Labor savin' devices

You probably have the same edition as mine, the 7th. I took Steel Structures around 1973.
Reply to
Ned Simmons
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It's been a long time since I've designed any lifting gear for others (and when I did I had a structural PE review the designs), but my recollection is that the codes require the "jerkiness" of the load be considered when choosing a factor of safety. When it's not yourself, there's not much you can do much about the jerkiness of the operator. Ned Simmons
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If I measure the maximum deflection by having a wire on the beam scratch a fixed smoked surface could I relate it to extreme fiber stress with an online calculator that shows both? Or am I missing something?
Reply to
Jim Wilkins
The short answer is, yes, that'll work for small deflections of straight beams. The only time I can remember actually comparing calculated vs. actual strain (strain = stress/modulus of elasticity) was in a Strength of Materials lab. I have had a chance to compare the actual and calculated deflection of simple well characterized beams a couple times, and the agreement was quite close. But the devil is in the details. Deviation of the supports, beam section dimensions, and loading details from the assumed ideals may introduce significant errors.
You could brew up your own brittle strain indicating coating.
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Reply to
Ned Simmons
...............
The short answer is, yes, that'll work for small deflections of straight beams. The only time I can remember actually comparing calculated vs. actual strain (strain = stress/modulus of elasticity) was in a Strength of Materials lab. I have had a chance to compare the actual and calculated deflection of simple well characterized beams a couple times, and the agreement was quite close. But the devil is in the details. Deviation of the supports, beam section dimensions, and loading details from the assumed ideals may introduce significant errors.
You could brew up your own brittle strain indicating coating.
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Reply to
Jim Wilkins
<snip>
Most common knots weaken the strength of the "rope". If you do some research in better knot tying books you can find some that maintain more of the ropes strength ;-)
Reply to
Leon Fisk
<snip>
Most common knots weaken the strength of the "rope". If you do some research in better knot tying books you can find some that maintain more of the ropes strength ;-)
Reply to
Jim Wilkins
<snip>
Most common knots weaken the strength of the "rope". If you do some research in better knot tying books you can find some that maintain more of the ropes strength ;-)
Leon Fisk Grand Rapids MI
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When working with a crew if I spend more than 5 seconds tying a knot they start joking about my "fancy French knots", so I keep them quick and simple or else call them by their European names, like "noeud de chaise." I've had helpers become very offended when they saw me tying knots they didn't know.
Reply to
Jim Wilkins
<snip>
Saw your other response too... Figured you knew what you were doing and had researched it for best practices ;-)
I can imagine there was considerable slack time during long ocean voyages. Industrious sailors would practice, observe and develop new knots to try out and amuse each other.
The Ashley Book of Knots has a lot of info and amusing anecdotes to peruse...
Reply to
Leon Fisk
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Saw your other response too... Figured you knew what you were doing and had researched it for best practices ;-)
I can imagine there was considerable slack time during long ocean voyages. Industrious sailors would practice, observe and develop new knots to try out and amuse each other.
The Ashley Book of Knots has a lot of info and amusing anecdotes to peruse...
Leon Fisk Grand Rapids MI
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When I was young, adventuresome and less injured I hiked all over the mountains here and learned what I could of rock and ice technical climbing equipment, and that I'm not agile or daring enough to try them. Surprisingly riding in Army helicopters didn't trigger my usual fear of height, even when a pilot demonstrated a hot LZ approach by suddenly rolling 90 degrees sideways and spiraling down in free fall.
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I climbed Mt Washington on an October day that was too cold, wet and miserable to drive up, though hundreds hiked it.
Reply to
Jim Wilkins
I hiked to the top of Mt. Washington on a July day like that. We camped a mile or two below Lakes of the Clouds and sprinted to the summit with daypacks on a gorgeous day. While sitting in the snack bar the clouds rolled in and next thing we were in a whiteout worrying about getting back to our camp in a blizzard with no gear. Or worse, spending the night in the "Dungeon" at Lakes of the Clouds hut.
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About 15 minutes later the snow stopped, the sky cleared, and it was a beautiful summer day again.
Reply to
Ned Simmons
W-folding step ladder?
Yup, whatever works.
Handy link.
Reply to
Larry Jaques
Presumably one of those that has 3 hinge joints. Each joint latches at several different angles in a 180-degree range. The center hinge faces "up" and the other two "down" (or vice versa) allowing a V fold (like usual stepladder) or a W fold or like an L (useful for under an eave) or like a C (sawhorse) >>across the rungs at beam height, then balance the two channels on the boards >>and attach the supports to the ends. Once the beam is suspended I remove >>the boards and lift the ladder over the beam. Disassembly is the reverse. [snip]
Reply to
James Waldby
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Presumably one of those that has 3 hinge joints. Each joint latches at several different angles in a 180-degree range. The center hinge faces "up" and the other two "down" (or vice versa) allowing a V fold (like usual stepladder) or a W fold or like an L (useful for under an eave) or like a C (sawhorse)
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Right. Unlike a regular stepladder they have no cross brace and can be lifted over the beam.
I always wonder how much should be explained for the muggles so I keep descriptions brief and watch for the questions. I'm of the engineer/scientist sort who communicates best through sketches.
Reply to
Jim Wilkins
O.K. That is related to the Anderson PowerPole connectors I just suggested. And the extra benefit of these is that they come with captive covers to keep dirt out of the connector wipers.
Good Luck, DoN.
