Gear Rifles - design assistance requested

[Varyon]

This is an idea I had (or, rather, shamelessly stole from this thread), for a "rifle" that stored its motive power in a clockwork battery. A good option for how it turns energy stored in said battery into propelling a bullet into some monster's skull, however, has always eluded me.

Until now.

Thanks to the Forgotten Weapons interview with the cofounder of ArcLabs about their GR-1 Anvil Gauss Rifle, I realized I could use a mechanism that pulled the bullet, rather than pushing it, down the barrel. This is what I've come up with. I'll note this is meant for DF, so strict realism is not necessary, although some nods to it would be welcome.

Aesthetically, the weapon would look more-or-less like a typical TL 4-5 musket/rifle, but with an ovoid barrel rather than a circular one (or a rectangle rather than a square, or an elongated hexagon rather than a regular hexagon). Internally, there is a winged "cup" at the back of the barrel, with a hole in top (matching up with one in the barrel; the latter would have a movable cover) for putting the bullet in. Threaded through the wings is a chain on each side, which wraps around and links to itself (going through the elongated portion of the barrel). When the weapon is fired, gears spin to move this chain, in turn accelerating the cup (and bullet within). When the cup reaches the end of the barrel, it strikes a brake (probably made of soft leather, or cork wood), which has a hole in the center for the bullet to pass through - this stops the cup (which slips from the chain on impact, so that the gears can continue turning for a bit rather than coming to a jarring stop; basically, the chain fits it snugly enough that it can be accelerated fairly quickly, but not enough to hold on at the sudden stop at the end). To reload, you flip a safety switch to disengage the gears from the battery, pull the cup back into loading position (it has a tab on it that comes up through a slit in the top of the barrel, and serves as rear sights; for long barrels, it typically has a lanyard attached so you can just grab and yank that back), drop a bullet in, then attach a hand crank, wind the mechanism, detach the hand crank, and finally flip the safety switch back to shooting position while shouldering the weapon.

However, that requires a sufficiently-long reload process that it may reduce the weapons to "one shot per battle," which is very much not what I want. Absent Fast-Draw, and ignoring the time to actually wind the mechanism, I'm thinking you could flip the safety and pull the cup back into position as a single Ready; draw a bullet from your pouch as a Ready; remove the cover, drop the ball into the cup, and replace the cover as a Ready; draw the handcrank as a Ready; attached the handcrank as a Ready; detach the handcrank as a Ready; stow the handcrank as a Ready (you could skip this step if you have it on a lanyard, simply dropping it as a free action); and take a final Ready to, well, Ready the weapon and flip the safety. That's 8 seconds!

What options would I have to speed this up? Having the crank permanently attached would cut time in half, but absolutely ruins the aesthetics of the weapon, so I'd rather avoid that. Might it be feasible to have a folding crank, such that the weapon doesn't have a big bulky thing off to the side normally, but you can pop it out, crank it, and put it back in (with the crank's position serving as the saftey - pulling it out switches the battery to be connected to the winding mechanism, putting it back in switches the battery to be connected to the gears). Or should I allow the battery to store multiple shots, so that reloading during combat only consists of pulling the cup back into position and dropping a bullet in?

For cranking and damage, my inclination is to define battery capacity in terms of pounds, have a character charge it by BL lb with each Ready (either 1.5xBL or 2xBL with an All Out Ready), and have the damage be equal to thr at the ST for which the battery's capacity matches its BL. That is, a battery that can store 80 lb would take a character with ST 10 around four seconds to charge (three or two seconds if going All Out) and deal damage equal to thr at ST 20 (2d-1). Does that sound feasible? Note if you dislike setting battery capacity in terms of pounds, you could instead use Joules - for 5xBL Joules, 7xBL Joules, and 10xBL Joules, respectively (of course, damage probably is unlikely to match up at all using Doug's spreadsheet, but that's fine - this is for Dungeon Fantasy, not Tactical Shooting).

