So what was the depth of the pool? I think I heard sometime that shallower pools make for slower times, which makes sense to me.
Happy 4th everyone!
In electronics when one has a circuit that has a tendency to ring” after a change in current (like motor controls etc) a common “fix” is to use a snubber circuit. These are often a diode and resistor in series across the resonant circuit which damps the ringing by placing the R across it for one polarity.
In a pool, having a trough like they describe would do a similar thing, wave energy that forces water over the edge is absorbed (and importantly, not reflected back into the pool).
Speaking of damping, back in Highschool where I met cyclecamper, I found that a triangular file could cut a nice notch into the down pipe on the schools urinal’s. When equipped with such a notch in the pipes, one could apply a “significant damping” to anyone who flushed the urinal after use. While incredibly funny at the time (and a large cut in the sit down toilet feed pipe was even more dramatic), one could also be suspended for such modification of the plumbing.
Actually my first engine that had unusual valve gear with this one. I was a Honda fan boi back then, had a CB160 in High school and bought a used CL450 a few years after graduating.
This had torsion springs instead of coil valve springs.
I had a friend that worked at a Chopper shop that specialized in British bikes and while I had no use for choppers (being a wannabe road racer) but did make good use of their junk pile and acetylene torch. The gas tank was from a BSA rocket three, seat from a CB750 café bike and front end from a 650 triumph.
Happy 4th!
Tom Danley
In electronics when one has a circuit that has a tendency to ring” after a change in current (like motor controls etc) a common “fix” is to use a snubber circuit. These are often a diode and resistor in series across the resonant circuit which damps the ringing by placing the R across it for one polarity.
In a pool, having a trough like they describe would do a similar thing, wave energy that forces water over the edge is absorbed (and importantly, not reflected back into the pool).
Speaking of damping, back in Highschool where I met cyclecamper, I found that a triangular file could cut a nice notch into the down pipe on the schools urinal’s. When equipped with such a notch in the pipes, one could apply a “significant damping” to anyone who flushed the urinal after use. While incredibly funny at the time (and a large cut in the sit down toilet feed pipe was even more dramatic), one could also be suspended for such modification of the plumbing.
Actually my first engine that had unusual valve gear with this one. I was a Honda fan boi back then, had a CB160 in High school and bought a used CL450 a few years after graduating.
This had torsion springs instead of coil valve springs.
I had a friend that worked at a Chopper shop that specialized in British bikes and while I had no use for choppers (being a wannabe road racer) but did make good use of their junk pile and acetylene torch. The gas tank was from a BSA rocket three, seat from a CB750 café bike and front end from a 650 triumph.
Happy 4th!
Tom Danley
Attachments
The OP mentioned that it was made out of steel. I assume that it will flex more easily than concrete ones. Depending on how the thing is stiffened it could show quite strange resonant behaviour IMHO.
Regards
Charles
Regards
Charles
Look Elsewhere
Some potential causes of a “slow” swimming pool:
1) Look at what is added to the pool water and its affect on surface tension (wetting agents).
2) Measure the condition of the air the swimmers are breathing in regards to Pressure, Temperature, Relative Humidity, and particularly, Oxygen content.
3) Calibrate the timers used that are indicating pool “slowness”.
4) Was the grouping of swimmers during the race spread-out or close together?
5) Is the pool length longer than advertized?
Some potential causes of a “slow” swimming pool:
1) Look at what is added to the pool water and its affect on surface tension (wetting agents).
2) Measure the condition of the air the swimmers are breathing in regards to Pressure, Temperature, Relative Humidity, and particularly, Oxygen content.
3) Calibrate the timers used that are indicating pool “slowness”.
4) Was the grouping of swimmers during the race spread-out or close together?
5) Is the pool length longer than advertized?
Yes, I would first suspect something environental more closely related to the biological processes than to waves. Exact characteristics of the water and air which are inhaled come to mind first. Chlorine and bromine water sterilization agents inhaled, ph, humidity, oxygen, CO2, ozone from mercury-vapor ozone-generator sterilizers inhaled, CO from heaters inhaled, bacteria & mold/fungus, particulate irritants, smog, pollution, whiteboard markers, ammonia, acids, etc. Things you might not suspect can have profound and immediate biological effects when inhaled.
Yes, car and motorcycle suspension people correct everyone on the difference between "damping" and "dampening" despite the same root "damp" ("to damp vs "is damp" or "to dampen")... I once saw a mean masculine black 'vette with plates "Wet Yet" but I suspect that was a different kind of dampening reference.
The 'Desmo' thing is interesting. Despite nearly doubled reciprocating mass there's no single part with increased stress (dual rockers for opener and closers, but each just as reliable and a single rocker) there's less frictional losses (motorcycles usually don't have roller followers, and springs themselves do not return 100% of the force, they get hot with internal frictional losses). I build TL1000s motors, the Japanese poor-man's Ducati. But my old Cagiva has a Desmo Ducati engine...
Tom, did you have something to do with car horns, small engines, or other noise sources in school lockers on the last day??? I think the statute of limitations has run out now...
