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JMortensen

Question about dual master cylinders...

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No by pedal ratio I mean where you put the balance bar. On a car wtih a vacuum booster it needs to go a little higher up the arm. I looked at the tilton pedals and used there leverage ratio when I modded the stock arm (distance from pivot to balance bar and total length of pedal). I have driven a car with the balance bar in the stock location and it requires a lot higher pedal effort to get stopped.

 

Cary

 

At the risk of sounding like a complete idiot, I have to disagree. By lowering the master attachment point, the amount leverage is being decreased exponentially. Was the other car you drove a Z, with the same size masters, etc?

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It's not exponentially decreased. The ratio is explained here. http://www.wilwood.com/Products/005-PedalAssemblies/Pages/techtip/pedaltech.asp What will matter is that the higher the ratio the less throw on the master for a given amount on the pedal. So I guess you have to keep in mind how long the throw on the cylinder is and how long the throw is where you plan to install the pivot.

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At the risk of sounding like a complete idiot, I have to disagree. By lowering the master attachment point, the amount leverage is being decreased exponentially. Was the other car you drove a Z, with the same size masters, etc?

 

I raised them about a half inch. I don't really know why they look so low in the photos.

 

Cary

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It's not exponentially decreased. The ratio is explained here. http://www.wilwood.com/Products/005-PedalAssemblies/Pages/techtip/pedaltech.asp What will matter is that the higher the ratio the less throw on the master for a given amount on the pedal. So I guess you have to keep in mind how long the throw on the cylinder is and how long the throw is where you plan to install the pivot.

 

Ok, exponentially wasn't the right word, but it certainly is multiplied. That link only reinforces my statement. Technically one would want the attachment point as high as the pedal throw will allow, and this will also decrease the amount of pressure needed.

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well i'm giving this one a shot guys. here's a couple pics of the progress Ive made so far. there's a couple reasons i did this. first being that i need more room for how i want to package my turbo/wastegate. second, is that this is going to cost me about the same as restoring the stock system.[new masters/booster, mine were junk] and i've got another pedal box so if i screw up, i'm not ...screwed. to be honest i dont totally understand yet how these are supposed to better for performance braking, so i'll let one of you guys tell me that.

 

oh yeah, and i think they look cool.

 

everything came today. balance bar, remote adjuster, [1] 5/8" master and [1] 3/4" master, all wilwood . here it all is, along with my partly notched pedal box.

Dualmasters1002.jpg

 

close up of the parts.

 

Dualmasters1001.jpg

 

the first thing i did was notch the pedal box, for clearance of the balance bar. i made sure before i cut, that the masters would have enough throw. i still have to do a bit on the inside wall. after notching the pedal box, was do some measuring as to where these things were going to go. here is what i came up with. an interesting thing i found out was that the wilwood masters lined up perfectly in the stock holes for the clutch master cylinder. [is this some kind of industry wide bolt pattern? or are we just lucky?] i guess i'll be picking up another one, just for continuity's sake.

 

dualmastercyllinderpattern.jpg

 

after that was cutting a hole in the pedal to fit the balance bar. this was by far the hardest part, it took about an hour. all i used was a drill and a round file.

 

dualmasterpedal001.jpg

 

close up

 

dualmasterpedal002.jpg

 

not welded yet.

 

so next is cutting off the old front, and making a new one for the masters to go through. i should get to that within a few days...

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The benefit to this over a normal master with a proportioning valve is that this is ACTUALLY proportional and a valve really isn't, so you can get more rear braking (especially at high speeds) with this setup than you can with a traditional prop valve.

 

I've decided that I'm going to do the same. Keep updating as it comes along. You'll probably save me some hassle... :wink:

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did some more work today. got the sleeve for the balance bar welded in, cut up the pedal box some more, and got the replacement face welded partway in. i'm takin a break right now. i'll update some more if i get anything else done tonight.

 

the hole near the weld is for the return spring

 

DualMasterCylinderFab005.jpg

 

DualMasterCylinderFab006.jpg

 

here you can see the clearance with the interior wall. it's fine if i keep the balance bar in the middle, but if i'm going to need to adjust it further that way i'll have to cut out a slot

 

DualMasterCylinderFab007.jpg

 

DualMasterCylinderFab009.jpg

 

DualMasterCylinderFab011.jpg

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Just finished! Kinda. just a few more things to button up.

