Back in zee day a coupla rose joints and we used ta be able ta hunker up a coupla 5/8 tin cans in ta an escort. buyin a pedal box!-Ya didn't read moi say dat. Incidentaly use ya comp and google-and look at images of (as suggested) an escort van with a booster/master sitting by the radiator activated by a rod.FACTORY.REMOTED- .
mjde,
May 26, 9:01am
Ok Ok it's a circuit car i'm building. a Porsche 914. I have fitted Nissan s15 front knuckles hubs etc and have gtr skyline discs up front and 4 pot calipers. on the rear there is Subaru rotors and discs and I will probably fit 4 pots there too. The engine ( ls1 turbo intercooled)and subaru 6 speed are in the back that's why i'm thinking I might need 4 pots all round. The floorpan layout is pretty much the same as early vw beetle with bugger all room for a master cylinder other thah the unboosted one mr porsche used and it's a bit inadequate I feel in light of my caliper upgrade. google 914 floor/ brake and see for yourselves
Yes, this was done on some of the Mini racers a few years ago, the Master cylinder had to be single bore however to get round the rules they went to a slave cylinder with a balance bar.
Glynn wouldbe the man ta talk 2- [If ya don't already know glynn!]
snoopy221,
May 26, 10:05am
Personaly also a rod system with a tandem boosted master behind the seat activated from the pedal is within the realms of possibility.
steve312,
May 26, 10:15am
There is absolutely no reason why whay you are suggesting wouldn't work.It does sound a bit like an extra link that could go wrong but it seems far easier to set up than linkages.
I would be going with a 1 - 1 ratio though (ie:3/4" master to a 3/4" slave or whatever size you decide on).This would provide you with the exact same amount of travel at the second master cylinder as you would achieve if it were connected directly to the pedal.The only thing you are going to have to ensure is that there is no flex in any of the mounting points.
It is still going to take a bit of shagging around to get the ratios correct.Bear in mind that the bigger the brake activating master cylinder is, the greater amount of pedal pressure you are going to require to to achieve enough clamping pressure at the calipers to haul the beast up
skin1235,
May 26, 10:43am
been out for tea, 2 issues, volume of fluid to pinch 2 pots each front and possibly twin pots rears - thats issue 1,8 pots swallow a fair bit of fluid - will your remote master be able to deliver 2nd issue - you'll want to be able to double pedal so travel at your actuator master will have to be limited to close to other pedal height, and not be excessive travel the 5/8 to 11/16 isdouble travel for the same inch at the final master - not good - as steve312 suggests 1:1 would be better - 5/8 master to 5/8 slave but I question the need for it at all, a remote booster with a twin system master behind it will work with normal pedal travel ( as long as your twin system master is matched to deliver the fluid demand you'll be creating) read if 8 pots requires even just 25cmm to fully activate is that master able to deliver such before bottoming out - something to check you may also be able to adjust/adapt more vac ( more assist)
on vac boosters - they charge via manifold vac, how much will you have ( throttle full wide doesn't create manifold vac) should you be using a vac pump - either electric or mechanical - back of alt like most diesels use
no expert on brakes etc but your questions intrigue me, and know that if enough ideas get thrown in the pot by enough people you may actually achieve something close to what you want hell even cable from existing pedal to an actuator lever in front of a suitable booster master with a coil spring return will work ( if mounts etc are up to scratch), is sound enough for many clutch system today
mjde,
May 26, 11:00am
Awsome, thanks men for all your input. Yes I see what you mean about the master slave ratio so I will keep it 1:1 then onto the master from there. the mounting setup I made today is very substantial and there's no chance for any flex. the slaves about 40mm away from the dual master connected by a pushrod
skin1235,
May 26, 11:02am
make that pushrod extremely robust, like 5/8 bright steel, there is no way you want that to bend under vital pressure, cos when you're pushing that hard you really need the brakes to continue working
mjde,
May 26, 11:16am
5/8 sure wouldn't bend!
petermcg,
May 26, 11:08pm
I will second that idea
mjde,
May 27, 12:34am
OK men I've an update for you. Been out in the shed and plumbed things up and the results are this for you to ponder. full stroke pedal moves the 1 1/16" dual curciut master cylinder 14.25mm. The calipers have 4 x 40.4mm dia pistons. I know there are are a few very clever engineers out there that will possibly be able to help with the calculations. please
skin1235,
May 27, 12:44am
you want to know how far full piston will move the pots!
mjde,
May 27, 12:52am
Yes please and I forgot to say that obviously there are two calipers per circuit. Really just want to know I wont run out of pedal before the wheels lock up!
skin1235,
May 27, 12:53am
head says one pot 6mm full pedal stroke 4 pots = 1.5mm each
with good rotors that will suffice, slight warp and it's anybodies guess
surprising perhaps but most pots move only a few thou to achieve lockup
skin1235,
May 27, 12:56am
I'm not even sure what the original system needed, doubling pots will halve the effect ( which is why I suggested light truck = larger volume for larger slaves) most twin systems have different volume ( stepped) master pistons = different ratio ofdelivery front and back = bias front/back keep that in mind when it comes to fit rear pots, you may need manul bias valve to get correct braking balance
mjde,
May 27, 1:03am
Looks like I had better go and modify the leverage point on the pedal for a longer stroke then
skin1235,
May 27, 1:05am
1 1/16 master ( 1.06mm) X 14.25 stroke = 8.1cc per stroke 40.4 pot cops 8.1cc moves 6mm 4 pots share it =1.5mm each
and thats just the front system using all the available displaced fluid
you need to be able to measure the displaced volume of both front and back separately
and that will also show you the mechanical bias which you can then calculate the actual bias once you have the size of the rear pots ( I think it works like larger pots = less effect = 50mm rears will not grab as hard as the 40mm fronts with the same delivered volume same pressure
makes ya head spin huh! does mine lol
check anything I say with other sources before committing harikari though, I could be soo far wrong I'm not even in the paddock next door
mjde,
May 27, 1:18am
I just took a look outside and all around and couldn't see you in any of the paddocks "bugger" But that doesn't mean you're wrong. with the dual circuit master, are'nt the front and rears independent and will move the same amount of fluid to each front and rear circuit! there are two reservior feeds. I can use a brake bias valve to lessen the effect to the rears if needed
saki,
May 27, 2:05am
I use .75 master cylinder on princess 4 potters piston diameter 38 mm.
mjde,
May 27, 2:16am
is that unboosted Saki
snoopy221,
May 27, 2:19am
Have ye got a damn stack of nissan! master cyls!
Earlier ya had an inch-now ya gotz an inch and a sixteenth
mjde,
May 27, 2:42am
well spotted snoopy, I looked on the invoice this morning only to discover that instead of it being an inch like the salesman said, it was in fact a 16th bigger. And by the way the dual master is an Isuzu.
bill-robinson,
May 27, 2:50am
I think you should look at the Wilwood reverse pedal box, uses pull cylinders mounted under the feet. Expensive but cheaper than an AP setup. Remember you are moving pressure not volume with brakes and the opposite with a clutch. I have a 5/8 master cylinder working 1 3/8 4 piston calipers and the pedal pad moves about 3/4 inch from rest to full on.
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