On the subject of the spring loaded starter - regen braking system and what have you...
Large engines... I mean LARGE engines use compressed air to start... Lets have a regen compressor charge a tank and have a compressed air motor start the engine or at least put some power to the wheels
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For long haul applications... convert to a turbine engine.
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Waste exhaust heat? Install an ammonia refrigeration system on your exhaust manifold... Recycled heat into air conditioning... Actually, I've always wanted to try this - by converting a continuous cycle propane fridge
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Air Brake turbines for regen braking... seems rather inefficient, but hilarious.
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Electric powered 5th (or even 6th) wheel... A hybrid conversion :P
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It's late... and I'm fried :P
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