New KSCC "wire"

Re: New KSCC "wire"

Postby walterclark » Sat Jan 16, 2016 10:36 am

I keep coming back to the idea of having something, probably on wheels, with a sheave (pulley) that can be deployed behind the truck, that can act as some drag on the loop to help keep the wire from curling up. I think it probably needs to be remotely steerable so it can be kept on the road and help keep the loop on the road around corners - like those huge fire trucks with the rear driver to help them negotiate turns in a tight city.

On a related subject... I have been thru the wire. I removed all the kinks, repaired a couple damaged spots that werent noticed and taken care of on the hill, tested all the drops and moved the spliced-in bit that was done after the street sweeper tangled up in the wire at Okemo.

I had noticed something of a "glitch" in the wire above Okemo check 7 last year when testing it using a technique called Time Delay Reflectometry or TDR. TDR lets you observe the impedance all along a cable by observing on an oscilloscope how a step signal is reflected back to the scope from the cable under test. You can determine the location and level of any impedance aberrations using it. It is a technique I used often back when I supported mainframe computers the size of a city block and the hundreds of miles of cables and connectors involved in tying all the bits together. Anyway, I was able to narrow the glitch (several actually) down to the junctions between the flat molded twinlead wire (the wire we used from Start to just above OC7) and the twisted pair wire we use from there to Holding. It turns out that the 2 wires, despite being the same mil-spec have slightly different impedances and so I was seeing the electrical equivalent of a speed bump at each such splice. One of these was not so bad but the fact that we repaired the damage to the twisted pair wire from the street sweeper with about 100' of the molded twinlead and this spliced in bit was a few hundred feet up the wire from the original twinlead to twisted pair splice meant we had 3 almost back to back "speed bumps". The resultant glitch was quite ugly looking. I removed the 100' spliced in twinlead, brought the two twisted pair ends together, spliced them, then moved down to the original twinlead to twisted pair splice and spliced the 100' patch there. The result is one small bump in an otherwise clean looking cable, rather than a wild set of impedance oscillations. I didnt try to test or predict what the effect of the original configuration had on our 0-5000Hz communications, but it is safe to say it didnt help. I did a bandwidth test of the wire after this and it is 0db down at 1000Hz, -3db at 6000Hz and -6db at 10000Hz, end to end with no loads (headsets) applied. About as good as one could hope for with this wire.

While the wire was completely wound onto the spare reel, I partially dismantled the primary reel. Sherm had said some problems had occurred to the drum core that he fabricated on this reel and I should check it out. Indeed there problems. 3 of the 4 2x3 studs he drywall screwed onto the original core had torn loose from the core so the poly core the wire is wrapped onto was moving around. I made up 4 new studs (the old ones were about 1/4" shy of reaching across the span between the reel sides) because I wanted to anchor the new ones to the sides and not the old core because this put the fasteners in shear for all loads and anchored into the middle of the studs. I used .25 x 3.5 lag bolts and took the opportunity to true up the new core (the original core was not centered to the reel and there was some runout). I also balanced the reel. When winding the wire onto the spare reel I noticed the primary reel seemed very unbalanced and always wanted to swing to the heavy side down. Some of this was because the wire was not centered around the reels rotation centerline and some of it was just uneven weight around the reel - probably due to some random voids and large drilled holes in the wood sides. So now the reel is balanced and the wire is even around the reel rotational centerline. It seems to have a much lower tendency to rock back and forth. We will see how it behaves when all the wire is back on the reel.

Oh. I also bought and added a couple flange bearings to the spare reel so a standard 1" iron pipe can be used as a stationary axle and a couple jack stands provide a nice stable perch while wire is wound to or from the spare reel. Just feeding that iron pipe thru the original holes in the reel and setting the axle on jack stands meant I spent as much time re-positioning the reel and axle as actually moving wire to it, not to mention the added work needed to spin the reel.
The older I get the better I was.
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Re: New KSCC "wire"

Postby sdwarf36 » Sat Jan 16, 2016 2:03 pm

Thanks again for all your hard work Walter. I think that the inner core not moving around might help with some of our problems. The wire would tend to act loose as it was shucking + jiving around the moving core. As you can see, its a good thing I don't build race cars out of wood. :?
Translating road racing to hillclimbing:
Proper tire selection== nothing hooks up on moss or wet leaves.
Staying on the racing line==anything paved is considered good.
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Re: New KSCC "wire"

Postby KevinGale » Sat Jan 16, 2016 10:19 pm

Many thanks Walker. I've done wire work during the off season a couple times. Lots of work and it's for the most part a thankless job.
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