Bachmann Spectrum Gear Replacement

P

Paradise

Registered
28 Jan 2010
997
Following a recent question on a related thread I thought I would start a specific thread on the subject of the replacement of split plastic gears on the 4-4-0, 2-6-0 and 2-8-0 Spectrum models.

A few key points:
1) The replacement plastic gears on axle from Bachmann spare parts for the 4-4-0 / 2-6-0 now have a D shaped hole rather than a spline. I bought two replacements from Bachmann spare parts, one came already split at the hub when I received the order but this may have just been an isolated incident. It is still firm on the axle.
2) The replacement delrin gears from 'North West Short Line' as listed on their old site was somewhat confusing. The 24 tooth gear is listed as a replacement for the 4-4-0 but the two 4-4-0's and 2-6-0 I have repaired both had 25 tooth gears. Several years back on a related forum, I recall Kevin Strong stating that he had replaced several gears in the Spectrum 4-4-0 / 2-6-0 and they were all 25 tooth.
3) Several web pages/pdf online with detailed instructions on doing the repair state ordering the 24 tooth gear replacement from NWSL although the pictures in the instructions show their old cracked gear which is 25 tooth.
4) The replacement 25 tooth brass gear from Bachmann for the 2-8-0 has been used by some people to repair the 4-4-0 and 2-6-0 although some modification may be needed to press it on the axle which is splined for interference fit where the gear sits. It is also slightly thicker at the gear face than the plastic gears which may not be an issue. All the Bachmann plastic gears have a face of approximately 3.9mm. The brass and NWSL delrin ones are 4.4mm.

Perhaps there are some Bachmann 4-4-0's with a 24 tooth gear but I have never come across any reliable source of that. I suspect there may be confusion from the NWSL 24 tooth gear product description. The question mark speaks volumes. Best to check the tooth count on your cracked gear first before ordering from NWSL.
NorthWest Short Line

From left to right below:
Original Bachmann 2-6-0 25 tooth gear on 46mm splined axle. (split)
Replacement Bachmann 4-4-0 25 tooth gear with D shaped hole (no spline) on 43.4mm axle. (currently Bachmann spare parts list this as replacement for both 4-4-0 and 2-6-0).
Original outside frame 2-8-0 25 tooth gear on splined axle (split)
Replacement Bachmann outside frame 2-8-0 brass 25 tooth gear on axle. Gear face 4.4mm.
NWSL 24 tooth delrin gear. Part No. 2223-6.
NWSL 25 tooth delrin gear. Part No. 2226-6.

I hope this helps others avoid some confusion when fixing their cracked Spectrum gears. :)

BachmannSpectrumNWSL_Gears_00.JPG

Some related links. Just be careful what you read.
Bachmann Forum
Bachmann Mogul - dreaded split gear issue - G Scale Central
Issues with Bachmann Consolidation gears? - myLargescale.com > Community > Forums
Axle with brass gear (Large Scale 2-8-0) [G813X-AXELBG] - $11.00 : Bachmann Trains Online Store!
 
Last edited:
L

LGeoB

Registered
12 Dec 2017
125
Perth, Western Australia
Following a recent question on a related thread I thought I would start a specific thread on the subject of the replacement of split plastic gears on the 4-4-0, 2-6-0 and 2-8-0 Spectrum models.

A few key points:
1) The replacement plastic gears on axle from Bachmann spare parts are a waste of time as they will probably suffer the same splitting as in the new locomotives. I bought two replacements from Bachmann spare parts, one came already split when I received the order.
2) The replacement delrin gears from 'North West Short Line' as listed on their old site was somewhat confusing. The 24 tooth gear is listed as a replacement for the 4-4-0 but the two 4-4-0's and 2-6-0 I have repaired both had 25 tooth gears. Several years back on a related forum, I recall Kevin Strong stating that he had replaced several gears in the Spectrum 4-4-0 / 2-6-0 and they were all 25 tooth.
3) Several web pages/pdf online with detailed instructions on doing the repair state ordering the 24 tooth gear replacement from NWSL although the pictures in the instructions show their old cracked gear which is 25 tooth.
4) The replacement 25 tooth brass gear from Bachmann for the 2-8-0 has been used by some people to repair the 4-4-0 and 2-6-0 although some modification may be needed to press it on the axle which is knurled for interference fit where the gear sits. It is also slightly thicker at the gear face than the plastic gears which may not be an issue. All the Bachmann plastic gears have a face of approximately 3.9mm. The brass and NWSL delrin ones are 4.4mm.

