[double00]

I am most baffled as all the track concerned has been carefully checked for faults.
The curves envolved are Hornby R607 double curves. The locomotives (Diesel) approaches the curve in question and negotiates at speed set by the controllers control knob. That is until the loco reaches the fourth curve, when the speed of the loco reduces to a slow crawl - picking up speed again on reaching the end of this curve and onto the straight rail. No alteration is made to the controllers variable control knob at anytime the loco is travelling on the layout.
Please, any suggestions. Reading voltage accross the two rails, shows no variation in voltage drop anywhere on the layout and that includes the curve in question.

 

[Dennis David]

I would check a couple things.

1. Dirty track
2. Binding wheels due to either the track or wheels being out of gauge.

 

[LisaP4]

I'd say the problem is a fishplate not conducting power properly, the voltage is getting through but not enough current for the loco. Best fix would be to solder the joins, or solder a jumper wire across the joins so that you are not relying solely on the fishplate to carry the power. Alternatively you could pull the track apart and give the fishplate a squeaze with pliers to flatten it a little and make a tighter joint.

 

[Dennis David]

Here's a question, if checking voltage is not enough how do you check to see if you have sufficient current?

 

[LisaP4]

Check the voltage first, if it's not one it's the other.

 

[John Webb]

Can I suggest you have a spare track power clip ready to hand, and connect your voltmeter/multimeter to this so that you can actually measure the voltage on the track when the loco is on that particular piece? This avoids having to arrange leads over or under the track in such a way that they do not foul the train as it passes over the measuring point when carrying out 'live' measurements.

Regards,

John Webb

 

[double00]

The voltage appears to read the same on all parts of the oval circuit.

 

[Rail-Rider]

It's really quite difficult diagnosing remotely, in that there are so many possibilities that it becomes an enormous job to try to list them all and especial in the correct order!
All the advice given up there is good.

Let me add a few thoughts.
You say you have checked voltage across the rails all the way round the oval, using a meter, and it's good. A problem that can occur here is that there is no train (weight) on the track when you do this. It's possible that a bad contact only occurs when the weighty loco rolls on to the problematic curve due to slight warpage in the track or unevenness of the underlying surface. As the train rolls onto the problem section, the weight transfer moves the section ever so slightly and a bad fishplate contact could be altered just enough that the current supply and speed is affected. So DO check for flatness and firmness of all the track sections.

Another little check - when the loco is actually ON the bad section and running slow, using a screwdriver or similar, press quite hard on the adjoining fish plates, forcing them into contact with the rails. If any improvement occurs you can be sure that's where the problem lies.

Another trick - while the loco is running slowly on the bad section, bridge each adjoining fishplate with a short length of wire. You'll need two hands to accomplish this. Press-gang a friend into checking another at the same time. If no friends, you could cobble up a paper clip for each one or perhaps a bulldog clip or even hairclips! Best of all would be as Lisa suggested, to solder a short wire jumper across the adjoining rail ends.

Finally, and I should have said this first - take out the annoying curve and swap its position with one of the other curves. A bit of trial and error may well point you towards whether the cause is warped or dirty track or bad fishplate connections.

I hope something here helps

 

[Rail-Rider]

I just remembered something important that was not quite coming to the surface earlier.

You really need to run a different loco, round this oval to see if the same thing occurs. If it does occur with other(s) then we can be fairly sure the problem is not in the loco itself, which, while seemingly unlikely, is possible and needs checking to be sure.

 

[double00]

I have tried to run the Heljan class 47 on its own, and no noticeable reduced speed at the curve in question. Hook on two Hornby InterCity coaches to the Heljan class 47 diesel locomotive, and the fault returns - if this be the case, why the fault?
The fishplates at either ends of the concerned curve, show the 11.8volts on the meter - ie a reading taken between said curve and both adjacent curve/straight track.

 

[double00]

An after thought led me to couple a Fleischmann class Greyhound diesel locomotive to the questionable two Hornby InterCity coaches - running this setup over the said curve, showed no slow down of the Greyhound/Hornby InterCity coaches when running over the questionable curve.
Now the question? what causes the Heljan class 47 to slow down when pulling the two Hornby InterCity coaches? a good question!

 

[LisaP4]

something iffy with the couplings?

 

[double00]

LisaP4, what do you suggest? that I check for? Thanks for your interest shown in my fault and also thanks to all who have replied with their suggestions.

 

[Gary]

Just something to check out.

Are all the Hornby curves used of Chinese origin?

If you are mixing track of European and Chinese origin then the steel used has different qualities and conductivity properties. A year or two ago I noticed something and spent some time comparing things. Locos from all manufacturers were consistently running slightly slower on some track sections than others where I mixed track from different companies and introduced secondhand track. When all track had steel from the same source it provided a consistent performance. It is not really advisable to mix track with steel from different sources as if you do you will get power fluctuations around your circuit.

Another reason for not economising on secondhand track.

Happy modelling
Gary

 

[Rail-Rider]

DoubleOO
Good work!
You have clearly established that the Heljan will run just fine on its own and also that the Fleischmann has no bother either - even with the coaches. Therefore there is nothing inherently wrong with the rails in that bothersome curve.

