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Dual Master Mock-Up

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martx-5

martx-5

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Well, I finally got the dual master brake cylinder mocked up for the TR3 resto. Revington gets a ton of money (about $1400 at current exchange rates) for their system. You also have to use a TR4 pedal assembly, and you have to widen the hole in the firewall to accept the three master cylinder assembly. After playing around with this for about a month, I discovered that I didn't need to widen the firewall aperture if I used three Girling remote reservoir masters. I also noticed that is was possible to use the original TR3 pedal assembly (the TR4 assembly has the connectors to the master's wider apart). One of the big problems was the wiper motor. It is right next to the master cylinder box. I didn't want to move anything, and I didn't want to do anything that wasn't easily reversible back to original.

After several master box mock-ups with the help of Tony at RATCO it looks like I've got a go situation. It's possible to use the original TR3 tin can reservoir. I've got them set up for the front and rear master's...but, I've got to get rid of that hose clamp. I need to use someting more like the original on there. The plastic third clutch reservoir...well, maybe I should just go to three plastic reservoirs.

Anyway, I'd like comments...good and bad. This could also be done alot easier on the TR4. I'll probably be mocking up a system for that with Tony in the near future.
 
How come two of the pictures show up in the thread, and the first one you have to click on to see??
 
Excuse me for bieng so dense but ... why would you need three master cylinders?
 
Art-

That looks great, as a TR4 owner I hope you let us know the various bits you are using. I would like a dual system and I thought about Revington's kit but the price is hard to swallow. I've contemplated the TR6 type arrangement but didn't want to do the bulkhead modifications.

Are you intending to add any metering/proportioning valve to the system? I thought Neil's setup used different m/c's for front/rear balance but that may be incorrect.

Where'd you buy the balance bar?

Randy
65 TR4
 
Looks good, Art !

I take it there wasn't room for all 3 MCs back inside the box in the body ? It looks like you've moved them forward, then shortened the clutch pushrod. Or was that just so the brake pushrods didn't have to be longer (for the extension to the balance bar) ?

No concerns over that right-angle joint on the top of the brake pedal ? Awful lot of force at that point during a panic stop; I was thinking more along the lines of a billet piece to straddle both the pedal end and the balance bar. The clutch involves a lot less force, so it can be run around corners if need be.

The first photo was slightly larger (didn't compress as well, perhaps) so the web site displays it as a link.

Kerry, the idea is to install 'split' brakes so that a single hydraulic leak doesn't leave you without hydraulic brakes. Using a pair of single-circuit masters is an alternative to using one of the more complicated dual-circuit masters used on later Triumphs (which also don't fit well in the space available). Although, I must admit there is a Spit master in my parts bin waiting for me to figure out how to use it /bcforum/images/%%GRAEMLIN_URL%%/grin.gif (probably by adapting it for a remote reservoir).

BTW, the Stag uses a metal remote reservoir for the clutch ... might look more at home especially if you paint it black. It's also not very big (clutches don't need as much as disc brakes).
 
I like it and look forward to the finished product. Sure does take a lot of time to work all these little things out, makes you wonder why they didn't give use this from the factory with all the design people getting paid the big bucks. I will be starting on a 3B for a friend in about six months, hope I can talk him into this setup.

Wayne
 
trrdster2000 said:
I like it and look forward to the finished product. Sure does take a lot of time to work all these little things out, makes you wonder why they didn't give use this from the factory with all the design people getting paid the big bucks. ...
Click to expand...
That's simple enough: back then, virtually NO cars had dual braking systems. I vaguely remember that American Motors was the first company in the US to feature them on their cars, several years before the Federal standard required same (1968 model year, IIRC).

Besides, a TR2/3 with a well-adjusted handbrake has a very capable "backup" braking system!
 
TR3driver said:
Looks good, Art !

I take it there wasn't room for all 3 MCs back inside the box in the body ? It looks like you've moved them forward, then shortened the clutch pushrod. Or was that just so the brake pushrods didn't have to be longer (for the extension to the balance bar) ?

No concerns over that right-angle joint on the top of the brake pedal ? Awful lot of force at that point during a panic stop; I was thinking more along the lines of a billet piece to straddle both the pedal end and the balance bar. The clutch involves a lot less force, so it can be run around corners if need be.

