Vacuum Canisters/Reserviors. Do they work?

I just read through this whole dam thread again trying to figure out what everyone was all wound up about. Nothing here is all that far off.

Eddie: Did you get all your questions answered?

Timm: Is there anything that you need clarification on? Don't be afraid to ask me.

Braking systems are a bit weird. The hydraulics is easy. Brake dynamics can get complicated.

Robert.

---

Robert.

"You are way too normal to be on Rally Anarchy." Eddie Fiorelli.

Thanks Robert, I'll let you know if I have any brake related questions, I think I'm good for now. My brake stuff is coming along pretty well, so far.

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Welcome to the cult of JVL drink the koolaid or be banned.

This reminds me of a conversation I had Tuesday night at the bar.
Mark and I had just got there and were waiting on Bill Lockwood, Matthew Johnson, Mitch Williams, and Steve Bis to join us. Had just got off the phone with Steve and they were out in his rally car doing some road tuning and 'theorizing on restrictor design.' I was talking about how it was a waste of time and how WRC teams that had way smarter people and way more budget had already spent plenty of time on this subject and you may as well just copy what they are doing as you are just wasting time for something that isn't going to have an improvement.
The other argument is that time and labor are free so you may as well. Personally my time and labor are never free and I'd rather go bowling than work on my car for hours for little or no gain. Or better yet, do something that generates or could generate income instead.

---

Grant Hughes

starion887 Wrote:
-------------------------------------------------------
>
> This thread started with the idea of avoiding a
> 'wooden pedal' effect. Where is it heading now?
>


Jeez, I go away for the weekend, come back and its a mad house in here! Totally anarchy.

Here's where the story went. I asked about canisters and John mentioned dual MCs. I read up on those and saw that they effectively can increase your brake output in addition to the biasing. Thus, when you are run them without vacuum assist the effort is not as great as a stock setup with a plugged vac line.

I then read the other thread here about VW knuckles and thought to myself that I hadn't even thought about the caliper's role in this story. The VW options I'm most familiar are the 9.4, 10.1, or 11" front setups. But never really talked to anyone about dual/quad pot setups. So, I was looking for info on where the conventional thinking is in regards to single/dual/quad piston calipers, that is, what's legit and whats just for show. I understand that more pots improve how the caliper load is distributed over the pad, but, can they also effectively increase the mechanical gain of the brake system.

Going on what everyone else is doing I'm inclined to "guess" that the sweet spot for the mk2 VW is a dual MC setup, no vac assist, stiffen the filewall (which goes for any setup), and then go with the 11" Corrado big brakes, mk3 or G60 knuckles, and Porterfield R4 pads. But that's based on me putting together peicemeal observations and without much experience on various platforms. Its the multi-platform experience that I'm looking for here.

Now I need to re-read this thread again to attempt to separate the wheat from the chaff.








Edited 1 time(s). Last edit at 04/13/2009 06:08PM by Eddie Fiorelli.

Just ignore anything I said, and anything John says to me, and you should be good. But dont ignore this post though, or you wont know what to ignore!

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Welcome to the cult of JVL drink the koolaid or be banned.

Eddie Fiorelli Wrote:
-------------------------------------------------------
>
> Here's where the story went. I asked about
> canisters and John mentioned dual MCs. I read up
> on those and saw that they effectively can
> increase your brake output in addition to the
> biasing. Thus, when you are run them without
> vacuum assist the effort is not as great as a
> stock setup with a plugged vac line.
>

Chaff?!?! Here ?!!?

Be sure you understand that the side-by-side dual MC setup only can provide more braking pressure IF the diameters of the side-by-side MC pistons are notably larger (EDIT: Ooops I meant to say SMALLER) than the diameter of the piston bore of the standard factory inline dual master cylinder.

If the piston sizes are the same between the 2 set-ups (side-by-side vs. inline dual MC's), the side-by-side MC's will provide HALF of the brake line pressure, since the pedal force is split between the 2 individual side-by-side MC's. (Assuming the pedal bar is set for a 50/50 split of MC pressures, and both MC's are the same size.) The pedal travel on the side-by-side MC set will be approximately half also.

Regards,
Mark B.



Edited 1 time(s). Last edit at 04/14/2009 09:03AM by starion887.

starion887 Wrote:
-------------------------------------------------------
>
> Chaff?!?! Here ?!!?
>
> Be sure you understand that the side-by-side dual
> MC setup only can provide more braking pressure IF
> the diameters of the side-by-side MC pistons are
> notably larger than the diameter of the piston
> bore of the standard factory inline dual master
> cylinder.
>
> If the piston sizes are the same between the 2
> set-ups (side-by-side vs. inline dual MC's), the
> side-by-side MC's will provide HALF of the brake
> line pressure, since the pedal force is split
> between the 2 individual side-by-side MC's.
> (Assuming the pedal bar is set for a 50/50 split
> of MC pressures, and both MC's are the same size.)

Huh??? Howzat? Why is split.
Say 10kg force input. master 1 sees 10kg, and master 2 sees 10kg.
How could it be otherwise?


Also experience shows that the masters used a invariably smaller than stock tandem booster assisted masters.

