switch to signed values for items

src/trainjs.cpp

@@ -66,7 +66,7 @@ void TrainJs::axisChanged(const int id, const int axis, const qreal value)
 	{
 		if(std::shared_ptr<Item> workitem = item_.lock())
 		{
-			uint8_t newValue = (value+1)*7;
+			int8_t newValue = value*14;
 			if(newValue != workitem->getValue())
 				workitem->setValue(newValue);
 		}