Engine differences with unit tonnage?

[jh316]

What's the difference between a 300 rated fusion engine in a 100 tonner and the same engine rating in a 75 tonner?  A lot of vehicle fusion engines ended up stripped to repair mechs during the succession wars, but since it appears engine cost is a factor of rating and unit weight, that stripping engines like that would be questionably useful as only a few very specific designs of the exact size and speed of the tank could use them. For example, a Von Luckner's 75 ton chassis with a 225 rated engine doesn't correspond to any mech around in 3025 (which might explain why it's one of the few tanks that still had fusion engines).

[jh316]

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[jh316]

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[jh316]

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[cray]

Hmm. I was going to say that the salvage rules of Strategic Operations (p. 191) ignored the unit's tonnage - if you got a 300-rated engine, you had a 300-rated engine that could go in another unit that used a 300-rated engine (per the replacement rules starting on p. 181). I tried to address common questions about fusion engines in Tech Manual's engine fluff section (p. 35-37), like oversized engines, but apparently didn't address the matter of sharing engines between units of different tonnages.

However, Strategic Operations' p. 180, "Stockpiles, Buying and Selling" section states, "Because engine costs are based on the tonnage of the unit and its engine rating (as well as a pre-determined number and type of heat sinks included), engines must be matched to the unit’s tonnage and Walking MP (and heat sink type, for heat sinks outside the engine)."

So I'll say, "You can only swap engines between units of the same tonnage and cruise/walking movement." [edit] A game balance issue addressed by that is the possibility of someone buying a low-tonnage, inexpensive version of an engine and installing it in a larger unit. [/edit]

That said, the Customization Rules (p. 188) address engine type changes as a Class F refit. That'd be a conservative way of turning a 50-ton 'Mech's 300-rated engine into a 100-ton 'Mech's 300-rated engine.