Development of cooling system expansion tanks / swirl pots

I concluded the previous blog post about making and installing the components of the cooling system by finding the right connectors for the controller. This blog post is about the expansion tanks / swirl pots. Perhaps I would like to explain this first.

Expansion tank / swirl pot, why?

Although the temperature differences will not be great, the coolant will expand and contract. It then wants to go somewhere or come from somewhere. An obvious solution is to simply make an expansion tank analogous to the original closed cooling system of the Amazon that is connected to a thin tube. However, I also want a so-called ‘swirl pot’. Because the coolant flows in along the edge, a rotating movement is created and it vents automatically.

Machining aluminium

So I measured a few things and bought some aluminum. I had never actually worked with that before.

Aluminium bought

From Mischa I learned that for a nice result it is best to provide the lid with a round edge. After looking at some Youtube examples, I got to work on it myself. First of all, by making a mold. This is a round disc with a diameter slightly smaller than the intended lid and a rounded edge (with a router).

Milling a wooden mould

And then sand them nice and smooth.

Mal gladschuren

Then I cut a circle out of aluminum and attached it and then hammered it around.

Eerste keer aluminium kloppen

Pretty nice for a first time.

Dekseltje controller swirl pot

It will also be the place where I will fill the cooling circuit, so I bought a weldable radiator neck.

Welding neck radiator aluminum

And unscrewed the lid so that it fits in.

Dekseltje uitgedraaid

And then the beginning is there.


The next step was to make the connection to the controller. I still had an aluminum AN8 adapter that I could use. Just increase the inner diameter a bit.

Drill out AN8 adapter

It then goes into the elbow that comes out of the controller.

Aansluiting swirl pot op controller1

Then I made a pipe to screw on it.

Aluminium buisje met schroefdraad

And then it has to be welded to the swirl pot.

Buisje op tussenstuk

Just to be sure, I tried it on with the bonnet on, but there is more than enough space there.

Fitting with the hood on

This way the liquid flows nice and low in the swirl pot so that it can go below the level and you don’t hear a ‘waterfall’.

Buisje tussen controller en swirl pot

A similar approach for the swirl pot of the battery cooling circuit.

Batteries Cooling Circuit Expansion Tank

There was also the question of whether the holes for the hoses were not too high.

Hose   route expansion tank batteries

Those corners are quite tight. First I had to make a distribution block.

Manifold nipples that are too small

Hmm, that doesn’t hold up. A little too little wall thickness. Let’s grab another block.

Larger distribution block

That’s better, now the tapered nipples can be tightened properly.

Blokje met nippels

It should be something like that after I rounded the back.

Block with nipples on expansion tank

Conclusion: the holes in the battery box should be lowered. In this way, a ‘waterfall’ is almost inevitable or the level must be very high. In addition, it remains tight in terms of hoses. So I marked where there is space in the box and made new holes.

Making new holes in cooling pipes

Yes, that looks a lot better. Now the pipes run nicely horizontally in a slight curve.

Horizontal Output Cooling Hoses 2

That triggered a new layout issue. The controller and batteries swirl pot are then exactly on top of each other so it was a question of how the controller return pipe should run. The swirl pot at the back of the batteries wasn’t pretty, so I went inside.

Controller return pipe inside

Moving controller swirl pot

In that case, the hose would have to kink after the battery swirl pot, or the controller swirl pot could not stay on the corner. I chose to make a new and shorter intermediate pipe. I omitted the AN8 adapter and made the correct male thread myself.

Insert male thread

First I twisted a piece of aluminum tube on the lathe to the correct outer diameter and then cut wire with the cutting plate. Just for this wire I don’t have the change wheels to be able to make it with the lathe. Anyway, that’s how it can be done.

Buitendraad gesneden

Twisted the pipe into elbow and made it fit in the right orientation on the outside wall of the swirl pot. Analogous to this, I also made an outgoing pipe.

Kort tussenpijpje en uitstroompijpje

The hose that comes on top of it must then be attached to the top connection of the radiator. However, it was not yet in the same plane.

Aansluiten op radiator

Again I made a zig-zag gradient out of aluminum that sticks through the bonnet trap.

Pijpje voor motorkap steunplaat

And in this way allows for a movement forward and down and thus fits precisely.

Verloopje aangesloten op radiator

Input manifold front battery box

The input manifold of the front battery box is a bit simpler. It just comes directly against the box. I can then make the same connections on these as those on the battery modules.

Incoming refrigeration manifold

So first I drilled out the hexagonal aluminum on the lathe.

Uitboren zeshoekig aluminium

And then make the holes in it according to the drawing.

Gaten boren voor connectors

Hmmm, but wait a minute. That’s very little space next to the hole. That will be difficult to seal. Just grabbed a new block of aluminum. At the same time I made a tube on the lathe which is then screwed into the bottom for the supply.

Incoming refrigeration manifold v2

However, the corner at the bottom is beveled so that it ends up exactly at the pump with a 45 degree silicone hose.

Koelverdeelblok en pomp

In addition to the fork to the three modules at the front, there must also be a branch to the rear for the battery modules there. Directly on the pipe just gets a bit tight.

Branch to the rear

So I made a connection to the distribution block itself. Because there are 5 modules at the back and it has to go all the way to the back, I wanted to make that connection well in the direction of power.

Aftakking naar achteren vanuit verdeelblok

It just doesn’t look very pretty. After sparring with Ben (Tinustuning) he indicated that it doesn’t really matter at the current speeds I’m dealing with. So I opted for a right-angled connection.

Aftakking haaks naar achteren vanuit verdeelblok

I use the hole at the top that I made to be able to drill out to place a temperature sensor. The distribution block itself was a bit too short for that, so I made an adapter.

Cooling Manifold Batteries

That’s starting to happen. Now all I have to do is make holes and tap wire for the ‘quick connect’ connections.

New lids expansion tanks

Now that I had gained some more experience in working with aluminum, I was no longer so satisfied with the first lid I made for the swirl pot. So I made a new attempt. Step 1: mark and make a circle.

Marking a round on a lathe

This time I took a bigger round.

Groter basisrondje voor dekseltje

That is more difficult to make because more material has to shrink to be able to turn the corner, but it does give a nicer result (if I do say so myself).

Nieuwe deksels

Now another significant piece of the puzzle has been completed. That is, prepared to be welded.

Expansievaten klaar om te laten lassen

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OldVolvo is a classic Volvo hobby blog by Lars Rengersen.

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