Online contest: Fastest boomerang?

[ortwin]

At Marines we had a little contest:  "Who can throw the fastest boomerang with a S8 Alice?"


We measured one of Daniel (Orso) at 6000 rpm, but there were some problems with the speedmeter, ta0 did not even get to trow his third attempt.  The main problem was that I had not brought the proper reflective tape that needs to be applied to the top for that measurement.


Here at home I found that tape and did a few measurements with my S8 Love with bearings.
So lets have a little informal contest for all those who have access to a rpm velocity meter and the ability to throw a boomerang. Only the absolute RPM is of interest here, so I think small tops should be favored by this rule.  Fixed tip would also be okay with me, but it probably does not offer any advantage.
I would further relax the rules by not asking for a boomerang to the hand it can be to a platform and does not even have to be a boomerang.


Just state the way you did it, your measuring equipment and your top.


I start by saying that with my S8 Love bearing top I reached with a boomerang to the hand 8400 rpm.
Surely others can easily reach 10000 rpm, come on tell us what is your fastest boomerang?



Edit:





It is a Strummol8 "Love" with a bearing tip. The largest diameter across is 44 mm, height 52 mm. It weighs 47 g.
I changed the tip to the new, larger S8 tip for better string behavior.

[Jeremy McCreary]

Really looking forward to the results!

Especially interested to see how the speeds from many different shapes and sizes compare. Would be nice to know at least the make, model, max diameter, and mass of each top. A top photo, too, but I get that you don't want to ask too much of your participants.

We recently discussed what the fastest peg top would look like, but I still don't have a good feel for the many trade-offs involved. An empirical database will help.

During the outbound leg of a boomerang, string tension converts the top's outward linear momentum into spin angular momentum. Here, a top with a low AMI per unit mass (e.g., a solid top) and would seem to have an advantage in terms of spin rate at the end of the outbound leg.

Still thinking through the more complicated turn-around and return leg. But for the pull-back to bring the top back to you, the string has to be able to pull against the top's AMI. And there, a larger AMI per unit mass would seem advantageous.

Gotta be a sweet spot in that trade-off somewhere. And that's just one of many.

[ta0]

A speed of 8400 RPM is very good, if accurate.

I don't trust the first measurement one gets when pointing the tachometer to the top. Many times you get crazy measurements that are easy to dismiss, but what if it still gets you a wrong measurement but it's believable? I think the correct way to do it, is by taking several samples of the decay curve and extrapolating to time zero. Of course, it's very important to determine exactly time zero. This is easy if you are filming with the same camera both the throw and the display of the tachometer.

These are curves I measured in the 2000's with a Duncan Bearing King (one unmodified and one modified by Takeshi):



It's easy to see that at time zero the speed for the unmodified (lighter) BK was very close to 7000 RPM.

So 8400 RPM with the smaller Alice is possible, but 10,000 RPM seems to me quite a challenge.

[Jeremy McCreary]

A speed of 8400 RPM is very good, if accurate.

I don't trust the first measurement one gets when pointing the tachometer to the top. Many times you get crazy measurements that are easy to dismiss, but what if it still gets you a wrong measurement but it's believable? I think the correct way to do it, is by taking several samples of the decay curve and extrapolating to time zero. Of course, it's very important to determine exactly time zero. This is easy if you are filming with the same camera both the throw and the display of the tachometer.

Same experience with laser tachometers here, and I like this workaround. But few participants will be willing to go to all that trouble.

So I volunteer ta0 to boomerang all of his tops and clock them in this manner. Should only take a year or two.

[ortwin]

... I think the correct way to do it, is by taking several samples of the decay curve and extrapolating to time zero. Of course, it's very important to determine exactly time zero. This is easy if you are filming with the same camera both the throw and the display of the tachometer....
...

Yes, you and me have the possibility to do it the correct way, but even I lack the motivation to do it that precise and I wanted to have more than two or three entries here.

So 8400 RPM with the smaller Alice is possible, but 10,000 RPM seems to me quite a challenge.

Actually it is the even smaller "Love" not "Alice". I used the "MAX" function of the instrument but I also observed a few times a clean run down of the frequency from values starting above 8000 rpm. So I think it is probably real. Maybe I could also record a sound sample (remember it is a bearing top) , do a frequency analysis on that and estimate an rpm value from that. If that coincides with the rpm meter, all the better.

And really,  I think even I can get to 9000 rpm - if I practice a bit, if I can fully concentrate on the boomerang and do not have to think about the measurement at the same time, if I get more comfortable with "Love", If I don't have to worry that the top is flying at walls or ceilings where it should not go.

