I put mine inside the pipe, used a spring for an exhaust pipe off a honda. I compressed the spring a little so it would hold the damper where I wanted it.
For what it's worth ACE Hardware has cast iron ones down to 4 inch ...
And on the eighth day God created barbecue …. because he DOES love us and he wants us to be happy.
Current smokers: Egor (trailered RF) and Easybake (tabletop pellet drive)
TQ, I prefer top dampers. The reason being for me the only reason I have one at all is to keep rain, bugs and what not out of my cookers. For the most part all my builds run the stacks full throttle and adjust temps through the intake. Internal dampers do little for inclement weather they just look cool.
TQ, yes as PressureRanger posted it is a 1/8" x 1/2" flat wrapped on the damper to act as a stop. It is over run about an 1/8" to clip the circumference and hold the damper in place when closed. My Good Friend Jan Olav from Norway was down for a week and we were working on the grill he came up with the design.
Here are a few more pics that may help.
Very good Kam that is what I like learning from people. My dad was a master craftsman and he always told me Pay attention !!!! that he had learned a lot from what some peole called helpers>>>> That statement does not insinuatethat you are a helper basially he was saying evryone has something to offer and that is soooo true!!!!!! let me ask do those type of dampers have a problem coming open going down the road????? brother you do a jam up job on your builds I can tell you have a lot of experience!!!!!
Thank You TQ, if you balance the damper on the barrel and do not let it drag on the stack a bit it more or less free floats and will open during transit. What I have started doing is adding the tab on the damper and drilling a 1/2" hole for my rod to go into. This allows me to seat the damper to the stack face with a little friction while the weight of the rod handle and damper more or less keep it closed. It is not perfect but during the travel to the painter (about 30 miles from home) none of the stacks drifted open.
I hope this helps.