British N gauge Mechanical Quality

[David Bale]

It's a known issue with Farish gears , hence my previous comment. It just seems to happen randomly, other manufacturers are not affected in the same way.

Here's an example:


Farish (Bachmann) split gear by Rail Squid, on Flickr

(head of the screwdriver is pointing at the split).

Loco still runs, but with a "clack clack clack" sound, and if kept running would quite likely lock up, which would damage the motor.

This is why I have a baggie of these:


Bachmann 16 tooth gears by Rail Squid, on Flickr

I suppose the upside is that I've acquire a few very nice second-hand locos over the years for a good price due to this issue, which is fairly straightforward to fix (I'll write it up if we don't have it somewhere already).

Either wrong type of plastic or wrong shape I assume, have you ever asked farish for a free replacement?

[railsquid]

Either wrong type of plastic or wrong shape I assume, have you ever asked farish for a free replacement?

I heard they might send out single gears if you ask nicely, but I decided it would be more pragmatic just to buy a bunch.

[Izzy]

Although not nearly so common split gears are not unknown in scales such as OO. There replacement gears are not easy to obtain, often just not available at all, so at least in N locos, even though it shouldn't be needed, they can be repaired. I am surprised about the new version class 25. I thought the newer/thicker gears used were supposed to prevent splitting. Oh well...

Izzy

[ntpntpntp]

Farish aren't the only brand which suffer split gears though they seem to have had more than their fair share.  I have replaced a few gears in Arnold, Minitrix, and Roco locos,  and even one Fleischmann loco.     

If I can, I replace with brass gears by firms such as KH Modellbahnbau.  If I cannot find a stock replacement I'll get gears made up by Kkpmo Mikroantriebe. Not cheap but reliable delrin.

The main cause of splits seems to be an overtight interference fit. Over-oiling doesn't help either.

Although not nearly so common split gears are not unknown in scales such as OO.

Yep, here's a G scale split    (Also a Bachmann model as it happens)

[Dr Al]

It just seems to happen randomly

In old Pre-2000 locos this is largely true, but the newer locos it's much less common, and very very commonly linked to a moulding deficiency.

Halving a split gear, you'll find it very common to see a moulding bubble or void at the point its split - I've seen this repeatedly on post-2000 models, and almost always when a newer model has a split. Fortunately it happens much less commonly - but it is a manufacture issue, and still happens across the Farish range - even new tool DCC ready tender drive models, I've seen a couple split gears - those being a completely new moulding, different diameter and tooth count.

Farish seem aware of the problem though - there seems to have been a gradual move to white nylon gearing more and more - which is good if they keep that up as those seem much less prone. Honestly, if this is more expensive, I'd rather just pay, knowing that it much diminishes the risk of future failure.

When replacing, use a taper broach to ream out the central gear hole to lessen the stress on the gear - thus if the replacement also has a void or a weak spot, it should be much less prone to splitting again. Plus, it makes them easier to get on the axles! Ideally they should slide on reasonably easily, but you also don't want to make them too loose such that they risk slipping on the axle.

HTH,
Alan - replaced two on Farish class 46s last night!

[railsquid]

It just seems to happen randomly

In old Pre-2000 locos this is largely true, but the newer locos it's much less common, and very very commonly linked to a moulding deficiency.

Halving a split gear, you'll find it very common to see a moulding bubble or void at the point its split - I've seen this repeatedly on post-2000 models, and almost always when a newer model has a split. Fortunately it happens much less commonly - but it is a manufacture issue, and still happens across the Farish range - even new tool DCC ready tender drive models, I've seen a couple split gears - those being a completely new moulding, different diameter and tooth count.

The vast majority of my Farish collection is Bachmann-era, if memory serves correctly all the split gears I've experienced until now are among the older Bachmann locos (all diesels) which came in the boxes with the grey foam inlays (whether split-chassis or DCC); this is the first one I've experienced on a loco from the more recent transparent box-in-a-box runs (for reference this is 371-088, date stamp on the cardboard outer packaging is July 2014).

When replacing, use a taper broach to ream out the central gear hole to lessen the stress on the gear - thus if the replacement also has a void or a weak spot, it should be much less prone to splitting again. Plus, it makes them easier to get on the axles! Ideally they should slide on reasonably easily, but you also don't want to make them too loose such that they risk slipping on the axle.

So, I just went to replace the gear, and the first one I got out of the little baggie pictured above fitted very tightly onto the axle and was impossible to push over the raised section in the middle. The next one I tried fitted firmly as per previous replacements (all of which have been just fine). Which makes me wonder if there's some degree of variation in the diameter of the hole with some being a little too tight (but forced onto the axle during manufacture) and the slight excess pressure causes them to eventually split... As far as I can tell the offending gear is a straight split with no obvious bubble/void.

Alan - replaced two on Farish class 46s last night!

Had split gears on all 3 of my 46s (though one of them was bought second-hand with heavy discount due to pre-existing split gear, which was probably more than enough to recoup the investment in above baggie of gears...)

[railsquid]

My main gripes with British N gauge ere the propensity of Farish items to develop split gears

In the process of going through my British stock to rebox for convenience, and lo-and-behold my Farish Class 25 (the DCC version, bought new in 2014), which was fine last time I tried it, set off with the distinct "clack clack clack" which indicates at least one of the gears has fallen victim to the gear weevils...  :'(

Hah, checking my spreadsheet I see I noted the split gear in April 2019. Anyway was just the one gear affected.

[David Bale]

Update on my dapol class 121
Dapol have sent me a replacement for the one returned for being noisy. I'm not sure it is any quieter or smoother! As I suspected it is normal for this loco. But there is a positive! Lights at the front bottom as well as the top. These did not light on the previous one, or does it depend on the CV settings?
But this model initially came off the track when going through peco setrack points, this was due to the brass pickup strips that also create a bit of suspension on one bogie were flat.
So my recent experience of mechanicals with dapol so far. Panier tank and class 33 good, class 121 poor. Although I'm told the Class 121 is an older design. The jury is still out on Dapol hopefully the 121 is not typical.