Hornby Announce a Re-tooled Class 91 for 2020

[jonnyuk]

just listening to the beyond the buffers pod cast, and guess what the designer mentioned a wobble on some class 91 samples and how he addressed it. 

[cravensdmufan]

6 hours ago, jonnyuk said:

just listening to the beyond the buffers pod cast, and guess what the designer mentioned a wobble on some class 91 samples and how he addressed it. 

 

Interesting to hear the senior designer talking about the development of the Class 91.  He says "the sound is terrific" - from that do we assume a TTS fitted version is coming?  And hopefully the decoder will be available to retro fit these first four releases.  

[Adamphillip]

8 hours ago, jonnyuk said:

just listening to the beyond the buffers pod cast, and guess what the designer mentioned a wobble on some class 91 samples and how he addressed it. 

timestamp?

[cravensdmufan]

5 minutes ago, Adamphillip said:

timestamp?

24:55

[scouse889]

3 hours ago, cravensdmufan said:

 

Interesting to hear the senior designer talking about the development of the Class 91.  He says "the sound is terrific" - from that do we assume a TTS fitted version is coming?

Either that or he was referring to every time it goes over a point! 😂

[GraemeWatson]

On 11/05/2022 at 16:46, WolfofBadenoch said:

 

I replaced the wheels with 12mm Bachmann ones.

 

Attached are photos showing the coupling apparently bent upwards. I've not noticed this before but wondering if it's to do with alot of pushing the carriages?

 

 

 

 

Many thanks for taking the time to reply again, and with photos. It has helped confirm a need to replace the pizza cutter wheels (the new ones are not as cheap to buy now as they used to be!).

 

I've re-wheeled a few of my MKIVs with Hornby 12.6mm wheels and noted a positive effect.

In your last photo, you can see how potentially the MKIV coupling could ride on top of the 91 coupling. In my experience, it has been doing that, and that is potentially implicated in my coach derailment. I ended up putting the slim NEM coupling into the 91 "upside down" and removed the hook. The lower lip on the slim NEM now faces upwards and deflects attempts from the MKIV coupling to over-ride it.

 

The only other problem I have is that on my lead coach behind the 91 I fettled the resin moulded end to the coach (which includes buffers, a prototype not yet made by Hornby) and those of course, get in the way...

 

Edit: I wonder if the better idea would be to replace the Hornby 12.6mm wheels with Bachmann 12mm wheels, lowering the coach height and therefore the likelihood of over-riding?

 

Edited May 12, 2022 by GraemeWatson

[97406]

I’ve sorted the white vertical window frame issue on the 91 as mentioned above. Goodness knows how that passed inspection by Hornby.

 

I thought mine was a bit lumpy over the points, though it seemed to get less as I ran it. Ironically the Heljan 86/3 in the background is butter smooth!  

 

A lovely model nevertheless.

Edited May 13, 2022 by 97406

[WolfofBadenoch]

On 13/05/2022 at 00:54, GraemeWatson said:

 

Many thanks for taking the time to reply again, and with photos. It has helped confirm a need to replace the pizza cutter wheels (the new ones are not as cheap to buy now as they used to be!).

 

I've re-wheeled a few of my MKIVs with Hornby 12.6mm wheels and noted a positive effect.

In your last photo, you can see how potentially the MKIV coupling could ride on top of the 91 coupling. In my experience, it has been doing that, and that is potentially implicated in my coach derailment. I ended up putting the slim NEM coupling into the 91 "upside down" and removed the hook. The lower lip on the slim NEM now faces upwards and deflects attempts from the MKIV coupling to over-ride it.

 

The only other problem I have is that on my lead coach behind the 91 I fettled the resin moulded end to the coach (which includes buffers, a prototype not yet made by Hornby) and those of course, get in the way...

 

Edit: I wonder if the better idea would be to replace the Hornby 12.6mm wheels with Bachmann 12mm wheels, lowering the coach height and therefore the likelihood of over-riding?

 

 

I'm not as knowledgeable or skilled as many on here so it's great to be able to give  some help. Studying my photos i think the couplings have been suffering from being pushed.

[sanspareil]

Still looking at/scratching my head with the running issues with mine. For sure its got to be to do with the restriction in for and aft bogie movement. This has been done to counter the very limited clearance of the dampers to body. Hornby clearly haven't thought the consequences through. Taking the bogie frame off makes no difference (as expected). The only solution i see is to trim done the vertical piece of plastic that by design reduces movement and then trim off some of the damper to give clearance. I am not quite sure how to get the bogie off without damage and am reluctant to do so on brand new £200 model. I am going to add to the weight and write to Hornby on this.

