Performance of multiple MUs

[ic31420]

Whilst watching a couple of 150+153 combinations climbing a hill a few days ago I was left pondering if the driver can feel a difference in performance when driving say 2x150s as opposed to a single 150.

I imagine any difference would be more pronounced at higher speeds in that the units would be able to accelerate better say from 60-70mph and maintain a higher balancing speed on climbs as aerodynamic drag will be less "per car" or per installed hp.

What about pairing a shorter lower top speed faster accelerating unit with a higher speed longer geared unit. Does the shorter geared unit push the other unit along perceptably?

 

[notadriver]

Whilst watching a couple of 150+153 combinations climbing a hill a few days ago I was left pondering if the driver can feel a difference in performance when driving say 2x150s as opposed to a single 150.

I imagine any difference would be more pronounced at higher speeds in that the units would be able to accelerate better say from 60-70mph and maintain a higher balancing speed on climbs as aerodynamic drag will be less "per car" or per installed hp.

What about pairing a shorter lower top speed faster accelerating unit with a higher speed longer geared unit. Does the shorter geared unit push the other unit along perceptably?

Very interesting what climb was this ?

 

[30907]

I would think the aerodynamic drag factor would be marginal on any significant gradient (having endured 150s through Darwen!).
Can't comment on gearing, leave that to a driver...

 

[ic31420]

Very interesting what climb was this ?

It was actually the climb out of Bolton on the Ribble line toward Darwen. Hardly high speed I give you, but it was what set the train of thought in progress.

 

[Llama]

You'll notice the reduced proportional aerodynamic dtah effect you describe slightly at higher speeds, for instance between Salford Crescent and Moses Gate going up towards Bolton you might just get 75mph out of a single 150, whereas a pair should have no problem reaching 75.

From Bolton towards Darwen the gradient is so steep that the aerodynamic drag effect doesn't really come in to it as attainable speed is so low (~45mph with 150/153/156).

153s on their own are usually noticeably slower than other units, perhaps for the fact that aerodynamic drag is more pronounced than it would be on a two car set, although 153s are about 10% heavier and their brakes much slower to release than 150/156.

142s being very light are at the mercy of aerodynamic drag too, a single 142 might just struggle to 65-70 between Salford Crescent and Bolton, a pair is noticeably better and three or four of them positively lively.

Going to Southport where the line is very open and flat between Parbold and Pool Hey the effects of the wind direction made themselves known very obviously on single 142s - it was often possible to get up to 70mph one way but not the other.

 

[PHILIPE]

Just for interest and hardly worth creating a new thread 5V98 19+53 Shrewsbury to Canton (Sunday train normally but TFW running an amended Sunday COVID service) was formed this evening of:- 150260, 150227, 153362, 153323, 153314 + 153303.
What a lash up

 

[cossie4i]

395s are noticeably faster as a 12car through the single bore tunnels between St Pancras and Dagenham.

 

[sd0733]

Just for interest and hardly worth creating a new thread 5V98 19+53 Shrewsbury to Canton (Sunday train normally but TFW running an amended Sunday COVID service) was formed this evening of:- 150260, 150227, 153362, 153323, 153314 + 153303.
What a lash up

260 was in the same platform at Shrewsbury but didnt go with the rest of them and ran on it's own to Abbey Foregate for the night. Still 4x153 and a 150 an impressive formation!

 

[PHILIPE]

There was a lash up of 5x153s from Carmarthen to Canton yesterday