OO gauge GWR Mogul and Prairie

[tomparryharry]

2 minutes ago, melmerby said:

The M7 has a very uneven weight distribution due to the wheel arrangement, take the rear truck away and the back end will hit the deck.

Their later 0-4-4T H class is much, much better with an improved, but still not ideal weight ditribution.

A little experimentation with a  small, light, spring on the centre of the  rear bogie of an M7 might well cure the problem. 

[rembrow]

I've tested mine through 3rd radius points and have had no problems  forward or reverse. I'm using dc operation. The rear bogie is free moving left, right and up, down. The springs in the rear pony are fairly light in tension so there is no real resistence. 

Edited December 5, 2021 by rembrow
Addition

[Ian Hargrave]

25 minutes ago, rembrow said:

I've tested mine through 3rd radius points and have had no problems  forward or reverse. I'm using dc operation. The rear bogie is free moving left, right and up, down. The springs in the rear pony are fairly light in tension so there is no real resistence. 

So the issue is not universal.Useful to know . 

[Ian Hargrave]

Might the position of the keeper plate in relation to the pick ups have a bearing on it.Too tight/loose ? Or isn’t that possible ?

[The Johnster]

6 hours ago, Harlequin said:

Here's the rear pony disassembled:

 

You can see the springs. I am going to leave them in for the moment but the reason for taking it apart was to fit some nylon washers to reduce the sideplay of the axle in the pony truck. Since the pony truck rotates I don't see the need for the axle to also have a lot of side to side freedom and I think it's causing the rear coupling to be off-centre.

 

I had a similar  sort of problem with a Hornby China 2721 (generic Jinty) chassis. noughties vintage I think, which had a sprung rear axle with two springs that sat in recesses in the underside of the chassis block and bore directly downwards onto the axle, no bearing plate.  I couldn't understand such a poor piece of engineering and downloaded the service parts sheet (loco was a cheapo 2h sold 'as seen'), but this was the design as intended.  The service sheet suggested that one might be able to increase the springs' downforce by stretching them by hand, or reduce it by trimming the ends down.  Now. this chassis had all sorts of problems of which this was only one and I eventually got it to run reasonably well compared to the 3-legged dog with 3 different legs that I'd originally taken a punt on, but 'reasonably well' was not good enough for my standards and I eventually stopped wasting time and effort on it and replaced it with a Bachmann.

 

Anyway, back to the twin springs, they were lifting the rear of the loco to the extent that the rear wheels were off the railhead and pickup performance was thus compromised, and when I provided pickups on the centre drivers as well, having replaced them with wheels from the scrapbox that did not have traction tyres, these were lifted clear of the railhead as well.  Having tried running the loco without the springs, which gave a performance half way between 3 legged dog and just plain dog, I trimmed them 'one coil at a time' until, after trimming 3 coils, the wheels sat on the railhead and pickup was pretty good.  I also emery-ed down the rough cut ends where I'd trimmed them and provided a brass bearing plate soldered to the ends and lightly lubricated, all of which provided incremental improvements to the slow running performance, but I never got her to start or stop smoothly (DC).  She runs beautifully on her Bachmann 57xx chassis, as do all my Bachmanns.

 

Some of this saga may be of use to people who want to try to improve the pickup performance of the Dap prairie, or a Hornby generic Jintychassis, or a Hornby 0-4-4.

[rembrow]