I could go on, but ultimately, these are my current questions (repeating some from above):

1. What are some good options to speed up the loading process? Does a built-in crank make sense? Should storing multiple shots worth of energy be an option, or would we be stepping on the toes of archers too much?
2. Does my BL/cranking time to damage relationship make sense, from a game balance perspective?
3. What sort of weight should these weapons have? I'm thinking of taking the simplified formulae for firearms I worked out based on Classic Vehicles and simply applying a multiplier - that is, a gear rifle would weigh something like 1.2x as much as a comparable firearm.
4. What effect should barrel length have? I'm thinking a longer barrel means the battery can discharge over a longer period of time, increasing efficiency. But by how much - and what should be the "zero point?" Perhaps a "typical" gear rifle is BL 80 and has a 1-yard-long barrel, and weaker weapons can get away with a shorter barrel and still have maximum efficiency, while stronger weapons need a longer one.
5. What about rifling? I like the idea of actual rifled weapons having their brake located partway down the barrel, with a portion of it that only the bullet travels through being rifled, imparting spin (thus, you're basically sacrificing damage to get higher accuracy). Problem is, I want bullets that are made of fired clay (including hollow ones that you can fill with stuff like alchemist's fire) in addition to the typical lead ones, but I don't think said clay would engage with the rifling the same way lead would. Do clay bullets require a smoothbore weapon - or might a wax "jacket" be an option?
6. Caliber. Should the above be for pi, pi+, pi++... or even pi-? How should things scale with other calibers of bullet? One idea might be that the reduced efficiency of having the battery discharge rapidly has to do with the speed of the gears more than the time period over which the energy is discharged, so heavier bullets can get away with shorter barrels to reach maximum efficiency. Even so, what about damage? Should I just scale this like Innate Attack does - that is, if the base is pi, then pi- would be +67% damage (around +2 per die), pi+ would be -17% damage (around -0.5 per die), and pi++ would be -37% damage (around -1.5 per die)?

Any assistance would be greatly appreciated. Hopefully this time I've avoided my chronic issue of "information overload in the first post."

[Anthony]

I suggest looking up the slingatron concept (originally proposed as a space launch, but people have built them as hobby projects).

[FenrisLoki]

So my take on this from a physicist's perspective, while not being completely realistic is it sounds very fun and cool. My answers would be:

1. I'd say you should store multiple shots per crank session (maybe 4-6) then have a lengthy winding session. Additionally, you could see a slight reduction in power per additional shot as the gears wind down.

2. I think your cranking set sounds like a good balance between realism and game balance.

3. I think you've got them a bit too light. All this mechanism is going to be far heavier than real guns. I'd say a minimum should be double a comparative TL4 gun.

4. Barrel length I feel is your trickiest and potentially least realistic point. A longer barrel is going to have far more friction with this system than a bullet so I don't think things scaling like a real gun is appropriate. At best you might break even with losses and gains. The most realistic method might be what you suggest with the length being related to the strength of the gun, but I would say if anything the stronger the gun, the shorter the range should be due to friction losses. And it might be interesting effects on usability.

5. Rifling again would be very tricky. Your ideas though are a pretty cool way of giving some rational explanation. I think the wax jacket is most realistic. The trade off of range for accuracy seems most feasible.

6. Caliber seems good the way you've described. Flechette darts might be good too as an option.

[Varyon]

Originally Posted by Anthony

I suggest looking up the slingatron concept (originally proposed as a space launch, but people have built them as hobby projects).

Fascinating, but I want rifle-shaped weapons, not large discs with spiral grooves in them, which is what it appears slingatrons generally are (Joerg Sprave's version, because of course he made one). This may well be something that is extant elsewhere, however - perhaps stationary defenses often use such a scheme, provided it's more efficient than the gear rifle (and I assume it is - otherwise you'd have people building something more like a gear rifle).

However, the description I first read about it gave me another idea for imparting spin to a projectile. I've heard before that vibrations can cause screws to, well, unscrew themselves - here's a video, ignore the (I think accidentally, but my volume is off) salacious title, they just use a vibrating toothbrush and electric shaver. I'm pretty certain that's an aspect of their threads, but would it be feasible that a vibrating gear rifle - say, because the gears aren't quite properly well-aligned - could impart spin to the projectile? I could see this being an accidental discovery in the early days of replicating the gear rifles found in the dungeon*, where it turned out that getting proper alignment to reduce vibration actually reduced accuracy. So, designers have the choice between better accuracy but lower efficiency (vibration is going to eat up some of your energy), or lower accuracy but better efficiency, getting the sort of accuracy-vs-damage trade-off I'd prefer. But I don't know if that's even remotely realistic.