 

Here's a pic of what the limited movement seems to do on plain line straight track, but just off level track. A spirit level shows it to be just off level but something no other loco/unit/carriage/wagon I have has an issue with.

It look likes the right damper is the issue in the pic but its a red herring. Taking off the bogie frame makes no difference. Cleary we can see why there is so much uneven loading on the axles through point work.

 

[adamvb]

6 hours ago, sanspareil said:

Still looking at/scratching my head with the running issues with mine. For sure its got to be to do with the restriction in for and aft bogie movement. This has been done to counter the very limited clearance of the dampers to body. Hornby clearly haven't thought the consequences through. Taking the bogie frame off makes no difference (as expected). The only solution i see is to trim done the vertical piece of plastic that by design reduces movement and then trim off some of the damper to give clearance. I am not quite sure how to get the bogie off without damage and am reluctant to do so on brand new £200 model. I am going to add to the weight and write to Hornby on this.

 

Here's a pic of what the limited movement seems to do on plain line straight track, but just off level track. A spirit level shows it to be just off level but something no other loco/unit/carriage/wagon I have has an issue with.

It look likes the right damper is the issue in the pic but its a red herring. Taking off the bogie frame makes no difference. Cleary we can see why there is so much uneven loading on the axles through point work.

 

 

I'm just writing a similar email to mention the wobble/running and the various livery errors (and cut short lower body at the front which I've just noticed...sigh).

 

I tend to find mine don't deviate quite as much from the track as yours, but they do definitely wobble and "clack" on points to varying degrees. I've also noted they seem to exhibit this less in reverse weirdly...

[cravensdmufan]

Received my 91 002 this morning.

 

Paintwork on loco is absolutely perfect.  @Derails Models tests and checks models before dispatch (great customer service, thanks).

 

Running is slightly lumpy over just one of my Peco Code 100 small radius turnouts in the fiddle yard, but over other turnouts it's fine.  No wobbles.

 

Just one very minor issue.  The coupling at No. 2 end wasn't springing back to centre.  On closer inspection one end of the tiny spring that links with the cam had become unhooked.  Got it back on okay, but quite fiddly -  took a while.

 

Overall, I'm pleased with the loco.

 

[cravensdmufan]

5 hours ago, cravensdmufan said:

Received my 91 002 this morning.

 

Paintwork on loco is absolutely perfect.  @Derails Models tests and checks models before dispatch (great customer service, thanks).

 

Running is slightly lumpy over just one of my Peco Code 100 small radius turnouts in the fiddle yard, but over other turnouts it's fine.  No wobbles.

 

Just one very minor issue.  The coupling at No. 2 end wasn't springing back to centre.  On closer inspection one end of the tiny spring that links with the cam had become unhooked.  Got it back on okay, but quite fiddly -  took a while.

 

Overall, I'm pleased with the loco.

 

A further update.  I fitted a decoder and decided to do a bit more investigation into the lumpy running over points.  I set up a test track on my brand new ply baseboard with a couple of lengths of Peco code 100 flexi track and a medium radius electrofrog point in the middle.  All brand new.

 

You will see from this short video clip that the leading wheel on the No.1 end bogie actually dips into the frog.  The inner wheels don't dip, and the outer wheel on No.2 end bogie dips only slightly.

 

I think this is the cause of the clunking sound and occasional derailment that others have experienced.

 

Maybe the locos run better on Code 75 turnouts with the shallower frog?  Of course it shouldn't make any difference because Hornby's own track is Code 100.  

 

My loco also has a very slight intermittent grinding sound on plain track, but I haven't run it in on the rolling road yet.  I have had similar sounds from other brand new Bachmann and Hornby locos and running in (as advised the manufacturers) usually cures that.

 

Has anyone any further ideas on how to cure the wheel problem?   I haven't!

 

 

[G-BOAF]

Seems, as noted above, that the bogie cannot pivot up and down enough, and is carrying too much weight on the outer wheelsets. These go over the frog and the whole loco dips. If there was better distribution between fore and aft wheels the bogie would not dip over the frog as much I believe. Maybe there is something preventing the up/down movement (actually rocking is more appropriate) of the bogie. I won't be getting one of this first batch, so can't comment in the flesh

[lyneux]

If you've already checked the back to backs then I suspect it is that the tread width is too narrow and the wheel is unsupported over the crossing. The massive flangeway gaps of OO require wide wheel treads to compensate and keep the wheels supported using the wing rail.

 

Try swapping out for another wheelset with wider treads. Or just go EM/P4! 😁

 

Guy

[James90012]

That is shocking for a new model... 

[DavidH]

If the tread was too narrow, wouldn't we expect all the wheels to do it?

 

I'd try swapping the wheelsets around, to see if it's always the front axle or if the problem moves with the wheelset, but my money is still on inconsistent back-to-backs.

