Gear Rifles - design assistance requested

[Anthony]

Originally Posted by Varyon

at sort of material/technology did you have in mind?

Good enough materials and manufacturing tolerances to build high strength low friction clockwork. Having orichalcum would probably help.

[thrash]

What about a series of spinning disks, probably in pairs, that propel a shot by friction? Each pair spins faster than the one before, to provide the acceleration along the length of the barrel? Somewhat like an automatic pitching machine in a batting cage, but in stages.

Each pair of disks has it's own clock spring. As the round moves down the barrel, it triggers each pair in turn. (This probably works better for a flechette or needle than a spherical shot.) The clock springs are all geared together, however, so that they can be wound from a master crank that is folded into the stock.

The basic mechanism isn't substantially more complicated than a wheel lock. The timing and master crank push this into the realm of unobtainium.

[Varyon]

Originally Posted by Anthony

Good enough materials and manufacturing tolerances to build high strength low friction clockwork. Having orichalcum would probably help.

Well, at least the base models are unreliant on fantastical materials, just cinematic engineering. But are you saying something akin to my current setup, but with an intermediate clockwork storage system between the primary energy storage and the gears that actually move the chain?

Originally Posted by thrash

What about a series of spinning disks, probably in pairs, that propel a shot by friction? Each pair spins faster than the one before, to provide the acceleration along the length of the barrel? Somewhat like an automatic pitching machine in a batting cage, but in stages.

Each pair of disks has it's own clock spring. As the round moves down the barrel, it triggers each pair in turn. (This probably works better for a flechette or needle than a spherical shot.) The clock springs are all geared together, however, so that they can be wound from a master crank that is folded into the stock.

The basic mechanism isn't substantially more complicated than a wheel lock. The timing and master crank push this into the realm of unobtainium.

Prior to seeing the video about the gauss rifle, this was more-or-less the working concept. However, the timing issue - as well as feeling hollow clay bullets may not be resilient enough to be battered about like this - made me dislike it. I also wasn't crazy about how heavy it would require the barrel to be - my preference is that roughly half the weight is in the stock (most of said weight being the energy storage mechanism), and half the weight being in the barrel, such that its balance point is around where the trigger is. I felt this would give it good balance for handling, as well as making it feasible to be used with Staff (it has comparable balance to a sword, where the balance point tends to be very near the crossguard, and I feel a sword should be usable with Staff, with one hand on the hilt and one on the blade).

[whswhs]

Have you looked at GURPS Low-Tech itself? Page 79 has all sorts of devices for readying a crossbow or catapult to fire at a higher ST that the user's unaided level. See in particular the windlass and cranequin.

[Anthony]

Actually, you can do the mechanical equivalent of a coilgun, though engineering it at TL 4, or even TL 6, is pretty optimistic.

The basic idea is that you have a pair of rails, with gears between the rails (probably more of a one-way gear, as it meshes more easily that way). The projectile is designed to slide along the rails, and has the ability to catch on the gears.

Now for the tricky engineering: each gear spins faster than the previous one, and thus as the projectile proceeds from one gear to the next, it is accelerated. Get the timing right, and you've got a mechanical linear accelerator.

[martinl]

Originally Posted by Anthony

The basic idea is that you have a pair of rails, with gears between the rails (probably more of a one-way gear, as it meshes more easily that way). The projectile is designed to slide along the rails, and has the ability to catch on the gears.

Now for the tricky engineering: each gear spins faster than the previous one, and thus as the projectile proceeds from one gear to the next, it is accelerated. Get the timing right, and you've got a mechanical linear accelerator.

Carefully chained nautilus gears might do the trick here, especially if you don't worry too much about strength of materials.

[Varyon]

Originally Posted by whswhs

Have you looked at GURPS Low-Tech itself? Page 79 has all sorts of devices for readying a crossbow or catapult to fire at a higher ST that the user's unaided level. See in particular the windlass and cranequin.

While I wasn't looking directly at them, I'll note that the windlass involves the same time multipliers as what falls out of my system, undoubtedly due to both being based on the same concept - that is, x1.5 to ST (and thus x2.25 to BL) is x2.25 to draw time, x2 to ST (x4 BL) is x4 to draw time, etc. So, I think my time ideas are on the right track. Arguably, it should use the doubled times of the cranequin, as it's only a single crank rather than the two of a windlass, but I'm willing to let that pass.

... of course, while looking up videos of windlasses to confirm that they have two cranks, I came across this gem. Yeah that's... that's a gear rifle. Shooting bolts, but a gear rifle (maybe the makers read the same thread I got the idea from? It was a gear bow there...). It's designed quite a bit differently from mine, however - but I think for DF, I kinda like my design better. But I'm biased.

Originally Posted by Anthony

Actually, you can do the mechanical equivalent of a coilgun, though engineering it at TL 4, or even TL 6, is pretty optimistic.

The basic idea is that you have a pair of rails, with gears between the rails (probably more of a one-way gear, as it meshes more easily that way). The projectile is designed to slide along the rails, and has the ability to catch on the gears.

Now for the tricky engineering: each gear spins faster than the previous one, and thus as the projectile proceeds from one gear to the next, it is accelerated. Get the timing right, and you've got a mechanical linear accelerator.

Again, the idea isn't to have a mechanical coilgun, just a gun that uses mechanical energy instead of chemical. One of my other ideas was to have a piston (possibly telescoping, so it didn't stick out the back when not in use) that would engage gears much as you're envisioning the projectile doing, with the piston pushing the projectile forward. That would probably work a little better using the idea of a cup (basically, a small piston that gets carried forward by the sequence of gears), but I don't like the extreme precision that would be necessary to get the teeth of the gears and the slots on the piston/cup to line up as well as they'd need to, in addition to needing gears spinning at different speeds (for an accelerating effect), and the weight of having gears going all the way down the barrel (plus having each gear linked to the battery in the stock). What I like about the "chaingun" idea is that it's relatively simple - just gears in the stock spinning to spin a linked chain.

[Anthony]

Originally Posted by Varyon

What I like about the "chaingun" idea is that it's relatively simple - just gears in the stock spinning to spin a linked chain.

The problem with the chain idea is that you have to move the entire chain to move the projectile, which means you have a large efficiency loss unless either the chain is very light, or you can keep the chain spinning between projectiles.

[thrash]

Originally Posted by Varyon

Again, the idea isn't to have a mechanical coilgun, just a gun that uses mechanical energy instead of chemical. One of my other ideas was to have a piston... that would engage gears much as you're envisioning the projectile doing, with the piston pushing the projectile forward.

Sounds as if you could be describing a scaled-up Red Ryder BB gun (HT, pp. 88-89). Skip the gears; use air as a working fluid. Put the piston under the barrel and back it with a strong coiled spring. Since you don't have to emulate a lever-action, you can increase the strength of the spring -- say, brace the butt on the ground and use two hands to cock it.

Not as delightfully clock-punk as a gear rifle, but certainly plausible. Real-world metallurgy and gun-smithing weren't up to the strengths and tolerances required, but you don't seem concerned about that.

[Fred Brackin]

Originally Posted by Anthony

Good enough materials and manufacturing tolerances to build high strength low friction clockwork. Having orichalcum would probably help.

We already have an Orichalcum Spring Gun in DF6. It's basically a ST12 Crossbow with 8 shots but without those inconvenient arms.