4-6-2 loco wheels jamming

[Throppers]

Hi

I have a Hornby Duchess Class 4-6-2 loco R2531 which runs fine in a forward direction but jams in reverse. I assumed a split gear however having removed / inspected all the gears, I can see nothing wrong with them. 

So I put the wheels back on with the idler gear removed so I can free spin the wheels and have noticed an issue with the front pair of wheels, which jam or pop out of the axle mounts when turned backwards. However when running forwards they are fine. 

The followong youtube video demonstrates. 

 

 

Any ideas? I’m thinking probably wheel quartering? 

Thanks

Throppers 

 

Edited July 14, 2019 by Throppers

[34theletterbetweenB&D]

Not quartering. That affects movement forward and reverse if the effect is that severe. I believe this will be a side rod snagging, on the far side as filmed so it cannot be seen!  Side rods snagging is very often directionally sensitive.

[RexAshton]

It could be the connecting rod catching the return crank or possibly the front crank pin catching the face of the crosshead. These can get bent if the loco hasn't been taken of the track carefully. As 3theletterbetweenb&d says though, it's difficult to be certain from the video.

[Theakerr]

Agree with snagging.  I have fixed definitely more than one for friends and it has pretty well been 100% Hornby.

[Throppers]

Hi all. 

Further video below to answer some points raised. 

 

 

Having checked all the rods and crank pins, everything is fine with no snagging or catching at all. 

 

Having pushed it along the track it runs along fine but this is a bit of a false test admin reality the drive comes from the centre axle and the front and rear axle are turned by the con-rods. 

[Grovenor]

Looks to be the front crank pins catching on the connecting rods, it can be seen in both videos. Tweak the connecting rods out a bit to give clearance. It would help to reduce the sideplay in the front axle by slotting fibre washers between the frame and the wheels.

Rgds

Edited July 14, 2019 by Grovenor

[cypherman]

Hi all,

I have noticed from the video that the wheel weights do not match. Both sides are out from the middle wheels. Might I suggest that at some point some one has taken the front wheels out and put them back in the wrong way round.

[Right Away]

7 hours ago, cypherman said:

Hi all,

I have noticed from the video that the wheel weights do not match. Both sides are out from the middle wheels. Might I suggest that at some point some one has taken the front wheels out and put them back in the wrong way round.

Weights on the front drivers on the prototype were offset in respect of the other axles to balance the motion and drive from the inside cylinders.

Edited July 15, 2019 by Right Away

[John Tomlinson]

I suspect there are two things going on here.

 

Your film shows the axle lifting and falling, which on the second film looks to be due to the normal action of the rods as you've removed the baseplate. However the first film shows a distinct jamming in one direction on what will be the offside when the chassis is the right way up. This looks like the action of the crankpin on the front driver against the connecting rod (as said above). This connecting rod appears concave to the chassis, it would have a better chance of not fouling if it was convex, by which I mean the connecting rod was pointing straight at the point of leaving the driver, and then curved in towards the cylinder.

 

This is a very common problem on Hornby Pacifics, both of my Duchesses and several WC/BB/MN's having the same problem. Excess sideplay is an issue on the leading driver, and can be cured by fashioning a couple of "U" shaped pieces of plasticard and glueing them to the chassis round the axlehole. Another issue is the size of washer between the coupling and connecting rods on the main driver. Some Hornby Pacifics have a very wide version, which helps to keep the connecting rod further out, others don't, it seems like random walk! Sometimes the likes of Peters Spares have packs of washers available as spares and I try to keep some in stock to cope with this eventuality.

 

John.

[Ceptic]

In the past, when I've had problems with Hornby Bulleid pacifics' wheels failing to rotate, it's always turned out to be caused by the final drive's gear wheel cracking / splitting from around the central / axle hole. 

IIRC, there's a RMweb thread on the subject, somewhere.

[RedgateModels]

48 minutes ago, Ceptic said:

In the past, when I've had problems with Hornby Bulleid pacifics' wheels failing to rotate, it's always turned out to be caused by the final drive's gear wheel cracking / splitting from around the central / axle hole. 

IIRC, there's a RMweb thread on the subject, somewhere.

 

I'm just fixing the very same issue for a fellow Webber. Rebuilt WC split axle gear. Wheelsets are freely available though