# Dead spot in switches



## rbr (Apr 27, 2014)

Hi everyone,

I have (2) Piko 35224 curved switches. The inside curve is radius 3 (roughly LGB 1500) and the outside curve is radius 5 (roughly LGB 1600). 

They both have a "dead spot" where the train will stop completely (if going slow enough) or slow down (if going a little faster). The "dead spot" is where the plastic piece of the switch/rail is. 

How do I fix this?

Thanks


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## Garratt (Sep 15, 2012)

The frog is very long on some switches so some rely on the wheel flange to ride on a metal contact in the bottom of the frog to maintain electrical conductivity. If you have shallow wheel flanges they lose contact and stall. The wheels dropping off the point of the frog would be evident of this happening.
Stalling will happen on short locomotives with few electrical pick-ups. I suspect you have n 0-4-0 with a wheelbase shorter than the plastic frog length. You could add electrical pick-up on pilot wheels etc. creating a longer total pick-up length or build up the contact height but that may interfere with anything else with deep wheel flanges causing the wheels to lift higher through the frog. 
A trailing tender or car with electrical pick-ups wired to the locomotive is another way of spreading the total pick-up length so stalling cannot occur. 

What locomotive are you having trouble with?

Andrew


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## East Broad Top (Dec 29, 2007)

Andrew my first guess on the head. You're running into the age-old problem called a "dead frog." Because that's where the rails come together, if the frog was metal, it would short the power out. So, manufacturers use plastic or otherwise insulate the frog from the rails so there's no power to short out. The drawback--the longer the switch, the longer this "dead" spot, and the greater the chance that locomotives with short wheelbases (thus limited power pick-up) will stall when it hits this section. This is probably the oldest problem in all of model railroading, and plagues all scales. This particular switch has a very long "dead" frog, so the chances that short locos stall is greater.

A few thoughts. First, from photos I'm seeing online of the Piko curved switch, it looks like it's got metal strips on the bottom of the flangeway through the frog. The idea here is that these strips are powered, and as the flange rides through the frog, the tips of the flange make contact with this strip, so power can flow to the wheels, thus to the motor. It helps reduce the "dead" spot of the switch, allowing short-wheelbase locos to run through without stalling. Without seeing your specific switch, I don't know if yours has these or not.

If your switch has these, (a) make sure power is going to those strips from the adjacent rails. (An ohmmeter will tell you that there's electrical continuity, or you can apply power and measure the voltage from the outside rail to the strip on the bottom of the frog.) If you're not getting power to that strip, then that's the first thing you'll want to fix. If there is power going to this strip, check to make sure it actually makes contact with the tips of the flanges as they roll through the switch. It may not, depending on if the flanges are not deep enough. Different manufacturers use different flange depths. Piko's flanges are on the deeper end of the spectrum, so it could be they engineered their switches with deeper flangeways that other manufacturers' wheels don't reach. These frogs are often referred to as "flange-bearing" frogs; i.e, they're designed so that the wheels riding through them roll through on the tips of the flanges as opposed to the treads of the wheels. It's supposed to make things run smoother, but you need consistent flange depths for that to work. Manufacturers are anything _but _consistent when it comes to flange depths.

If the tips of the flanges aren't making contact with this strip, you'll want to flex this strip up a bit so that it can make contact with the tips of the flanges, thus get power to the wheels. You could try adding shims under the strips, too, but you run the risk of equipment with deeper flanges "bumping" through the switch. If you can get away with just flexing the strips up so they're springy, the weight of the equipment will press them back down, reducing the "bump."

Other alternatives; you could make the frog a "live" frog. This requires a little bit of work and an electrical switch in conjunction with your switch throw. To do this, you'd add a thin brass or copper "strip" to the top of the V-shaped point of the frog that stops just short of the end of the frog where the rails join the plastic. Then you'd solder a wire to this strip, and run it to an electrical switch. The other two contacts on that electrical switch would be tied to the position of the points of the switch, so that the frog gets power from the appropriate rail. This is common in high-end HO scale switches (called "power-routing" switches), but has yet to really catch on with the big commercial track manufacturers. 

If you can't or don't want to modify the switches, your alternatives are to add additional power pick-ups to your locomotives, so that the length over which the loco picks up power exceeds the longest "dead spot" you would have on the railroad. This is hard to do on small locos like 0-4-0s, but if you've got a tender, you could add power pick-ups to the trucks on the tender. You could also add strips of phosphor bronze strips as sliders behind the rear drivers that would make contact with the rails as well as the drivers. Again, this is an age-old problem in all scales, so if you have access to back-issues of _Model Railroader_ or _Railroad Model Craftsman_ magazines, you'll likely find a bunch of articles on improving electrical pick-up of small locos. I remember a ton of 'em from back in the 80s when I was in HO scale, trying to tweak my steam locos for smoother operations over my dead-frog switches. (I ultimately switched to the higher-end "power-routing" switches.)

Of course, I would be remiss if I didn't sarcastically suggest converting to battery power...  I'm joking (well, partly). But in the interest of full disclosure, I haven't pushed electrons through my rails in 30 years, so my "firsthand" experience fixing issues with switches is based on my experience in HO scale, and learning from others in large scale who have fixed these issues on their own switches. 

I'm also not addressing the possibility that these problems are not electrical, but mechanical. That's a different ballgame, but you'll want to take a close look at the wheels of your locomotive to see what they're doing as they go through the frog, to see if they're catching on anything that might be causing issues. There are fixes for that as well, so if all the electrical issues check out okay and it's a mechanical thing, let us know and we can work with you to sort those out as well. There's no such thing as a switch that can't be fixed. It's just a matter of how much of the switch you want to replace to fix it. 

Later,

K


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## ntpntpntp (Jan 14, 2008)

I don't own any Piko switches, but I do have a couple of LGB R5 switches. These have metal strips in the base of the frog, which are reasonably effective when running LGB locos but no use with other brands that have smaller flanges. 

I'm used to having live frog switches in the small scales. in order to make these R5 switches live frog, I removed the plastic centre V (it's a separate part) and made up a replacement from brass rail. It's quite a complex shape using just the head of the rail for the most part, but once in place it totally cures the problem. As EBT stated, you need to use an electrical change-over switch to power the frog, and also ensure that both V rails are isolated just after the frog.

I'd be interested to know if the Piko frog is a similar design with a removable V? 

Nick


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## Pete Thornton (Jan 2, 2008)

> How do I fix this?


 The (expansive) solution is to change to on-board battery power. Then the track just guides the wheels, and all those problems go away.


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## Garratt (Sep 15, 2012)

A buffer capacitor fitted will give the locomotive a small amount of reserve power when the power drops out while going through the frog. It will smooth out the power supply and get the locomotive through short spots with no conductivity.
It is still possible to stall if you stop the locomotive on the electrically dead spot though.

http://www.shourtline.swl4.com/SL-6101047_4,700uF_Automatic_Power_Buffer_EBAY.html

Andrew


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## Dan Pierce (Jan 2, 2008)

The above power buffer is not for track powered analog/DC as it is polarity sensitive.
Decoders have the option of having a capacitor added to the internal electronics.


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## Greg Elmassian (Jan 3, 2008)

Jeeze... at least when trolling spell correctly.... 



Pete Thornton said:


> The (expansive) solution is to change to on-board battery power. Then the track just guides the wheels, and all those problems go away.


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