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OO gauge GWR Mogul and Prairie


Paul.Uni
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7 hours ago, St Enodoc said:

 

My experiences led me to the conclusion that the problem is the cam pivot not self-centring properly, not the wheels. As mine derails only (but always) in one place, where nothing else has a problem, I have banned it from that section of track. Everywhere else it is fine.

Our derailment was on a 30" ish radius curve on the down main so a ban on down trains is a bit impractical.   I didn't think of the cam, but when placed on new code 100 peco track with one flange hard against the rail head the tyre on the other wheel is barely hanging on to the rail, it's like on 25% of the rail head.   Normally one can adjust the B to B but with the Dapol split axle it's not easy.   My Triang M7 has the same axle set up and it took ages to get the B to B right as I had to start with it wide and carefully file the axle stubs until it was right, when I cocked it up and filed too much off I had to find another wheel and stub axle and start again, the Dapol is too narrow.  Plan B is Hornby wheels, plan C is Super glue down the Dapol axle muff to space the wheels out more, plan C (i) reprofile the Dapol tyres,  Plan D is check out the cam, and Plan E is fit a decent front coupling so it can actually push trains without derailing the pony truck.  Just about every loco I have ever bought has needed a re engineered front coupling so I'm not criticising Dapol for that.   

Top speed is probably a DCC thing, mine needs to cruise at 60 or 30 or start at the same voltage as Triang. most Hornby most Bachmann etc as I do a lot of double heading and banking

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2 minutes ago, DavidCBroad said:

Our derailment was on a 30" ish radius curve on the down main so a ban on down trains is a bit impractical.   I didn't think of the cam, but when placed on new code 100 peco track with one flange hard against the rail head the tyre on the other wheel is barely hanging on to the rail, it's like on 25% of the rail head.   Normally one can adjust the B to B but with the Dapol split axle it's not easy.   My Triang M7 has the same axle set up and it took ages to get the B to B right as I had to start with it wide and carefully file the axle stubs until it was right, when I cocked it up and filed too much off I had to find another wheel and stub axle and start again, the Dapol is too narrow.  Plan B is Hornby wheels, plan C is Super glue down the Dapol axle muff to space the wheels out more, plan C (i) reprofile the Dapol tyres,  Plan D is check out the cam, and Plan E is fit a decent front coupling so it can actually push trains without derailing the pony truck.  Just about every loco I have ever bought has needed a re engineered front coupling so I'm not criticising Dapol for that.   

Top speed is probably a DCC thing, mine needs to cruise at 60 or 30 or start at the same voltage as Triang. most Hornby most Bachmann etc as I do a lot of double heading and banking

Mine derails when running chimney first off a right-hand 30" curve through the straight road of a double slip. On the curve the pony is of course pushed to the right and it doesn't centre itself completely, so it's still displaced to the right when it enters the slip. The straight road is effectively unchecked at the elbows (K-crossing) and it takes the wrong road. I tried some Gibson wheels at various back-to-back settings but that made no difference so I reverted to the Dapol wheels, which on my example are 14.5mm BTB.

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4 hours ago, melmerby said:

More like 120 on mine!

Way too fast. The decoder needed Vtop to be reduced to 140 to get a normal top speed of around 70.

Others have also commented on the over high top speed.

AFAIK no revised gearing models out yet.

Apparently slow speed controllability is satisfactory according to the reviews, and the obvious solution is to not drive fast (!), but if the top speed is high, it would annoy me because, if the gearing were more suitable, then the slow speed controllability would be improved as well.  Moreover, it is an indication of poor design on Dapol's part (of course, we don't know the full story, perhaps a differenc motor to the original spec had to be used and nobody bothered to alter the gearing, not that that's an excuse but it might be a reason), a really basic mistake, and if they are capable of this sort of fundamental error why would I trust them or give them my money?

 

I'm out of the game as far as moguls go but my shopping list for prairies is not yet complete; see below...  As Dap will sell running chassis, I might consider one to upgrade an older Hornby with as well, after the gearing upgrade.

 

4 hours ago, boxbrownie said:

I vowed never to buy another Dapol product, it might be a bit of “cut nose to spite face” but I felt very strongly about it.

 

Poor customer service is what the 'cut nose  to spite face' in this situation is, and Dap are the nose cutters with the face.  Inexcusable; it cannot be good practice to upset the people who are giving you money.   I have come to the same decision with Ratio kits, but in this case it is because of the very poor quality of parts and near impossibility of constructing them to the instructions.  Dapol, as I say, are in the 'suspicious' category; I would be happy to buy wagon or van bodies, for example, from them but would need a lot of re-assurance from reviewers before I opened my wallet for anything like a locomotive.  That might be modified if something I particularly wanted was available at a reasonable price, and the possibility is the Collett 31xx.  This would, if ever produced by Dap, presumably benefit from the gearing redesign.

