Dapol Class 121 and 122 in OO gauge

[Penrhos1920]

Has anyone been brave enough to take a knife to their Arriva 121 and correct the missing windows yet?

[adb968008]

Just took apart one of my 121/122’s in search of said grease, but there isn’t any to remove.

 

I’m very impressed with the gear chain, the shaft drives both bogies.

With a start up draw of 0.4amps @12v = .48w it’s actually quite power hungry, after a few minutes it drops to about 0.3amps but it’s still rumbling along.

 

I have 3 of these all performing pretty much equally.

 

It’s easy to see its free running, but thick grease on the gears isn’t the issue.

I’ve just experimented dropping out one of the gear shafts, and trying again, the difference is massively significant...

I’m down to 0.2a draw, and over time it’s accelerating and further decreasing in power, below 0.2 at some point.

 

 

Anyone any thoughts on this ?, i’m thinking this is only a 1 car DMU and i’d rather it move at a realistic speed on my layout on 1 powered bogie, than at a crawl on two ?

 

Hers it reassembled, you can see the shaft removed at the front of the picture, and it’s rattling along nicely.

 

 

Anyone any thoughts on this, I’ve left the gears in the bogie, they don’t lock up and are quite free running.

Edited January 3, 2018 by adb968008

[adb968008]

To follow up on yesterday’s posts, today I’ve done some performance testing.
For this I have used my silly gradient... as this seeks to show not just speed, but acceleration performance too.

To start with, here is a video of the chassis I modified above, and a GW 121 behind which is unmodified, This is a standing start on a gradient. The unmodified unit is drawing 0.4amp, the modified draws 0.2amp =0.6amp approx which on a 1amp Controller, with line losses is close to but not at its max. (Two unmodified units drawing 0.8amp are both negatively impacted in speed even more so and wouldn’t climb this hill as it was beyond the power available from the controller).

The next video shows both 121’s modified, you can see that they are now both very closely aligned, the GW unit ever so slightly out performs the blue grey unit, although they look it, they are not coupled together in this video.

They are both drawing approx 0.2amps, with a single gear shaft (0.4amp approx total) and are in line with (but still at the higher end) of UK industry norms for consumption, but allow speed and performance of the motors to reach there max, which is a much more realistic top speed.
Here is a standing start video, showing realistic control is still possible (this unit is maxing at 70% on the controller, not full speed) so probably 0.15amps. And could go faster, but is more than double it’s original speed before the shaft was removed.

Whilst increased speed isn’t to everyone’s taste and some are probably ok with performance being less than other locos on their layout, it is worth considering that the 2 shafts, and their torque is using considerably more power, than 1, whilst the unit is going slower, to achieve a higher speed the motor is working much harder, which could impact the life of the motor.


Here’s a few pictures how to modify the unit (bear in mind it’s your own choice todo so, and is probably outside warranty, even if, in my opinion it’s a better result).

1. Body removal is straight forwards, it just up clips, either side at either end, i’d Start with the open end, as the guards van end has exhaust pipes that sit just under the chassis your removing, and this way you can slide it slightly away from the cab.



Fortunately the screws you need to remove are all different sizes throughout this exercise, so just keep the count correct..1 bogie retainer, 1 pcb retainer, 2 gearbox retainers, 4 seat retainers.

2. 4 screws hold the seats on, these are straight forwards to remove and the seats lift straight off.

3. Remove the bogie retaining screw, and the pcb retainer

4. Slide the bogie side to side (don’t lower it out at is stage) and undo the two gearbox retaining screws..

5. The bogie now has movement in all directions, hold it with the frame and flip it sideways, I used the smallest screw in My jewellers screwdriver set to unclipped the gearbox cover and flip it upwards towards the chassis. (Flip the whole chassi/bogie over and repeat for the other side, again don’t let the bogie drop out, it’s still connected by the pickups).

Worm exposed

6. Using a small screwdriver, slide up the plastic cover that protects the pickups.

7. Finally, lift the pcb cover, approx 4mm above the chassis, and now for the greasy bit, using your fingers, or tweezers to pull out the worm/shaft, if it doesn’t immediately move, turn the worm or lift the pcb a little higher, it’s loose fit.


8. Reassemble again, in reverse order, slide the plastic cover back over the gearbox (it sits inside the pickups, so sometime you need to tweak the pickup ends out a little, then snap fit the gearbox lid, turn it right way up, add the pcb screw (the smallest screw you have),then the two gear box retainers, then the fat stubby screw to hold the bogie, add the seats and their 4 screws, finally add the body, starting with the guards van end, and sliding the exhausts under the frame, beware of the tail lamp irons, and finally snap it back together. Edited January 4, 2018 by adb968008

[brushman47544]

As seen in some of the photos... "Front lihgting" !!! How did that get through QC :-)

[ruggedpeak]

Adb

 

How do the units sound when a shaft is removed? Do they sound less strained. It seems like a good mod given all wheel drive and maximum traction is not required as you say.

