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Old 09-29-2016, 04:23 PM   #11
The_Ryujin
 
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Default Re: [Low-Tech] Chinese Guns

Quote:
Originally Posted by Icelander View Post
What is the weight of projectile and velocity that you are assuming for that Dmg? And what is the caliber of the ball?
Since it's an iron ball that weights 0.52kg that gives us a roughly 25mm diameter given that iron is about 7.8g/cc.

200m/s was the velocity I used to get 3d+2. That is a bit too high for my taste but if we assume that figure in the book was correct for a normal density bullet and they forget to half it then I suppose it works, in so far as my model is right in the first place.

Hopefully we'll be able to find source that covers how fast it's muzzle velocity was to get more concrete data.
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Old 09-29-2016, 05:53 PM   #12
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Default Re: [Low-Tech] Chinese Guns

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Originally Posted by The_Ryujin View Post
Since it's an iron ball that weights 0.52kg that gives us a roughly 25mm diameter given that iron is about 7.8g/cc.

200m/s was the velocity I used to get 3d+2. That is a bit too high for my taste but if we assume that figure in the book was correct for a normal density bullet and they forget to half it then I suppose it works, in so far as my model is right in the first place.

Hopefully we'll be able to find source that covers how fast it's muzzle velocity was to get more concrete data.
The Crouching Tiger Gun is supposed to have a WPS (Weight Per Shot) of 1.15 lbs., which is the combined weight of the propellant and the stone shot. I don't know what kind of stone, though I've seen sources on Turkish guns mention marble balls. In any event, it must be a tolerably dense stone, but not so dense that it cannot be worked into a round shape without unreasonble effort.

Marble has about a third of the density of iron or 2.563g/cc, so there's a benchmark you could use. Granite at 2.75g/cc makes fairly little difference. Basalt, at 3.011g/cc would be noticably denser and mean a slightly smaller ball.

I would be hesistant to use a 25mm caliber, as it would be rather difficult to fit 100 lead shot of .43 inc to .50 inch there. In fact, it would be entirely against the rules in HT p. 172 for multiple projectiles. Even if we were to assume the smallest .43 caliber shot (which would contradict the WPS as well as Range), we still could not fit more than 12 and that only with great good will and some minor frowardness at rounding.

In any case, there is absolutely no way that the projectile could weigh 0.52 kg, as that would mean that there were less than 25 grains of black powder propelling it. A more plausible powder charge would be the 3 oz. (1312.5 grains) charge that unidentified people on the Internet attribte to the Crouching Tiger Gun by citation to a 1994 volume of Joseph Needham I can't access or the massive 8 oz. (1/2 pound = 3,500 grains) charge that Joseph Needhams assigns* it in his 1987 volume I can read.

This would leave 4,550-6,737.5 grains for the possible weight of the round stone ball or 0.65-lb to 0.96-lb in GURPS terminology, 0.295 kg to 0.435 kg in civilised units.

With marble, that gives me a caliber of some 60.5mm to 68.7mm, depending on the powder charge. The lower bound of this caliber range also fits exactly with the rules on HT p. 172 used to calculate the maximum number of multiple projectiles or the cube of (barrel diameter/shot diameter).

Granite and basalt have a similar range, going roughly 59mm to 67mm and 57.5-65mm respectively, depending on how much of the 1.15 lbs. load is stone and how much is powder.

Personally, I should be inclined to estimate that a lower powder charge would be used with stone shot than lead and thefore essay the 3 oz. charge with the stones and save the 8 oz. one for the lead shot. Depending on the type of stone, I should then have a projectile which took the form of a 0.435 kg stone with a diameter of some 65mm to 68.5mm. If we want to go with the same 8 oz. powder charge for both stones and lead shot, we'd get a 0.297 kg stone ball with a diameter around 57mm to 60.5mm.

If we want 6d+2 pi++ with either load, we have to accelerate it to between 730 fps and 870 fps, depending on our assumptions for stone type and amount of propellant. This is not impossible, to be sure. With a heavy load and good powder, black powder weapons achieved this and much faster velocities too. And even the 'light' load of 3 oz. of black powder is more than three times the heavy load of a 4-bore elephant rifle.*

The mystery then becomes why the Long-Range-Awe-Inspiring Gun, with a 2-lb to 2.5-lb lead ball of diameter from 54mm to 58mm, cannot get more than a 2.2% improvement over this damage. This will occur if we can keep the velocity under 500 fps, I believe, but as to why 8 oz. of black powder should not answer for more velocity gain than that in a 3' barrel compared to a 2' one (especially if we are assuming a 3 oz. charge in the smaller gun), I must admit perplexity.

Also, if the Crouching Tiger Gun can handle that weight of shot and blazing velocity, why build a gun with an identical role and little to no improvement that's 33% longer, more than 240% heavier and almost 240% more expensive?

