Flight shooting machine

Kviljo · Post by **Kviljo** » Sat Sep 05, 2015 8:58 am

Youtube video:

https://youtu.be/i7T-_RxSDIU

As a last test of the turkish composite bow before thinning the kasans, I shot it for flight with the shooting machine. It turned out I had set the machine to shoot without any overdraw for most of the arrows. It released at about 25 inches, where the point of the arrows were just beside the handle. The attached siper does also need adjustment, as it scraped off one of the fletchings on several of the arrows. One of the arrows actually went 345 meters with only two fletches, while the best went 351 meters with three.

This is the same bow that shot 392 meters at the competition last year. This year it shot 375 meters in calm and flat conditions.

Now I will finally adjust the tiller somwhat, and thin the horn on the kasans as much as they allow for. Should make it a little lighter, but I bet/hope it will shoot faster.

Adam Karpowicz · Post by **Adam Karpowicz** » Wed Sep 09, 2015 12:09 pm

Great idea Ivar with the pulley and the foot drawn set up. i am tempted to modify my old machine for something similar - easy and light to carry in the fields. One thing that I would do: mount the bow horizontally as a crossbow rather than vertically. That way there is only up-down flapping of the arrow, no side-to-side plus up-down as it is now.

I am not surprised the machine shot arrows fly lesser distances than hand shot. I have had the same problem - the machines are rigid with not enough give to buffer the impact of the arrows on the siper (more on that in the sec. edition of my book). The best machine could be a rubber one (or better yet - flesh!).

Adam

Kviljo · Post by **Kviljo** » Thu Sep 10, 2015 10:13 am

Thanks!

When I designed the machine I wanted it to replicate hand shooting as closely as possible, as I was curious to test the siper with it. Now I just need a highspeed camera to see how the arrow passes the bow. It looks like I have found the best position for the siper now, but I'm sure there would be something to learn from some highspeed footage.

When mounting the bow in the machine, I first found the pressure points from the hand and thumbring and also marked the nocking point on the string. This way the bow is drawn exactly the same as by hand. The release mechanism is also somewhat simulating a thumb release, where the string is just pushed off a ledge to the right. It would probably be more optimal mounting it as a crossbow with everything in the middle, but...

It would be cool to make the front part of the machine out of something that would compress perhaps an inch if loaded with 100 pounds. Steve Gardner mentioned that he repeatedly could out-shoot the shooting machine.

How are you sure that the impact between the arrow and the siper is a big problem in the machines? Trying a few different placements/angles of the siper, I feel like the one that I have in this second video is letting the arrow pass quite smoothly. If the bow is set up vertically as if hand held, and the arrow is nocked a little higher, the siper would nearly just function as a way of holding the tip of the arrow before release. And then when released the arrow would lift up from the siper and not touch it at all. That's what I am aming for at least.

Yesterday I did a follow-up on the last shooting:
https://www.youtube.com/watch?v=DiFDK3tp71M

Having reduced the bow from approximately 65#@25" to 53#@25", and thinned the horn on the kasans, it went from shooting 350 meters to shooting 370 meters from a 25" draw. That's reducing the draw weight 12 pounds and adding 20 meters! Obviously dead weight in the kasans is hugely important on these bows

At the end of the test I also shot three arrows at about 27 inches, which gave a best of 399 meters.

jiao · Post by **jiao** » Thu Sep 10, 2015 2:18 pm

can you post some pics ? youtube and facebook can not look in china

Kviljo · Post by **Kviljo** » Thu Sep 10, 2015 4:53 pm

Ah, that's too bad, Jiao. Here is a picture of the shooting machine and the bow:

Adam Karpowicz · Post by **Adam Karpowicz** » Thu Sep 10, 2015 11:30 pm

I am glad we are both folowing the same path of thought. Bear in mind the arrows shot from a low weight bow are still acting stiff enough for good clearance.

Once you get to heavier bows, above 90-100lb for the "real" distances, the problems of mismatch between the arrow spine and the bow's weight begin to show.

