Hs3 Hydraulic Brakes and Clutch

[speedfr]

When we brake on a motorcycle, actually every wehicule with liquid brake on disc, we first push the fluid with the lever to move the "fork cylinder" (sorry, i don't have the exact technic word) so it press the pad to the disc. But the disc constantly turn (till you stop  ) and by his movement keeps pushing the pad back so you maintain that force through the pressure you have on the lever. On this system, the pressure is made, the little tiny circuit is filled up, you test with the lever, you have pressure. But if during a lap, you keep pressing, pressing, nothing move, the pressure keeps being directly applied only to the round metallic cap that press on the silicium plate (that catch the pressure by deformation if i understood what i have been reading about it).
So in the Allan system, i think but i might be totally wrong - i just give an idea that i have in my mind - that the pressure will keep going up to a certain level and something is going to leak or break after a lot or maybe not a lot of actionning. As far as i know water is not compressible, what about this DOT fluid ?

[HornetMaX]

Ideally you need a load to resist against, no just a resiviour (like this is)

By presure is a constant, I assume you mean under load. EG say it is the system is at 100 PSI then you pulling on the lever should not increase the presure, it should apply a movment load until there is no more give. Unfortunetly in this siuation that wouldn't be a practical solutuion as it would require a lot of space.

We use the same pricipal in Lifts, systems sit at say 10 bar and starting the pump doesnt actually put any more pressue on the cylinder it just moves oil into the cylinder and such moves the lift car on the rod.

That's not how brake works (can't say for lifts but I trust you).

Lever not pulled, pressure in the main part of the circuit is small (in the reservoir it's just the atm pressure).
Only when you pull it the pressure builds up. The initial part where you actually displace the piston/pad is not very interesting (but you ned some extra pressure for this too, to overcome friction). Once the pad touches the disc, this is where you build up pressure.

[matty0l215]

Yes sorry, like you say. Pulling on the lever would increase the pressure because there is a resistive load.

I should have put it differently. You could use a static load (contstant presure, say to a piston) but theis would then require another mesuring device and would actually be useless in this situation because it wouldn't give the feel of a motorcycle break

Rambeling again, I'll be quite now

[h106frp]

Prressure is constant - just refering to the hose comment. The issue with hoses is not changing pressure but the bulging creating more volume space for the working fluid.

The ratio comment is that correctly primed this system would have virtually no lever movement, we are not (meaningfully) trading displacement for force and would describe it as very 'wooden' in a real scenario.

I did start something using a cheap landrover clutch slave cylinder - a push cylinder acting on a stiff spring that finally became coil bound after a short displacement to simulate initial take up and loading - seemed a reasonable simulation but gave up onn the idea of a fluid system.

Well done to DD, once refined certainly the way to go.

[HornetMaX]

Prressure is constant - just refering to the hose comment. The issue with hoses is not changing pressure but the bulging creating more volume space for the working fluid.

The ratio comment is that correctly primed this system would have virtually no lever movement, we are not (meaningfully) trading displacement for force and would describe it as very 'wooden' in a real scenario.

I did start something using a cheap landrover clutch slave cylinder - a push cylinder acting on a stiff spring that finally became coil bound after a short displacement to simulate initial take up and loading - seemed a reasonable simulation but gave up onn the idea of a fluid system.

But why doing that once you have a real lever and master cylinder ?
Assuming a real caliper + pads+ disc is perfectly "rigid" (i.e. no bulging/leaks), then just put a short hose with a tap on it and it should have the same feeling as a real brake no ?
OK, minus the fading, but everything else should be the same (hose bulging + master cylinder losses). I don't think the actual displacement of brake pads pistons really matters to the feeling.

[uberslug]

Prressure is constant - just refering to the hose comment. The issue with hoses is not changing pressure but the bulging creating more volume space for the working fluid.

The ratio comment is that correctly primed this system would have virtually no lever movement, we are not (meaningfully) trading displacement for force and would describe it as very 'wooden' in a real scenario.

