I saw some expensive thermostatically controlled blowers being sold for forcing more air into the air intake of various smokers, and was pretty floored that they get $300 for some of these things. I thought about it and the times I would really want to stoke my firebox would be to help it heat up faster during initial starting, and to help re-heat again after opening a door. For those uses it probably isn't necessary to get fancy with a sensor and a control circuit. A simple switch, and maybe even a few variable speeds would do me fine.
I took a look at my Oklahoma Joe Longhorn Offset Side Firebox Smoker/Grill and realized that the air intake butterfly has a post/lever that could support a plenum, and all I would really need to build a plenum would be a 9" diameter and couple of inch deep stainless steel pie pan. I found one for $5. The post is 2.800" away from the center pivot, and the post is 0.4375" diameter (7/16").
I had a few extra muffin fans left over from an electronics project, so one of them would do. The fan I picked is a NIDEC TA450DC 12 VDC (nominal) Muffin Fan that was purchased at a deep discount ($10). It has a cast metal frame and a ball bearing motor and is rated to operate over a voltage range of 7 - 14 VDC while drawing 0.47 Amps. Life is specified as 57,100 hours. The fan is rated at a maximum of 112 CFM (cubic feet per minute) operating at its nominal rating of 12 VDC but will pump less air at lower voltages.
I marked up the pan finding its center and making my post hole 2.800" from the center and then positioned the fan below the post hole and traced it on the pan. I drilled the holes and used a hand nibbler tool to make the big hole for the airflow. Then I used a brass hammer with a small anvil to flatten the nibbled edge.
I assembled the fan and added a length of high temperature wire I had on hand (red/black twisted pair #18), with a double banana plug hi-fi connector at the end.
I already had a small 12 VDC switching power supply that had cost $20 from a discount electronics supplier that would provide the juice. It is capable of 12 VDC at 2 Amps, and also has settings for 9 VDC, 7.5 VDC and 6 VDC that will run my fan at maximum airflow (12 VDC setting), and allow several lower levels of airflow as well. This would be the easiest way to get going but there are many options for power including using a 12 VDC battery with switched voltage dropping resistors or a power rheostat for variable voltage/speed, but that all could come later.
I expected to have to run a die over the steel post on my butterfly to thread it to accept a wingnut to hold the pan in place, but decided to try things out by just slipping it on and letting it hang - and amazingly it stayed in place just fine, so no need to even figure out which die to use and then find a wingnut.
So this little project represented $35 of parts, most of which I already had on hand, and it will stoke the fire for sure since the maximum airflow of the fan I used is rated as 112 CFM. Now I need to try it a few times and see if it helps!
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