Re: Wiring a Shinahora Double Crossover for DCC
Vollrath, Don <dvollrath@...>
A couple more commentstoggle quoted messageShow quoted text
1. Note the close proximity of rails of opposite polarity near the frog points. This is where extra wide wheel treads and out of gauge wheel sets may contact both rails. Also there are rail-rail bonding ties at the bottom of the wheel flange trench at the frog. these are supposed to be burried into the plastic but on 2 of my samples are actually exposed. Older wheel sets with oversized flanges can touch the wrong rail polarity while rolling through.
2. Making the the switch DCC friendly includes making the 'unused' point rail the same polarity as the adjacent stock rail. In most cases including this one, it requires cutting gaps in the closure rails just before they reach the frog as Allan has shown. But this becomes an 'unfriendly' DCC problem only when using older oversized or out of gauge wheels or only when there is an actual derailment. Good running wheel sets should not be brushing their backside against the other point rail when it is open. If you are willing to gamble on that, then you don't have to cut any rail gaps. Just let both point rails become the same polarity as the frog, as originally designed.
3. The original Shinohara design uses a copper strap at the points as a sliding switch to selectively power the point rails and frog to the right stock rail polarity as each switch is thrown. This works OK but has all the potenital of poor electrical contact due to oxidation, dirt, etc. Ditto for where the point rails swivel. One needs to add continuity jumpers around the swivel point to fix that particular problem. [Making the swivel joint with rail joiner-like clips is better than rivets, but still subject to ageing problems.] Adding an external electrical switch to provide a better electrical connection to point and closure rails is necessary to avoid the problems of a dirty or work copper contact at the rail points. JMNust make sure that the electrical switch transfers power while neither point contact is touching.
4. If you add the external supplementry switch as in #3, and are willing to live with or eliminate the problem of #2, You don't need to cut any new rail gaps. The problem of the exposed built in bonding wire being exposed of #1 can be avoided by simply throwing all four throwbars to be in the same position at the same time. Easy to do if you are using 4 tortiose machines.
From: wirefordcc [mailto:email@example.com]
Sent: Monday, March 28, 2005 7:11 PM
Subject: [WiringForDCC] Re: Wiring a Shinahora Double Crossover for DCC
Here's a drawing of the double crossover that shows what Don is
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