 

(I also feel the bogie loading and flexibility could be a red herring for the 'dipping into the point crossing/frog' problem. If the bogie and axles were independently sprung the bogie might drop with the wheelset, but the wheel dropping problem would still be there? Solve that first before cutting into the plastic to deal with the next issue.)

 

9 hours ago, lyneux said:

Try swapping out for another wheelset with wider treads. Or just go EM/P4!

I have EM wheels fitted to 00 axles* that don't behave that badly on commercial points (used in my fiddle yard).

 

(*Wagons with Gibson and Keen wheels)

Edited May 19, 2022 by DavidH

[Patriot87003]

How does the wheelset face to face measurement compare with other stock?

 

If Hornby have used a finer flange depth, or a thinner tread width, or a combination of both, then a slightly wider back to back measurement maybe required to maintain continuous contact with the crossing and wing rails when traversing points. 
 

[Legend]

14 hours ago, cravensdmufan said:

A further update.  I fitted a decoder and decided to do a bit more investigation into the lumpy running over points.  I set up a test track on my brand new ply baseboard with a couple of lengths of Peco code 100 flexi track and a medium radius electrofrog point in the middle.  All brand new.

 

You will see from this short video clip that the leading wheel on the No.1 end bogie actually dips into the frog.  The inner wheels don't dip, and the outer wheel on No.2 end bogie dips only slightly.

 

I think this is the cause of the clunking sound and occasional derailment that others have experienced.

 

Maybe the locos run better on Code 75 turnouts with the shallower frog?  Of course it shouldn't make any difference because Hornby's own track is Code 100.  

 

My loco also has a very slight intermittent grinding sound on plain track, but I haven't run it in on the rolling road yet.  I have had similar sounds from other brand new Bachmann and Hornby locos and running in (as advised the manufacturers) usually cures that.

 

Has anyone any further ideas on how to cure the wheel problem?   I haven't!

 

 

 

Very interesting . Looks like you have demonstrated the issue very well .  

[PaulRhB]

 

I put mine on a flat sheet, see ruler under frame, on some 1mm shims. The inner wheels don’t touch the board. 
 

so I tried the same on the inner wheels,

 

 

the outer wheels don’t drop any further by eye though, still daylight under the flanges. 
 

The outer wheels won’t go up or down although there is limited movement up to the body on the inners that allows the front to drop in a fraction more I guess. It’s a bit odd. 
 

 

Effectively the bogie is pivoting around the outer axle so it takes most of the weight hence it drops into any gap hard. The inner axle is taking virtually no weight so I guess occasionally it’s either hitting the frog at a funny angle hard and bouncing off or a minor issue with b2b is exacerbated by it?

Edited May 19, 2022 by PaulRhB

[DavidH]

I don't know, I don't have the model, but my hunch would be that that should only cause an issue on a sharp transition to an incline. Not on a flat(tish) point.

Have you swapped the wheelsets round to see if it happens to all of them (assuming they drop out like Hornby D&E locos used to)?

Are the B2Bs consistent - but if they are, try widening the B2B on the leading axle to se what happens.

I have BILs and HALs where one wouldn't go through a particular point frog, and swapping the wheels with one that did, stopped the derailment. It's often the wheels, before any other issue.

Apologies, this isn't meant to be patronising - I'm almost certainly stating the obvious!

[dj_crisp]

This is interesting... The only other loco i have that has similar characteristic is Dapols 73 - which has a weird bogie setup that seems similar to how the 91 is looking. I've never tried it on OO track and never been happy with it's running over wonky or "hilly" track ... fine over the hill but rubbish in the dips. It's sitting in my one to resolve one day pile

[cravensdmufan]

1 hour ago, PaulRhB said:

 

I put mine on a flat sheet, see ruler under frame, on some 1mm shims. The inner wheels don’t touch the board. 
 

so I tried the same on the inner wheels,

 

 

the outer wheels don’t drop any further by eye though, still daylight under the flanges. 
 

The outer wheels won’t go up or down although there is limited movement up to the body on the inners that allows the front to drop in a fraction more I guess. It’s a bit odd. 
 

 

Effectively the bogie is pivoting around the outer axle so it takes most of the weight hence it drops into any gap hard. The inner axle is taking virtually no weight so I guess occasionally it’s either hitting the frog at a funny angle hard and bouncing off or a minor issue with b2b is exacerbated by it?

That's a good bit of research, thanks.

