Hornby A4's, and their fixed pony trucks

[Dan_Kunja]

As a modeller who's on a budget (aren't we all) I haven't had the chance to get my hands on the newer premium Hornby A4's. However, from what I've seen online and from an old (10 years old) model I own, they seem to have fixed pony trucks on their A4's while their other models (Duchess and West Country Classes) have swinging/pivoting pony trucks.

Any insight as to why this is, or just to check if they are fixed on the newer models at all?

[Atlantic 3279]

With a bit more searching the answer to this would be found easily, but to summarise: no LNER Pacific, Prairie or Mikado ever had a rear "pony truck". The rear carrying wheels were in Cartazzi axleboxes, providing limited freedom for the wheels to move aside between the fixed rear frames of the loco which were just 6 feet apart. When Hornby decided to make a model that looks right, instead of carrying on with the old toy-train fudge of portraying the rear frames as an incorrect waggling pony truck with a visible gap above, that inevitably generated the problem of greatly limiting the movement of those rear wheels resulting in a loco that would not go round toy-town curves. Hence the locos come from the factory with flangeless rear wheels. You can hack the rear end of the loco about internally to allow it to cope with reasonable curves if proper flanged wheels are installed.

[Hatfield Shed]

... from what I've seen online and from an old (10 years old) model I own, they seem to have fixed pony trucks on their A4's while their other models (Duchess and West Country Classes) have swinging/pivoting pony trucks.

Any insight as to why this is, or just to check if they are fixed on the newer models at all?

Hornby initiated the move to a fixed rear flangeless wheelset on the A4 (and A3 which shares the same mechanism in all essentials) but have since introduced this to every other large loco with an outside framed rear carrying wheelset in their range. LMS, SR and BR pacifics genuinely had (slightly)pivoting rear trucks, but Hornby have decided to fix these too.

I believe this is largely about containing costs, while offering superior appearance of the axlebox and frame parts, and hoping that the flangeless wheelset doesn't offend. For those whom it does offend, there's several possibilities that enable a flanged wheelset to be installed.

For comparison, Bachmann go about it another way. The exterior relief of the axleboxes is less than scale depth, and width over the frame faces overscale; by this means they win enough space to put a flanged rear truck wheelset in a traversing slide, and this is capable of negotiating set track curves.

[65447]

Hornby initiated the move to a fixed rear flangeless wheelset on the A4 (and A3 which shares the same mechanism in all essentials) but have since introduced this to every other large loco with an outside framed rear carrying wheelset in their range. LMS, SR and BR pacifics genuinely had (slightly)pivoting rear trucks, but Hornby have decided to fix these too.

I believe this is largely about containing costs, while offering superior appearance of the axlebox and frame parts, and hoping that the flangeless wheelset doesn't offend. For those whom it does offend, there's several possibilities that enable a flanged wheelset to be installed.

The current Hornby 'Britannia' includes in the box a flanged wheelset on an axle to replace the flangeless set as supplied in the rear 'pony truck' - however there is no mention of this in the enclosed instructions...

[mick b]

... from what I've seen online and from an old (10 years old) model I own, they seem to have fixed pony trucks on their A4's while their other models (Duchess and West Country Classes) have swinging/pivoting pony trucks.

Any insight as to why this is, or just to check if they are fixed on the newer models at all?

Hornby initiated the move to a fixed rear flangeless wheelset on the A4 (and A3 which shares the same mechanism in all essentials) but have since introduced this to every other large loco with an outside framed rear carrying wheelset in their range. LMS, SR and BR pacifics genuinely had (slightly)pivoting rear trucks, but Hornby have decided to fix these too.

I believe this is largely about containing costs, while offering superior appearance of the axlebox and frame parts, and hoping that the flangeless wheelset doesn't offend. For those whom it does offend, there's several possibilities that enable a flanged wheelset to be installed.

