A Study on Engines

[Scotty]

A couple weeks back, I decided to sit down and have some fun with the BattleTech construction system.  I took the tonnage and walking speed of 'Mechs, and determined how much tonnage left over after picking an engine that a given 'Mech (using standard everything except engines, in most cases) would have for weapons and equipment - and then comparing those to each other to determine 'optimal' arrangements, both by speed and by TMM achieved.  Separate pages I did for the inclusion of jump jets.  Future pages will include differing cockpits, gyro types, and structure types.  Hardened Armor will also be considered due to its reduction in run MP that affects the TMM achieved.  Improved jump jets might get a revisit, but those promise to be tricky.

Some notes on the first upload:

• 65 ton machines are in general not efficient in terms of payload space given standard construction equipment.  The only exception to this is the LFE, which is overall not very efficient itself.
• The 65 ton frame is capable of inflicting the single most damage on a single charge at a whopping 77 points at a dead sprint.  This is only capable with at 7/11 with a 455 rated engine, leaving half a ton for armor and weapons.  Incidentally, the 455 rated engine is the single highest rated engine to appear on this list in any capacity.
• The 75 ton frame had the highest number of 'most efficient' billets (technically the 100 tonner made more, with 13, but 12 of those were for speeds 1, 2, and 3, which are pretty much the 100 ton frame's domain by default.  Doesn't count), making appearances in six graphs.  The only two exceptions were the LFE graphs.
• The LFE had the highest number of 'useless' ratings, in which there was no tonnage saved from the next larger engine (in this case, SFEs).  13 of the LFE's entries duplicate the SFE's entries, compared to 2 for XLEs, and 4 for XXLs in comparison to LFEs and XLEs respectively.
• To my mild surprise, there was not a single instance with either of the four engines tested (SFE, LFE, XLE, XXL) in which the optimal tonnage for a smaller 'Mech was greater than the optimal tonnage for a larger 'Mech.
• The only 'Mechs capable of reaching an incredible +6 TMM on this list are all 30 tons or lighter.
• The optimal speeds for both 30 and 35 ton 'Mechs were the same across all tournament legal engines.  XXLs predictably skewed the average.
• The highest jump speed possible with an XXL (and otherwise standard materials) is a whopping 13 hexes on both 20 and 25 ton 'Mechs.  This leaves one ton for weapons and armor.

More thoughts to follow as I build more tables, but for now enjoy the fruits of my labor.

[Kitsune413]

Interesting charts

[House Davie Merc]

Given the ability to customize -
I've always preferred the 75 ton frame for ANY tech level .

It just seemed to have the best possible combinations of mountable armor, speed,
weapons load out , and anything with more weight available seemed to run out
of crit slots to quickly to take advantage of the additional tons made available
using 3050 + tech .

A 3050 + Marauder-D variant can be made to move 5/8/5  and can carry an impressive
amount of armor and usable weapons .
Even with I/S tech  it's a beast for the Clanners .
Similarly a 3025 MAD-D that moves at 3/5/3 is a complete monster in 3025 era play .

75 tons  seems to be a sweet spot that unfortunately has NOT been utilized very well
in many canon designs .

[SCC]

OK, this confirms something, weight for tonnage Light 'Mechs don't do very well. At the lower speeds 6/9, heavier 'Mechs are a better choice. at the higher speeds, 8/12, your getting into hovercraft territory.

Now, as for the colors, the bands along the top show TMM brackets, light blue means best choice in TMM bracket, green means best choice at speed, red means worse choice for speed, less free tonnage and weighs more. Grey-Green means no more tonnage then worse engine, and grey means?

[Scotty]

The bands along the top show TMM brackets.
Light blue means best choice in TMM bracket.
Green means best choice at speed.
Red means that there is a better choice at a lower tonnage for the same speed - notable because that's an effective cost saving measure.
Yellow means 405+ rated engine.
Grey-Green (it's supposed to be brown) means that the engine in question is the exact same tonnage as the next worse engine - LFE compared to same-rating SFE for example.
Grey means that the engine in question is the exact same tonnage as the next speed in the same engine type and weight.  It's only on there a couple times, but it indicates where upping to the next engine size is stupidly obvious because you don't lose a single half-ton to do it.

