Hornby Tornado TTS Juddery at Low Speeds

[totontony]

HI,

i have a problem with my Hornby Tornado with TTS sound. It Judders at slow speeds and does not stop until around step 40. Have set CV08 to 08 without any improvement. Anyone any ideas on which CV's I could change to help with the problem.

Thanks in advance.

Totontony

[Deem]

I recently bought used Hornby Tornado which was converted to TTS by previous owner with Hornby R8108.

I cleaned the wheels and reset the decoder after that it worked fine. Before all that it used to Judders but after the above process it ran much better.

This may help you and it may not, always worth a try.

Regards

[Fishmanoz]

Standard solution for juddery TTS - change CV150 from 0 to 1. That will at least improve it. If not fully fixed, we can tell you the related CVs which can further fine tune. Or do a forum search on PID.

Mods or Tony, can you please add to the thread title “TTS Juddery at Low Speeds”. Good idea, Thanks, RDS

[totontony]

Hi,

Thanks to Fishmanoz for the info. Works ok after changing CV 150 from 0 to 1. I must be getting old because I had the same problem with a class 66 and cured it the same way and didn't realise that all TTS sound chips have the same CV's for the same purpose. Thanks again.

Cheers,

Totontony

[Fishmanoz]

not at all Tony, all part of the service.

[ff2nd]

Can you read CV7? That will tell you what version of firmware your chip is on. I believe Hornby have updated files for some locos that can cure things like this.

[Fishmanoz]

Given what we see here consistently as the problem (juddery at low speed) and what consistently fixes it (changing the motor algorithm by changing CV150 from 0 to 1), it’s pretty clear the default algorithm “under-damps” throttle response to speed changes. Or put another way - when the controller asks for a speed change, the throttle continues to increase speed for a short time beyond the new set speed, then over-corrects to get back to the new set speed and over-corrects again on the way back).

It would be interesting to know if a change to the default algorithm by making the CV150 default value 1 instead of 0 would make things better or worse. It would certainly eliminate virtually all of the problems reported here but may create more.

Rob, it would be worth suggesting to Hornby they take a look at which default value is better?

[ColinB]

I have many TTS decoders in various locos, it has got to be over 30 if not more. The only locos I have had to change CV150 to 1, have always been Bachmann locos. On all the other locos it works perfectly out of the box. The most important thing before you rush off changing CVs is does the loco run reliably under DC. I have many locos I have bought second hand where they judder at low speed on DC so of course when you add DCC the issue is probably going to get worse as the electronics tries to compensate. Many times I have found the motors although they work, don't work very well on low current. Of course you would not notice that on DC. On one loco I was fixing for someone else it juddered because someone had glued an axle gear back together when it split. No matter how good you are the addition of the glue will make that gear slightly thicker so causes issues. So as everyone says on this Forum test it on DC before you do anything, that is also another reason to NEVER hard wire a decoder.

[96RAF]

The problem is Fishy even if the production firmware was adjusted to default CV150 to value 1 this would have to be on a case by case basis for each loco and motor type (e.g. FS can have a 3 or 5 pole motor), and even then existing stock wouldn’t benefit from the change so I doubt it will happen, although I have brought it to Hornby’s attention.

[ColinB]

Did you not read my post 96RAF. Perhaps I ought to reiterate "ON MOST OF MY LOCOS WITH TTS FITTED I HAVE NO NEED TO ADJUST CV150". Now I don't know if you lot are running a dodgy set of motors, I have not seen the issue. Believe me I would have noticed it, as I saw it immediately of both my Hornby and Bachmann class 66s. I have noticed on most old Hornby locos, the loco driven types the motors draw a lot more power and are not as smooth as new out the box. Generally if the loco is a bit hesitant on DC I change the motor. It is amazing on so many of Hornby locos where they use the same motor and give it a different price (very often a lot lower if it is an obscure one). So for once I agree with Hornby.

[96RAF]

Yes I did read it Colin and that is why in my reply aimed at Fishy I said any change would have to be loco and motor specific- therefore not a blanket adjustment to the decoder code.

[rvinalaff]

The other thing to consider is that different controllers have different idioscyncrasies where one would dislike a Hattons decoder or anther would dislike a Zen or a Hornby chip and so on.....

[Fishmanoz]

Might I just summarise this topic - OP advised TTS juddery at low speed, asked what CVs to adjust. I advised CV150 to 1 and OP advised thanks, loco now much improved.

We know there are many other factors for juddery but, over the years for TTS, this has been a major cause of problems. In the early days, it seemed every second or third question asked was this one. Other common problems were early reliability, the firmware bug which meant they would only run placed one way on the track and lately it’s availability.

Even so, look back over the previous 4 pages of topics in this forum and there is one on low speed juddery on each of the pages and each is a Hornby loco. You will also find one of my longer PID explanations there at https://uk.hornby.com/community/forum/r30044-class-37-network-rail-jerky-running-at-slow-speed-326599?ccm_paging_p=1&ccm_order_by=&ccm_order_by_direction=

Rob, you are perfectly correct, whether this problem will arise or not starts with the motor and chassis configuration, then relates to specifics of individual locos within that configuration. I just thought that, given the prevalence, it may be worth investigating further. It might even be interesting to ask why the designers included the feature given it is not a feature of the basic 8249.

Colin, given the history, you’ve been fortunate not to see the problem more often. Although it’s also true that the routine maintenance you do before fitting DCC can be a factor in the problem not arising in the first place, given it’s nature. Then it’s also true that Bachmann seems to have had their fair share of the problem with at least their earlier decoders having CV53/54 adjustments for a similar problem.

[Yelrow]

I have the same loco. Never had any problem with it. I have its brother that is not sound, and that did judder, until i adjusted cv