Selecting bigger alder seeds by their falling speed in air

I'm curious that no one has suggested using a cyclone. A light tin can is easily transportable and by sizing the cone angle and pipe diameters appropriately they can be made to be very selective and have no filters or screens to get blocked or contaminated.

It's donkey's years since I did any analysis on such a thing, but I should imagine it's easy enough to unearth if you look.

Richard

--- news://freenews.netfront.net/ - complaints: snipped-for-privacy@netfront.net ---

In article , Michael Bell writes

Michael,

Read all the helpful suggestions. As far as I can see, no-one has yet suggested a sideways air current.

Since (as someone pointed out) the weight varies as the cube of the linear dimensions, and the cross-sectional area varies as the square, a bigger seed would be less deviated by a cross current than a smaller one, so the distance from the vertical axis at which the seed hits the ground should vary inversely as the size of the seed.

You could try this quite easily, and (assuming it works) the apparatus should be quite portable. The cross-wind would have to be pretty constant, and the thing shielded from extraneous winds.

The idea is quite reminiscent of the method used in a mass spectrometer, with an electromagnetic field acting as the "side wind".

David

I don't see how they could NOT have the same density independent of size. But it doesn't matter. I want seeds that contain food material, if a seed contained a lot of fluff, I wouldn't want it anyway.

Michael Bell

It's a possible design. But air would flow into the outlet at the bottom for the heavies so I would have to put a glass jar at the bottom to collect them. However I have gone so far down this route that I don't want go another way.

Michael Bell

I am aware of this idea, but I want something vertical so that I can hold it, and tip the cones in and get a result. I don't want something that needs to be levelled on a bench.

Michael Bell

ITYM Weight is proportional to 'width' cubed.

Nope, it's a standard square/cube law situation. Bigger seeds will fall faster in air, assuming the same density.

-- Peter Fairbrother

Actually it's not exactly that, but a complete analysis would take several pages of math. It's close though.

Take a half-full jar of honey or syrup and shake it vigorously, then put it down. The big bubbles will rise fast, but the small bubbles will take a long time to rise.

It's the same with seeds in air, except the other way up, and honey is thicker than air.

-- Peter Fairbrother

Ah - must be the man from ipomea then ;-)

Regards, Tony

For the same shapes so is surface area and Michael mentioned that.

Indeed but I was conceding that althought Michael's analysis was flawed, heavy seeds fall faster if of the same density. You don't spend 30 years working in wind tunnels without learning some of the basics! Mind you that was a while ago now so can't claim to remember everything!

Could you not hang it from say a tree branch and then weight it so it hangs level?

Graham

Not very portable, but possible.

Michael Bell

Branch position certainly does make a difference, but even within one branch or even cone, there is variation in size. What causes that? Surely the pollen!

So that when I find a tree with small seeds I can go on to the next, and when I find a tree with big seeds, I can spend some time on it.

Then suggest a better way to go about it.

Michael Bell

I'm pretty sure it's not the pollen, but I'll phone my brother-in-law later today and ask him for confirmation of this.

I do know that he has told me that seed size etc is, in general, determined by the female parent.

You'll still have to take things like water content into account. Are the seeds big because the tree is well watered? Are they big because the tree/branch etc is in a good position? And so on.

I don't think choosing the biggest seeds from a single tree will help much.

You want to choose a tree or ten which have big seeds, lots of seeds, seeds with the best nutritional value, which are not growing in especially favourable conditions, and collect seeds from those trees, and only them.

Once you have chosen the trees, I don't think the size of the actual seed you use will matter very much. You will have a good maternal line, and I don't think the paternal line affects seed size much, if at all.

Again, I will confirm this later today. It's not something I've had to consider for ipomoeas, just the pretty flowers.

See above.

BTW, have you eaten alder seeds? What do they taste like?

I hear the catkins taste horrible ...

-- Peter Fairbrother

Probably chicken, most things taste like chicken.....................

John S.

..except Co-op chicken :( --

Chris Edwards (in deepest Dorset) "There *must* be an easier way!"

Fine. Now the next stage of the design.

My sorting tube has an internal diameter of 2.5 cms and the fan has an internal diameter of 8 cms, and I want to connect them with an inverted cone - actually an inverted pyramid because it will be square-sided.

It would be nice for the seeds to settle in bands of different size in the cone that joins them, but in such turbulent flow that's asking for too much.

So failing that, what I want to do is to do it in an energy efficient way, and that means an evase. What angle should it be? There is plenty of vertical space. What should the expansion angle be? It will probably be expressed as 1 in x rather than in degrees. Google acknowledges the meaning of the word, but I can find no way of calculating it.

Michael Bell

Yikes. I hope you're young.

How many generations of tree breeding do you envisage?

BugBear

Typo. It should have been "seeds". Yes, it's a hard one. Maybe beyond my time, though I plan to do it quicker than some think of.

Michael Bell

Why for goodness sake ? Starting with two circles it's easier to make a cone. It will also be more efficient that some odd thing with squares crudely fitting circles. It could be reasonable with transition pieces for circle to square at each end but complicated to design and make.

Henry