Bachmann Ivatt Cutting Out on Hornby Points

[latestarter]

Some will have seen my long thread in another part of the forum about setting up my layout. I felt this was a separate issue, albeit tangentially related, so I've started this thread. I hope that's OK.

My Bachmann Class 2MT Ivatt 2-6-0 46520 (bought 'pre-owned' and fitted with sound from Hattons a few months ago) stops moving as the front bogie comes over the Hornby DCC point clips on at least 2 Hornby R8073 points on my layout. This usually happens when the loco is moving at less than half speed on the controller (Hornby Select). If moving faster than half speed it seems to have enough momentum to avoid stalling, although I have noticed it appear to 'judder'.

The track is not yet wired up, but has power throughout via a Hornby 4amp transformer. That said, I have had 3 locos running simultaneously, and at good speeds. the problem occurs if the Bachmann is running alone or with other locos. 

Any thoughts are welcome and I would be happy to offer further details if needed.

Edited November 6, 2021 by latestarter

[Butler Henderson]

Have you checked all pick ups are correctly aligned? Could be that the plastic frog is slightly raised lifting the front driving wheel off the metal rail and also possibly the centre one as well.

[latestarter]

28 minutes ago, Butler Henderson said:

Have you checked all pick ups are correctly aligned? Could be that the plastic frog is slightly raised lifting the front driving wheel off the metal rail and also possibly the centre one as well.

Thank you for that. I'll have a look at the pickups. I'm not entirely sure how they should be set (very new to model trains) but I might be able to work it out.

[Butler Henderson]

The pick ups will be thin phosphor bronze strips that should  bear on the back of the wheels at all times so you need to check  them at the outer limits of the sideways movements of the wheels. If any are not bearing properly they can be corrected using a pair of small flat head jewellers screwdrivers . Use one to hold the pick up strip on to the rear of the metal tyre of the wheel and use the other to form an appropriate gentle bend in the strip.

[latestarter]

39 minutes ago, Butler Henderson said:

The pick ups will be thin phosphor bronze strips that should  bear on the back of the wheels at all times so you need to check  them at the outer limits of the sideways movements of the wheels. If any are not bearing properly they can be corrected using a pair of small flat head jewellers screwdrivers . Use one to hold the pick up strip on to the rear of the metal tyre of the wheel and use the other to form an appropriate gentle bend in the strip.

Thank you again. I'll have a proper look tomorrow and come back to you. Much appreciated.

[Nick Holliday]

Could it be that the back-to-back of the pony wheels is too tight, causing the back of the flange to make contact with the opposite-powered rail at the frog? Although I would have thought the loco would stall closer to the frog, but maybe the momentum when testing takes it a bit beyond the point of contact. Perhaps try a run through in the dark to see if there are any flashes.

[Flying Pig]

While you're checking the pickups, also clean out any fluff and gunk that has accumulated on them.

[latestarter]

3 hours ago, Nick Holliday said:

Could it be that the back-to-back of the pony wheels is too tight, causing the back of the flange to make contact with the opposite-powered rail at the frog?

 

I actually don't know what this means. I'm very new to all things model railway, and not familiar with the jargon yet.

When I trained (pun intended) in psychoanalytic psychotherapy in the 1980's, I told my supervisor that my patient was...using projective identification to sublimate the unconcious angst created by the demise of her sibling. The supervisor replied...for God's sake just tell me what she is doing!

Edited November 7, 2021 by latestarter

[latestarter]

48 minutes ago, Flying Pig said:

While you're checking the pickups, also clean out any fluff and gunk that has accumulated on them.

 

I will, thank you.

[Flying Pig]

18 hours ago, latestarter said:

 

 

What's going on with the sawcut through the rails just ahead of the loco in this picture?  That isn't usual for the kind of points you're using. 

[latestarter]

21 minutes ago, Flying Pig said:

 

What's going on with the sawcut through the rails just ahead of the loco in this picture?  That isn't usual for the kind of points you're using. 

I've just been to have a close look, as I definitely haven't taken a saw to anything. I can't see that 'line' at all on the points. The only 'lines' in the rails are where the track pieces join and they are flush.

[latestarter]

@Butler Henderson @Flying Pig @Nick Holliday Thanks for all the help with this guys. I took some snaps with my phone, all but one is too blurry show you, but these are the main findings (excuse my lack of correct language):

1. The pick ups on the pair of wheels on the loco, closest to the tender lose contact if I move that pair of wheels side-to-side.

