Airfix 4f, running nightmare!

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markS&D
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Airfix 4f, running nightmare!

Postby markS&D » Fri Feb 17, 2012 7:23 pm

I have reached the point of despair with this loco.

It is so unreliable, that I have now got to the point of wanting to chuck it in the bin!

The motor assembly runs fine, if I could get the damn loco chassis to pick up the current correctly from the track!

I have had the loco to pieces about 15 times now! Each time I take it to bits and reassemble it, it works for a couple of circuits then goes back to its old ways again!

I have tried adjusting the wiper pickups, I have cleaned the wheels to within an inch of their lives, I have cleaned the back of the loco wheels, I have cleaned the contact surfaces of the wiper pickups, I have checked the back to back measurement of the wheels. And yet the loco keeps stopping at random places on my layout, and has to be given a nudge to get it moving again.

No other loco has this problem. It is driving me mad!

Has anyone else experienced this problem, with the Airfix, or even the newer tender drive Hornby model?
My layout, only look if you are interested:

viewtopic.php?f=22&t=48422

Latest Video Link:

https://youtu.be/g5ytOK5FCZc

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Campaigner
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Re: Airfix 4f, running nightmare!

Postby Campaigner » Fri Feb 17, 2012 11:40 pm

Not personally had any problems when I had my Airfix 4F, however, have you stopped to consider how old this is? this could be something to it. :(

Bigmet
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Re: Airfix 4f, running nightmare!

Postby Bigmet » Fri Feb 17, 2012 11:43 pm

Are you absolutely sure the problem is in the pick up area? The way I would check this is to solder on a 12V bulb directly onto the wiper strips via short lengths of bare copper wire. You will see any momentary losses of pick up at a moderate controller setting by the light flickering far more readily than you will detect a change in the motor speed. But what you may see is the bulb staying on when the loco stops : that would mean it is not the pick up side at all, but a poor connection somewhere between pick ups and motor. The kind of intermittent fault you are describing is very easily the product of a dry soldered joint, or a wire with the conductor broken inside the insulation, or a worn brush with a slack spring.

All that said, there is no doubt in my mind that pick up on driven wheels is typically way more effective than from undriven. For a Midland type 0-6-0, the little Bach 3F is a jewel of a performer, and not expensive...

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flying scotsman123
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Re: Airfix 4f, running nightmare!

Postby flying scotsman123 » Sat Feb 18, 2012 10:50 am

i have problems with locos with motors in back too. i had a black LMS hornby loco and right from the start it was all jerky and horrible. i still maintain that any designer who puts the moter in the tender was drunk :mrgreen:
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Stone station in pre-grouping days, my layout. Workbench for other projects here.

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markS&D
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Re: Airfix 4f, running nightmare!

Postby markS&D » Sat Feb 18, 2012 8:01 pm

Bigmet wrote:Are you absolutely sure the problem is in the pick up area? The way I would check this is to solder on a 12V bulb directly onto the wiper strips via short lengths of bare copper wire. You will see any momentary losses of pick up at a moderate controller setting by the light flickering far more readily than you will detect a change in the motor speed. But what you may see is the bulb staying on when the loco stops : that would mean it is not the pick up side at all, but a poor connection somewhere between pick ups and motor. The kind of intermittent fault you are describing is very easily the product of a dry soldered joint, or a wire with the conductor broken inside the insulation, or a worn brush with a slack spring.

All that said, there is no doubt in my mind that pick up on driven wheels is typically way more effective than from undriven. For a Midland type 0-6-0, the little Bach 3F is a jewel of a performer, and not expensive...


This is a tender drive model. The 'dummy' loco has pickups on all 6 wheels, but the tender wheels are all plastic, with traction tyres.

I do wonder if the loco chassis is worn out, due to the fact that the metal axles are running in an all plastic chassis moulding, perhaps this is causing 1 or more of the wheels to be lifted off the track, right at a moment when all 6 wheels really need to be making contact. Plus something is not quite right, the loco has a slight wobble as it is pushed round by the tender.

Did Hornby upgrade anything on the chassis, when they started producing the 'tender drive' 4F, or is it basically the same model?
My layout, only look if you are interested:

viewtopic.php?f=22&t=48422

Latest Video Link:

https://youtu.be/g5ytOK5FCZc

Bigmet
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Re: Airfix 4f, running nightmare!

Postby Bigmet » Sat Feb 18, 2012 11:38 pm

It was basically the same model in Hornby production, with a tender drive. But the 2011 announcement included a revised loco drive 4F: same body mouldings, on a new chassis. Since the wheelbase is the same as that of the Q1, it rather is to be hoped that Hornby will re-use the basics of that successful chassis design: a version of their proven black can motor, with a good two stage reduction for smooth running. Over a year later still awaiting sight of this model...

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markS&D
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Re: Airfix 4f, running nightmare!

Postby markS&D » Sun Feb 19, 2012 1:45 am

The revised Hornby LMS '2p' has been released over the last few weeks, hopefully the 4F will follow soon. 'Tony Wright' reviewed the latest '2p' model and gave it the 'thumbs up', although The 5 pole loco drive models from Hornby in my opinion are usually really good runners anyway.

I dont dislike the Airfix 4F model, it looks good compared to other items that were available in the late 70's and 80's.

Perhaps I am expecting too much from such an old model, especially as I am using DCC control, Perhaps the momentary losses of current collection would not have shown up on normal DC control?

I have read somewhere that the traction tyres from tender drive locos cause the track to become more dirty in a short space of time. Is this true?

