On my Vicky there is no way to get the MC and booster under the floor and putting the booster out where it can be seen is out of the question. I need the four wheel power discs because of my shitty feet so I'm using the MC/booster mounted laterally back near the gas tank. It is readily serviceable there to check fluid etc. so no concerns. Also it is well away from any heat sources which has proved to be problematic in the past. To actuate it I'm using a Wilwood compact MC under the floor and a matching slave on the booster. Easy peazy! My question is, does anyone actually know if I need a 2lb residual valve in the primary circuit to maintain a full pedal? The slave is a good 12" above the MC. I know you generally do not use them on a clutch system but that is a bit different than a split braking system. I know this is not typical on a traditional rod so I'm not sure if anyone on here has ever had any experience as this was quite common back in the old street roddy days. Thanks upfront guys! Pics soon.
I've never heard of that solution before. Extended pushrod for sure, with bellcranks if necessary to avoid obstruction. From a safety standpoint I suppose it's no worse than using a single, 'fruit jar', system. Not sure about the residual valve. Possibly not required as what is described is rather clutch like. Or maybe they could be used in a clutch but the need is not paramount as it is with brakes where quick take up is imperative? Chris
Used to be very common. Not so much on HAMB style cars as they tend to be more old timey. In my opinion only, no more risky than a single MC which we've all used already. Much safer than having your brakes cooked under the car by a tightly packed exhaust, (if I could get it under there). The MC in this case is well above the calipers but I'll use 2lb residuals just to keep a bit of tension on the pads. I'm more worried about too much braking than too little. I'm running bias plys so locking them up will be a concern for sure. I'm going to drill my pedal/bracket on the primary for both 4/1 and 6/1 and experiment a bit. The secondary on the cylinder is a direct coupling.
It sounds like you have a hydraulic clutch setup operating a remote master cylinder. That part wouldn't require a residual valve. I've seen a couple of cars with similar space issues that had very long (and heavy) push rods to a master cylinder that in one case was almost 3 ft from the pedal assembly. T bucket style frame that had a pretty fat automatic in it and no space to put much of anything until you got back behind the tail shaft of the trans. It had a simple bracket off the frame back there and the main thing I remember about it was that he used a piece of tubing about like you would see on a T bucket drag link for the rod with an end that fit the pin on the pedal on one end and made an adjustable (threaded) end for the other end. I had to make a similar but shorter setup for my 48 when put a dual master cylinder on it and had to make a push rod. The first rod I made bent and I had to make a stronger one.
I considered about every combination of rods, bellcranks, crosshafts, and all kinds of cables etc. This is the only solution that is even close to working. I'm sure this is going to take some experimenting and yeah, I have a decent E-brake setup as well.
I'm getting this fabbed up and it is working perfectly! There still are some kits on the market. This is not uncommon, just for me. I'm generally into more traditional setups so this is learning time for me.
Hard to tell from the picture, but it looks like the left side axle tube could get too personal with the proportioning valve knob. You could flip it up, without modifying anything.
Good observation there. Pic is deceptive however and everything clears nicely through full suspension travel. The proportioning valve is readily accessible while safe from road damage and not requiring the services of a contortionist. My greatest concern is having too sensitive brakes. The primary circuit is fairly adjustable as to both pedal ratio and stroke from 4-1, a typical power brake ratio, and 6-1 a more typical manual brake ratio. As I mentioned above this setup is somewhat new to me so there is a bit of a learning curve here. I've gone to a 1960 dual GM pickup MC and matching slaves for both brake primary and clutch actuation, The MC looks right at home on the firewall and with the D-Russ style front brake covers it will not be too obvious the car is running some serious brakes when you pass me at 80 in dim light. Just waiting for a few parts to arrive to finish up and give it a try. A few progress pics.
Just looking at the pics, I wanted to mention the panhard bracket on the rear is obviously not finished. I promise to neaten it up considerably. It wouldn't last long like that.
Looks like it should work, but the safety factor of a dual master is lost on the front half of the system.
That was the one thing I thought about. I've used these single cylinders in dozens of cars and to be honest I never had even one fail. I can't say the same about the Corvette style dual cylinders. I've actually gone through several of those already. This has been a lot of fun doing something I haven't done 20 times already. Hopefully it works as it should. On paper it plots out well. In reality, I'm stuffing 350 HP into a homemade car of 80 year old parts built by a guy who is at most times not totally right. What could go wrong? (Just kidding, my engineering is actually quite good.).
Yep! And could've achieved the same [or better] results by using a PBR VH 44 inline booster. Or if you wanted to keep it really simple , use a small 7/8"bore [ AC Delco #18M309 ]quick uptake M/C and a lower pedal ratio. [Quick uptake aka Stepped Bore] @Koz The answer to your original question.[below] Normally yes [including clutches] because the M/C gravity syphons back and pulls the slave back into the cylinder. You can "sort of" avoid this if the slave has an adjustable pushrod and it is adjusted so the piston cannot move any further back. On open wheel race cars I've built, [4 wheel disc] we do not use any residual valves or proportioning valves. We simply mount a M/C remote reservoir higher up [usually on the roll bar under the engine cover]
Just because of the height difference so you won't have drain back issues swap the valve from the clutch side of mc [remember original sides are reversed.]. I would also have some gussets on the brackets for the MC and Slave.
Or just one between the two mounts? But there's some very sturdy material in use there, so maybe not, but belt and braces is always nice! Chris
+3 on some triangulation stiffener(s) for your booster and slave mounts. A web tying the 2 would be great. Looks good otherwise!
Thanks guys! I used stuff I had or could get easily, (any info on an inline booster?), however, I did have a small 7/8" Wilwood MC and matching slave on hand. I elected not to use it as I have had at least one fail in the past. As I noted above I have never had the GM one let me down. Just a ,matter of faith I guess. Typically I would say those brackets need to be gusseted. I'm used to designing and welding structural steel. The rear crossmember is .250 wall and the brackets made of the same. A gusset would be a nice safety net but I trust my welding and the safety factor on them is off the chart. Both brackets will be in the 180,000 lb. area to fold or break the weld and neither the booster or cylinder is anywhere near that level. I elected to forgo a gusset for that reason. I'm going to be very careful in setting this up and testing it before any road time and will keep an eye on everything for some time.
Checked out the VH 44, (actually VH 40 for four wheel discs) and I really like my setup a little better. They do the same thing but seem to have the slave incorporated in the booster assembly. Other than that, no advantage I can see. I believe they use mostly Japanese and Australian parts and as such they are probably more obtainable and commonly used outside the US. Everything I have here is US sourced and easily serviced at the local NAPA or any auto parts stores. Great idea Kerrynzl and it proves my solution is somewhat sound. I am a bit of a creature of habit I guess and I'm really cheap sometimes as well.
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