 

DualMasterCylinderFab012.jpg

 

DualMasterCylinderFab013.jpg

 

DualMasterCylinderFab014.jpg

 

DualMasterCylinderFab015.jpg

 

the only issue now is that the holes in the plate are a little far apart, and they're a LITTLE crooked. not sure how to real with that yet. maybe spacers to push the arms further apart on the balance bar.

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What are the washers supposed to do? From your pics it's not clear what you're trying to do here. You need to clearance the inside of the bolt above and I would recommend adding the lip back in around the firewall mount as it adds stiffness.

 

Cary

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I think he mounted the masters too far apart, so the washers are spacing the black parts (don't know the name of those) so that the rod from them to the masters are straight.

 

Thats exactly right. The balance bar had 1 very thin washer on each side of the middle tube that welds into your pedal. i used some thicker ones to space the black blocks out more so they would line up again. if this ends up not giving me enough adjustment i'll try to replace the main threaded rod with a longer one. i should be able to because the monoball is just held in with jam nuts.

 

i dont see how that would make them work any differently.

 

Adding bracing is one of things i haven't gotten to yet. i was planning on adding the lip back, and triangulating it back to the main body...kinda hard to explain, you'll see.

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I pulled my pedal box out again today and took a look. It appears as the pedal pivot to master cylinder pivot distance is roughly 3.25", and the pedal pivot to the middle of the pad at the bottom is roughly 13.625". So that means the stock pedal has a leverage ratio of 4.19. Not a whole lot of leverage.

 

I see cary talked about moving the pivot up ~.5", and that yeilds a leverage ratio of ~5:1. So I guess I'll follow his lead on this and drill the new pivot hole up about 1/2" inch. I was kind of hoping that the ratio would be closer to 6:1, but I don't think there will be enough pedal stroke if I move the pivot too high.

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OK, I cut the brake side of the pedal box off where it sits against the firewall. Trying to figure out what to do here. I have some .103" plate, and I have some .040 sheetmetal. My instinct is to build the thing with the sheet. I checked the thickness of the original sheet and it was .050, so a bit thicker. I don't have anything that thick, and the .103 is just so much overkill. I really think that the thinner stuff will be OK since this is the part that hits the firewall. Opinions?

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Also, Lunar, I got the Tilton balance bar and it looks like those washers you have are just not necessary. I don't think they'll hurt anything, but they don't really do anything other than perhaps keeping dirt out of the monoball area inside. I think you need to remove the jam nuts on the outer ends of the bar on both ends too. Otherwise they will prevent the balance bar from working.

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thanks, i'll take those jam nuts off then. I was really confused why they were included on the balance bar actually., because it's not like the "black box things" [ i dont know what else to call them] can spin off, because they're attached to the the master cylinders via the rod that threads into them.

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Are the connectors that attach the master to the balance bar (I guess its a clevis?) supposed to be right up against the tube that gets welded into the pedal? It seems like they should be close, but I'm pushing my pedal and the balance bar is pivoting not just left and right, but also up and down. I don't think this would cause any big problems, just doesn't seem like it's right.

 

I was really surprised at how much adjustment the balance bar has! Doesn't take much...

 

Also starting to look at the firewall and wonder what should be done there. My big idea right now is to cut out the area where the stock master bolts up, and make a little plate to fit in there that has the hole pattern for the duals, then weld it right into that little square. It's a bit confusing because there is the level of the masters respective to the pedal, and that height has to be transferred correctly onto the firewall, otherwise it won't all plug together.

 

I suppose the other possibility is to just hack up the firewall so that the masters just sit on the pedal assy and don't touch the firewall, but I'm not so sure I like that idea, especially since I used that .040 sheetmetal...

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I just looked at Cary's again, looks like he used a heavier plate and then cut the hole in the firewall so that he didn't have to make a corresponding plate for it. I think I may take what I have now, use it as a template and do the thing over in that .103" plate. I've done all the hard work, getting all the holes to line up and all of that...

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Are the connectors that attach the master to the balance bar (I guess its a clevis?) supposed to be right up against the tube that gets welded into the pedal?

 

The clevis' need to be straight out from the master cylinders so the pushrods get a nice, straight push. The clevis' can be close to the monoball mounting tube as long as they don't contact it during braking. The biasing action comes from moving the monoball pivot side-to-side within its mounting tube.

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