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Discussion Starter #1
Maybe Jeorg can help here, there has been a long debate with contradictory "proofs" about fork width and speed, to my current knowledge in physics a narrower fork should be faster than a wider one at same rubber elongation (same stored energy) because of the cosine law. I currently have an accurate slingshot simulator and checked results against a rudimentary experiment

the wide forks 10"

input data --------------------
band fork width (cm)= 2.00
band pouch width(cm)= 1.80
fork width (cm)= 25.40
band lenght (cm)= 30.00
ammo weight (grams)= 4.00
pouch weight (grams)= 1.50
pull force (kgf)= 5.67000
band(s) per side = 1

output data -------------------
bands mass (grams)= 7.77503
elongation *** (cm)= 97.13847
elongation ratio = 4.23795
stroke (cm)= 99.32335
draw (cm)= 126.50257
ammo speed (m/s)= 80.34966 [ 263.61437(FPS)]
ammo energy (joules)= 12.91214
efficiency (%)= 60.26353


the narrow forks 2"

input data --------------------
band fork width (cm)= 2.00
band pouch width(cm)= 1.80
fork width (cm)= 5.08
band lenght (cm)= 30.00
ammo weight (grams)= 4.00
pouch weight (grams)= 1.50
pull force (kgf)= 5.70000
band(s) per side = 1

output data -------------------
bands mass (grams)= 7.77503
elongation *** (cm)= 97.18844
elongation ratio = 4.23961
stroke (cm)= 97.27080
draw (cm)= 127.16308
ammo speed (m/s)= 81.53529 [ 267.50422(FPS)]
ammo energy (joules)= 13.29601
efficiency (%)= 60.26353


so there is a little difference of 1.5% favouring narrow forks

the empirical data with the estimated average speed

2" fork width 79.11 m/s and 20" 77.86 almost same little difference of 1.6% which is very close to the numeric model

the setup used has a string to limit same elongation ratio

so my conclusion is there are almost meaningful differences on speed on a big range of forks widths
Arturo
 

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Nice post and good setup.

Please do another test with the string at the fork center for both pulls.

This test would mimic the fork to sighting position distance.

I believe that a wider fork is safer than the narrow fork because a broken rubber is not as likely to rebound directly into your face.

This is especially important in a powerful slingbow when the pouch is not very close to your face.
 

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Loudest boom on Earth
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looks very nice, what was your sample when collecting emp. data?I am surprised that efficiency is the same. How did you calculate it?
 

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Discussion Starter #4
Nice post and good setup.

Please do another test with the string at the fork center for both pulls.

This test would mimic the fork to sighting position distance.

I believe that a wider fork is safer than the narrow fork because a broken rubber is not as likely to rebound directly into your face.

This is especially important in a powerful slingbow when the pouch is not very close to your face.
if I put the restraining string at center the comparison will be useless (apples to oranges), the wide fork will store more energy and explaining any difference in speed as a property of the fork dimensions will be plain faulty, my intention was finding the REAL influence of forks width and seems to be negligible from 2" to 10" ...
Arturo
 

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if I put the restraining string at center the comparison will be useless (apples to oranges), the wide fork will store more energy and explaining any difference in speed as a property of the fork dimensions will be plain faulty, my intention was finding the REAL influence of forks width and seems to be negligible from 2" to 10" ...
Arturo

The wide fork would be less efficient because some of the force is to the side. The test is to see if the ~2" longer pull would overcome the efficiency loss.
 

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Discussion Starter #6
The wide fork would be less efficient because some of the force is to the side. The test is to see if the ~2" longer pull would overcome the efficiency loss.
I need to do another set of measures to check at equal draw (string tied at center), maybe in a few days ahead, the model predicts a very little difference for the 10" at same draw which cannot overcome the efficiency loss

input data --------------------
band fork width (cm)= 2.00
band pouch width(cm)= 1.80
fork width (cm)= 25.40
band lenght (cm)= 30.00
ammo weight (grams)= 4.00
pouch weight (grams)= 1.50
pull force (kgf)= 5.70500
band(s) per side = 1

output data -------------------
bands mass (grams)= 7.77503
elongation *** (cm)= 97.79989
elongation ratio = 4.26000
stroke (cm)= 99.98808
draw (cm)= 127.16730
ammo speed (m/s)= 80.87387 [ 265.33422(FPS)]
ammo energy (joules)= 13.08117
efficiency (%)= 60.26353

Arturo
 

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At the 'other forum' there has been debate about this where the people of more position & also moderating power, refute alternative views and have at times, locked topics on something which should be open for discussion ... but I am maybe going off topic!

