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You most probably are right, in a case of a bigger friction, the way of transfer the energy would be changing. But friction isn't prnament on the whole way of the booster, it might make additional problems with timing.

I'm happy to hear about the postive results of your test. I will think about doing the same. But now there is the time for me to land from the space just to the bed

It's really great to see new, original ideas, and out-of-the-box brainstorming comments being welcomed on the forum once again, rather than merely being ridiculed, and put down with a dismissive, oh-so-venomous tongue-in-cheek comment!      

This one is a real winner, whether or not it turns out to be workable.  I, as the resident champion of the unconventional,  hope that it flies farther, faster, and more accurately than any sling in history ever has!  But then, again what do I know?  I still think that the Assyrian soup spoons were really just long-tailed toli sticks!    They were there to protect the Assyrians from ancient long bows because they were unable to defend themselves with their "inferior" Asiatic composite bows, which although lighter, shorter and easier to carry and shoot further accurately, especially when fired from horseback, than the long bow, were still inferior somehow, and were just invented due to the lack of decent bow-making materials on the steppe (yeah, and General Lee mistook shabbily-dressed Ulysses S.Grant for a blacksmith, and handed him his sword a Appomatix court house for Grant to polish!.   The solution?  Use the long-tailed soup spoon toli sticks to shoot white-hot, wind-heated charcoal-coated glans and set their bows on fire! YEEEEAH! 

Hey, how about this one...a compound toli stick for hundred-yard field goals every time!

But seriously...(which I seldom bother to be (serious, that is!) anymore, but here goes...) I believe that creative, and visionary thinking such as this idea, and others like it on slinging.org may result in a LARGE vartiety of new and unique tools, weapons and other useful inventions which may someday be remembered in history as having inspired many new and life-changing technologies, as well as an environment of intellectual freedom and mutual inspiration for those of us who occasionally find too much time on our hands.

lmao - good to see you back ts.

No idea what soup spoons have to do with this topic - assyrian or otherwise - but excess enthusiasm is probably better than none at all, and hey you never know. The bloke who invented cats eyes just wanted a way to get back from the pub while tanked up on misty nights - he changed the world for the better. Big ideas can have humble beginnings  :-)

And Matthias - wow - you made one and it worked, now I definitely want one :-)
75 metres with a tennis ball is pretty good they don't fly particularly far in general.

Dear Techstuf,

If it ever does take off to such grandiose heights, it will be thanks to members like you, Matthias, Tint, Aard, Lobohhunter and perhaps even little old me (part optimist, part curmudgeon), ....Underdog!     ...among several others.  It never hurts to encourage our people with some shameless, "magnumslinger-esque" cheerleading, however!  I really think that there are many here who could make it happen, intentionally, or otherwise.  Yeah, some significant inventions will probably someday be traced back to this forum, eventually!

Aardvaark!  How's it going?  I was refering to several posts where I tried to get/continue or stimulate discussion here by reeling off wild ideas, etc.  (It usually worked, thanks to you, and others who were kind enough, and/or at least interested enough to comment on them!  )  The "soup spoon"part  was a reference to the old pictures where it looked like the ancient Assyrian slingers were throwing stones from soup spoons, which I mused were more likely to turn out to be toli sticks, or Philippine bamboo stone throwers!  I left out that Irish-American wild Astrology-history-Egyptian-Biblical site you got such a kick out of!  By the way, here's a couple of sections from another interesting one with some similar references, but one that I enjoyed even more: 

http://www.theosophical.ca/Book12A%20-AncientEgypt.htm

http://www.theosophical.ca/Book4AncientEgypt.htm

There were no cool "ancient-solar-heroes-slinging-from-horseback-at-evil-giant" cartoon pictures, or even any fun "Prehistoric Irish mutant ninja druid-kings-as-unjustly-dethroned-masters-of-the-ancient-world" conspiraciy theories on this one, though! 

Feel free to either tear it apart, comment unenthusiastically, or praise it, as you see fit!  Either way, I think you'll have some good insights to offer, as usual!

Could the booster weight be more oval shaped or otherwise elongated in shape with the cord attaching on each end of it? I'd think it would be less likely to tangle that way.
 
     What about just drilling a hole lengthwise through a lead weight and using a piece of heavy guage wire bent into an eyelet at each end? Of course, this would prevent a series of weights for different weghted glans.

[quote]75 metres with a tennis ball is pretty good they don't fly particularly far in general.[/quote]
It's about as far as I can throw one comfortably with a standard sling. The motion feels funny - as the ball *shouldn't* go as far as it does...

[quote]Matthias, did the booster weight slow down almost completely in your tests?[/quote]
Pretty much - my masses weren't balanced, which I think allowed the booster to hit the release hook, stopping the outward motion and allowing it to retain more energy than it otherwise might. The speed was definitely cut to around 1/3 or less of the pre-release speed though. If the secondary doesn't fire for some reason the difference becomes very apparent. The sliding mass should basically adjust itself for maximum energy transfer: in a properly working compound, prematurely stopping the weight (not enough sliding room allowed) and releasing the secondary early (not enough time/arc allowed for the transfer) will be the main factors. You are always going to lose a little from the release point, unless someone comes up with an instant release that works at exactly 180 degrees. My sling is supposed to dump somewhere between 160-170, which is adjustable by the length of the trigger cord. Making the booster lighter relative to the thrown mass shortens the amount of sliding required.

