There was a web site that had a home built smoke generator in it. The author used some brass to fabricate a box, and then added a smoke generator (I think from a ship) and a small computer fan to blow the smoke out. He attached the fan to the motors so that the fan would blow harder at above idle, hence more smoke coming out of the tubes. He is in the process of rebuilding his web site right now, so the links to the project are not available. His site address is: http://www.tanksandtrolls.co.uk/home.htm. I got that info from the site that we are not allowed to post links to. If you email me I'll give you the form address so you can get the other info from the post.