Nerd Alert
- Thread starter Bart_
- Start date
Replacement ptc thermistor worked, Belfuse brand 750 mA Ih with about 25% bigger body. Neat thing is its a dc or ac resistor, no PN junctions doping semiconducting it just a polymer that expends as it resistively heats up separating conductive particles until the increased resistance effectively shuts off the power - cools off resets go again. An MOV in your spike protected power bar however may survive as it conducts in the face of a voltage spike across it or it may burn - it drops its resistance as terminal voltage increases. I hotrodded a power bar 30 years ago by putting 3 or 4 MOVs in parallel to be able to handle a worse spike. Guess it worked, it never died.
Sean, you need to get that knot info to Knotorious.
Proof that Princess Leia time travelled
Sean, you need to get that knot info to Knotorious.
Proof that Princess Leia time travelled
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Reach
Been here much more than a while
- Location
- Atglen, PA
Now that paragraph takes me back to my college days! I haven’t thought about electrical components like those in a long time.Replacement ptc thermistor worked, Belfuse brand 750 mA Ih with about 25% bigger body. Neat thing is its a dc or ac resistor, no PN junctions doping semiconducting it just a polymer that expends as it resistively heats up separating conductive particles until the increased resistance effectively shuts off the power - cools off resets go again. An MOV in your spike protected power bar however may survive as it conducts in the face of a voltage spike across it or it may burn - it drops its resistance as terminal voltage increases. I hotrodded a power bar 30 years ago by putting 3 or 4 MOVs in parallel to be able to handle a worse spike. Guess it worked, it never died.
Sean, you need to get that knot info to Knotorious.
Branch Union TIP Rope Sawing During Climb - SRT
This popped up in another post so I thought I'd take a crack at it here. A lot of the data and analysis comes from the SRT Base Tied Tp Forces thread linked below.
The branch TIP union is a 180 degree wrap bollard with a tension ratio of 1.4 for a typical climb rope on average roughness bark. That means that the rope will slide over the union as you settle your weight onto the up rope leg until the tension rises in the down rope leg, maybe I'll rename that basal leg, to 1/1.4 x the up leg tension. So a 100 lb guy settles out : (1.0+1.4)x? = 100lbs, ? = 41.6 lbs giving 41.6 lbs in the basal leg and 58.4 lbs in the up leg. Oops. that's the DRT calculation! SRT: basal leg = 1/1.4 x 100 lbs = 71.4 lbs and climber up leg = 100 lbs.
If the climber's "weight" is incremented upwards both tensions rise maintaining the 1.4 ratio. The 1.4 value comes directly from at the point of bollard slippage so an initial climber weight increase will cause a small slippage or rope saw. Such an increase can come from initiating climber movement like pulling/stepping on an ascender. IIRC in my test data such an increase was 10% or 20% of the climber's weight or expressed in a ratio 1.1 or 1.2 G's. This is the source of bounce while ascending. Numbers can be 78.6 lbs, 110 lbs or maybe 85.7 lbs 120 lbs. After the slippage the basal rope side will stay at the higher tension value until the climber side drops to 1.4x less or 78.6/1.4= 56.1 lbs or 85.7/1.4 = 61.2 lbs as above example numbers. A principle of the tension ratio is that it matches the direction of motion of your rope through a device, pulley or other. There's a high side, loss and then lower tension side. This creates a hysteresis window that often confounds practical experiment measurements.