Perhaps there are some Bachmann 4-4-0's with a 24 tooth gear but I have never come across any reliable source of that. I suspect there may be confusion from the NWSL 24 tooth gear product description. The question mark speaks volumes. Best to check the tooth count on your cracked gear first before ordering from NWSL.
NorthWest Short Line

From left to right below:
Original Bachmann 2-6-0 25 tooth gear on 46mm axle. (split)
Replacement Bachmann 4-4-0 25 tooth gear on 43.4mm axle. (currently Bachmann spare parts list this as replacement for both 4-4-0 and 2-6-0).
Original outside frame 2-8-0 25 tooth gear on axle (split)
Replacement Bachmann outside frame 2-8-0 brass 25 tooth gear on axle. Gear face 4.4mm.
NWSL 24 tooth delrin gear.
NWSL 25 tooth delrin gear.

I hope this helps others avoid some confusion when fixing their cracked Spectrum gears. :)

View attachment 259108

Some related links. Just be careful what you read.
Bachmann Forum
Bachmann Mogul - dreaded split gear issue - G Scale Central
Issues with Bachmann Consolidation gears? - myLargescale.com > Community > Forums
Not sure if this helps but for a Bachmann three truck Shay, the gear is a standard 22 test, 32 pitch gear which is used in some RC cars. I bought some Castle Creations ones made of aluminium that just needed drilling out to fit the axles. Are the gears for your engines a standard size per chance?

Geoff
 
Rhinochugger

Rhinochugger

Retired Oik
27 Oct 2009
28,200
North West Norfolk
Following a recent question on a related thread I thought I would start a specific thread on the subject of the replacement of split plastic gears on the 4-4-0, 2-6-0 and 2-8-0 Spectrum models.

A few key points:
1) The replacement plastic gears on axle from Bachmann spare parts are a waste of time as they will probably suffer the same splitting as in the new locomotives. I bought two replacements from Bachmann spare parts, one came already split when I received the order.
2) The replacement delrin gears from 'North West Short Line' as listed on their old site was somewhat confusing. The 24 tooth gear is listed as a replacement for the 4-4-0 but the two 4-4-0's and 2-6-0 I have repaired both had 25 tooth gears. Several years back on a related forum, I recall Kevin Strong stating that he had replaced several gears in the Spectrum 4-4-0 / 2-6-0 and they were all 25 tooth.
3) Several web pages/pdf online with detailed instructions on doing the repair state ordering the 24 tooth gear replacement from NWSL although the pictures in the instructions show their old cracked gear which is 25 tooth.
4) The replacement 25 tooth brass gear from Bachmann for the 2-8-0 has been used by some people to repair the 4-4-0 and 2-6-0 although some modification may be needed to press it on the axle which is knurled for interference fit where the gear sits. It is also slightly thicker at the gear face than the plastic gears which may not be an issue. All the Bachmann plastic gears have a face of approximately 3.9mm. The brass and NWSL delrin ones are 4.4mm.

Perhaps there are some Bachmann 4-4-0's with a 24 tooth gear but I have never come across any reliable source of that. I suspect there may be confusion from the NWSL 24 tooth gear product description. The question mark speaks volumes. Best to check the tooth count on your cracked gear first before ordering from NWSL.
NorthWest Short Line

From left to right below:
Original Bachmann 2-6-0 25 tooth gear on 46mm axle. (split)
Replacement Bachmann 4-4-0 25 tooth gear on 43.4mm axle. (currently Bachmann spare parts list this as replacement for both 4-4-0 and 2-6-0).
Original outside frame 2-8-0 25 tooth gear on axle (split)
Replacement Bachmann outside frame 2-8-0 brass 25 tooth gear on axle. Gear face 4.4mm.
NWSL 24 tooth delrin gear. Part No. 2223-6.
NWSL 25 tooth delrin gear. Part No. 2226-6.

I hope this helps others avoid some confusion when fixing their cracked Spectrum gears. :)

View attachment 259108

Some related links. Just be careful what you read.
Bachmann Forum
Bachmann Mogul - dreaded split gear issue - G Scale Central
Issues with Bachmann Consolidation gears? - myLargescale.com > Community > Forums
Axle with brass gear (Large Scale 2-8-0) [G813X-AXELBG] - $11.00 : Bachmann Trains Online Store!
The replacement Bachmann axle (from Bachmann Estore) for the Connie 2-8-0 has a brass gear :nod: :nod:

Well, the two that I bought in 2017 were .............
 