That completely eliminates the variable steel conductivity theory, which I wouldn't accept as plausible anyway, unless it were issued in an official Hornby statement and I would most seriously doubt that.

I would like you to run the Heljan loco, together with the coaches, but reverse the loco end for end, to see if the misbehaviour remains the same. Also to try running the train over the curve, but travelling in the opposite direction, ie in reverse.

You really must check that the track is absolutely flat, not warped in any way and not kinked - the loco could be losing pick up contact due to the added weight of the coaches being just enough to tilt or move the track in some way, in which case the loco could lose rail contact intermittently with one or more of its wheels. Alternatively, there could be just enough track movement to reduce contact between rails and fishplate connecting them together. The first is much more likely, but the second is possible and even maybe both.

You need to swap that troublesome curve with another one and also to check if the troublesome curve REMAINS troublesome in a different location.

I feel sure that some combination of the above will identify and eliminate the problem.

As a last resort, one other possibility that I have encountered, although I am not familar with the internals of your loco, is that there could be a faulty wheel pickup strip inside it which, through some coincidental combination of forces, is losing contact when under load on that curve. This is unlikely but definitely worth checking out if nothing else works. Similarly a faint possibility that some loose strand of wire inside the loco is causing a partial electrical short, intermittently.

All problems of this nature are soluble - it's just a matter of methodical elimination

 

[Dennis David]

The key is being methodical.

 

[Gary]

QUOTE That completely eliminates the variable steel conductivity theory, which I wouldn't accept as plausible anyway, unless it were issued in an official Hornby statement and I would most seriously doubt that.

Why should Hornby have to issue a statement? I don't understand this comment?

Their track produced in the here and now is of consistent quality and offers consistent performance as far as I can tell.

Moving on...

It is the mixing of track from different eras and companies that can result in giving the running qualities that are being discussed here. As long as the track of one company and one era is being used then I would agree that this is not an issue in this case. When mixing track this effect is most noticable when running the old Tri-ang locomotives which have relatively poor pick up by todays standards, a motor that requires a relatively high draw, and poor rolling resistance.

Pop around to my house sometime Rail-Rider and I will give you a demonstration. double00 has indicated that the Heljan loco is affected when pulling a load. The pick up properties of different locomotives is variable as are the properties of motors. Manufacturing tolerance account for this. Adding coaches to a loco affects the draw required to haul the load and this could be a factor as it makes the difference more apparent. I take it the coaches don't have lights or a redundant light circuit? Some of the older Hornby Inter-City coaches had this fitted.

And it would be best to see if doubleOO is using a mixture of track before jumping to conclusions. Have you put the offending piece of track in a different position?

I would certainly agree with Rail-Rider that this should be done.

As well as the other suggestions made of course.

Happy modelling
Gary

 

[double00]

Again my thanks for further suggestions given.
Rail-Rider - Tried running Heljan+coaches in reverse, this showed no fault over the said curve. Running same, by switching Heljan loco in reverse position to end of the second coach and running this combination in a clockwise direction - no slow down fault sowed over this said curve.
Said curve has in the past been swapped over with another curve and said curve repositioned and placed in space vacated - replaced curve showed to have similar fault as to the said repositioned curve.
Joinning said curve to adjacent straight rail by use of electrical wire - showed no improvement in performance ie slow down on said curve remains. Heljan loco always speeds up on leaving said curve and on to straight track.

Gary - All curves, straight track are Peco ST nickle plated range and purchased as new 18 months ago. Points also bought 18 months ago are (5) Hornby and (2) Peco.
Said curve is not at or near any of the installed points.

Track has been checked for level, movement and kinking - nothing appears to show any deffects. Four curves at each end of the layout, show no sign of any faults but a gradual even circular bend.

Heljan loco class 47 has on its tow bogies - six wheels (two centre wheels are free movement, and can cause great difficulty to place on track).

 

[Gary]

QUOTE Said curve has in the past been swapped over with another curve and said curve repositioned and placed in space vacated - replaced curve showed to have similar fault as to the said repositioned curve.

So clearly something to do with that location on your layout. Have you tried swapping the sections around either side of the section of track under discussion?

Say 2 or 3 pieces of set track either side of the offending piece of set track.

To be honest it is not uncommon for locomotives to slow down in curves due to additional forces on the locomotive such as sideways drag of the flanges on the rails, and then speed up again on the straights. But you are saying that it is just one section of the four curved sections at one end where this is noticeable.

A mystery. If it was me I would do the above and see what happens.

Another thought though. Remove one section of track completely and make sure you have a good current all the way around the rest of the circuit when driving your loco over it. You might find that there is a break in the circuit somewhere.

Happy modelling
Gary

 

[double00]

On running again the Heljan class 47+ two coaches in reverse, it now shows that it slows down on the fourth curve at opposite end of the layout.
Far end - loco slows approaching fourth curve - speeds up along the stretch of straight track and again slows down approaching (previous) original fourth said curve - speeds up again, until reaching fourth curve, slows down making a complete circuit.
As in real times, a locomotives will slow down in speed approaching a bend on the line.