It seems the 'wider forks supporters' were implying that they are automatically superior to narrow forks, however if there is any speed increase, it is so NEGLIGIBLE or very minor. IMO, one can optimize a catapult, such as one with narrow forks with best elastics set-up and shooting style technique that can give very good speed and accuracy performance. I would think, wider forks can have diminishing returns if you go too wide, such as difficulty holding and aiming the slingshot and accuracy may suffer?? Also, at other forums, they state wider forks maybe are very slightly easier to draw. Again, it seems that is negligible or very minor in overall picture.

For myself, I'm having more preference for narrower forks. When one draws a narrow forked catapult, it is almost similar to holding a rifle and makes pointing towards target easier which enhances the aiming/sighting. The PFS is one of the most narrowest forked slingshots and perhaps one of reasons it has maybe become popular.
 

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I suppose that one instance in which there might be a clear advantage for very wide forks would be for slingbows. As the possible length of draw is limited by arrow length then having forks wide enough to have no slack would be a plus.

Both Rattlin Randy and Badass slingshots seem to be working on these lines and I'm planning something similar myself.

Any thoughts on this before i start?
 

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There are several factors involved.

The wider fork has a longer elongation with the same bands, just because of the geometry. See my example of a 60 cm fork vs. a 10 cm fork. The bands of the wider fork will be stretched to 105 cm at a 100 cm draw length. If your bands are 20 cm long, then the wide fork leads to a stretch of 5,25 vs. 5,0.

The wider fork eliminates any dead play of the bands, in fact they prestretch the bands at this width. This results in a longer power stroke (100 cm vs. 80 cm) and also gives it more force.

But the wider fork also has a much less direct power vector. It is like two horses pulling a cart. If they go in slightly different directions, a certain part of their power is lost by pulling against the other horse.

These factors, to my experience, pretty much even each other out. That's why there is very little difference in speed.

It doesn't matter if your fork is 4 cm or 14 cm wide. The difference is so small that it won't be even measurable. Such issues are only affecting cross bow weapons where you can go REALLY wide with your fork.
 

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There are several factors involved.

The wider fork has a longer elongation with the same bands, just because of the geometry. See my example of a 60 cm fork vs. a 10 cm fork. The bands of the wider fork will be stretched to 105 cm at a 100 cm draw length. If your bands are 20 cm long, then the wide fork leads to a stretch of 5,25 vs. 5,0.

The wider fork eliminates any dead play of the bands, in fact they prestretch the bands at this width. This results in a longer power stroke (100 cm vs. 80 cm) and also gives it more force.

But the wider fork also has a much less direct power vector. It is like two horses pulling a cart. If they go in slightly different directions, a certain part of their power is lost by pulling against the other horse.

These factors, to my experience, pretty much even each other out. That's why there is very little difference in speed.

It doesn't matter if your fork is 4 cm or 14 cm wide. The difference is so small that it won't be even measurable. Such issues are only affecting cross bow weapons where you can go REALLY wide with your fork.

Great analysis.

It is the slingshot draw length that we shoot, not the stretch ratio.

You designed a self-cocking folding triggered slingshot. Nice!

Idea: Pivot and lock the fork to achieve a portable, climb the tree, easy carry, wide fork.
 

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And how does this experiment is understood through this data?
Bill Hays did not use the same draw length. He measured the length of the band as he had the rope attached to the fork arm, not to the center between the forks.

Also his draw weight readings have been so close to each other that the difference was not significant. Just 0,34 pounds, not even 150 grams. When you draw out a band, it loses draw weight so quickly because of the cooling effect that you can't reliably measure that precise.

If he would have drawn out from the center of fork, then the would have seen a much different draw weight because of the longer stretch factor. Simple geometry, as shown in my little sketch.
 

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At the 'other forum' there has been debate about this where the people of more position & also moderating power, refute alternative views and have at times, locked topics on something which should be open for discussion ... but I am maybe going off topic!

It seems the 'wider forks supporters' were implying that they are automatically superior to narrow forks, however if there is any speed increase, it is so NEGLIGIBLE or very minor. IMO, one can optimize a catapult, such as one with narrow forks with best elastics set-up and shooting style technique that can give very good speed and accuracy performance. I would think, wider forks can have diminishing returns if you go too wide, such as difficulty holding and aiming the slingshot and accuracy may suffer?? Also, at other forums, they state wider forks maybe are very slightly easier to draw. Again, it seems that is negligible or very minor in overall picture.