 

The other vague hope I have from Dapol, and my theory is that if I keep banging on about it here and Dap read it so that it is somewhere in their collective conciousness, so pardon the blatant wishlisting please, is that they will put the ex Lionheart Diagram N auto trailer through a 7-4mm scale shrink ray.  One day, maybe, maybe even before I kick it.

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I ordered a new Mogul and it arrived this morning, with two of the buffers floating around in the box. At least the buffers were easy to put back where they should have been - but that ease was probably how they became detached in transit in the first place!

 

Running it in gave me a more positive view of the model. It looks nice and runs very nicely and quietly too, although the gearing is far from perfect. The tender coupling is a joy to use too, much easier than dealing with other models' tenders.
Unfortunately, I hooked it up to a train and found that it couldn't pull the skin off a rice pudding - the moment it reached a small incline it slipped to a stop. I thought that the Hornby large prairie was a bit gutless, but that made mincemeat of the same hill with the same train! The only model in my fleet that struggles more with such a train is an Andrew Barclay, which is certainly excusable given its small size.

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Hi Matt

The tender coupling is indeed "a joy to use" but at least one poster has pointed out that after several unplug and plugs it became sloppy and would not stay together when pulling a train.

I too am concerned about it's durability.

 

Mine will pull 6 Bachmann (ex Mainline) coaches up a 1:100 incline where it slows down noticeably. If it stops on the incline it it can't start again, it just spins the wheels.

If I put a lead saddle over the boiler to add some extra weight, it still slows down but will start again on the incline, albeit slowly

 

Pulling power IMHO is poor for it's size as there is not enough mass in the boiler region and the motor seems underpowered.

The same haulage comments apply to the Hornby prairie although it is better than the mogul.

No other tender loco I have is this poor and most tank engines, such as a Bachmann 57XX. manage it with ease.

 

Why can't manufacturers use a more powerful motor and more mass?:scratchhead:

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9 hours ago, melmerby said:

Hi Matt

The tender coupling is indeed "a joy to use" but at least one poster has pointed out that after several unplug and plugs it became sloppy and would not stay together when pulling a train.

I too am concerned about it's durability.

 

Mine will pull 6 Bachmann (ex Mainline) coaches up a 1:100 incline where it slows down noticeably. If it stops on the incline it it can't start again, it just spins the wheels.

If I put a lead saddle over the boiler to add some extra weight, it still slows down but will start again on the incline, albeit slowly

 

Pulling power IMHO is poor for it's size as there is not enough mass in the boiler region and the motor seems underpowered.

The same haulage comments apply to the Hornby prairie although it is better than the mogul.

No other tender loco I have is this poor and most tank engines, such as a Bachmann 57XX. manage it with ease.

 

Why can't manufacturers use a more powerful motor and more mass?:scratchhead:

Perennial problem.  DCC modellers rightly demand all sorts of electronic jiggery pokery, and the space inside a steam outline model is limited if daylight is to be visible where it should be and full cab detail included, both of which put constraints on the size, and thus power, of the motor and the amount of ballast that can be put in above the driving wheels where it is needed.   
 

I know you are fully aware of this and am not trying to do the thing with grannies and eggs, but point this out as useful to newcomers to the situation.  Plastic bodies add nothing useful to the mix, and sadly some designs do not exploit the space available to the best possible advantage.  My practice is to cram in as much ballast as I can manage, using whatever suitable material I can lay my hands on, and, as my layout is DC, replacing the chip holders with something heavier; every little helps.  
 

The alternatives are tender drive and/or traction tyres; no thanks. 
 

There may be some advantage to playing the long game, Matt.  All of my brand new locos have improved beyond whatever I could achieve by adding ballast over time, for what I suspect may be several reasons.  The increase in traction of Bachmann driving wheels as the smooth plated tyre surface wears over time and be omes rougher, gripping the railhead better, is well known, and presumably occurs to some extent on all locos, and the general bedding in and loosening up of mechanical components that begins with running in lessens the friction and drag that saps motor power and gear efficiency.  It is also possible that wear helps chassis to be more easily flexible and to ‘sit’ better on the track, enabling the motor and gears to deliver the power to the railhead with less loss, and for pickup to be improved, meaning that power to the motor is less likely to be interrupted for even very short periods.  All pf this will be reflected on better haulage and performance as a whole. 
 

My Hornby W4 Peckett is tasked with hauling 11-wagon coal trains, mixed rakes of  7 plankers and 16 & 21 tonners.  The loaded train has real coal on top of card infills.  When new, the loco could manage the empties with careful driving and some slipping, and the loaded train had to be split into 3 portions as 4 loaded was the best she could do, the problem spot being a no.3 curve at the fiddle yard throat.  After a year of almost daily use, she can manage both sets coupled together with careful handling, and manages the complete rake of loaded with ease. 
 

