Hornby R3395TTS - Stuttering when driving slow

[MrWagner]

Hello,

I received a completely new Mallard (Hornby R3395TTS) a few days ago. You can't complain for the price. I don't know if the following problem is normal:

The locomotive starts to stutter when driving slowly or when it starts moving. Sometimes the locomotive stops for a moment and then jumps forward again. She moves in a slippery manner.

Could that be a DDC setting? Although I cannot imagine that it is due to too little oil.

Here are two three five Videos:

final 1:

final 2:

new:

old:

old:

Edit: digikeijs DR500 central, power supply is set to 15V.

Mod note - the links have been edited to make them valid. The original URL link text started -http the - is not a valid starting character.

user note: Thx for the hint :-)

[96RAF]

Those YT links are reporting as invalid.

If your controller supports changing CVs alter CV150 to value 1.

[MrWagner]

The YouTube links should actually work?

Motor Control was changed to 1. The locomotive now runs faster at the same level, but the problem does not change.

It has nothing to do with CV10 or CV29? At CV26 there is 6 default which probably means that DC and DCC mode are active at the same time? OK, for CV10 there is a hint in the manual for lower speed running. I will try that.

[ColinB]

I know it is not always that easy but have you thought of replacing the TTS decoder with a DC header and see if the fault disappears. At the moment you don't know if it is the loco or the decoder. I have a lot of A4s fitted with the TTS decoder and I must admit I have never noticed this sort of symptom and I would have as I notice it on all the Bachmann diesels I fit with Hornby decoders (fixed by setting CV150 = 1). It could be the decoder, but generally they either work or they don't. I did have one that was distorted in sound, but generally the only issue I have had with them is overheating and blowing up. It could be an issue with the gears that you only notice at low speed. One loco I fixed, the gear on the drive axle had split in the past and someone had glued it back together, but it made the tooth gap slightly bigger causing a jerking at low speed. It took me ages to find it.

[MrWagner]

I know it is not always that easy but have you thought of replacing the TTS decoder with a DC header and see if the fault disappears.

 

 

I hadn't thought of it now. Basically just pull out the 8 pin decoder and put in the DC header?

I also think that my expectations may be too high and that it is normal. On YouTube I did not see this behavior in all of the introduction and unboxing videos, although there were also other mallard models. They all moved very smoothly. Does the Hornby R3395TTS differ from other Mallard models in terms of components?

I noticed the following other things:

1. The rear wheel of the locomotive was not in contact with the rail and did not turn. Probably the sheet metal plate was tightened too much or the wrong way round.
2. The first and last axles of the tender do not turn because the contacts see too much tension. I still have no idea how to fix this without taking the tender apart? I had already tried to bend the contacts a little inwards with a screwdriver.
3. The housing of the locomotive is a little difficult to put on because the drive rods are in the way. That sounds worse than it is, but I have no idea whether this is normal.
4. The drive rods seem to drag on the front wheels when driving forward.

Maybe I'm just too fussy.

[RDS]

With those 'mechanical' problems I am not surprised it has issues at low speed. In my view, those problems need fixing before changes to any CV's are considered.

[MrWagner]

I'm considering sending the locomotive back and having a new one sent to me. Just to see how a new locomotive drives.

But I have the problem that I don't know if this is normal. Can someone with exactly this model confirm that they do not have these problems? See my new video. I cannot rule out 100% that it has something to do with my seating. The locomotive runs, no problem at normal and high speed. Only start and slow travel is a problem.

I have now also dismantled the tender, the contacts are bent incorrectly at the factory from my point of view. My opinion.

They were bent far too far back, too steep an angle and put too much pressure on the wheels. They should actually be like a spring and go with the wheels and not block them. At least that's what I think. Since the locomotive has contacts on 7 axles this is not a problem, but if 7 axles have contacts then all contacts should work. But didn't solve the problem either.

Edit: Something has changed. I now really suspect that it has something to do with the tender contacts.

From my point of view, I bent them better. Now the problem is less and all four wheels of the tender also turn. Before, the first and last axes were actually completely blocked and did not turn. I suspect that they have loosened every now and then and no longer dragged on the rail. The motor had to pull less weight and then start jerking to somehow regulate it. But it's all just speculation.

[96RAF]

Good clear fault diagnosis and reporting. Normally first time posters are raw beginners and we would not advise them to take such steps at dismantling and rectification as you have undertaken. We would recommend going for a replacement before tackling such dismantling. You are obviously a competent modeller. The fixed trailing bogie likely has unflanged wheels, which sit clear of the rail tops. This is to aid running on tight second radius curves. You have already noticed the valve gear and motion rods are fragile and easily distorted and can foul on other parts or the main drivers. These need to be very likely oiled to preclude wear and hence falling to bits later.

CV10 is back emf and TTS relies upon this to play the correct chuff or coast sounds when on or off load. CV29 covers many functions and is more easily understood using an online calculator. DC running is not recommended as it can lead to DC runaway if the DCC signal is lost for any reason and is best left off.

Once CV150 is set then there are addition trial and error CVs to alter the motor P & I characteristics. A bit of a black art.

I hope this helps, but please come back for more detailed help as required.

Edit - having watched the videos I can see the trailing bogie is below rail height and as stated it should stand clear of the rail tops. In the longer video there is a definite clicking noise coinciding with the jerks, so I would say initially the tender pickup wipers catching on the wheel spokes hence the distortion and possibly the valve gear and motion hanging up. Close observation would likely help including running on a rolling road.

[MrWagner]

I have attached two more videos of how the Mallard is running now.

I would also leave the videos on YouTube in case someone has similar problems. When you dismantle the wheels from the tenter you can bend the contacts straight with a pair of tweezers and then bend them in a curved manner. Like a spring. I have no idea why the contacts were so bent at the factory. At first totally straight and then a kink just before the end. With so much pressure that they blocked the wheel. But also so little freedom of movement that the contacts did not follow the wheel when entering a curve.

I will reset the decoder again to check again whether the current state is somehow false-positive. As it now looks like, the Mallard is going okay at first. It still has "micro stutters", but I think that's okay at this speed.

At the moment I would really blame it on the contacts from the tender + wheel blockade + sudden release of the wheels. But it could also be that the engine has run in or suddenly the oil has seized. I don't think so.

Edit: The trailing bogie is fixed in this model and does not follow the curve (even if it is shown differently in the manual). When you go from the curve to the straight, the wheels grind briefly, but I think it's relatively uncritical. Maybe that's the reason why the wheels didn't touch the rail at first.

"I would say initially the tender pickup wipers catching on the wheel spoke"

That was my assumption too, there is a strange noise sometimes from the tender. That they also grind somehow. I have to pay more attention to that.

[96RAF]

Something that had me fooled on a super-detailed Mallard was on tight curves the cab door was clicking as it caught on the tender on curves.

Ref the trailing bogie. Adjust it so it is clear of the rail tops, in case of shorting.

[Fishmanoz]

Adjustment of the additional CVs that go with CV150 set at either 0 or 1 is better than the black art Rob suggests. There’s a thread or two here that gives the methodology. Hopefully someone will find one of them for you.