I agree with your previous comment regarding not wanting the dust from inside of the DC-3300 to get into the motor, so I think you have no choice but to seal off the motor housing compartment from the inside of the DC-3300. At least, that is my opinion. So, if the motor housing is sealed on the one end and open on the back end to the outside, then I agree this is less than ideal for cooling the motor. What I envision is that there will be some natural convection that results in a small amount of heat to escape from the motor to the ambient air inside the motor housing and eventually expelled with natural convection currents out the back vented opening of the DC-3300. However, with the addition of that crude fan on the back of the motor it should blow even more hot ambient air from around the motor and expel it out the back. When it does so, it will create a bit of a negative pressure situation in the air around the motor housing causing more air turnover between this motor housing air and the air outside the DC-3300. If the fan is blowing air out, then I expect makeup air to be sucked in on the periphery around the diameter of the fan until it reaches the backside of the fan. It may short cycle a bit, but it should work to crudely cool the motor. Due to 2nd law of thermodynamics, heat will naturally flow from an area of higher heat to an area/object that is cooler, so this will cool the motor, but the real question is whether it cools it fast enough to keep the thermal rise down. Only way to know for sure would be to thermocouple the motor and test it with & without sealing the front of the motor housing. Just have to keep the motor to a reasonable temperature to not degrade its performance/longevity, so this cooling system doesn't have to be perfect. Remember active cooling is about managing thermal rise, not preventing any rise, so as long as that crude plastic fan keeps hot air moving away from the motor such that the motor stays under its thermal design limit then it should be "okay".DLB wrote: ↑Fri Aug 27, 2021 1:38 pm Yes, it is a plastic cooling fan and blows warm dusty air out the back through the grate. But where is that air coming from? Mine is only a subjective opinion. But the fan is recessed in the housing. And the grate is considerably smaller than the opening in that pic. So I seriously doubt that the fan is moving an appreciable amount of cooling air over the length of the motor case. I'm not a fluid dynamics guy, but I see no way that this fan is pulling shop air through that grate, routing it back along the outside perimeter of the housing, and then back along the motor case and out the front through the same grate with no ducts. What I see when I look at this more oven like. I suspect the fan and motor case are designed for cooling in free air, preferably mounted vertically with the fan at the top.
I know a lot more about the leak now than I did when I duct-taped this. The tape was quick and dirty to help me definitively determine between a couple of possible/probable sources, and it was already in stock. It was also enough to satisfy me that this thing has serious cooling challenges. I don't think I had it fully sealed, at the time I had no intent to fully seal it unless/until I get a new motor housing.
- David
Just trying to think of ways to improve what you have got. Another option would be to mod it to have a PVC inlet near the front of the motor housing and connect this to outside, clean air, but this new inlet might be difficult to seal inside the DC-3300. Also, it doesn't look like that great of a fan on the back of the motor, so I am not sure how much airflow would actually flow through a new air inlet if you created one. An alternative might be to use small computer case fans mounted in the 4 corners on the inside of the motor housing with a push-pull configuration to help exhaust more motor heat out the back of the DC-3300 while simultaneously pulling more air in with the pulling (computer) fans.