Minimum trailing vehicles for loco to run at line/max speed?

[G-BOAF]

It my understanding that light engines are often restrited below line speed or rated maximum speed, as without trailing vehicles, stopping distances are longer than that assumed at line speed and as designed with signal distances etc.

 

So my question is what is the minimum number of vehicles trailing required for line speed to be reached? e.g. how many vehicles would a Class 67 or 91 need to run at 125 on the ECML, A class 90 or 87 at 110, or a Deltic or Class 68 at 100 (assuming that in all cases light engine speeds will be below the line speed or class rated max)

 

I haven't seen this discussed, and a not-so-quick google search has not yielded a result. But happy to be provided with a link to relavent discussions/materials

 

Edit - should be in questions not discussions.... how do i move??

EDIT - Thanks Mods for moving!

Edited August 30, 2021 by G-BOAF

[iands]

AIUI it is to do with brake force. I think light engines are restricted to 75mph max. The trailing load will improve the overall braking, allowing for increased speed. Sorry, but I don't know how it is calculated or how the required number of vehicles is determined. Will be interesting to find out and I'm sure someone with the relevant knowledge will be along soon to inform us. 

[hexagon789]

13 hours ago, G-BOAF said:

It my understanding that light engines are often restrited below line speed or rated maximum speed, as without trailing vehicles, stopping distances are longer than that assumed at line speed and as designed with signal distances etc.

 

So my question is what is the minimum number of vehicles trailing required for line speed to be reached? e.g. how many vehicles would a Class 67 or 91 need to run at 125 on the ECML, A class 90 or 87 at 110, or a Deltic or Class 68 at 100 (assuming that in all cases light engine speeds will be below the line speed or class rated max)

 

I haven't seen this discussed, and a not-so-quick google search has not yielded a result. But happy to be provided with a link to relavent discussions/materials

 

Edit - should be in questions not discussions.... how do i move??

Light engine is 75 where linespeed is 90 or greater, if it's 85 or less then the light engine restriction is 60mph.

 

67s and 68s are allowed 100 light engine as they are disc braked and have a greater brakeforce than traditional locos. Chiltern make good use of that and I imagine it's also useful for 67s on Thunderbird duties.

 

For loco hauled formations - 3 coaches or less is treated as light engine.

 

4, 5 or 6 coaches is 90mph where linespeed is 100 or greater.

 

80mph where linespeed is 90 or 95mph.

 

75mph where linespeed is 80 or 85mph.

 

7 vehicles or more are unrestricted, hence why the 47+Mk2 Cross-Country trains were 7 coaches.

 

 

Edited August 29, 2021 by hexagon789

[dhjgreen]

14 hours ago, G-BOAF said:

Edit - should be in questions not discussions.... how do i move?

Report it so a Mod can see your request, done it for you this time.