'30s Brake Vac. Can

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Packardbarry
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'30s Brake Vac. Can

Post by Packardbarry » Sat Aug 25, 2012 5:21 am

Know the Factory Spec on LBS PULL of the '30s Brake Vac. Can?

Dave Czirr
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Re: '30s Brake Vac. Can

Post by Dave Czirr » Sat Aug 25, 2012 5:35 am

Yes, I've got some a reference to that somewhere. But it depends on which models/year since, depending on year the Eights and Twelves used two different diameter booster cylinders and the 33/34 models had a dash control to vary the amount of boost so the lbs of pull would depend on which valve setting you selected.

You can also calculate it knowing the surface area of the vacuum piston and the vacuum applied.

I'll browse around and see if I can find that reference over the weekend, if no one else finds it first.

PS - Found it in a letter from Bendix to me back in 1975. The BK-13740 suspended cylinder type as used on 33/34 Eights and Super Eights applied 249 lbs of pull at selector valve position #4 (ed. correction #1 position).

Packardbarry
Posts: 249
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Re: '30s Brake Vac. Can

Post by Packardbarry » Sat Aug 25, 2012 6:25 am

WOW!!!!!!!!!! 249. Dont think my gage goes that high. Interesting that they give #4 setting. Believe thats the low vac. - think 5". Think i have a sick can. Guess its time for a new seal.

Dave Czirr
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Re: '30s Brake Vac. Can

Post by Dave Czirr » Sat Aug 25, 2012 6:31 am

Oops, my error, #1 position!!

I've asked a friend who is sharper with math than me to calculate the cylinder pull at 19 inches of vacuum. We'll see if he can confirm Bendix's number. I'll let you know.

Packardbarry
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Re: '30s Brake Vac. Can

Post by Packardbarry » Sat Aug 25, 2012 6:50 am

Thanks Dave

Dave Czirr
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Re: '30s Brake Vac. Can

Post by Dave Czirr » Sat Aug 25, 2012 7:43 am

Gene, a quick and rough calculation. The power cylinder at 6-1/4 inch diameter has an area of about 30 square inches. Calculate the weight of Mercury in a 19 inch column (as in manifold vacuum of 19") with a 1 square inch area, multiply by 30 square inches, and you get just a bit over 210 lbs of force. In the Bragg-Kliesrath service manual data they show a 6" booster cylinder giving 282 lbs of pull at 20" of vacuum.

So somewhere between 210 and 282 lbs is the concencus.

Packardbarry
Posts: 249
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Re: '30s Brake Vac. Can

Post by Packardbarry » Sat Aug 25, 2012 2:32 pm

Guess ill go hook up a Mercury Park Lane to it and see if it pulls it. Never realized they had that much power. I always figured it was me who was strong.

jacko
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Re: '30s Brake Vac. Can

Post by jacko » Sat Sep 01, 2012 2:06 pm

I have a 33 eight and the vacumn assist at #4 seems to work quite well but I doubt it is at 200+ lbs pull but I have not measured it. In any case, has anyone rebuilt the seal on the vacuum can? How do you get the can open to install a new seal? I have not removed the can so have not had a chance to examine how it might come apart.
Thanks,

bob Jacko

34PackardGuy
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Re: '30s Brake Vac. Can

Post by 34PackardGuy » Sat Sep 01, 2012 2:15 pm

Bob, servicing the booster vacuum chamber is pretty easy. I forget the details, did mine decades ago, but as soon as you look at it and see how simple it is, it will all be quite apparent.

Packardbarry
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Re: '30s Brake Vac. Can

Post by Packardbarry » Sun Sep 02, 2012 7:05 am

Believe this seal is the correct dia. for the eights
http://www.classicandexotic.com/store/p ... -seal.aspx
Havent done one for a few yrs but If i remember:
-Mark the can to the cover
-Drive out the drive screws
-Rework the can and the cover to a mach. screw
-Cant remember how the seal goes to piston but it was no big deal.

Yesterday i found the cable from the Booster to lever was way loose. Dont know if it streched or unscrewed itself but i adjusted it and seems to be better but pretty sure i need a new seal so guess i have another project.

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