For myself, I'm having more preference for narrower forks. When one draws a narrow forked catapult, it is almost similar to holding a rifle and makes pointing towards target easier which enhances the aiming/sighting. The PFS is one of the most narrowest forked slingshots and perhaps one of reasons it has maybe become popular.
One thing I would never do is go to another forum and then proceed to trash everybody on a different forum. It's just a very low sort of behavior.


The reason I did any videos showing the narrower is faster myth is in error is because Dgui kept insisting the PFS is the fastest most accurate frame you can use... He said it is so because narrow forks are far faster than wider forks and when you also add an immediate release, you can achieve speeds of over 50% faster versus the larger traditional frames.
All of this I was willing to overlook, but then Dgui was commenting to another poster that when I do my shooting and stuff that I am manipulating my results for the purpose of selling slingshots.
He outright called me a liar.

So I did some simple tests to show that what he is saying is completely in error and after insulting me personally a couple of more times in PMs and in public forum... I simply fought back and he did end up leaving the SSF.

You should realize something... I am blessed with a high IQ, I also have a real understanding of the math behind it all as well... but what I had to do was try and design an experiment that is simple to understand and that anybody with any real interest in the subject could replicate themselves.

These videos are the result of that:

Since people tend to draw to the same anchor point as opposed to merely a stretch ratio, ths first video shows exactly that. Wider is faster no matter what width (within reason) is chosen.

Wider (3"-24", standard to extreme) shoots about 10 fps faster than narrow (1" gap, pfs size).
[ame]http://www.youtube.com/watch?v=4aSZHbxagmg[/ame]

Some then argued that people cut bands to a particular elongation ratio and not for the same anchor point... so I then showed that to shoots faster with wider forks.

You can get up to about 10 fps more from wider forks, in this video several shots per width are done to eliminate any chance of anomaly:
[ame]http://www.youtube.com/watch?v=ajb9IQ_HTxs[/ame]

After that, we had some who insisted that "sure wider may be faster, but it comes at the expense of more draw weight."
That is also not true.

Draw weight for the same elongation ratio is actually less when using a wider fork as compared to a very narrow fork. When going to the same anchor point the draw is almost exactly the same. This scale locks at peak weight, I waited to make sure peak was locked and then showed the result. After the video I did this a few more times and the results were almost identical:
[ame]http://www.youtube.com/watch?v=x91fgAlI2j8[/ame]


So, why does any of this matter?
We all push for the smallest increases in speed versus draw weight... for example I personally buy and use medical grade latex instead of theraband gold because it's about 10 fps faster using the same cut.
We use small efficient pouches to cut down on weight. We use a longer draw to accentuate speed.... etc etc....
So when someone, ANYONE, says you can get a lot more speed by simply going to a narrower fork.... THAT needs to be tested.
It was tested, and it was shown to be a myth.

Wider forks have less slack (dead play) which creates a longer acceleration cycle versus narrow forks... and that overcomes the fact that latex is actually more efficient in a direct linear usage.
It really is that simple.
 

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Discussion Starter #14 (Edited)
Here is the detailed math and verification measured data on why narrow forks are more efficient than wide forks at the same STORED ENERGY regardless the acceleration length. My empirical results are in total accordance on what physics states, there is no way for a wider fork to be faster than a narrower fork provided the SAME ELONGATION, SAME BANDS.

the pictures shows
1) the differential force vector diagram. It's easy to understand that the force vector 'fy' doesn't contribute to ammo acceleration, in the wider fork 'fy' will be bigger and 'fx' (which is the acceleration force which is converted in speed) will be smaller.
2) the work (energy), the analytic solution for this integral is quite complex to resolve so it's better to represent it as a series to allow numeric computations
3) transformation to discrete computable model
4) maximum efficiency, in the series expansion each term is a force multiplied by the EFFICIENCY which happens to be the COSINE of the instantaneous angle at that term, so regardless the force function F(x) there is a limit to maximum energy that can be transferred, for the same F(x) a wider fork will always transfer less energy that can be converted in speed than a narrowed fork.
as an example in the setup used to record my measures 10" is 0.979 and 2" is 0.999 even the 2" has 2.71cm more slack than 10" still more efficient (anyway the "slack theory is a myth" at the same elongation), of course the efficiency in the real world of both cases will drop due the rubber and pouch weight and the rubber retraction speed limit so not all stored energy will be converted in speed.

the empiric verification, was done recording the time from release to target, the resolution is 1.17 mm/m at 44,1 Khz better than 1% of most crony's
data:
2" WIDTH

