Counterbalancing displacers

[Tom Booth]

I have a slight issue or problem to work out with the experimental TWO DISPLACER engine I'm experimenting with.

I want to try and at least ensure that it will run on a cold sink (ice rather than applied heat) and have every advantage I can give it.

To that end, I thought counterbalancing the displacers would be a good idea.

To have two displacers in the same chamber, I decided to try using a thin tube as a connecting rod, and an even thinner rod inside that tube for the second displacer connecting rod.

In adding some counterbalances I'm having some difficulty envisioning a way to avoid sideways stress, that is, the counterbalance connected in a way that would lift the displacers straight up and down, independently.

Some. Seesaw apparatus would lift in an arch. But that is about all I can think of, and what I'll probably use, if I can't come up with a better idea.

The connecting rods fit together with a close tolerance so could probably not stand too much sideways stress without adding more friction, which would largely nullify the advantage of the counterbalancing.

I though maybe someone might have already worked something out.

Any ideas?

Two DISPLACER engine

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[Tom Booth]

Ok, it just came to me.

A pulley system. Like an elevator with a counterbalance.

It takes the weight off and lifts straight up, so won't create any friction from lifting in an arch like my initial seesaw arangement.

Well, actually the rope and pulley themselves add some friction, but I think that would be slight in comparison with the other seesaw ides. And can be minimized.

What I want to avoid is any drag or binding on the connecting rods and sleeves. I think a pulley type arrangement should do the trick and is quite simple to implement.


https://youtu.be/17qjUcR7-fI

[thanh-cuibap]

I think, just my opinion: TWO DISPLACER will change the principle of stirling motor. Displacer has the effect of moving air from the hot zone to the cold zone and contrary,. Why don't you reduce the weight of displacer?

[Tom Booth]

I think, just my opinion: TWO DISPLACER will change the principle of stirling motor. Displacer has the effect of moving air from the hot zone to the cold zone and contrary,. Why don't you reduce the weight of displacer?

There are many, many different Stirling displacer arrangements. These are regenerative displacers. The metal mesh of the regenerator material does add weight, but I think the design, as opposed to having an external regeneratior, reduces dead air space.

At any rate, Stirling engines with this type of regenerative displacer run well, judging by what I've seen.

I found the micro-ltd Stirling on the market particularly impressive, given its very small size.

As far as why use TWO displacers?

Yes, it is a little different than a standard Stirling engine.

It is both an engine and a heat pump. Specifically, a VM heat pump http://stirlingengineforum.com/viewtopic.php?f=1&t=2525 which utilizes two regenerative displacers.

Read my other thread for details on the experiment.

Here:. http://www.stirlingengineforum.com/view ... f=1&t=1029

[Tom Booth]

As things progressed, I started trying to mount support brackets and such on the lid of the cookie tin, however it was still far too weak and prone to buckling and bending so I had to add more cross bracing.

I ended up going with the seesaw method of counterbalancing as it seemed the displacers really have little room to move any more than about 1/2 inch and this did not seem enough movement to cause any binding.

It really made a tremendous difference.

Previously, lifting the displacers by the connecting rods, I could feel the weight. So much so that it made me worry that the big engine running on such a small temperature difference would not be able to develop enough pressure to lift such weighty displacers with their imbedded metal mesh regenerators.

Now with the counterbalance, I'm able to move the large top displacer easily with the slightest touch of my pinky. By adjusting the counterbalance (magnets) the displacer can be made to seem completely weightless. Just what I was hoping for.

I still need to fashion another counterbalance for the bottom displacer.

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[thanh-cuibap]

I will learn more about them when I have time
And hope you succeed with your ideas!

[MikeB]

Doesn't it add an awful lot of friction to have the two displacer rods running inside each other?

[Tom Booth]

I will learn more about them when I have time
And hope you succeed with your ideas!

Thanks. That didn't happen this time though. Back to the drawing board.

[Tom Booth]

Doesn't it add an awful lot of friction to have the two displacer rods running inside each other?

Yes, that was a problem. Particularly because they are thin, soft metal (brass and copper) and tend to bend buckle and bind easily. But that was all that was available at the local hardware. It did work, so long as they were straight, but I had to keep adjusting and straightening them.

If I try that again, I'd probably use thicker steel rods and tubes. Or maybe plastic or Teflon or something.

A rhombic drive Stirling has this sort of connecting rod inside another connecting rod.