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[ortwin]

Q: Any idea how far the contact is below the top's overall CM (including core) when on the bottle cap?

Hard to say, somewhere between one and two millimeters ?

[Jeremy McCreary]

Still want to find a better rigging method and a material suited better for spokes.

The thiinest guitar string? Takes a lot of tension with little stretch.

[ortwin]

Still want to find a better rigging method and a material suited better for spokes.

The thiinest guitar string? Takes a lot of tension with little stretch.

Yes, but at the same time I have to find a way to fasten the ends. Currently I make a knot in the nylon string. Like in that picture of the hub I posted earlier in this topic. 

Still need to find out if such little knots are possible with wire, or if there are even better possibilities. SUGGESTIONS ARE WELCOME!

[the Earl of Whirl]

Here is a picture of guitar strings.  It shows the end that is secured at the bottom of the guitar, nearest the sound hole.  Would this “knot/hub” do the trick?  If so, it is not too hard to take the pieces and put one on the other end of the string.

[ortwin]

Here is a picture of guitar strings.  It shows the end that is secured at the bottom of the guitar, nearest the sound hole.  Would this “knot/hub” do the trick?  If so, it is not too hard to take the pieces and put one on the other end of the string.

Thanks, keep those ideas coming!
This one is very big in comparison to a tiny knot in a 0.3 mm nylon string. Remember, if I go from this aluminum flywheel to brass or to something with even higher density, things become smaller still.
Also, as I do the rigging at the moment, the line is under some tension already while I apply the securing knot on the second end. That doesn't help of course putting it at a precise position.

[ortwin]

The Easy Listening Top was fun, I will still continue to give it a spin, but the major development with it I consider done.
I learned something about some problems that are specific to suspension tops and hope I can use those findings for improvements in the next top.
I think I want to move from Easy Listening to Brass Band music.  I tried different ways of arranging the lines, every way had its problems, the position and the angle where the threads in the flywheel are, need to be modified for a next version.

Best results with Easy listening: on concave mirror: 9:51 , on dedicated base with recessed tip 19:05.
Moving to brass keeping the mass of the flywheel and AMI constant, I dream of 20 minutes on a concave mirror and over 30 minutes with the recessed tip.

This last rigging became a bit complicated, a sign to move forward I guess.




Yes, as you can see in the video, there is an A-side and a B-side to Easy Listening.



In playing around with the recessed tip and the dedicated base, I came to think that those are not necessarily features my tops are not allowed to have. After all, all those concave mirrors are also quite special bases and also a lot larger/heavier/more expensive than that simple bottle screw cap I used. I don't know for sure yet, so I will probably make tops that can do both modes. The possibility of longer spin times is of course also tempting.
 

[Jeremy McCreary]

Best results with Easy listening: on concave mirror: 9:51 , on dedicated base with recessed tip 19:05.
In playing around with the recessed tip and the dedicated base, I came to think that those are not necessarily features my tops are not allowed to have.

Don't worry, checked with Mistress von Karman. She said that as long as the top's overall CM is above the contact in operating configuration, you can have those features.

But she's watching you!

[ta0]

Those are great times for Easy Listening!

You are very good at making good tops out of common things you find around.

I look forward to Brass Band!

[Jeremy McCreary]

What ta0 said.

[ortwin]

...
You are very good at making good tops out of common things you find around.
...

Thank you. That is a very polite way to say that my tops look shabby.
But that is alright, the Levitrons I build usually also did not look that great at first, but with the last  one, you see in my first post here in the forum I am happy.  That means I still hope that one of these ugly ducklings I presented so far will turn one day into a sleeping beauty.

[ta0]

Thank you. That is a very polite way to say that my tops look shabby.

On the contrary! I'm amazed how good they look!

[ortwin]

Thank you. That is a very polite way to say that my tops look shabby.

On the contrary! I'm amazed how good they look!

Ah, this fishing for compliments is still working  .
But now I started thinking about the Brass Band. First thing I noticed, was that "Band" also has a meaning that makes a bit of sense in this context here. 
Good enough.
Then I measured the starting speed of "Easy Listening". I got it up to around 600 RPM which is about the same of what I can do with the modified Euler disk weighing 440 g and having a diameter of 75 mm.
That leads to the question of the dimensions of the flywheel for Brass Band : Should it be the same dimensions as Easy Listening ? Or should I keep the mass and AMI constant? It is far from clear for now for me what would be the best. Gut feeling tells me to go with a square generator of 8 by 8 mm and an outer diameter of 80 mm. Somehow in between.
Still guesswork, maybe I should calculate AMI of three square generators within reach and then decide somehow from there.  Ans better suggestions from the crowd?

[Jeremy McCreary]

@ortwin: I'm not familiar with the ergonomics of your starting method, but you might make some wooden dummies to see what diameter gives the fastest release speed. Since your aerodynamics are pretty much set, you could then focus on minimizing critical speed using a spreadsheet and the formulas I gave you.

[ortwin]

Availability helps deciding! I received the brass ring on the right in the photo today. I want to try to turn that into "Brass Band".

[Jeremy McCreary]

Availability helps deciding!

Tell me about it -- the curse of modular topmaking!

Really looking forward to Brass Band.