Fred2179G

Fred2179G

Registered
20 Apr 2017
500
USA
The replacement plastic gears on axle from Bachmann spare parts are a waste of time as they will probably suffer the same splitting as in the new locomotives.
Hmmm . . Not sure I agree with that statement. Bachmann's new part, which you show second from left, has a flat on the axle and therefore those axles won't take the NWSL gears without some significant modification. It has also been suggested that they won't spin on the axle if they split - which I find difficult to accept! Hopefully Bachmann made them out of different plastic? If not, you still get 10+ years before they shrink and crack.



I recently dealt with a 4-4-0 and it turned out the axle was this new type and the problem was the worm follower. Jiro made me a new one and the loco is running fine.
 
Fred2179G

Fred2179G

Registered
20 Apr 2017
500
USA
Two more comments occurred to me.
- NWSL closed up shop this summer so the parts are unavailable. An employee was said to be taking over. I queried the availability of the gear mid-summer and was told the new owner would be contacted about my request. I have heard nothing since. In any case the gear won't fit the new "D" shaped axle, though it will fit the old style.

- as I noted, my problem wasn't the axle gear. So if your loco stops with a spinning motor sound but no motion, take it apart before you order the gears. Here's the thread about the worm+follower:
Large Scale Central - Advanced Forum Detail Topic - A Different Spectrum 4-4-0 Gear Problem
 
Rhinochugger

Rhinochugger

Retired Oik
27 Oct 2009
28,200
North West Norfolk
Hmmm . . Not sure I agree with that statement. Bachmann's new part, which you show second from left, has a flat on the axle and therefore those axles won't take the NWSL gears without some significant modification. It has also been suggested that they won't spin on the axle if they split - which I find difficult to accept! Hopefully Bachmann made them out of different plastic? If not, you still get 10+ years before they shrink and crack.
The problem wasn't shrinking and cracking, it was damage during the manufacturing process and the force fit onto the axle.

My original Connie, stored in an unheated garage, and having suffered sudden stop / starts with an intermittent track power feed problem, had a virtually undamaged drive gear (I still changed it 'cos I had the loco apart and a new one ready by the time I saw the gear).

The second one I bought, second hand but only very slightly used (judging by the wheel wear) had a badly split gear - but the splits were from the centre, and hadn't got to the edge. Now, in my book, that's not shrinkage cracking :shake::shake::shake::shake:
 
Fred2179G

Fred2179G

Registered
20 Apr 2017
500
USA
The problem wasn't shrinking and cracking
I merely quoted the opinions of my learned friends, as all the ones we've seen were cracked all the way to the outside, as if the axle was too big for the gear. But as we'll never know the scientific reason, I am quite willing to concede that it wasn't shrinking or cracking. Onward and upward. . . :D :D
 
S

Sparesman

Accidental Trader
9 Jan 2015
67
From a purely engineering point , if you try to put a shaft into a same size hole ,
if that hole is in the centre of a small gear , it will split the gear through the
root of the tooth , this has been the problem for many years with particular
manufacturer . Worse if there is a knurled portion on the shaft , which gives
grip , but increases the shaft diameter.
Best to make the gear a tight push fit and then use a good superglue .
I am going to see HPC Gears this week and will enquire about small worm and
wheel sets , and post more details if they can help.
 
Fred2179G

Fred2179G

Registered
20 Apr 2017
500
USA
it will split the gear through the
root of the tooth , this has been the problem for many years with particular
manufacturer
It would seem that they don't split immediately - usually after about 10 years; hence the 'shrinking' theory. Most of the Bachmann 2-6-0 & 4-4-0 models are at least that old. The new 2-6-0 has a different gear of brass.
 
