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Dual Master Mock-Up

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Art- Was going thru the archives and came upon this post.
This been on your mind a while?

7148 - 10/07/04 11:59 AM TR3 Dual Masters
martx-5 martx-5 Online content
Luke Skywalker

Registered: 07/12/02
Posts: 1651
Loc: Kings Park, NY
Anyone put dual master brake cylinders in their TR-3??

I'm contemplating this as I'm doing the resto. I understand there are some TR-4 parts necessary. What's actually needed?? Which pedal assembly and masters are required. And yes, I do know that the pedal box has to be enlarged. What else is entailed??
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Art

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Yes, there are a lot of things that I have contemplated during this resto, and the dual master set-up is certainly one of them. Most of the other changes from original are pretty much tried and true, so there aren't too many surprises. This one just hit me in the head because I didn't really think it out well enough.

I'll eventually get the system in, but after I get the car up and running.

Look at the date of that post. It's been over three years since then. Time to get this sucker together. /bcforum/images/%%GRAEMLIN_URL%%/thirsty.gif
 
If you are looking for smaller bore cylinders,check out rallying sites. There is 1 on UK that i look at a lot. I think they have smaller ones and are Girling.
 
70herald said:
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.
Click to expand...

Well, I'd almost bet that the Toyota calipers have more total area then the OE Girlings, but I'll measure them and find out. That brings me to the rears. The 9" drums are often modified with the Morgan cylinders to allow the rears to work more, which I believe are larger then the TR's. I have the 10" drums, and I don't think there are any mods available for those. So, as it stands now, with the Toyota calipers and a single system, I will have less braking from the rear. I'm sure I could work all of this out, but right now, it's on the back burner.

The stupid thing about all of this, is that I'm doing alot of this stuff because I can. I work for a rebuilder, so getting the parts cost me next to nothing. You know, just give me those two Toyota calipers. The rest of the stuff comes from the stuff laying around at the club, and of course, Tony at Ratco, who put the triple cylinder design that I mocked up on his computerized plasma cutter and cut out the pieces. We may go with this project, but right now I need to do some more homework.
 
martx-5 said:
The 9" drums are often modified with the Morgan cylinders to allow the rears to work more, which I believe are larger then the TR's. I have the 10" drums, and I don't think there are any mods available for those.
Click to expand...
Well, it's an easy swap to the 9" drums, and given how scarce the 10" parts are, would probably pay for itself.

But, I believe you should be able to use the same cylinders for either 9" or 10".

Might not be a problem anyway, as the whole reason Triumph switched to 9" was because the 10" tended to lock early even with small diameter slaves.
 
FWIW, I just read that Kas Kastner did the twin-master conversion, using two 5/8" masters and modifying the pedal to get back the lost advantage. He said it worked out very well.
 
That would be the only way to get it done. It's probably one of the reasons why Revington modifies the pedals like the TR4. However, besides the TR4 pedals splaying out to better line up with the masters, the short end of the pedal fulcrum is a bit longer then the TR3 also. That would cut down on mechanical advantage, wouldn't it?? I'll have to carefully measure both ends of both sets of pedals. Perhaps the foot length of the TR4 pedals are longer.
 
martx-5 said:
That would be the only way to get it done. It's probably one of the reasons why Revington modifies the pedals like the TR4. However, besides the TR4 pedals splaying out to better line up with the masters, the short end of the pedal fulcrum is a bit longer then the TR3 also. That would cut down on mechanical advantage, wouldn't it?? I'll have to carefully measure both ends of both sets of pedals. Perhaps the foot length of the TR4 pedals are longer.
Click to expand...

Yes. To reduce the force your foot would have to apply to the pedal, you would have to reduce the short arm and/or lengthen the long arm. I think that this would also give you better modulation control with your set-up because, since the volume of fluid going to the wheels would be about halved in each master cylinder (since it's going to two wheels instead of four), the distance the piston moves would be halved. This would mean that your foot (pushing on the stock pedal levers), although pushing harder, wouldn't move as far to apply the brakes, decreasing "feel", wouldn't it?

So by changing the arms' length, you would get back to the same force and distance on the foot side as you had before the modification to dual master cylinders.
 
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