Wrenn gear disaster

[cypherman]

Hi all,

The motor for one of  my Wrenn N2's had shredded it's worm gear. Not  clue if I can get a replacement worm gear or even how to dismantle a Wrenn engine. This is the first time one has failed on me. Any one got any tips or ideas. If I can get a replacement and I think that's a big if I do have a worm puller so if I can get at it I should be able to remove it. Getting it back on might be a bit interesting

[33C]

Replace the whole armature and worm. Undo the top lock nut, take out the bearing screw and withdraw the whole armature and worm through the side of the block. You could send it away for an exchange unit?

[John Isherwood]

2 minutes ago, 33C said:

Replace the whole armature and worm. Undo the top lock nut, take out the bearing screw and withdraw the whole armature and worm through the side of the block. You could send it away for an exchange unit?

 

Didn't Wrenn N2s have HD-style R1 chassis - in which case the motor is a separate item, surely?

 

CJI.

[33C]

No, no room for the rear pony...

[cypherman]

Hi all,

Yes the motor is removable. Similar to the early XT60 Triang motors. The Wrenn motors are not the same as the H/D ones. 2 screws and they come off. But the worm is shrouded and difficult to get at. I will look for a replacement if I cannot find a replacement worm.

[John Isherwood]

2 hours ago, 33C said:

No, no room for the rear pony...

 

Not true - please check before posting.

 

CJI.

[33C]

All mine have the horseshoe type and that's how I change them. Not seen that type before, assuming these are N2's?

[John Isherwood]

3 minutes ago, 33C said:

All mine have the horseshoe type and that's how I change them. Not seen that type before, assuming these are N2's?

 

It has recently been posted here that Wrenn did not perpetuate the horseshoe chassis, but adapted the HD R1 chassis.

 

That was not the first time that I have come across this information.

 

CJI.

[Ruffnut Thorston]

The Wrenn, and Hornby Dublo, Half inch motor comes to pieces well…

 

The shroud or bearing support comes off, it is secured by machine screws.

 

Parts and whole motors are available…

 

 

https://www.ebay.co.uk/itm/324731157849?

 

 

https://www.ebay.co.uk/itm/313621991460?

 

 

The Hornby Dublo 0-6-2 (N2) Chassis.

 

 

 

The Wrenn modified R1 0-6-2 (N2) chassis. An adaptor casting is attached to the R1 rear coupling fixing hole…

 

 

 

 

 

 

https://www.ebay.co.uk/itm/353610964267?

 

 

Edited August 9, 2021 by Ruffnut Thorston
More added

[Il Grifone]

Exchange components are usually expected to be in serviceable with just rewinding, so a stripped worm might not be accepted.

However a Dublo/Wrenn armature (or complete motor) is fairly easy to obtain.

 

To dismantle, undo the body screw at the front. The motor is held by two screws revealed once the pickup assembly is removed. Take care as it is delicate and tends to fall apart.

 

I think (perhaps someone who has them to hand can confirm?) that the worm is the same as those on the Deltic/Co-Bo idler shaft and may be a cheaper solution. One of these supplied me with a worm for an X.04 which will power my latest Dublo Castle. 

IIRC the Dublo worms are soldered to the shaft and do not require a puller.

 

Wrenn produced a new pony truck for the N2 which results in guard irons in the wrong place.

 

Searching on eBay, found 2 X.04s described as Dublo motors (they're not and don't fit without modification) an armature (rather expensive at £20, but that is the price for an exchange armature)

 

https://www.ebay.co.uk/itm/304033730433?hash=item46c9d28f81:g:rwIAAOSwWglgyGi5

 

There are complete motors for £29.50

 

https://www.ebay.co.uk/itm/353084793721?hash=item52357e6379:g:PwUAAOSwx2dYDzek

 

(Usual disclaimer for all).

Edited August 10, 2021 by Il Grifone

[cypherman]

Hi all,

I have just bought a replacement motor and a replacement armature. Sad thing about the original motor is that it runs really sweetly. I will still try and find a replacement worm. Any chance the worm from an x03 motor would work as I have several of them spare.

Edited August 10, 2021 by cypherman

[Il Grifone]

The pitch of the Tri-ang worms is completely different. I am not sure whether the interaxes of are the same however which would enable both gears to be exchanged. The Tri-ang one is on the relevant service sheet (430 thou.); Dublo's is top secret. Obviously the Tri-ang gear would need bushing (Tri-ang axles are 9/64"; Dublo 1/8" diameter. Luckily the armature shaft diameter is the same for both motors 3/32".

