R30044 Class 37 Network Rail jerky running at slow speed

[David J Oldbury]

I'm having problems with a recent purchase of this engine.

At slow shunting speeds the unit is very jerky both forward and reverse.

I've run the engine in on a rolling road for a couple of hours each way without success.

I've changed the decoder from a Laise to a DCC Concepts Zen 218 V12 Black but still experience jerky slow speed performance.

Could anyone please offer any advice to resolve this problem. It would be much appreciated!

[Jupiter 1707822591]

I cannot see any CV on the zen that will improve slow running.

Check that a rf capacitor is connected across the motor .snip it out if so. .

If no improvement ..ring / email DCC concepts ask there tech team .

[David J Oldbury]

Many thanks for your advice, I did however remove rf capacitor prior to installing the decoders but this had not improved the slow running.

I'm reluctant to strip down the gearbox assembly on the power bogie at this stage given that the model is just "out of the box".

[96RAF]

Turn off BEMF for a start then maybe look at the Zen manual for any CVs that cater for PID motor characteristics.

[rpjallan]

Have you checked that all the pickups are contacting the wheels all the time?

[Jupiter 1707822591]

Many thanks for your advice, I did however remove rf capacitor prior to installing the decoders but this had not improved the slow running.

I'm reluctant to strip down the gearbox assembly on the power bogie at this stage given that the model is just "out of the box".

Are you able to fit a blanking plate to check running on DC only .If you have not already done so .

You could contact DCC concepts tech team for advice .

Bemf seldom causes this problem but worth turning off to eliminate .

Nothing in the decoder manual to help that I can see .(plenty of options for flashing lights ).

Mod note - did you use the blue button to reply and find you were stuck in the quote box meaning your reply is lost in the original post. I have made it bold to stand out.

A better method is to use the three dot context menu and select quoted reply then you can reply in the clear space. As you can see now even I am stuck in the quote box just trying to add a note in Edit.

[David J Oldbury]

Turn off BEMF for a start then maybe look at the Zen manual for any CVs that cater for PID motor characteristics.

Many thanks for your advice, I disabled the BEMF via JMRI Decoder Pro as you suggested and ran a test. This unfortunately did not solve the problem, however I checked CV150 which indicated a value of 6. Reducing this to a value of 1 did reduce the stuttering quite a lot but not entirely.

 

 

One thing of note though was the gear train to the powered bogie sounds pretty rough when running despite the model being "run in " for a couple of hours.

 

 

Cant help but think that Hornby have cheapened their drives to such an extent that I would not consider buying their units in future. Bachmann in my view are far superior certainly from an engineering standpoint

[David J Oldbury]

Have you checked that all the pickups are contacting the wheels all the time?

 

 

Yes thanks for pointing that out! I've checked the power bogie and the contacts are fine. One contact arm on the rear bogie pick up was adrift which I have now rectified

[David J Oldbury]

No, that's a good suggestion, many thanks. I'll try that on a DC test track at the weekend. If their is no difference it would suggest the the gear train is at fault

[Going Spare]

Your comments about the standard of Hornby's engineering against Bachmann's in respect of the class 37 need to take account of Hornby's model being in their budget Railroad range and priced under £100 RRP whereas Bachmann's is £245 RRP.

[Fishmanoz]

There’s a clue in your CV150 adjustment. I don’t have access to the manual to see what the adjustment is for, can you let us know please?

I’m assuming it’s not BEMF as you mention it separately. Is it part of a PID adjustment? This possibility was mentioned above.

To explain PID, it is a method of controlling overshoot or undershoot as the loco speed approaches a new setting sent to it from your adjusting the desired speed on the controller. If it is overshooting, it means it adjusts to the new speed very quickly but shoots past then quickly goes the other way, shooting past again but by less than the first time. In an electronics analogy, think a ringing tuned circuit. And mechanically, it’s jerky running exactly as you’ve seen. If it’s undershooting, it means it takes longer than necessary to get to the new speed.

Explaining further, the P is the first order effect, the I the second order and the D, if present, the third order. Consequently, you first adjust the P to minimum jerkiness, then the I similarly, then the D. Your decoder manual will tell you the related CVs if your decoder has this capability. Lots of adjustments necessary so, if you get in a mess doing them, just write 8 to CV8 to reset the decoder and start again from scratch.

Hornby uses it in their TTS range. They have two motor algorithms for a start in CV150 (values of 0 and 1 only), then P and I adjustments for each algorithm across CVs 151-154.

If you want to learn more, google PID control.

PS. Note in this reply I have avoided the blue button and 3 dots so as not to unnecessarily repeat any previous posts and used the text box and green Post Reply button at the bottom of the page.

[David J Oldbury]

Further to your suggestion I replaced the decoder with the DC blanking plate and ran the engine under DC on a test track.

The engine stuttered badly at slow speed (3v) which suggests that under DCC the stutter may not be directly attributable to the decoder CV's configuration.

Tempted to obtain a replacement power bogie and test it against the original!

[David J Oldbury]

Further to your suggestion I replaced the decoder with the DC blanking plate and ran the engine under DC on a test track.

The engine stuttered badly at slow speed (3v) which suggests that under DCC the stutter may not be directly attributable to the decoder CV's configuration.

Tempted to obtain a replacement power bogie and test it against the original!

[David J Oldbury]

Many thanks for your reply and your comprehensive summary of PID, the concept of which I was completely unfamiliar with.

To clarify, I changed the value of CV150 via Decoder Pro from 6 to a value of 1.

I rechecked this again today and found the value had remained unchanged at 6

I've checked through the ZEN manual and found that CV149 through to CV255 are not user adjustable, so this was a bit of a red herring on my part!

I replaced the decoder with the DC blanking plate and ran it on a DC test track and found the engine stuttered badly at slow speed (3v) which as I have just posted tends to suggest more of a mechanical issue rather than CV configurations

[Jupiter 1707822591]

Many thanks for your reply and your comprehensive summary of PID, the concept of which I was completely unfamiliar with.

To clarify, I changed the value of CV150 via Decoder Pro from 6 to a value of 1.

I rechecked this again today and found the value had remained unchanged at 6

I've checked through the ZEN manual and found that CV149 through to CV255 are not user adjustable, so this was a bit of a red herring on my part!

I replaced the decoder with the DC blanking plate and ran it on a DC test track and found the engine stuttered badly at slow speed (3v) which as I have just posted tends to suggest more of a mechanical issue rather than CV configurations

Then I would be enquiring about a replacement if possible.

Thought CV 150 was incorrect .I cannot find any reference to it in zen manuals that are usable.