[ortwin]

I am still not happy with the measurement and the spin decay curve, but I think it proves a point I made earlier.



https://youtu.be/Ldli3okfA9M


Edit: How do you like the "lens" (cocktail stirrer) I use to shape the laser beam?

[MrYo]

I think you need some "salt" to break 10.000 rpm, something like a 25€ of discount on Sara top as prize for Love bearing, 30€ of discount on Sara top if you beat 10.000 rpm with Alice.
If you use another top... an Alice
The first one reaches the 10.000 rpm wins!

Maurizio

[ta0]

Edit: How do you like the "lens" (cocktail stirrer) I use to shape the laser beam?

I love the cylindrical lens idea!

I think you need some "salt" to break 10.000 rpm, something like a 25€ of discount on Sara top as prize for Love bearing, 30€ of discount on Sara top if you beat 10.000 rpm with Alice.
If you use another top... an Alice
The first one reaches the 10.000 rpm wins!
Maurizio

Wow! Now I will have to try it!

[ortwin]

I did not come here to claim a prize, just want to share some slightly better measurements.



The max. RPM value was 9968 RPM in this measurement. The spin decay curve looks better then before mostly because I held the tip firm in my fingers for most of the time, so I did not need to move my hand around to balance the top. 
The gap towards the beginning of the curve is because of the transfer of the top from my palm to the finger grip, that happened out of the view of the RPM meter. The glitches toward the end of the curve might stem from unwanted reflections?
Also today I did not use that "cylindrical lens", instead I applied a long thin stripe of reflective tape to the S8 Love.

[ta0]

The max. RPM value was 9968 RPM in this measurement.

I think that's a pretty impressive throw!
Extrapolated to time zero you obviously went above 10,000 RPM, so I say you won!

[ortwin]

No no no! I am part of the organizing committee, I can not really take part. Plus I never saw a value above 10.000 RPM. So it is still open, you don't get
off this that easy ta0!
How about others? Attila? Jun? Yahir? Texture? And there are surely many more in the forum that can throw a better boomerang.

[Mermouy]

No no no! I am part of the organizing committee, I can not really take part. Plus I never saw a value above 10.000 RPM. So it is still open, you don't get
off this that easy ta0!
How about others? Attila? Jun? Yahir? Texture? And there are surely many more in the forum that can throw a better boomerang.

Sure but not everyone got a speedmeter...

[ortwin]

...
Sure but not everyone got a speedmeter...

Oh yes, that is certainly true! So, do you want to offer this "essential" equipment in your online store?

[ta0]

I did some preliminary throws with a Love and only got about 8000 RPMs. It feels to me that the throws are strong.
Although I have some ideas on how to improve the speed by changing the string and wrap, 10000 RPMs looks difficult to achieve.

Ortwin: I'm impressed about your 10,000 RPMs. Did you compete in javelin throwing when you were young? 

[Mermouy]

...
Sure but not everyone got a speedmeter...

Oh yes, that is certainly true! So, do you want to offer this "essential" equipment in your online store?

I guess Ali-express is doing a pretty good job 

[ta0]

Tried again this morning with the Love. Normal throw, as hard as I can while keeping control: the best I'm getting is about 8400 RPM max, so extrapolated to zero a little higher, but lower than 9000. I did get a few higher values displayed but those were measuring errors as the values were jumping around. I generally get very smooth decay measurements starting from the first value.

[ortwin]

Tried again this morning with the Love. Normal throw, as hard as I can while keeping control: the best I'm getting is about 8400 RPM max, so extrapolated to zero a little higher, but lower than 9000. I did get a few higher values displayed but those were measuring errors as the values were jumping around. I generally get very smooth decay measurements starting from the first value.

Hmmm, I wonder what is going on there!
This what my Love looks like before a throw:





The string is 140 cm long and 2 mm thick. You can see the wrap height. I use this type of string with most of my tops up to the size of Augusta.
I have to hold it tip pointing downwards. I only learned to throw a top with tip downward this year in Marines, and that was with  a Sweetle with a far longer string that I am usually using for that. Anyways, I found I can only throw Love well with tip down and it felt awkward at the beginning. The motion of my throw can be seen in that video above. After the last set of strong throws (only about five or so) where my last spin decay curve comes from, I really felt my arm, that kind of surprised me.
How does your spin down curve compare to mine where they should be about the same? Are the spin times you get from 8000 down to zero comparable to mine in that range? - Of course the state of the bearings can make a huge difference here.

I thought about the possibility of analyzing the speed of a top by filming it in slow motion. I estimate that you need at  a camera/cell phone with at least 500 fps (frames per second) to measure a speed of 10000 RPM.