Are some locos just not meant to run on certain layouts?

[Popsicle49]

My wife is a gardener and takes the view that some plants just aren't meant to grow in your garden; I'm wondering whether her philosophy can hold true on a railway layout?  I have a stretch of n gauge analogue track about 2' 6" long with three sets of points over which a variety of loco types (from a variety of makers) from saddle tank to A2 all pass happily with no drop-off in speed.  A Dapol A4 (recently serviced by DCC Supplies and therefore very healthy) however, stutters on all three points yet trundles happily and smoothly round the rest of the oval at all speeds passing a couple more sets of points freely.  The track is squeaky clean as are the relevant wheels.  My instinct is to take my wife's view and find the loco a new home, I can't think of anything else to do.  Does anybody else have similar experiences or observations to make?

TIA Popsicle49 

[fozzy280472]

I actually believe this is true that some locos are just a PITA , I have a new Hornby class 56 and it is an absolute nightmare for derailing , stalling , uncoupling etc whilst my other Hornby , Bachmann ,Dapol and Heljan locos have no problems.

I can't bring myself to get rid of it though as its such a nice model,unfortunately its become a bit of a depot queen !!!

I have lost count the amount of times I have had it apart for checking....suppose its just one of those things.

Cheers Paul.

[RAF96]

I have Railroad Class 56 converted to DCC that runs fine on the rolling road but wont move on track. Its the one with pickups on both sides of the dummy bogie but only one side of the motor bogie, the other side has 3 x traction tyres. Not exactly engineered to work at all.

[Happy Hippo]

I've had a similar problem with an N gauge loco..

 

The problem was insufficient back to back on the wheel sets.

 

As it went through points, it was trying to short out on the back of the point blades.

[Crosland]

Insulfrog or electrofrog points?

 

What track was it tested om when serviced?

 

It doesn't matter how clean the track is if bits of it are uneven or unpowered or if the loco pickups are not working well or if the back to back is not correct.

 

Andrew

[Popsicle49]

Thanks for replies,

 

Insulfrog or electrofrog points?

 

What track was it tested om when serviced?

 

It doesn't matter how clean the track is if bits of it are uneven or unpowered or if the loco pickups are not working well or if the back to back is not correct.

 

Andrew

Hi Andrew, insulfrog and as far as the test track goes it was at DCC Supplies who are official Dapol repair agents so I don't know.

The area of track concerned isn't a prob for my other locos even a saddle-tank is fine.  BTW what is meant by 'back to back'?

Thanks for your reply

Popsicle49

[topsy11]

Does the running improve at all after you've been running the loco for a little bit.

 

I've got a Hornby model that doesn't like a set of points on my layout either but after 5 mins or so of running, with a little help over the troublesome points, it runs lovely over all the track.

 

Abit like your problem, there's no reason for it to stutter on the said set of points but it does. 

 

If it does cause continuous trouble then I'd be inclined to move it on myself.

[Kenton]

 

or if the loco pickups are not working well

Or even that there are insufficient pickups!

 

N guage is much less tolerant of track laying then OO. Insulfrog points have a proportionally greater dead spot. Place points in a row or sequence and you increase the chances of the wheels with the working pickup stuttering on the dead spots.

 

Some locos have poor(er) motor design or no fly wheel weight and simply cannot cope as well with an intermittent supply.

 

Just because the rail tops look clean - they probably are not (oil from passing locos, oils from fingers, atmosphere) N gauge points are notorious for poor electrical contact, unless they have been wired accordingly the switch rail will depend on contact with the stock rail for continuity - that contact point is often not cleaned very well so is more dependant on the back to back (distance between the backs of the wheels on an axle) to force them together.

 

Different plants require different soil types, light, humidity, moisture, climate ...

 

I am a long way from your wife's theory being proven.

[F-UnitMad]

Thanks for replies,

 

 

Hi Andrew, insulfrog and as far as the test track goes it was at DCC Supplies who are official Dapol repair agents so I don't know.

The area of track concerned isn't a prob for my other locos even a saddle-tank is fine.  BTW what is meant by 'back to back'?

Thanks for your reply

Popsicle49

"Back-to-back" is the measurement between the inside faces of a pair of wheels on an axle. As I don't work in N I don't know what that measurement should be, but it's important as if it's wrong it badly affects the model going through pointwork - the flanges can bind on the frog and check rails. It may look like, or actually cause, stalling, but the problem is not the loco pick-ups or how clean the track is.

Run the loco as slow as possible, get down close and look at what the wheels do as it tries to go through the points. Do they try to lift over the track, for instance.

I'd take it back to DCC Supplies if possible and ask them to check the back-to-backs, as if adjustment is needed this might be tricky, & if the model is new, may come under warranty?

[newbryford]

Check the pickups - especially if wipers on the back of the wheels.

Some locos will run fine on straight track, but as a curve is encountered, the axles move sideways and lose contact with the wiper pickups on the back of the wheels.

Conversely, some locos will run well on curves and be cr*p on straight track. Not unknown for a loco to work well when travelling clockwise and rubbish when anticlockwise round a curve.

 

Cheers,

Mick

[DCB]

Back to back is the distance between the backs of the wheels, this is around 14.5 mm in 00 gauge although I use 14.25 mm .  This compares with the gauge, the distance between rails at 16.5mm.   If the back to back is too tight the backs of the wheels can bind on the point blades or check rails, causing shorts with live frog points.  If the back to back s too wide the flanges can bind against the the point bade of frogs.   A related problem is pickups often don't make proper contact when the wheel is deflected sideways to the maximum if the back to back is too wide.

