function drawtrainhealth()
    for k, v in pairs( ents.FindByClass("func_tracktrain") ) do


        -- check if it's really a func_tracktrain
        if v:GetClass( ) == "func_tracktrain" then
            -- change the Vector in LocalToWorld to change
            -- where the text should appear in relation to the ent
            local pos = v:LocalToWorld(Vector(0, 0, 100)):ToScreen()
            -- check we can actually see this part of the entity
            if pos.visible then
            -- what info to draw

                draw.DrawText( tostring( v:Health() ),
                    -- what font to draw it in
                    "Default",
                    -- where to draw it
                    pos.x, pos.y,
                    -- what colour it must be
                    Color(255, 255, 255),
                    -- how to align the text
                    TEXT_ALIGN_CENTER
                )


            end
        end
    end



end
hook.Add("HUDPaint", "ShowHealthAboveEnt", drawtrainhealth )