DCC acceleration problem

[legin]

I can see that there are over 2000 posts on DCC topics, so I am sure this must have been covered somewhere but I am unable to find it by using the correct search words unfortunately.

I have 3 vintage locos,  Airfix x 2 and Mainline, an R2098c  2P, and a new Hornby Jinty, all converted professionally to DCC, and all except the Jinty and Mainline class 4 with Ringfield or Ringfield type motors.  Regrettably, I don't know what make of chip has been installed. ,  They are controlled by a Bachmann EZ controller. All will crawl at walking pace and up to a scale 10-12 mph or thereabouts. After that speed, 3 of them leap to approx. 25 mph instantaneously, whilst the 4th and 5th, including the JInty, will manage about 15 mph before taking off. No amount of fine control with the speed dial will stop this happening. My layout is relatively small and a scale speed of  about 18-20 mph  is about as fast as I want to go but I can't get it.. I have spoken with the fitter about this and his idea is that it may be the number of speed settings on the chip and these have been altered with a Dynamis from 28 to 128 but with no discernible difference. I doubt therefore if going down to 14 will make a difference either. I do not think that this is a problem with the controller since I have a Lenz fitted engine which accelerates smoothly throughout its range. I would be surprised also if it was to do with the locos since they have split chassis, can, and Ringfield motors between them.

Is this likely to be a CV setting problem? All of the locos are operating on the chip default settings at the moment. They are however accelerating smoothly between 0 and 10-15mph depending on the loco, and above 25 mph. I am pretty new to DCC and so any help would be gratefully received.

[Andymsa]

I would certainly think this is a cv setting issue, cv 2 crawl speed and cv 5&6 full/ half speed are what you need to adjust. If you want a max speed of 20 mph then adjust cv 5 until you get the result your after.

[Phil S]

Unfortunately not all decoders have cv5 ie the basic Hornby Decoder .... the most essential value to set when some youngsters are around thinking speed control is an on/off switch !   ... but they'll point out they added it via an option in Railmaster 8-)

Is there a also a possible misunderstanding here of the concept of 14 / 28 / 128 speed steps ??

They all share the same top and  bottom speeds ... and 'path'/curve in between ... but with 14 -discernable -steps, or 28- less-identifiable steps or 128-shoulndn't -be-detectable-steps   ..... first these need to generated by the controller.  For example the Maus 1 (Lenz for many makes when dcc started) and LGB MTS controllers only generated 14 speed steps.    I assume the Bachmann EZ offerS 28  ....    a Multimaus can be selected on a loco- by -loco basis to send 14,  28, or 128  steps   ....BUT does the knob being turned actually generate 28 or 128 or ? steps ... with software offering the rest ?   the DECODERS may offer 1024 internal speed steps ( the '14 speed step' LGB MTS  decoders did/do) .... but how well they can use this depends on how large your cv3 and cv4 values are ... the higher values allow more interpreted steps between 'set' speed values.

Alternatively  ... has the EZ commnd controller got a dodgy knob ???

[john dew]

I suggest getting the guy who fitted them to identify the chip manufacturer(s) for you......not an unreasonable request!

 

Alternatively if you can read Cvs on your layout you can do it yourself......Cv 8 shows the  Manufacturers ID#......Lenz is 99,TCS is 153 for example

 

Some TCS decoders and early DCC Concepts decoders are known to have a very noticeable speed lurch around the mid point of the speed curve. .......which is why I and others eventually replaced them....I standardised on Lenz (usual disclaimer)

[Andymsa]

18 minutes ago, john dew said:

I suggest getting the guy who fitted them to identify the chip manufacturer(s) for you......not an unreasonable request!