I have looked at Hornby advertising from the early 80's and they try and convince us that 'tender drive' is really good. In my opinion (rightly or wrongly) , this was nothing more than a cost cutting excersize by Hornby, so that they could use the same crappy 3 pole 'ringfield motor' in all Steam and Diesel/Electric models.

Srangely there were a couple of exceptions such as the SR light Pacific which had loco drive.

To sum things up, I cant financially afford to replace the 4F with the new 'loco drive' version, at £80+ it is too expensive. In these hard times, it is £80 that I would rather spend on the layout itself. If I can get the Airfix model to run, that will do me for now.

I like the idea that you proposed about soldering a bulb across the wiper pickups, that would indeed show up a current collection problem especially on DCC as the bulb would stay lit even when the loco is stationery.
My layout, only look if you are interested:

viewtopic.php?f=22&t=48422

Latest Video Link:

https://youtu.be/g5ytOK5FCZc

Bigmet
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Re: Airfix 4f, running nightmare!

Postby Bigmet » Sun Feb 19, 2012 9:27 am

You need to use 12V bulbs in series for DCC, because the typical track voltage peak well exceeds 12V. What I was trying to encourage you to think about is possibilities for the location of the problem. You have obviously given a lot of attention to pick up, now you need to know if that is working well , and a light can show you that. Because if that proves the pick up is OK, then the problem must be 'somewhere else' on the loco. These kinds of intermittent troubles can be the very devil to track down, because you have to wait for when it happens and then try and detect the source.

Traction tyres can be a source of track dirt. There are some more sophisticated types out there, Rivarossi had a good example which didn't lead to a significant increase in track dirt for example, but what has been used on OO is pretty basic.

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stuartp
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Re: Airfix 4f, running nightmare!

Postby stuartp » Sun Feb 19, 2012 1:28 pm

Bit of a left field suggestion, but the generic Hornby 0-6-0 chassis of the same period might fit with a bit of sawing. Used under the Jinty, Thomas, 08, Ivatt 2MT and no doubt a lot more, available from Ebay in various formats from bomb-proof Tri-ang version with an XO4 motor which would run your washing machine to DCC ready or even fitted versions.
Portwilliam - Southwest Scotland in the 1960s, in OO - http://stuart1968.wordpress.com/

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markS&D
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Re: Airfix 4f, running nightmare!

Postby markS&D » Sun Feb 19, 2012 6:55 pm

I tried connecting a 15 volt grain of wheat bulb across the pickups as you suggested, and I did notice that when the loco wheels are in a certain position, the bulb goes out.

When I removed the wheels from the chassis, I noticed that none of them are running true on their axles, which may be making the wheels lose contact with the wiper pickups and/or the track.

Would a new wheelset from this website fit the old airfix chassis?

http://www.modeltrains4u.co.uk/Spares-b ... /page3.htm
My layout, only look if you are interested:

viewtopic.php?f=22&t=48422

Latest Video Link:

https://youtu.be/g5ytOK5FCZc

Bigmet
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Re: Airfix 4f, running nightmare!

Postby Bigmet » Sun Feb 19, 2012 7:21 pm

Ah, that's progress: you are now sure there's a pick up problem. Can you see the pick up wipers losing contact with the wheelbacks when you look from the underside (or some other convenient angle) and rotate the wheels to what you have now identified as the 'no pick up' position? What you want to know before buying any spares is exactly where the problem lies. If the wheel wobble is what takes the wheelbacks out of contact, then if this cannot be fixed by bending the wipers out a little more, or trueing up the wheels , then buying a new set might be a solution.

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markS&D
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Re: Airfix 4f, running nightmare!

Postby markS&D » Sun Feb 19, 2012 7:51 pm

Further investigation, seems to show that the wheel wobble is actually causing the rear wheel on the left side, to lift off the track slightly. This seems to be causing the loco to lose electrical contact on points, and slightly uneven sections of track.

The problem with the wheels on this loco is that the axles are plain, with no splines on them, so if I start trying to square the wheels up, I will probably end up upsetting the quartering of the wheels even more than it already is due to the out of true wheels.

Plus the newer Hornby wheels look better than the Airfix ones, with smaller flanges. They are not a bad price from that online store.

The annoying thing is that I got the loco for £25, which I thought was a bargain, by the time I have finished messing about, I might aswell have bought the newer tender drive Hornby version :roll:
My layout, only look if you are interested:

viewtopic.php?f=22&t=48422

Latest Video Link:

https://youtu.be/g5ytOK5FCZc

Bigmet
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Re: Airfix 4f, running nightmare!

Postby Bigmet » Mon Feb 20, 2012 9:37 am

Or even the loco drive 4F which Hornby have coming. Or the Bachmann 3F which is available and is a super model available at around £60.

Even if you can get it running reliably by spending on replacement parts, it will always be a traction tyre dependent tender drive unit. Is that what you want longer term? If not then flog it for what you can get, and put the money toward new recently designed product. It is very easy to spend the money that would have bought a better design new model, in several 'little dribbles' buying spares to keep an old and inherently inferior model going.

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markS&D
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Re: Airfix 4f, running nightmare!

Postby markS&D » Mon Feb 20, 2012 6:29 pm

Probably true. To be honest I would prefer to spend my time concentrating on the layout, than fiddling about trying to get older models to run properly.
My layout, only look if you are interested:

viewtopic.php?f=22&t=48422

Latest Video Link:

https://youtu.be/g5ytOK5FCZc

whynot
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Re: Airfix 4f, running nightmare!

Postby whynot » Mon Feb 20, 2012 7:46 pm

"Perhaps I am expecting too much from such an old model" seems to be the truth of the matter! It's OLD and presumably worth next to nowt (and was hardly an expensive luxury item when new). Stuff wears out!
dave j
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