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Discussion Starter #1
Hi Folks,

Anyone got a Thomas 12v vacuum pump for their brakes?
They look like this:


What do I use to connect into the "vacuum hole" on the top of the pump?
Mine has a threaded hole which I expect all of them do, but where do I get the connector that screws into this hole?

Cheers!
:)
 

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Discussion Starter #4
Ok, we're getting somewhere. I have the system installed but I have a problem.
the pump achieves vacuum and then switches off which is normal, however less than 5 seconds later it switches back on. This must mean there's a leak in theory but buggered if I can find it.
I have a stop valve connected at the pump end just in case the pump is leaking air into the vacuum system so there's no problem there.
My question to those who have their brake systems finished, how often do your vacuum pumps kick in without touching the brake pedal? Once every 5 mins? Never?
 

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I have a small reservoir that I made out of PVC pipe with end caps and PVC glue. I drilled and threaded the holes and then installed the pipe fittings with teflon tape. My pump initially takes 20 seconds to evacuate my little reservoir at which point it shuts off. I get two brake applications and then the pump comes on again and shuts off in about 12 seconds. I gave it a leak down test and it came on again 12 minutes later so I know I too have a leak. It should hold vacuum indefinitely...right?..or at least longer than 12 minutes. I suspect that my leak is occuring at the teflon tape on the fittings because I am using new booster hose and "full circle" clamps that are on very tight. I also have two new check valves I installed but still same problem. Im thinking that I may get rid of the teflon tape and use epoxy to seal the fittings to see if this helps. How did you affix the brass fittings to your reservoir Kiwi?
BTW...how to do you post the pics within the text like you do?...mine show up as thumbnails.

On a side note people...you want to use real brake booster hose. It has a thicker wall so it will not collapse under vacuum and adversely affect your brakes.
 

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Discussion Starter #7
You're not a post-whore? Oh go on, admit it! You can't resist it!
LOL

Ok, I covered everything in PVC cement glue stuff and now it's going fine. I pressed the brake, got the vacuum pump motor going, waited for it to reach vacuum, then timed how long before the motor kicked in again.

Thirty minutes later I got sick of waiting. I guess that means the leaks are gone!
Here's a picture in glorious full size.
:p

You can see the master cylinder (bottom right), the vacuum canister (behind the front grille) and the vacuum pump (in the black box behind the left headlight).
I fear my vacuum tank isn't big enough though as whenever I put my foot hard down, the motor kicks in. If I press the brake lightly it's ok but realistically the motor's going to kick is fairly often. I don't have room for a bigger canister yet either.

I'm proud of the way the vacuum pump is tucked away in a box. It brings the noise level of that little pump down HEAPS! It's a quiet little thing now.

Maybe later I'll install a large mega-tank behind the lower front grille. Still, it's one thing done off my list!

P.S. Maybe your images are too big so they automatically get thumbnailed? I reduce all my pics to 640x480.
 

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This is just a noob mechanical question, but why do cars use a vacuum for brake assist and not pressure? To me it makes more sense that if the brake pads need to squeeze the discs then you would just pump pressure into a cylinder that would expand and push it, how does it work with a vacuum? I know there is a practical reason i just can't work it out.
 

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why do cars use a vacuum for brake assist and not pressure?
Mostly because vacuum is a readily available resource that all gasoline engine develop without additional equipment. It’s drop-dead simple and very cheap to implement.

The vacuum servo (booster) on a power brake system is a fairly simple device which places vacuum on both sides of a diaphragm when the brakes are at rest. When you press the pedal, atmospheric pressure is allowed to enter one side of the diaphragm, allowing the vacuum on the other to "suck" the diaphragm (and the master cylinder push rod) in, assisting in applying the brakes.

Vacuum assist has been around so long that it's become the default for brake servos, even in diesel vehicles which need a mechanical pump driven from the crankshaft to develop vacuum.

Systems exist that do use other power sources, notably some that activate ABS brakes, but the vacuum servo is cheap and simple, and will likely be with us as long as there are throttle plates in ICE engines.
 

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This is just a noob mechanical question, but why do cars use a vacuum for brake assist and not pressure? To me it makes more sense that if the brake pads need to squeeze the discs then you would just pump pressure into a cylinder that would expand and push it, how does it work with a vacuum? I know there is a practical reason i just can't work it out.
The old Audi 5000s used hydraulic pressure from the power steering pump to do just this. This pump used to fail constantly because it had a double duty job. Audi went through 4 incarnations of this pump each improving on the previous design in an attemp to make it more reliable. Eventually the system went away and now they are back to vacuum boosters like everyone else. Heres a pic of the overall brake setup, brake master cylinder and brake booster.
 

