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Discussion Starter #1
I just bought a vacuum brake/master cylinder combo on e-bay
for my 1981 Jet Electrica. It should arrive today.

I do not have a vacuum pump yet.

If I install the booster/brake/MC will braking without
vacuum require more pedal pressure? How much?

John in Sylmar, CA
PV EV

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Discussion Starter #2
Depending on the weight and load. Press your foot to a floor and it might
feel like that. I use either a GMC or a Ford vacuum pump that are use on
diesel engines, that is belted off the pilot shaft of the main motor. These
type do not need a vacuum canister if you are just just using the vacuum for
brakes.

I just pick up a vacuum pump from my independent auto parts store, who also
does vehicle repair. They had one that they took off a damage Ford diesel
engine. I got it for $0.00.

Roland


----- Original Message -----
From: "JS" <[email protected]>
To: "Electric Vehicle Discussion List" <[email protected]>
Sent: Friday, October 26, 2007 11:56 AM
Subject: [EVDL] Vacuum brakes


> I just bought a vacuum brake/master cylinder combo on e-bay
> for my 1981 Jet Electrica. It should arrive today.
>
> I do not have a vacuum pump yet.
>
> If I install the booster/brake/MC will braking without
> vacuum require more pedal pressure? How much?
>
> John in Sylmar, CA
> PV EV
>
> _______________________________________________
> For subscription options, see
> http://lists.sjsu.edu/mailman/listinfo/ev
>

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Discussion Starter #3
in a vehicle with optional power brakes the master cylinder for the power b=
rake system will have a larger bore and require more pedal effort, when ope=
rated without supplying vacuum, than will the manual brake master cylinder,=
if however you are mixing masters from different vehicles you will need to=
know how the bore diameter of the new master compares to the bore of the o=
ld master to know what the change is going to be

> Date: Fri, 26 Oct 2007 10:56:37 -0700
> From: [email protected]
> To: [email protected]
> Subject: [EVDL] Vacuum brakes
> =

> I just bought a vacuum brake/master cylinder combo on e-bay
> for my 1981 Jet Electrica. It should arrive today.
> =

> I do not have a vacuum pump yet.
> =

> If I install the booster/brake/MC will braking without
> vacuum require more pedal pressure? How much?
> =

> John in Sylmar, CA
> PV EV
> =

> _______________________________________________
> For subscription options, see
> http://lists.sjsu.edu/mailman/listinfo/ev

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Discussion Starter #4
John,

Assuming the vacuum brake/master cylinder combo is sized correctly for
the application, similar to an ICE vehicle, imaging driving at speed in
the ICE car and the motor dies, and you brake just enough to use up all
vacuum. The pedal will then feel hard, and maybe take both feet on it
to get a great amount of braking. You will be able to stop, but not
easily, and possibly not quickly. You will not want to drive this way
for long or at all due to safety concerns, and comfort. In your EV,
you'll do ok at the stop signs as you are not in a vehicle with an
automatic transmission with an ICE motor trying to move forward.
Getting the EV stopped however will be a chore.

If the vacuum brake/master cylinder combo is not sized correctly for the
application, you could have better or worse performance that the above
situation. If the master cylinder has a piston that is too large, you
will get a very hard pedal. If the piston is too small, you will get
better pedal feel (easier to depress and stop) but the piston may bottom
out and give no additional increase in braking beyond that point.

One site I looked at mentioned the following question that may help: "I
have installed power brakes on my original manual brake car and now the
brakes are extremely sensitive.
There are two attachment points on the brake pedal. For power brakes you
need to use the lower attachment hole. Using the upper hole will make
the brakes too sensitive." One idea would be to use the "manual"
attachment point until you get the vacuum pump set up, and then change
the setting.

Please consider all safety measures in your set up, and make sure you
have correctly sized and compatible parts. I am not a mechanic.

Alan

-----Original Message-----
From: [email protected] [mailto:[email protected]] On
Behalf Of JS
Sent: Friday, October 26, 2007 10:57 AM
To: Electric Vehicle Discussion List
Subject: [EVDL] Vacuum brakes

I just bought a vacuum brake/master cylinder combo on e-bay
for my 1981 Jet Electrica. It should arrive today.

I do not have a vacuum pump yet.

If I install the booster/brake/MC will braking without
vacuum require more pedal pressure? How much?

John in Sylmar, CA
PV EV

_______________________________________________
For subscription options, see
http://lists.sjsu.edu/mailman/listinfo/ev

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Discussion Starter #5
Alan Brinkman wrote:

> Assuming the vacuum brake/master cylinder combo is sized
> correctly for the application, similar to an ICE vehicle,
> imaging driving at speed in the ICE car and the motor dies,
> and you brake just enough to use up all vacuum. The pedal
> will then feel hard, and maybe take both feet on it to get a
> great amount of braking. You will be able to stop, but not
> easily, and possibly not quickly.

This may or may not be true for a particular vehicle. My '87 Forsa (Chevy Sprint) conversion has power brakes, and I have a GM vacuum pump installed and ready to go, but I've never yet bothered to power it up. The brakes work just fine without any vacuum assist and since I am still within the GVWR I've had no issue with being unable to stop just a quickly as I want.