*With no doubt correct translation, but yet I shudder to think of a 47 lbs. gun firing almost three pound of lead shot with a half pound powder charge and question why where would be any need for the more strongly built Long-Range-Awe-Inspiring Gun if this heavy charge were not considered somewhat over-reaching for the smaller gun.
**Albeit early TL4 powder vs. mature TL5, so that the relative TNT equivalnt measured after correcting for REF might merely be as little as 2 to 1 in favour of the bombard.
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Last edited by Icelander; 09-29-2016 at 06:26 PM.
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Old 09-29-2016, 06:38 PM   #13
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Default Re: [Low-Tech] Chinese Guns

Ah, I mistook the listed weight as just being the shot and I must of miss read the stat line since I thought it was an iron ball that it shot. When I get home from work later tonight I'll go over it again and look over the gun section of low tech more carefully, my calculation was based on a really quick glance over I did while getting ready for work.
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Old 09-29-2016, 11:30 PM   #14
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Default Re: [Low-Tech] Chinese Guns

Ok, now that I've a chance to look over things I've noticed I made a mistake with my diameter assumption, I accidentally used the radius in my calculation rather then the diameter. That's what I get for trying to rush something out before I got the time to sit down and think >.>

I ran the numbers for the Long Range Cannon based on the lead shot weighing 1.19kg and was fired at your estimate of 152m/s with a diameter of 58.4mm and a density of 11.34g/cc. This gives me 17.4 dice with my formula. I ran it again with Doug's and got 15.5. If I ignore density for my formula I get 15.4 dice.

In order to get the books number of 7d-1 or 6.85 dice the gun could only fire at 71m/s!

Given that the numbers I'm getting is roughly twice as high, I wonder if Bill accidentally halved the Long Range Cannon and left the Crouching Tiger one at full damage.
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Old 09-30-2016, 12:16 AM   #15
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Default Re: [Low-Tech] Chinese Guns

Quote:
Originally Posted by The_Ryujin View Post
...

In order to get the books number of 7d-1 or 6.85 dice the gun could only fire at 71m/s!

Given that the numbers I'm getting is roughly twice as high, I wonder if Bill accidentally halved the Long Range Cannon and left the Crouching Tiger one at full damage.
OK just going by comparisons to other guns* in the book (so not commenting on the maths).

That would make the 160lb awe inspiring gun 14d, considerably more efficient by weight than any other gun in the book. In terms of damage the nearest comparisons being the 15d Saker that weighs 1400lbs, the 14d+1 3lb cannon weighs 1000lbs

Now don't get me wrong these guns are not identical, but that's a massive improvement (which I don't think can just be covered by the fact the saker and 3lb cannon have wheels) with really a reduction in range to compensate?


If anything isn't it more likely that the crouching gun's stone shot damage didn't get halved?

As again if you look at it nearest direct comparison the swivel gun (which doesn't have a wheeled carriage) its doing the same damage with stone shot as the swivel gun does with metal and weighs a quarter of the swivel gun weight!

And if you compare it to the wall gun which is a bit lighter but does 5d+1, having the 6d+2 figure being for lead makes sense as well

Or maybe the Chinese once they got into TL4 just made absolutely amazing cannon compared to everyone else (but I don't think that's backed by history)


*which of course begs the obvious question were the discrepancy is.

Last edited by Tomsdad; 09-30-2016 at 06:53 AM.
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Old 09-30-2016, 01:34 AM   #16
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Default Re: [Low-Tech] Chinese Guns

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Originally Posted by The_Ryujin View Post
I ran the numbers for the Long Range Cannon based on the lead shot weighing 1.19kg and was fired at your estimate of 152m/s with a diameter of 58.4mm and a density of 11.34g/cc. This gives me 17.4 dice with my formula. I ran it again with Doug's and got 15.5. If I ignore density for my formula I get 15.4 dice.
That's quite a lot, considering that my estimate of 500 fps was derived from at what velocity Doug Cole's Ballistics sheet gave a projectile of that size Dmg 7d-1.

Granted, 1.19 kg for the lead ball is slightly heavier than I had modelled, as I tried lead ball from 2-lb to 2.5 lbs. (0.9 1kg to 1.13 kg). Remember, the WPS of 3 lbs. includes the propellant and that propellant is at minimum 8 oz. or 0.23 kg, according to sources on the Long-Range-Awe-Inspiring Gun.

But this is not enough of a discrepancy to explain such a wide range in the calculated damage. I'm using a version of Doug's file from February 24th, 2011.

This is how my assumptions look:

Code:
Chamber Pressure --	1090 	psi
Barrel bore -------- 	59	mm
Case Length --------	30	mm
Chamber Bore ------	60	mm
Barrel length -------	610	mm
Bullet Mass ---------	17500	grains
Aspect Ratio --------	1	L/Bore
Burn length --------	300	mm
Projectile Caliber ---	58	mm
Total Accelerated Mass	17500	grains

Velocity ---	137,1	m/sec
 -----------	450	feet/sec
Kinetic Energy	10657,7	Joules

Note that Chamber Pressure and Burn Length are not necessarily historically right, but it doesn't matter, as they are only set up to produce the right velocity. One might be higher and the other lower, as long as velocity comes out the same.

With this size ball, I get Dmg 7d-1 at velocity 450 fps. If I go down to a smaller ball of 2-lb, I need velocity 500 fps for the same damage.

