How do I make this fakearm script work?

I want the fakearm to grow in size every second but it only does it instantly what do I do?

Char = game.Players.LocalPlayer
RS = Char.Character.Torso["Right Shoulder"]
run = game:GetService("RunService")
for i = 1,10 do
RS.C0 = RS.C0 *CFrame.Angles(0,0,-0.16)
end

Char.Character["Right Arm"].Transparency = 1
Fakearm = Instance.new("Part")
Fakearm.Parent = Char.Character["Right Arm"]
Fakearm.Size = Vector3.new(1,3,1)
Fakearm.BottomSurface = "Smooth"
Fakearm.TopSurface = "Smooth"
Run = game:GetService("RunService")
w1 = Instance.new("Weld", Char.Character)
w1.Part0 = w1.Parent["Right Arm"]
w1.Part1 = Fakearm
w1.C1 = CFrame.fromEulerAnglesXYZ(0,0,0) *CFrame.new(0,0,0)

Fakearm.Size = Fakearm.Size + Vector3.new(0,2,0)