 

Alternatively if you can read Cvs on your layout you can do it yourself......Cv 8 shows the  Manufacturers ID#......Lenz is 99,TCS is 153 for example

 

Some TCS decoders and early DCC Concepts decoders are known to have a very noticeable speed lurch around the mid point of the speed curve. .......which is why I and others eventually replaced them....I standardised on Lenz (usual disclaimer)

 

Not forgetting digitrax has the lurch aswell

[john dew]

Ah I didnt know that....I lead such a sheltered life with Lenz!

 

But would you agree that the performance described by the OP is consistent with that type of speed lurch?

[Andymsa]

 

13 minutes ago, john dew said:

Ah I didnt know that....I lead such a sheltered life with Lenz!

 

But would you agree that the performance described by the OP is consistent with that type of speed lurch?

 

It could be possible, the lurch from my observations has been like a couple of speed steps have been missed. I think your reply to identify the decoders would be a first step to see if the lurch may be a factor

[SRman]

I'm not sure if you can do this with the basic command station, but if possible, try selecting 128 speed steps for the decoder control as well.

Edited March 22, 2019 by SRman

[Pete the Elaner]

You really need to start by identifying the decoders. They all have manufacturer & version ids. Some manufacturers do not use their version ids very usefully though.

I am not sure if the Bachmann EZ controller is capable of reading decoders in order to find this out.

 

[RedgateModels]

14 hours ago, legin said:

all converted professionally to DCC,

 

I always worry when I read this. Not saying the OP's are necessarily poor but you should see some of the rescue jobs I take in where the loco has been "professionally" fitted previously .....

 

The EZ Command does not even have a display, so can't read cvs

 

 

[legin]

Many thanks for the detailed replies, for which I am very grateful.

Boiling them down, it looks like I shall have to identify the make of decoders first. My EZ command, as has been said, does not allow reading of the decoders, so I shall have to get someone, maybe the model shop, to look at CV values, starting with CV2 and CVs 5&6, and probably  CV 3&4 as well. At least for some of the locos, setting CV5 to a max of 20 mph would stop them lurching to 25mph and so that would be a big improvement. The decoders themselves are, I hope, relatively new, having been fitted last year. And I am still rather dubious about it being the EZ command's fault, since my one Lenz fitted loco accelerates uniformly throughout the speed range.

[Sir TophamHatt]

As you've said, forget about the controller for now.

 

Where are you located?  If near a member here, I'm sure they'd be able to help you read and write new values if possible.

 

Ask the model shop/anyone to read the CV values from 2, 3, 4, 5, 6 to be on the safe side.

Also post the results here.

 

Also, don't get confused with the speed steps and mph.

I have no idea what speed step 28 is in mph on my layout.  I don't know what the maximum setting would be if you wanted 28 to be the top speed.

 

FYI: I only have 28 speed steps on my layout.  My controller/decoders do all three settings, but I choose 28 as 128 is a little too long for me (I don't need that fine motor control!) and 14 is a bit too short.

Edited March 22, 2019 by Sir TophamHatt

[Andymsa]

1 hour ago, legin said:

Many thanks for the detailed replies, for which I am very grateful.

Boiling them down, it looks like I shall have to identify the make of decoders first. My EZ command, as has been said, does not allow reading of the decoders, so I shall have to get someone, maybe the model shop, to look at CV values, starting with CV2 and CVs 5&6, and probably  CV 3&4 as well. At least for some of the locos, setting CV5 to a max of 20 mph would stop them lurching to 25mph and so that would be a big improvement. The decoders themselves are, I hope, relatively new, having been fitted last year. And I am still rather dubious about it being the EZ command's fault, since my one Lenz fitted loco accelerates uniformly throughout the speed range.