 

As a non-engineer I'm wondering where in the drive train the excess strain is coming from and whether it can be alleviated to keep both shafts?

[adb968008]

Adb

 

How do the units sound when a shaft is removed? Do they sound less strained. It seems like a good mod given all wheel drive and maximum traction is not required as you say.

 

As a non-engineer I'm wondering where in the drive train the excess strain is coming from and whether it can be alleviated to keep both shafts?

 

 

When I placed it on rollers it sounded like a DMU actually, I was thinking I don't need a sound unit, though on the track it's quiet, I didn't notice any difference in sound, but it does seem less strained overall.

 

(On my gradient in the video the track is roughed with a file to improve adhesion, for the benefit of my steam fleet, it adds 1 carriage to a train length capacity, which is why it sounds like it's on a bridge).

 

When turning the fly wheels on the motor, I don't feel any tension, they turn quite freely. Indeed the gear chain in the bogie is also very free wheeling (I left the gear chain in my bogies although i'm sure theres some drag the amount of performance increase I get from just removing the shaft means I didn't need to go further).

 

I'm not sure why the two shafts impacts so badly, but the ammeter alone shows a 100% performance improvement, I didn't expect it to go from peaks of 0.4 down to a peak 0.2, maybe theres some conflict as one shaft is going forwards the other is technically reverse as its a mirror opposite.. I don't know, maybe its the gear ratio thats slowing it down and the impact of doubling it slows it drastically, but for sure the motors got more than enough beans and the capacity for the job.

it means I can now stick it with a 2 car DMU to make a 3 car and see it work.. which is how I saw most of these units, indeed although I saw most of them in service, I think i only ever saw the GW150 unit on it's own, the rest were always running with another unit, bit like 153s today !

 

i might put Heljans DPU on tomorrow and see how it's different... for sure that will pull the track up behind it and at full speed if I let it.

Edited January 4, 2018 by adb968008

[Pteremy]

Thanks for a really interesting post!

[BR Blue]

Yes. Very interesting. Many thanks.

[ELTEL]

Hi All

 

Just fitted a sound chip to my 121 very straightforward after obtaining the correct speaker as advised by Dapol

 

Thought I fit a driver into one of the cabs.

 

I am a bit unsure in how to access and remove one of the cabs for fitting of a driver, I thought wrongly by removing the two screws that hold the lighting strip I would be able to remove a cab.

 

Any ideas

 

Eltel

[ELTEL]

Sorted

[ruggedpeak]

When turning the fly wheels on the motor, I don't feel any tension, they turn quite freely. Indeed the gear chain in the bogie is also very free wheeling (I left the gear chain in my bogies although i'm sure theres some drag the amount of performance increase I get from just removing the shaft means I didn't need to go further).

 

I'm not sure why the two shafts impacts so badly, but the ammeter alone shows a 100% performance improvement,

I will do this mod when i have a moment, on my micro layout the strained performance of two driven bogies is not required. Will see if this affects it's issues going through Hornby points. Thanks for putting the info.

[dibber25]

Sorted

 

I succeeded in getting into the cab areas on two 122s but I'm having huge difficulty doing the same thing on a 121. I can unclip the cab interiors but I can't extract the lighting PCB from its locations in the headcode boxes. I would very much like to fit the headcodes and destinations INSIDE the glazing as it will look so much better. I've got an original green with whiskers 121 for which the supplied destinations are not appropriate - they even include Scottish destinations but none for the WR London area and branches which are the only ones suitable for an original livery 121. The West Midlands and Scottish ones were much later, if at all. I've made some suitable ones and printed them but I can't actually get them into the model where they need to be. I'd be interested to hear of a successful method to get to the head code box as I'm in danger of ruining a lovely model. (CJL)

[dibber25]

I succeeded in getting into the cab areas on two 122s but I'm having huge difficulty doing the same thing on a 121. I can unclip the cab interiors but I can't extract the lighting PCB from its locations in the headcode boxes. I would very much like to fit the headcodes and destinations INSIDE the glazing as it will look so much better. I've got an original green with whiskers 121 for which the supplied destinations are not appropriate - they even include Scottish destinations but none for the WR London area and branches which are the only ones suitable for an original livery 121. The West Midlands and Scottish ones were much later, if at all. I've made some suitable ones and printed them but I can't actually get them into the model where they need to be. I'd be interested to hear of a successful method to get to the head code box as I'm in danger of ruining a lovely model. (CJL)

 

Success! But it meant undoing SIX of the tiniest screws I have ever seen. I have no idea how I'm going to re-fit them. Also, the lighting duct moulded into the glazing of the head code box may mean that the decal actually has to go on the outside. In which case one of the reasons for opening up the model in this way, has gone. (CJL)

[centraltrains]

You know I just got 2 of the Dapol Imperium Decoders, and they run MUCH better with those compered to when on sapphires... Like a totally different model...

[adb968008]

Success! But it meant undoing SIX of the tiniest screws I have ever seen. I have no idea how I'm going to re-fit them. Also, the lighting duct moulded into the glazing of the head code box may mean that the decal actually has to go on the outside. In which case one of the reasons for opening up the model in this way, has gone. (CJL)

With tiny screws, that are no good for tweezers, I usually put a dab of paper glue (pritt stick) or blu tac on the screwdriver head so the screw sticks to it momentarily whilst I get it in the hole and tightened.

Edited January 17, 2018 by adb968008

[dibber25]

With tiny screws, that are no good for tweezers, I usually put a dab of paper glue (pritt stick) or blu tac on the screwdriver head so the screw sticks to it momentarily whilst I get it in the hole and tightened.

 

My crosshead driver with the sharpest point has a magnetised tip which proved very useful today as I put the cabs back in place. You can't fit the head codes inside the glazing because there's a light duct arrangement built in to the back of the glazing. So all I was able to do was to fit drivers - they are essential, however, as DMUs look daft running as 'ghost trains'. (CJL)

[Matabiau]

Success! But it meant undoing SIX of the tiniest screws I have ever seen. I have no idea how I'm going to re-fit them. Also, the lighting duct moulded into the glazing of the head code box may mean that the decal actually has to go on the outside. In which case one of the reasons for opening up the model in this way, has gone. (CJL)

 

Where do these screws come from? I believe I have found one rattling around inside the 121 but couldn't see the whole it came out of. Thanks.

[BR(S)]

Where do these screws come from? I believe I have found one rattling around inside the 121 but couldn't see the whole it came out of. Thanks.

 

They secure the contact strips between the lighting strip and the cab area, three each end.

 

The tiny screws make it easier to add drivers in the 121 as just the cabs can be removed.  In the 122, the contacts are soldered in place, necessitating removal of the lighting strip and cabs as one piece. 

Edited January 18, 2018 by BR(S)

[ELTEL]

My crosshead driver with the sharpest point has a magnetised tip which proved very useful today as I put the cabs back in place. You can't fit the head codes inside the glazing because there's a light duct arrangement built in to the back of the glazing. So all I was able to do was to fit drivers - they are essential, however, as DMUs look daft running as 'ghost trains'. (CJL)

Hi Chris

 

As my class 121 is destined to run in the West Country, none of the destination panels are appropriate, just as well because you can’t fit from the inside.

 

Have you fitted yours on the outside?

 

Eltel

[dibber25]

Hi Chris

 

As my class 121 is destined to run in the West Country, none of the destination panels are appropriate, just as well because you can’t fit from the inside.

 

Have you fitted yours on the outside?

 

Eltel

 

Yes. Like you, I found none that were suitable on the extensive sheet supplied. Quite why so many non-121 destinations have been included and so many genuine ones left off, I've no idea. It almost seems like the sheet was designed for a different model. At first I used a decal I made by copying the head code and destination from a near head-on picture on the internet. The main reason was that 'STAINES WEST' has to be in tiny type to fit, whereas on the BR blinds a very condensed font was used. The picture also had a 2A50 head code which was wrong for the branch (2A82) but the head code was seldom correctly displayed so I quite liked the idea of 2A50. Sadly the photographic destination didn't look that great, (see pic) so I printed my own (in very small type). The destination is INSIDE the windscreen but there's no way to fit the head code inside because there's a big light conductor in the way, so that is fitted on the outside. (CJL)

Edited January 24, 2018 by dibber25

[exmoordave]

I just wondered if anyone else has had the same experience as I have had with their 121? 

When I received my long awaited unit I decided to test it straightaway, and placed it on my end-to-end Southern region layout, "Newton St. Petrock". I ran it gently up and down a couple of times (say 12' in each direction), and although slow it appeared to be OK. However after driving it again, the red overload light began to flicker and gradually became brighter, until the unit stopped completely. After waiting for a few moments, I tried again and the overload light did exactly the same and again the unit stopped completely. I decided to leave it for a day or so, and upon trying yet again, the same thing happened.

