Pellets as TOPS

Pellets as TOPS

Joined: June 7th, 2010, 12:14 am

April 28th, 2012, 11:49 pm #1

In consideration of the thread regarding diabolo pells and straight sided bull-its, I thought it might be interesting to spin a pell like a child's top and see how things lined up. I was sort of expecting the pell to self align as it stood spinning on it's heavy dome head.

Well, Suprise! The skirt flares widely while the pell spins. Not flat on the side, but no more than 45 degrees to verticle.

This is with JSB Jumbo,s in .22 and Eunjin 16 grains in .177. (what I have ready to hand)

As fast as I could twirl them between my fingers onto the stone countertop.

Hmmm.
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Joined: April 25th, 2003, 11:44 pm

April 29th, 2012, 12:18 am #2

It is that air flow in flight which creates the drag stabilization of the diabolo.

You can get a very low speed flow by dropping the finger spun pellet whilst standing on a chair. Dropping it onto plasticine or sticky fly paper will show that the pellet will always land nose first providing you employ the correct spinning technique with your fingers ..........and use pellets like JSB which have their C o G in the right place.
... Edit: This of course combines the three criteria and shows that at very low velocities spin is the most important factor. Just dropping the pellets as indicated in the reference is insufficient. As the velocity (air flow speed) goes up the spin rate becomes less important. It still has a place in the scheme of things but is less important. .......... Kind regards, Harry.

Here's a referencehttp://www.network54.com/Forum/79537/th ... h+my+posts..
Last edited by Yrrah on April 29th, 2012, 12:31 am, edited 1 time in total.
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Joined: June 13th, 2009, 4:42 pm

April 29th, 2012, 12:30 am #3

In consideration of the thread regarding diabolo pells and straight sided bull-its, I thought it might be interesting to spin a pell like a child's top and see how things lined up. I was sort of expecting the pell to self align as it stood spinning on it's heavy dome head.

Well, Suprise! The skirt flares widely while the pell spins. Not flat on the side, but no more than 45 degrees to verticle.

This is with JSB Jumbo,s in .22 and Eunjin 16 grains in .177. (what I have ready to hand)

As fast as I could twirl them between my fingers onto the stone countertop.

Hmmm.
www.facebook.com/huntfishtn
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Joined: June 7th, 2010, 12:14 am

April 29th, 2012, 12:35 am #4

It is that air flow in flight which creates the drag stabilization of the diabolo.

You can get a very low speed flow by dropping the finger spun pellet whilst standing on a chair. Dropping it onto plasticine or sticky fly paper will show that the pellet will always land nose first providing you employ the correct spinning technique with your fingers ..........and use pellets like JSB which have their C o G in the right place.
... Edit: This of course combines the three criteria and shows that at very low velocities spin is the most important factor. Just dropping the pellets as indicated in the reference is insufficient. As the velocity (air flow speed) goes up the spin rate becomes less important. It still has a place in the scheme of things but is less important. .......... Kind regards, Harry.

Here's a referencehttp://www.network54.com/Forum/79537/th ... h+my+posts..
Air flow can only "correct" and always with over correction,(conservation of momentum) and then oscillation about the center.
(some aircraft are like that)

But you know this.

And if the pell were thrown upwards at less than 30 fps, would it also strike the jell-o on axis? I do not believe it would. the air flow that fills the abscence is too small a force.


Perhaps a rifle and a smooth barrel side by side would demonstrate something new.

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Joined: June 7th, 2010, 12:14 am

April 29th, 2012, 12:42 am #5

It is that air flow in flight which creates the drag stabilization of the diabolo.

You can get a very low speed flow by dropping the finger spun pellet whilst standing on a chair. Dropping it onto plasticine or sticky fly paper will show that the pellet will always land nose first providing you employ the correct spinning technique with your fingers ..........and use pellets like JSB which have their C o G in the right place.
... Edit: This of course combines the three criteria and shows that at very low velocities spin is the most important factor. Just dropping the pellets as indicated in the reference is insufficient. As the velocity (air flow speed) goes up the spin rate becomes less important. It still has a place in the scheme of things but is less important. .......... Kind regards, Harry.

Here's a referencehttp://www.network54.com/Forum/79537/th ... h+my+posts..
Considering "normal profiles" and often with hollow skirts. (air gun specific)
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Joined: April 25th, 2003, 11:44 pm

April 29th, 2012, 1:04 am #6

All projectiles are subject to drag. But where the centre of wind pressure is located relative to the centre of gravity seems to determine the relative effect of drag in establishing and maintaining point on stability.

Pointed bullets that eventually lose their spin stability seem to want to swap ends as the rock in the sock, as Robert puts it, takes over.

Diabolos with heavy heads and draggy lightweight rear ends will always want to travel head first. ...

Pellets with light heads, some hollow points (CMs)and others with hollow head and some with all the wrong characteristics like light hollow pointy heads, may fight to turn end about but the skirt drag prevents them from quite making it. They precess and spiral readily .... KR, H.
Last edited by Yrrah on April 29th, 2012, 1:06 am, edited 1 time in total.
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Joined: April 25th, 2003, 11:44 pm

April 29th, 2012, 1:27 am #7

Air flow can only "correct" and always with over correction,(conservation of momentum) and then oscillation about the center.
(some aircraft are like that)

But you know this.

And if the pell were thrown upwards at less than 30 fps, would it also strike the jell-o on axis? I do not believe it would. the air flow that fills the abscence is too small a force.


Perhaps a rifle and a smooth barrel side by side would demonstrate something new.
Shot at 28 yards; JSB 8.4 gr .177; MV something a little over 400 fps; un-rifled rough "smooth bore" 1948 Stella.

Target backing was a lead plate but the target was placed on a table for photographing.



The angle of the target and plate relative to the rifle and to the pellet's trajectory at impact - unknown. ... Note the angle of the sun to the target, therefore the shading of and within the pic.



Best regards, Harry.
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Joined: April 25th, 2003, 11:44 pm

April 29th, 2012, 1:31 am #8

Air flow can only "correct" and always with over correction,(conservation of momentum) and then oscillation about the center.
(some aircraft are like that)

But you know this.

And if the pell were thrown upwards at less than 30 fps, would it also strike the jell-o on axis? I do not believe it would. the air flow that fills the abscence is too small a force.


Perhaps a rifle and a smooth barrel side by side would demonstrate something new.
http://www.network54.com/Forum/79537/th ... ..+and+all. ... KR, H.
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Joined: June 7th, 2010, 12:14 am

April 29th, 2012, 1:35 am #9

but missing contemporary expectations
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Joined: April 25th, 2003, 11:44 pm

April 29th, 2012, 1:45 am #10

Air flow can only "correct" and always with over correction,(conservation of momentum) and then oscillation about the center.
(some aircraft are like that)

But you know this.

And if the pell were thrown upwards at less than 30 fps, would it also strike the jell-o on axis? I do not believe it would. the air flow that fills the abscence is too small a force.


Perhaps a rifle and a smooth barrel side by side would demonstrate something new.
probably never did get to spin on its axis as its one point of contact. Spun at 40,000 rpm it may have damped out the precession. Spun at 10,000 rpm with a 900 fps air flow it may have done just as well. ST barrels in my experiments are indicating that to be so. ... KR, H.
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