Hornby Britannia R3865 Oliver Cromwell bad running, no idea what the cause is. (brand new model)

[mikesndbs]

Hi

 

Gutted, here is loco number two after the first one had to be sent back.

 

I've checked everything, coupling rods are not locking, everything seems to be fine, wheels are not bent etc, etc.

Yet it does this and it is horrid at slow speeds and twitches at higher ones.

 

I am so hoping this is a simple solvable issue.

 

 

 

I am posting this to see if anyone has an idea what might be going wrong here. The loco a brand new Hornby R3865 has been like this from the start and despite a good bit of running it continues. The middle pair of driving wheels seem to pump hard to one side at the same time the loco slows. At speed it’s not too bad but viewed from above it can be seen to twitch. The big problems come at low speed when this has a significant bad effect on running. This is my 2nd loco the first was broken on arrival and was sent back. I’ve fitted details etc. now and kind of think sending it back I will probably get something even worse. Have to say I am really getting put off buying new stuff, if it was £50 or so you might look past it but nearly £200 it should be perfect. Thanks for looking.

[roythebus1]

See my reply on the other post.

[Il Grifone]

That looks like a quartering and/or off true wheel  problem to me. At £200 it should go straight back!

 

The lack of motion in the eccentric rods suggests the real thing wouldn't work either. Incorrect positioning of the return cranks on a model is not acceptable in the 21st century IMHO.

You can see what I mean here. The Dublo model for all its faults has got it right (This also applies to the green. Hornby's is awful! - unless it's the lighting?). It should not be forgotten that the Dublo model was intended as a toy and cost around half as much in real terms.

 

 

Edited March 21, 2021 by Il Grifone

[mikesndbs]

37 minutes ago, Il Grifone said:

That looks like a quartering and/or off true wheel  problem to me. At £200 it should go straight back!

 

The lack of motion in the eccentric rods suggests the real thing wouldn't work either. Incorrect positioning of the return cranks on a model is not acceptable in the 21st century IMHO.

You can see what I mean here. The Dublo model for all its faults has got it right (This also applies to the green. Hornby's is awful! - unless it's the lighting?). It should not be forgotten that the Dublo model was intended as a toy and cost around half as much in real terms.

 

 

 

Thanks, do you think the return crank os on wrong on my model then?

[Il Grifone]

It's definitely wrong, but AFAIK that is how the models are made and there is nothing that can be done about it.

Here's the real thing for comparison:

 

 

[great central]

2 hours ago, mikesndbs said:

 

Thanks, do you think the return crank os on wrong on my model then?

 

This has been a problem since production was moved to China as far as I'm aware. Whether it's down to the people in this country placing the orders with the factories or, as I suspect, the extra costs in getting it right I don't know.

It's been pointed out continually by all the magazines doing reviews and by people on forums like this, even with pre-production samples, but they still come out wrong.

I think it's simply a case of 'most people are unlikely to notice so we'll leave it like that' 

I've corrected several of my Bachmann locos but only investigated one Hornby example so far which didn't seem to offer a relatively simple solution. As I have nowhere to run anything it's fairly academic to me anyway.

 

 

[mikesndbs]

Hi all, I took a couple of close up photos of the valve gear in the same position.

Can anyone spot a problem?

Just wondering if there is anything obvious. 

 

 

[great central]

23 minutes ago, mikesndbs said:

Hi all, I took a couple of close up photos of the valve gear in the same position.

Can anyone spot a problem?

Just wondering if there is anything obvious. 

 

 

 

The slidebar angle looks to be wrong, it's too steeply inclined and the con rod will foul it. The slidebar should point to just above the centre of the driven wheel, so that the piston rod is parallel with it when the wheels are at the rear of their revolution. 

I've dug out my earlier one which I'm in the process of renumbering, luckily the wheels are set pretty much right to show what I mean.

Whether that's a design or assembly problem I can't say but whichever it's not good. The Bachmann 04s suffer from the same problem and that's definitely down to design.

Apologies that the photo is on it's side, can't figure out why at the moment.

[Il Grifone]

The RHS is about right, but the angle on the LHS is only about half the right value except that it leans backwards Tri-ang fashion*. With the wheel crank pointed downwards, the return crank usually should point forward** so that the eccentric rod pivot is horizontally in line with the wheel centre.

 

* Tri-ang had only one casting for the wheels which obviously resulted in one side being incorrect. This possibly saved perhaps a penny per locomotive??

 

** Something to do with inside or outside admission. When I studied mechanical engineering, steam was 'old hat' and not mentioned. Unfortunately I lost the book I was given which explained it all during a house move!    The only class I can think of offhand is the rebuilt West Country/Battle of Britain.

