reversing loop

[david_watts1]

Just wondering, if you fit all of your locos with stay alives could you get around the reversing loop problem by simply having a dead section that is longer than the loco.

[Fishmanoz]

Excellent and thought-provoking question David!

My answer - yes, as long as some conditions are met. I’ll get to those conditions below.

First, given you’ve asked the question, I’m going to assume you understand the RL issue of DC polarity reversal or DCC phase reversal and the need for an isolated section (IS) to stop either reversal resulting in a short circuit of track power.

Given this fact, I’m going to reframe your question - is it necessary to power the isolated section in an RL with an RLM or other switching arrangements?

To this, I’m going to answer no as long as some conditions are met.

First, the best practice IS is longer than the longest train and must not have more than one train entering/leaving at the same time. The reason is to cater for there being electrical continuity along the length of the train. This can only happen if there is continuity from couplers to (metal) chassis to axles.

I believe this is unlikely with modern rolling stock, so my first answer becomes - no power is need to the IS as long as it is either longer than the longest train, or longer than the longest loco and tender and there is no electrical continuity along the length of the rolling stock/rake.

First complication to take account of - something like lit Pullmans where there is electrical continuity between the front a rear bogie axles due to them having wipers to power the lights. This means the IS must be longer than the longest item of rolling stock if it has continuity along its length.

Different complication - you can’t end in a position where the stay alive discharges with the loco still in the IS. You can avoid this either by having operations that don’t have the loco staying/running in the IS for longer than continuous operation of the stay alive or - be able to switch power into the IS from the direction of exit by the loco from the IS.

It shouldn’t be too difficult to meet the above, so in practice the IS can work unpowered by an RLM or otherwise. In particular, the HM7000 power bank with 7 plus seconds of operation time will be able to operate this way.

Mods - this is a DCC question, not an HM | DCC question and should be moved to the DCC forum.

[rpjallan]

Just wondering, if you fit all of your locos with stay alives could you get around the reversing loop problem by simply having a dead section that is longer than the loco.

 

 

Having had a reverse loop on my layout for many years (using Hornby's original Reverse Loop Module) & having many locos fitted with stay alives, from small ones to quite large, I think that would be a very hit & miss (mainly miss) solution...

[P-Henny]

If you read the 'Reverse Loop Tutorial' sticky. It states and explains why the protected section needs to be longer than your longest train and not just the loco. This would mean that any dead track in your suggested solution would need to be at least that length. Only very large 'stay alives' are likely to last that long.

EDIT: Mine is an abridged (more basic) version of Fishmanoz's reply.

[Brew Man]

Coupled with the fact you would need a Stay Alive in each loco, which you may want anyway, but there will be some that don't have the space to fit one. A RLM costs about £30 and will be the only one you will need, (unless of course you have more than one reverse loop).

[Rallymatt]

Although technically possible, I think the hassle and cost of fitting capacitors in every loco, and then running the loop so that each train exits the IS before the capacitor is dry makes it less flexible than fitting a RLM.

My reverse loop is a diagonal crossing from one side of an oval to the other, across a viaduct and running will sometimes require trains to wait on the viaduct for the lines ahead to clear before they can re-join the main up/down lines. I’m back because of TT and finding a decent RLM has been quite a challenge. No stock from Hornby so can’t comment on that but one from a rival was relay activated and quite dim witted, I have gone with a Lenz unit that operates seamlessly and is quite compact.

[Brew Man]

I got mine from Block Signalling and cost a whisker under £30, Works a treat.

[rpjallan]

My reverse loop is a diagonal crossing from one side of an oval to the other, across a viaduct and running will sometimes require trains to wait on the viaduct for the lines ahead to clear before they can re-join the main up/down lines.

 

 

Yes, I quite often have trains sitting in my reverse loop for a while also.

 

 

[96RAF]

The old Hornby RLM is also ‘dim witted’ as you term it with mechanical relays. Its only sophistication is a sensitivity switch to cater for the 1-amp vs 4-amp PSU self protection. See here for details of its innards http://www.halton96th.org.uk/page19.html

The new RLM is likely to be bluetooth to support use with the HM7K system.

[Brew Man]

I seem to recall when I was looking for a RLM that the Gaugemaster offering was not compatible with Hornby controllers, but I can't remember why that was. Does anyone recall the reason why?

[96RAF]

I think Chris covered that in his guide.

[Brew Man]

Right, I'll have a look. I remember it making perfect sense at the time.

[rpjallan]

I have to say that I have never had a problem with my Hornby RLM. I do know some people who have had problems with other brands of relay based modules though.

Why would you need Bluetooth on a RLM?

[P-Henny]

Why would you need Bluetooth on a RLM?

 

 

I don't think anyone has said it does have BT on it. But if it did, then maybe to use the HM7000 APP to configure a trigger current OR perhaps to act as an additional mesh node to increase BT range.