 

Something to bear in mind what ever setting cv5 is set for if you have one of the decoders that have the lurch it will still be there even as you say the max speed is 20mph, you will just be moving it. Identify first, I would if you can put in a decoder that does not have the lurch. Ones that seem ok to those who use them are ESU ZIMO LENZ

[legin]

Thanks Sir Topham . Unfortunately, I am in South Devon and so a long way from Leicester although I was just up the M1 in Sheffield until 5 years ago, which would have been doable. If I have understood this correctly, are we saying that 128 speed steps gives finer control than 28 or 14? The "trial" loco  I took to the model shop was changed from 28 to 128 but did not appear to make any difference. I will take the same engine in, one of the worst performers, and post the CV results. Andymsa -thanks also. Unfortunately, the chips are all hard wired in, including the new (ish) loco which is a Hornby railroad, so swapping them  without a lot of trouble and expense is not really an option. However, as I said above, my newest loco was DCC ready and I put a Lenz chip in which performs perfectly on its default setting. This is why I don't think the controller is the issue.

[Andymsa]

6 hours ago, legin said:

Thanks Sir Topham . Unfortunately, I am in South Devon and so a long way from Leicester although I was just up the M1 in Sheffield until 5 years ago, which would have been doable. If I have understood this correctly, are we saying that 128 speed steps gives finer control than 28 or 14? The "trial" loco  I took to the model shop was changed from 28 to 128 but did not appear to make any difference. I will take the same engine in, one of the worst performers, and post the CV results. Andymsa -thanks also. Unfortunately, the chips are all hard wired in, including the new (ish) loco which is a Hornby railroad, so swapping them  without a lot of trouble and expense is not really an option. However, as I said above, my newest loco was DCC ready and I put a Lenz chip in which performs perfectly on its default setting. This is why I don't think the controller is the issue.

 

Dont forget to let us know the make of the decoder as well. Considering your lenz chip is ok I'm really leaning towards the speed lurch issue.

[legin]

Will do.

[MikeHunter]

I'm having the opposite problem. I have a loco that seems to jump straight to full speed. I have an NCE Power Cab, and have tried resetting the decoder to factory settings, but it hasn't cured the problem. Either I'm doing something wrong with the programming, or I have a faulty decoder. As the loco is hard wired, want to triple check its not a progamming issue before changing the decoder. Its a Gaugemaster decoder. Any suggestions?

[tarifa]

Reading your OP it would appear to be a CV problem.  You say you cannot identify the decoders but most manufacturers use different colours, for example Bachmann are blue.  Have you tried resetting the decoders to default, this can be done by setting CV8 to 8.  To me your problem appears to be the speed curve is not linear, a reset should correct this.

[Andymsa]

28 minutes ago, MikeHunter said:

I'm having the opposite problem. I have a loco that seems to jump straight to full speed. I have an NCE Power Cab, and have tried resetting the decoder to factory settings, but it hasn't cured the problem. Either I'm doing something wrong with the programming, or I have a faulty decoder. As the loco is hard wired, want to triple check its not a progamming issue before changing the decoder. Its a Gaugemaster decoder. Any suggestions?

 

Sometimes doing a factory reset does not reset all the cv values. To be sure go through each relevant cv manually. Also what are the cv values before you did the reset. A good piece of kit to get is the ESU decoder tester for these kind of issues, but I'm thinking your have to take out the chip to isolate the issue. I always add my own sockets if space permits when hard wiring.

[Sir TophamHatt]

On 23 March 2019 at 14:05, legin said:

If I have understood this correctly, are we saying that 128 speed steps gives finer control than 28 or 14?

 

As far as I'm aware yes.

 

If you say each speed step has an acceleration rate of 4 units when using speed step 14, that means:

1 on the dial has 4 units of power applied to the motor.

2 on the dial will be 8.

3 on the dial will be 12.

... and so on.

 

If you increase the amount of steps (to 28), then the numbers change because there's more steps between 1 and 28:

1 on the dial will be 2 units of power applied to the motor.

2 on the dial will be 4.

3 on the dial will be 6.

... and so on.

 

So it gives a greater number of units applied to the motor.

You could think of "units of power" as MPH, and every time you increase the speed step another x MPH gets added to the current speed.

 

128 is massive.