[Il Grifone]

Talking of gear replacements, I have a Tri-ang Bo-Bo Transcontinental power bogie with stripped spur gears (the early type with the short shaft X.04 motor). These appear to be the same diameter as the standard worm wheel S.2021, but with teeth cut parallel to the shaft and a centre hole to force fit a 3/32" shaft.

Service sheet 6  http://www.hornbyguide.com/service_sheet_details.asp?sheetid=157

 

Does anyone know of suitable replacements?

Edited August 11, 2021 by Il Grifone

[cypherman]

Hi all,

One thing i do not understand is why a worm gear that was looking completely alright and was well lubricated should just disintegrate like it did. Does brass have a similar problem like mazak at some stage of it's life. The motor was running freely and under no load when it happened.

[Ruffnut Thorston]

Brass can I think get “work hardened”. 
This makes it go brittle.

 

I remember that a brass paraffin lamp font that had been polished for years split apart.

[Il Grifone]

Could it be what happened to my bogie? I doubt it could be lack of lubrication and they mesh correctly or they would if they had any teeth left (a bit like their owner!).

[sagaguy]

21 hours ago, Ruffnut Thorston said:

Brass can I think get “work hardened”. 
This makes it go brittle.

 

I remember that a brass paraffin lamp font that had been polished for years split apart.

I remember many years ago when i was heavily into model engineering,i was given a couple of blocks and a length of square cast brass.When i went to use them,they had gone brittle with crystilline cracks so yes,brass can disintegrate over time.

 

                            Ray.

[cypherman]

Hi all,

Well the spare motor and armature arrived today. i now have 2 working motors. I will fit the on in the engine tomorrow as there is a little soldering to do and I am too tired from work at the moment.

Is ther any way to get the worm off the old armature. I tried with my gear puller but it would not budge.

Edited August 13, 2021 by cypherman

[uax6]

Try heating the brass up with a small blow lamp (like a chefs one) it should expand it which will help break its grip on the shaft, and your puller should then get it off.

 

Andy G

[Ruffnut Thorston]

On 10/08/2021 at 09:03, Il Grifone said:

>Snipped

 

I think (perhaps someone who has them to hand can confirm?) that the worm is the same as those on the Deltic/Co-Bo idler shaft and may be a cheaper solution. One of these supplied me with a worm for an X.04 which will power my latest Dublo Castle. 

IIRC the Dublo worms are soldered to the shaft and do not require a puller.

 

>Snipped

The worm may be soldered onto the shaft.

 

 

Edited August 14, 2021 by Ruffnut Thorston
Tidying

[Il Grifone]

I have used a large file to remove brass worms in the past, usually from X.04s to fit something less appropriate to a racing car.  Just take care to remove any filings etc. before fitting the new one.

If the worm is knackered, it won't be any loss.

 

Obviously care is necessary with a blowlamp to avoid damage to the commutator and/or windings. It could easily unsolder the delicate wires from the commutator. (They are quite capable of unsoldering themselves!)

Edited August 14, 2021 by Il Grifone

[Playing trains with kids]

I came across this thread because I had a similar problem a year ago on an 0-6-0 (R1?), (the bright green one with the BR logo - actually I thought mine was an HD model) which seemed odd but I thought nothing more of it, but now my Wrenn N2 (0-6-2) has begun to grind its gear. It is very surprising because the failure is 'catastrophic' (in the technical sense) - no warning and then sudden and almost immediate grinding of the worm gear to shreds. These models came from different sources (on ebay). I am not sure about the suggested failure mechanism, it seems to me like there is continuous wear, and at some point, (possibly with some fatigue mechanism), once the first slip/grind happens, the subsequent grinding is inevitable. I have two questions:

- how successful has replacing the worm been? I am concerned that the worm gear and the axle gear would wear themselves into a set pattern, and therefore maybe the axel gear would not work well with the replacement worm (or may grind it again!)

- Could anyone tell me if the 3-rail Hornby Dublo N2s have the same motor and worm? These are potentially a much cheaper source of a replacement motor

Thanks in advance for your help. Some kids are quite eager for the resurrection of their favourite "steamies"

Edited February 1, 2023 by Playing trains with kids
added last line

[Il Grifone]

The Dublo N2s have a different chassis - the shorter vertical armature with the worm gear as part of the shaft. The Wrenn version (at least the later ones?) uses the same chassis as the R1 0-6-0. Gear stripping is not a problem I've had (excluding my Airfix 14xx!). This sounds like the wheels have seized (?).

These might be useful:

https://www.ebay.co.uk/itm/3143541

https://www.ebay.co.uk/itm/2251398

https://www.ebay.co.uk/itm/3047089

 

Complete reconditioned armatures are available (at a price). Inspection of the gear should reveal any damage; replacements are available.