Perhaps your Mogul will manage better in time, not that this will alleviate your current disappointment.  Hang in there!

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19 hours ago, melmerby said:

Pulling power IMHO is poor for it's size as there is not enough mass in the boiler region and the motor seems underpowered.

 

This also goes back to the poor gearing choice. The lower the gearing, the more the motor torque is multiplied at the wheels, and hence potential haulage power increases.

Edited by 57xx
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38 minutes ago, Butler Henderson said:

No reason for DCC matters to take up space in the loco body of a tender loco as it can all go on the tender. Dapol however think the idea of  he who is not mentioned these days to put the decoder behind a removable smokebox door is a good one:angry:

I can see why the DCC gubbins isn’t in the tender on this loco, though, as Dap are in the business of making a standard mech that can be used in prairies as well to cut costs.  Decoders behind removable smokebox doors where you can get at them without taking the top off are not the worst of The Unmentionable’s ideas, though they do mean extra lengths of vulnerable wiring and, again, compromised ballast provision.  

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8 hours ago, The Johnster said:

.....There may be some advantage to playing the long game, Matt.  All of my brand new locos have improved beyond whatever I could achieve by adding ballast over time,....

 

Perhaps your Mogul will manage better in time, not that this will alleviate your current disappointment.  Hang in there!

All my engines have got miles better and some with a few 'running in sessions' lasting 2hrs in each direction at about 50% speed. cept my King Richard III which can't manage 8 cars round a 2 & 3/4 curve and grinds to a halt at 18inches in.

 

56 minutes ago, Butler Henderson said:

 ......he who is not mentioned these days.... .

Who?

 

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5 hours ago, The Johnster said:

I can see why the DCC gubbins isn’t in the tender on this loco, though, as Dap are in the business of making a standard mech that can be used in prairies as well to cut costs.  Decoders behind removable smokebox doors where you can get at them without taking the top off are not the worst of The Unmentionable’s ideas, though they do mean extra lengths of vulnerable wiring and, again, compromised ballast provision.  

Good point.

 

Remember that the mogul has a cast metal running plate to give more mass than a traditional all-plastic bodied model. (If you look inside there really isn't room for any more ballast except for the smokebox where the decoder gubbins lives.)

 

The point about waiting for the tyres to wear-in a bit is also a good one.

 

Dapol clearly had to make some very finely balanced design decisions for this and the related locos and on the whole I think they've done a good job. Not perfect but then nothing ever is - and the next revision will be even better.

 

Edited by Harlequin
Smokebox - not Firebox! Duh!
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10 hours ago, The Johnster said:

Perennial problem.  DCC modellers rightly demand all sorts of electronic jiggery pokery, and the space inside a steam outline model is limited if daylight is to be visible where it should be and full cab detail included, both of which put constraints on the size, and thus power, of the motor and the amount of ballast that can be put in above the driving wheels where it is needed.   
 

I know you are fully aware of this and am not trying to do the thing with grannies and eggs, but point this out as useful to newcomers to the situation.  Plastic bodies add nothing useful to the mix, and sadly some designs do not exploit the space available to the best possible advantage.  My practice is to cram in as much ballast as I can manage, using whatever suitable material I can lay my hands on, and, as my layout is DC, replacing the chip holders with something heavier; every little helps.  
 

The alternatives are tender drive and/or traction tyres; no thanks. 
 

There may be some advantage to playing the long game, Matt.  All of my brand new locos have improved beyond whatever I could achieve by adding ballast over time, for what I suspect may be several reasons.  The increase in traction of Bachmann driving wheels as the smooth plated tyre surface wears over time and be omes rougher, gripping the railhead better, is well known, and presumably occurs to some extent on all locos, and the general bedding in and loosening up of mechanical components that begins with running in lessens the friction and drag that saps motor power and gear efficiency.  It is also possible that wear helps chassis to be more easily flexible and to ‘sit’ better on the track, enabling the motor and gears to deliver the power to the railhead with less loss, and for pickup to be improved, meaning that power to the motor is less likely to be interrupted for even very short periods.  All pf this will be reflected on better haulage and performance as a whole. 
 

My Hornby W4 Peckett is tasked with hauling 11-wagon coal trains, mixed rakes of  7 plankers and 16 & 21 tonners.  The loaded train has real coal on top of card infills.  When new, the loco could manage the empties with careful driving and some slipping, and the loaded train had to be split into 3 portions as 4 loaded was the best she could do, the problem spot being a no.3 curve at the fiddle yard throat.  After a year of almost daily use, she can manage both sets coupled together with careful handling, and manages the complete rake of loaded with ease. 
 

