The relevant Model Engineer articles are as follows:
1994, Vol.172, Issue 3966, page 435. Original descriptive article with drawings.
1994, Vol.172, Issue 3970. page 670. Editorial: Clarification as to fuel to be used.
1997, Vol.179, Issue 4047, page 144. Update: blast nozzle increased to 2.9mm diam., pseudo brick arch added (with drawing of arch), importance of lubrication.
If you cannot source these I may be able to assist with further information. Just send me a Private Message with your email.
Regards,
Phil