hucknall byron Posted March 30, 2020 Share Posted March 30, 2020 Anybody have the technical reason why a loco sometimes needs a gentle push to start it? Is it something to do with the motor just not getting the electrical jolt it needs to start working or something else? As this must be one of the most common annoyances I just thought it was worth asking the question. Not strictly DCC related I know but relevant just the same. Link to post Share on other sites More sharing options...
RMweb Gold pheaton Posted March 30, 2020 RMweb Gold Share Posted March 30, 2020 15 minutes ago, hucknall byron said: Anybody have the technical reason why a loco sometimes needs a gentle push to start it? Is it something to do with the motor just not getting the electrical jolt it needs to start working or something else? As this must be one of the most common annoyances I just thought it was worth asking the question. Not strictly DCC related I know but relevant just the same. ive lost more hours than I care to mention trying to figure this out I've got a Bachmann peak that's notorious for it!!! Link to post Share on other sites More sharing options...
Luke Piewalker Posted March 30, 2020 Share Posted March 30, 2020 Stiction. The static friction is greater than the dynamic friction, so once things are moving the the friction reduces. DCC chips have various settings to give a motor an initial 'kick' to overcome it. That or dirty contacts. 1 Link to post Share on other sites More sharing options...
Nigelcliffe Posted March 30, 2020 Share Posted March 30, 2020 If its bad pickup, then its bad pickup - clean the wheels and pickups, and the track. If the pickups are OK, then its a mixture of crap motor and poor gearing in the mechanism. Fixes depend on the model in question, and how much effort willing to put into solving it. Decent models don't do either. Nigel 3 Link to post Share on other sites More sharing options...
hucknall byron Posted March 30, 2020 Author Share Posted March 30, 2020 Stiction. Yes that sounds very logical. I have spent a few hours this weekend cleaning the wheel sets and contacts on a Hornby 101 dmu that previously ran like a bag of nails and now its as smooth as silk right down to almost a crawl, but it refuses to start from stationary without a gentle push. It is dcc fitted so any suggestions for the CV setting to help with this problem would be greatly appreciated. Link to post Share on other sites More sharing options...
hucknall byron Posted March 30, 2020 Author Share Posted March 30, 2020 Nigel the motor is Hornbys 5 pole skew ( whatever that is). I don't know if that qualifies as crap? but I do know that there as possibly better ones out there as you say. Can this one be improved in some way? Link to post Share on other sites More sharing options...
34theletterbetweenB&D Posted March 30, 2020 Share Posted March 30, 2020 6 hours ago, hucknall byron said: ... it refuses to start from stationary without a gentle push. It is dcc fitted so any suggestions for the CV setting to help with this problem would be greatly appreciated. Assuming you have solidly reliable pick up, Increase CV2 until it starts every time would be the short answer. But it is not necessarily solely the mechanism that has a part in this, the decoder's performance is also potentially part of the problem. Some decoders are very weak at current supply at low output. I have literally never had this 'failure to start' problem using Lenz and Zimo decoders on a variety of mashima powered kit mechanisms and assorted RTR, but have seen plenty of others that are frankly 'flabby' when asked to start a mechanism by a smooth slow creep into dead slow movement. 1 Link to post Share on other sites More sharing options...
RobjUK Posted March 31, 2020 Share Posted March 31, 2020 20 hours ago, hucknall byron said: but it refuses to start from stationary without a gentle push. A dead winding or dry joint on the commutator motor could cause something like that - or just a very dirty commutator or contaminated brushes. 2 Link to post Share on other sites More sharing options...
WIMorrison Posted March 31, 2020 Share Posted March 31, 2020 IIRC there is a CV that will give higher starting voltage to overcome 'stiction' then once the motor is moving it falls back to the settings defined starting with CV2? I cant remember what CV it is, anyone else remember it? Link to post Share on other sites More sharing options...
RMweb Gold Dagworth Posted March 31, 2020 RMweb Gold Share Posted March 31, 2020 3 minutes ago, WIMorrison said: IIRC there is a CV that will give higher starting voltage to overcome 'stiction' then once the motor is moving it falls back to the settings defined starting with CV2? I cant remember what CV it is, anyone else remember it? CV 65 https://dccwiki.com/Kick_Start Andi Link to post Share on other sites More sharing options...
WIMorrison Posted March 31, 2020 Share Posted March 31, 2020 Thanks, seems that CV65 is for NCE in this article - in Zimo it is software subversion , though I note in NMRA Spec it shows as kickstart but that it is optional https://www.nmra.org/sites/default/files/standards/sandrp/pdf/s-9.2.2_decoder_cvs_2012.07.pdf Link to post Share on other sites More sharing options...
Nigelcliffe Posted March 31, 2020 Share Posted March 31, 2020 There are no standards for "kick start" etc.. Its all down to individual decoder maker (and its not needed by the really good ones anyway!). Some decoders are not as good as others (I'd call them poor or rubbish) - they work sort of OK, but then not as well as alternatives for about the same sums of money. Certain names come up again and again as excellent decoder makers, there is a reason for that. Nigel 1 Link to post Share on other sites More sharing options...
Pete the Elaner Posted March 31, 2020 Share Posted March 31, 2020 What decoder is in the affected loco please? Link to post Share on other sites More sharing options...
dasatcopthorne Posted March 31, 2020 Share Posted March 31, 2020 Is this a sound decoder or does to loco have any lights. If so, when it refuses to start, is the sound still active or are the lights on? Dave Link to post Share on other sites More sharing options...
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