The DeeperBlue.net Gun Building Extravaganza - Gun Options 5 - Track Options

[Stephan Whelan]

The 5th poll on the DeeperBlue.net Gun Building Extravaganza.

Do we want a conventional flush track or do we want a recessed track.

[ILDiver]

First to vote! whoooohoooooo! What does that get me?

I voted recessed. I would hope it fights the vibration of the bands and help the barrel slip through the watter better on side to side movement.

[blaiz]

Maybe this has been discussed but I think I missed it. IF so point me in the right direction and if not any thoughts?....

Will the recessed track cause a problem with the bands when fired?... by this I mean as the bands are released and proceed to pull the shaft forward will teh bunching of the bands inside the track cause any friction or other problems?

I really like the idea of the recessed track but before I vote I want to know if anyone has thought about this yet.

[ILDiver]

There is another thread where the shape is discussed, but it can be discussed here again. The recess would prolly be wide enough to allow the bands to come back to size. Then they would be exposed at the end, since tha barrel has a taper too. So from the side you would see 12 or so inches of the bands from the muzzle back. (the 12" is just me guessing).

More POV's can be found here: http://forums.deeperblue.net/spearo-...gun-shape.html

[blaiz]

Thanks Chris,

It seemed to slip my mind what we were building the gun with a tapered stock. I really do like the idea of the recessed track.

[Pastor]

It has been discussed but this looks like we now get to make a decision. By the look of it this has little to do with the shape of the gun but more to do with getting the track cut and the trigger fitted.

[Jonny250]

If you use the recessed track then i think you reduce the vertical stiffness of the gun quite significantly - if that might be a problem? in the image of the 2 tracks the effective thickness (for stiffness) is about 1/4 less on the recessed track, so 0.42 x the stiffness...
I like the idea of the enclosed the track for hiding the bands - reducing that vibration when you track sideways...

[Marwan]

i voted recessed, not that i feel that the vibration will be bad on a single 90, but hey its a special gun we are building so i went with the "new" feature...

[Mongrel454]

I went for recessed also, for no other reason than just preferance

[Lockedin]

Jonny - instead of thinking of it as 1/4 less material in the center, I thought of is as having a bit more material on the sides (though there probably will be a bit less in the center - GITS?)

Would the band need to be completely hidden to eliminate vibration?

And what is the diameter of the band when stretched - how deep will the recess be?

[ILDiver]

Originally Posted by Lockedin

Would the band need to be completely hidden to eliminate vibration?

I thought that too, maybe it would not have to be full depth. But if your going to go there, go all the way? a 19mm band fully stretched on a 90cm gun ends up at about... 12mm - 14mm I think. I would have to measure it to be certain. How tall was the gun? I'd have to look, wasn't it 20cm? Once reshaped though.....

[Pastor]

20cm? You've confused me there bro

[ILDiver]

The dimensions of the uncut blank for the gun.... I could not remember. And cm is a bit much mm maybe, me and the metric system.... I should have taken more time before I posted. I could not recall the starting point. 50mm x 50mm x 1500mm. I knew the length, could remember the height.

So if it is made to an oval shape, we lose material in the height a little. If it stayed at 50mm, the band channel could be 10mm and you lose 1/5 of the barrels strength. But changing the shape of the barrel, I'm not sure what the effects are.

So as far as the channel covering the entire band. I don't thing it would have too. And I'm not sure it can once the gun is re-shaped to be oval (If that is the shape it will be).

It's a little hard for me to visualize the gun and "if" it will all work out. Starting with a 50mm square and going to oval, seems thin to me. I looked, but can't find it at the moment, for the dimensions with the taper.

[foxfish]

I wonder if I asked the Gits if he could build some sort or prototype out of soft wood or something, he might have more idea if a recessed track would be feasible?
I would be worried about the necessary dimensions, might be a bit big for a 90 euro?

[ILDiver]

If I had a copy of AutoCAD still, or a 3D modeling program....that would be the way to go...

I think with the dimensions we we started with, 50mm x 50mm, that is not wide at all for trying to notch out. Then trying to make it oval, makes it even tougher. How tall is a normal wood gun? I'm used to a Cayman that has an inner diameter of 25mm and it is plenty stiff. I don't know what thickness the wood has to be.

Maybe a half oval for the bottom and a flat top, with enough recess to make the bands 1/2 or 2/3 recessed?


*****Added 2 more rough ideas. The grid is 5mm squares.*****
*****Recesses may not be deep nor wide enough, but this*****
*****Should give you an idea of where I'm coming from *****