Very cool to measure free flow air delivery I have used a garbage bag in a wooden box built to a known volume and drill a few holes around the box to help air in to box to escape as the bag inflates and one bigger hole in the top that you can use to see when the bag is full You can also use the bigger hole to measure pressure as you know surface area of the hole if you put a weight on top of area to work out the pressure
You could try to keep the vase mode outer shell and then print a smaller infilled rotor that you can "screw" inside of the vase shell, that way you save on the post processing of the rotor, get a better lobe fit, and it becomes easier to test different geometries.
you really have done a great job making that. and you injecting water will work for sealing and cooling. inject water in the middle under the air end or at the female rotor side of the case at the start of the compression cycle. love to know if it works. thanks for the great vid.
I think they come off quieter because the peaks and valleys of the noise made aren't nearly as unsteady as a piston type, which have to accelerate and then decelerate over and over again. Having the power go out in the middle of the day while using air tools really gives an idea of how much higher the noise floor is with these running.
Your print and fitment issues come for lack in adjustments on slicer settings. adjust the horizontal expansion setting in your slicer... negative values if holes or too tight things fit too tightly, positive values if they are too loose... insure your printer e-steps are properly calibrated. Both can cause too much or too little flow and make the overall print different than you design. I run into this problem with different types of filaments as well. The more you print the more you learn.
It's definitely a learning process, I need to place more with the slicer settings. I had a terrible time getting the shape to be perfectly concentric. I have very different printer setup now that may do a bit better.
I'm not sure on the cause. I know that most small dry compressors don't usually run timing gears. I know the twin-screw superchargers used on things like the Hellcat have muffler built into the supercharger otherwise they'd be quite loud.
I’d still call it a win irregardless, especially when the gears were not fitted. You are entering new ground that I wouldn’t have considered and have a complete unit running. Not many of us would have tried.
Some materials and print settings have a parameter called "Shrinkage or Expansion factor" which potentially explains your meshing problem. This information is not available outside academic settings and precision engineering houses that test materials themselves, so shrinking a part was a good move.
Thanks. I need to play with the shrinkage settings in Cura more and see if I can get the parts to turn out more accurately. I wish there was more information out there on the manufacturing and design of these.
@@IndeterminateDesign You might also have to increase the stiffness of your printer. If you have a direct drive printer (I think you do, because you print PETG), then you could consider switching to a bowden tube, and creating gussets to stiffen the gantry of the printer. This could improve your tolerances enough to get a solid print. That said, I wonder how much the parts are expanding as the helix rotates from centrifugal forces. We might be dealing with factors beyond just the actual printing tolerance of the printer, when you get interference on your gears.
Yeah, some of that is so hard to measure with these shapes. I didn't talk about it in the videos, but these screws are basically a type of cycloidal gear, so they have a lot of sliding action which the smallest errors in the shape can cause intermittent issues, and actually push the air the wrong direction. The biggest lesson I now know for version 2 is to print very slowly. I seem to get much more accuracy when I do this.
I used to sell drilling rig equipment and 700hp+ screw compressor were common, they used a huge amount of oil and the receivers had oil separation in them, i don't know the grade, but i suspect it was 10w40.
Hi wonderful work. Quick question... you said you noticed play in the 608 bearings and basically fixed it with tape? Is there a "zero play" bearing or am I asking about something that doesn't exist or is the nature of this type of bearing always going to have some play in it. I'm learning so much from this and am glad that you got technical but not mind boggling with the explanation of the build. That really matters to some of us!
Thanks! The 608 bearings do vary quite a bit in quality and tolerances, but in this particular case the threaded rod I used for the shaft was slightly undersized. If I did it again, I would use an 8mm precision rod which is fairly cheap on Amazon and these should fit much tighter. Being a first time prototype I just tried to make it work with the threaded rod I already had.
What RPM are you running this at? I think your design is sound but with the tolerances of FDM, you can expect your blowhole (rotor tip leak) to be quite larger than a machined compressor. Efficiency drops significantly with more tip leakage and higher rpms will improve output. Generally screws run at about 9-13k RPMs IIRC. I have a screw compressor design/performance textbook and maybe can offer some help if you ever revisit this project again.
I was peaking around 7k rpm. So it sounds like I really need to spin this thing faster. I think it would definitely go smaller for my next design and a full gear driven drivetrain. Like you said the tolerances are what make this so difficult, particularly at this size.
Hi There! After finding your videos from a post on r/F1Technical, I have binge watched every video on your channel. I am going in to my first year at the Ohio State University for mechanical engineering, hoping to do something automotive for my career. I have a decent understanding of Autodesk inventor, the lower CAD software they have. I was just wondering what it is that you went to school for, what your job is, and how are you so good at designing this stuff?!? Thank you so much for the amazing content. I would love to be this good some day!!
Thanks! That's great that you already have some hands on experience with CAD software. I encourage you to get exposure to as many engineering and non-engineering disciplines as possible. In school I did a few years of engineering but I switched to a business degree, and ultimately ended up managing tech organizations. I'm a firm believer that having a broad background and good communication skills will afford you all kinds of career opportunities. I think this is great time to be in school, a revolution is coming with manufacturing and AI/ML. Best of luck at Ohio State! I've actually been reading a lot on the Buckeye Bullet for a potential future project. Definitely get involved in with something like that or FSAE.
Buddy, if you get one of these compressors able to lift 70 psi, how much would you charge for one? Let's says it's entirely printed in PTE with the needed tolerances.
That's an interesting question, I'm not sure at this point how much one would cost. Unfortunately, since this design is a dry screw compressor it will not be able to achieve 70psi. Professionally built industrial screw compressors like this only achieve around 30-40psi. Definitely something I may look into later, but it will require a two stage screw compressor.
That's good to know. I assumed differently after I saw all this sales literature about how quiet they were. Goes to show that you shouldn't trust sales.
Well this design wasn’t very efficient, but with regards to your question is this most won’t decrease the amount of air consumed. The engine would spend more energy spinning this pump than it would recover by pumping air back into the system.
Not good to use 1 timing belt would recommend 2 one that connects 1 motor to the other one just a strait connection and one where it goes 1 motor to the compressor. with how you got it set up it makes slag between the motors and ain't that good
I don't think I'm going to be able to fit all of that in to a video. If you check out my GitHub I have the cad files and profile for the rotors available. github.com/indeterminatedesign/ScrewCompressor There is a significant amount of math and a custom program I had to create to generate the rotor profiles using envelopes. If you want to make a different form of rotor I recommend downloading this paper. docs.lib.purdue.edu/icec/1099/.