 

I'm wondering if we have another situation similar to that of the problem with some Bachmann 6 wheeled diesel bogies a few years ago (there was a lot of discussion on that at the time here on RMw) where it was found that the centre axle wheelset sat lower than the outer two resulting in intermittent loss of rail contact and derailing on points.  The cure was to file a fraction off  the plastic where the brass axle holders clipped in (file down just the centre axle ones).  I had to do this with a number of my 37s and 47's, just taking a tiny bit off at a time until the wheels were all level - the trick was to put the loco on a piece of glass to ensure all the flanges were touching the flat surface and the bogie didn't rock.  All were cured of the problem.

 

I'm tempted to try this eventually with my 91, but only as a last resort.  In the meantime I will check all b-t-b's  and swap axles around as has been suggested.  Naturally surgery would invalidate the warranty, but I really love this loco.  Such problems shouldn't occur on £200 products.

Edited May 19, 2022 by cravensdmufan

[cravensdmufan]

Update on the Class 91:

 

Well I checked the back to backs with my gauge block and also with the digital caliper – all the same at 14.5mm.

 

The wheel treads and flanges are the same dimensions as other Hornby and Bachmann rolling stock wheels which don't sink deep into the turnout frog. But they do seem slimmer than on other locos – but I haven't checked that yet.

 

So I took a Class 91 wheelset out and freewheeled it through the frog a few times – it didn't sink or derail! So I figured the problem must be the depth of the outer axle compared to the inner axle (even though they are mounted identically) the weight of the loco causing the bogie to become very slightly imbalanced.

 

Despite thinking I may do it in the future as a last resort, curiosity got the better of me and I decided to wield a small round file to the u shaped piece that houses the brass axle holders on the outer end only of No.1 end (the worst wheels for dipping), filing a tiny bit of the plastic away.

 

It seems to have cured the problem. The loco no longer drops right down into the frog – it still goes down very slightly but no more than some of my other locos. I didn't want to file too much away, and I had to be really careful not to let the file near the plastic cog. My heart sank after my initial attempt as the loco wobbled slightly on the move, but then I checked again and spotted I hadn't filed evenly on both sides. It's a matter of trial and error.

 

So although I'm pleased with the result - much quieter and smoother over the points - I didn't attempt the other bogie's outer axle which wasn't so bad. I was afraid of ending up with a wobbling or leaning loco.

 

 

[andyman7]

On 18/05/2022 at 13:18, cravensdmufan said:

Received my 91 002 this morning.

 

Paintwork on loco is absolutely perfect.  @Derails Models tests and checks models before dispatch (great customer service, thanks).

 

Running is slightly lumpy over just one of my Peco Code 100 small radius turnouts in the fiddle yard, but over other turnouts it's fine.  No wobbles.

 

Just one very minor issue.  The coupling at No. 2 end wasn't springing back to centre.  On closer inspection one end of the tiny spring that links with the cam had become unhooked.  Got it back on okay, but quite fiddly -  took a while.

 

Overall, I'm pleased with the loco.

 

I had exactly the same issue with a Bachmann Class 90, the springs for the self-centring couplers are fiddly but with care can be re-seated 

[andyman7]

1 hour ago, cravensdmufan said:

Update on the Class 91:

 

Well I checked the back to backs with my gauge block and also with the digital caliper – all the same at 14.5mm.

 

The wheel treads and flanges are the same dimensions as other Hornby and Bachmann rolling stock wheels which don't sink deep into the turnout frog. But they do seem slimmer than on other locos – but I haven't checked that yet.

 

So I took a Class 91 wheelset out and freewheeled it through the frog a few times – it didn't sink or derail! So I figured the problem must be the depth of the outer axle compared to the inner axle (even though they are mounted identically) the weight of the loco causing the bogie to become very slightly imbalanced.

 

Despite thinking I may do it in the future as a last resort, curiosity got the better of me and I decided to wield a small round file to the u shaped piece that houses the brass axle holders on the outer end only of No.1 end (the worst wheels for dipping), filing a tiny bit of the plastic away.

 

It seems to have cured the problem. The loco no longer drops right down into the frog – it still goes down very slightly but no more than some of my other locos. I didn't want to file too much away, and I had to be really careful not to let the file near the plastic cog. My heart sank after my initial attempt as the loco wobbled slightly on the move, but then I checked again and spotted I hadn't filed evenly on both sides. It's a matter of trial and error.

 

So although I'm pleased with the result - much quieter and smoother over the points - I didn't attempt the other bogie's outer axle which wasn't so bad. I was afraid of ending up with a wobbling or leaning loco.

 

 

Really useful investigation. Essentially, what we are dealing with is a slight shortcoming in the amount of 'slop' or 'float' that an RTR model needs in place of the compensation that a finescale P4 or similar model would have.

I know it's frustrating that this occurs but the measures here suggest that the fix is relatively straightforward and that potentially if future batches are modified the parts might me made available to update the first batch.