Tornado

So what else caused that blue effect so clearly shown on the photo?

 

Its not that high tho. 300C is not crazy hot for something with a meting point of circa 1300C.

With the greatest respect, you are wrong.

It may be surprising to some, but this is a well understood phenomenon. Metals in general are very elastic and very expressive when strain hardened and bent. I think its also easy to forget just what a trauma this component was going through in its last seconds of life.

A sticking valve at one end, and the driving motion at the other, neither of which are taking no for an answer. The poor old combi lever didnt have choice in the matter.

 

Only other theory - being dragged along the ground ?
The mystery to me is, once the Combi lever went, why would the cross head post go... (or if the cross head post went, why would the combi lever also go) unless at there has been some incredibly unlucky alignment with an oncoming track feature at the instance of it falling... perhaps we will never know.

 

My own theory from earlier is that the union link being free once the combi lever let go, found something to buddy up to, imparting an incredibly large force on the cross head on the return stroke.

Remember you have the entire reciprocating mass acting through the cross head, and the union link is very stiff, so the cross head fails from a shock load impact when the union link digs into a neighboring component.

Either way, being a single shear part with a hole for the gudgeon pin, it was never going to take that force and so fractured. There is no bluing there, implying fast fracture.

1. Valve sticks.
2. Bending starts.
3. Combi lever heats.
4. Combi lever breaks.
5.Union link becomes free.
6. Union link finds and equal and opposite force.
7. UL imparts the reciprocating motion and resultant force to the Crosshead.
8. Crosshead fractures.
9. Brakes go on.

Thats how I see it. I may well be wrong OFC, but if anyone has a better theory and it is borne out in the official report, il buy them a pint.

 

The crosshead arm was also welded to the crosshead on both sides.

 

nearly what I think too with a few minor adjustments:

1. Valve sticks.
2. Bending starts.
3. Combi lever heats.
4. Combi lever breaks.
5.Union link and lower part of Combi lever becomes free.
6. Union link/lower part of Combi lever finds and equal and opposite force. (possibly another part of the locomotive but could be the ground or track but seams less likely)
7. UL/part CL imparts the reciprocating motion and resultant force to the Crosshead.
8. Crosshead fractures..(BIG BANG!)
9. Brakes go on.

 

Nowhere remotely close to enough energy.

Let’s assume that lump of metal weighs m kg.

90mph is 40m/s as near as dammit. So the energy available as it left the engine =1/2 m.v.v = 800J/kg

Specific heat capacity of steel is 500 J/kg/K pretty much. So 800J/kg is sufficient to raise the temperature of m kg of steel by about 1.6K - a negligible amount, even if the energy coupling between steel and ground was perfect so all the energy went into heat. In practice most of it would be noise. Even were it dragged for a considerable distance while still attached to the loco, the energy coupling of being dragged along a very bumpy surface (ballast) would be very inefficient - most of the energy would be in noise and causing it to jump around (movement) every time it hit a stone and very little in heating. What heat was released would be very small flakes of metal released as sparks, not an even temperature rise throughout the substantial mass of metal.

Short answer - when that bit of steel hit the ballast, there would be a loud clattering but negligible heat rise. Whatever heated it up happened while it was still attached to the loco.

Tom

 

Looking at photos of A1s I'm not sure it would even reach the ballast when hanging straight down. There's plenty of other solid bits for it to hit whilst flailing about. Bogie and bogie axle, cylinder block and rear cover, possibly even a frame stretcher behind and well below the slide bars.

 

Some wonderful speculation going on here! All this talk of heating to 300°C. What temperature does that superheated steam get to in the valve chest? A tad more than this. OK, we are outside the steam chest but we are not talking about excessive operating temperatures at 300°C.
No mention has yet been made of what other damage was sustained in the incident. My gut feeling is that it is not confined to the valve, combination lever, union link and crosshead but I don't know.
For my bit of speculation as to the prime cause of the failure, it could be any number of things but my Mars Bar is on a little check valve. I'll be quite happy to be told I'm wrong, though.

