The Stovebolt Site Forums The Shop Area Engine Shop Vacuum Tank/Reservoir

Question has to do with plumbing a vacuum tank for the vacuum wipers without a check valve. I have a vacuum tank in my precious metal pile from a 40' Nabors trailer. It's about 8"x24". If I install a tee below the carburetor, one line to the wipers, one to the tank. When accelerating or going uphill, will the low engine vacuum deplete the tank, resulting in basically no extra vacuum for the wipers?

Since the tank will be mounted behind the cab, bed under the flatbed, just thinking about how to make it work with a single line. My strong suspicions are it'll take two lines with a check valve on the vacuum supply line to the tank.

RonR

I'm letting the question above stand just to illustrate how slow my brain works these days. All I need to do is place the check valve immediately downstream of the intake, then T into the line downstream of the check for the wipers. So only one line making the long run to the tank methinks.


RonR

I believe you have it figured out. Should be fine.

I agree it is worth a try with that configuration. The key will be the vacuum differential required to open and close the check valve.

My suggestion is to make a trial run with the tank sitting on the floor on the passenger side. That will tell you a lot. Tee a vacuum gauge into the line to the tank so you can watch what is happening. Find a long hill to climb while running the wipers.

If I understand your thinking, you want the check valve to close when the engine vacuum drops below what is in the tank. Then it should re-open when the engine vacuum goes above the tank vacuum. It should stay open under equal vacuum.

You are storing energy to run the wipers in the tank. It is functioning as an accumulator.

One scenario that will be interesting to observe is when you have depleted the tank and engine vacuum is still low. If things are working as I think they should then the wipers will operate (or actually not operate!) as if there is no tank in the system.

The next scenario to consider is what happens when the engine is trying to recharge the tank while the wipers are working. That might create a situation where the check valve starts opening and closing rapidly and interfering with wiper operation.

Great idea! I am interested in your results.

Don’t know much about vacuumed tanks but in the 70,s they had ones that looked like tomato juice cans ,yours being so big would be interesting .

I remember those #10 juice can accumulators. A major difference in those applications is that the overall vacuum demand was fairly low. Vacuum was used mainly to power short term functions like moving ventilating flaps and locking doors. There was no continuous demand like the wipers.

This was also in the early era of emission control systems. The small accumulator was needed to prevent a temporary/sudden drop in vacuum which could affect the emission control system.

I've found it's easier to hide a small-diameter, long vacuum reserve tank. I use a piece of 4" PVC pipe about 3 feet long with caps glued onto the ends and a grommet for a brake booster check valve fitted into one end cap. Paint the tank black and bracket it inside a frame rail. I prefer to run a second line from the tank to whatever vacuum accessories I'm using.
Jerry