Rhinochugger

Rhinochugger

Retired Oik
27 Oct 2009
28,200
North West Norfolk
It would seem that they don't split immediately - usually after about 10 years; hence the 'shrinking' theory. Most of the Bachmann 2-6-0 & 4-4-0 models are at least that old. The new 2-6-0 has a different gear of brass.
Ah, I think the issues with the 2-6-0 and 4-4-0 may be different from the Connie - the axles are very different

I've only dealt with the Connie issues - I now have a 4-4-0, but haven't had to dismantle the gearbox .............................. :tmi::tmi:
 
maxi-model

maxi-model

UK/US/ROW steam narrow gauge railways 1:1
27 Oct 2009
4,828
Bucks/Oxon/Northants area
I have a habit of not throwing things away. My 2-6-0, bought NIB 12 years ago, gear failed after about 5-6 years use. I picked up a notification on another forum about 3-4 years ago that Bachmann had replacements back in stock. I ordered 2. The first thing I noticed was that the gear was on a D shaped mount rather than the original splined one shown above it. That's where I think the confusion with the NWSL replacements may be coming from. If the pitch circumference for the 24 & 25 tooth gears are about the same then I assume they should work in the same gear train. I have no idea if my 2-6-0 was equipped with the 24 or 25 tooth originally. Perhaps Bachmann had a rethink on the gear ratio between the two types release.


20191124_174330.jpg

For good measure I show also the axle from my Connie that was replaced with a brass geared one, ready fitted, supplied by Bachmann UK about 6 years ago.

In both cases, both splined original axel fitted gear wheels split. How long till and why these failed is probably down to, time of use, loads on the loco and the topology of the layout they were run on. Looking at the types of solutions that Bachmann settled on is probably indicative of the shortcomings of using a splined mount with a cheap nylon gear i heavier load applications in the first place. It was the early days of Bachmann operating in the Fn3 world with the heavier than Big Hauler stock, like the Spectrum and AMS articles. They learnt.
Max
 
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Rhinochugger

Rhinochugger

Retired Oik
27 Oct 2009
28,200
North West Norfolk
I have a habit of not throwing things away. My 2-6-0, bought NIB 12 years ago, gear failed after about 5-6 years use. I picked up a notification on another forum about 3-4 years ago that Bachmann had replacements back in stock. I ordered 2. The first thing I noticed was that the gear was on a D shaped mount rather than the original splined one shown above it. That's where I think the confusion with the NWSL replacements may be coming from. If the pitch circumference for the 24 & 25 tooth gears are about the same then I assume they should work in the same gear train. I have no idea if my 2-6-0 was equipped with the 24 or 25 tooth originally. Perhaps Bachmann had a rethink on the gear ratio between the two types release.


View attachment 259129

For good measure I show also the axle from my Connie that was replaced with a brass geared one, ready fitted, supplied by Bachmann UK about 6 years ago.

In both cases, both splined original axel fitted gear wheels split. How long till and why these failed is probably down to, time of use, loads on the loco and the topology of the layout they were run on. Looking at the types of solutions that Bachmann settled on is probably indicative of the shortcomings of using a splined mount with a cheap nylon gear i heavier load applications in the first place. It was the early days of Bachmann operating in the Fn3 world with the heavier than Big Hauler stock, like the Spectrum and AMS articles. They learnt.
Max
Yes, fully agree.

It's also useful to look at the 0 Gauge and Gauge 1 gearbox solutions. The reality is that we put quite a bit of load on some very small parts :whew::whew:
 
P

Paradise

Registered
28 Jan 2010
997
Hmmm . . Not sure I agree with that statement. Bachmann's new part, which you show second from left, has a flat on the axle and therefore those axles won't take the NWSL gears without some significant modification. It has also been suggested that they won't spin on the axle if they split - which I find difficult to accept! Hopefully Bachmann made them out of different plastic? If not, you still get 10+ years before they shrink and crack.



I recently dealt with a 4-4-0 and it turned out the axle was this new type and the problem was the worm follower. Jiro made me a new one and the loco is running fine.
Fred. Ah yes! The Bachmann replacement gear for the 4-4-0 and 2-6-0 does have a D shape hole for the axle. Something I did notice years back when I first received the parts but one was already cracked at the hub so they were put back in the bag and not taken seriously. My repairs were done with the NWSL delrin gears on the original round splined axles. I'll change my first post to avoid my bad advice. My main point was the 4-4-0 / 2-6-0 tooth count conundrum.
I don't know what the 24 tooth gears are actually used for as people seem to only have 25 tooth gears in those models.

I have bought 5 Bachmann 2-8-0 connies and every one of them was split from new. I suspect they were all returns to the OS dealer who I bought them off at discount. OS orders don't come back and they closed a few months later. All were repaired with the replacement brass gear from Bachmann.