I contacted the retailer to inform them and they said to return it which I did, and they sent a replacement - which did exactly the same! I then decided to try it on a rolling road, which showed that it ran perfectly. Now the only difference here are the control units used. The unit I use for my layout is a Kent Panel Control, and I use an old Hammant & Morgan for the rolling road. Both transformers have an identical output of 1 Amp, so no difference there. I have emailed Dapol to see if they have any thoughts, but I thought I would air the problem here to see if anyone can kindly offer any thoughts please? I would just say the 121 is a DC unit & not DCC. So if anyone can make any suggestions I would be very pleased to hear. Many thanks in advance.

[letterspider]

When I placed it on rollers it sounded like a DMU actually, I was thinking I don't need a sound unit, though on the track it's quiet, I didn't notice any difference in sound, but it does seem less strained overall.

 

(On my gradient in the video the track is roughed with a file to improve adhesion, for the benefit of my steam fleet, it adds 1 carriage to a train length capacity, which is why it sounds like it's on a bridge).

 

When turning the fly wheels on the motor, I don't feel any tension, they turn quite freely. Indeed the gear chain in the bogie is also very free wheeling (I left the gear chain in my bogies although i'm sure theres some drag the amount of performance increase I get from just removing the shaft means I didn't need to go further).

 

I'm not sure why the two shafts impacts so badly, but the ammeter alone shows a 100% performance improvement, I didn't expect it to go from peaks of 0.4 down to a peak 0.2, maybe theres some conflict as one shaft is going forwards the other is technically reverse as its a mirror opposite.. I don't know, maybe its the gear ratio thats slowing it down and the impact of doubling it slows it drastically, but for sure the motors got more than enough beans and the capacity for the job.

it means I can now stick it with a 2 car DMU to make a 3 car and see it work.. which is how I saw most of these units, indeed although I saw most of them in service, I think i only ever saw the GW150 unit on it's own, the rest were always running with another unit, bit like 153s today !

 

i might put Heljans DPU on tomorrow and see how it's different... for sure that will pull the track up behind it and at full speed if I let it.

 

Thanks for your post, after reading it I decided to test my Bubblecar - I hadn't a chance since Christmas to get it out of the box.

 

I had the same problem with slow running but found another potential solution if any one else has the same problem.

 

On the rolling road I only had one bogie running and the other off the runners. A bogie on its own worked faster. Then  I swopped it around after some running in and did the same with the other bogie. If you give each separate bogie a reasonable period of running in (I only did 10 minutes), then when the DMU is put on the tracks it runs as fast as you would expect.

 

Hope this is of help for those modellers who don't want to take the unit apart

Edited January 30, 2018 by letterspider

[Mooresby]

Apologies if its been mentioned earlier in the thread but has anyone had issues with directional lighting?  Works fine in one direction but nothing from either end when going in the other.  I've got an ESU Loksound 4 decoder on board.  Any help would be greatly appreciated

[Chuffed 1]

What an impressive thread!  A question for the historically knowledgeable out there. One of the locations on the layout I am building is Alvescot, on the Fairford branch. A lot earlier on this thread someone said they saw a 121 with Fairford on the blind.  In addition to this, in the Middleton Press Branch Line To Fairford there is a photo at Eynsham that purports to show an approaching Flying Banana. Leaving aside that it seems to show a departing unit, considering the disembarked passengers on the adjoining photo, as close an inspection as is possible with a printed picture seems to show a 121 or 122 (or even, perhaps, one of the Oxford-Bedford 108's?).

My question is, did Oxford have an allocation of single units during their first four years?

 

BTW, my own 122 runs like a dream and the green seems about right, unlike the 'whiskers' which are far too thick.  Or did BR paint 'speed moustaches' on their early units??

[chrisf]

Sorry to disappoint you, Chuffed 1.  When the Gloucester built cars [Class 122] were introduced, in 1958, they were divided between Southall, Reading and Tyseley.  When the Pressed Steel variety [Class 121] appeared in 1960 they too were divided between Southall and Reading except for three which went to Bristol.  The advent of the 121s displaced some 122s which mostly went to Laira with some to Tyseley.

 

As a consolation prize you may like to know that Oxford played host to ex-Great Western railcars at various times in the 1950s but according to the book at my elbow never more than two and none after 1957.

 

Chris 

 

Edit - I forgot to deal with the appearance of Fairford on dmu destination blinds.  It's true, not only of the single cars but also of the 117s.  I don''t know the book Branch Line to Fairford so can't help you there.  Conventional wisdom says that there was never a regular dmu working to Fairford but never say never!

Edited February 8, 2018 by chrisf