vL to dTons (and back again)

[Taluron]

Okay, I'm making a small craft which carries a few vehicle weapons (combat drop ship, vehicle weapons are for ground support during unloading).

In the T20 handbook it says that the ratio is that a dTon is appro 1400 vL, ie divide vL by 1400 to get dTon. But in Traveller Aide #3 and #6 it says this:
"multiplying the vls by 5 to get the size in liters, then divide by 1000 to get cubic meters, and again by 14 to get starship tons"

This says (effectively) to divide vL by 2800 to get dTons. (x5 /1000 /14 resolves to /2800)

So which is it? divide by 1400 or divide by 2800?

 

[tjoneslo]

Either, pick one and be consistent.

The issue is that VLs are both volume and mass, in the same way that starship tons are both volume and mass. And neither are consistent about conversions to real units.

I wrote TA3,6,8 where the alternate conversion appears. I felt the conversion gave better (read: closer to real life) values for vehicles. That is a 4,000 vl car is closer to 20 cubic meters than to 40 cubic meters.

This really should be in a FAQ somewhere. See also:
<a href="http://www.travellerrpg.com/cgi-bin/Trav/CotI/Discuss/ultimatebb.cgi?ubb=get_topic;f=3;t=000668" target="_blank">
VL to KG conversion the t20 vehicle design sequence</a>
<a href="http://www.travellerrpg.com/cgi-bin/Trav/CotI/Discuss/ultimatebb.cgi?ubb=get_topic;f=40;t=000390" target="_blank">
How big is 1vls?</a>

 

[veltyen]

To reconcile these two opposing statements I've taken to a slightly different interpretation.

VL=5 litres interior to the vehicle
VL=10 litres to store the vehicle within something else. (ie. on a spaceship)

 

[BetterThanLife]

OK. So an M-1 Tank is between 90 and 95 cubic meters (Approximately) and weighs between 60 and 80 tons (Approximately, and depending on which version of the Tank you are talking about. Lets use the low end of the scale and call it 60 Metric Tons.). 1 Cubic meter is 1000 liters.
An M-1 Tank is about 10M long about 3.7M wide and about 2.5M high. Approximately 92.5 cubic meters (We'll round down to 90 Cubic meters. Mostly because it makes the math easier and takes into account the Turret is smaller than the body.)

Now sitting on the deck of a starship, it is 6 2/3 boxes long, and 2.5 boxes wide. (Taking up about 8 2/3 tons of floor space in a starship, however there is about .5m of clearance above the tank so you can stack stuff on top of it, which then gives up a DTon value of 6.9 for the tank. (Roughly because of rounding and the fact that a DTon on a starship deckplan is only 13.5 cubic meters.)

Now according to CT, MT, T20 1 Dton is approximately 14 cubic meters. So an M-1 Tank is about 6.4DTons. Density wise it masses about 10 tons per DTon (ton of displacement).

According to T20 an M-1 tank would be about 9000 vls. This in terms of DTons is about 6.4DTons.

According to TA-3,6,8 an M-1 Tank has a vls of 18,000 (based on liters of the tank or based on the DTons of the tank.) or 60,000 (based on mass of the tank). I personally think that is highly confusing and think the T20 calculation makes more sense. (At least it is consistent.)

Further according to the calculations in T20 a low berth is either 500 vls, in the vehicle design rules, or 700 vls (.5 DTons), in the Starship design rules. They aren't the same but fairly close. (One could guess that it is rounded to make starship calculations easier.) Now according to the TA3,6,8 rules that same low berth is only .1785 DTons. To use your formula and be fairly consistent with the vehicle design/starship design rules all the components have to be resized.

I think the alternate rules in TA3,6,8 need to be clearly marked as an alternative system (As they obviously don't mesh with the rest of the T20 rules in terms of calculation of VLS.) the same way the half jump fuel rule is listed.

To answer the question originally asked, which to use. The Canon choice is 1 DTon = 1400 Vls.

Sorry TJoneslo. I do love your work, your vehicle designs are wonderful, but that formula, making all your designs half the size for cargo purposes, just doesn't feel right at all.

Originally posted by tjoneslo:
Either, pick one and be consistent.

The issue is that VLs are both volume and mass, in the same way that starship tons are both volume and mass. And neither are consistent about conversions to real units.

I wrote TA3,6,8 where the alternate conversion appears. I felt the conversion gave better (read: closer to real life) values for vehicles. That is a 4,000 vl car is closer to 20 cubic meters than to 40 cubic meters.