Quote:
Originally Posted by The_Ryujin View Post
In order to get the books number of 7d-1 or 6.85 dice the gun could only fire at 71m/s!
That seems too high a damage for such low velocity.

Quote:
Originally Posted by The_Ryujin View Post
Given that the numbers I'm getting is roughly twice as high, I wonder if Bill accidentally halved the Long Range Cannon and left the Crouching Tiger one at full damage.
I'd think that the Crouching Tiger Gun is more likely to be wrong, as the Long-Range-Awe-Inspiring Gun actually has plausible enough stats at 450 fps, very similar to a Swivel-Gun.
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Old 09-30-2016, 01:38 AM   #17
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Default Re: [Low-Tech] Chinese Guns

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OK just going by comparison other guns* in the book (so not commenting on the maths).

That would make the 160lb awe inspiring gun 14d, considerably more efficient by weight than any other gun in the book. in terms of damage the nearest comparisons being the 15d Saker that weighs 1400lbs, the 14d+1 3lb cannon weighs 1000lbs

Now don't get me wrong these guns are not identical, but that's a massive improvement (which I don't think can just be covered by the fact the saker and 3lb cannon have wheels) with really a reduction in range to compensate?

If anything isn't it more likely that the crouching gun's stone shot damage didn't get halved?
Oh yeah, this all just blind guess atm. I was originally thinking that Awe Inspiring was accidentally halved and the Crouching Tiger wasn't but it is also possible that the Awe Inspiring is right and the Crouching Tiger is still a typo.

Quote:
Originally Posted by Tomsdad View Post
*which of course begs the obvious question were the discrepancy is.
And that is what's driving me nuts heh.
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Old 09-30-2016, 02:01 AM   #18
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Default Re: [Low-Tech] Chinese Guns

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Originally Posted by Icelander View Post
That's quite a lot, considering that my estimate of 500 fps was derived from at what velocity Doug Cole's Ballistics sheet gave a projectile of that size Dmg 7d-1.

Granted, 1.19 kg for the lead ball is slightly heavier than I had modelled, as I tried lead ball from 2-lb to 2.5 lbs. (0.9 1kg to 1.13 kg). Remember, the WPS of 3 lbs. includes the propellant and that propellant is at minimum 8 oz. or 0.23 kg, according to sources on the Long-Range-Awe-Inspiring Gun.

But this is not enough of a discrepancy to explain such a wide range in the calculated damage. I'm using a version of Doug's file from February 24th, 2011.



This is how my assumptions look:

Code:
Chamber Pressure --	1090 	psi
Barrel bore -------- 	59	mm
Case Length --------	30	mm
Chamber Bore ------	60	mm
Barrel length -------	610	mm
Bullet Mass ---------	17500	grains
Aspect Ratio --------	1	L/Bore
Burn length --------	300	mm
Projectile Caliber ---	58	mm
Total Accelerated Mass	17500	grains

Velocity ---	137,1	m/sec
 -----------	450	feet/sec
Kinetic Energy	10657,7	Joules

Note that Chamber Pressure and Burn Length are not necessarily historically right, but it doesn't matter, as they are only set up to produce the right velocity. One might be higher and the other lower, as long as velocity comes out the same.

With this size ball, I get Dmg 7d-1 at velocity 450 fps. If I go down to a smaller ball of 2-lb, I need velocity 500 fps for the same damage.


That seems too high a damage for such low velocity.


I'd think that the Crouching Tiger Gun is more likely to be wrong, as the Long-Range-Awe-Inspiring Gun actually has plausible enough stats at 450 fps, very similar to a Swivel-Gun.
I don't know if open office is just acting buggy or if I made a mistake somewhere but I created a new spread sheet just to be sure and ran the numbers using Doug's formula again and I got 6.7 dice. I'm still getting double the damage with my number so I think it's clear that my formula must be off. Welp, back to the drawing board I go.

But at lest I think it's pretty safe to say that that Crouching Tiger Gun stats are in error.
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Old 09-30-2016, 06:59 AM   #19
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Default Re: [Low-Tech] Chinese Guns

Quote:
Originally Posted by The_Ryujin View Post
Oh yeah, this all just blind guess atm. I was originally thinking that Awe Inspiring was accidentally halved and the Crouching Tiger wasn't but it is also possible that the Awe Inspiring is right and the Crouching Tiger is still a typo.



And that is what's driving me nuts heh.
Yeah, a lot of comparing variables against variables here!
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Old 09-30-2016, 01:10 PM   #20
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Yeah, a lot of comparing variables against variables here!
Yeah, but at lest we made some progress though it sucks that I didn't end up helping as much as I thought I was. Thought my model was getting really close but it seems that I made an error somewhere on my test sheet. Thank god I didn't use it for my GURPSday post!

This is one of the reason I don't like the "closed box" mind set that 4th editions has had. It's hard to have a generic system if I don't know how to play with it's numbers (though don't get me wrong, I do understand why they felt pressured to do so. I just don't like it heh).

But now that we're pretty sure that we've figured out what's going on with the Crouching Tiger Gun, it's time to move on to why the scattershot range is different from what High Tech suggests.
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