Tender drive A4 problems

Discuss Hornby Model Railway products and related topics here. This includes (Lima, Rivarossi, Jouef, Electrotren).
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Ken Shabby
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Joined: Thu Jan 15, 2009 12:20 pm

Tender drive A4 problems

Postby Ken Shabby » Tue Mar 27, 2018 1:58 am

A few weeks back I bought a cheap tender drive Mallard in B.R livery. This was the loco I really wanted back in 1980 , and now I finally have one.
At first the loco ran poorly with the loco wheels locking up and being pushed along by the ringfield in the tender, but this was easily put right by lubricating the locos axles. For a couple of days all was well , then last Friday the loco became jerky but then settled down again after about 30 minutes running.
Today it was even worse, so I tested the tender with old Hornby Schools class , It looked odd but ran fine and so It's not a fault with the tender drive .
I then ran the A4 with the Schools tender to be sure, and again it ran very poorly.
This has got me thinking there is a problem with the draw bar between the loco and tender. Although it looks to be undamaged and clean I can't think of any other reason for the poor running.
The loco chassis is now very free running and I only used a tiny amount oil bought from Hattons ( I don't recall the exact make) , so i don't think I've distrurbed anything in the loco chassis.
I may borrow the pony truck off my sons old Flying Scotsman tomorrow for further tests. In the meantime does anyone have any idea what could be causing this ?
Thanks, Ken

GWR_fan
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Re: Tender drive A4 problems

Postby GWR_fan » Tue Mar 27, 2018 4:49 am

I have found with older Hornby free rolling chassis with single power pickup that crud in the axle cutouts can affect power pickup. Lubricating will make the problem worse. The same applies to the A3, A4 and King class chassis. I would thoroughly clean the rolling chassis and then sparingly lube. There may be a wire problem at the drawbar which needs to be looked at. Also close up the brass power strips on the drawbar that clamp on the tender drawbar pin to ensure positive power transfer.

Bigmet
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Joined: Tue Aug 14, 2007 2:19 pm

Re: Tender drive A4 problems

Postby Bigmet » Tue Mar 27, 2018 8:35 am

Ken Shabby wrote:A few weeks back I bought a cheap tender drive Mallard in B.R livery. This was the loco I really wanted back in 1980 , and now I finally have one.
At first the loco ran poorly with the loco wheels locking up and being pushed along by the ringfield in the tender, but this was easily put right by lubricating the locos axles. For a couple of days all was well , then last Friday the loco became jerky but then settled down again after about 30 minutes running.
Today it was even worse, so I tested the tender with old Hornby Schools class , It looked odd but ran fine and so It's not a fault with the tender drive .
I then ran the A4 with the Schools tender to be sure, and again it ran very poorly.
This has got me thinking there is a problem with the draw bar between the loco and tender...


Good fault finding process, but not the highlighted conclusion: what you now know is that the problem is on the A4 loco 'somewhere' but not any specific component. In fact you can rule out the draw bar, because following initial lubrication of the A4 the unit ran well, so the power was being conducted properly to the tender drive then! What you describe is very characteristic of what 'GWR fan' has identified:

GWR_fan wrote:I have found with older Hornby free rolling chassis with single power pickup that crud in the axle cutouts can affect power pickup. Lubricating will make the problem worse...


Absolutely. What happens is that the new lubricant starts to dissolve all the old crud that previous lubricants left behind when they evaporated. As the old crud redissolves it starts to impede pick up through the axles and the chassis block. A thorough cleaning of the axles and their locations, followed by a light relubrication should make the improvement you are looking for.

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Ken Shabby
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Joined: Thu Jan 15, 2009 12:20 pm

Re: Tender drive A4 problems

Postby Ken Shabby » Tue Mar 27, 2018 12:58 pm

Gentlemen, thank you.
It was indeed being caused by too much lubricant and gunge in the axle cut outs. It was a 5 minute job to remove the plastic plate off the bottom of the loco chassis and clean them out with a cotton bud and some lighter fluid.
She's now running very smoothly indeed.
This was the loco that first got me interested in model railways back in 1980, when a mate brought the Hornby catalogue into school.
It was on my 9th birthday list , but I ended up with a Airfix 4F instead.
Thanks, Ken


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