I've looked at the rear pony truck and initially, I was surprised that the wheelset didn't have as much free rotation as I would expect. Unlike the front pony truck, the springing for the rear pony is on the axle, rather than the truck, so I'm wondering if this could be causing the problem, if the pressure on the axle is too much, in some cases, restricting rotation and leading to issues on points. I also found that the rear pony axle, when the whole wheelbase is on the rail, or on a flat surface, is fully depressed and the pony truck top is against the cab floor, giving no further upward movement. I can see that if the pony wheels are pushed up, there is no play to stop the chassis lifting. What I've done is twofold. Having seperated the pony truck by the two screws, I've removed the springs and reduced their length by a quarter. This relieves the pressure on the axle. I've slightly extended the half circular end of the axle locating slot, with a round file, to give more up and down movement of the axle, particularly when the wheelsets are down on the track. I may have to lengthen the slot more, but it has given the wheelset more free rotation and there is some upward movement ability, when the wheels are on the track, so it should now be able to handle the upward movement on some points  without lifting the driving wheels. From what I've found  the loco may have problems in tackling gradients while in reverse, due to the lack of upward movement available in the rear truck wheelset  unless the axle and truck are modified.

Addition. I've now successfully tested the modification on a created incline.

Edited December 5, 2021 by rembrow
Correction

[Ian Hargrave]

Hopefully,Dapol’s design team are working on a diagnosis and remedy. A recall.  as such is problematic .

[B10M]

I have since found this which is rather helpful if experiencing stall issues, informative description too so I take my hat off to the gent for going into so much detail to assist...

https://youtu.be/wJohLL7K-u8

 

 

 

[boxbrownie]

10 hours ago, B10M said:

I have since found this which is rather helpful if experiencing stall issues, informative description too so I take my hat off to the gent for going into so much detail to assist...

https://youtu.be/wJohLL7K-u8

 

 

 

It is very noticeable that once the rear pony truck is removed the rear driver set drop significantly going over the frog gap, before it seemed to be smooth…..so yes the rear pony is taking a lot of the weight, too much it appears.

[Guest]

10 hours ago, B10M said:

I have since found this which is rather helpful if experiencing stall issues, informative description too so I take my hat off to the gent for going into so much detail to assist...

https://youtu.be/wJohLL7K-u8

Very good video, but end of day one shouldn't have to do all this.  I shan't be getting one if I've got to faff around to rectify possible proper design fault.  I'll just get the Baccy small prairie instead as I had been holding back to see what the Dapol one was like.  Shame.

 

I only have one loco that didn't run properly (and still doesn't) and thats my King Rich III, it jerks to a stop with a clicking noise, motor out spins fine down to a stop, chassis freewheeling, back together same, above stopping and starting fine. Not sent back as was a 2020 Xmas present and didn't have heart to ask giver for receipt to send back, so took apart.

 

For what its worth my nearest proper model railway shop 50ml round trip, won't sell Dapol due to QC issues they had with their last batch of OO class 73's - wheel sets falling out and or driveshafts not fitted - and loads of different issues with 122 Bubble car, and a nearer general model shop, won't stock Dapol either now, they will just keep Bachmann once their few remaining Hornby items are gone.!

Edited December 6, 2021 by Guest

[boxbrownie]

37 minutes ago, confused said:

Very good video, but end of day one shouldn't have to do all this.  I shan't be getting one if I've got to faff around to rectify possible proper design fault.  I'll just get the Baccy small prairie instead as I had been holding back to see what the Dapol one was like.  Shame.

 

I only have one loco that didn't run properly (and still doesn't) and thats my King Rich III, it jerks to a stop with a clicking noise, motor out spins fine down to a stop, chassis freewheeling, back together same, above stopping and starting fine. Not sent back as was a 2020 Xmas present and didn't have heart to ask giver for receipt to send back, so took apart.

 

For what its worth my nearest proper model railway shop 50ml round trip, won't sell Dapol due to QC issues they had with their last batch of OO class 73's - wheel sets falling out and or driveshafts not fitted - and loads of different issues with 122 Bubble car, and a nearer general model shop, won't stock Dapol either now, they will just keep Bachmann once their few remaining Hornby items are gone.!

I was disappointed the video didn’t actually show us what he did with the pony truck just an description showing the standard assembly (unless I missed something)….I got the gist I think.

