Glad to see some of the old-timers still hanging around...
The spacing is definitely part of the puzzle. I tried several variations of the velocity stack, with the bottom of the struts moved up in 1 mm increments. The further away you get, the better. The factory grill is mounted with a pair of washers, but they aren't very thick. Even with wire grills, I still use the washers.
Given that the wire grill with no disk in the middle is better than one with it, I wonder if the velocity stack would work better with no center as well? That would get rid of the strut noise entirely, and might not affect the airflow much.
I like having some sort of protective grill, especially on the extruder fan. I've had a couple close calls when changing filaments where the end of the filament has flapped around and gotten pretty close to the fan intake. I suspect stuffing a piece of filament into the blades would be the end of the fan. The wire grill doesn't provide as much protection as the factory one, but I just have to be more careful if I want to keep the increased airflow.
Quieter Fans
Re: Quieter Fans
When we lived on the boat (36 foot trawler) I built-up a computer from motherboard, 3U alminum server chassis, 12 volt input power supply, audigy sound card with panel controls, and a graphics card which could do TV. All of this was hung from the overhead next to the helm and provide TV from satellite on a 20 inch 6x9 monitor. It all worked great, but three 2 1.2 inch fans were incredibly loud, they screamed. The fans were mounted to an aluminum panel which had a pattern punched in it which was very close to what you would do if you wanted a siren. armed with my trusty circle saw, I cut out the pattern and because the fans were mounted inside the case didn't replace the "grilles" with anything because the fans were inaccessible to fingers when the systme was running.
I always wondered if the guys who designed this thing had ever put a machine together and powered it up.
I always wondered if the guys who designed this thing had ever put a machine together and powered it up.
Re: Quieter Fans
I worked at Hewlett Packard around 1980 designing test equipment. We had a really sharp industrial designed who had done an in depth study of fan noise. Nobody else seemed to pay much attention to fan noise back then. That was the first time I heard about the 'siren effect" from having struts or a grill on the intake side. He discovered that some vendors had the support struts on the intake side, and with no grill at all, they would make a lot more noise than if the struts were on the outlet side.
One fan could be bad enough, but in instruments with more than one fan, you could get beat note effects that would drive you nuts. He found vendors that could synchronize their fans, and that helped enormously.
I also scratch built a PC many years ago, and the case had provisions for a huge number of fans. I loaded it up and carefully avoided the siren-grill problem, but it was WAY too loud. I removed about half the fans, and put adhesive backed car audio dampening material on the panels to make it tolerable.
One fan could be bad enough, but in instruments with more than one fan, you could get beat note effects that would drive you nuts. He found vendors that could synchronize their fans, and that helped enormously.
I also scratch built a PC many years ago, and the case had provisions for a huge number of fans. I loaded it up and carefully avoided the siren-grill problem, but it was WAY too loud. I removed about half the fans, and put adhesive backed car audio dampening material on the panels to make it tolerable.
Re: Quieter Fans
There may never have been any techs that actually wanted the noise, but then I never worked in a lab.
On the subject of noise, sometime in the mid '50s Remington marketed a more or less silent typewriter. I think it was called the quiet-writer. I can remember seing one, IIRC the type was secured to metal arcs which were raised by the mechanism to whatever height was needed to index the desired letter and then pressed against the paper without any partiuclar impact.
And they really were quiet and the whole idea was a phenominal mistake.
Good typists loved the clatter, the more the merrier. It made them feel that their productivity could be appreciated.
Dad worked for a guy whose secretary won typing speed contests. She was faster than any of the machines then on the market '53-'55. When IBM was working on the golf-ball electric, they'd send the early models over for her to try with a techincian who would measure which sequence of letters were the quickest. Apparently querty was a layourt devised to prevent sequences which occurred most frequently from being easy enough to overspeed the machines du jour, but in 1955 she could do it on almost any combination.
In any case, IBM went to market with a version of the machine she couldn't beat. Or at least, that's how I heard it.
On the subject of noise, sometime in the mid '50s Remington marketed a more or less silent typewriter. I think it was called the quiet-writer. I can remember seing one, IIRC the type was secured to metal arcs which were raised by the mechanism to whatever height was needed to index the desired letter and then pressed against the paper without any partiuclar impact.
And they really were quiet and the whole idea was a phenominal mistake.
Good typists loved the clatter, the more the merrier. It made them feel that their productivity could be appreciated.
Dad worked for a guy whose secretary won typing speed contests. She was faster than any of the machines then on the market '53-'55. When IBM was working on the golf-ball electric, they'd send the early models over for her to try with a techincian who would measure which sequence of letters were the quickest. Apparently querty was a layourt devised to prevent sequences which occurred most frequently from being easy enough to overspeed the machines du jour, but in 1955 she could do it on almost any combination.
In any case, IBM went to market with a version of the machine she couldn't beat. Or at least, that's how I heard it.
Re: Quieter Fans
Ah, the good old days.
My Mom had a "Underwood Noiseless" mechanical typewriter. I think this was before "truth in advertising" became a thing... It was loud, black, & mostly cast iron. To get upper case, your pinky had to lift the entire carriage assembly, which took stronger fingers than I had when I was a kid.
In the Selectric testing I heard about, I think IBM was mostly focused on where to put the letters on the type ball. The goal was to put the most common letters (or the ones the typist could hit the quickest) all close on the ball so it didn't have to spin as far. They had a bit more time to deal with letters/symbols that were out at the corner of the keyboard.
My Mom had a "Underwood Noiseless" mechanical typewriter. I think this was before "truth in advertising" became a thing... It was loud, black, & mostly cast iron. To get upper case, your pinky had to lift the entire carriage assembly, which took stronger fingers than I had when I was a kid.
In the Selectric testing I heard about, I think IBM was mostly focused on where to put the letters on the type ball. The goal was to put the most common letters (or the ones the typist could hit the quickest) all close on the ball so it didn't have to spin as far. They had a bit more time to deal with letters/symbols that were out at the corner of the keyboard.