HST 'Jolt'...?

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Hello all.

Maybe a bit of an odd one this but im sure someone can help me.
Fortunately I have been lucky enough to travel via rail for the past few months thanks to my job, (Exeter to London).

It's something I've never really noticed but on all my journeys so far this year, when travelling relatively slow the train would appear to 'jump' or 'jolt', like when you switch off a car engine in-gear, well sort of? It only happens a couple of times...

Anyone know why this is, i'll be waiting for it again tomorrow on my return trip. I have gone via SWT on a 159 but not experienced it, only the 43's.

Thanks,
 
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PaxVobiscum

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It's something I've never really noticed but on all my journeys so far this year, when travelling relatively slow the train would appear to 'jump' or 'jolt', like when you switch off a car engine in-gear, well sort of? It only happens a couple of times...
Might be the couplings? (getting on a bit, like me). When the train accelerates or decelerates there can be a 'domino' bump from front to back or back to front. Shouldn't happen really but I've noticed it a bit on EC stock recently as well. Not enough to spill your your tea, but enough to be felt.
 

mralexn

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Believe me, Greater Anglia 90's are way worse
Sit in the most rear carriage and every time you leave a station (from a stand) you will get a massive jolt!
 

ainsworth74

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Believe me, Greater Anglia 90's are way worse
Sit in the most rear carriage and every time you leave a station (from a stand) you will get a massive jolt!
That's simply due to the slack in the couplings being taken up as the train moves away and you tend to get it on just about all LHCS though in my experience it tends to be more noticeable when the locomotive is pulling rather than pushing.

As for HSTs it's due (in my understanding) to the fact that the power cars tend not to power up at the same time, there is a slight delay between the front power car pulling the train forwards and the rear power car joining in by pushing from the rear. This has the effect of causing the slack in the couplings to be taken up causing a slight jolt as the train moves away.
 

mralexn

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That's simply due to the slack in the couplings being taken up as the train moves away and you tend to get it on just about all LHCS though in my experience it tends to be more noticeable when the locomotive is pulling rather than pushing.

As for HSTs it's due (in my understanding) to the fact that the power cars tend not to power up at the same time, there is a slight delay between the front power car pulling the train forwards and the rear power car joining in by pushing from the rear. This has the effect of causing the slack in the couplings to be taken up causing a slight jolt as the train moves away.
your right, 5 second delay :)
 

yorkie

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It's something I've never really noticed but on all my journeys so far this year, when travelling relatively slow the train would appear to 'jump' or 'jolt'...
Yes, this happens some times. From memory, perhaps most commonly on EMT. My last HST journey was on XC (1703 Birmingham-York last Saturday) and it was extremely smooth, not even the slightest jolt, we also arrived early at every station (although at both Derby and Wakefield we had to wait a few minutes at each for a platform to become available).
 

dstrat

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Yeah, sit in the rear of a 91/Mk4 combo and everytime you pull off with the 91 behind you it just rams into coach B or whatever. As said, careful with your tea!

It does though appear to happen when doing 125 ish....not sure if that is sudden acceleration, breaking or wheelslip tho.
 

DownSouth

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It does though appear to happen when doing 125 ish....not sure if that is sudden acceleration, breaking or wheelslip tho.
That would just be normal motion, from the train not being entirely rigid.

The only way it could be absent when a push-pull train is operating in loco-shoved mode (as opposed to loco-hauled) is if the motion was perfectly smooth and free from external forces like air resistance, or if it was perfectly rigid.
 
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Oh yes of course, the slack between the couplings, should have known better really. Thanks everyone for the replies.

Just on my way home now, haven't felt it yet and just about to arrive into Taunton. Very smooth journey.

Thanks
 
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Hydro

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Blimey, if you want a good jolt, try push-pull 73's hitting a gap whilst under full power.
 

DaveNewcastle

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Were you aware that there was an almost identical thread last month?
Its here : xc hst violent jurking?.
It took a few posts to see what the OP was asking about, but some of the responses may be relevant to this discussion too.

[Frankly, the worst 'jolts' at the moment seem to be over Colton Junction at linespeed. I've seen one FC host be thrown from one one side to the other, using the two luggage racks as supports, one then the other, in turn, after which the driver explained that he'd actually eased off power to reduce speed from 125 to 110mph in anticipation of the junction! It will probs get a TSR soon just like the equally horrendous Temple Hirsts Jn where NR's response to the state of the track has been to slap an 80 limit on it for the past 3 months or so. But I appreciate that's not what this thread is about].
 
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tsr

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Similar effects can be felt on 442s leaving Gatwick Airport in the up direction, for some reason.

It's not the points, before anyone asks, although I know there have been issues with "rough riding" over these in recent months, leading to some customer complaints and a few speed restrictions.
 
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WatcherZero

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You get the same thing in cars with turbos, turbo-lag, you floor the pedal and accelerate slowly for a few seconds then the turbo kicks in and suddenly your in the back of the seat.
 

185

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Anything that was ex-Intercity before MK4 seemed to jolt, it was part of the fun!

(I'm picturing Clarkson deliberately bumping into May on Top Gear) ;)
 
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Oh yes of course, the slack between the couplings, should have known better really. Thanks everyone for the replies.

Just on my way home now, haven't felt it yet and just about to arrive into Taunton. Very smooth journey.

Thanks
Ha! I spoke too soon...:) 'Jolted' a couple times leaving Tiverton Parkway, just when I thought it would be a 'jolt-less' trip!
 
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