Now this is where it gets interesting. Descent. At first you apply hand pressure to your hitch/device which in itself doesn't change the up rope tension by the amount of hand force because while doing so you equally decreased the load on your bridge. But, it causes some reduction of grip of your hitch/device and it no longer supplies 1 climber G of support, so perhaps 90% or .9 G is still grabbing and the other 10% or .1G starts accelerating you toward mother earth. Now the up leg is at 90% of it's previous 100 lb load or 90 lbs so does the rope reverse the saw direction? In the case of descending after gentle settling to 71.4 lbs basal the bollard (union) won't slip until the climber side is below 71.4 lbs/1.4 = 51 lbs and 90 lbs is higher, so no slip. If you bounced/ascended and kicked the basal side up the 90 lbs doesn't make it down to/lower than 56.1 lbs or 61.2 lbs. so no slip. I could see that if you completely unweighted your SRT climb line and resettled onto it you could reasonably create a full reverse saw stroke. For completeness, at the stopping point of your descent you G spike the rope but my data was typical 10 or 20% only so that's the same calculation as for ascent.
So it seems that on initial settle onto the rope you get one forward saw stroke, any incremental climber G spikes create a little bit extra forward stroke, but in normal climbing negative G spikes are never large enough to reverse the bollard skid direction ie do the reverse rope sawing stroke. Maybe spring sap lubricated cambium has a tension ratio of 1.1 or 1.2 but then you've defeated all purpose of reasonableness if you're in that situation. The interested student could work the numbers.
The G spike values were from RW and ascender development I did that hasn't been published. Yeah aggressive climbing can increase the G spikes to some degree but I think you have to be pretty wild to create a significant effect from them.
link to related data and analysis thread: Seems like the right place to reference it - nerd content
I found during my testing a real non-linear initial settling of the rope length vs tension or "linear" %elasticity modulus, as the rope "cabled up" so it remains for the interested student to enlighten the details of this zero to low hundreds of lbs rope behaviour. I think it's severe enough to not even bother to try to calculate sawing motion size via use of a linear rope elasticity model.
This popped up in another post so I thought I'd take a crack at it here. A lot of the data and analysis comes from the SRT Base Tied Tp Forces thread linked below.
The branch TIP union is a 180 degree wrap bollard with a tension ratio of 1.4 for a typical climb rope on average roughness bark. That means that the rope will slide over the union as you settle your weight onto the up rope leg until the tension rises in the down rope leg, maybe I'll rename that basal leg, to 1/1.4 x the up leg tension. So a 100 lb guy settles out : (1.0+1.4)x? = 100lbs, ? = 41.6 lbs giving 41.6 lbs in the basal leg and 58.4 lbs in the up leg. Oops. that's the DRT calculation! SRT: basal leg = 1/1.4 x 100 lbs = 71.4 lbs and climber up leg = 100 lbs.
If the climber's "weight" is incremented upwards both tensions rise maintaining the 1.4 ratio. The 1.4 value comes directly from at the point of bollard slippage so an initial climber weight increase will cause a small slippage or rope saw. Such an increase can come from initiating climber movement like pulling/stepping on an ascender. IIRC in my test data such an increase was 10% or 20% of the climber's weight or expressed in a ratio 1.1 or 1.2 G's. This is the source of bounce while ascending. Numbers can be 78.6 lbs, 110 lbs or maybe 85.7 lbs 120 lbs. After the slippage the basal rope side will stay at the higher tension value until the climber side drops to 1.4x less or 78.6/1.4= 56.1 lbs or 85.7/1.4 = 61.2 lbs as above example numbers. A principle of the tension ratio is that it matches the direction of motion of your rope through a device, pulley or other. There's a high side, loss and then lower tension side. This creates a hysteresis window that often confounds practical experiment measurements.
Now this is where it gets interesting. Descent. At first you apply hand pressure to your hitch/device which in itself doesn't change the up rope tension by the amount of hand force because while doing so you equally decreased the load on your bridge. But, it causes some reduction of grip of your hitch/device and it no longer supplies 1 climber G of support, so perhaps 90% or .9 G is still grabbing and the other 10% or .1G starts accelerating you toward mother earth. Now the up leg is at 90% of it's previous 100 lb load or 90 lbs so does the rope reverse the saw direction? In the case of descending after gentle settling to 71.4 lbs basal the bollard (union) won't slip until the climber side is below 71.4 lbs/1.4 = 51 lbs and 90 lbs is higher, so no slip. If you bounced/ascended and kicked the basal side up the 90 lbs doesn't make it down to/lower than 56.1 lbs or 61.2 lbs. so no slip. I could see that if you completely unweighted your SRT climb line and resettled onto it you could reasonably create a full reverse saw stroke. For completeness, at the stopping point of your descent you G spike the rope but my data was typical 10 or 20% only so that's the same calculation as for ascent.