For comparison, Bachmann go about it another way. The exterior relief of the axleboxes is less than scale depth, and width over the frame faces overscale; by this means they win enough space to put a flanged rear truck wheelset in a traversing slide, and this is capable of negotiating set track curves.

Bachmann A1 and A2 suffer as result of using the slide idea and is much less than scale depth mentioned above and is very noticeable, I have found they are a pain to line up on the track and can derail with little provocation.
I have no problem with the flangeless version used by Hornby.You have to look very hard to notice the missing flange on the wheel set. They supply flanged wheel set with the Locos , for anyone who wants to fit one and it will still go round very generous curves.

[ColHut]

Yes, my son's new Silver Link comes with a flanged trailing wheel set in addition to the flangeless one fitted, although it is not mentioned in the instructions. I actually wondered why they had included a spare to start with!

[Hatfield Shed]

Some of us view at or near rail level and are offended by the obvious visual blot of an absent flange maybe?

Hornby's supply of the flanged wheelset is very welcome, but not only are there no instructions, it simply doesn't work correctly on either of the mechanisms that are common to A3/A4 and Britannia/Clan. The axle is too high on the A3/A4 so the wheelset isn't on the rails, and once this is sorted the minimum radius installed is about 4 feet. On the Britannia/Clan it simply will not fit, as the flanges do not clear inside the rear truck casting until some metal has been ground out; then it is good for a minimum radius of 3 feet. It is easy enough on both to knock things about until a 30" minimum radius is possible with no loss to external appearance, that is as small as I need for routes traversable by pacifics.

No idea of how it does in the P2, Bulleid and Stanier pacifics.

The Bachmann sprung slide, often has too little vertical travel to allow the wheelset to be positively sprung onto the rail head over gradient transitions and the like. I have had to fiddle with all the A1s (early purchases circa 2001-3) to get the springing optimised for travel and force. Completely reliable on my 3' minimum radius point / 30" plain track curve set up. (The later A2 and V2 were much better out of the box, fit to run without adjustment.)

[cctransuk]

I have just 'unfixed' the rear trailing truck of a Hornby 71000 'Duke of Gloucester'.

I drilled through the cast dummy pivot point at 1.4mm., for later tapping 10BA.

I then cut longitudinally through the chassis casting with a piercing saw, following the upper profile of the trailing truck.

Once the truck was detached, I removed some metal from the cut surfaces of the chassis block and trailing truck to tidy them up and provide clearance for running and swivelling.

The truck was counterdrilled 1.8mm for 10BA clearance, and the chassis was tapped 10BA.

A waft of Halfords Satin Black tidied things up, and flanged wheels were fitted in the truck slot with a 14mm. length of 1.5mm. brass rod above the axle to give the correct ride height.

Screwed to the chassis block with a 10BA cheeshead screw, and with a drop of oil on the pivot and the axle slot, the trailing truck now behaves as per the prototype.

What Hornby forget is that, whilst the correct fixed Cartazzi frames look fine on scale radii, they look ludicrous on the necessarily tighter radii that most of us are obliged to use, even if these are generous by model railway standards. Plus, the steamroller flangeless wheels short circuit between the running rail and open point blades.

Just another cost-cutting measure !!

Regards,
John Isherwood.

[Mersey508138]

I did the same thing with my hornby britannia loco as it looked ridiculous traversing 2nd and 3rd radius curves aswell as hornby R628 curves ( same radii as the hornby Y points ) with the rails visible under the cab area. I actually tried fitting the flanged wheels that came supplied with it before I made the modification 3 years ago and it was worse than with the non flanged wheels because with the rear pony fixed in place and the flanged wheels fitted it derailed everytime no matter which direction I ran it. After a few months of derailments I completely removed the rear wheels and ran it like a 4-6-0 until 2013 when I was looking through a model magazine ( I'm afraid I cannot remember which 1 or which year it was ) and saw a project which would allow the rear pony to swing as it should and in mid 2013 I bit the bullet and within 2 hours of starting the cut through the block which the rear wheels are fitted into the loco had a rear swinging pony truck and runs much better than she did with it fixed in place.

