Chiltern class 172 - Change to hydraulics transmission?

[Prestige15]

Apparently according to rail (issue 869). Chiltern's 172 have proved not to be as reliable as the 168's and there are talks of their being converted to hydraulics transmission.

Would that be a right move from CR?

 

[hexagon789]

Apparently according to rail (issue 869). Chiltern's 172 have proved not to be as reliable as the 168's and there are talks of their being converted to hydraulics transmission.

Would that be a right move from CR?

Well, while they accelerate quicker off the mark and are generally more fuel efficient with the six-speed ZF gearboxes, I believe that 172s are very poor at coasting having to be kept under power even downhill to maintain speed which I would imagine negates fuel savings on longer runs.

Assuming they converted to a Voith transmission as fitted to the 168s, then I imagine that would mean the two classes had more parts in common, though whether this would affect maintenance costs...

 

[Bletchleyite]

Weren't some of the 172s built with the Voith transmission? Was it LO's?

 

[hexagon789]

Weren't some of the 172s built with the Voith transmission? Was it LO's?

I thought all the 172s had ZF Ecomat 6-speed gearboxes?

 

[Bletchleyite]

I thought all the 172s had ZF Ecomat 6-speed gearboxes?

Maybe they do, I just recall hearing talk when they were new that one TOC was going for hydraulic - perhaps there was a change of plan.

 

[hexagon789]

Maybe they do, I just recall hearing talk when they were new that one TOC was going for hydraulic - perhaps there was a change of plan.

Maybe they did originally plan as such, but AFAIK all 172s have had the ZF transmission from new.

 

[superkev]

Well, while they accelerate quicker off the mark and are generally more fuel efficient with the six-speed ZF gearboxes, I believe that 172s are very poor at coasting having to be kept under power even downhill to maintain speed which I would imagine negates fuel savings on longer runs.

I believe the Voith 2 speed hydraulic as fitted to 14x 15x, 17x dmus only coasts in low ratio drive being direct in high. The ZF is reported to give around 10% fuel savings and be much quicker off the mark at the cost of more complexity. Perhaps Voith now make a more efficient comparable multi ratio box?
Pity the British SCG as fitted to heritage dmus and early Pacers is now defunct as there box was the most efficient of the lot. Sadly let down by insufficient development as engines got bigger.
K

 

[hexagon789]

I believe the Voith 2 speed hydraulic as fitted to 14x 15x, 17x dmus only coasts in low ratio drive being direct in high. The ZF is reported to give around 10% fuel savings and be much quicker off the mark at the cost of more complexity. Perhaps Voith now make a more efficient comparable multi ratio box?
Pity the British SCG as fitted to heritage dmus and early Pacers is now defunct as there box was the most efficient of the lot. Sadly let down by insufficient development as engines got bigger.
K

According to the document I have on the transmission as fitted to the 150s, both the torque convertor and fluid coupling can be emptied of oil as necessary when the power controller is closed and the unit freewheeling.

If Porterbrook's document on the 172s is correct, the 172s are quicker off the mark but take nearly two minutes longer to reach 100mph compared to a 168/170.

 

[Prestige15]

According to the document I have on the transmission as fitted to the 150s, both the torque convertor and fluid coupling can be emptied of oil as necessary when the power controller is closed and the unit freewheeling.

If Porterbrook's document on the 172s is correct, the 172s are quicker off the mark but take nearly two minutes longer to reach 100mph compared to a 168/170.

So by the look of it, I would make little difference on journey time if the 172 and 168 are opposite from eachother in terms of performance?

 

[gallafent]

So by the look of it, I would make little difference on journey time if the 172 and 168 are opposite from eachother in terms of performance?

… or perhaps one gets the best of both worlds by coupling one to t'other … at last we know why the “hybrid” (part mainline, part commuter) services exist

 

[hexagon789]

So by the look of it, I would make little difference on journey time if the 172 and 168 are opposite from eachother in terms of performance?

Presumably a 172 comes into its own on stopping services, because it can get away from a stand and built up a bit of speed quicker than a 168 but three trade-off is poorer high-speed performance.

