I think you will have to make one yourself Davy or get someone like AngleRing to roll them up for you. I was talking to a guy doing a 9"Little Samson who cut his T section from an RSJ to get the correct internal radius and then had angle ring do the rolling.
Did you see the post about a month ago on TT about the three 4"BB1s being built there are quite a few photos of a homemade roller there, think I also posted the link here.
http://www.model-engineer.co.uk/forums/postings.asp?th=67930
5mm is a bit thick for an 11"wheel or is it that big single on the mole drainer? Can you not weld a ring into a rolled strip like most do on engine wheels. Or another method is to cut a groove into your rim material and when rolled that traps the leg of the Tee. I can post some pictures of this method tomorrow as I don't have the link on my ipad
J
Edited By JasonB on 17/05/2012 22:12:40