Why does this output error occur?

I'm trying to make the model 'Jericho 1' move as a whole (since there's more than one brick in the model) so I've set the Primary Part to Warhead1. Anytime I press the button, all I get is an output error saying "Unable to cast double to CoordinateFrame".

Jericho1 = game.Workspace["Jericho I"]
 Jericho2 = game.Workspace["Jericho 2"]

Warhead1 = Jericho1.Warhead
Warhead2 = Jericho2.Warhead

Jericho1.PrimaryPart = Warhead1
Jericho2.PrimaryPart = Warhead2



 function onClicked(playerWhoClicked)
   for i = 1, 500 do
    Jericho1:SetPrimaryPartCFrame(-31.209+i, 3.451, -126.11)

end
end

script.Parent.ClickDetector.MouseClick:connect(onClicked)

Could someone please tell me why this error occurs and/or what I need to do to fix it?

Thanks.