 

[tomuk]

The most obvious thing to do would be to do a swap between WMT, TfW and Chiltern.
4x 2 car 172s Chiltern to WMT - All 172s are then based at Tyseley.
4x 2 car 196s WMT order transferred to TfW Civity order.
4x 2 car 170s TfW (ex Anglia) to Chiltern - Converted to 168s

 

[Kite159]

The most obvious thing to do would be to do a swap between WMT, TfW and Chiltern.
4x 2 car 172s Chiltern to WMT - All 172s are then based at Tyseley.
4x 2 car 196s WMT order transferred to TfW Civity order.
4x 2 car 170s TfW (ex Anglia) to Chiltern - Converted to 168s

Or even the 4x 172/1s to WMT with 4 of the 170/5s transferring the other way to be converted to 168s. Keeps all the 172s together at Tyseley and gives Chiltern a more uniform fleet of 168s & 165s

 

[fgwrich]

Presumably a 172 comes into its own on stopping services, because it can get away from a stand and built up a bit of speed quicker than a 168 but three trade-off is poorer high-speed performance.

It’s interesting that Chiltern should be looking to swap the transmissions over to a Hyrdraulic set up for their 172s as, as you touched upon above Hexagon, I believe they were initially ordered for their rapid acceleration - they were initially to be used on the stopping services into Marylebone allowing an increase of services stopping at Sudbury etc, without clogging up the “mainline”.

The other intreguing part to this story is that the last time Bombardier tried a more powerful 172 engine under a ScotRail 170, it rather didn’t take very well to the Hydraulic gearbox of the 170 IIRC.

 

[hexagon789]

It’s interesting that Chiltern should be looking to swap the transmissions over to a Hyrdraulic set up for their 172s as, as you touched upon above Hexagon, I believe they were initially ordered for their rapid acceleration - they were initially to be used on the stopping services into Marylebone allowing an increase of services stopping at Sudbury etc, without clogging up the “mainline”.

That's what I always understood, they were ordered for superior start-stop performance.

The other intreguing part to this story is that the last time Bombardier tried a more powerful 172 engine under a ScotRail 170, it rather didn’t take very well to the Hydraulic gearbox of the 170 IIRC.

I believe it caught fire IIRC. The NIR Class 4000s have the same engines as the 172s but uprated to 390kW (523hp) against 360kW (483hp).

In extension from that NIR's other DMU class - the 3000, has Voith hydraulic transmission. The 3000 and 4000s are used seemingly interchangeablely on individual services but only run in multiple within class in passenger service.

Presumably if NIR found the ZF transmission on the C4Ks problematic they would've changed to the same hydraulic transmission as the C3Ks by now as it would've meant near complete fleet commonality bar engine type.

 

[gallafent]

That's what I always understood, they were ordered for superior start-stop performance.

It would make sense I guess, but I'd have thought that there are so few in the (Chiltern) fleet that all the timings on the suburban services will be for 165s anyway, and so there's no advantage to be had on a normal day (though clearly being able to catch up lost time in the event of disruption is an advantage). If there could be some “172-only” services as suggested then I guess that would have made more sense, but I assume that didn't happen (I frequently see them on Oxford services!)

The idea upthread of the three-way swapping, losing the 172s in favour of some 170s (converted to 168s) coming to Chiltern seems like a good one to me!

 

[Billy A]

I believe the Voith 2 speed hydraulic as fitted to 14x 15x, 17x dmus only coasts in low ratio drive being direct in high. The ZF is reported to give around 10% fuel savings and be much quicker off the mark at the cost of more complexity. Perhaps Voith now make a more efficient comparable multi ratio box?
Pity the British SCG as fitted to heritage dmus and early Pacers is now defunct as there box was the most efficient of the lot. Sadly let down by insufficient development as engines got bigger.
K

Strictly speaking, the Voith box is a three speed unit with two gears - first speed involves a torque converter driving low gear while second speed uses a fluid coupling to drive the same gear with less slip. It drains all the couplings when power is cut so it'll coast in neutral - it doesn't coast in gear as such.
Yes, Voith make a conventional "mechanical" box - the Diwarail, a modified version of their four speed bus gearbox

The SCG box was a bit of a disaster from the reliability point of view..