Reply to
DoN. Nichols
O.K. That is related to the Anderson PowerPole connectors I just suggested. And the extra benefit of these is that they come with captive covers to keep dirt out of the connector wipers.
Good Luck, DoN.
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The assembly and disassembly tool for them is a small flat-blade screwdriver. Use it to push the contact pin in until it snaps over the spring, or to pry the spring out of the step. If you don't seat the pin over the spring it may back out when connected.
Reply to
Jim Wilkins
Yes -- the smaller (15/30/45 Amp) ones have a tool (which comes with the crimper) which is a half-cylinder to be used for pushing the terminals crimped on wire into the connector until the spring catches, and it has a pair of ears on the end which are used to hook onto the terminal and rotate to press the spring down to release the contact.
Larger ones (or at least semi-clones) have the halves of the housing held together with a couple of through screws, so you can then just lift the crimped wires and terminals out or place them in. These were ones which I picked up at hamfests, with the idea of using them for making external battery boxes for the smaller Best Power Systems UPS which I also have. Those came with cables pre-crimped, so no need to find a big enough crimper.
Enjoy, DoN.
Reply to
DoN. Nichols
Yes -- the smaller (15/30/45 Amp) ones have a tool (which comes with the crimper) which is a half-cylinder to be used for pushing the terminals crimped on wire into the connector until the spring catches, and it has a pair of ears on the end which are used to hook onto the terminal and rotate to press the spring down to release the contact.
Larger ones (or at least semi-clones) have the halves of the housing held together with a couple of through screws, so you can then just lift the crimped wires and terminals out or place them in. These were ones which I picked up at hamfests, with the idea of using them for making external battery boxes for the smaller Best Power Systems UPS which I also have. Those came with cables pre-crimped, so no need to find a big enough crimper.
Enjoy, DoN. ================================= At a ham fest I bought a "Crimp Tool One Piece" for half the price that appear to be for Andersons, as they are labeled with the same size numbers and do make solid crimps that pass the pull test, though I have to pry the pin out of the slot after crimping it.
My larger Andersons were also surplus, with heavy cables attached, so I've never had to crimp a pin larger than 45A. They were crimped by dimpling with a rounded-end punch instead of a compression tool.
I followed the rule for a battery box on a boat, to fuse the lead within 7" of the battery terminal, which permits a molded in-line fuseholder just outside the cover. A fuse inside the box could ignite hydrogen.
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The thinner (cheaper) fused charging leads are separately connected to the battery terminals to provide a Kelvin connection (no IR voltage drop) for monitoring battery voltage during discharge, so I can estimate remaining run time.
Reply to
Jim Wilkins
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The "hold onto the pin" *feature* applies to the crimper which came with the Quicksilver crimp set too. :-)
It may have been a tool similar to the machined pin crimp tools for mil-std aircraft connectors. It has four pins which push into the barrel at 90 degree intervals, making a very good crimp connection. (And an adjustment point which determines how deep the pins go to fit different size pins.)
But I've not yet seen one large enough for those pins. :-)
Sounds good to me.
Kind of like a good lab style multimeter, which does four-wire resistance measurement -- if you select the right switch. I used this for recording the resistance values of a General Radio decade box, whose lowest resistance step was 1 Ohm per step. The multimeter also had an IEEE-488 interface, so I could record the resistance measurements on the computer. (Two pins to feed current through the resistance, and two pins to measure the voltage drop across the resistor.)
Enjoy, DoN.
Reply to
DoN. Nichols
[ ... ]
The "hold onto the pin" *feature* applies to the crimper which came with the Quicksilver crimp set too. :-) ============================================
The owner told me of the troubles he had getting the prototype dies machined to his satisfaction, while I was silently thinking he should have bought machine tools and perfected them himself, as I do.
You can machine the two halves of a hex crimp die with only a plain straight end mill and a 30/60 angle block. Cut the flat that's parallel to the split line to the correct depth and width, then nibble the angled flats to meet its ends by eye. There's exactly enough clearance on the raised side.
Reply to
Jim Wilkins
[ ... ]
It may have been a tool similar to the machined pin crimp tools for mil-std aircraft connectors. It has four pins which push into the barrel at 90 degree intervals, making a very good crimp connection. (And an adjustment point which determines how deep the pins go to fit different size pins.)
But I've not yet seen one large enough for those pins. :-)
--------------------- The crimper appears to have been a single guided punch, like the hammer crimping tool. ---------------------
Kind of like a good lab style multimeter, which does four-wire resistance measurement -- if you select the right switch. I used this for recording the resistance values of a General Radio decade box, whose lowest resistance step was 1 Ohm per step. The multimeter also had an IEEE-488 interface, so I could record the resistance measurements on the computer. (Two pins to feed current through the resistance, and two pins to measure the voltage drop across the resistor.)
Enjoy, DoN. ============================================================ The result is the resistance between the two connections closest to the resistor, regardless of whether they are force or sense.
You can use the four-wire method to accurately measure very small resistances with a current-limited power supply. I use a DPS5020 at 10A or 20A to measure milliOhms, such as antenna element contact resistance and solar panel wiring corrosion. Some wire I bought recently was right at the minus side of its size tolerance.
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A rectifier supply made from a 24V 250VA control transformer is enough to charge a 12V battery at 15A with the DPS5015. The supply I made from a 50A buzzbox welder charges to 24V at 20A. The DPS family isn't quite as nice as a Keysight/Agilent/HP E36xx but they cost ~$60 instead of ~$1600, and I can datalog their outputs with $40 PC-interfaced meters.
Reply to
Jim Wilkins

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