The NWSL website has been redesigned recently since the original owner's closure several months back but not all products are listed yet. I'm not sure of what the situation is with the new owner or if the delrin gears are still available from them. Time will tell.

Geof, good to know about the RC car gears fitting the 3 truck shay. I may need to do that one day.

Max, interesting how your two axles seem to be the same length. The original having a spline and the newer replacement having a flat to accommodate the D shape hole in the gear.
My two have a 2.6mm difference in length.

Thanks for the comments guys. It's good to have it all in one place with links and as usual, I'm still learning... :)
 
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Greg Elmassian

Greg Elmassian

Registered
8 Mar 2014
4,152
San Diego
www.elmassian.com
Underlining what Fred said, the nylon gears as a whole tend to shrink over time, and the interference fit is also a bit too tight. Not all gears split, but most do, and some are delivered to the customer split.

The new D shaped arrangement helps a lot, but it's not on all locos. The 24 vs 25 "debate" has raged on, and you can usually use either gear, apparently the 24 was the original design, but looks like for certain years, Bachmann used a 25 because it had some of these, but again there are all kinds of opinions and no "official" information from Bachmann.

NWSL is pretty much still out to lunch (meaning not fully running) and it looks like certain items that were always in stock are not in stock now. The company is still adjusting to the change in ownership and move.

If you find new old stock of NWSL delrin gears, buy them if you think you will be needing them.

Anyway, almost every Bachmann loco has had some kind of gear problems over the years, from the trolley to the hand car to the mogul, connie, big hauler, american.


Best of luck,

Greg
 
Rhinochugger

Rhinochugger

Retired Oik
27 Oct 2009
28,200
North West Norfolk
Anyway, almost every Bachmann loco has had some kind of gear problems over the years, from the trolley to the hand car to the mogul, connie, big hauler, american.




Greg
Yeah, I think they were just about getting it together when they pulled out of Fn3 - The K27, C19 and Mallet seem to be OK :think::think::think:

And for some reason, the 45 Tonner doesn't appear to have had an issue either.
 
P

Paradise

Registered
28 Jan 2010
997
Yeah, I think they were just about getting it together when they pulled out of Fn3 - The K27, C19 and Mallet seem to be OK :think::think::think:
And for some reason, the 45 Tonner doesn't appear to have had an issue either.
Although the K27 has a double worm gear therefore twice the final speed which may have been a ratio mistake and explains why it goes too fast.
 
Greg Elmassian

Greg Elmassian

Registered
8 Mar 2014
4,152
San Diego
www.elmassian.com
And has no pulling power, and other running issues caused by a double lead worm.... (the worm gear is the other gear, i.e. there is a worm and a worm gear, the worm is double lead in this case, the worm gear does not look any different)
 
Rhinochugger

Rhinochugger

Retired Oik
27 Oct 2009
28,200
North West Norfolk
Although the K27 has a double worm gear therefore twice the final speed which may have been a ratio mistake and explains why it goes too fast.
And has no pulling power, and other running issues caused by a double lead worm.... (the worm gear is the other gear, i.e. there is a worm and a worm gear, the worm is double lead in this case, the worm gear does not look any different)
Sounds weird - I've not had the luxury of even touching a Bachmann K27, but one of the principles of easing the stresses on gearboxes in the larger scales is to use a 2-stage box. However, a double worm is an oddity, although it may have been somebody's brainwave to overcome a height / size issue.

ABC use helix gears on their Gauge 1 gearboxes to reduce wear and stress. I'd been led to believe that the K27 had a helix gear :oops:
 
P

Paradise

Registered
28 Jan 2010
997
I think the double lead worm helps to minimise the engine surging when going down inclines due to slop in the gear train.
For those who don't understand what a double lead worm is. It is like two separate helical grooves side by side on the worm. One worm revolution displaces it's driven gear by two teeth.
 
Rhinochugger

Rhinochugger

Retired Oik
27 Oct 2009
28,200
North West Norfolk
I think the double lead worm helps to minimise the engine surging when going down inclines due to slop in the gear train.
For those who don't understand what a double lead worm is. It is like two separate helical grooves side by side on the worm. One worm revolution displaces it's driven gear by two teeth.
Ah, gotcha - that makes sense - hence the higher gear ratios

Now I understand :nod::nod: