A4 Mallard stalling on points

[Andy Train]

Hi all

i have purchased a used Railroad Mallard with tender which stalls on my electrofrog points 

All my other Hornby locos cross without stalling , so it must be this loco.

any advise would be appreciated , thanks 

[Flashbang]

Hi

Can we confirm that its actually Stalling - Stopping with the power still on the rails and DCC console display still remains lit and visible? Or its short circuiting the DCC system causing the display on the DCC console to disappear for a brief time? As there is a very large difference to what the cause might be.

[Andy Train]

Hi

the Mallard just stops and won't cross the point without a push

sometimes it decodes the decoder so I have to reprogramm with my Elite

[96RAF]

That indicates a short is resetting the decoder.

 

You say it decodes the decoder. I translate that to mean the decoder reverts to default address 3. Can you confirm that is what happens before you refresh the address by reprogramming.

 

Can you confirm the connection type between loco and tender. Is it a post on the tender connecting with a drawbar on the loco that has springy fingers or is it a fixed drawbar with a four pin plug on the loco into a socket on the tender, or even nothing at all In the way of electrical connection between the pair.

 

In the absence of that could you take the leading bogie off (one screw and maybe a spring) and see if that helps or hinders.

[Flashbang]

As we are on DCC it is possible that the wheels on the loco or its tender are out of gauge. i.e. their Back to Back is not correct known as B2B. It must be set to 14.5mm maximum. Special B2B gauges are available to test and reset the wheels on each axle, this includes all loco pony truck, bogie wheels and Tender wheels too.

If any wheel set is too wide (greater than 14.5m) its very possible for a metal wheel to bridge both Vee rails where they are closest at the frog and cause a short circuit to occur.  Re setting the wheel(s) to the correct B2B gauge should remove the problem. If it doesn't, then consider fitting Insulated Rail Joiners (IRJs) to the points vee rail ends to stop the shorting occurring See... https://www.brian-lambert.co.uk/DCC_Page_1.html#Bookmark4

[ColinB]

Why is it every fault is a back to back issue. I have had a lot of back to back issues on my old Hornby Ringfield based locos and they definitely don't do this. For a start they either derail or you hear a clomp as they jump over the point or they stop and blow up the decoder. To be quite honest most modern locos are better than that. The way the front bogies are designed makes it virtually impossible, I know because one of the things I have done to my old locos is replace the wheels of the front bogie to new ones.

I had exactly this issue with an A4 and a Bachmann diesel, I imagine it is a large radius point, either curved or a normal large radius turnout. As the loco turns it is possible for it to short on the guide rails of the point, it took a while for me to work it out. I wondered when I bought the new Peco electrofrog points why they had the facility to isolate the frog, this why. So what I did is isolate the "frog" as Peco recommend but don't use a switch off the point to power it, use one of those autofrog devices, the problem will disappear.

Actually thinking about it, it was a renumbered Railroad Mallard that caused the issue, so there must me something about its wheel geometry, but as I said the Bachmann class 47 did the same.

[Fishmanoz]

Colin, when begging to differ from one of the more experienced posters on the forum, might I suggest that you start your post somewhat differently.  Something like this might be better:

 

"If Flashbang's excellent advice does not solve your problem, you might consider these alternatives ............"

[ColinB]

I am sorry perhaps I could word it better, experience is the ability to have seen the issue before, so someone who only posts once may have the answer. I regularly measure the back to back measurements on my locos when I have an issue and as I say, it generally occurs on old locos where you can push the wheel anywhere on the spindle and you can hear it as it clomps over the points, if it doesn't derail. That is definitely the case with Peco ones. It can easily happen on carriage and wagon wheels as again you can push the wheel anywhere on the spindle. Most of the Hornby front bogie wheels are capped so it is extremely difficult to push them any further on the spindle. As I said in my first post, I actually saw this fault on a large radius point, it took me ages to figure it out, it is a difficult one to figure out. Peco obviously noticed this as an issue as their older points didn't have this feature. Perhaps it only happens with electrofog points, which is why I see it and others that use Hornby track don't. 