Regarding the 75 ton frame in 3025: it's actually better in every way to use the 80 and 85 ton designs when moving 4/6.  At that speed, all of them have the same tonnage remaining: 42.5 tons.  However, the 80 and 85 ton designs have higher internal structure and more powerful physical attacks - but the same jump jet size and room for weapons.  You can take any 75 ton design, transplant it onto an 80 or 85 ton machine, and the 80 or 85 ton machine will be objectively better.  This goes out the window when bringing XLs into the equation, but for SW tech the 75 ton frame is actually one of the least efficient use of resources in the game with regards to "could do better" potential.

OK, this confirms something, weight for tonnage Light 'Mechs don't do very well. At the lower speeds 6/9, heavier 'Mechs are a better choice. at the higher speeds, 8/12, your getting into hovercraft territory.

After this table is complete, I'm going to start on vehicles.  Naturally, the most interesting thing to do with those tables will be to compare where and how 'Mechs stack up.  One huge advantage that Scout 'Mechs have over scout hovers is the ability to traverse woods and forests, and to vault vertical obstructions.  Obviously VTOLs don't have this problem, but it's going to be interesting to confirm or bust the myths about hovers versus Lights.

EDIT: Breaking news from the IJJ section of the graph.  Just experienced the very first local minima in any graph during the jump from 55 to 60 tons with more than 3 IJJs.  The tonnage increase really screws bigger 'Mechs over, particularly along the divisions.

[SCC]

That whole argument about vehicles having trouble moving through trees is that for scouts speed is important, and moving through trees tends to kill speed

[Scotty]

It does not kill jumping speed, however, which is where 25 and 30 ton designs excel.  Besides which, I rather like being able to know what's on the other side of a given obstacle, and a scout running through woods, even if not jumping, is still faster than a non-scout running through those same woods.

[House Davie Merc]

Regarding the 75 ton frame in 3025: it's actually better in every way to use the 80 and 85 ton designs when moving 4/6.  At that speed, all of them have the same tonnage remaining: 42.5 tons.  However, the 80 and 85 ton designs have higher internal structure and more powerful physical attacks - but the same jump jet size and room for weapons.  You can take any 75 ton design, transplant it onto an 80 or 85 ton machine, and the 80 or 85 ton machine will be objectively better.  This goes out the window when bringing XLs into the equation, but for SW tech the 75 ton frame is actually one of the least efficient use of resources in the game with regards to "could do better" potential.

Different way to think about it :
If your pushing for the lightest unit with the best capabilities at 4/6 the 75 tonner is better .

It's a HEAVY mech that can carry as much firepower as an 80 or 85 ton assault .
Lighter with the same projected capabilities ( firepower) can be cheaper C-Bill wise
as well as easier to transport and repair .

If jump jets are desired - IIRC at 85 tons you have to get heavier JJs .

If your using introtech with a 3/5/3 movement the cost of the unit goes way down .

If you want a 5/8/5 with an XL for 3050 + 80 tons and up isn't as efficient .

[Scotty]

Wrong on most counts.  It's not more difficult to transport (one 'Mech bay: one 'Mech).  85 ton 'Mechs still have one ton jump jets.  It's cheaper C-bill wise, but the 85 tonner has objectively better capabilities thanks to the increase in internal structure points to keep it alive, even with identical armor.

At 3/5/3 the 75 tonner has 48.5 tons to play with.  The 85 tonner has 54.5 tons (both with standard engines).  The disparity closes, but the absolute ceiling remains with the 85 tonner regardless of engine.  Only when moving 5/8 or faster is the 75 ton frame superior.  At that point (once you get LFE or XLE) the 75 tonner is the most efficient frame in the game.  At 5/8 SFE, however, the 60 tonner is superior, by seven full tons!