Adam

Kviljo · Post by **Kviljo** » Fri Sep 11, 2015 7:21 am

I bet it does. The arrow that went 399 meters is 241 grains... The next best at 188 grains. Shooting the 188 grain one with double the weight should be a trial. Lately, with breaking the back part of the arrows, I have started seeing that they (the old competitiors) must have focused their training on having a super-clean release to be able to shoot arrows that we would generally consider hugely undersized today. Or, they had access to incredibly dense arrow material [and that the stiffness of the old ones have degraded], or, they were not shooting the 5mm-thick-in-front-of-the-nock arrows out of 100#+ bows.

But, don't you think that your problems with mismatch with the arrows (I have not read your flight-chapter yet) could be at least partly solved by mounting the bow vertically, and using a siper in the traditional way? What this does is place the tip of the arrow about 1 cm from the side of the bow at full draw, so that there is already good clearance against the grip. Of course, the push of the string would not be in the plane of the arrow to the same degree, but there would be better chanses of good clearance.

Adam Karpowicz · Post by **Adam Karpowicz** » Fri Sep 11, 2015 9:43 am

The tests I have done so far were all with bows mounted vertically and filmed at slow motion.

Horizontal mounting will reduce the arrow issue to up-down movement only. I am going to try that once the fields are hayed.

Adam

jiao · Post by **jiao** » Fri Sep 11, 2015 5:16 pm

thanks for pic
make a big turkish crossbow is good Idea

Pat Menzies · Post by **Pat Menzies** » Sat Sep 12, 2015 9:11 pm

Adam, still no word on how Joe Gibbs made out with your heavy bow?

J Menna · Post by **J Menna** » Tue Sep 22, 2015 9:02 am

What a nice shootign machine Ivar! Sound is good when you draw.... Just thinking, is the relase soft enought for bow...? It wont harm it, I mean?

Have you try target shooting whit machine? Would be interesterd to compare arrows to each other. Little different things between arrows could give lot of information.

Bede · Post by **Bede** » Wed Sep 23, 2015 11:29 am

When shooting with a siper, the arrow usually passes the bow with only a few millimetres clearance rather than a whole centimetre. Wear on old sipers suggests that the arrows do not travel straight along the groove.

Looking at the machine, I wonder at the distance between the nock and the catch used to hold the string. The usual position of the nock is just above the thumb ring by about 5 mm.

Bede · Post by **Bede** » Wed Sep 23, 2015 11:47 am

Reviewing the YouTube videos, I think that the machine is replicating the points I made above.

Rigid fletching like parchment limits how close the arrow can come to the arrow pass. Arrows I have seen with parchment fletching show no damage to either hen feather. Since they had names written on them, I assume they were used. The writing went down from the fletching onto the shaft showing that they were not added before the parchment fletching was affixed.

stm2010 · Post by **stm2010** » Mon Jul 11, 2016 8:18 am

Hi Bede, do you think this shooting machine will be the Chinese Sony dynasty's Shenbi Nu (Divine armed crossbow) type ?

Shenbi Nu used during the Song dynasty, said to be invented in the 11th century.

Its supposed statistics.

Bow span - 98cm
Length - 140cm
String length - 77cm
Effective range - 150m
Maximum range - 370-460m

It was said to be able to pierce straight through the double layer of iron lamellar worn by Jurchen heavy cavalry.

Kviljo · Post by **Kviljo** » Fri Aug 12, 2016 10:02 pm

Bede wrote:Rigid fletching like parchment limits how close the arrow can come to the arrow pass. Arrows I have seen with parchment fletching show no damage to either hen feather. Since they had names written on them, I assume they were used. The writing went down from the fletching onto the shaft showing that they were not added before the parchment fletching was affixed.

Ah, I see I have not been visiting this place so often... Sorry for the year-long delayed response

That's a very good observation, Bede! I got hold of some flight arrows too, with parchment, and none of them show any sign of having touched the handle of the bow either. I suspect only the front 15cm of the arrows touched the siper groove. The rest must have gone clear of everything.

I want to modify my shooting machine to apply some torque to the handle, to let the arrows pass better than in the current configuration.