This really should be in a FAQ somewhere. See also:
<a href="http://www.travellerrpg.com/cgi-bin/Trav/CotI/Discuss/ultimatebb.cgi?ubb=get_topic;f=3;t=000668" target="_blank">
VL to KG conversion the t20 vehicle design sequence</a>
<a href="http://www.travellerrpg.com/cgi-bin/Trav/CotI/Discuss/ultimatebb.cgi?ubb=get_topic;f=40;t=000390" target="_blank">
How big is 1vls?</a>

 

[tjoneslo]

As previously discussed, the use of one term (vl) to describe both weight (mass) and volume leads to many confusing conversions, depending upon where you start and what you consider "realistic"

As a counter point to using an M1 tank, try doing the conversion using any boat. In order to float, the boat must have a volume (in liters) greater than it's weight (in kg). Or a Density < 1 kg/liter. Submarines must be of neutral density or almost exactly 1 kg/liter. Most unarmored vehicle are between 1 and 2 kg/liter. As you point out, armormed vehicles like the M1 can get up to 4 kg/liter.

So there really isn't a perfect or even good conversion. Like I said, pick one and be consistent.

 

[RandyT0001]

Originally posted by tjoneslo:
Either, pick one and be consistent.

The issue is that VLs are both volume and mass, in the same way that starship tons are both volume and mass. And neither are consistent about conversions to real units.

Nope, vl is for volume, kg is for mass. Traveller dtons is volume not mass. In CT, which T20 is based on, the mass of an object was irrelevent since the gravitic drives of starships and vehicles were not affected by the mass thereon or therein.

I wrote TA3,6,8 where the alternate conversion appears. I felt the conversion gave better (read: closer to real life) values for vehicles. That is a 4,000 vl car is closer to 20 cubic meters than to 40 cubic meters.

So basically you decided to change the accepted T20 conversions of 1400vl equates to one dton. I can't understand why QLI accepted it though with such a radical change included. T20 isn't that old and we already have conflicts in T20 'canon' about designing vehicles. I was hoping that QLI would have learned from Traveller's mistakes in the past and not incorporate new inconsistencies in the rules.

This really should be in a FAQ somewhere. See also:
<a href="http://www.travellerrpg.com/cgi-bin/Trav/CotI/Discuss/ultimatebb.cgi?ubb=get_topic;f=3;t=000668" target="_blank">
VL to KG conversion the t20 vehicle design sequence</a>
<a href="http://www.travellerrpg.com/cgi-bin/Trav/CotI/Discuss/ultimatebb.cgi?ubb=get_topic;f=40;t=000390" target="_blank">
How big is 1vls?</a>

My suggestion to the original post is to use 1400 vl equals one dton as stated in T20.

 

[BetterThanLife]

OK. Lets pick yours and stay consistent with it for a second.

A Low Berth, (should be a low berth no matter what is transporting it as it is still going to need all the same components.) is 500vl.

A Low Berth using the T20 calculations is .357 DTons.

A Low Berth using the TA 3,5,8 calculations is .179 DTons.

A Low Berth under the Starship components is .5 DTons.

I am willing to concede that the starship number was rounded to make calculations easier. Or even that the Starship one, because of regulations needs an extra piece of safety equipment. But to be able to easily fit 2 in the same space of one low berth? That makes no sense to me.

Originally posted by tjoneslo:
As previously discussed, the use of one term (vl) to describe both weight (mass) and volume leads to many confusing conversions, depending upon where you start and what you consider "realistic"

As a counter point to using an M1 tank, try doing the conversion using any boat. In order to float, the boat must have a volume (in liters) greater than it's weight (in kg). Or a Density < 1 kg/liter. Submarines must be of neutral density or almost exactly 1 kg/liter. Most unarmored vehicle are between 1 and 2 kg/liter. As you point out, armormed vehicles like the M1 can get up to 4 kg/liter.

So there really isn't a perfect or even good conversion. Like I said, pick one and be consistent.

 

[Tekrat04]

Originally posted by tjoneslo:
As previously discussed, the use of one term (vl) to describe both weight (mass) and volume leads to many confusing conversions, depending upon where you start and what you consider "realistic"

As a counter point to using an M1 tank, try doing the conversion using any boat. In order to float, the boat must have a volume (in liters) greater than it's weight (in kg). Or a Density < 1 kg/liter. Submarines must be of neutral density or almost exactly 1 kg/liter. Most unarmored vehicle are between 1 and 2 kg/liter. As you point out, armormed vehicles like the M1 can get up to 4 kg/liter.