RELEASE TARGET TIME(milliseconds)
.990814 .813333 177.481
1.096525 .918298 178.227
1.120219 .943431 176.788
.360495 .183387 177.108
.621421 .444687 176.734
1.045134 .870318 174.816
.659204 .482683 176.521
.297671 .12155 176.121
.992605 .814805 177.800

176.844 average

10" WITDH

RELEASE TARGET TIME(milliseconds)
.365692 .187499 178.193
.201611 .021416 180.195
1.087663 .907171 180.492
.616584 .436735 179.849
1.030868 .852997 177.871
.374933 .195405 179.528
.215364 .035465 179.899
.257518 .080314 177.204
.647578 .468941 178.637

179.096 average

so the results are in total accordance with theory, the wider fork is a bit more slower (.987425) very close to my simulator results. Now as I said before the differences on practical forks are so small that for the real shooting are meaningless, I've did this analysis for the sake of rigor, "wider is faster" as a sole geometric property is plain wrong, faster regardless width is simply more ENERGY.

final thoughts, I knew before any experiment that narrower forks were in theory faster than wider forks at SAME ELONGATION because of the COSINE LAW, less efficiency means less energy transfer and less energy means less speed, that's an unavoidable truth known from centuries (Newton), if "angled forces" were more efficient many mechanic devices would look quite different today, crane pulleys an many others which not happen.

Mr. Hayes I am quite intrigued with your second video results, I have repeated this experiment 3 times and never got such results, also didn't understand what you explained about "it doesn't matter the force direction" because that is precisely what matters, if this experiment delivers contradictory results that violates Newton second law, something is wrong with your experiment.

Arturo
 

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Wider forks have less slack (dead play) which creates a longer acceleration cycle versus narrow forks... and that overcomes the fact that latex is actually more efficient in a direct linear usage.
I actually agree. I just believe that the speed increase you can actually achieve is very small, especially if you keep the fork width within the acceptable range for hand held slingshots.

Of course the different acceleration cycle comes at a price. You have to invest more physical work in order to get more energy for your shot. So you only get more shot energy if you set up the bands for the same maximum draw weight. If you go for the same amount of physical work invested, I agree with Arturo, then the more narrow fork probably works better.

Is it bad style to bring a discussion to this forum that started elsewhere? I don't see it. Here, people can discuss whatever they want. As long as it is polite, it is OK with me.
 

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I actually agree. I just believe that the speed increase you can actually achieve is very small, especially if you keep the fork width within the acceptable range for hand held slingshots.

Of course the different acceleration cycle comes at a price. You have to invest more physical work in order to get more energy for your shot. So you only get more shot energy if you set up the bands for the same maximum draw weight. If you go for the same amount of physical work invested, I agree with Arturo, then the more narrow fork probably works better.

Is it bad style to bring a discussion to this forum that started elsewhere? I don't see it. Here, people can discuss whatever they want. As long as it is polite, it is OK with me.
Another thought: Are wider forks on a slingbow safer because the pouch is not in your face?
 

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One thing I would never do is go to another forum and then proceed to trash everybody on a different forum. It's just a very low sort of behavior.
I dont see how he trashed anyone... Maybe my lack of English vocabulary is the reason for this? I dont think so.

I am with Arturo on this. Math is math. An experiment is only valid as evidence if the sample is substantial and you can eliminate all variables that exist in an uncontroled enviroment.

Last week I read a interesting trivia fact about Stewen Hawking. After he was asked what his IQ is, he responded that he has no clue and people who boast with their high IQs are loosers( or a similar word I dont remember ).

I dont wanna insult anyone here at all, it just sounded funny when I read your post that you wrote you re blessed with a high IQ Mr. Hays, nothing else. No offense meant.
 

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First of all, I said it is a low behavior to come to a different forum and trash members of another forum, and I referred to "ZorroSlinger"s post. I speak English pretty well and do understand what he is saying perfectly.

Second of all, I dropped out of MENSA when I was 25 years old (half my life ago) because everything was about IQ and not about what was accomplished with their gifts... basically meetings were big bragging sessions and a lot of snobbery... In other words, there's been many in this world far less gifted who have accomplished far more... plus I had far different interests than pretty much anybody else there.
You all can see how I dress and how I act in my videos and so forth... that's me in my for real everyday life, I do not put on airs of superiority at anytime and I did not mention what my IQ is, only that I'm gifted so as to make sure you don't think you need to talk down to me... I am capable of comprehending whatever you would like to throw my way.
(I do have some funny stories about all of this, but that's for another day)

Third of all, there is no audio program that measures as well as an actual calibrated chronograph does.. so any measurement taken that way will automatically be taken as questionable. I have all the most popular audio programs and they are all vastly inferior to the actual chrony... heck, in the past I've even done videos comparing one, the most popular, two side by side with the chrony.. and it showed that the chrony was consistent but the audio version was only consistent UP TO 5% over a series of the same measurements.

