After years of looking at my cardboard-box chimney and thinking it was the weak point of my set-up, I wandered around Home Depot for a while looking for a better solution. My goal was to connect the back of the Hottop to 4" flexible dryer ducting and up to my range vent hood.
Last weekend, I succeeded.AFTERBEFORE
I wanted it to be quickly removable and not require any permanent modification to the Hottop.
I came up with something that works surprisingly well and requires no cutting or drilling.
I discovered that a toilet flange is perfect for this and the ones at Home Depot are black!
Furthermore, they have a slot which allowed me to easily create a bayonet-like attachment.
They come in a view varieties. Find the one that allows your venting to slide snugly over it.
Once you have the supplies, it should take less than 30 minutes to do.
Here's what you need to do:
1) Remove the rear fan assembly and replace the top two M4 X 30mm machine screws with small lockwasher and M4 X 45mm screws (I had 50mm so they stick out more than I'd like - I'm waiting for 45s and some M4 flange nuts ordered off ebay for a neater job). Make them very snug so they don't loosen when you start tightening things on the other end which will tend to turn these screws CCW.
Reassemble. You will now have two screws sticking out the back of the Hottop.
2) Place a couple small lockwashers (M4 or similar so they just fit over the screws) on these screws and then a 1/4" X 3/8" OD X .171 ID nylon spacer. Now put another lockwasher followed by a #8 washer then an M8 washer. The M8 washer is the perfect size to fit through the largest opening in the toilet flange and the spacers fit perfectly in the groove. If you can find a fender washer with the same OD as the M8 washer but much smaller ID then you might not need the #8 washer. Next put another #8 washer followed by a lockwasher, then an M4 nut. You may find hardware that's slightly different but the key is that the fan screws are M4, an M8 washer is the perfect OD to just fit through the largest gap in the flange and the spacers fit right inside the groove in the flange. The small lockwashers help keep everything snug and allow for fine-tuning to get the perfect gap between the roaster and the M8 washer.
3) All that's left to do is to slide the venting over the flange. I used venting with collars as they fit right over the flange. I decided to secure the venting to the flange with vent tape.
At the other end, I used vent tape to secure a small stainless steel hook which keeps it in place on my range vent. I also wanted to vent tape to smooth out some of the rough/sharp edges.
To attach the vent assembly to the Hottop, line up 2 of the large square openings on the flange with the 2 washers on the Hottop and turn the flange as far counter-clockwise as it'll go. To remove it turn it clockwise.
If you want a solution that doesn't allow for instant removal then you can replace all four M4 screws instead of just the top two. Then use the four holes in the flange rather than the slots. Drill the holes in the toilet flange a little larger so they all match up with the four screws (40 mm length screws might work). Then use a small lockwasher and whatever washers and M4 wingnut, M4 regular nut or M4 flange nut you need to secure all 4 points.
Obviously, this can be modified for different specific venting needs. The key is that the flange is almost perfect for this.
When I'm not using it, it hangs on a little hook in the basement.
Everything's available at Home Depot that's needed. Total cost is <$20. They don't have 45mm M4 screws and they may not have M4 flange nuts but as described above, those are optional; the stainless steel hook didn't come from there either. To make sure everything fit right, I took the rear fan cover to Home Depot with me and semi-assembled everything there. I roasted today and it worked great. Despite only being attached at the top of the fan, no smoke leaked and there's little play.