What causes the "whoom, whoom, whoom" sound inside 175s/170s?

[anamyd]

As per title, does anyone know what causes the "whoom, whoom, whoom" sound at the engine speed inside 175s/170s?

 

[Bletchleyite]

As per title, does anyone know what causes the "whoom, whoom, whoom" sound at the engine speed inside 175s/170s?

I'm not 100% sure which sound you mean, but it's probably resonation between engine vibration and the bodywork.

 

[anamyd]

I'm not 100% sure which sound you mean, but it's probably resonation between engine vibration and the bodywork.

It's that "whoom" sound that repeats every three quarters of a second or so (not sure why though). Somewhat makes sense though, thanks :P

 

[LNW-GW Joint]

It's that "whoom" sound that repeats every three quarters of a second or so (not sure why though). Somewhat makes sense though, thanks :P

185s do something similar too, can be very irritating when they are coasting downhill or up to a stop.
22x don't seem to do it, despite using the same engine.

 

[gimmea50anyday]

Is it to do with engine braking? 22x use electrical transmission whereas 170, 175 and 185 are mechanical so the engines can be used as a brake as well as providing traction power. Alternatively is it not the engine hunting where the revs keep pitching up and down?

 

[AzureOtsu]

I'm not 100% sure which sound you mean, but it's probably resonation between engine vibration and the bodywork.

I think this best describes it.

 

[507020]

It's that "whoom" sound that repeats every three quarters of a second or so (not sure why though). Somewhat makes sense though, thanks :P

I’ve got no idea what it is but I can confirm that there definitely is a repeating “whoom” sound every three quarters of a second on 175s. Not sure about 170s because I’ve only been on one once from York to Harrogate.

 

[physics34]

Could it be the air con?

 

[hexagon789]

Is it to do with engine braking? 22x use electrical transmission whereas 170, 175 and 185 are mechanical so the engines can be used as a brake as well as providing traction power. Alternatively is it not the engine hunting where the revs keep pitching up and down?

170s don't have a retarder and the one on 175s has been disabled for most of their lives.

As per title, does anyone know what causes the "whoom, whoom, whoom" sound at the engine speed inside 175s/170s?

I suspect it's vibration and resonance in the bodywork, 170s certainly do this frequently at mid-range rpm - literally everything that can vibrate does on some units.

 

[warwickshire]

Chiltern railways 168 have it as well. Same as East Midlands/West Midlands class 170s.
Maybe something very common on 168s and 170s.

 

[warwickshire]

170s don't have a retarder and the one on 175s has been disabled for most of their lives.


I suspect it's vibration and resonance in the bodywork, 170s certainly do this frequently at mid-range rpm - literally everything that can vibrate does on some units.

Yes I have noticed this as well. Including Chiltern railways 168s also.

 

[anamyd]

Is it to do with engine braking? 22x use electrical transmission whereas 170, 175 and 185 are mechanical so the engines can be used as a brake as well as providing traction power. Alternatively is it not the engine hunting where the revs keep pitching up and down?

The sound is within a certain (range of) steady engine speed(s). That also seems to link with others' suggestions of the bodies resonating from the engine sound, as that will be at (a) certain frequency(ies). There must be a more specific reason it does it with the "whooms", but thanks for everyone's responses

 

[Tynwald]

Engine noise

== Doublepost prevention - post automatically merged: 28 Jun 2022 ==

And cooler group load.

 

[anamyd]

Yes I have noticed this as well. Including Chiltern railways 168s also.

Sorry, by 170 I meant 168/170/171.

 

[anamyd]

Engine noise

== Doublepost prevention - post automatically merged: 28 Jun 2022 ==

And cooler group load.

I've heard about the cooler group in relation to 175s(/180s?), so this has something to do with the "whooms"?

 

[satisnek]

Ah, is this the reason why 170s were called 'washing machines' when new? (By a very small number of people, admittedly...)

 

[warwickshire]

Ah, is this the reason why 170s were called 'washing machines' when new? (By a very small number of people, admittedly...)

And sound like them especially when travelling In the Cross country ones.
Like we are all in the Laundrette.
However at Cambridge days of the excellent sounds of a 317 departing on full motor screem. With a Cross country 170 going in opposite direction making the classic sounds of a washing machine are very sadly. Have just finished. Another era gone.

 

[Mat17]

I know the sound you mean. For those familiar with Indiana Jones and the Raiders of the Lost Ark, it reminds me of that scene where the ark is in the ship's cargo hold inside the crate and it starts making that exact noise, which affects all the rats scurrying around.