> One site I looked at mentioned the following question that
> may help: "I have installed power brakes on my original
> manual brake car and now the brakes are extremely sensitive.
> There are two attachment points on the brake pedal. For power
> brakes you need to use the lower attachment hole. Using the
> upper hole will make the brakes too sensitive." One idea
> would be to use the "manual" attachment point until you get
> the vacuum pump set up, and then change the setting.

I'll have to check if this is the case for my car also; if so, I might be able to improve the pedal feel even more!

Cheers,

Roger.

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Discussion Starter #6
John-

I just installed a vacuum pump and a new vacuum brake booster (same
master cylinder) in my '84 Chevy S10. The truck originally had
vacuum-assist brakes, but when the original owner converted it he gutted
(removed the diaphragm from) the booster in the pursuit of easier manual
braking. Which is to say that he believed (as seems to be the general
wisdom) that a vac brake system without a vac source was worse than a
straight manual system.

However...when I first installed the booster and pump, I rigged the pump
up wrong. The practical upshot was that I test-drove the truck with a
vacuum brake system and no vacuum, which I think is pretty close to the
situation you are asking about. I could not tell any difference (which
told me I had screwed up, since I was expecting a big improvement) in
the braking performance vs. the straight-manual setup. It should be
noted that the previous fully-manual braking performance was pretty bad,
and that there may be some difference in fully-manual performance vs.
gutted-booster performance.

So, take this for what it's worth. My anecdotal evidence suggests both
that a)the diaphragm in an '84 S10 brake booster doesn't significantly
impede no-vac braking and b)some folks think it does enough to gut a
booster. I'm not sure that this is exactly the same question you are
asking (that is, whether gutted-booster==no-booster), but it seems to me
that it should at least be closely related, if not identical. If I were
doing it, I would wait for your vacuum source to arrive before
installing the new booster (you should be able to do both in an
afternoon pretty easily), but I doubt it's going to make a real big
difference if you decide to jump the gun. That said, your Whr/mi may
vary.

Good luck!

Hunter


JS wrote:
> I just bought a vacuum brake/master cylinder combo on e-bay
> for my 1981 Jet Electrica. It should arrive today.
>
> I do not have a vacuum pump yet.
>
> If I install the booster/brake/MC will braking without
> vacuum require more pedal pressure? How much?
>
> John in Sylmar, CA
> PV EV
>
> _______________________________________________
> For subscription options, see
> http://lists.sjsu.edu/mailman/listinfo/ev

_______________________________________________
For subscription options, see
http://lists.sjsu.edu/mailman/listinfo/ev
 

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Discussion Starter #7
I gutted the booster on my '76 Datsun, and it improved the braking
immensely. I still can't panic-stop, but it doesn't require the amount of
effort to brake that it did without a pump. Probably abut 1/10th the effort.

Joseph H. Strubhar

Web: www.gremcoinc.com

E-mail: [email protected]
----- Original Message -----
From: "Hunter Cook" <[email protected]>
To: "Electric Vehicle Discussion List" <[email protected]>
Sent: Sunday, October 28, 2007 6:49 PM
Subject: Re: [EVDL] Vacuum brakes


> John-
>
> I just installed a vacuum pump and a new vacuum brake booster (same
> master cylinder) in my '84 Chevy S10. The truck originally had
> vacuum-assist brakes, but when the original owner converted it he gutted
> (removed the diaphragm from) the booster in the pursuit of easier manual
> braking. Which is to say that he believed (as seems to be the general
> wisdom) that a vac brake system without a vac source was worse than a
> straight manual system.
>
> However...when I first installed the booster and pump, I rigged the pump
> up wrong. The practical upshot was that I test-drove the truck with a
> vacuum brake system and no vacuum, which I think is pretty close to the
> situation you are asking about. I could not tell any difference (which
> told me I had screwed up, since I was expecting a big improvement) in
> the braking performance vs. the straight-manual setup. It should be
> noted that the previous fully-manual braking performance was pretty bad,
> and that there may be some difference in fully-manual performance vs.
> gutted-booster performance.
>
> So, take this for what it's worth. My anecdotal evidence suggests both
> that a)the diaphragm in an '84 S10 brake booster doesn't significantly
> impede no-vac braking and b)some folks think it does enough to gut a
> booster. I'm not sure that this is exactly the same question you are
> asking (that is, whether gutted-booster==no-booster), but it seems to me
> that it should at least be closely related, if not identical. If I were
> doing it, I would wait for your vacuum source to arrive before
> installing the new booster (you should be able to do both in an
> afternoon pretty easily), but I doubt it's going to make a real big
> difference if you decide to jump the gun. That said, your Whr/mi may
> vary.
>
> Good luck!
>
> Hunter
>
>
>
JS wrote:
>> I just bought a vacuum brake/master cylinder combo on e-bay
>> for my 1981 Jet Electrica. It should arrive today.
>>
>> I do not have a vacuum pump yet.
>>
>> If I install the booster/brake/MC will braking without
>> vacuum require more pedal pressure? How much?
>>
>> John in Sylmar, CA
>> PV EV
>>
>> _______________________________________________
>> For subscription options, see
>> http://lists.sjsu.edu/mailman/listinfo/ev
>
> _______________________________________________
> For subscription options, see
> http://lists.sjsu.edu/mailman/listinfo/ev
>
>
>
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