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3rd-rail shoe for Metro North - Long Island RR through running

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3rd-rail shoe for Metro North - Long Island RR through running
Posted by daveklepper on Saturday, May 28, 2022 2:56 PM

Comments?

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Posted by MidlandMike on Saturday, May 28, 2022 8:43 PM

What is the 3rd rail contact material?  Would the assembly fit under the LIRR 3rd rail safety cover?

I understand NH had shoes that were compatible with both types of 3rd rail.  How does theirs compare with yours.

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Posted by daveklepper on Sunday, May 29, 2022 2:04 AM

I'll need to do some  research to answer.  I had not thought about the possible problem of the shoe's thickness.  Dumb of me!

The NYNH&HY shoes you mention were only on FL-9s.  No other "motors." and  no Ms had them.

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Posted by Overmod on Sunday, May 29, 2022 8:17 AM

Three times my reply has been made to disappear by the evil elves.  Use a hinge at the 'wrist' and either servos or springs to float a thin shoe level with the contact patch; perimeter weighting stabilizing "flight" in underrunning contact.  For higher speed use predictive servo control like lightweight HSR pans.

In my design the replaceable contacts in the shoes are graphited and roughly triangular, alternately facing up and down in a symmetrical gridiron structure whose angled faces handle the peak current and transmit it to conductors 'going inboard' isolated from the sense logic and power to control the shoe.  If you angle them or run them longitudinally you could still preserve 'one size fits all' top and bottom...

By analogy with model railroad 'microarcing' you want to control the amount of plasma damage to the rail, particularly at points subject to arcing and progressive erosive damage.  I proposed back in the day to handle this with metal spraying rather than 'subtractive machining' analogue of rail grinding -- you'd have to make the covers removable to get the stones to bear for overrunning, and design different wheels to get in for underrunning, but I presume they have current (no pun intended) equipment and procedures to keep the third-rail surface properly dressed over time.

I expect that without some current control the sectional shoes would have the usual 'brush fire' erosion at leading and trailing negotiation of poor-contact areas or discontinuities in the third rail. Neutral sensing brushes could be provided between the contact segments to allow current to be modulated in the ways used to limit commutator and brush wear in motor design.

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Posted by daveklepper on Monday, May 30, 2022 10:51 AM

This should work, with threaded broad screw-type seats for the springs  to allow precise adjustment over service time to insure proper alignment.

The right force ratio between the main springs in compression and the flipper springs in tension is important and may require some experimentation.

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Posted by daveklepper on Monday, May 30, 2022 11:06 AM

Further thought.   The spring ratios and adjustment would not be as critical, id the vertical movement of the flipper (with the contact-pad insert) has "tracks" or guides at each side to kep it horizontal at any height.

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Posted by Overmod on Monday, May 30, 2022 11:40 AM

This might be a good time to invoke Prof. Milenkovic, as one of his specialties is precisely the kind of linkage that would 'float' the shoe level with any desired level of preload.  

Final load against the rail via an array of voice coil style solenoids with helical springs located in their centers, a bit like the spring nest in a 3-piece truck.  Ice cutters fore and aft.  

I'm assuming no real redesign of the third-rail architecture that's there, so no insulating guiderails.  I'd think about increasing the lateral polar moment of inertia with weights (get out the depleted uranium???) as the voice coil servos wouldn't have trouble with it, but momentary high-g accelerations due to third-rail alignment or FOD would be less difficult to accommodate and less potentially damaging.

Some thought could be given to allowing the shoe or mount to pivot laterally and de-energize without breaking away from the truck.

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