The 'Desmo' thing is interesting. Despite nearly doubled reciprocating mass there's no single part with increased stress (dual rockers for opener and closers, but each just as reliable and a single rocker) there's less frictional losses (motorcycles usually don't have roller followers, and springs themselves do not return 100% of the force, they get hot with internal frictional losses). I build TL1000s motors, the Japanese poor-man's Ducati. But my old Cagiva has a Desmo Ducati engine...
Tom, did you have something to do with car horns, small engines, or other noise sources in school lockers on the last day??? I think the statute of limitations has run out now...
Okay, related to the slow pool topic: We took a ferry somewhere and you could see that dolphins were "surfing" on the wave off the stern of the ferry. That is, there was a pretty good wake which had a downslope that a dolphin could just ride on with little apparent exertion. A free ride.
Were the dolphins slowing down the ferry?
David
Were the dolphins slowing down the ferry?
David
I'm pretty clueless about pools, would have to think about this...
Making the waves slowed down the ferry and it didn't benefit at all?
Surface waves usually indicate the water below moving circularly. So the waves sometimes push you ahead and sometimes pull you back unless you can ride them downhill like a surfer or a surfing dolphin. If a swimmer makes a wave, does he eventually have potential benefit from its reflection? I dunno...does a pro swimmer float?
I used to have a big waterbed. Geeze (flashback) come to think of it, when Danley was first married he had the same waterbed; not the same model, but actually the same bed LOL. TMI. Too much information. Now he's sorry to have an old schoolmate on-list. Anyway, with an undamped bag 'relations' were nearly effortless...at one frequency. With a damped bag or mechanical wave absorber it was much more work LOL. I'd expect a wave absorber to have a penalty; the swimmer suffers the cost of making the wave but never benefits from it? The waterbed analogy could certainly be flawed logic...or the root of my mis-conception...or perhaps of the conception of my daughter...but I digress again.
Making the waves slowed down the ferry and it didn't benefit at all?
Surface waves usually indicate the water below moving circularly. So the waves sometimes push you ahead and sometimes pull you back unless you can ride them downhill like a surfer or a surfing dolphin. If a swimmer makes a wave, does he eventually have potential benefit from its reflection? I dunno...does a pro swimmer float?
I used to have a big waterbed. Geeze (flashback) come to think of it, when Danley was first married he had the same waterbed; not the same model, but actually the same bed LOL. TMI. Too much information. Now he's sorry to have an old schoolmate on-list. Anyway, with an undamped bag 'relations' were nearly effortless...at one frequency. With a damped bag or mechanical wave absorber it was much more work LOL. I'd expect a wave absorber to have a penalty; the swimmer suffers the cost of making the wave but never benefits from it? The waterbed analogy could certainly be flawed logic...or the root of my mis-conception...or perhaps of the conception of my daughter...but I digress again.
Tom mentioned using a diode and resistor to damp. Made me wonder...
First question: We know how a port doesn't flow symmetrically in both directions if just one end is flared or flush-mounted, and that makes the driver slowly pump in or out as it works. Could that be corrected for electrically with a diode and resistor? Seems to me even an imperfect model could effect adequate slow opposed correction to negate this.
Follow-on question: We employ mostly mechanical means to center the averaged position of the moving mechanism between its extremes; could we improve mechanical compliance if we used electronic centering means instead, with some slow feedback mechanism? Can't we do much better electrically than a springy spider? Suspensions seem so primitive...there's lots of discussion of better linear bearings, double spiders, various hinges, etc. but little discussion addressing the springy return to center. Is it worth pondering?
First question: We know how a port doesn't flow symmetrically in both directions if just one end is flared or flush-mounted, and that makes the driver slowly pump in or out as it works. Could that be corrected for electrically with a diode and resistor? Seems to me even an imperfect model could effect adequate slow opposed correction to negate this.
Follow-on question: We employ mostly mechanical means to center the averaged position of the moving mechanism between its extremes; could we improve mechanical compliance if we used electronic centering means instead, with some slow feedback mechanism? Can't we do much better electrically than a springy spider? Suspensions seem so primitive...there's lots of discussion of better linear bearings, double spiders, various hinges, etc. but little discussion addressing the springy return to center. Is it worth pondering?
I think it would have to be better than this. For example..
If a best case normally sprung valve uses soft enough springs that the valve's inertia overcomes the spring force at max RPM when it is depressed, then there should be twice the energy invested into the moving mass (and into the spring) than a desmo actuating cam would be required to throw to overcome the valve inertia alone. Then figuring in the mass of the spring itself, the retainer, (and the spring losses etc), the (desmo) actuating cam may be made much lighter.
The desmo return cam would have to 'catch' the valve and throw it back, but minus the retainer, so lighter than a standard cam.
Other 'pros' for the desmo cams being light is that the engine is normally operated where the valve inertia is less than required to overcome the spring force, and springs are typically made even more stiff than required to ensure correct operation.
Then again since this all probably comes down to materials science, it may be purely academic.
- Status
- Not open for further replies.