Ordinary Express Series 165 "Monterey Color"

[Lawrence]

Hi Guys, for some reason my Tomix 165 has started stalling across points (all Kato) in either direction, unless I whack the speed up.  Could this be a BtB problem and do Tomix or Kato do BtB gauges?

Thanks in advance for any help

[keitaro]

Hi Guys, for some reason my Tomix 165 has started stalling across points (all Kato) in either direction, unless I whack the speed up.  Could this be a BtB problem and do Tomix or Kato do BtB gauges?

Thanks in advance for any help

 

So it use to run fine?

 

Do all other models run fine on these points?

 

Does it run fine at other track areas and only on points?

 

If you answered yes to the above it sounds like one of the bogies is not picking up power or something is causing a short.

 

Get the + and - wires from your controller and place it at say 30% not too fast.

 

Place the model upside down and test contact on all the non traction wheels 1 at a time to make sure they are all getting contact.

 

Also if you have a similar tomix model compare the pickups to make sure they are not, loose the springs are there and the wheels are properly mounted on the grooves they go in.

 

Also clean the switchs even the grooves.

[The_Ghan]

keitaro offers good advice here, particularly the last point.  If the grooves are dirty then the wheels might be lifing off the track.  I'd also be checking the wheels to make sure they are clean.

 

Cheers

 

The_Ghan

[Lawrence]

Hi Guys, for some reason my Tomix 165 has started stalling across points (all Kato) in either direction, unless I whack the speed up.  Could this be a BtB problem and do Tomix or Kato do BtB gauges?

Thanks in advance for any help

 

So it use to run fine?

Yes

Do all other models run fine on these points?

Yes

Does it run fine at other track areas and only on points?

Yes

If you answered yes to the above it sounds like one of the bogies is not picking up power or something is causing a short.

 

Get the + and - wires from your controller and place it at say 30% not too fast.

 

Place the model upside down and test contact on all the non traction wheels 1 at a time to make sure they are all getting contact.

 

Also if you have a similar tomix model compare the pickups to make sure they are not, loose the springs are there and the wheels are properly mounted on the grooves they go in.

Will have a look at that though I don't think I have anything to compare it with

Also clean the switchs even the grooves.

Do you mean at the frogs? I have cleaned them out with isopropyl on a small stiff brush

 

Thanks for your help, I take it you don't think it is the back to backs then?

[The_Ghan]

Hi Lawrence,

 

From your original message it seems that momentum is carrying the loco across the points at high speed.  This is typically a circuitry problem either in the track, between the track and the loco, or in the loco itself.  You must explore all three possibilities.  It seems you've thoroughly cleaned the track, but have you tested it?  How many sets of points do you have?  As a sanity check, I'd be checking the points with a multimeter or, at least, one of those circuit probes that you can buy at an automotive shop to make sure every part of the points is properly electrified.

 

I don't know what BtB's are, so I can't help you there.

 

From your latest reply I'd be looking at testing the circuitry on the loco with probes connected to your controller.  As keitaro suggested, set the power low and probe each pair of wheels in turn - the motor should spin each time.  Test wheels fitted with the rubber traction tyres too as they can still pick up power through the flange.

 

Dirty wheel sets can also cause this problem.  Make sure they are thoroughly clean.

 

Hope that helps.

 

Cheers

 

The_Ghan

[Lawrence]

Hi Ghan

 

thanks for that, back to back is the distance between the back of the wheels on an axle, there is usually a standard to adhere to, maybe it is a British modelling thing 

 

Wheels are clean, as is the track, have carried out voltage checks all round the loop and it is all pretty goo I must say, It has to be the loco and when I get some time I will have a look at keitaros' suggestion

[The_Ghan]

Good work Lawrence,

 

I think you're going to find it's a pickup problem.  Here's hoping it's an easy one to fix.

 

Cheers

 

The_Ghan

[KenS]

thanks for that, back to back is the distance between the back of the wheels on an axle, there is usually a standard to adhere to, maybe it is a British modelling thing 

 

There are standards for both the wheel "back to back" separation (NMRA S-4.2) and the opening at the point rails (NMRA S-3.2) which is the one place on a Kato switch where a BtB issue could cause a short, since the open point rail will always be opposite in polarity to the wheel backing up against it. I don't know that the Japanese manufacturers follow these in particular, but it's a useful pair of dimensions.

 

Per those, wheel BtB spacing should be 7.65 +0.05 / -0.10 mm. Point rail front-to-back spacing should be 7.98 +/- 0.05mm.  Note that you need to add a bit to the back-to-back number to compare the two, since  the wheel has a flange that keeps its back away from the rail its on. Flange width should be 0.51 +/-0.05mm (also in S-4.2). This means that the back of a wheel should have at least (7.55+0.46=8.01) - 7.93 = 0.08mm of clearance, and probably more, since the curve of the wheels isn't accounted for there.

 

On one of my Kato switches, the "front to back" spacing of the point rails is about 6.86mm. My calipers aren't really designed to measure a front-to-back dimension like this, so I had to line them by eye and that may be off a hair, but not much. That puts the point rail further from the other rail, making a short less likely even if the wheelset was out of spec.

 

I don't have much Tomix equipment, but one engine had a wheel BtB spacing of 7.37mm, which means those wheels were slightly too close together. But the clearance is still probably around (7.37 + 0.46) - 6.86 = 0.97mm on my sample.

 

I'm guessing the Japanese manufacturers don't follow the NMRA standard, but instead design on the safe side of it, making wheels closer together (avoiding problems with slightly too-narrow track), and point rails further from the running rail (avoiding BtB shorts). That makes a BtB short unlikely, particularly one occurring on multiple switches.

 

Which is not to say it's impossible.  Checking the wheel BtB spacing (and looking at the switches to see if any of the point rails look bent) seems worthwhile. But as The_Ghan points out, the symptom sounds more like a power problem. Most likely, as keitaro noted, is a pickup problem on the bogie. 

 

It's possible however that the point rails aren't being properly powered because they're dirty (on the underside) or bent, but that doesn't seem likely for multiple switches.

 

One other possibility: you didn't say what kind of Kato switches. If these are #4, one of the set screws on the underside can be set to make the frog (and the point rails attached to it) unpowered. This would cause problems with trains using single-truck pickup (or really short ones). You can't do that with a #6 though; the frogs/points on those are always powered.

[Lawrence]

Ken - fantastic, thank you very much.  One thing I do know is that the screws are set correctly.  As this is something that has only recently happened I should think it is the loco, either the pickups or BtB's.

Thanks for all the help