2. There are thin black wires touching the front pair of wheels. There is a similar pair near the middle set of wheels, but they are not touching the wheels, as far as I can see.

3. Should the plastic bracket-shaped bar at the front of the two front two wheels (pony wheels?) sit on the rail? See photo. I took the front coupler off, as I thought it might be part of the problem.

[Flying Pig]

1 hour ago, latestarter said:

1. The pick ups on the pair of wheels on the loco, closest to the tender lose contact if I move that pair of wheels side-to-side.

 

Ok, those will need to be adjusted to maintain contact all the time.

 

1 hour ago, latestarter said:

2. There are thin black wires touching the front pair of wheels. There is a similar pair near the middle set of wheels, but they are not touching the wheels, as far as I can see.

 

I suspect these may not be pickups, but represent the sand pipes on the real loco (they don't do anything on the model).  They should come down vertically near the wheel then bend through about 45 degreed to point at the wheel tread, but should not touch either the wheel or the track.  

 

The pickups should be like the ones on the rear wheels and contact the back of the wheels.

 

1 hour ago, latestarter said:

3. Should the plastic bracket-shaped bar at the front of the two front two wheels (pony wheels?) sit on the rail? See photo. I took the front coupler off, as I thought it might be part of the problem.

 

 

No, again these are not functional on the model but represent the 'guard irons' on the real thing.  They should not touch the track.

 

Did you find any improvement with removing the coupling?

[latestarter]

18 minutes ago, Flying Pig said:

Ok, those will need to be adjusted to maintain contact all the time.

 

 

I had a go at pushing the contacts against the rear set of wheels, but no luck as yet. They seem to want to sit inside the wheels, near the 'spokes' rather than on the flat rim o the inside, where the ones on the other two sets sit. I'll keep trying, as I suspect (with all the help here) that this may be the issue.

Quote

I suspect these may not be pickups, but represent the sand pipes on the real loco (they don't do anything on the model).  They should come down vertically near the wheel then bend through about 45 degrees to point at the wheel tread, but should not touch either the wheel or the track. 

  I'll move them away from the wheels a bit.

Quote

Did you find any improvement with removing the coupling?

Not really, I'm thinking of putting it back on. Thanks for all the advice.

[Butler Henderson]

You can see the pick ups in a partly dismantled model shown on this page

https://www.rmweb.co.uk/community/index.php?/topic/28805-ivatt-2mt-2-6-0/&tab=comments#comment-303029

 

[latestarter]

52 minutes ago, Butler Henderson said:

You can see the pick ups in a partly dismantled model shown on this page

https://www.rmweb.co.uk/community/index.php?/topic/28805-ivatt-2mt-2-6-0/&tab=comments#comment-303029

 

 

Thanks very much for that, and it's a bit worrying. The ones I can see (in the last photo) seem to show the pickup lying along the curve of the wheels (sort of upside down half-moon shape). But, mine hang down from inside the loco, with the small 'dot' touching the wheel.

This may have a bearing on why my Ivatt is not crossing the points well, and not at all when less than 1/3rd speed - even though I seem to have got all pickups touching the wheels. . I wouldn't be skilled enough to dismantle the loco, but I'll have another look tomorrow to see if the pickups can be re-arranged without snapping them off.

[Butler Henderson]

Can happen if the pick up is not correctly aligned that it then catches on parts of the wheel and get twisted silightly.  The solution is probably to undo the keeper plate to gain better access; the plastic bottom of the loco, usually two screws plus removal of the pony truck (front wheels) noting from the photos that it needs to removbed in a hinged action due to the wires attached to one end.

[latestarter]

Thanks again I'll try and have a look tomorrow.

[Nick Holliday]

On 07/11/2021 at 10:01, latestarter said:

 

I actually don't know what this means. I'm very new to all things model railway, and not familiar with the jargon yet.
 

 

 

On 07/11/2021 at 06:36, Nick Holliday said:

Could it be that the back-to-back of the pony wheels is too tight, causing the back of the flange to make contact with the opposite-powered rail at the frog? Although I would have thought the loco would stall closer to the frog, but maybe the momentum when testing takes it a bit beyond the point of contact. Perhaps try a run through in the dark to see if there are any flashes.

 

What I was trying to say may be explained by the diagram, where I have coloured the rails either in blue or green to represent the polarity of the power supply.  I am assuming that the two links have been connected correctly, and the rails leading off to the left, beyond the frog, which is the area between the two circles, are correctly powered, using external switching, and the original link has been removed. This should be true, otherwise no locos would run through it.