[quote]...FunSlinger rasises a bunch of good points...[/quote]
Normally, I'd splice all the connections in a sling like this for smooth transitions, but whipping would work perfectly as well. The reason I left knots with long tails was that I wasn't certain that I wouldn't have to adjust everything.

I think possibly a more streamlined, organised booster FunSlinger describes might help with a fixed-position design. The booster I was using slides, which seems to be a big help, though with this trigger the fixed one might be manageable as well. Apart from the seeming automatic tuning benefit, the huge advantage is that it puts tension on the cords through the first moment of release, which makes the whole thing much more predictable.  I think that you could actually get away with a small pulley and snap-hook masses clipped on without worrying too much about tangling. The booster stays nicely out of the way of the whole process because it is being held outward by the slinging forces.

A plate/jigsaw-blade hook seems like a good idea (waterjet cut would be really nice - anyone have one in the garage?) One of the problems with the geometry I used is that the secondary retension cord interferes a bit with the hook - and the wire loops make it worse. Rather than using a single piece retension cord as shown, I suggest that a better design would use three holes in the hook, and break the cord at that point. This should help with the tangling a bit by keeping the hook straight and the troublesome crossing will be eliminated.

[quote]...Funslinger talks about compound-whip-slings...[/quote]
I have absolutely no idea. That could go in the simulator pretty easily though.  ...Thinking... hmm, I think I could see it working pretty well. Aiming would either be easy or really really hard. Who's going to build one for a real world test? I won't be back at the simulator until mid next week.

[quote]How are you holding onto the projectile when you swung your prototype?  Did you have any problems with dropping the ball before/during release?[/quote]
I just hold the pouch. No trouble at all with dropping, but I never drop anything with a normal sling either. The test sling uses a woven split pouch that I had left over from the tutorial I wrote a while back. It holds the tennis ball pretty securely. The trick with pouches is that you really want to hold the projectile with the outside edges if at all possible. Support it from the middle and it's apt to roll around.

Jurek's sliding booster fixes the release mechanics perfectly. What would otherwise be a pretty complicated manoever with potentially slack cords and unreliable timing becomes as easy as a standard release!

[quote]Could the booster weight be more oval shaped or otherwise elongated in shape with the cord attaching on each end of it? I'd think it would be less likely to tangle that way.[/quote]
It could (see FunSlinger reply). I'm thinking of going the opposite direction though, and using a pulley and maybe even a short length of cord to get it away from the sling (remember that the sling is folded through the working phase).  As complicated as the design looks, it is really easy to load and seems pretty tangle free. My main problems were cord twisting and tangling at the retension hook.

[quote]In your design, does the booster weight actually slide along the cord?  If so, what stops it?  Seems like it would tend to tear the cord at the release gadget.[/quote]
It does slide - you can see clear evidence of this in the photo if you squint. The sliding is what makes dropping the pouch work as well as it does, regardless of the contribution to energy transfer. As for stopping the sliding - It stops itself. Amazing but true! So long as it isn't so heavy that it can make it out to the hook before dumping the remaining energy, it stops sliding as the secondary reaches max extension. If you look closely at the second simulation I posted you can see the path taken by the mass, including the point where it has stopped moving (both outward and tangentially). In that sim, the secondary doesn't dump, so as it comes around past 180 degrees, it reaccelerates the booster and starts sliding it inwards at the same time...

The sling should be tuned so that the mass doesn't make it to the hook. In the test rig, I "think" I'm hitting, but can't tell with the speed everything unfolds at. Lowering the ratio of booster to thrown mass or moving the retention hook outward a bit more would both work. I don't think the second is necessarily a good idea though, as the shorter secondary would put bigger demands on the system.

Once the secondary fires, there is nothing to prevent the booster from sliding out to the end. A stop before the hook is a good idea to prevent trouble with this critical part. The further extension of the primary length after release is helpful though, as it slows what's left of the rotation down even more.

******

I look forward to seeing some Mark II compounds posted. Weekend's coming up!

Matthias

My impression with Matthias' first scheme with non-sliding booster weight is that this booster weight is not for boosting but for making the first string controllable independent of the second string. What would be interesting is a variant of a staff sling. Take e.g. a 70cm carbon fiber stick and attach a sling to that. The release could be some kind of remote compound bow release. The stick would be controllable thereby allowing a lot of different motions. Or it can just lengthen the arm. So that would be some merger of sling and staff sling.

But first I have to get my normal slinging working. (Btw. there is no flash plugin for Linux x86_64. So I can't look at the new member map.)

Zwiebeltuete

wanderer wrote on Mar 30^th, 2007 at 9:16pm:


Once they figure out how to make crossbows, the popularity of the sling diminishes fast. 

I think a crossbows are simpler than what we are trying to make on this thread.