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[VintageLambo] Re: Espada brakes

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There are several Espadas fitted with dry vacuum pumps. I"ve driven one, and braking wasn"t particularly better, perhaps a bit more even in application. Different MFG use differing spring return rates on the diaphram hub, and different types of burp valves too. The vacuum during deceleration should be at least 22" HG, which coupled with the accumulator tank will give good results. I agree completely with the guesstimate about US owners wanting featherlite brakes. I drove a Chrysler Imperial from the mid-60s and almost put my passenger through the windshield, and I barely touched it. European cars seem to require a much stiffer application to get the same results. Also, pads on Euro cars are a generally harder compound to cope with the higher braking speeds to mimimize fade. Once I replaced my boosters with the Lockheed units, and cleaned the tank, lines, and replaced the one-way valve, things worked perfect (then I had a sticky caliper). The Girling unit is notoriously balky if not used regularly. I think the burp valve may get sticky allowing some vacuum to escape the low pressure side of the diaphram. Vacuum pumps: As Rev mentioned, aircraft must use a vacuum pump to operate some of the instruments. Some are "wet" pumps driven off the accessory housing with an oil bath pump systems. They are very reliable, and rarely fail. However, dry pumps have a much higher failure rate, and have been conclusively linked to several high profile fatal accidents. My diesel truck uses a wet pump, and has been going for 220,000 miles. If you use a dry pump as mentioned in the text below, there is an approx 400 hour life span for aircraft types, and automotive probably wouldn"t last much longer. Dry pumps are also noisy as hell, and make an annoying buzz while in operation. Use a leakdown test of the vacuum system, and see how long it will hold vacuum. I don"t think the cam overlap is such an issue unless you are using the brakes during acceleration when MP is relatively high(near atmosphere). Under deceleration, there is plenty of vacuum in the mainfold. I can"t say whether it"s getting to the balance tube and then to the vacuum line, to the booster. Perhaps a crossover line from the front of the two balance tubes would improve the flow into the brake reservoir. My understanding of the S2 and S3 vented disks is that the pad size and rotor diameter are the same. If the caliper pistons were the same, then brake effectiveness would be the same. Venting is to reduce fade, and keep things cooler. Again, this makes sense with the European driver needing fade resistance from high speeds. So, I think this was all related to the US drivers expectation of featherlite brake feel. The factory would have been well advised to just tell the US customers to get used to it, and press harder. Doc --- In VintageLambo@yahoogroups.com, "lgpdk" wrote: > This in reference to Fred"s message #6951, #6968, Bill"s #6969 and > others on the subject: > > Yes, it is interesting to read the Estes - Stanzani communications, > but the substance behind the pleasantries is mostly moving hardware > and going through legislative and political hurdles. From an > engineering standpoint, I can understand why the factory didn"t > react to the vague statements like: "great difficulties with the > brakes" and "serious problem with the Espada brakes", because under > most circumstances the brakes work very well on a well-tuned car. > There also is the "cultural" difference between Europe and US in the > amount of power assistance (brakes and steering) desired. Here in > the US we almost seem to want to park with a single finger on the > steering wheel and stop by breathing on the brake pedal.