Of course, the Superior Railway (see below) favoured Stephenson gear and tucked it away tidily between the frames.

[great central]

8 minutes ago, Il Grifone said:

The RHS is about right, but the angle on the LHS is only about half the right value except that it leans backwards Tri-ang fashion*. With the wheel crank pointed downwards, the return crank usually should point forward** so that the eccentric rod pivot is horizontally in line with the wheel centre.

 

* Tri-ang had only one casting for the wheels which obviously resulted in one side being incorrect. This possibly saved perhaps a penny per locomotive??

 

** Something to do with inside or outside admission. When I studied mechanical engineering, steam was 'old hat' and not mentioned. Unfortunately I lost the book I was given which explained it all during a house move!    The only class I can think of offhand is the rebuilt West Country/Battle of Britain.

Of course, the Superior Railway (see below) favoured Stephenson gear and tucked it away tidily between the frames.

 

Err, from my memory, all Triang valve gear was correctly set up. With the wheels at bottom dead centre the eccentric crank should face forwards on both sides.

This was never an issue until production was moved to China.

The exceptions in model terms being the Bulleid Pacifics and the Bachmann N class I think.

 

[great central]

There's some excellent footage appeared here, including Britannias moving around Carnforth shed yard, to give an idea of how a model should look when in motion.

 

[Il Grifone]

On Tri-ang locomotives, on one side the return crank faces forward and rearwards on the other.

 

Here's a service sheet which clearly shows the position of the valve gear.

 

http://www.hornbyguide.com/service_sheet_details.asp?sheetid=136

 

And a service video for a Tri-ang Britannia. (Don't use anything metallic to clean the commutator slots and IMHO he's a bit overgenerous with the abrasives and the oil.) As can be seen the return crank leans rearwards on the RHS and forwards on the LHS.

 

 

Edited March 21, 2021 by Il Grifone

[mikesndbs]

2 hours ago, great central said:

 

The slidebar angle looks to be wrong, it's too steeply inclined and the con rod will foul it. The slidebar should point to just above the centre of the driven wheel, so that the piston rod is parallel with it when the wheels are at the rear of their revolution. 

I've dug out my earlier one which I'm in the process of renumbering, luckily the wheels are set pretty much right to show what I mean.

Whether that's a design or assembly problem I can't say but whichever it's not good. The Bachmann 04s suffer from the same problem and that's definitely down to design.

Apologies that the photo is on it's side, can't figure out why at the moment.

 

Hi, I tried to replicate yours.

I feel it looks the same but could be wrong?

 

 

 

[mikesndbs]

2 hours ago, Il Grifone said:

The RHS is about right, but the angle on the LHS is only about half the right value except that it leans backwards Tri-ang fashion*. With the wheel crank pointed downwards, the return crank usually should point forward** so that the eccentric rod pivot is horizontally in line with the wheel centre.

 

* Tri-ang had only one casting for the wheels which obviously resulted in one side being incorrect. This possibly saved perhaps a penny per locomotive??

 

** Something to do with inside or outside admission. When I studied mechanical engineering, steam was 'old hat' and not mentioned. Unfortunately I lost the book I was given which explained it all during a house move!    The only class I can think of offhand is the rebuilt West Country/Battle of Britain.

Of course, the Superior Railway (see below) favoured Stephenson gear and tucked it away tidily between the frames.

 

 

Hi, is this how you mean?

 

 

[mikesndbs]

Hmm, I think I see what you mean, looking at the full screen here https://www.stationroadsteam.com/5-inch-britannia-stock-code-5156/fullscreen/1/

 

So with wheels cranks at the bottom the Eccentric Crank should be leaning forward and the expansion link leaning back at the top.

 

This then suggests that the wheels have been put on the axel wrongly as there are flats on the crank pin to locate them as shown above

[great central]

5 minutes ago, mikesndbs said:

Hmm, I think I see what you mean, looking at the full screen here https://www.stationroadsteam.com/5-inch-britannia-stock-code-5156/fullscreen/1/

 

So with wheels cranks at the bottom the Eccentric Crank should be leaning forward and the expansion link leaning back at the top.

 

This then suggests that the wheels have been put on the axel wrongly as there are flats on the crank pin to locate them as shown above

 

It looks like, I'm afraid, the whole thing is a bit of a c**k up. The wheels must be right otherwise the coupling rods would be out of sync. If there are flats on the crankpins for location they are what's wrong.

The left hand slide bar is definitely misaligned as well.

Something to raise direct with Hornby to my mind. These are basic design or assembly faults and, in my opinion, the loco is not correct as a model, so unacceptable.

[mikesndbs]

Ok, this is weird, I was watching the middle pair pumping back and forth then changed me position to observe that not only were they going back and forth but also up and down!!!