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RE: I don't have room for a bigger canister yet either.

One of the local EV guys suspended about 8 feet of PVC under his EV. Do you have clearance for that? He said it was nice because the pump ran for a while and then shut off for a long time.

You're total volume looks a bit small to my untrained eye. :) I get 2 hard brakings on my system before the pump kicks on - and because of the low "pressure" set point on the regulator, I know that I have at least two more in the pipe, good for panic events and if the pump decides to quit.

Next step for me is to pump a box around the pump to quiet it down. In the world of almost silent EV's the pump noise sure is annoying!
 

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KiwiEV, can you tell me where I can get a Thomas 12v vacume pump for my little Geo conversion project? I also need to find (2) 5K throttles--the lever type. And to all answering my posts--I am unable to find them. I tried using the refresh and F5 key but they are not there. If you mention something concerning the Gov or a corp does the forum delete those posts? or are you notified if that occurs? I am still new to this forum.
One point I would like to mention-after being on this forum last night -when I ran a cookie scan I had more cookies to remove then I have ever had. There are alot of Corps & Gov offices attempting to get info off of the members PCs from this site! I would suggest all to get the best spyware available.
Neogeogray
 

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slwhiteside, the 66 T-Bird I used to drive had a large Tomatoe juice can for its vacume resavour. What would work well is a empty freon R-12 can as they are made to handle pressure either way and they already have the top fitting on them. They are approx 1.5 - 2 gallon I think.
Neogeogray
 

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I see five cookies associated with DIY EV, and all of them appear to be associated with valid forum business, last visit, forum view, session hash, activity, etc.

Since my browser is set to delete all cookies upon exit, there is very little else in the cookies cache this morning, certainly nothing that I am alarmed about, but then I do run a fairly tricked-up version of Proxomitron (software proxy) to kill scripts, pop ups, banners and adverts.
 

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Discussion Starter #17
KiwiEV, can you tell me where I can get a Thomas 12v vacume pump for my little Geo conversion project? I also need to find (2) 5K throttles--the lever type. And to all answering my posts--I am unable to find them. I tried using the refresh and F5 key but they are not there. If you mention something concerning the Gov or a corp does the forum delete those posts? or are you notified if that occurs? I am still new to this forum.
One point I would like to mention-after being on this forum last night -when I ran a cookie scan I had more cookies to remove then I have ever had. There are alot of Corps & Gov offices attempting to get info off of the members PCs from this site! I would suggest all to get the best spyware available.
Neogeogray
Hi mate, sorry for the delay in replaying (holiday etc).
I found my Thomas vacuum pump and switch on Ebay. Last time I looked there were four available for sale, all cheaper than any EV parts dealer I'd found.
Send a message to Nick Smith (on this board) as he found a smaller, quieter vacuum pump. He sent me details in an email but he didn't mention a brand name. As per his email, "It’s only about 20cm long x 13cm high x 11cm wide. It’s pretty quiet too…"
I found the Thomas pumps louder than a firing range until I put it into it's little "shuddup" box. :)
 

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I got myself a MES-DEA pump second hand from the "ev tradin' post". It is a cute little unit and comes with proper automotive type connections.
 

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Kiwiev, thank you for the info. I have heard that the Thomas vacume pumps are very loud. I'll keep watching ebay until I find a quieter pump.
I found the 5K throttles on two ele sites. around 80.00 each thats about 60.00 more then they are worth but I'll buy 2 anyway. Hows the weather down your way? We were getting hit with storm after storm for a while there-until people actually called into the alternate media and told of the tanker planes -seeding the air were spotted off the coast of the western USA by more then one person--then all the sudden the weather got better. (www.infowars.com has the weather modification story if your intrested) Now we are having nice weather here in the northern area of Idaho just 30 or so miles so of the Canadian border. They chemtrailed today so we will have to stay at home tomorrow, (as I have 3 hepa filters in my home) -otherwise its nice here as we have mountians all around us! Its like living in Alaska again. Nothing like snow caped mountians to cheer you up. Are you in the USA or Aus?
neogeogray
 

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my $.02:
<my ford diesel truck has a 12 volt vaccuum device to run (of all things) the heater controls and the auto lock front hubs. the unit has a pump, and reservoir and included 1/4 fittings. I'm thinking that a junkyard has these by the bunches and probably cheap since the stupid things don't appear to wear out. They are also mostly quiet.
 
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