Thoughts on my vac box attempt?

[TMerritt]

I'm brand new to CAD and to CNC so I'm learning as I go. I basically copied this box from a thread picture I found here on this forum. This will be for 4 of these motors here.

I'm wondering if I should put some exhaust fans on the bottom of the box instead of the curved exhaust vent on the bottom. I feel like this won't be enough area to vent the exhaust for both the vaccum and the motor cooling. What do you think? Box dimensions are 48" x 29.5". I'm not sure how to post up the file for it at this point but if I figure it out, I will.

[pkirby]

Good job learning the Fusion 360, I've been playing around with it and have enjoyed using it. As for the vacuum box, I built one almost exactly like that based off Gary's design (The Black Box) and also used a lot of info from the vacuum threads from Brady. I don't use my Shopbot constantly and have had the box built for about 2 years and about 100 hours into running 2 of the motors went out. One burned up and the other one's bearings/impeller fell apart. You could tell they were getting way to hot because the foam gasket I installed on the bottom of them had melted and deformed a good bit. After talking with Butch at Lighthouse motors about it, he informed me that the newer designs of this box have some extra design considerations to keep the motors from burning up. I'm not sure what they are and if I had to do it again, I would most likely just purchase the unit since it's now for sale (I think it's called the Hurricane). My current plan is to take apart my box and just mount the motors externally so there is plenty of air movement.

[jTr]

My black box was constructed the same, except the left and right panels. As shown in your draft, they contact the floor - on mine they are terminated at the same level as the box bottom, so the arched side is no longer the vent. I'm sure you can readily see a massive increase of exhaust air flow would be the result of this simple alteration.

As for the motors, get an outdoor thermometer. Attach sensor to housing of one of the primaries so you may monitor. My average temp is 114-124F with rare spikes hitting 130 ish. Original set of 4 are still going strong after 4 years of service in my full time shop. In reality, the secondary pair are almost never used- I now regard them more as backups if I ever do toast a primary.

Monthly, I average 20 hours use, so it's pretty light, but I'm more than confident your design with the slight mod to allow ample air flow should serve you well. Also, be certain to use lock washers in fastening motors so you can make them snug and secure without over-torquing. If you get too heavy handed, you may squash the housing, resulting in impeller rub = heat and death.

Hope that helps - looking good!

Jeff

[TMerritt]

Thanks for the advice fellas. I really like the outdoor thermometer idea.

jTr, how is the noise level on your box with the sides cut at the same level as the last baffle? That was my concern with cutting the sides like that. I have to sit next to this thing while it's running and I didn't want it to get too obnoxious. I'm actually thinking of layering the baffle section with sound deadening material to help with that. Maybe open or closed cell foam glued in place, but I haven't done my homework on that yet.

I've also just found some 6" duct fans that flow 240 CFM and are pretty cheap, so I'm toying with the idea of using 2-4 of those per side and helping the flow along instead of making the vacuum motor do all the work of pushing the air out of the baffles.

[jTr]

how is the noise level on your box with the sides cut at the same level as the last baffle?

Unbearable without ear protection. However, this is to be expected for most any vac source, more or less. Moreover, I don't feel the described modification has much effect on the noise levels. However, I do feel a wide open motor, as opposed to the box, would be significantly higher in Db's.

I'm actually thinking of layering the baffle section with sound deadening material to help with that.

I agree- I used acoustic ceiling panels, rough cut and adhered within the exhaust chamber and interior. Very cheap aid in sound deadening.

just found some 6" duct fans that flow 240 CFM and are pretty cheap, so I'm toying with the idea of using 2-4 of those

Feel free, though from my experience, I'd save the bucks and try without to start. Remedy only if deemed necessary as you monitor heat. Temps quoted matched Gary's averages per older posts, so I'm comfortable with that range. Again, that's 4+ years of trouble- free operation.

Good luck!

Jeff