I can't see how anyone could see the difference between 1 and 2 speed steps using such a large range.  Also means you have to turn the knob/wheel/whatever more to get to the top speed.

If you don't need a fast top speed, then CV numbers can be adjusted, which would give you the range of 128 in just 28 speed steps - although that's probably confusing things now :p

But I understand everyone is different.

Edited March 25, 2019 by Sir TophamHatt

[legin]

Many thanks again for the replies. Sorry I have not replied sooner but I had not managed to get hold of the guy who fitted all 8 decoders. It's between 8 months and a year and a half since he fitted them but thinks that they are all Hornby decoders. And because they all perform broadly in the same manner, I think his memory must be correct. Because I have an EZ controller, I cannot read or reset the CV values but the guy who fitted them has a Dynamis which can of course. They have not been altered from default.    Sir Topham -- thank you. I am with you on the speed steps and think that 28 should be perfectly ok for what I need, i.e. slow speeds, although at the moment, I am still getting the sudden acceleration jump from slow-about 10 mph on the worst locos-to 25 whichever of 28 or 128 steps are programmed.

[Nigelcliffe]

The EZ only outputs 28 step commands.  You can't change that on the EZ.

 

A decoder which is set to 28/128steps will respond to either packet format.  Its the DCC data packet from the command station which tells the loco whether to use 28 or 128 steps. 

 

 

- Nigel

 

[beejack]

3 hours ago, legin said:

Many thanks again for the replies. Sorry I have not replied sooner but I had not managed to get hold of the guy who fitted all 8 decoders. It's between 8 months and a year and a half since he fitted them but thinks that they are all Hornby decoders. And because they all perform broadly in the same manner, I think his memory must be correct. Because I have an EZ controller, I cannot read or reset the CV values but the guy who fitted them has a Dynamis which can of course. They have not been altered from default.    Sir Topham -- thank you. I am with you on the speed steps and think that 28 should be perfectly ok for what I need, i.e. slow speeds, although at the moment, I am still getting the sudden acceleration jump from slow-about 10 mph on the worst locos-to 25 whichever of 28 or 128 steps are programmed.

If they are Hornby then it most likely to be the R8249 and with this decoder you can only alter the following CVs 1, 3, 4, 10, 17, 18, 29 so there is no way to limit the top speed and the speed curve cannot be altered using CV's 2, 5 and 6

 

I would also suggest that if they are Hornby decoders it may be a compatibility issue between the decoders and the EZ Controller especially if the Lenz decoder works ok.

[NoelG]

If you can find out what decoders they are by querying CVs such as 8 etc. Some decoders use speed curves instead of CV6 to define the mid point voltage. A single CV29 bit usually turns this speed curve on or off (reverting back to CV2,6,5 curve). Also check the values for CV3 and CV4 are not too low. Another remote possibility is the decoders are in shunting mode which disables or reduces other speed effects. The main suspect seems a speed curve. Can you run them smoothly on DC (ie to verify chassis are free running)? Smooth Low speed running should normally be one of DCCs strong points. Good luck.

 

ps. I recommend lenz silver+ decoders or LokPilot for super smooth motor control. Zimo also excellent. Hornby decoders are not the best and often lack support for common motor control CVs. 

Edited March 27, 2019 by NoelG

[NoelG]

On 25/03/2019 at 10:18, MikeHunter said:

I'm having the opposite problem. I have a loco that seems to jump straight to full speed. I have an NCE Power Cab, and have tried resetting the decoder to factory settings, but it hasn't cured the problem. Either I'm doing something wrong with the programming, or I have a faulty decoder. As the loco is hard wired, want to triple check its not a progamming issue before changing the decoder. Its a Gaugemaster decoder. Any suggestions?

Sounds like speed curve settings too. ESU lokpilot and loksound chips have a self cabilbration mode for motor settings that involves the loco lunging forward at speed for 2 meters.