Two other possibilities, the pick up is from the inside corners of the track so wiping a track cleaner flat across the track may not clean the contact area, and sometimes the weight of a loco on a point blade can push the blade down and push the contact on the blade away from the rail,  Does the A4 have tender pickups?   All sorts of things can cause uneven running, I had a displaced layshaft fouling the backs of the driving wheels on a Q1 on certain curves which took ages to locate.

[Popsicle49]

Much food for thought thanks, boy, are some of you guys  clever!  Regarding Kenton's point about the original garden analogy, my wife is a much more methodical and sensible gardener than I am railway modeller; she does her homework, knows her plants and buys only what our garden conditions can sustain bearing in mind position, pests etc etc. Despite that, the inexplicable still occasionally occurs and then the philosopher kicks in.  Depends how many challenges one wants to face. Layout problem-solving is fun up to a point (!) but I want to enjoy my trains too and watch the locos running round smoothly without getting stressed out because one of them doesn't run perfectly - It's a question of balance I guess. My track work is sound enough to have 99% of my locos working happily (surely that's a key consideration) and I've done everything reasonable to address the A4's peccadilloes. Somewhere there'll be an explanation but, being more artist than engineer, my resolve to get to the bottom of it is waning, you can't win every battle.  She'll no doubt run perfectly on someone else's layout. That other old gardeners' maxim about a garden never being finished is certainly true of model railways but that is fun; besides and it keeps us off the streets.

[34theletterbetweenB&D]

... My track work is sound enough to have 99% of my locos working happily (surely that's a key consideration) and I've done everything reasonable to address the A4's peccadilloes. Somewhere there'll be an explanation but, being more artist than engineer, my resolve to get to the bottom of it is waning...

What you don't know is exactly where the problem lies. It may be that the track is very marginal in some respect, and this particular mechanism is that little bit more sensitive to whatever shortcoming exists in the track. (As such it may be useful as a good test vehicle should you alter or develop the layout's trackwork.)

 

A typical scenario with ready made points and a model. Most ready made points have a slight upward bow, mostly induced by the curved rails. Something as simple as the A4 model of all the models you own having the least vertical flexibility for those parts of the chassis where pick occurs may be enough for it to momentarily have interuption of current collection, as the non-pick-up wheelsets while on the raised areas of the points lift all the current collecting wheels out of contact one side. The gap will be too small to see.

 

Here's something to observe, run the loco on the layout in darkness, observing the trouble spots. If you see sparks, it's short circuiting on the rails somewhere; if there are no sparks then most likely loss of contact between the pick up wheels and rail, on one side at least.

[Popsicle49]

What you don't know is exactly where the problem lies. It may be that the track is very marginal in some respect, and this particular mechanism is that little bit more sensitive to whatever shortcoming exists in the track. (As such it may be useful as a good test vehicle should you alter or develop the layout's trackwork.)

 

A typical scenario with ready made points and a model. Most ready made points have a slight upward bow, mostly induced by the curved rails. Something as simple as the A4 model of all the models you own having the least vertical flexibility for those parts of the chassis where pick occurs may be enough for it to momentarily have interuption of current collection, as the non-pick-up wheelsets while on the raised areas of the points lift all the current collecting wheels out of contact one side. The gap will be too small to see.

 

Here's something to observe, run the loco on the layout in darkness, observing the trouble spots. If you see sparks, it's short circuiting on the rails somewhere; if there are no sparks then most likely loss of contact between the pick up wheels and rail, on one side at least.

Thanks for this extremely interesting reply - I think your scenario, almost undoubtedly, is the most probable explanation.  I shall follow your advice about operating in the dark and, for me, it corroborates my view about accepting the original premise.  To solve this particular prob is not only technically beyond me but also I don't want to go ripping up track at this stage so the A4 will, for now, rest in the cabinet.  Much appreciate the detail.

[dasatcopthorne]

Popsicle49.

 

This doesn't sound like too much of a 'technical' problem to me.

 

In all my years of sorting problems such as you describe, it seems to me that there can only be two problems.

 

Dirty track or bad pickups.

 

When cleaning track, don't forget that often wheels don't ride on the tops of rails but the edges. So, clean the tops, yes but also clean the inside edges of the rails by using you track rubber (or whatever you use) at 45deg.

 

Test the loco and when it stalls, see if it rocks. Some locos don't have pickups on the centre drivers and it could be sitting on these and not picking up power.

 

Also, when it stalls try moving the loco side to side. This usually shows up any pickups that are not always in contact with the backs of the wheels.

 

Best of luck.

 

Dave

[RAF96]

Further to my post at #3 I have fitted some additional pickups to the motor bogie insulated wheels side and shimmed up the wheel sets on that bogie to eliminate a lot of the side slop, which was allowing the gears to almost come out of mesh. I could have used shim washers on the axles but plasti-card was just as easy.

Investigation had shown that pushing the wheels side to side also affected an AVO check for continuity betwixt rails and motor, hence the plastic shim.

The extra pickups were old steam loco ones modified and soldered to a thick copper link wire that mounted them to the motor bogie side frame. The link wire then has a flexi-wire soldered to it fed back to the front bogie and hence to the decoder socket.

Result - it runs very smoothly on the RR but is still stutters on the main, but it will make a journey at last.

I have ordered up some Neo magnets to see if that will give it a bit more torque.