 

I wasn't going to comment until the report came out but my gut reaction is very much like yours, an initial major component failure would be most unlikely. A locomotive equivalent of a horseshoe nail moment looks to be far more likely. We'll find out soon enough.

 

Do you mean a non return valve? Such as might be found at various points in the lubrication system?

 

You could say that. Pure speculation on my part, though, and based on no evidence, only experience. I might end up having to buy a Mars Bar for someone.

 

FROM Facebook A statement on behalf of the The A1 Steam Locomotive Trust.

The A1 Steam Locomotive Trust would like to apologise for the disruption caused to passengers travelling on ‘The Ebor Flyer’ on Saturday 14th April 2018 and passengers on other trains impacted by No. 60163 Tornado’s breakdown. The locomotive came to a stop just south of Sandy with a broken combination lever. Investigations have so far revealed that this was due to the middle piston valve overheating and binding in the valve chest. The root cause is not yet fully clear, but it is likely that insufficient lubrication was an issue. Investigations continue to establish the cause of failure in the lubrication system and any contributing factors.

Tornado has run many miles since winter maintenance with no obvious issues in this area. Whilst we have been asked if the higher speed was a factor in the failure, at present we believe it not to be. It probably happened slightly earlier in the journey than if running at lower speed, but it most likely would still have happened.

Because we did not deliver the day out we hoped to for passengers travelling on ‘The Ebor Flyer’, we have given each passenger a voucher with discount off a future Tornado-hauled railtour. Furthermore, we are looking at the option of re-running the train in the future with a repaired Tornado and will ensure all passenger on ‘The Ebor Flyer’ get the first chance to book tickets.

Following on from this, we have postponed our visit to the Midland Railway Centre (Saturday 21st April 2018) and we have also postponed ‘The Ynys Môn Express’ which was due to run on Saturday 28th April 2018, a date is yet to be confirmed as to when this tour will be rescheduled. Additionally, we regret that we will be rearranging the Tornado Team day that was due to be at the Nene Valley Railway on Saturday 12th May 2018. – again a rescheduled date will be announced in due course.

We are now concentrating our efforts on continuing the investigation and undertaking the necessary repairs.

You can support the work of The A1 Steam Locomotive Trust by becoming one of our monthly Covenantors and donating from £10.00 per month towards No. 60163 Tornado. This is our core fundraising initiative and we have around 1,200 people who regularly donate towards the maintenance and upkeep of Tornado. For more information on how you can support the Trust in this way please visit https://www.a1steam.com/become-a-covenantor/ or to make a one-off Donation, please click here https://www.paypal.com/fundraiser/charity/128932 , call 01325 460163 or email enquiries@a1steam.com.

 

You have to applaud A1ST openness, level of detail and providing information about its future availability

 

You can stick your Mars Bar up your @rse!

If it was a stick of liquorice, though, that's a totally different matter!

And the check valve is as good a theory as any other, although still only a theory.

 

A stick of liquorice it is, then. It isn't a theory so much as an educated guess.

 

Now with all that heat generated in the area at the top of the combination lever, now could it have been the Pin in the top of the combination lever where it goes through the intermediate valve spindle seizing prior to the rod breaking that caused all that heat. To me that would be a make much more sense.

 

More sense than the heat being generated through Strain Energy?

If something is seized, it is by definition constrained and so can not cause heat via friction. Friction requires relative movement.

 

Yes.

There would obviously have been considerable friction before it was unable to rotate.

 

The bushes(Bronze?) would have melted out long before the steel fractured. Leaving the combi lever free to rotate again if the valve was not stuck. More to the point, if that was the failure mechanism it would have failed around the pin, connecting it to the valve spindle in the same way at the Crosshead link.

Its failed due to strain energy which is more than sufficient to generate that level of heat.