XL engines throw off the equivalency, but you might be interested to note that the 80 ton frame only loses by 2.5 tons when going 5/8/5 - and actually wins (and handily!) when going 3/5/5.  The 85 ton frame is actually the second most efficient way to jump 5 hexes (47.5 tons available for weapons and armor, which actually out-payloads the 75/80/85 tonners at 4/6!), and it is beaten only by the LFE and XLE 3/5/5 100 tonner.

This kind of stuff is exactly the reason I started doing this in the first place.  The 75 ton sweet spot does not actually exist in 3025.

[Thatguybil]

This kind of stuff is exactly the reason I started doing this in the first place.  The 75 ton sweet spot does not actually exist in 3025.

Yup and 4/6 85 tons with SFE and double heat sinks beats 4/6 75 tons with SFE and DHS in the spare crits.

[Kitsune413]

I get really excited about math. :)

[SCC]

It does not kill jumping speed, however, which is where 25 and 30 ton designs excel.  Besides which, I rather like being able to know what's on the other side of a given obstacle, and a scout running through woods, even if not jumping, is still faster than a non-scout running through those same woods.

Jumping is another matter, but for most patches of woods on a game board it probably doesn't take any more MP to go around then it does through

[Scotty]

While this is true, there's something to be said in terms of intangibles like momentum.  It's much "faster" regardless of the actual duration of the maneuver to simply vault those trees in your way than it is to scope out a route around them.  Strategic operational speed would be significantly impeded with a slower ground design or hover that had to continually disrupt its route or take detours, leaving aside that such detours create holes the enemy can slip through.  On a pair of mapsheets, that's not especially relevant.  Then again, on a pair of mapsheets you'd probably not need a scout at all.

Anyway, to round out this post: would folks prefer it if I posted the updated graph immediately after finishing CFE and IJJ tables, or wait for things like Endo-Steel and alternate gyro types first?

[Khymerion]

Wait a bit and give more data.  Never wrong to have more data to comb over.

[Scotty]

Massively re-organized the charts for ease of viewing and comparison between different engine types with otherwise similar characteristics.  Color coded and consolidated sheets.  Added key, updated charge damage tab.  Added Compact engine and associated jump jet tables.

Next on the to-do list is to do an exhaustive list of all gyro combinations with all engine combinations and jump jet combinations.  It's going to be it's own document, and is probably going to be huge.  Until then, enjoy.

[Diablo48]

Wrong on most counts.  It's not more difficult to transport (one 'Mech bay: one 'Mech).  85 ton 'Mechs still have one ton jump jets.  It's cheaper C-bill wise, but the 85 tonner has objectively better capabilities thanks to the increase in internal structure points to keep it alive, even with identical armor.

At 3/5/3 the 75 tonner has 48.5 tons to play with.  The 85 tonner has 54.5 tons (both with standard engines).  The disparity closes, but the absolute ceiling remains with the 85 tonner regardless of engine.  Only when moving 5/8 or faster is the 75 ton frame superior.  At that point (once you get LFE or XLE) the 75 tonner is the most efficient frame in the game.  At 5/8 SFE, however, the 60 tonner is superior, by seven full tons!

You forgot a few other important advantages to the larger frame.  First is that Endo-Steel works better on larger frames so you can actually pull ahead of the heavy in total mass with that.  Second, the larger engine lets you stow more Heat Sinks in the engine which is very important once DHS come around.  Third and most important, the way BT is balanced, you usually want more armor than the rules allow you to mount for optimal balance between offensive and defensive power so the extra armor capacity of the larger frames is a major advantage.

XL engines throw off the equivalency, but you might be interested to note that the 80 ton frame only loses by 2.5 tons when going 5/8/5 - and actually wins (and handily!) when going 3/5/5.  The 85 ton frame is actually the second most efficient way to jump 5 hexes (47.5 tons available for weapons and armor, which actually out-payloads the 75/80/85 tonners at 4/6!), and it is beaten only by the LFE and XLE 3/5/5 100 tonner.

That 100 ton, 3/5/5 optimal point is hilarious to exploit on the Dire Wolf.  The crazy thing moves like a heavy in tight terrain while packing far more armor and firepower than they can ever hope to.