Like all newbies I'm probably asking something that has already been answered but here goes. I've succeeded in building a circular tube 325 mm high and 214 mm external diameter with wall thickness of 4 mm. I now need to make this tube oval but not a real oval more like a running track with half circles at each end and in my case with straight sides of 50 mm joining the two halves of the circle Thanks in advance Keith
Since I don't really know your topology, I better start from scratch. If I interpret your question right, here's how I would approach it:
I assume a Blender unit to be 1 meter. I don't use metrics, so you might have to adapt your values.
Create a cirle. In the redo panel to the left, enter the desired resolution (I chose 64) and as radius, enter .214/2
Go into Edit Mode with TAB, hit A to clear the selection and use B to select half of it (you could do a negative border select with MMBand spare the A).
Then press Y.
It's called split and will duplicate the verts at the border of your selection. In this case it means you now have two half circles. One is selected, one isn't.
With the right half still selected, move the right circle to the right with GX .05 RETURN, right?
Select all with AA and fill it with F
Inset the face with I .004 RETURN
Delete the inner face using X, "Only Faces"
The finished tube with, I hope, the right dimensions.