The first photo was slightly larger (didn't compress as well, perhaps) so the web site displays it as a link.

Kerry, the idea is to install 'split' brakes so that a single hydraulic leak doesn't leave you without hydraulic brakes. Using a pair of single-circuit masters is an alternative to using one of the more complicated dual-circuit masters used on later Triumphs (which also don't fit well in the space available). Although, I must admit there is a Spit master in my parts bin waiting for me to figure out how to use it /bcforum/images/%%GRAEMLIN_URL%%/grin.gif (probably by adapting it for a remote reservoir).

BTW, the Stag uses a metal remote reservoir for the clutch ... might look more at home especially if you paint it black. It's also not very big (clutches don't need as much as disc brakes).
Click to expand...
I kind of figured that might be the reason {only logical} But then one never really knows for sure without asking.
 
Andrew Mace said:
Besides, a TR2/3 with a well-adjusted handbrake has a very capable "backup" braking system!
Click to expand...
Certainly better than nothing, but you can slide an amazing distance with the rear wheels locked.

Or, if you're like me, neglect to replace the broken cable and then wish you had once the hydraulics fail !
 
I have been thinking about dual brakes systems for a while also. Mostly because I have to replace the piping on my car at some time in the near future. It seems to me that it would be much easier to use a cylinder like this.
https://www.wilwood.com/Products/006-MasterCylinders/009-ATCMC/index.asp

it is available with an appropriate bore, and would only require a tiny modification to the mounting bracket.

Incidentally, it would be worth looking into looking into using Wilwood or other brake suppliers in any case.
I see no reason why this
https://www.wilwood.com/Products/006-MasterCylinders/002-CRMC/index.asp
could not be used as a direct replacement for the Girling masters on many of our cars. There are all sorts of different configurations (for the reservoir), and they are available in a wide variety of bore sizes. Since the clevis is screwed on it adds the option of adjusting the brake system to eliminate a bit of excess travel also. Summit racing has pages of different master cylinders (including these and similar from other companies) The best thing is that they are significantly cheaper than the Girling reproductions. (single circuits ~$60)


Art, two questions
1. how are you planning on plumbing the system? front / back, Diagonal? I believe that most modern cars use diagonal, but I could take a look in a Bosch auto systems reference manual we have at work. It gives a rather in depth explanation of the +/- of all the various configurations.

2. are you putting some sort of warning system in like the PWDA switch? No mater how you plumb the system, total instantaneous failure is rare, rather there would more likely be at least a tiny leak which would set of an alarm long before the pipes would actually fail. Panic braking with only 2/4 brakes is still likely to lead to locking up wheels / potential loss of control.
 
TR3driver said:
Looks good, Art !

I take it there wasn't room for all 3 MCs back inside the box in the body ? It looks like you've moved them forward, then shortened the clutch pushrod. Or was that just so the brake pushrods didn't have to be longer (for the extension to the balance bar) ?

No concerns over that right-angle joint on the top of the brake pedal ? Awful lot of force at that point during a panic stop; I was thinking more along the lines of a billet piece to straddle both the pedal end and the balance bar. The clutch involves a lot less force, so it can be run around corners if need be.


BTW, the Stag uses a metal remote reservoir for the clutch ... might look more at home especially if you paint it black. It's also not very big (clutches don't need as much as disc brakes).
Click to expand...

Actually, The master's are inside the pocket by about an inch or so. I basically started out by using pictures of the Revington set-up. They have the master's moved forward also. Mine are about two inches forward of the original position.

Randall, there is some concern about the right angle set-up on the brakes. That's probably one of the reasons Revington uses the TR4 pedals. They are set wider right on the brakes, and wider left on clutch. This puts the brake pedal acuator in a direct line with the middle of the bias bar. I will most likely make up an offset billet piece to stradle the pedal. If that doesn't work out, then I may be forced to use a TR4 pedal. I'll also have to look for that Stag reservoir. It sounds like it be more fitting.

Also, I'll be running the system front to rear. I don't think there will be a necessity for a warning...you'll know if you lose fluid in one of the systems when the pedal goes half way to the floor.

