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#1
09-06-2008, 11:49 PM
 jlsawell Senior Member Join Date: Apr 2008 Location: BrisVegas, Australia Posts: 321
Vacuum pump reservoir - math

Can someone please check my maths?

I'm putting together the PVC reservoir for my Thompson Vacuum pump to power the brakes.

Talking to KiwiEV, he mentioned his was about 2L capacity and he was planning to double it because it's good to show off the brake/thrust combo of the EV and after a couple of stop+starts, the reservoir needs time to refill.

So, I'm planning to go 5L right off - here's my maths.

Volume of a cylinder is Pi x r(squared) x length

So if I'm using 50mm diameter (25mm Radius) PVC from the local plumber, we get.

25 x 25 = 625 (radius squared)
625 x 3.142 = 1,964 (area of the circle)
1,964 x 1273 (length) = 2,499,854

So if I use 2 pipes 1,273cm long and 50mm diameter I will get my 5L capacity - correct?

Sorry if that's confusing to those poor cavemen not using metric system.

We can still use the term "quarter pounder with cheese" though...
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#2
09-07-2008, 05:24 AM
 O'Zeeke Senior Member Join Date: Mar 2008 Posts: 302
Re: Vacuum pump reservoir - math

Quote:
 Originally Posted by jlsawell Can someone please check my maths? I'm putting together the PVC reservoir for my Thompson Vacuum pump to power the brakes. Talking to KiwiEV, he mentioned his was about 2L capacity and he was planning to double it because it's good to show off the brake/thrust combo of the EV and after a couple of stop+starts, the reservoir needs time to refill. So, I'm planning to go 5L right off - here's my maths. Volume of a cylinder is Pi x r(squared) x length So if I'm using 50mm diameter (25mm Radius) PVC from the local plumber, we get. 25 x 25 = 625 (radius squared) 625 x 3.142 = 1,964 (area of the circle) 1,964 x 1273 (length) = 2,499,854 So if I use 2 pipes 1,273cm long and 50mm diameter I will get my 5L capacity - correct? Sorry if that's confusing to those poor cavemen not using metric system. We can still use the term "quarter pounder with cheese" though...
Hi jlsawell, i had no idea cheese was metric. Anyway i think your math is right except where are you going to stick 2 tubes 1.273 meters long? I dont think it matters if you have 1 tube 2.5 M long or 10 tubes .25 M long connected together except for the greater amount of joints to leak. Check out http://www.driveev.com/jeepev/convpgs/pbrakes.php Can you get 4" (9.8cm)pvc? I think the length could be decreased by a factor of 4 making it easier to fit it in. Hope this help a little, if not i have a friend Dave who has a Ph.D in math who might to be able to figure it out.

Last edited by O'Zeeke; 09-07-2008 at 05:27 AM.
#3
09-07-2008, 04:54 PM
 jlsawell Senior Member Join Date: Apr 2008 Location: BrisVegas, Australia Posts: 321
Re: Vacuum pump reservoir - math

Quote:
 Originally Posted by O'Zeeke Check out http://www.driveev.com/jeepev/convpgs/pbrakes.php Can you get 4" (9.8cm)pvc?
Thanks O"Zeeke, that Jeep link is exactly what I'm looking for.

The 2.5m tube won't fit anywhere but I was thinking I might fit 2 x 1.2m tubes across where the radiator used to be. I'll have to do some measuring of the car but so long as the math is right I'll be able to fit something together with a visit to my local plumbing supplies warehouse.

Much obliged for that url!
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Mad Max 2: The Road Warrior - coming soon to a suburb near you!
#4
09-22-2008, 06:07 AM
 jlsawell Senior Member Join Date: Apr 2008 Location: BrisVegas, Australia Posts: 321
Re: Vacuum pump reservoir - math

OK, for about \$20 at my local Bunnings Hardware I got 1m of 50mm PVC tube, two end caps, 4 washers, 2 brass hose nipples and 2 brass locks for the inside. 3m of vacuum hose cost me \$12 at the local auto parts store. I cut the tube down to 80cm, as this will give me about 5 litres of vacuum.

(2.5cm x 3.142)^2 x 80cm = 4.9 Litres

Then when I got home I learned that the thread on the brass nipples is about 1/2 inch - a lot larger than the largest drill bit in my kit. Back to bunnings for a drill bit and I also picked up some silicone sealant and a gun. I drilled a hole in the end caps, fitted the washers and nipples to the locks and sealed all around them. Pushing the vacuum hose onto the nipple was a bit of work, but then tightening up the hose clamps was the easiest part of the job.

So: here's my finished setup. I've checked that it will fit in the car in front of the radiator, using cable ties to secure it to the body.

Now all I've gotta do is afford the vacuum pump from ZEVA.

And do I need to keep the radiator? My gut feel is to chuck it, so long as the transmission doesn't use it for cooling, right?
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__________________
http://www.diyelectriccar.com/garage/cars/36

http://ev-pulsar.blogspot.com

Mad Max 2: The Road Warrior - coming soon to a suburb near you!

Last edited by jlsawell; 09-22-2008 at 06:12 AM.
#5
09-22-2008, 07:46 AM
 e_canuck Senior Member Join Date: May 2008 Location: Canada Posts: 283
Re: Vacuum pump reservoir - math

Hello jlsawell.

I did'nt follow all your steps. But the radiator is for dissipating the heat from the ICE. I see very little use for it. On my donnor the rad also old the AC's own rad and one inertia switch for the airbag.

If you have stuff hanging from it, you might have to reposition them or manufacture some brackets.

Your reservoir is very long, therefore thin. Brian's first build colapsed.
http://www.diyelectriccar.com/forums...ighlight=brian

You might have to do similarly.

I am also waiting for my pump. Expensive "sucker" is'nt it?

Take care,

DP
#6
09-22-2008, 08:48 PM
 jlsawell Senior Member Join Date: Apr 2008 Location: BrisVegas, Australia Posts: 321
Re: Vacuum pump reservoir - math

Quote:
 Originally Posted by e_canuck You might have to do similarly. I am also waiting for my pump. Expensive "sucker" is'nt it? Take care, DP
I will probably have to do similarly - have to see when the pump arrives. They are expensive suckers. I am sure Cuthbert Calculus could invent something cheaper...
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Mad Max 2: The Road Warrior - coming soon to a suburb near you!

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