I Just Got a New Air Compressor

[BukitCase]

I would probably just go with 30w non-detergent (I keep some in a squirt can) - marvel is kinda thin, doubt it would help seal the rings much, even temporary.

Doesn't matter if you "contaminate" the compressor oil, it'll need replaced afterward no matter what you do... Steve

Oh, the "groovy" cylinder walls were on cylinder #1 of a 3 cyl. hercules gas engine in an old Oliver OC-46 (crawler with a 5/8 yd. bucket and rippers) a buddy talked me into buying (because HE wanted it but didn't have the money OR a place to play with it - I had both, and 3/4 mile of road to punch in on a curvy sidehill)

At first I was elated when I did the comp test and had 0, 60,60 wet or dry - figured I'd do valves and be back in biz. I just about puked when I got the head off and saw those grooves! Took the block downtown and had the local wiz sleeve and bore it to a new piston, I put rings/valves/bearings, etc, in it and away we go :cool2:

 

[ericher69]

This gets into the realm of mass-spring-mass calculations - ever seen a sign on a long suspension bridge that said "no dogs

In the case of the bridge/dog, typically a dog will go into a trot when it's going somewhere - it's a very constant series of "little jumps", so to speak. If that particular dog's weight and "frequency of thumps" happens to coincide with a harmonic of the bridge's natural resonance, it works just like pushing your kid on a swing - if you time the pushes right, he'll go higher and higher. In the case of the bridge, there have been cases of dogs destroying a bridge under the wrong circumstances.

Shorter answer - oh yeah, that was the FIRST sentence ...Steve

Steve;

I'm gonna need some proof of this...

The only thing that remotely refers to any animal (not at all involved with destruction) but named after an animal was the Tacoma Narrows bridge collapse of 1940. Workers nicknamed it "Galloping Gertie"

I am just a man than needs to see to believe

Thanks

 

[BukitCase]

ericher, thank you for questioning that bit of "lore" - which I SHOULD have done several years ago. It came from a man whom I've never met, but is a veritable encyclopedia of things acoustic. I had never known him to utter a word that wasn't verifiable (if you knew enough :confused2: ) so I had taken this "fact" as true without question.

Fortunately, the important stuff he taught me IS verifiable in the hundred$ in books I've accumulated on acoustics :confused2:

However, I just spent about 15 minutes looking for anything on this, and like you, I came up empty. Kind of surprised there's nothing on snopes.com about it.

Guess I'll just have to "un-learn" something today - again, thanks... Steve

 

[ericher69]

ericher, thank you for questioning that bit of "lore" - which I SHOULD have done several years ago. It came from a man whom I've never met, but is a veritable encyclopedia of things acoustic. I had never known him to utter a word that wasn't verifiable (if you knew enough :confused2: ) so I had taken this "fact" as true without question.

Fortunately, the important stuff he taught me IS verifiable in the hundred$ in books I've accumulated on acoustics :confused2:

However, I just spent about 15 minutes looking for anything on this, and like you, I came up empty. Kind of surprised there's nothing on snopes.com about it.

Guess I'll just have to "un-learn" something today - again, thanks... Steve

Steve;

Guilty of the same type of thing many times over!

This is why I now question things and try not to repeat to others until I know that it is fact.

Hope there are no hard feelings as my intent was not to mock or ridicule anybody!

 

[Jeembawb]

Hi guys - am reading this with interest. I thought I knew a fair bit about air compressors till I found this, and I do especially like the bit about the harmonic vibrations and the springiness of the rubber. It sort of explains why one of my compressors (which has one solid rubber foot and 2 solid rubber wheels) bounces sideways around the shed. It had a motor replaced once and may have gotten a wrong pulley ratio out of the deal or may have always had the harmonic imbalance, so based on this thread I will try it out with a different ratio. When I do I will try to determine the correct ratio to get max output (I like sandblasting) but a different note of determining "free air delivery" which has been spoken about up thread - there are a couple of ways to determine the rated or advertised outputs of compressors - and I can't just yet put my eyes on the info to explain better, but off the top of my head there is the theoretical output that doesn't take into account losses etc and the more accurate way was to test with certain parameters ( and I think there may be different sets of parameters that get used by manufacturers to advertise their output - a bit like the different ways of measuring horsepower (a horse should be a horse right??? Unless of course it's a donkey)) - I saw an article once by a local "reputable" manufacturer that said they used the true output method of rating and went to explain the difference - I will try to find it.

About the dogs on the bridge - if a whole lot of my blue cattle dogs started trotting across a bridge I would get worried (she's not gentle), but I don't reckon one dog would have enough mass (even whiskey - that's her name) to cause the harmonic resonance required to shake it to bits but I did see a documentary (prolly history channel or some such) that covered a lot of this bridge resonance stuff including wave and wind action. Probably where this has all derived is the "army marching in step" across a bridge I guess and the dog thing being the other end of the scale but probably still measurable (they were doing that on the doco measuring the frequency of something at the other end of the bridge and were watching the oscillations increase).

I know what you mean about verifiable info (or at least correct info) - nothing worse than people believing something they heard or read is correct and going about prattling as if its gospel when it's not - it could lead to mass ignorance :drool::drool::confused2::drool::drool

 

[Iplayfarmer]

Quick update:

I found a 8.5" pulley in a pile of auction leftovers and swapped it out for the 7.4" that I had on before. This took my volume up to 12 cfm. I wish I had remembered about that pulley before I spent $50 on the 7.4" pulley.

I think I'm done modifying for now. 12 cfm is plenty for most of my needs. I've had the compressor up and running for about a month now. It cycles smoothly. The tank holds air. I builds plenty of pressure. I consider this project a success. Now I can turn my attention on re-organizing the garage to accommodate all the stuff displaced by this behemoth.

 

[BukitCase]

Cool, I love it when a plan comes together (even better when things come together with no plan whatsoever :=)

Seriously, IMO a shop isn't a shop without adequate compressed air, and congrats on nearly stealing the beast... Steve