*Oubliette is roughly TL 2-3 generally, but has found - and successfully replicated - TL 4+ technology in the dungeons that tend to randomly pop up all over the place.

[johndallman]

I'd suggest having a weapon that takes minutes to wind up, but powers an endless chain (like a chainsaw) that runs for 4-6 seconds.

You drop your cups onto that when you pull the trigger and they get flung downrange. You need a magazine in the weapon, to make this work. That gives you RoF 1 if your magazine is operated automatically, or RoF 1/2 if it behaves more like a bolt-action rifle.

[Varyon]

Originally Posted by FenrisLoki

1. I'd say you should store multiple shots per crank session (maybe 4-6) then have a lengthy winding session. Additionally, you could see a slight reduction in power per additional shot as the gears wind down.

For firearms, I'm fond of the idea of a 5-shot revolver at low TL's (because 5 shots is how many you get before black powder fouling comes into play; also, IIRC, in Classic Vehicles, a 5-shot revolver ends up weighing exactly twice as much as a normal breechloader). So being able to hold up to 5 shots could certainly be an option. I'm thinking soldiers typically have single-shot versions, but adventurers are going to spring for the more expensive (and heavier) version.

Damage slowly going down matches the behavior of the TL 5 air rifle in HT, IIRC. I'd have to decide if I want that for DF - I'm honestly leaning toward "no" ("It's your last shot... and it does half damage" seems like adding insult to injury).

Originally Posted by FenrisLoki

2. I think your cranking set sounds like a good balance between realism and game balance.

Thanks!

Originally Posted by FenrisLoki

3. I think you've got them a bit too light. All this mechanism is going to be far heavier than real guns. I'd say a minimum should be double a comparative TL4 gun.

Double was actually my first instinct, but I feared that would be a bit too much - in settings where both are available, I want the two to be competitive with each other.

Originally Posted by FenrisLoki

4. Barrel length I feel is your trickiest and potentially least realistic point. A longer barrel is going to have far more friction with this system than a bullet so I don't think things scaling like a real gun is appropriate. At best you might break even with losses and gains. The most realistic method might be what you suggest with the length being related to the strength of the gun, but I would say if anything the stronger the gun, the shorter the range should be due to friction losses. And it might be interesting effects on usability.

The bullet - and cup for that matter - don't have much direct interaction with the barrel, although I could see a longer chain causing more friction losses. I'm willing to step away from realism here to get the effect I want - namely, that longer barrels (resulting in worse Bulk and higher weight) result in higher damage.

Originally Posted by FenrisLoki

5. Rifling again would be very tricky. Your ideas though are a pretty cool way of giving some rational explanation. I think the wax jacket is most realistic. The trade off of range for accuracy seems most feasible.

If vibration doesn't work, I think the rifled end of the barrel may well be my best bet.

Originally Posted by FenrisLoki

6. Caliber seems good the way you've described. Flechette darts might be good too as an option.

Flechette darts are an interesting idea. They'd typically be made of iron/steel rather than lead, making them lighter (so damage somewhere between what lead and clay bullets get), but they'd be eligible to be made with hardened steel, for an armor divisor. Damage type would be impaling, but probably with the same WM as the bullet they replaced, rather than the default x2 (the difference between imp and pi here would be interaction with certain types of DR and IT:DR... assuming I opt to have something that differentiates between the two, anyway). Unlike the spherical bullets, orientation would matter a great deal for these - I'd probably give a penalty to Fast-Draw to load them quickly. They'd also risk damaging the rifling if not used with a smoothbore, but if the wax jacket works for clay bullets, it should work for flechettes as well.

Originally Posted by johndallman

I'd suggest having a weapon that takes minutes to wind up, but powers an endless chain (like a chainsaw) that runs for 4-6 seconds.

You drop your cups onto that when you pull the trigger and they get flung downrange. You need a magazine in the weapon, to make this work. That gives you RoF 1 if your magazine is operated automatically, or RoF 1/2 if it behaves more like a bolt-action rifle.

I'd rather have independent shots than something that just flings metal downrange for a bit after pulling the trigger (also, I don't think my cup idea would be compatible, here). A magazine could well be an option for the default version of the weapon, although given the way it would generally need to be set up, it would interfere with aiming (although a bottom-mounted magazine, using springs or a manually-operated lever to push bullets up into the cup like a modern firearm rather than gravity to drop them down like a repeating crossbow, might be doable; it would absolutely require a dedicated weapon, or at least modifying a normal gear rifle).