Edited December 6, 2021 by boxbrownie

[Harlequin]

11 hours ago, B10M said:

I have since found this which is rather helpful if experiencing stall issues, informative description too so I take my hat off to the gent for going into so much detail to assist...

https://youtu.be/wJohLL7K-u8

 

 

 

Very interesting. And interesting that I didn't see this problem. I guess my track is similar to Dapol's test track...

 

Actually, I've just remembered I do have some ugly Hornby Code100 Settrack for my Christmas tree layout - maybe that would be an interesting test!

 

[boxbrownie]

33 minutes ago, Harlequin said:

Very interesting. And interesting that I didn't see this problem. I guess my track is similar to Dapol's test track...

 

Actually, I've just remembered I do have some ugly Hornby Code100 Settrack for my Christmas tree layout - maybe that would be an interesting test!

 

During the recent Hornby television series their “test track” consisted it appeared of nothing but set track, and they have a torturous (their words) through several reverse curve small radius points, hopefully Dapol would do the same level of testing.

[melmerby]

46 minutes ago, boxbrownie said:

I was disappointed the video didn’t actually show us what he did with the pony truck just an description showing the standard assembly (unless I missed something)….I got the gist I think.

He flattened the moulding and left the springs out when re-assembling.

I'm surprised that at the speed it was going the flywheel didn't carry the loco over the problem point. It suggests the flywheel isn't very effective.

I also noticed it now drops as it goes over the frogs etc. after the fix. Not good.

 

 

Edited December 6, 2021 by melmerby

[boxbrownie]

7 minutes ago, melmerby said:

He flattened the moulding and left the springs out when re-assembling.

I'm surprised that at the speed it was going the flywheel didn't carry the loco over the problem point. It suggests the flywheel isn't very effective.

I also noticed it now drops as it goes over the frogs etc. after the fix. Not good.

 

 

I noticed that also, I think the better solution might be just to “adjust” if possible the spring tension until it’s a balance between the two extremes.

[boxbrownie]

Actually thinking about the solution he came up with, I assume the rear coupling is attached the the pony truck? Surely then if he flattened the grooves and removes the springs which effectively lowers the truck the coupling would be a bit low as well?

[melmerby]

9 minutes ago, boxbrownie said:

I noticed that also, I think the better solution might be just to “adjust” if possible the spring tension until it’s a balance between the two extremes.

Why does it need any compensation?

It should run as an 0-6-0 with the trucks having no effect on the weight distribution, a driving wheel shouldn't drop into those gaps.

The vast majority of my tank locos with leading or trailing wheels have no springing at all and dont do it.

 

Edit

Those that have springing have just enough the keep the wheels on the track, they shouldn't be compensating for poor weight distribution on a 2-6-2

Edited December 6, 2021 by melmerby

[Mallard60022]

Apologies. Someone that might know and link me to this so I don't have to plough through this whole tread. Also, I do try the search on RMW but it rarely works for me for some reason.

Is there a comparison for the Bachman version of the Mogul and the Dapol new one? If not does anyone have any comments about 'faults' on the Baccy version 43XX version please? Thanks ever so much.

Phil

 

[adb968008]

Agree it sounds like its over compensated on the springs, trimming the spring may work too.

Hornbys last 14xx 1450 had opposite issues..they needed springs but didnt have them and resulted in similar issues.

Edited December 6, 2021 by adb968008

[adb968008]

8 minutes ago, Mallard60022 said:

Apologies. Someone that might know and link me to this so I don't have to plough through this whole tread. Also, I do try the search on RMW but it rarely works for me for some reason.

Is there a comparison for the Bachman version of the Mogul and the Dapol new one? If not does anyone have any comments about 'faults' on the Baccy version 43XX version please? Thanks ever so much.

Phil

 

I have both, tbh Dapols wins hands down.

 

The Bachmann ones are 30+ years old, the moulding quality just not the same standard as today. It also used the split chassis, which some love, some hate and has no DCC.

 

A few grumble (but they always do), but overall I really like it and prices are quite reasonable. I’m sure others with sharpened knives will talk about the wheel size (1mm small, equates to 1.5” of tyre thickness), tender coupling (those of poor dexterity might need a few attempts) , but I find both very acceptable and definitely an improvement on your alternatives.

