, the lever firms up and additional lever pressure gives the desired braking modulation.

If you simply "T" the brake hose into a second caliper of the same type, then it will require double the lever travel to bring both sets of pads into contact with their respective discs. No useful braking force will be generated until that point is reached. The risk is that the lever will be back to bars before you reach that point.

Daroxtar

Isn't there a combination cable/hydraulic system where the cable runs from the lever to the piston which contains hydraulic fluid? You wouldn't be relying on the lever generating pressure on its own reservoir. Could that work better or would splitting the cable be another engineering problem ?

wrightguy

Keep_Her_Lit wrote: »

The previous poster makes a valid point. A brake lever designed to operate a single caliper will, when pulled through a normal amount of travel, displace enough fluid to bring the pads into contact with the disc. At that point, the lever firms up and additional lever pressure gives the desired braking modulation.

If you simply "T" the brake hose into a second caliper of the same type, then it will require double the lever travel to bring both sets of pads into contact with their respective discs. No useful braking force will be generated until that point is reached. The risk is that the lever will be back to bars before you reach that point.

I agree totally, it will require twice the lever travel and that's assuming the coupling is 100% efficient. However if the brakes are of 'high performance' standard they should hold out - they're also over designed as a factor of safety.

I won't know for sure until we actually test it.

Thanks very much for your reply.

wrightguy

Keep_Her_Lit wrote: »

The previous poster makes a valid point. A brake lever designed to operate a single caliper will, when pulled through a normal amount of travel, displace enough fluid to bring the pads into contact with the disc. At that point, the lever firms up and additional lever pressure gives the desired braking modulation.

If you simply "T" the brake hose into a second caliper of the same type, then it will require double the lever travel to bring both sets of pads into contact with their respective discs. No useful braking force will be generated until that point is reached. The risk is that the lever will be back to bars before you reach that point.

You can also adjust the pads so that the feed rate of the lever corresponds to a greater movement of the pads which would help.

wrightguy

Daroxtar wrote: »

Isn't there a combination cable/hydraulic system where the cable runs from the lever to the piston which contains hydraulic fluid? You wouldn't be relying on the lever generating pressure on its own reservoir. Could that work better or would splitting the cable be another engineering problem ?

I'm not sure what you mean exactly. Cable brakes involve 'pulling' the pads together while hydraulic involves pushing a piston to increase the fluid pressure therefore forcing the pads together. Yes, when you pull the lever the piston is pushed but the lever is still applying the force.

And yes, separating cables would be overly complicated and is not 'fool proof'.

Thanks for your post.

DubVelo

Lots of motorcycles have dual front discs and calipers running off a single master cylinder, there is no problem with the idea.

I agree with the previous poster that you likely won't have enough pressure in your system. Why not try a master cylinder & lever from a scooter or small motorcycle?

Good luck!

Daroxtar

On my bike with hydraulic brakes the brake lever houses a reservoir and the fluid is compressed there by the lever. By my understanding in the combined system the lever is a standard brake lever which pulls a cable. The cable runs to the caliper which has its own reservoir in the caliper body and the compression takes place there . Here, you'll probably get more info out of this
http://road.cc/content/review/85499-trp-hyrd-mechanical-interface-hydraulic-disc-brakes

wrightguy

Daroxtar wrote: »

On my bike with hydraulic brakes the brake lever houses a reservoir and the fluid is compressed there by the lever. By my understanding in the combined system the lever is a standard brake lever which pulls a cable. The cable runs to the caliper which has its own reservoir in the caliper body and the compression takes place there .

Are you suggesting that you split that cable and send it to both calipers? If you are then this would be very difficult as you would have to balance both cables correctly and it could loosen if not done well.


I have a feeling those brakes that have the master cylinder on the caliper itself instead of the handlebar may be more expensive but it's a cool idea.

Thanks for your help.

Alek

I have HY/RD on the front. They're nowhere near as powerful as they should be for your project - barely adequate for a touring bike. Normal MTB hydraulics are much more effective.

gctest50

wrightguy wrote: »

Hello guys,

I am currently undertaking a project where I am using bike brakes on a small race car. I have a hydraulic disc brake on each of the front wheels but I need a method of applying both front brakes while pulling only one lever.
....

You could use two master cylinders and put a balance bar between them :

this sort of idea :



/ other random thoughts on it :

don't use an O-ring chain
don't put extra seals on the wheels
"high speed" bearings are a bit more "free running" - test them against ceramic bearings
if it has chain drive - don't go too small with the front sprocket - dont use idlers
try using dry lubes on the chain - see which is best


this yoke can do 240 km/h with only 50cc engine, sort of the same game - waste as little power as possible :

https://www.youtube.com/watch?v=mYINrhTNiyM

krissovo

If its for safety only would a brake on the transmission/axle be an option? Less components and a single caliper front/rear rather than each side. Otherwise a simple couple could be manufactured at home.

Eamonnator

I remember, in about 1998, an Irish DownHiller, racing on a bike, that had 2 disc brakes at the front, used in conjunction with 1 brake lever.
i can't remember the manufacturer.

deandean

OP I suggest you stick to standard component as much as possible.

So, buy two standard MTB front brakes, such as

http://www.chainreactioncycles.com/ie/en/shimano-xt-m785-disc-brake/rp-prod67208
(pick the tube length you require)
and
http://www.chainreactioncycles.com/ie/en/shimano-xt-saint-rt86-ice-tech-6-bolt-disc-rotor/rp-prod67197

Next, presuming you will be working the brake with your foot, make up a mounting so the two brake levers are side-by-side, horizontally. You need to keep the levers horizontal so that the hydraulic fluid reservoirs remains more or less upright, this is the way they are designed.

Next make up a bracket that goes between the two levers. Attach a foot-pedal pedal onto that bracket, and away you go. When you press the foot pedal it's just like pulling both brake levers on the handlebars.

Some microlight aircraft use MTB disc brakes, but each side remains independent to assist the pilot in steering at low speeds.

Best of luck!

wrightguy

deandean wrote: »

OP I suggest you stick to standard component as much as possible.

So, buy two standard MTB front brakes, such as

Next, presuming you will be working the brake with your foot, make up a mounting so the two brake levers are side-by-side, horizontally. You need to keep the levers horizontal so that the hydraulic fluid reservoirs remains more or less upright, this is the way they are designed.

Next make up a bracket that goes between the two levers. Attach a foot-pedal pedal onto that bracket, and away you go. When you press the foot pedal it's just like pulling both brake levers on the handlebars.

Some microlight aircraft use MTB disc brakes, but each side remains independent to assist the pilot in steering at low speeds.

Best of luck!

Sounds good, thanks for the help. Chainreactioncycles.com is a great website!