After the workbook is saved the chart on the first worksheet disappears (Input.xlsx).
I then copied the worksheet to Input 2.xlsx, deleted the chart and pasted it in again and the chart isn't lost but the chart loses the check on the "Right Angle Axes" property on the 3-D rotation tab.
Dim excel As Workbook = New Workbook(Application.StartupPath & "\Input.xlsx")
excel.Save(Application.StartupPath & "\Output.xlsx")
David