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Author Topic: Faulty New release 4F.  (Read 369 times)

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Offline Dave_cooper79

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Faulty New release 4F.
« on: July 06, 2017, 06:25:13 pm »
I've a new farish 4F that is running very juddery. It's dcc fitted but I think the issue looks to be mechanical, unless could the BEMF be causing issues with the poleless motor?

I've added a link to a video of its running on YouTube in case anyone has any experience with issues like this.

Many thanks in advance,

https://youtu.be/BFvHJXpDrAY

Offline ntpntpntp

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Re: Faulty New release 4F.
« Reply #1 on: July 06, 2017, 06:29:44 pm »
Well, in the vid it appears to be sticking at the same point of rotation in two places 180 degrees apart, so I'd say it's something mechanical.
Nick.   2016 celebrating the 20th anniversary of "Königshafen" exhibition layout!

Offline Westbury

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Re: Faulty New release 4F.
« Reply #2 on: July 06, 2017, 06:49:06 pm »
How much running in time has it had ?

I've had the odd loco thats been a bit iffy running out the box but a good hours running at different speeds / directions has settled it down...

Offline Dave_cooper79

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Re: Faulty New release 4F.
« Reply #3 on: July 06, 2017, 06:54:41 pm »
It's had 1/2 an hour in both directions at half speed, I'm going to give it an hour in each direction this evening to see if there is any change, if not I think a warranty return might be in order unfortunately.


Offline newportnobby

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Re: Faulty New release 4F.
« Reply #4 on: July 06, 2017, 09:17:54 pm »
Have you tried running it on DC as, if it's OK, everything points to either the chip or summat within your DCC set up?

Offline Dave_cooper79

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Re: Faulty New release 4F.
« Reply #5 on: July 06, 2017, 09:43:28 pm »
It's a bit juddery in DC too, I'm going to try another chip this week to rule that out, after a good two hours extra running in it still is performing poorly, particularly when it's pulling anything.

Offline Dr Al

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Re: Faulty New release 4F.
« Reply #6 on: July 07, 2017, 09:23:53 am »
Looks mechanical - it's clearly got mechanical resistance at approximately two points per wheel rotation - implies something with an intermediate gear (swarf between teeth, or a damaged tooth perhaps).

Cheers,
Alan
Quote from: Roy L S
If Dr Al is online he may be able to provide a more comprehensive answer.

Offline Dave_cooper79

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Re: Faulty New release 4F.
« Reply #7 on: July 07, 2017, 12:38:52 pm »
Thanks for all your help so far.

On opening up the chassis I've found the recess for the largest cog seems to be in the wrong place, I've attached pictures, where it should be centered its off by some margin, would that catch the gear enough to cause the judders?
the off center bit can be seen in the pdf Chassis 2

« Last Edit: July 07, 2017, 12:40:12 pm by Dave_cooper79 »

Offline Dr Al

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Re: Faulty New release 4F.
« Reply #8 on: July 07, 2017, 12:43:01 pm »
On opening up the chassis I've found the recess for the largest cog seems to be in the wrong place, I've attached pictures, where it should be centered its off by some margin, would that catch the gear enough to cause the judders?
the off center bit can be seen in the pdf Chassis 2

I don't think so. The gear looks to be running true on its axle - it wouldn't be able to drop into that recess when running. If it was in that recess the whole thing would be locked up solid.

Check for protrusions, moulding flash etc on all the gears (particularly this one) that could be catching on the edges of the lip though - e.g. on that gear there looks to be a moulding pip - could that be catching the edges of the recess on the other chassis side?

Cheers,
Alan
Quote from: Roy L S
If Dr Al is online he may be able to provide a more comprehensive answer.

Offline Dr Al

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Re: Faulty New release 4F.
« Reply #9 on: July 07, 2017, 12:46:31 pm »
P.s. you might be able to remove the motor then part reassemble the chassis sides so you can turn the gears by hand and feel exactly where there's a stiff point - and you then may be able to see exactly what's catching.

Cheers,
Alan
Quote from: Roy L S
If Dr Al is online he may be able to provide a more comprehensive answer.

Online Steve Brassett

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Re: Faulty New release 4F.
« Reply #10 on: July 08, 2017, 04:57:48 pm »
My 4F is very juddery.  Unfortunately, I have played around with it too much to send it back.  I am pretty sure now it is down to quartering.  I have got it running better, which confirms my thoughts.  One day I will have a further play.

Offline Izzy

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Re: Faulty New release 4F.
« Reply #11 on: July 08, 2017, 07:37:30 pm »

Although in many respects the new version Farish 4F is a very nice loco is does suffer in one area compared to the new version Jinty in that it drives off the rear axle rather than the middle one, and has an extra idler gear at the end of the gear train to reach the driven axle. It would still need this if it had driven off the middle due to the increased distance to the drive axle compared to the Jinty, but driving off the middle axle can often offset/even out any slop in the coupling rods and gear train. As it is the combination of rear axle drive and idler gear means there is a lot of extra play/slop in the gear train and this does often seem to lead to jittery/juddery running at certain speeds, the kind normally only found with DCC fitting and too high a level of BEMF.  This does not occur with the Jinty. I found that fitting a CT DCX 76 decoder to the 4F and reducing some BEMF values actually helped to almost eliminate this juddering.

The revised cv settings I used are here in this thread, which may prove useful:

http://www.rmweb.co.uk/community/index.php?/topic/82934-farish-jinty-2fs-dcc-jinty-update-4f-2fsdcc-conversion/page-2

However, having said that the type of running seen in the video - I am not sure I would class that as juddering but maybe it is at higher/different speeds -  I would say is due to quartering issues as a first cause since it only happens at certain fixed points on each wheel revolution. If this is the cause then I am afraid it won't improve however much running is done until that is adjusted.

Izzy




Offline Roy L S

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Re: Faulty New release 4F.
« Reply #12 on: July 08, 2017, 07:54:10 pm »
Driven goes to the rear axle because that is where the traction tyres would have gone had they been fitted!

Roy

Offline Izzy

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Re: Faulty New release 4F.
« Reply #13 on: July 09, 2017, 12:30:14 pm »
Ah yes, this would have helped those looking for a bit more haulage capacity. Pity spare sets of wheels both with/without tyres aren't available/provided as an option. But I don't think it wouldn't overcome the excess slop in the gear train issue, might actually make it worse. No real way to know. Unless of course the 2MT 2-6-0 also has the same gear train. Anyone know?

Izzy

edited to add- just looked up the service sheet. 2MT drives the middle axle with no idler gear.
« Last Edit: July 09, 2017, 01:17:59 pm by Izzy »

 

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