Why does the +vector3.new/-Vector3.new not work?

local enabled = true
Player = script.Parent.Parent
character = Player.CharacterAdded:wait();
mouse = Player:GetMouse()
Run = game:GetService("RunService")
Head = Player.Character.Head 
function onKeyDown(key)
    key = key:lower()
    if key == "r" then
        game:GetService("Chat"):Chat(Player.Character.Head, "REN!")
        r = Instance.new("Part")
        r.Shape = "Ball"
        r.Transparency = 0.7
        r.BrickColor = BrickColor.new("White")
        r.TopSurface = "Smooth"
        r.BottomSurface = "Smooth"
        r.CanCollide = false
        for i = 1,20 do
        r.Size = Vector3.new(r.Size.X + 1, r.Size.Y + 1, r.Size.Z + 1)
        wait()
    end
        for i = 1,20 do
        r.Size = Vector3.new(r.Size.X - 1, r.Size.Y - 1, r.Size.Z - 1)
    end
        r.Parent = workspace
        Weld = Instance.new("Weld")
        Weld.Part0 = r
        --Weld.C0 = r.CFrame:inverse
        Weld.Part1 = Head
        Weld.Parent = character 
    end
end

mouse.KeyDown:connect(onKeyDown)

Thanks for helping me.