I've been very careful to show exactly what I did on video and I do not see any area that I may be overlooking... wider is faster, NOT SLOWER.
Arturo, you originally jumped into the argument to come to the aid of your friend Dgui... that is admirable and completely understandable... but regardless of whatever measurements you can come up with, you cannot argue with what I CLEARLY and conclusively show in the videos. Wider is faster.

Notice something, I'm not saying wider is better... personally I find very wide slingshots to be cumbersome and not fun at all... but the point I made and then proved is that PFS slingshots are NOT superior to standard slingshots in ANY way other than being more concealable. Which is exactly contrary to what Dgui was loudly vociferously proclaiming on many occasions.
Occasions like when he did and even still does continue to claim a PFS is far faster than it's larger counterparts simply because it's narrow and therefore far more efficient.... which is simply not true by either Arturo's measures or mine.

So my point is made regardless... if we go by Arturo's measurement on an audio measuring device... narrower is only the very slightest amount faster. Or if we go with my measurements using an actual calibrated chronograph... wider is a little faster than narrow.
Again, either way... you are NOT going to pick up 30% more speed by shooting a PFS instead of a more traditional sized fork, which happens to be the original claim put forth.
 

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Discussion Starter #19
Mr. Hayes, yes I backed my friend dgui, after he followed some of my observations to let him show clean and clear his points about "active shooting" thing that I don't practice, that's another stuff from the past and better let's put it aside from this topic.
My objection is only with the second video at constant elongation, same experiment I've done, maybe at constant draw the wide fork has a slight advantage because it stores more energy enough to overcome the slightly less efficiency, and no one can dispute that more energy is the only source to obtain more speed.
I knew and also tested almost all audio programs and I agree that those things are toys and cannot compete against optic crony's so I don't rely on that gadgets. The audio tape was analyzed by me and that's why I've shown only the ELAPSED TIME with enough resolution (1.1mm/m) to obtain very precise time measurements as good as standard crony. The only difference is I don't compute an instantaneous velocity but it is clear that less time means more speed. In the audio file the little spike at 1 is the release, it happens to be very sharp and narrow, the last noise burst at 2 is target impact, both very precise indications. My objection is that you took few measures with a relatively high spread and that is an indication that are some random variables not fully controlled affecting results, finally I've done the experiment early in the morning to be sure of a constant ambient temperature during measurements.
For the stopping string I've used a very rigid YUTE string hooked in my index finger and same 2nd knuckle (same finger holding the pouch) to be sure almost equal elongation (maybe the paracord is a bit more elastic ???) and maybe hooking in your middle finger makes it more variable, honestly I don't know, just speculations on what could happen with your experiment ...
My experiment just confirmed physics principles that are out of any doubts that must be complied ... but again the differences over a wide set of fork widths are meaningless in real world shooting, better choose what is more comfortable for your hand and style ...
Arturo
 

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That's all well and good Arturo, but you see light is faster than sound... so the chrony will have a more precise reading given a faster sampling rate... which it does have as well.

Wider is faster because there is a longer period of acceleration... which is also why I called you out a long time ago when you were showing active shooting versus "static" shooting... and you were merely using a longer draw on the active shooting, as shown in your video.

Also, I already thought of the middle versus forefinger and used the forefinger in the following video to confirm my previous ones. In this video the paracord literally touches the back of the pouch at exactly the same spot on every shot when at full draw:

[ame]http://www.youtube.com/watch?v=yaKvJRp41As[/ame]

I do this stuff on video so each part of the whole is clearly visible... feel free to refute all you want but it is undeniable that no matter how I do it... wider is proven to be faster when using small sample sizes or larger sample sizes... cool days or warm days, close to optimal draw or less than optimal, elongation ratio or to an anchor.
Wider is faster.

Again, I honestly don't care... if the two are even close it proves my original point and that was that Dgui could not be getting 30% more speed by simply using a narrower fork.. which happens to be the original claim. Afterwards the claim was amended to "active shooting" gives up to 30% more speed, at which point you decided to weigh in with your opinion and video which was proven to be in error because of the draw length issue.

I don't sit by and suffer insults to my integrity very well. I do everything above board, I use my real name, I show my real data, I try to help people when and where I can... so when someone, anyone, calls me a liar... I take that as an insult and an invitation to do something about it... which is what I did.
 
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