Get this crash when trying to start with "Mechanical" part of ProjectRed
Time: 12.02.15 18:44
Description: Exception in server tick loop

cpw.mods.fml.common.LoaderException: java.lang.NoClassDefFoundError: mrtjp/projectred/transmission/PowerWire_100v
at cpw.mods.fml.common.LoadController.transition(LoadController.java:162)
at cpw.mods.fml.common.Loader.preinitializeMods(Loader.java:514)
at cpw.mods.fml.server.FMLServerHandler.beginServerLoading(FMLServerHandler.java:88)
at cpw.mods.fml.common.FMLCommonHandler.onServerStart(FMLCommonHandler.java:313)
at net.minecraft.server.dedicated.DedicatedServer.func_71197_b(DedicatedServer.java:114)
at net.minecraft.server.MinecraftServer.run(MinecraftServer.java:374)
at net.minecraft.server.MinecraftServer$2.run(MinecraftServer.java:669)
Caused by: java.lang.NoClassDefFoundError: mrtjp/projectred/transmission/PowerWire_100v
at mrtjp.projectred.ProjectRedExpansion$.preInit(ProjectRedExpansion.scala:28)
at mrtjp.projectred.ProjectRedExpansion.preInit(ProjectRedExpansion.scala)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
at java.lang.reflect.Method.invoke(Unknown Source)
at cpw.mods.fml.common.FMLModContainer.handleModStateEvent(FMLModContainer.java:513)
at sun.reflect.GeneratedMethodAccessor3.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
at java.lang.reflect.Method.invoke(Unknown Source)
at com.google.common.eventbus.EventHandler.handleEvent(EventHandler.java:74)
at com.google.common.eventbus.SynchronizedEventHandler.handleEvent(SynchronizedEventHandler.java:47)
at com.google.common.eventbus.EventBus.dispatch(EventBus.java:314)
at com.google.common.eventbus.EventBus.dispatchQueuedEvents(EventBus.java:296)
at com.google.common.eventbus.EventBus.post(EventBus.java:267)
at cpw.mods.fml.common.LoadController.sendEventToModContainer(LoadController.java:208)
at cpw.mods.fml.common.LoadController.propogateStateMessage(LoadController.java:187)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
at java.lang.reflect.Method.invoke(Unknown Source)
at com.google.common.eventbus.EventHandler.handleEvent(EventHandler.java:74)
at com.google.common.eventbus.SynchronizedEventHandler.handleEvent(SynchronizedEventHandler.java:47)
at com.google.common.eventbus.EventBus.dispatch(EventBus.java:314)
at com.google.common.eventbus.EventBus.dispatchQueuedEvents(EventBus.java:296)
at com.google.common.eventbus.EventBus.post(EventBus.java:267)
at cpw.mods.fml.common.LoadController.distributeStateMessage(LoadController.java:118)
at cpw.mods.fml.common.Loader.preinitializeMods(Loader.java:512)
... 5 more
Caused by: java.lang.ClassNotFoundException: mrtjp.projectred.transmission.PowerWire_100v
at net.minecraft.launchwrapper.LaunchClassLoader.findClass(LaunchClassLoader.java:188)
at java.lang.ClassLoader.loadClass(Unknown Source)
at java.lang.ClassLoader.loadClass(Unknown Source)
... 33 more
Caused by: java.lang.NullPointerException

Think you need transmission.

Big thanks, I just forget to install it:)