[Andy Train]

Hi 

it is the Mallard with the draw bar and springy fingers

if the mallard stops on the point it does not trip light a short it just stops and I have to reset the address with my Elite it does not appear to go back to the default address no 3 it appears to wipe all addresses.

i have checked the wheel setting and they are correct .

at speed the momentum of the loco with cross but not at normal or slow speed it stops 

any ideas would be appreciated 

thanks 

Andy

[Flashbang]

Check the fingers on the tender to loco connection are not able to touch the central pin. Also ensure the fingers of the Y shaped pin connector and the two contact fingers are all spotlessly clean, as too is the pin and plate and they are all making good and continual contact to either the pin or the wiper plate that the fine fingers rub on.  Use a Fibre pencil to clean all areas of contact.

 

Reentering of the address, indicates its losing data or momentarily shorting! Causing the stall.   

[96RAF]

This may help with the springy finger thing...

 

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[Andy Train]

Hi

i have checked all the above and all seems correct.

i am now running the loco without the tender and it still stops as the wheels hit the frog , I am using live frogs.

so I assume that it must be the loco wheels that are causing the stalling . The Elite is not shorting or loosing the data from the decoder which was the problem when the tender was attached.

the wheels are all perfectly in line and I can't see how they could be adjusted as they appear fixed to the spindle.

the brushes are all in place and touching the wheels.

This Mallard stops on every point not just one ,  my other simila locos cross at low speed with out an issue , including the Hogwarts train  and Maude 673 and Bach**n locos    I have fitted insulated rail joiner in the V of the frog.

The only other loco which stops at low speed in a small 040 southern 63 which has never been a good runner,

I am reluctant to purchase other locos until this issue is solved 

many thanks Andy

[ColinB]

Did you try my suggestion of isolating the frogs and putting in an autofrog device? As I said previously, it worked for me. What I did with mine to test it, I cut the links to isolate the frog. With your Mallard because of the long wheelbase it should go over the point even though there is no power to the frog. If it fixes the issue, then add the autofrog so it works for slow moving or short wheelbase locos.

[96RAF]

Take the front bogie and pony truck off and see if the bare driver chassis will traverse your points. If so then replace those bits one by one and recheck.

My MN was shorting as the main driver live wheel rim moved across to hit the valve gear.

[Andy Train]

Hi

i have tried running the loco without the tender , but it still stops on each point unless I run at speed then it will judder but the momentum carries it over the point 

thanks

[96RAF]

My suggestion was to  run it with the front bogie (under the pistons) and the trailing pony truck (under the cab) removed as well without the tender. This will narrow the problem down to the main driver set. If that runs OK then reattach the pony truck, if that is OK then it points to the front bogie. The back to back dimension is easily adjusted on those wheels, as you sy not so esy on the main drivers which will require advanced skills to shim the back to back exactly and ensure the motion gear quartering is not disturbed.

[ColinB]

I don't know if you ever got round to isolating the frogs on the electrofrog points but I had a similar issue. What happens is when the loco traverses the points if it has a long wheelbase the back of the wheel can touch the moveable part of the blade that is not in contact with the rail. If you haven't isolated the frog then the supply from the other side of the blade that is touching the rail makes the whole of the blade live, basically both sides, so if the back of the loco on the non switched rail touches it, you get a short. If you cut the links and power the frog separately, this doesn't happen. Unfortunately, Peco don't explain the reason you need to isolate the frog in their instructions. I hope that explains it, is a bit difficult without a diagram. I spent a good hour trying to analyse what was going wrong with mine.

[BR63]

Taking  different tack.... remove the front bogie and rear truck as RAF suggested. Now with no power running place the main engine on the track and with a finger push the engine through the turnout with a finger behind the firebox.  If you feel a resistance as it goes through then you don't have an electrical problem it is a mechanical problem.  Perhaps the B2B as previously mentioned,there is a small foriegn body in the gap between the stock and check rail or the main wheel flanges are too wide.  Run the front bogie and rear truck the same way.

Hope this helps.

[creilly81]

If this is a railroad model, can you check to see if indeed the tender has pick-ups as disconnecting it if it hasn't wouldn't change anything anyway.

I'd be suprised if the tender does have them, that it should stall.

[ColinB]

The other thing to check if they are electrofrog points, is that the little links to the frog aren't broken. Peco make them breakable so you can separately power the frog but I have found on my points they seem to break on their own, which means the frog is isolated. I must admit I would have thought it would show up on your other locos, but you never know. I have had a couple of points where they were working one day the following day the link has magically broke itself. The other issue is the Railroad Mallard has those stupid finger things on the coupling between loco and tender if it is like mine, are they working properly? If not you don't have any tender pickups.