Steve, thanks for the excellent tutorial... and the time and energy you put into it.
Wonderful!
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Steve, thanks for the excellent tutorial... and the time and energy you put into it.
Wonderful!
EXCELLENT tutorial Steve.
I’ve been getting a few emails from folks that are in the process of putting together their vacuum systems. I think that is great and know you will love the system once operational!
Wanted to let everyone know that it was politely brought to my attention that the air filters used in my system were actually installed backwards. According to the specs - the ¼” NPT opening is actually the output and the ½” barb is the input.
While I did disassemble each filter before placing it into the system so I could inspect the element and also make sure the filter was seated tightly against its O-ring, I saw nothing in the housing or on the element that would suggest air flow was unidirectional.
So, a simple test was called for.
I wheeled out my vacuum system and turned it on to find out what the vacuum was with the air filters in the original configuration. All I did was plug the end of the lathe adapter with a piece of plastic bag - the first reading was 24 hg. To determine if the air filter routing made a difference with regard to the air flow, I then disconnected the input filter to my system and tested for hg. It measured 24 hg. I then disconnected the output filter to make sure it wasn’t causing backpressure to the system and again tested for hg. It again measured 24 hg. So, about as un-scientific as you can get but I don’t believe the routing of the air filters change anything.
While this new information does not change the operation of the vacuum system, in my opinion, it nevertheless needs be presented so each individual can decide if they want to rig things differently or not.
There is one design change, as a result of this information, that would be worth considering and that concerns the exhaust air filter. If installed ‘correctly’ the Silencer/Muffler would then screw directly into the filter housing. That would clean up the exhaust area by eliminating some hose and a couple of brass adapters. Course, you would then require a different adapter to connect the ½” barb of the filter to the exhaust port of the pump. It’s always something, eh?
Hope the info wasn’t confusing. If you have questions, please let me know and I will do my best to answer them.
Steve,
Somehow I missed the reason for the exhaust filter. Is the vacuum pump oil-lubricated? Certainly looks like a dandy system.
Richard,
The vacuum pump uses graphite vanes and over time they will wear down. The filter was placed in-line to prevent that dust from blowing all over the shop.
Thanks, Steve. Did not think of that. Realized that I have a small piston-type compressor that I modified some years ago for use as vacuum pump, but never actually used it as such. Even if it works as originally intended, would need a surge tank and some baffles to smooth out the pulses. Something to try in spare time. Can always buy a real vacuum pump if it comes to that.
Steve,
I actually wondered about the input/output routing when I was building mine. I wasn't concerned enough to do the scientific test you have now performed, but I reasoned that going from smaller diameter to larger was probably to prevent back pressure in the filter. I also figured if it mattered the manufacturer would label the ports. Made sense to me when I was in a hurry to get mine working, but I'm not sure it does now.
In any case mine works great and I'm not messing with it. (Besides I don't want to have to make another 3/8” NPT(MIP) x ½” ID Hose Barb transition.):)
Chuck - I got an email from member Bob Justin and I hope that he doesn't mind but I would like to quote him with regards to this matter:
"My understanding for most filters has always been that the "Dirty" air or liquid should enter on the larger surface area of the filter and the smaller surface or clean side should route to the pump. For this application, I would want to have the visual in the filter housing as larger chips and dust build up so it can be cleaned as needed."
I also received an email from the person who first brought this to my attention and his concern - having not seen the filter - was that it could collapse under vacuum if it was designed for directional airflow. The test I ran and a description of the filter element (similar in construction to the reinforced paper filters used on Shop-Vacs) have alleviated his concerns.
So, the air filters will work in the system regardless of their orientation. I personally like the input filter installed the way it is - so I know when to clean it - but I may end up changing the output filter just to clean up the exhaust area a little bit.
Hope this helps.
Steve,
I've made a few of the chucks according to your plans. The first couple have too much wobble. I think the hot glue cooled too much before I got the pvc coupler seated. On the next ones I seated the pvc without the glue, then ran a bead of glue inside and out. They are much better.
I built a slight variation that has proved very useful for small items like boxes and lids. It's built the same way you describe up to the point before turning the shoulder for the coupler (through step 5). Instead of using the coupler, I simply covered the entire piece with the foam (except for the tapped hole of course). I drew some concentric circles with a sharpie to help with alignment. I'm amazed how well this holds small items with a flat surface or smooth rim, except when I forget to close the regulator valve, which has only happened twice now.
Thanks again to you for the plans, and to Tom Steyer for the adaptor.
Thanks for a great post, i learnt a lot from this.
Steve, I have seen a system (home built) that incorporated 2 short pieces of 4" PVC placed in-line to act as a vacuum reservoir in cases of lost power. Are you familiar with such an item and what do you think of it's usefulness?
David - have not heard of that particular version but sounds like it would work just fine. So far - knock on wood - I haven't worried to much about losing vacuum but things like that do happen!
Same thing as a pressurized tank in reverse. Instead of 120 psi positive pressure resevoir, you have a resevoir of 25"-28" Hg vacuum, mostly nothing in the tank except for a few stray molecules.. So the very maximum vacuum is equal to atmospheric of about 14.7 psi at sea level acting upon the surface of your tank. Quiet a difference compared to 120 psi of internal positive pressure. So why worry about a vacuum resevoir failing. Anyway which is worse and implosion or explosion? I don't know, never had either.Quote:
Originally Posted by David Haywood