So there really isn't a perfect or even good conversion. Like I said, pick one and be consistent.

Mayb I ask where did you get the notion that (vl) represent both volume and mass?

Page 223 of THB states quite clearly that this is not the cass:

Volume is given in vl, which represents about 10 liters of volume or 0.01 cubic meters of space.
Weight is in grams (g) or Kilograms (Kg).

Again form page 223 on the subject of displacement:

Displacement tons do not indicate weight or mass.

On the subject of mass per liters you may want to double check your math. How did you come up with 4kg/l for a M1? Ussing Bhoins numbers a M1 should actually float!!! (80,000kg/90,000l = 0.889kg/l). The problem here was not that Bhoins had the wrong numbers for a M1. It's that he did not use the right mesurments to calculate the volume of the hull and turret of a M1.

M1A2 Statistics
Lenght, gun forward: 9.83m
Lenght, hull: 7.92m
Width: 3.66m
Height, overall: 2.89m
Height, to turret roof: 2.48m
Ground clearence: 0.48m
Mass, full combat load: 69,500kg

If we use the max dimmention figures (9.83*3.66*2.89) to calculate the volume we get a volume of 103.976 cubic meters. Over 50% of this would be air. In order to get a closer aproximation of the volume of a M1A2 we need to concentrate only on the hull it self. So we use the lenght of the hull (7.92m), the width (3.66m) and the height of the hull it self, the height to the turret roof minus the ground clearence (2.48m - 0.48m = 1.9m). This gives us a volume of 55 cubic meters. About 20-25% of this is still air. We will use the smaller of this value, so we multiply 55 by 0.8 for a sub total of 44 cubic meters. Now we add the volume of the components that are outside of the hull, 1.6 m3 per track, 0.4m3 for the gun barrel and another 1m3 for the miscellaneous components on top of the turret. So in the end a M1A2 would have a volume of 48.6m3 and a density of 1.43kg/l.

People need to take the time to find the right figures and do the math correctly.

 

[mike wightman]

The vl system for vehicle design is a nice, simple way to design vehicles.

I have issues with it, mainly the idea that a human takes up 1300litres, and the conversion of vEP to EP

I agree that the T20 core book does not equate vl to a combined mass/volume fudge, and thus, when the Yiarn Caardee Vehicle Catalog is published we will have the first T20 rules schism

 

[BetterThanLife]

I do appologize for not having exactly the correct dimensons of the M-1 Tank. I got the ones I had off an Army Web site which was not the TM for the tank.

I knew the weight was in excess of 60 Tons but wasn't sure how much more the A2 was above 60 tons. I do remember many bridges having to be reconstructed and checked for weight tolerance in Germany because of the M-1 Deployment. I do appologize for my approximation but it does prove the point that volume and mass have no correlation.

Originally posted by Tekrat04:
</font><blockquote>quote:</font><hr />Originally posted by tjoneslo:
As previously discussed, the use of one term (vl) to describe both weight (mass) and volume leads to many confusing conversions, depending upon where you start and what you consider "realistic"

As a counter point to using an M1 tank, try doing the conversion using any boat. In order to float, the boat must have a volume (in liters) greater than it's weight (in kg). Or a Density < 1 kg/liter. Submarines must be of neutral density or almost exactly 1 kg/liter. Most unarmored vehicle are between 1 and 2 kg/liter. As you point out, armormed vehicles like the M1 can get up to 4 kg/liter.

So there really isn't a perfect or even good conversion. Like I said, pick one and be consistent.

Mayb I ask where did you get the notion that (vl) represent both volume and mass?

Page 223 of THB states quite clearly that this is not the cass:

Volume is given in vl, which represents about 10 liters of volume or 0.01 cubic meters of space.
Weight is in grams (g) or Kilograms (Kg).

Again form page 223 on the subject of displacement:

Displacement tons do not indicate weight or mass.

On the subject of mass per liters you may want to double check your math. How did you come up with 4kg/l for a M1? Ussing Bhoins numbers a M1 should actually float!!! (80,000kg/90,000l = 0.889kg/l). The problem here was not that Bhoins had the wrong numbers for a M1. It's that he did not use the right mesurments to calculate the volume of the hull and turret of a M1.

