Shooting low..

[willstroo]

https://www.youtube.com/watch?v=1pnd2osl5nQ

I just realised that I have this video of the gun firing low.

Since this video the enclosed track section has been added at the back, and a pulley system was installed to crank the rubbers up past what i could load it. But this video is pre both of these things. Here is the gun:

http://www.spearboard.com/showthread.php?t=173125

Can anyone see in the footage why it would be firing downward so significantly. It looks like the shaft is almost bending..? Does that mean the point was already aiming down when the trigger was pulled, i mean below the level of the tail?

Totes cant get my head around it..

Anyway, im changing to a double roller, which will be using significantly smaller "rollers", which hopefully will have the bands guiding the shaft down the barrel more with more force downward, as the point of the rubber where it comes over and off the roller is lower on the muzzle now.

Any help is great

[2fishin2]

Are you using a target or just shooting into nowhere land and coming up with these observations? And I see a bunch of recoil going on with that gun.

[willstroo]

Originally Posted by 2fishin2

Are you using a target or just shooting into nowhere land and coming up with these observations? And I see a bunch of recoil going on with that gun.

There was "yakkas" (a small fish), in the distance which I was shooting at. Its clear in one of the videos, we killed one and then shot at the carcass.

You don't agree looking at the footage, especially the last clip, that the shot is going low..?

[2fishin2]

Honestly I cant give an opinion unless you get in some calm water and set up a target to shoot at. Your videos dont show anything to me except you shooting into open water. And your gun looks to have some serious recoil going on.

The target is very easy. Grab you a 1kilo weight, tie it to a small soda bottle that you have marked with some sort of target block and shoot away.

[isotopez]

If the diameter of your rollers make it such that the band is higher than shaft, when the band makes the turn on the roller it will pick up rear of shaft via the wishbone on sharkfin.

That's one of the things that looks like is happening to me

Edit: looking at pictures of it the diameter of your rollers seem to put bands in line with shaft. Chalk it up to another wonderful how do I fix this roller gun problem haha. Hmm...

[willstroo]

Originally Posted by isotopez

If the diameter of your rollers make it such that the band is higher than shaft, when the band makes the turn on the roller it will pick up rear of shaft via the wishbone on sharkfin.

That's one of the things that looks like is happening to me

Edit: looking at pictures of it the diameter of your rollers seem to put bands in line with shaft. Chalk it up to another wonderful how do I fix this roller gun problem haha. Hmm...

Yeah that's what I'm thinking too..

The new rollers are probably 10 mm less diameter, so that will eliminate that problem at least! Will be a double 16mm roller with a pulley tightening, should have enough power to rule out under powering as well.

Thanks for the help

[isotopez]

Here's another thought. As shaft is accelerating out of gun and wishbones slide up over the muzzle bridge, if the shaft is much lower than the top of bridge it may be picked up. So what I'm saying is a smaller diameter shaft could get lifted up when the shaft reaches the muzzle bridge because the wishbone on shaft is lower than height of bridge.

[willstroo]

Originally Posted by isotopez

Here's another thought. As shaft is accelerating out of gun and wishbones slide up over the muzzle bridge, if the shaft is much lower than the top of bridge it may be picked up. So what I'm saying is a smaller diameter shaft could get lifted up when the shaft reaches the muzzle bridge because the wishbone on shaft is lower than height of bridge.

Yeah thats also possible, but it looks like the damage is being done before then, like its shooting down as soon as the trigger is pulled.

Thats what it looks like to be anyway.

Home made guns are cool, but holy crap the people that produce these large scale are talented to get them working right!

[Pankrationist]

I have only looked at the first video at this stage but between 24 - 27 second mark it looks like the barrel is flexing a lot. What barrel have you used?

[willstroo]

Originally Posted by Pankrationist

I have only looked at the first video at this stage but between 24 - 27 second mark it looks like the barrel is flexing a lot. What barrel have you used?

This one:
DMart Apex Carbon Rail Barrel
Item No: CBRL-H140

http://www.speargun.com.au/barrel/index.htm

[Nanna Arms]

Handle position is very low on the stock. Barrel also looks to snap back to shape once shot. What diameter is the shaft?

[Pankrationist]

Most, if not all of the products sold at D-Mart are Chinese knock offs. When I asked for the specification including deflection rates of the barrels communication stopped completely.

If you grab your muzzle and try and bend it does it feel like there is bending that you van notice?

When you watch your vid can you see what I am referring to?

[AJP]

Really hard to tell if the barrel is actually flexing while the whole gun is turning - appears to be though...

[willstroo]

Originally Posted by Nanna Arms

Handle position is very low on the stock. Barrel also looks to snap back to shape once shot. What diameter is the shaft?

I hadnt considered that.. The shaft is 8mm

[willstroo]

Originally Posted by Pankrationist

Most, if not all of the products sold at D-Mart are Chinese knock offs. When I asked for the specification including deflection rates of the barrels communication stopped completely.

If you grab your muzzle and try and bend it does it feel like there is bending that you van notice?

When you watch your vid can you see what I am referring to?

Ill try bending it tonight, and see what happens. I can kiiiind of see it in the first vid but i dont know if its my hand twisting. I cant really see it in the other ones.

God if the barrell is flexing then making it a double roller could be dangerous..