BTW, there is a Willwood tandem master that will mount up to the original TR3 box. There are two problems however. One is it's length...too long to fit in the recess, and the other is that the outlets come out the bottom of the master...not enough room for the hydralic lines. I would have liked to go that way, but it wasn't in the cards.
 
TR4nut said:
Art-

Are you intending to add any metering/proportioning valve to the system? I thought Neil's setup used different m/c's for front/rear balance but that may be incorrect.

Where'd you buy the balance bar?

Randy
65 TR4
Click to expand...

You are correct about Revington using two differnet bore master's for the brakes. I retained the 3/4" bore for both at this time. I'm not going to use a propotioning valve at this point. The system originally used one 3/4" master for the brakes, so that's what I will stick with for now. The balance bar I made at work. I have it split evenly at the moment. I could easily make up differnet bars with differnet hole spacing to bias the front or rear, but I first have to finish the resto and get some miles on this before I decide which way to go. I also have the 10" drum and shoe arrangement on the rears which throws another monkey wrench into things. An adjustable bias bar would be nice, but the ones that I've seen require a minium distance needed between master's of 2 1/2". I only have 1 7/8", so any changes I make will have to be with hole spacing.
 
martx-5 said:
The system originally used one 3/4" master for the brakes, so that's what I will stick with for now.
Click to expand...
Perhaps I'm confused, but isn't that going to double your pedal effort for the same amount of braking ?
 
TR3driver said:
martx-5 said:
The system originally used one 3/4" master for the brakes, so that's what I will stick with for now.
Click to expand...
Perhaps I'm confused, but isn't that going to double your pedal effort for the same amount of braking ?
Click to expand...

I don't understand what the question is concerning pedal effort. I'm using two 3/4" master cylinders for two circuits, instead of one for 'two' circuits. Each circuit will be applying less pressure, but there is 'half' as much surface area being applied to. It should be the essentially the same as a single circuit with only one master.

Unless my understanding of hydraulics is all out of whack. I don't see how using two 3/4" masters in two circuits will change the pedal effort for the same amount of braking as using one 3/4" master for both front and rear.
 
Ok, for the sake of argument, let's say you need 100 psi hydraulic pressure for the braking you need at the moment. A single .75 MC has an area of about .44 square inches, so that's .44 times 100 = 44 pounds on the push rod.

Now let's assume you have two MCs, each still with .44 square inches, and you still need 100 psi hydraulic pressure. That's 44 pounds on each pushrod, or 88 pounds total.

The hydraulic pressure required stays the same (if the slaves stay the same), but the pushrod force to generate that pressure depends on the piston area exposed to hydraulic fluid. You've doubled the total MC piston area, so the total pushrod force is also doubled. If you had a separate pedal on each MC, then the pedal force on each pedal would stay the same, but adding them together still gets you twice as much.
 
TR3driver said:
If you had a separate pedal on each MC, then the pedal force on each pedal would stay the same, but adding them together still gets you twice as much.
Click to expand...

That would be rather unusual in a car! Rather standard on tractors though. If you were coordinated enough it would be great for sharp turns on autocross!
 
I mentioned it only to try to illustrate the point ... but you're right, it might be useful for autocrossing.
 
OK, I definetly had a brain [censored]. Randall is totally right in saying that I will wind up with twice the pedal pressure for the same amount of braking force.

I calculated out the bore size neccessary to keep the braking force exactly the same as the original 3/4" piston size for the single system. I would need to use two cylinders measuring .530" in diameter. Not happening. The smallest that I have found available is 5/8" (.625). That would yeild about a third more braking force. I was trying to do this without investing in a bunch of cylinders.

Since I also have installed Toyota four piston calipers on this car, I'm going to go back to the original set up for now and see what effect the Toyota calipers have before messing with the dual master set-up again. I've got so much more work to do on this car, that for now, it is best to shelve this project for the time being.

I will do it, but just not now.

Thank you Randall for pointing out my error. It's not what I wanted to hear, but I'm glad that you guys are paying attention. /bcforum/images/%%GRAEMLIN_URL%%/cheers.gif
 
Art,
find out what the diameter of the pistons on the toyota calipers are. If the total area is larger (than the original girling) you are going to need LESS pressure than previously, so the larger area may be fine. Now you the real problem is going to be how to adjust the balance between the front and rear brakes.
 
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