roller gun questions.

[scallywag]

I'm playing with the idea of making a roller gun for my next build.
Two questions:-

1, Is it ok to use a notched spear or are sharks fins better for a smooth release?

2, Can the bands be in a fixed position under the barrel or must they be "hooked" onto a fixing or is either ok?

I've got all sorts of designs in my head but just need these points clarifing before I make a start.

Thanks in advance.

 

[lawstraljan16]

You can have them fixed if you'd like but I don't see the point. When you're not using the gun you would want to unfix the bands so they don't stretch out as fast. Even having a few fix points would help to load the gun.
Also, I don't think the shaft being notched or having a fin would make much difference, just a notched shaft would have less strength IMO due to it being thinner where the notch is. Rollerguns are quite powerful but as I said I don't think it'll have much difference.

When I get home I'll post you a link about rollerguns. Rollerguns tend to have a low trajectory and this article says that he has the solution to 'rectify' the problem. It did seem as if it would work but I didn't try it myself, but as I said it looked like a solid idea.

Hope I helped a little at least




Sent from my GT-N7100 using Tapatalk 2

 

[-Paddy-]

I'm using a notched shaft on my Imersion custom roller speargun and a shaft with pins on my midhandle woody and it makes no difference to me.
Although I prefer the one with pins/shark fins as the shaft is stronger and it is easier to hook the wishbone on it.
Both my guns have fixed bands at the bottom and I find it very comfortable to use especialy when night diving. I have no pretension on the bands so I don't have to worry about stretching out when the gun is not in use.
Having hooks in few positions would allowe to change the tension/power of your gun.
Here are some pictures of my builds. I'm finshing this weekend a roller speargun for my buddy which will have hooks in 3 positions for the bands and a shaft with shark fins.

 

[scallywag]

Thanks for your answers. What I was keen to avoid was either having a protracted loading sequence of having to go from notch to notch above and below the gun and also having the bands flapping about after the shot. I think I've got it straight in my head now what I'm going to do.
First step will be to get the apprentices at work to machine me up some aluminum rollers!

 

[foxfish]

If I were to make another roller gun I would not try & make a lightweight short gun because it is very difficult to counterbalance the roller mechanism.
I would definitely make the most of the potential band stretch as possible & in my mind this requires at least two loading sequences.
Setting the handle in a forward position will help to counterbalance the rollers but I would still be looking a meaty stock & 1.2 length.
The idea of the band still producing power right up to the spear exiting the gun means a long stretch to grab the band when loading so I cant really see how you can avoid the two part loading & still get the max benefit?

 

[scallywag]

I suppose for me its not about maximising energy potential more about adding a different style of gun to my collection. Its going to have an 85cm rail length, aluminium rollers and carbon fittings so I hope I can maintain a degree of balance.

 

[-Paddy-]

Scallywag I'm not sure about making rollers out of aluminium. The surface will start to corrode in salty environment, to avoid it you would need to anodise them but this again will leave you with a rough finish. Maybe there is an other way of protecting it from corroding, I don't know. Also you will get high friction when spinning them on stainless steel shaft and lots of unwanted noise. It is not the case if you are going to use ball bearings but this will add weight to your muzzle and will cost you more.
I'm making my rollers out of acetal, it is easy to machine and you can get a super fine surface finish. It has also very low friction factor so you can drive it directly on you shaft without bearings.

 

[scallywag]

They would get a colour anodise so corrosion wouldn't be a problem and they would have a smooth finish. I'd probably fit a nylon (or similar) sleave to the spindle hole to aid the free running and reduce the risk of a reaction with the stainless axle.

 

[foxfish]

you can buy several purpose roller heads now but when I built this little one I used a roller set up from the local boat chandlers normally used on sailboat rigging.... lovely delrin rollers set on ss bearings for about £20.
PS crap muzzle heavy gun it turned out to be!

 

[scallywag]

Luckly I work for an engineering company manufacturing aircraft parts so I have access to all sorts of materials and machines. I've no intention of making a muzzle heavy dog of a gun!

 

[foxfish]

Cool... only trying to helpful mate!!!
I am really looking forward to your project - I like all gun builds

 

[scallywag]

I'll probably end up spending hours playing with it only draw the same conclusions as you have! Its the whole build process I enjoy. To be honest I was going to PM you to ask my questions as I doubded that I'd get any response on the open forum but I'm glad there are other active builders out there willing to get involved, thanks to all. I'm going to wait until after summer has gone berfore I make a start and will try to post progress as I build.

 

[scallywag]

Luckly I work for an engineering company manufacturing aircraft parts so I have access to all sorts of materials and machines. I've no intention of making a muzzle heavy dog of a gun!

Didn't mean to sound stroppy!!!

 

[foxfish]

You could consider combining your idea with the vertical band muzzle & some rollers?

 

[scallywag]

I think I'll have to make some mock-ups before I start building.

 

[-Paddy-]

I look forward to see your build scallywag. It is always interesting to see the new ideas and designs that builders come up with.

I'm thinking about building myself a light classic teak gun with 16-18mm single band and 6mm shaft, but I like roller guns so much that I migh end up with another roller.

Good luck with your project!

 

[scallywag]

Out of interest what dimensions do you use for your rollers?

 

[-Paddy-]

I was making my rollers to fit individually to every gun I made and I would recomend the same to you.
The width and the radius depend on the band diameter you are going to use. I recomend 14-16mm bands.
The distance/diameter between the radius depends from the hight of the gun in that section. Basicaly you dont want the bands to rub against your gun, so this dimension should be a bit bigger then hight of the gun section behind individual rollers.
Total diameter should be at least a few mm bigger then the diameter of the radius, so the bands stay on the rollers.
Hole diameter depends obviously from the shaft, bushes, bearings or what ever else you are going to use.
I don't know if I made myself clear enough, but it is a bit hard to explain.
Here is a picture of a roll I came up witch recently. I think that this size and proportion should fit 90% of the builds.

 

[scallywag]

Cheers Paddy, thats pretty close to what I'd drawn up.
I'll start a build thread as soon as I've got the bits together.

 

[scallywag]

Well the rollers are done,(all bar the plastic bearing liner) made from cnc machined aluminium with a colour anodize finish. All I need now is the spear and trigger mech. Thanks to Paddy for the dimensions.