HM7000 and older models - experiences / lessons

[George-351466]

As a modeller of some duration, the attraction of dcc was not compelling; that is until HM7000 came along. The ease and economy of free, download Bluetooth control converted me in January 2023 as soon as I read the (then) new Hornby catalogue. But…….what about my existing large layout and stock of older, but much loved locos? Converting the sectioned, cab control layout to permanently live throughout was relatively simple, producing a large pile of redundant wiring and many types of assorted switches. It took just a day of grovelling on my back and I was ready to go. 
Then there were the locos. The relatively modern Hornby and Bachmann dcc ready models (generally post 2015) posed few problems, although earlier Bachmans with 8 pin sockets in impossibly cramped loco body locations were another matter. I’ll come back to those. But I had (have) and treasured collection of Hornby Railways era and early (non dcc) Chinese models which I still wanted to run; but what to do? 
No problem, I hear you say: You Tube is full of helpful videos showing everything from early Tri-ang to later Lima, Mailine and Airfix et al, all easily adapted to take control via a dcc chip. Confident in my soldering capabilities I set forth with excited anticipation. But, here is where I’m keen to hear from others who have gone down this route; it’s been a tedious and frustrating experience - at least in so far as HM7000 decoders are concerned (I have no Select or Elite controllers to test other decoder types: I’m Bluetooth only) 

Some have worked well; notably Lima diesels, with CD motor replacements, once you delete the voltage droppers on 6v motors. Others not so, but why is that? To set the (hoped for) discussion in a wider context, here are a few of my “case studies”

Early dcc ready Bachmanns (eg Ivatt 4MT and Standard Class 4), as referred to above, cannot fit modern sound decoders where their sockets are and their part diecast, heavily and finely detailed weighted bodies make it very challenging to wire through to tenders. Once done, however, the loco-only pick-up arrangements are very unreliable, even on well laid track. Stalling could be irritating when on analogue: in dcc it rapidly renders the locos useless. So, lesson one: a stay alive (Power Bank) has been found to be absolutely essential for these models.

But when it comes to older Hornby and Triang locos, solutions have (in most cases) been elusive. Diesels seem to be more successful, but I’ve found that 2 factors are essential. 1. Power Banks are necessary to prevent stalling on points where the alternate bogie pick-ups and traction tyre arrangements inevitably lead to fatal cuts in connection. 2. Added weight - as much as possible, adds hugely to reliable, smooth running, even on level straight track. I’d given up on my Class 29 (R.080) ever running reliably until I packed as much lead as possible into it. It’s now saved my over £100 on a Dapol replacement. I assume it must be a matter of firm rail contact, where the weighty Bachmanns score well of course. 
As for older Hornby models (eg 0-6-0 tanks and tender drive steam locos); I’ve had no success. The depressing pattern is, replace Ringfield motor (CD in a tender drive, or Peter’s Spares in lieu of older XP types) wire to an 8 pin socket, plug in and link to the fitted HM7000 decoder after cleaning and lubricating mechanisms. Linking is always successful; connection is made, a profile downloaded and all sounds working. But, even with a power bank, when it comes to movement there will be a start for an inch or two, then it stops and connection is lost. Why does this happen? It almost feels like the decoder can’t cope, despite the new motors and trouble free analogue test performance. One can (almost) understand it on old 1970’s / 80’s / 90’s models, but why does my beautiful blue, rebuilt Merchant Navy model (R.2171); exactly the same mechanically as the dcc ready model produced a year later, behave the same way? Answers (and remedial suggestions) please, with apologies for this lengthy starter. 

 

 

 

[ColinB]

I have converted many of my old models to DCC that includes many Ringfield motors and Bachmann split chassis. The ones I don't convert are my Wrenns because why butcher a collectable loco and some really old Triang locos where the pickup arrangement is not that robust and it is so easy to short the motor to the pickups taking the decoder with it. The big issue is that a lot of these locos use high currents in Model Railway terms so a good starting point is to test them with a decent decoder that has decent motor control. I used Zimo ones for my conversions, I found Hattons, Hornby and many others had a habit of blowing up even though according to the specification the current limit should be ok. I have never tried with a HM7000 but to be quite honest if you want to convert your old locos, convert them to DCC first, check they run ok then add the HM7000. I have seen a number of posts saying that these decoders are not as reliable as they should be, one of mine just failed for no valid reason. As to the Blue Merchant Navy, I converted mine, in fact the new ones Hornby make to this day are no different except they have put the decoder in the tender. When I converted my one I decided the area inside the loco was too cramped so I I added the 4 pin connector between loco and tender and put the decoder in the tender with a socket so it is easy to test and upgrade decoders if you ever need to.

I forgot to add adding extra pickups as you have, improves things a lot, with the class 29 ( I have one ) the big issue is that the ringfield has traction tyres so you cannot pickup current on these wheels. I also added extra pickups to the trailing bogie by using later Hornby parts.

Edited March 30 by ColinB

[ntpntpntp]

22 hours ago, George-351466 said:

Converting the sectioned, cab control layout to permanently live throughout was relatively simple, producing a large pile of redundant wiring and many types of assorted switches. It took just a day of grovelling on my back and I was ready to go. 

?  Seems like a lot of unnecessary work and irreversible should you still wish to run some of your DC locos?
My 25+ year old N gauge layout is wired for DC cab control and runs DC 99% of the time.  If I wish to run DCC I simply remove all DC locos, connect a DCC system to one of the cabs and switch all sections to that cab.   No wiring changes necessary 🙂

[ColinB]

52 minutes ago, ntpntpntp said:

?  Seems like a lot of unnecessary work and irreversible should you still wish to run some of your DC locos?
My 25+ year old N gauge layout is wired for DC cab control and runs DC 99% of the time.  If I wish to run DCC I simply remove all DC locos, connect a DCC system to one of the cabs and switch all sections to that cab.   No wiring changes necessary 🙂

I know I read a lot of posts like these on this forum. What people don't understand is that all you need to do, is feed the same DCC signal to all sections so basically paralleling up the feeds to one source. The separate isolating sections are really useful if you have a short you cannot find.