I did start something using a cheap landrover clutch slave cylinder - a push cylinder acting on a stiff spring that finally became coil bound after a short displacement to simulate initial take up and loading - seemed a reasonable simulation but gave up onn the idea of a fluid system.

But why doing that once you have a real lever and master cylinder ?
Assuming a real caliper + pads+ disc is perfectly "rigid" (i.e. no bulging/leaks), then just put a short hose with a tap on it and it should have the same feeling as a real brake no ?
OK, minus the fading, but everything else should be the same (hose bulging + master cylinder losses). I don't think the actual displacement of brake pads pistons really matters to the feeling.

In a properly primed system the initial lever movement takes up the gap between the pad and the disc, which, while small, does require a modest amount of fluid especially on systems whose brake caliper pistons are large or numerous. The amount of lever movement required is inversely proportional to master cylinder piston diameter and there will be minimal change is line pressure as there is very little resistance [a bit of static pressure which would be very difficult to measure]. I am not writing anything new here, just putting other enthusiast's words in a different order.

If the system is dead headed and is completely air free, as DD's seems to be, then one would see an increase in system pressure immediately upon pulling on the lever. In properly primed systems the pressure curve is not at all linear as the gap provides no resistance, the balancing of the fluid load [in the case of multiple caliper pistons of differing diameters] provides an modest load, the compression of the brake pad material provides a large load, and compression of the brake disk provides a tremendous load. Once all gaps have been taken up and all components have completed their limited amount of compression then the system is at its maximum pressure capacity and any increase in braking force is due to friction between the pads and the disk and not the pressure being exerted on the lever. Any additional lever movement beyond the maximum system pressure point just expands the diameter of the brake lines, regardless of brake line material.

[doubledragoncc]

The biggest problem that you guys forget is cost and shipping.

I was lucky to find a DOT 5.1 that is totally NON HAZARDOUS to ship BUT you have to ship with NO air in the system or it can be dangerous.

If it was a complete brake system it costs so much more AND I would then need to think on mounting all the parts and keeping them safe in shipping.

Compromizws must be made. If everyone was rich it would not matter but you have to keep it real to sell it!!!

DD

[HornetMaX]

Once all gaps have been taken up and all components have completed their limited amount of compression then the system is at its maximum pressure capacity and any increase in braking force is due to friction between the pads and the disk and not the pressure being exerted on the lever. Any additional lever movement beyond the maximum system pressure point just expands the diameter of the brake lines, regardless of brake line material.

Hmm, sorry but no. The friction you mention (discs - pads) is proportional to the pressure between the two parts, so any increase on lever pressure will increase breaking force.
The pressure is definitely not constant: that's why when you want to brake more you squeeze the lever more (no matter if it actually moves or not).

Simple proof: put a chair on the floor and push it. Now sit your wifey on the chair and push it. More pressure, more friction, more force.
Don't push the wifey too far though

@ddcc: I'm actually arguing in favor of simpler stuff, just like you did

[uberslug]

Once all gaps have been taken up and all components have completed their limited amount of compression then the system is at its maximum pressure capacity and any increase in braking force is due to friction between the pads and the disk and not the pressure being exerted on the lever. Any additional lever movement beyond the maximum system pressure point just expands the diameter of the brake lines, regardless of brake line material.

Hmm, sorry but no. The friction you mention (discs - pads) is proportional to the pressure between the two parts, so any increase on lever pressure will increase braking force.
The pressure is definitely not constant: that's why when you want to brake more you squeeze the lever more (no matter if it actually moves or not).

Simple proof: put a chair on the floor and push it. Now sit your wifey on the chair and push it. More pressure, more friction, more force.
Don't push the wifey too far though

@ddcc: I'm actually arguing in favor of simpler stuff, just like you did

I agree the amount of friction is proportional to the pressure, however, once the system has reached maximum pressure any additional force on the lever is absorbed by the expansion of the brake lines. In the real world, there is very little braking force to be gained by increasing the pressure on the lever beyond the maximum pressure point of the system. This is the reasoning behind steel braid reinforced versus stock aramid braid brake hoses, less system flex equals more system pressure equals more braking force [to a point].