 

The 5101 is getting a hardtime as theres an immediate comparator. But tbh I still prefer the looks of Dapols from what I am seeing, it just maybe a spring needs adjustment, which is a shame but looks solvable, but its a complaint that should be upheld from what ive seen so far.

 

 

 

Edited December 6, 2021 by adb968008

[melmerby]

7 minutes ago, Mallard60022 said:

 

Is there a comparison for the Bachman version of the Mogul and the Dapol new one? If not does anyone have any comments about 'faults' on the Baccy version 43XX version please? Thanks ever so much.

Phil

 

The 43XX was inherited from Mainline by Bachmann and although they reworked the chassis to to take a standard in line motor it is still a split chassis.

They left the body and tender alone, so are to '70s standard.

AFAIK It was pencilled in to be re-tooled like all the remaining split chassis models but hasn't been and probably won't happen.

I have a Mainline one with a Comet Chassis and a slightly later Bachmann tender.

 

The Dapol one, with all it's faults is way better.

[Mallard60022]

7 minutes ago, adb968008 said:

I have both, tbh Dapols wins hands down.

 

The Bachmann ones are 30+ years old, the moulding quality just not the same standard as today. It also used the split chassis, which some love, some hate and has no DCC.

 

A few grumble (but they always do), but overall I really like it and prices are quite reasonable. I’m sure others with sharpened knives will talk about the wheel size (1mm small, equates to 1.5” of tyre thickness), tender coupling (those of poor dexterity might need a few attempts) , but I find both very acceptable and definitely an improvement on your alternatives.

 

The 5101 is getting a hardtime as theres an immediate comparator. But tbh I still prefer the looks of Dapols from what I am seeing, it just maybe a spring needs adjustment, which is a shame but looks solvable, but its a complaint that should be upheld from what ive seen so far.

Thanks for that. Split Chassis will be a PITA but hey, I can sort that. Also DCC is easily fitted to one of these. The one I have acquired (ex shop) will be covered in filth anyway. I can put up with it not being as good as my excellent Dapol item that pulls 9 Mk1 coaches and looks OK apart from a slightly weird Chimney.

P

[Guest]

On 06/12/2021 at 11:50, melmerby said:

It should run as an 0-6-0 with the trucks having no effect on the weight distribution, a driving wheel shouldn't drop into those gaps.

That's what I thought, I wonder if they run OK over live frogs?

 

On 06/12/2021 at 11:37, melmerby said:

I'm surprised that at the speed it was going the flywheel didn't carry the loco over the problem point. It suggests the flywheel isn't very effective.

I also noticed it now drops as it goes over the frogs etc. after the fix. Not good

My only flywheel loco is a class 08 shunter, and just testing on an isolated section (I'm DC only) at slow speed it carrys on till the bottom dead centre of last wheel is 8mm over the IRJ, my Baccy 8750, N class stop the second they go over IRJ, 94XX about 2mm over IRJ, but then it is heavy.  So as melmerby said is the flywheel up to it? To many unknowns.

 

EDIT: re-run test, 94xx is 2grams lighter than N class (loco only) so maybe coreless motor carries the 2mm further. Just a thought.

Edited December 16, 2021 by Guest
Additional info. spelling

[melmerby]

1 hour ago, Mallard60022 said:

my excellent Dapol item that pulls 9 Mk1 coaches and looks OK apart from a slightly weird Chimney.

 

Once again we get the variations. Mine won't pull anything like that, it's just too weak.

[melmerby]

51 minutes ago, confused said:

 

 

EDIT: re-run test, 94xx is 2grams lighter than N class (loco only) so maybe coreless motor carries the 2mm further. Just a thought.

Coreless motors have much less inertia than an iron cored motor, a distinct disadvantage for model locos.

Edited December 6, 2021 by melmerby