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Some videos of Real Cranes & one note about electrical meters.

This is just a short post to kind of clean up a few loose ends.  Besides, it is about time we had a “light” post.   (Tastes great… less filling… something like that.)

Electrical:

First,  I want to clear up something that was not said about the voltmeter.  Most newer style meters use an amplifier inside that makes the input impedance a high value.  Usually this is about 10 MΩ.  Before the days of everything being digital, there were actual analog (dial) meters that had the amplifier to raise the input impedance.  Being a nerd kid, one of the Christmas presents I requested was a HeathKit vacuum tube voltmeter.  That was state of the art in the late 60’s.

High input impedance is not always a desirable thing.  Sometimes wires and components have a charge on them even though they are disconnected.  (Explaining how this happens will take some effort and we are not there knowledge wise yet.)  A high impedance meter will display a voltage, were a low impedance meter will drain the charge and show a truthful 0 volts in this case.   I have been lead astray because of things like this.  Dial meters are sometimes better than digital meters because it will follow variations where the digital will tend to average things and display one value.

Ideally you would want each type, but most people opt for the digital meter because it is easier to read the value and works in most cases.   A medium priced digital is the meter I use.

Cranes:

I have been researching real cranes to get an idea of the kinds of forces to expect. By kinds of forces, I am talking in general terms, i.e. Compression, Tension, Bending, etc. It is looking as if most modern cranes are designed to operate with the boom primarily in compression.  I am still not done thinking this out.   The videos are of two draglines operating.   One is a very old one and the second one is a much newer Manitowoc crane. On the Manitowoc crane site you can actually load data sheets on their cranes.

One of the things that has allowed cranes to become so massive is the whole development of hydraulics.  The Manitowoc cranes have the hoist winding drum inside the base of the boom.  (They call it the boom butt.)   This puts this cable inside the boom and places the boom under internal compression.   The other cables also primarily pull in a direction to make compression on the boom structure.  On the old crane the whole mechanism was gears, brakes, and clutches, driven directly off the engine so they had less options on threading the cables on the machine.

Notice in the second video the structure behind the boom used to raise an lower the boom.  This gets the cables up higher to provide leverage  on the boom.   In general, I am not sure where we will go with popsicle sticks but compression is going to be a tough problem to deal with because of the thin section of the popsicle sticks.

 


I hope you enjoy watching these. I guess I never grew up out of playing in my sandbox with the toy trucks so I enjoyed these.  Although I really have no idea on how we are going to ‘git-er-done”…. I am looking forward to the challenge.

Gary


 

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