Pretty much no matter what one uses in a braking system with 'flexible' hoses, the system isn't [in a strict sense] dead headed [technically hard pipe doesn't provide true dead heading if the pressure has no defined limit].

If braking force were merely dependent upon system pressure we would have massively large brake calipers with massively large pistons and very small master cylinder diameters. In addition, levers would be REALLY long with very high pivot ratios. Modern braking systems rely on the friction created when two materials are rubbed against each other for their braking force, not the overall system pressure.

And just so we are comparing apples to apples: In my argument I am defining 'Braking Force' as the drag the braking system introduces to the rotational velocity of the wheel, not the amount of force being exerted upon the brake pad / disk combination.

Yes, simple is better.

[HornetMaX]

I agree the amount of friction is proportional to the pressure, however, once the system has reached maximum pressure any additional force on the lever is absorbed by the expansion of the brake lines.

Ah OK then, it was a bit unclear when you first stated it.

If braking force were merely dependent upon system pressure we would have massively large brake calipers with massively large pistons and very small master cylinder diameters. In addition, levers would be REALLY long with very high pivot ratios.

But that's mostly the case no ? Multi-piston calipers(more practical than one larger piston), braided hoses, small master cylinders, high leverages ... all stuff we have on sports bikes.
Not the long levers of course, for obvious resons

Modern braking systems rely on the friction created when two materials are rubbed against each other for their braking force, not the overall system pressure.

Oh man, you lost me again That (rubbing) friction depends on the pressure.
If it wasn't dependent on the pressure, we wouldn't need braided hoses (just lower the leverage to get a lower max pressure with just as much braking force).

And just so we are comparing apples to apples: In my argument I am defining 'Braking Force' as the drag the braking system introduces to the rotational velocity of the wheel, not the amount of force being exerted upon the brake pad / disk combination.

And what I'm trying to tell you is that the two are proportional
The more you press the pad against the disc, the more drag you get.

[doubledragoncc]

DING DING end of round one................

I love the way you guys really get into it when I dont even have calipers or discs lol.

DING DONG round two lol

DD

[speedfr]

I can't understand or argue correctly with you guys but as an Ingeneer, i did a lot of theory and once in situation, the theory stays a theory, the reality is sometimes way differents.
And my feeling is that the DD system will have problems anyway, as Uberslug seems to says it too.
(my lack of words is horrible, my technical English is so poor i'm censored by my language limit, very frustrating but too bad for me).
found out that what you call caliper is actually what i was calling "fork-cylinder"... very frustrating.

@DD : Can't you ship your systeme without liquid and the client could filled it up by himself no ? (if it's for GOOD reasons that doesn't depend on you but on International Flight Rules, any client will understand)

Edit : Like that ? 

[doubledragoncc]

lol speedfr

Before you all start the next round you should really wait until I finish my testing. I have learnt that sometimes what should not work in theory, can actually work in practice.

It would not be good to ship without filling the system as the customer might not be the kind that knows how to bleed this system to make sure it works, plus it wont matter if I ship the fluid in a container it is still needing to be shipped lol.

DD

[HornetMaX]

Before you all start the next round you should really wait until I finish my testing. I have learnt that sometimes what should not work in theory, can actually work in practice.

Not sure it was clear but my point is/was that what you're building should feel very much like a real brake.
If it has some "dead zone" at the beginning of the lever travel, the rest should be fine.

[speedfr]

@HornetMax :

that's the point, if he uses transductor its to get pressure on the hand as a real brake, so the feeling would be the same.

And i'm glad to see that we agree with DD, theory and practic are oftenly different, it needs to be tested and retested.

"The Bumblebee can't fly, Aeoronautics theory has proven it. But he doesn't know about aeronautics, that's why he is actually flying..."