At the area within the pink circle, you can see that the two opposite polarity rails are in quite close proximity, and with DCC there is something like 16 volts potential difference between them. If the wheels on the pony truck (bogie) are too close together (that's their Back to Back) the rear of the wheel could be pulled over by the check rail at the top, and get close to, or touch, the other rail, resulting in the possibility that the current could arc across the gap, causing a short circuit. 

There is a faint chance that something similar could happen within the green circle, if the driving wheel's tyre could bridge the gap between the rails there, but this is unlikely unless running older stock with much wider (steamroller) wheels.

I am not familiar with this type of point, so I don't know what the electrical status of the two wing rails (those between the circles) is.  They appear to be metal, rather than the plastic of older insulated frog points, and it might be a good idea to check with a meter whether either of them is live, as that would also be a problem.

 

 

[latestarter]

48 minutes ago, Nick Holliday said:

 

 

 

What I was trying to say may be explained by the diagram, where I have coloured the rails either in blue or green to represent the polarity of the power supply.  I am assuming that the two links have been connected correctly, and the rails leading off to the left, beyond the frog, which is the area between the two circles, are correctly powered, using external switching, and the original link has been removed. This should be true, otherwise no locos would run through it.

At the area within the pink circle, you can see that the two opposite polarity rails are in quite close proximity, and with DCC there is something like 16 volts potential difference between them. If the wheels on the pony truck (bogie) are too close together (that's their Back to Back) the rear of the wheel could be pulled over by the check rail at the top, and get close to, or touch, the other rail, resulting in the possibility that the current could arc across the gap, causing a short circuit. 

There is a faint chance that something similar could happen within the green circle, if the driving wheel's tyre could bridge the gap between the rails there, but this is unlikely unless running older stock with much wider (steamroller) wheels.

I am not familiar with this type of point, so I don't know what the electrical status of the two wing rails (those between the circles) is.  They appear to be metal, rather than the plastic of older insulated frog points, and it might be a good idea to check with a meter whether either of them is live, as that would also be a problem.

 

 

Thanks very much for the explanation @Nick Holliday. it really helped clear up a lot of technical language that I wasn't previously familiar with. I am now very clear about what a 'frog' is - rather than just assuming it was the pointed plastic bit. I'll go and check the point and also the back-to-back on the pony truck (get me!)

The two wing rails are definitely metal, and possess a multi-meter (God knows why, I might just as well possess a Hadron Collider) and I'll check if they are live.

I am also going to see if I can dismantle the Ivatt to check that the pickups are positioned correctly around the wheels. More importantly, I'm also going to see if I can get it back in one piece!

Edited November 8, 2021 by latestarter

[latestarter]

@Nick Holliday I checked the track with a multimeter. I was getting some sort of reading on the track generally, all over. On those points, I was getting movement on either rail before and after the frog, and on the point clips. No movement (no number other than 0.00) on either of the 2 wing rails (which are metal).

The Ivatt is stopping dead precisely when the front pony truck wheels touch the part of the rail where the clips are fitted, if not running at well over half speed on the controller. I tried it with a Horny Tornado 60163 at a dead slow crawl at it passed over those points very smoothly. I even managed to (accidentally) couple the Ivatt to the back of the Tornado and it pulled it across with no effort.

[rogerdee]

Try removing the clips then try the loco over the point. The wheels on the front might not like the clips if they have a larger flange on them. Some models have a separate set of wheels more of a scale size with smaller flanges.

[latestarter]

10 minutes ago, rogerdee said:

Try removing the clips then try the loco over the point. The wheels on the front might not like the clips if they have a larger flange on them. Some models have a separate set of wheels more of a scale size with smaller flanges.

I thought I had posted here, to say that I tried it without the clips yesterday. But I must have omitted it.

 

The result was the Ivatt stopped just after the frog. The other locos ran across the point really smoothly. Which begs the question; what are the clips for, given there is still power without them fitted? I'll have a double check tomorrow and come back.

[dave55uk]

On 08/11/2021 at 17:16, latestarter said:

I might just as well possess a Hadron Collider

This made me laugh.

[dave55uk]

23 minutes ago, latestarter said:

Which begs the question; what are the clips for

I guess Hornby use these clips to carry the power [see an earlier diagram] to both routes from the point.

Whereas, AFAIK, most people use droppers [down to the power bus] after the points and not reply on those clips.