 

[Bletchleyite]

That's what I always understood, they were ordered for superior start-stop performance.

And that's certainly what they have delivered on the Snow Hill lines - an EMU like service but using DMUs.

 

[superkev]

According to the document I have on the transmission as fitted to the 150s, both the torque convertor and fluid coupling can be emptied of oil as necessary when the power controller is closed and the unit freewheeling.

If Porterbrook's document on the 172s is correct, the 172s are quicker off the mark but take nearly two minutes longer to reach 100mph compared to a 168/170.

I'd take it with a pinch of salt. A 172 has a much more powerful engine (485hp) than a 170 (422hp) as well as a more efficient transmission, and is a few tons lighter so should be quicker under all conditions.
As for no coasting heritage dmu's has a freewheel in the carden shaft with the reversing mechanism in the final drive which worked well.
're Chiltern perhaps they just want all there dmu's to be the same rather than having 4 odd ones.
K

 

[Prestige15]

Bare in mind the 170's from WMT will be withdrawn from there so i know Chiltern is keeping an eye on them, but then again so is Cross ****ry and possibly Northern.

 

[sufian123]

Bare in mind the 170's from WMT will be withdrawn from there so i know Chiltern is keeping an eye on them, but then again so is Cross ****ry and possibly Northern.

Leasing companies taking them back 170s. They are homeless after 2022.

 

[Bletchleyite]

Leasing companies taking them back 170s. They are homeless after 2022.

They won't end up homeless, they'll go somewhere either for extra capacity or 15x replacement.

 

[sufian123]

They won't end up homeless, they'll go somewhere either for extra capacity or 15x replacement.

I meant time being they’ll be. Unless they find a new home.

 

[Prestige15]

I meant time being they’ll be. Unless they find a new home.

Chiltern, Cross Country and possibly Northern as they do seek capacity.

 

[sufian123]

Chiltern, Cross Country and possibly Northern as they do seek capacity.

Yeah it’ll be up to DFT.

 

[XCTurbostar]

Interesting reading through this thread. The current gear changes for the 6-Speed ZF Gearbox is at 15MPH, 28MPH, 42MPH, 58MPH and 76MPH.

 

[bnsf734]

Deleted

 

[hexagon789]

The idea upthread of the three-way swapping, losing the 172s in favour of some 170s (converted to 168s) coming to Chiltern seems like a good one to me!

Yes, I agree. A fleet standardisation would surely be a good thing.

And that's certainly what they have delivered on the Snow Hill lines - an EMU like service but using DMUs.

From Porterbrook:

"Accelerates to 25mph in 45 seconds; 50mph in 80 seconds; 75 mph in 150 seconds
and 100 mph in 362 seconds on flat level track, with low wind. These figures are
achieved with the vehicle in tare condition with all engines at operational temperature."

I'd take it with a pinch of salt. A 172 has a much more powerful engine (485hp) than a 170 (422hp) as well as a more efficient transmission, and is a few tons lighter so should be quicker under all conditions.

Wouldn't it also depend on how the transmission puts down that power though?

As for no coasting heritage dmu's has a freewheel in the carden shaft with the reversing mechanism in the final drive which worked well.

I know First Gen DMUs can coast no problem, but there are several posts across many threads on this forum which state that 172s are poor at coasting.

 

[superkev]

're 170 v 172 comparison looking at a recent Rail express magazines monthly 0 to 60 comparison (good read) 172 103 reached 60mph in just 83 seconds with a 170 taking 114 seconds.
For interest some others 185 (68s); 158 (98s); 180 (83s), 220 fastest non electric (53s ); 345 fastest emu (36s).
May be of Interest.
K

 

[hexagon789]

're 170 v 172 comparison looking at a recent Rail express magazines monthly 0 to 60 comparison (good read) 172 103 reached 60mph in just 83 seconds with a 170 taking 114 seconds.
For interest some others 185 (68s); 158 (98s); 180 (83s), 220 fastest non electric (53s ); 345 fastest emu (36s).
May be of Interest.
K

Always interesting to read, and where I get much if my acceleration times info from. It does show how superior 172s are off the mark compared to a 168/170 etc.