[Anthony]

You know, the way the gauss rifle works is that you've got a primary electrical energy store (high storage, but not enough power to directly propel the bullet) that charges a secondary energy store (low storage, but high burst power). The equivalent of this for clockwork would be to use clockwork to charge a device of another type, such as a bow, sling, or spring.

[Varyon]

Originally Posted by Anthony

You know, the way the gauss rifle works is that you've got a primary electrical energy store (high storage, but not enough power to directly propel the bullet) that charges a secondary energy store (low storage, but high burst power). The equivalent of this for clockwork would be to use clockwork to charge a device of another type, such as a bow, sling, or spring.

The gauss rifle mention was more about giving me the idea of having the projectile be pulled rather than pushed than about trying to mimic a gauss rifle at TL DF. That said, from a certain point of view, that's exactly what's happening here - your primary (mechanical) energy store is the character's muscles, the battery is the secondary energy store that uses its high burst power to propel the bullet. Of course, you could also think of the character's muscles as being equivalent to the power plant that charges the battery, in which case we're missing the equivalent of the capacitors. A stretchy material (as used in slingshots) could work, but I think low TL's are rather lacking in such - they rely instead on bendy materials (like wood), and I'm wanting something that looks like a rifle, rather than an autococking crossbow. Although perhaps something using torsion, with the chains replaced with thick string/thin rope, could be an option? That would essentially be something with two triggers. The first releases the primary energy store to wind up the strings and generate torsion, with the cup locked in place. Once it's done "charging," you pull the trigger to release the cup, and it rockets forward, in turn propelling the bullet. You'd probably need to use the weapon shortly after creating the torsion, so gear rifles would be a bit delayed in use at the start of combat (you can have it wind up while you're reloading it for later shots).

[Anthony]

Originally Posted by Varyon

A stretchy material (as used in slingshots) could work, but I think low TL's are rather lacking in such - they rely instead on bendy materials (like wood), and I'm wanting something that looks like a rifle, rather than an autococking crossbow. Although perhaps something using torsion, with the chains replaced with thick string/thin rope, could be an option?

What TL are you thinking about? I was assuming this was for a clockpunk TL 5-6. The essence of 'clockwork' is that you have a primary energy source (for something portable, probably a mainspring, though non-portable clocks often used a suspended weight) that gets converted to something else through a set of gears, and if you can build a mainspring you've got pretty good elastic materials. Still, your basic problem is that most methods of converting rotary motion to linear motion involve long arms (the prototypical simple example is a torsion catapult).

[Varyon]

Originally Posted by Anthony

What TL are you thinking about? I was assuming this was for a clockpunk TL 5-6. The essence of 'clockwork' is that you have a primary energy source (for something portable, probably a mainspring, though non-portable clocks often used a suspended weight) that gets converted to something else through a set of gears, and if you can build a mainspring you've got pretty good elastic materials. Still, your basic problem is that most methods of converting rotary motion to linear motion involve long arms (the prototypical simple example is a torsion catapult).

For Oubliette, the world at large is mostly TL 3-ish, with some TL 4 technology - that is, your stereotypical DF setting. The dungeons are otherworldly in origin (and are their own pocket dimensions, after a fashion), and contain some technology from other worlds. Some of this technology, such as the gear rifles, is technically TL 3^ and TL 4^ clockwork, which performs roughly comparably to TL 5 and TL 6 clockwork. The inhabitants of Oubliette can duplicate this technology (in large part because one flavor of magic in the setting allows one to unmake an item, and in the process gain the knowledge to make it again, given appropriate time and materials... and skills), but as it is TL 3-4^, it is unreliant on the sorts of materials and technology available at TL 5-6, being able to use what they already have access to (iron, steel, etc).

What sort of material/technology did you have in mind? It may be something they could get access to via the dungeons, and potentially have other uses (for example, I'm considering the advanced knowledge of clockwork and gears allowing for decently-accurate timepieces and low-tech velocipedes, despite such not showing up as loot in the dungeon). I'll note I'm not aiming for scientific rigor, rather more "that makes sense, and would be pretty neat."