Please to be 'splaing....
> The pedal travel on the side-by-side MC set will
> be approximately half also.
>
> Regards,
> Mark B.

---

John Vanlandingham
Sleezattle, WA, USA

Vive le Prole-le-ralliat

www.rallyrace.net/jvab
CALL +1 206 431-9696
Remember! Pacific Standard Time
is 3 hours behind Eastern Standard Time.

john vanlandingham Wrote:
-------------------------------------------------------

> Huh??? Howzat? Why is split.
> Say 10kg force input. master 1 sees 10kg, and
> master 2 sees 10kg.
> How could it be otherwise?
> Regards,
>
> John Vanlandingham
> Sleezattle, WA, USA
>
> Vive le Prole-le-ralliat
>
> www.jvab.f4.ca


I'm thinking its because the cylinders are in a parallel configuration but I'll let Mark do the s'plainin.

Eddie Fiorelli Wrote:
-------------------------------------------------------
> john vanlandingham Wrote:
> --------------------------------------------------
> -----
>
> > Huh??? Howzat? Why is split.
> > Say 10kg force input. master 1 sees 10kg,
> and
> > master 2 sees 10kg.
> > How could it be otherwise?
> > Regards,
> >
> > John Vanlandingham
> > Sleezattle, WA, USA
> >
> > Vive le Prole-le-ralliat
> >
> > www.jvab.f4.ca
>
>
> I'm thinking its because the cylinders are in a
> parallel configuration but I'll let Mark do the
> s'plainin.


I was on the phone with "Service Nazi" Robert (Rallymech) and he was in strong agreement. 10 kg input on a shaft inline with the pedals or if there was a square bar welded fixed to the pedal with one rod say 3" from pedal centerline there'd still be 10kg force. If there were 2 shafts forward, there's be 10 kg at the end of both the shafts....

(By the way, this is a good example of why having the answer already done 10,000 times is good. Even if there is a mistake in reasoning, ways of expressing a problem, ways of understanding/comprehension, if you DO the right thing, it works as it should---understanding is a luxury.
Simply put for cars in the Escort/Corolla/Golf size and weight there is already published sized that worked for guys faster than us and worked well. We can look on Ford and VW set up sheets and see pretty typically Front mater 0.7", rear 0.7, or 0.75. Front caliper 4 x 1.5", rear 2 x 2" (reduced with limiter that folks always call "proportiong valve". Cars the size of Xratties, Le-gassy, Evo-bitchi, front 2 x 1.5 and 2 x 1.625 progressive or simply 4 x 1.625 and 4 x 1.25 rear. Master front 0.7 or 0.810, rear master 0.75" This is gravel.
This is so consistent i made one of my infamous "I bet ya a nickel" bets to Dave Clark once when he had a Suby rear caliper what the size was since he didn't know off the top of his head. I bet it was 2 x 1.5 or 38mm.
Wone the bet. Then knowing that I bet another nickel that the fronts would be the progressive 2 x 1.5 and 2 x 1.625..
Dave declined to take the bet----wise man, cause the guess was right.

>
>
>

---

John Vanlandingham
Sleezattle, WA, USA

Vive le Prole-le-ralliat

www.rallyrace.net/jvab
CALL +1 206 431-9696
Remember! Pacific Standard Time
is 3 hours behind Eastern Standard Time.

And I just edited my BIG posting error in saying the side-by-side cylilnders need to be lareger...noooo they need to be SMALLER to create more line pressure. That applies for any MC. Funny what pops into your head in the middle of the night.....

OK, on the side-by-side pressures: the pedel bar is a beam with foot pedal pressure near the center and supported at the 2 ends be opposite forces in the MC's. The total force on the beam from the pedal side has to be equal to the total force from the MCs' side or it moves, I.e., once you have your foot down, the total force from the 2 cylinders has to equal the force from you foot. This means the forces are split in some proportion between the 2 cylinders. If the balance point is in the middle (and all else is equal) then the force are slplit 50/50 between the 2 cylinders: 10 kg from the pedal results in 5 kg on each MC. And thus versus a dual in-line MC, half the line pressure results for a given diameter of MC.

You get approximaately 1/2 the pedal motion since each cylinder is only feeding fluid to half the system. But, ultimately you don't want hlef the line pressure, so you will probably put in cylinders small enough to regain some or all of the hydraulic line pressure and thus increase the travel close to where you were before.

In the dual inline MC, let's assume the MC bore is constant throughout for both pistons which is pretty often the case. The pedal pressure is directly applied to MC piston 1. This generates a certain amount of line pressure in the #1 piston's chamber and the associated half of the brake system. That pressure is also exerted by on the #2 piston direcly behind it in the bore and separated by a spring. The #2 piston has to move until the pressure behind it (feeding the second half of the brake system) equals the pressure being exerted upon it by the #1 piston; otherwise the #2 piston will keep moving until this equlibrium is reached. So, in this case, the pedal pressure essentially acts equally on both pistons and on both halves of the system.