So successful was this modification that over the last few months in between my studies I have been looking at the feasibility of doing this modification on my 2 Railroad Gresley A1/3 Locos aswell as the super detail A3s 60103 & 60049 and A4 60029 because even though I had to file off the sidescof the block which keeps the rear wheels more or less centered I also had to deepen the axle slot on these locos as the slot on the rear of these locos as supplied actually lifts the rear of the loco up so the 6 driving wheels end up not all making proper contact with the rails thus limiting the locos haulage capacity.

However, if the slot on the block under the cab is made deeper then the supplied wheels sit correctly and also the driving will all be in full contact with the rails. Modifications are also required to couple the loco and tender once the block that holds the rear wheels is removed and for that I recommend tony wrights idea where a loop of brass wire ( I use 1.0 mm wire ) bent like a goal post and a hook made from the exact same wire attached to the tender chassis will cure this problem and once wires are connected to the tender pickups the loco will be ready for service.

This may disappoint some of you but I may even carryout this modification on a Hornby P2 if I ever manage to get 1 to enable it to go round depot curves aswell as over turnouts while going backwards towards the shed or to couple up to a rake of coaches or wagons.

Hope this helps.

[RayS]

This thread is extremely interesting, but I for one would welcome some clear illustrations of the suggested mods?

[nzpaul]

I'm not wanting to be argumentative or anything but...while I can see the point making a Britannia's trailing truck move with the reasoning that that's what the real thing does, applying the same thinking to an A3, A4 or anything else of LNER origin that has a trailing axle doesn't quite make a good fit. The rear end isn't supposed to go anywhere, it sits there under the cab and behaves in a very rigid fashion (axle boxes excepted). Hornby's solution does what it should, staying still, and I'm sure I'm not the only one who prefers it to the Bachmann low relief idea despite the flangeless wheel. You could, of course, make the axle wobble about inside the fixed frame, as you would with a Comet chassis or similar giving the model a minimum radius of around 22", but that makes them awkward to put on the tracks, which is where the Hornby idea makes life rather simpler.
If a Britannia looks ridiculous with is trailing truck staying put bellow the cab, wouldn't an A3 look equally silly if its rear frames were made to move?
Apologies in advance if I've misinterpreted what has been meant in previous posts.

Cheers
Paul

[Mersey508138]

The main reason I would make the trailing wheels pivot would be to make it easier for a loco fitted with flanged wheels under the cab to reverse over points without derailing as the wheels need to be able to stear the loco even if the cartazzi frame doesn't pivot and I would rather cut the metal block that holds the rear wheels off the chassis and adapt is as necessary to allow the wheels to have full movement.

The other point to this as far as I can see is that even if the rear bogie frame did pivot along with the wheels is that for those who want flanged wheels but only have standard train set curves is that the loco would then be able to traverse the curves without derailing because the non flanged wheels look completely ridiculous hanging off the track and they can often derail a loco when it goes back onto a straight section and they can also cause shorts on points.

[mick b]

The main reason I would make the trailing wheels pivot would be to make it easier for a loco fitted with flanged wheels under the cab to reverse over points without derailing as the wheels need to be able to stear the loco even if the cartazzi frame doesn't pivot and I would rather cut the metal block that holds the rear wheels off the chassis and adapt is as necessary to allow the wheels to have full movement.

The other point to this as far as I can see is that even if the rear bogie frame did pivot along with the wheels is that for those who want flanged wheels but only have standard train set curves is that the loco would then be able to traverse the curves without derailing because the non flanged wheels look completely ridiculous hanging off the track and they can often derail a loco when it goes back onto a straight section and they can also cause shorts on points.

Depends on what you call full movement. Any swing is restricted by the fixed frames and would be minimal at best.

Never had a problem with the non flanged wheels shorting anything, the clearance is at least 1mm or more. If they are shorting on track you must have misaligned track/points.