 

This led me to look at the bottom plate(s) and the securing method.

 

The break roding and shoes come off as one bit, under is the pick up plate.

Only two screws are used to secure all of this.

The end furthest away from the gear drive (so the front of the loco) looks to be split?

Anyway I experimented with sliding it about very slightly with the screws in lose.

 

I found a point where the concentric running stopped and quickly tightened the screws.

 

While the middle pair still pull from side to side they do not go up and down anymore and the loco can now crawl (albeit noisily) without stalling.

 

Certainly a poor design, the tolerance for adjustment is only that allowed by the slack in the screw holes.

I did make sure that the wires went directly down the hole in the chassis rather than being trapped between the two plates as was clearly obvious before I did this.

 

 

[Il Grifone]

The slide bars are out of line with the cylinders. As they are the pistons would be unable to slide inside the cylinders. The connecting rod should move above and below the centre line by equal amounts during the rotation of the wheel.

 

The model is excellent, but if the motion does not operate correctly the overall effect is spoilt. After all, the fine detail can only be appreciated in close up. (Just my opinion of course - others may differ.)

 

I've just noticed the valve gear is set slightly in reverse. Now I am being pedantic?

Edited March 21, 2021 by Il Grifone

[mikesndbs]

2 hours ago, Il Grifone said:

The slide bars are out of line with the cylinders. As they are the pistons would be unable to slide inside the cylinders. The connecting rod should move above and below the centre line by equal amounts during the rotation of the wheel.

 

The model is excellent, but if the motion does not operate correctly the overall effect is spoilt. After all, the fine detail can only be appreciated in close up. (Just my opinion of course - others may differ.)

 

I've just noticed the valve gear is set slightly in reverse. Now I am being pedantic?

 

Question is are they all like mine or are some correct, can anyone else post similar photos of theirs? 

[Grovenor]

Some will be correct, just depends on which way round the centre wheelset is fitted, probably no-one has told the assemblers that it matters.

On the old models with two identical wheels it didn't matter as one side would be wrong regardless. On these newer models where Hornby have noted the criticism and corrected it they can be assembled correct on both sides or wrong on both sides. To correct it just remove the centre wheelset and turn it round so the right wheel becomes the left wheel and vice versa.

Edited March 22, 2021 by Grovenor

[sjp23480]

I don't have the latest Oliver Cromwell, but I do have one from the 15 Guinea Special train pack. 

Worrying it might be similarly affected? 

[cypherman]

Hi all,

I think the only way that this engine will ever run properly is if you dump the Hornby chassis and build a new one.. Do High Level or Perseverance do a chassis kit for the Britannia.

After watching Jenny's video about the difference between the H/D and Hornby Duchess(Yes I know it is not a Britannia she is talking about). It is fine saying Oh this looks much better than this or that and this is finer than this or that. But if it does not work and it is clearly due to a poor manufacturing issues it is about as good as having 4 flat tyres in an F1 race. You can guild a T**D as much as you like. But it is still a T**D. And clearly IMHO this Britannia is one.

Edited March 23, 2021 by cypherman

[Il Grifone]

On 22/03/2021 at 22:34, Grovenor said:

Some will be correct, just depends on which way round the centre wheelset is fitted, probably no-one has told the assemblers that it matters.

On the old models with two identical wheels it didn't matter as one side would be wrong regardless. On these newer models where Hornby have noted the criticism and corrected it they can be assembled correct on both sides or wrong on both sides. To correct it just remove the centre wheelset and turn it round so the right wheel becomes the left wheel and vice versa.

 

Unfortunately it doesn't seem to be that simple. It's not just that the return crank is mounted to point backwards, but that the angle at which it is set is incorrect. Whether there is any way to adjust this I don't know. (SWMBO would have a fit if I were to spend that much on a loco!)

The Tri-ang ones can be adjusted by pushing out the offending crank pin and filing the lugs on the inside of the wheel. It can then be refitted and fixed with Araldite (or just replace the wheels with something better*).

* Mine is getting a set of HD 4MT drivers. They are  a bit undersize for a Britannia, but do look like BR standard wheels. The undersize will help with the excessive buffer height.

[Grovenor]

At least tuning the wheelset end for end makes the backward leaning return cranks lean forward. The exact angle is not going to affect the running, and I don't think any error in that angle can be accurately assessed from the pictures so far available. If the crankpin design is similar to the black 5 then changing the angle would not be easy but could be done. Quite a  long period between the two models so I've no idea if they are the same.

[mikesndbs]

Hi guys, so a good conclusion to my problems, here is what I did

 

 

If anyone has any other comments about the valve gear I'd be most interested.