Improving reliability of Hornby TT120 points

[Hobby11]

After wiring my layout I had a play and found that the power continuity through points was iffy to say the least. The issue isn't the dead frog but the connection between the switch blade and stock rail and that sprung connection. I have found it very hit and miss and a real pain as the points are at the front so having to nudge the loco isn't an option. I did look at replacing all the points with Peco ones but it would have involved a lot of track relaying as the geometry is different.

After some thought I've worked out that I can make the connection using a switch rather than rely on the blade. My layout is DC like all my others and when using Peco points I use a slider switch to switch frog polarity. I've worked out that using a DPDT slider switch I can use the same principle with the Hornby points and won't have to rely on the point blade. 

I've ordered some switches on Amazon and should get them tomorrow and I'll keep you updated. I know it won't work for everyone as, unlike a live frog point, it uses a DPDT switch rather than a SPDT switch but some may find it useful.

Edited July 25 by Hobby11

[ntpntpntp]

You only need an SPDT switch,  wire the two frog exit rails together to make them behave like a Peco Electrofrog. 

 I do this with Peco Insulfrog points in my automated fiddleyard as you can see here (the wire linking between the V rails runs to the SPDT accessory switch attached to the point motor)

 

For manual points I use wire-in-tube and an SPDT slide switch

[Hobby11]

I'm not going to make them operate that way as I want them to operate like they are built to, with one rail and siding beyond it "dead". If I were to wire them as per a live frog I'd have to add insulated fishplates and added wiring and switches. I did think about that route but recon this would be easier as the track is already laid and wired. As I'll be using DPDT slider switches any how it just seemed easier.

Edited July 25 by Hobby11

[Hobby11]

Now finished the set up. Slider switches and omega loops installed for each of the points at the front, wired as I said earlier so that I am not relying on the point blade for electrical continuity. Tested and ok, now for the ballasting!

[What About The Bee]

Charlie, at Chadwick, demonstrated a useful technique improving continuity.  I cannot put my finger on the episode, he has so many.

The technique relies on soldering a small loop of wire between each point blade and the corresponding wing rail.  The wire must be a long loop, to permit motion without restriction, and further to that end, multi strand to be flexible.

The loops reside in holes in the baseboard, under the point.  There is a bit of fettling with the plastic sleepers.

The power to the point blades is no longer necessary through the elbow, rather it flows through the loop.  

If I can find the episode, I will update 

Bee

 

Edited August 1 by What About The Bee

[Hobby11]

If I understand that correctly it would make the blades live and prevent the sidings bring isolated. I wantd to keep them as Hornby make them, the only live track is the one the point is set to.

[ntpntpntp]

@What About The Bee  Bonding the blades to the stock rails will remove the "power routing" capability of the point (what the Continental brands used to call "thinking points" 🙂  )  That bonding is also part of the "DCC friendly" modification some people carry out on live frog points, along with cutting and isolating the frog from the blades. 

Bonding the blade to the wing rail at the pivot overcomes any problems with continuity at that joint.  I've done that with a few Peco N gauge points and also G scale points over the past few decades, but it's not the main cause of problems.   This won't affect "power routing" but then you're still relying on the blades for continuity. 

Edited August 1 by ntpntpntp

[Hobby11]

Yep, that's what I thought, NTP, just to clarify my layout is DC and the modification is to improve running but keep the points as designed. And it does just that!

[What About The Bee]

I defer to @ntpntpntp

I could have sworn that power would still be switched via the blades and relied upon blade contact with the stock rails.  The wing rails rely upon power from the blades, and the loop merely improves continuity over the sliding elbow.

I stand corrected and accept error

Bee

[ntpntpntp]

@What About The Bee you are correct, however I don't think the blade pivot is as troublesome as the blade contact itself (with or without those little contacts Hornby points seem to have under the blades).  It's the blade contact issues @Hobby11 is working around. 

I just bind both frog rails to an SPDT change-over switch to create the equivalent of Electrofrog points in terms of power routing  - ie. they still select one or other route but instead of the other frog rail being dead both rails become the same polarity =  no voltage to drive a motor.  Accessory switches on point motors are typically SPDT not DPDT. 

Edited August 1 by ntpntpntp

[What About The Bee]

Whew!   I was beginning to think I had communicated poorly.  I was in the process of creating a diagram to clarify what I was relating, and still couldn't see the issue @ntpntpntp

Over long term use, those elbows will wear and become unreliable, intermittent.  In retrospect, TT points are too new to be at that stage yet.

I still defer to you!   Ha!  🙂

Bee

[Hobby11]

The points are just made the same way as the British RTR manufacturers have always made them for setrack, in this case it suits me to have them work that way. I could have done what NTP did, in fact one less wire, but I had the DPDT switches so just set it up to work as they were made to. Charlie's way I suspect is for DCC , same as those little spring wires that Hornby do but a little more robust, but as I said my layout is DC!

Just out of interest @ntpntpntp am I right in thinking that your way would only work on dead end sidings? If there was a loop it would short unless my mental picture of it is wrong!

Edited August 2 by Hobby11

[Paul M]

DC only here, and I switch mine manually, taken a lot of fiddling to get them all working. All worked fine in testing after gluing the track down before ballasting so it was a bit frustrating. 

[ntpntpntp]

6 hours ago, Hobby11 said:

Just out of interest @ntpntpntp am I right in thinking that your way would only work on dead end sidings? If there was a loop it would short unless my mental picture of it is wrong!

That's why I said I treat them the same as Electrofrogs, where an isolating joiner is required after the frog V rail if that rail has its own power feed further along. 

With a loop you can "get away with it" as long as both points are set to the same route.  OK for DC but with the constant power of DCC you'd have to sync both point changeovers absolutely precisely to avoid a short.  So it's easier just to insert isolating joiners somewhere!