0
How do the Classic Battletech construction rules work?:
The 'Mech's engine (I'm only talking about Standard and Extralight Fusion Engines, which make up the vast majority of Battlemech Engines, and are the only ones available in MWO) includes ten heatsinks. These take up no additional weight, and might not end up taking critical slots either. The engine shares critical slots with up to one heatsink for every 25 points of engine rating, so an engine with a 250 rating or greater has all of its mandatory heatsinks integral to the engine (they do not take up any critical slots in the 'Mech. Additional heatsinks can be placed in the engine (where they do not take up critical slots, but still increase the 'Mech's weight) for every 25 points of engine rating over 250.
Furthermore, the 'Mech's Gyro also determines its weight based on the engine. Standard Gyros (the only kind currently available in MWO) weigh 1 ton for every 100 points (or fraction thereof) of the 'Mech's engine rating.
But the 'Mechlab looks a lot simpler than all that math!:
In the 'Mechlab, Standard Heatsinks require 1 ton and 1 crit (Double Heatsinks require 3 crits). Instead of having the 10 mandatory heatsinks as part of the "Engine" item (which would require a complicated system to allocate any "free" heatsinks that don't fit in the engine) the weight of any heatsinks that do not fit in the engine are subtracted from the engine's weight. These heatsinks are then placed normally, weighing 1 ton and taking up 1 crit as if they were normal heatsinks. Then a simple yes/no check of "does this 'Mech have 10 heatsinks" is made, and if the answer is yes, the 'Mech is able to launch. The way we know it works like this is that in the Closed Beta, this check had not been implemented yet, and it was possible to drop in 'Mechs with small engines and less than 10 heatsinks to gain additional weight for other systems (a COM-2D with 7x SHS and 3x SRM-6 is absolutely hilarious).
For Gyros, the actual "Gyro" item cannot be interacted with. Also, it has no weight. To prove this, strip all existing systems and armor from a 'Mech, you will get a weight of 3 tons (the weight of a Standard Cockpit which includes the Sensors and Life Support) plus whatever the weight of the internal structure is (1/10th the maximum weight of the 'Mech for Standard Internals, Endo-Steel halves this and rounds up). Because the Gyro's weight is entirely determined by the engine rating, the weight of the Gyro has been included in the weight of the "Engine" item in the 'Mechlab.
How does this affect my Urbanmech (or Panther)?:
The reason these 'Mechs would be so hard to implement with the current 'Mechlab is that their engines have very low ratings. The PNT-9R Panther has a 140 Standard Fusion Engine. This weighs 5 tons, and the Standard Gyro required weighs 2 tons. The engine has 5 internal heat sinks (25x5=125, 140-125=15, not enough for another heatsink). This means that the 'Mechlab decreases the "Engine" item's (and by this I mean engine and gyro combined) weight by 5 tons, since 5 Standard Heat Sinks would have to be placed in other critical slots. Therefore, a 140 Standard Fusion Engine would weigh 2 tons in the 'Mechlab (5 as per CBT, +2 for the Gyro, -5 for external HS).
But wait, that works out! I just have to put those other 5 Standard Heatsinks (or Doubles) in normally! It still weighs the same, right? Then why does the 'Mechlab only have engines with a rating of 150-400?
The problem comes when you try to use Extralight (XL) engines. These halve the engine's weight (rounded up) at the cost of side torso critical slots. Remember that the construction still follows the tabletop game's rules, so only the actual engine weight is halved, not the weight of the engine+gyro-some heatsinks that is an "Engine" item in 'Mechlab. If you took that stock Panther and replaced it's Standard Fusion Engine (SFE) with an XL Engine, that would decrease it's engine weight to 2.5 tons. Then you add the gyro weight of 2 tons for 4.5 tons. Unfortunately, the way the 'Mechlab is programmed you then need to subtract the weight of 5 Single Heat Sinks, which is 5 tons, greater than the weight of the engine. The 'Mechlab can't handle an item that has negative weight, especially based on how it could be exploited (see the part in the second section about Closed Beta). The Devs apparently want to have a Standard and XL Engine availabe for every rating that is possible, which is why they can't currently go below a rating of 150. (A 150 XL weighs 3 tons, +2 for the gyro, and it holds 6 internal heatsinks, so it only needs to subtract 4 tons for the mandatory heatsinks. This leaves an "Engine" item weight of 1.)
That's the Panther though, I want my Urbanmech!
The UM-R60 has a Standard Fusion Engine with a rating of 60. This weighs 1.5 tons, requires a 1-ton gyro, and holds only two internal heatsinks. If implemented in MWO, it's "Engine" item weight would be -5.5 tons. In all likelihood, the 'Mechlab is not programmed to use items with negative weights (Endo-Steel doesn't actually have a negative weight, when you "add" it you are actually replacing a heavier item.
So we'll never get the Urbanmech?!?
Not necessarily. Updates to the User Interface and the 'Mechlab are expected this summer or fall. These might include support for smaller engine ratings, although it is probably not a high priority. Also the possibility for such extreme customization (I have problems with the ability to install engines of any rating, since it opens engine/gyro weights up to exploitation) means that a UM-R60 would essentially be a SDR-5K with fewer hardpoints and a much lower maximum engine rating. However, some of the other Urbanmech variants would have unique hardpoints, and of course there are advantages to such a compact profile. It is somewhat telling, however that the only 'Mech statue or bobblehead that does not depict a 'Mech included in-game is that of the Urbanmech.
Edited by Joker Two, 24 April 2013 - 06:04 AM.
Troll with the Urban mech.