Perhaps your Mogul will manage better in time, not that this will alleviate your current disappointment.  Hang in there!

Dear The Johnster

I  found your  thoughtful and considered analysis to be absolutely spot on .Well said .

My Bachman 56xx displays all of the benefits you note of extended use but I had missed the point of tyres wearing in . I’ve long believed that machinery beds in .

Ken 

 

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3 hours ago, Harlequin said:

Good point.

 

Remember that the mogul has a cast metal running plate to give more mass than a traditional all-plastic bodied model. (If you look inside there really isn't room for any more ballast except for the firebox where the decoder gubbins lives.)

 

 

 

Maybe they should have also done a cast boiler as per several of Hornby's smaller/lighter locos?

 

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The more cast metal is used the better from this point of view, but this is a decision for production engineers who will be influenced by the cost effectiveness of the production process, material cost not being the major issue here but 'how many processes are needed to assemble the model and how long does it take'?  Hornby's new 78xxx has a diecast boiler and running plate IIRC, so it can be done, but there may well be good reasons for H going down that road with their model and Dap not with the Mogul that we are not party to. 

 

The big lost opportunity with the Dap mogul is clearly the gearing, a rookie mistake but as I suggested in an earlier post maybe the result of a change of motor supplier and not adjusting the gearing to account for a fast revving motor, which is a possible explanation not an excuse!  Some models run well despite this, which suggests a mechanically efficient drive train, but one vulnerable to being upset by minor maladjuctments of the sort that are difficult to isolate and fix.  To be fair, Dap are addressing the issue which should resolve this particular issue, and also provide an increase in tractive effort that will not be unwelcome.

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1 hour ago, The Johnster said:

 Hornby's new 78xxx has a diecast boiler and running plate IIRC, so it can be done, but there may well be good reasons for H going down that road with their model and Dap not with the Mogul that we are not party to. 


?? Have I missed something

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1 hour ago, The Johnster said:

...  Hornby's new 78xxx has a diecast boiler and running plate IIRC,...

Should that be Accurascale?

 

4 hours ago, The Johnster said:

A brief history of Dapol and DJM will clear matters up for you, Butler. 

Could'nt find a connection but unimportant,  realise who is DJM.

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13 hours ago, Butler Henderson said:

No reason for DCC matters to take up space in the loco body of a tender loco as it can all go on the tender. Dapol however think the idea of  he who is not mentioned these days to put the decoder behind a removable smokebox door is a good one:angry:

 

I understand the idea originated with Andy Forty, and only the opening door and use of the space was adopted by DJModels, despite the idea of the sliding tray being discussed at that time....

 

Les

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On 06/04/2021 at 12:42, St Enodoc said:

Mine derails when running chimney first off a right-hand 30" curve through the straight road of a double slip. On the curve the pony is of course pushed to the right and it doesn't centre itself completely, so it's still displaced to the right when it enters the slip. The straight road is effectively unchecked at the elbows (K-crossing) and it takes the wrong road. I tried some Gibson wheels at various back-to-back settings but that made no difference so I reverted to the Dapol wheels, which on my example are 14.5mm BTB.

I swapped the Wrenn wheels for Hornby wagon wheels with the pin-points filed off,  With aB to B between 14.2 and 14.5 the go/ no go limitsbon my gauge these cured the derailments. My Dapol wheels are also more than 14.2 and less than 14.5mm B to B but  actually drop in on a one place on a curve.

It's not so much the B to B as the very thin flange, the Hornby flange is noticeably thicker and for the same B to B the Hornby has 0.5mm or more tyre on the opposite rail despite being about the same overall width.   I did try re profiling the Dapol tyres but they still derailed,

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This is going to sound somewhat controversial, but, it happens on the big railway as well. 

 

If you've got an unchecked rail , and a locomotive derails on  it , doesn't that tell you something? .......... ' Unchecked rail'....... That is why we used to call in the P.Way people, to install a check rail.  Check rails are bespoke; they can & do vary in length. Anything from 12', up to anything that a check rail is required.  If the loco was derailing on straight track, then your concern is- would be, completely justified.  If it's a localised problem, then deal with it at a localised level.  On a more possible serious problem, modifying the model may well preclude said model from working over  a larger portion of the layout.  Operating machinery (any scale/gauge ) outside of its design parameters will sometimes result in disappointment. If you peruse Youtube, you will see a Deltic spreading some points on the North Norfolk Railway.  We dropped a class 37 on the P&B  because of poor pointwork. 105 tons, mind.....

 

..... Unchecked rail.......

Edited by tomparryharry
Poor grammar on my part.
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