M1A2 Statistics
Lenght, gun forward: 9.83m
Lenght, hull: 7.92m
Width: 3.66m
Height, overall: 2.89m
Height, to turret roof: 2.48m
Ground clearence: 0.48m
Mass, full combat load: 69,500kg

If we use the max dimmention figures (9.83*3.66*2.89) to calculate the volume we get a volume of 103.976 cubic meters. Over 50% of this would be air. In order to get a closer aproximation of the volume of a M1A2 we need to concentrate only on the hull it self. So we use the lenght of the hull (7.92m), the width (3.66m) and the height of the hull it self, the height to the turret roof minus the ground clearence (2.48m - 0.48m = 1.9m). This gives us a volume of 55 cubic meters. About 20-25% of this is still air. We will use the smaller of this value, so we multiply 55 by 0.8 for a sub total of 44 cubic meters. Now we add the volume of the components that are outside of the hull, 1.6 m3 per track, 0.4m3 for the gun barrel and another 1m3 for the miscellaneous components on top of the turret. So in the end a M1A2 would have a volume of 48.6m3 and a density of 1.43kg/l.

People need to take the time to find the right figures and do the math correctly. </font>[/QUOTE]

 

[BetterThanLife]

The big question on the Vehicle Guide is are the weapons, and other vehicle accessories in it sized appropiately for T20 vls? Or are they double sized?

Originally posted by Sigg Oddra:
The vl system for vehicle design is a nice, simple way to design vehicles.

I have issues with it, mainly the idea that a human takes up 1300litres, and the conversion of vEP to EP

I agree that the T20 core book does not equate vl to a combined mass/volume fudge, and thus, when the Yiarn Caardee Vehicle Catalog is published we will have the first T20 rules schism

 

[far-trader]

slyen2 asked a related question (here) and my answer might add some insight here so (cut and paste)...

I looked at this a while back and went with a straight kg = vl based on noting that the LMG in both sections (pg. 200 and pg. 247) are identical for TL, cost, damage, rof, and range. The only difference is one is 5.5kg and the other is 5.5vl.

Of course despite this and a couple other revelations* in digging around the book I'm not convinced this is correct but it works well enough.

* for example:

1 - The lowberth in the vehicle and ship sections cost the same and presumably function the same the difference is the first is rated as 500vl and the other is 0.5 Tons. This would lead me to think that 1000vl = 1 Ton. The official conversion though is 1400vl = 1 Ton.

2 - Compare the vehicle Heavy Beam Laser and Heavy Pulse Laser to the ship Beam Laser and Pulse Laser. The TL, costs and damage (adjusted for size) are the same. The difference is the vehicle ones are 1000vl (each) while the ship ones fit in 1 Ton (up to three in a turret). See the similarity?

I get the feeling some of the components were copied into the vehicle section using a straight 1000vl = 1000kg = 1 Ton. How simple and easy it would all be if that was the real way to do it. And how consistant. I'm tempted to just believe that is the case and ignore anyone (even Hunter) who says otherwise

But then there'd be so much I'd have to check and correct

 

[far-trader]

I am just an evil cross posting fool today. Again from slyen2's thread, because it might fit here too...

Originally posted by far-trader:
A little off slyen2's original topic (my reply that is) but... </font><blockquote>quote:</font><hr />Originally posted by Casey:
</font><blockquote>quote:</font><hr />Originally posted by far-trader:
1 - The lowberth in the vehicle and ship sections cost the same and presumably function the same the difference is the first is rated as 500vl and the other is 0.5 Tons. This would lead me to think that 1000vl = 1 Ton. The official conversion though is 1400vl = 1 Ton.

...For the lowberth differences it's possible [handwaving] those are two different versions or a ship needs some extra room/precautions [/handwaving].

Casey </font>[/QUOTE]Quite

Especially the way I like my lowberths, as a self contained mobile grav supported unit with independant powersupply. So add those support features to the vehicle lowberth (or rather build a small vehicle of 700vl with those features and the 500vl lowberth) and you have your, er, my tu version. It's much like the old magazine article described them for MT.

In mtu you can haul lowberths and emergency lowberths (old article mentioned they were just oversized for cattle) in the cargo hold, just not for passengers (not legally ). For (paying) passengers you need a dedicated room big enough for your rated capacity.

When the ship is built you "buy" your rated capacity of lowberths. Then each time you get a low passage it may be fresh (a live person approaches you and you install them in the lowberth) or frozen (you accept a lowberth with an occupant and swap it out for one of your empties). And at the other end your popsicle may be defrosted by you if they have arrived at their destination or kept frozen if they are going further. They may travel on with another ship if you are not still going thier way in which case the port will transfer an empty lowberth from the warehouse to fill your slot, your choice of charged up(1) for Cr100, or dead(2) for free.

(1) so you can use it anytime it has the charge pack of meds and cryos good for one cycle, minimal power sustains it indefinitly

(2) so you need to load a charge pack before you can use it

I should also note that half of that volume (vl or tons) is the actual lowberth while the other half is empty space for access and such, so that kinda fits the vehicle vl conversion used in the TA's </font>[/QUOTE]

 

[veltyen]

The vehicle scale laser weapons seem to be a sticking point. The conversion does look a little off.

Going with a ship weapon beam laser, the size is mentioned in 3 locations, under starship construction, under trade in the ship weapons entry, and presumably in the vehicle weapons section (the heavy beam laser).

Cost is the same in each case. That being 1MCr.
Damage is effectively the same (d8 ship scale/6d8 vehicle scale)
Size is highly variable. 1000VL, 0.25 dTon, or up to 3 in a single dTon with additional turret mechanisms.
Energy is also out of whack. 1 ship EP per ship laser, vs 2 Vehicle EP per heavy laser.

Avoiding the temptation to modify the stats something to reconcile these differences would need to be found.

The only thing that comes to mind is that the vehicle scale lasers have enormous cheap capacitors/batteries as part of the weapon. Thus the low power requirement (continuous trickle recharge vs direct power conduits on the ship weapons) and the increased size.

Personally I don't like that answer and IMTU have changed the power requirements for lasers to 10/100/200/200 and dropped the size of the heavy lasers to 350 VL. 200 EP does sound like a lot, but considering it is one-sixth of an EPhour (based on a 3 second combat round) it isn't really a hard thing to do with the capacitance of batteries being what they are.

 

[BetterThanLife]

Actually when you look at laser turrets (Or other turrets on a starship for that matter.) You will see they stick up above the profile of the ship. Since we are setting aside 1 ton internally, perhaps the difference is that which is on the exterior of the ship.

After all you are talking about adding less than 3% of the ships volume. (In starships, mind you, not small craft.) With vehicles you are generally looking at a much higher percentage and that would severely mess with your flight characteristics.

Perhaps the bigger size comes from having to have to have special lenses and transformers to increase your power output to the starship laser level. (Or additional lenses, etc.) After all a Starship EP is about 466 vehicle EP. (Based on fusion plant sizes.)

 

[BetterThanLife]

You will also note that the space aboard the "Standard Starships" for the "Standard Vehicles" is also allocated at the 1000Vl = 1DTon rate. (5 DTons for an Air/Raft that is 5000Vl.)

Originally posted by far-trader:
slyen2 asked a related question (here) and my answer might add some insight here so (cut and paste)...

I looked at this a while back and went with a straight kg = vl based on noting that the LMG in both sections (pg. 200 and pg. 247) are identical for TL, cost, damage, rof, and range. The only difference is one is 5.5kg and the other is 5.5vl.

Of course despite this and a couple other revelations* in digging around the book I'm not convinced this is correct but it works well enough.

* for example:

1 - The lowberth in the vehicle and ship sections cost the same and presumably function the same the difference is the first is rated as 500vl and the other is 0.5 Tons. This would lead me to think that 1000vl = 1 Ton. The official conversion though is 1400vl = 1 Ton.

2 - Compare the vehicle Heavy Beam Laser and Heavy Pulse Laser to the ship Beam Laser and Pulse Laser. The TL, costs and damage (adjusted for size) are the same. The difference is the vehicle ones are 1000vl (each) while the ship ones fit in 1 Ton (up to three in a turret). See the similarity?

I get the feeling some of the components were copied into the vehicle section using a straight 1000vl = 1000kg = 1 Ton. How simple and easy it would all be if that was the real way to do it. And how consistant. I'm tempted to just believe that is the case and ignore anyone (even Hunter) who says otherwise

But then there'd be so much I'd have to check and correct

 

[MrMorden]

As for the origins of the 1400vl = 1 ton conversion, if I remember my ancient Traveller history correctly, from CT Book 2, it mentions:

The volume of 1 metric ton of liquid Hydrogen = 1 displacement ton = 1400 liters.

I'm *sure* I will be corrected if I've misstated it.

 

[mike wightman]

It's 14,000litres (14 kilolitres), or 14 cubic metres, per displacement ton
Put another way, 1vl is 10litres...