Edited February 1, 2023 by Il Grifone

[cypherman]

Hi Playing trains with kids,

I never managed to get the worm off. But as I had 2 working motors after getting a replacement armature, I just junked the old armature and put in a spares box for possible future use.

[DCB]

7 hours ago, Playing trains with kids said:

 Could anyone tell me if the 3-rail Hornby Dublo N2s have the same motor and worm? These are potentially a much cheaper source of a replacement motor

The 3 rail H/D N2 chassis is completely different to the Wrenn N2 chassis.   H/D  has a vertical armature  inserted into the chassis with bolt on magnets, Wrenn has a detachable motor.  The worm and axle gears are totally different the H/D a much larger diameter axle gear and the worm is machined into the armature shaft.  The Wrenn N2 chassis is a lengthened version of the H/D 0-6-0 "R1" chassis.  Both share the same wheelbase and wheel size, but nothing on the early H/D 0-6-2 chassis fits the Wrenn 0-6-2 chassis.

 

Working Wrenn and Hornby Dublo 0-6-0 chassis are widely available and cheap. Your  BR Green one sounds like the very common Hornby Dublo version. There were green and black ones in the starter sets and many thousands were sold. I don't think Wrenn did the BR green one.    The 0-6-0s had the 1/2" motor similar to the Triang X04, so similar that I use the same Romford armatures in both, but which had adjustable bearings and a  single start worm.  The same motor was used in the 8F and Castle for a couple of years but overheated in the metal bodies and it was superseded by the Ring Field.   The 0-6-0 tank was the first  and only 2 rail only Hornby Dublo loco.   Previous models had a vertical armature motor, A4, 0-6-2, Duchess, Std 4mt and rear axle drive leaving room for the 3 rail pick up under the chassis. The vertical motors made a return with the G&R Wrenn in the Royal Scot and unrebuilt WC,  and Wrenn used the 0-6-0 chassis with 1/2" motor on their 0-6-2.  The wheels and wheelbase were the same on both anyway.  The 

10 hours ago, Playing trains with kids said:

I came across this thread because I had a similar problem a year ago on an 0-6-0 (R1?), (the bright green one with the BR logo - actually I thought mine was an HD model) which seemed odd but I thought nothing more of it, but now my Wrenn N2 (0-6-2) has begun to grind its gear. It is very surprising because the failure is 'catastrophic' (in the technical sense) - no warning and then sudden and almost immediate grinding of the worm gear to shreds. These models came from different sources (on ebay). I am not sure about the suggested failure mechanism, it seems to me like there is continuous wear, and at some point, (possibly with some fatigue mechanism), once the first slip/grind happens, the subsequent grinding is inevitable. I have two questions:

- how successful has replacing the worm been? I am concerned that the worm gear and the axle gear would wear themselves into a set pattern, and therefore maybe the axel gear would not work well with the replacement worm (or may grind it again!)

I have never seen a failed H/D or Wrenn 0-6-0 worm gear.  Or worm,   I have quite a few, half a dozen runners and the bits of several more, even a brand new unused H/D factory replacement chassis. Even an S15  4-6-0 with an R1 chassis and 22mm Romford wheels, which is very heavily weighted.    I have it in my mind than the axle gears are shiny steel.    May be wrong.    The  gears can potentially disengage if the motor comes loose, it's screwed to the chassis from underneath, or the motor frame screws can come loose, or the bearing play is not adjusted and not oiled and the bearings wear and most common, the axle bushes wear and let the wheels and the gear move sideways. this will lead to the corner of the gear taking the load and initially maybe stripping the corners of the teeth which then fail completely. The later badly made Wrenn vertical motor WC and Scot chassis are particularly prone to this, and eat their misaligned gears unless the chassis is carefully re machined and the gears shimmed to keep them aligned.  .  The  WC gears are unobtainable but 2-6-4T gears fit.  

All H/D and Wrenn and H/D chassis benefit from having their axle gears shimmed to keep them aligned with the worm gear, its much better than shims behind the wheels but every little helps.   The H/D and Wrenn  gears are secured with grub screws, really they need two screws as they run eccentric if the single screw is overtightened.  I think H/D used two screws Wrenn just once again memory is fallible but two screws is better.   If all else fails eBay.   I sold a very nice boxed little used Wrenn R1 for £23.35inc postage recently, so there are plenty out there and not much demand.  The chassis is little use for other models as the  motor sits so far back in the chassis and the wheelbase is so odd,  but mine seem to keep going and going.   Unlike the Wrenn Ring Fields and vertical motors.