So it seems that on initial settle onto the rope you get one forward saw stroke, any incremental climber G spikes create a little bit extra forward stroke, but in normal climbing negative G spikes are never large enough to reverse the bollard skid direction ie do the reverse rope sawing stroke. Maybe spring sap lubricated cambium has a tension ratio of 1.1 or 1.2 but then you've defeated all purpose of reasonableness if you're in that situation. The interested student could work the numbers.
The G spike values were from RW and ascender development I did that hasn't been published. Yeah aggressive climbing can increase the G spikes to some degree but I think you have to be pretty wild to create a significant effect from them.
link to related data and analysis thread: Seems like the right place to reference it - nerd content
I found during my testing a real non-linear initial settling of the rope length vs tension or "linear" %elasticity modulus, as the rope "cabled up" so it remains for the interested student to enlighten the details of this zero to low hundreds of lbs rope behaviour. I think it's severe enough to not even bother to try to calculate sawing motion size via use of a linear rope elasticity model.
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Muggs
Been here much more than a while
- Location
- Canuckistan
Lignin welding, wooden nails, cool
Insert/Woodstove Burning
Noticed something the other day. We went through a dose of -10 to -15C weather and the insert was running nice, burning well and clean, maybe a bit quick. Then in about ten hrs it suddenly warmed up to -2C and the stove, on the same wood, slowed down, threw less heat and was lethargic burning the coals to ash. I recently found a 0.05" to 0.08" water column draft change reported in EPA test runs between lo and high burn rates, presumably due to higher flue gas temps. So we know flue gas temp self feeds back draft increase. But, the amount of degrees flue gas change is maybe even 200deg whereas the outside delta temp was only 10 deg. Both with significant effect. Bit of a head scratcher. To corroborate, my controller was running much higher air settings trying to maintain flue temp so it wasn't just observed "by eye".
My control is copied, with logic and proportional in between: flue at Low setpoint give 100% air, flue at High setpoint give 0%air - 0% air on the lever of a modern EPA emissions stove is actually not zero, it's an experimentally proven still-clean-burn lower setting, to avoid creosote fires!! Anyway, that forms a feedback gain delta air per delta temp. This gain was never evaluated re control theory, it just fell out of simple reasoning dictated by the end temp limits but it certainly could be made higher (and add in saturation clipping - you can't get more than 100% air!). Point being, on a sluggish day and perhaps only a few pieces of chunky firewood the fire struggled. In contrast, normally the gain seems just about right with medium firewood chunks and the kicker was I saw the stove oscillate on start up in the real cold when I had moderate kindling and a few more than usual nice dry medium small firewood chunks. The fuel caught, flue temp went right up to High limit, even overshot a bit, air turned to zero, flue temp dropped below High limit, air opened up a bit, overshot again about 5 cycles total. Then it cruised at 0% air cmd for quite a while. So I guess the point of the story is that besides outside temp and self feedback flue temp draft increase, geometry/dryness/fineness/quantity of fuel also forms part of the gain of how hot your stove runs.
Heck of a convoluted way to learn something you probably already knew.
Noticed something the other day. We went through a dose of -10 to -15C weather and the insert was running nice, burning well and clean, maybe a bit quick. Then in about ten hrs it suddenly warmed up to -2C and the stove, on the same wood, slowed down, threw less heat and was lethargic burning the coals to ash. I recently found a 0.05" to 0.08" water column draft change reported in EPA test runs between lo and high burn rates, presumably due to higher flue gas temps. So we know flue gas temp self feeds back draft increase. But, the amount of degrees flue gas change is maybe even 200deg whereas the outside delta temp was only 10 deg. Both with significant effect. Bit of a head scratcher. To corroborate, my controller was running much higher air settings trying to maintain flue temp so it wasn't just observed "by eye".
My control is copied, with logic and proportional in between: flue at Low setpoint give 100% air, flue at High setpoint give 0%air - 0% air on the lever of a modern EPA emissions stove is actually not zero, it's an experimentally proven still-clean-burn lower setting, to avoid creosote fires!! Anyway, that forms a feedback gain delta air per delta temp. This gain was never evaluated re control theory, it just fell out of simple reasoning dictated by the end temp limits but it certainly could be made higher (and add in saturation clipping - you can't get more than 100% air!). Point being, on a sluggish day and perhaps only a few pieces of chunky firewood the fire struggled. In contrast, normally the gain seems just about right with medium firewood chunks and the kicker was I saw the stove oscillate on start up in the real cold when I had moderate kindling and a few more than usual nice dry medium small firewood chunks. The fuel caught, flue temp went right up to High limit, even overshot a bit, air turned to zero, flue temp dropped below High limit, air opened up a bit, overshot again about 5 cycles total. Then it cruised at 0% air cmd for quite a while. So I guess the point of the story is that besides outside temp and self feedback flue temp draft increase, geometry/dryness/fineness/quantity of fuel also forms part of the gain of how hot your stove runs.
Heck of a convoluted way to learn something you probably already knew.
Muggs a deeper dive into wood products prompted by your post. Good stuff but chemistry makes my head hurt.
bioresources.cnr.ncsu.edu
It's what you call a review or summary type paper. Thank jeebus for those guys doing all the reading of all the original work papers and making the summary.
edit - One pill makes you larger, and one pill makes you small...
Fungal in my celium?! Well I think you've got fungal in your celium!
Adhesiveless bonding of wood – A review with a focus on wood welding :: BioResources
It's what you call a review or summary type paper. Thank jeebus for those guys doing all the reading of all the original work papers and making the summary.
edit - One pill makes you larger, and one pill makes you small...
Fungal in my celium?! Well I think you've got fungal in your celium!
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Woodstove Control
I've had two more incidents of bouncing off of and plain exceeding flue temp with 0% air command. One was more smaller (2 to 3" dia.) pieces involved and the other was being too generous with dried bark kindling when I though the regular pieces were on the wet side. Conversely I had once or twice wetter pieces sit there like a lump even near 80% air on good coals - which lead to the overkindling. I find that a partial load - trench the coals center front to back for below door air jet to go into, one half split as a bridge and two half or so splits perched 45 deg on top of the bridge leaves a good portion of the coal bed exposed to burn down att the same time as the new load burns mostly in free air exposure. 3 or 4 mid chunky splits (dry) run medium to hot, starting say 60% air to ignite, throttling maybe even to 0% during peak burn and then slowly increasing the air again as the fire converts to coals. So it seems rather than controlling the fire, the controller is helping manage air in response to the natural burn cycle. The wood load easily overpowers the intake air adjustment effect.
The main benefits seem to be catching overfire automatically and keeping the later coal bed hot, but I still have to be smart about each time I load wood into the stove.
I've had two more incidents of bouncing off of and plain exceeding flue temp with 0% air command. One was more smaller (2 to 3" dia.) pieces involved and the other was being too generous with dried bark kindling when I though the regular pieces were on the wet side. Conversely I had once or twice wetter pieces sit there like a lump even near 80% air on good coals - which lead to the overkindling. I find that a partial load - trench the coals center front to back for below door air jet to go into, one half split as a bridge and two half or so splits perched 45 deg on top of the bridge leaves a good portion of the coal bed exposed to burn down att the same time as the new load burns mostly in free air exposure. 3 or 4 mid chunky splits (dry) run medium to hot, starting say 60% air to ignite, throttling maybe even to 0% during peak burn and then slowly increasing the air again as the fire converts to coals. So it seems rather than controlling the fire, the controller is helping manage air in response to the natural burn cycle. The wood load easily overpowers the intake air adjustment effect.
The main benefits seem to be catching overfire automatically and keeping the later coal bed hot, but I still have to be smart about each time I load wood into the stove.
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Wood Moisture Meter Calibration
My buddy just got a midwinter load of firewood and it was not dry - who would sell a clearly use-it-now load of wet wood in good conscience? But that's another story. My buddy doesn't have a wood moisture meter but he does have a multimeter. Wood %moisture content is just mapped resistivity. Without double checking IIRC resistance reading of a surface, sheet or thick sheet is "per square" and thus it doesn't matter what your probe spacing is. IIRC the resistance value vs %moisture content calibration changes a bit with wood species, but for rock'n'roll a generic table is often used.
I have a cheap meter which gave the values of interest 15% and 20% - 5.0 Mohms = 20.5%, 10.0 Mohms = 19%, 20 Mohms (two 10M in series) went noisy 12%to 16% and thus is in question. 1Mohm showed 23%. Target firewood is 15 to 20%.
Would anyone with a wood moisture meter be able to try those resistor values across the probing pins and see if they get the same % readings? By the way, you can't hold the resistor to the pins with your fingers because your body has similar resistance as the wood would and would ruin the measurement. However, if you don't have gator clip wires it is acceptable to squeeze one end/lead of the resistor to one probe pin with index/thunb but just pivot the other lead end of the resistor to the other probe pin without touching it - then no circuit is formed across your body.
The objective here is that you can clip your multimeter across two pins and know %moisture without buying a separate meter. Also, instructions were pins separated across the grain, not with the grain. Also to test your firewood, warm it to room temp, then fresh split it and test on the split face.
edit - Have you heard of the Kiki bird up here in Canada? It goes " Kee kee kee Christ it's cold up here!". weather commentary
edit - search turned up USFS paper - so much for rock'n'roll approximation
My buddy just got a midwinter load of firewood and it was not dry - who would sell a clearly use-it-now load of wet wood in good conscience? But that's another story. My buddy doesn't have a wood moisture meter but he does have a multimeter. Wood %moisture content is just mapped resistivity. Without double checking IIRC resistance reading of a surface, sheet or thick sheet is "per square" and thus it doesn't matter what your probe spacing is. IIRC the resistance value vs %moisture content calibration changes a bit with wood species, but for rock'n'roll a generic table is often used.
I have a cheap meter which gave the values of interest 15% and 20% - 5.0 Mohms = 20.5%, 10.0 Mohms = 19%, 20 Mohms (two 10M in series) went noisy 12%to 16% and thus is in question. 1Mohm showed 23%. Target firewood is 15 to 20%.
Would anyone with a wood moisture meter be able to try those resistor values across the probing pins and see if they get the same % readings? By the way, you can't hold the resistor to the pins with your fingers because your body has similar resistance as the wood would
and would ruin the measurement. However, if you don't have gator clip wires it is acceptable to squeeze one end/lead of the resistor to one probe pin with index/thunb but just pivot the other lead end of the resistor to the other probe pin without touching it - then no circuit is formed across your body.The objective here is that you can clip your multimeter across two pins and know %moisture without buying a separate meter. Also, instructions were pins separated across the grain, not with the grain. Also to test your firewood, warm it to room temp, then fresh split it and test on the split face.
edit - Have you heard of the Kiki bird up here in Canada? It goes " Kee kee kee Christ it's cold up here!". weather commentary
edit - search turned up USFS paper - so much for rock'n'roll approximation
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Can we talk about Municipal projects and the WILD world of bidding them?
- Started by cooperMI4681A
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