This has to be true per the axiom about the relation between cylinder diameter, fluid movement, and the assocatd pedal movement needed, and rationally the pedal travel in this case should be 2x. To check this, say the fluid dispaced in each system half is 10cc for argument's sake. Piston 2 moves to displace 10cc of fluid. Piston 1 moves to displace 10cc of fluid into its assocated line PLUS 10 more cc to fill the fluid space in front of piston 2 created when piston 2 moved. So this checks out.

And I'll correct one thing for Eddie that is my mistake from an earlier post: With the side-by-side MC's, If you work to get line pressures equal to what you had before swapping from dual in-pine to side-byside MC's, then pedal movement will only be slightly different than with a boosted inline MC.

And, if you have not done so already, have you thought about replacing all your stock rubber brake lines with braded Teflon lines as a first step? Rubber lines have a finite amount of expansion that is greater than teflon lines, This expansion causes extra fluid and pedal movement and also absorbs a bit of the force being exerted. Using thes will really stiffen up the brake system make it easier to appy and modulate, and shorten pedal travel a bit.

And John, I half agree and half disagree. If you want to save time, yes using the tried and true will get you there; I never have desinged a camshaft and don't intend to! But, it's like when I learned to tune Webers (a bit); I started with the book setup for the car in question. That got it basically running, but it had stumbles and lean spots. I did not know where to turn. Once I read up on them some, I got a basic understanding on where to aim some efforts to remedy the problems. AND then when I asked someone who knew how all the parts really worked, he added to my framework of understanding and really got me zeroed in on the emulsion tubes that I should try. He could do this because HE UNDERSTOOD THE THEORY AND REASONS BEHUND ALL THE WEBER BITS AND PIECES.

So, IMHO copying gets you so far, Understanding enbles one to handles things mroe and better when the pat solution does not work out quite as planned.

Regards,
Mark B.

Well I got to try out the Summit $35 canister at Idaho for a couple stages and I think it worked out really well. The brakes were consistent the whole time, even on the up hill stage 2 where we were pinned on the throttle much of the time. I wish I had longer time to evaluate them before tagging that tree but for the short time I ran with it I think the canister was a success.

-e

Wow a lot of confusion going on. But the truth is that real race cars all use tandem MC's with balance bar bias adjustment. But at the same time, setup geometry in the pedal box is the most miss-understood concept and where 99% of all brake problems come from at the track.

So keep it simple and follow John's directions or just leave the stock stuff on there like the Gr N guys and they dont run boosters either. So start your squat routine at the gym.

Eddie Fiorelli Wrote:
-------------------------------------------------------
> john vanlandingham Wrote:
> --------------------------------------------------
> -----
>
> > Huh??? Howzat? Why is split.
> > Say 10kg force input. master 1 sees 10kg,
> and
> > master 2 sees 10kg.
> > How could it be otherwise?
> > Regards,
> >
> > John Vanlandingham
> > Sleezattle, WA, USA
> >
> > Vive le Prole-le-ralliat
> >
> > www.jvab.f4.ca
>

If 4 pallbearers are holding a 400-pound casket with a dead fatman in it, each of them only has to hold up 100 pounds of fatman and wood. If it were any other way, they wouldn't need four of them.

The master cylinders are the pallbearers.

The crossbar is the casket.

Your foot is gravity.

Make sense now?

-Dave

eyesoreracing Wrote:
-------------------------------------------------------
> Eddie Fiorelli Wrote:
> --------------------------------------------------
> -----
> > john vanlandingham Wrote:
> >
> --------------------------------------------------
>
> > -----
> >
> > > Huh??? Howzat? Why is split.
> > > Say 10kg force input. master 1 sees
> 10kg,
> > and
> > > master 2 sees 10kg.
> > > How could it be otherwise?
> > > Regards,
> > >
> > > John Vanlandingham
> > > Sleezattle, WA, USA
> > >
> > > Vive le Prole-le-ralliat
> > >
> > > www.jvab.f4.ca
> >
>
> If 4 pallbearers are holding a 400-pound casket
> with a dead fatman in it, each of them only has to
> hold up 100 pounds of fatman and wood. If it were
> any other way, they wouldn't need four of them.
>
> The master cylinders are the pallbearers.
>
> The crossbar is the casket.
>
> Your foot is gravity.
>
> Make sense now?
>
> -Dave
>


I have to push a dead POS Nissan. It weighs 2450 lbs, I weigh 200.
I push X hard using one hand.
Or I push X hard using two hands spaced about shoulder width apart....

It weighs what it weighs and I weigh what I weigh and can only exert X force even if I pushed with my rawk hahd cawk and balls*

Posing made up examples which shift substantially the whole notion being examined rarely elucidates the problem.




Famous local Craigslist reference--ask Dave Clark.

---

John Vanlandingham
Sleezattle, WA, USA

Vive le Prole-le-ralliat

www.rallyrace.net/jvab
CALL +1 206 431-9696
Remember! Pacific Standard Time
is 3 hours behind Eastern Standard Time.

Push with one hand and you make a big dent in the trunklid. Push with 2 hands and you make 2 dents, each half as big.

If examples don't clarify things for you, go back and read Mark B's last post where he essentially describes a free-body diagram. Total force from the master cylinders has to equal total force from your foot, otherwise your foot would move.

-Dave