Mark 5, By Accurascale

[adb968008]

18 minutes ago, TomScrut said:

If they are back on single 185s then logically they'll be cheaper to run.

 

If 185s in pairs, not sure TBH, maybe depends on the lease terms.

 

In terms of fuel, two 185s have more power than a 68, distributed across smaller engines with a hydraulic powertrain so I would expect a 68 to use less fuel. One large engine should be more efficient that multiple smaller engines for any given power due to friction, and the electric powertrain allows the engine speed to be optimised for efficiency vs wheel speed, the 185s engines will broadly speaking have a relationship with the speed of the wheels. Also a 68 (85T) with 5 mk5s (215T) weighs less than a pair of 185s (326T).

 

So dispelling the whole notion that Multiple Units are more efficient than locomotive hauled trains….

[TomScrut]

29 minutes ago, adb968008 said:

So dispelling the whole notion that Multiple Units are more efficient than locomotive hauled trains….

 

Well the thing is, 185s are heavy and have one 750hp engine per car.

 

A 170 as a comparison weighs about 30 tonnes (20%) less and has 1000 less hp (45%) per set and so would expect to be way more efficient than either. A 3 car 170 weighs about the same as 3 mk5s.

 

But my original post was not a statement of fact but of expectation.

 

Locos will be more inefficient for passenger work simply because they need to be heavy, and any weight the carry to improve traction is inefficient compared to the distributed drive axles on a MU.

 

But we are probably comparing the best loco/coach combination with the worst unit in terms of what could be speculated about their efficiency. The 68 is light at 85 tonnes. 185s are probably metre for metre the heaviest DMUs in the country. When MUs first came about it was either a type 3/4 at 120+ tonnes or type 2/3 at 85 ish tonnes. So to get any sort of meaningful power they would be big heavy Co-Co locos. Now we can fit 3800hp in an 85 tonne Bo-Bo. But on the flipside a 5 car class 800 (not sure about 802, bigger fuel tanks though) weighs 243 tonnes and has more capacity than a 68/mk5a combo and possibly 2x185. 802s have 2820hp on diesel. So way lighter, carries more people but is less powerful than either a 6 car 185 or the 68. That sounds a lot more efficient!

Edited October 7, 2022 by TomScrut

[Roy Langridge]

Need to be very careful just looking at power etc. For some trips our 2.5l car is more fuel efficient than our 1.6l car, and way more powerful. 
 

Roy

[TomScrut]

45 minutes ago, Roy Langridge said:

Need to be very careful just looking at power etc. For some trips our 2.5l car is more fuel efficient than our 1.6l car, and way more powerful. 
 

Roy

 

Yes I agree, but if you had 2 1.25 litre engines at half the power of a 2.5 litre then the issue would be exacerbated which is what I am getting at with the 68 more likely being more efficient than the 6 engines in 2 185s.

[Steadfast]

Loco plus 5 coaches is the tipping point where it's more cost effective to run that rather than a DMU according to Ian Walmsley in Modern Railways, and he should know from his time at Porterbrook.

 

 

The comparison upthread using hp is a touch flawed, as with trains tractive effort is more important than horsepower. There will be losses in the system, such as the electrical loads, cooling, noise, friction that will sap some of the stated hp. Also a diesel electric will have different losses to a diesel hydraulic or a diesel mechanical.

 

Anyway, our toy trains are all powered by a small electric motor so work out the losses on that! 😉

 

Jo

Edited October 8, 2022 by Steadfast

[TomScrut]

7 hours ago, Steadfast said:

tractive effort is more important than horsepower

 

I don't agree with you there as the two are intrinsically linked (Power= Force x Velocity). To have high tractive effort at high speed, high power is required by definition. Obviously at lower speeds, assuming the drivetrain can provide enough torque then the mass on the driven axles is the limiting factor as adhesion is the problem, but to keep applying high tractive effort at speed you need power.

 

I think a good example of this is why a class 88 can go over Shap with 1183 tonnes on the back at 50mph whereas "A similarly loaded Class 66 will gasp over at 15mph" (interestingly also written by Ian Walmsley) despite the 66 having a greater tractive effort at lower speed due to the additional adhesion it has from it's weight, the 88s power allows it to keep applying the effort at a higher speed.

 

7 hours ago, Steadfast said:

There will be losses in the system, such as the electrical loads, cooling, noise, friction that will sap some of the stated hp. Also a diesel electric will have different losses to a diesel hydraulic or a diesel mechanical.

 

Yes that's what I meant. Diesel electric offers quite a lot of benefits here in my opinion as it means the engine isn't connected to the wheels. Probably why most high speed DMUs are diesel electric too.

 

7 hours ago, Steadfast said:

Loco plus 5 coaches is the tipping point where it's more cost effective to run that rather than a DMU according to Ian Walmsley in Modern Railways, and he should know from his time at Porterbrook.

 

That is interesting, and sorta on the lines of what we are saying here perhaps. I think the important thing here is "DMU" too, as EMUs it is a completely different matter as it is the engines and gearboxes (and multiples of) that will be the main cause of inefficiency. EMUs should be more efficient than electric loco and coaches because the distribution of drive axles doesn't need the overhead of the loco mass to get traction.

[No Decorum]

3 hours ago, TomScrut said:

 

I don't agree with you there as the two are intrinsically linked (Power= Force x Velocity). To have high tractive effort at high speed, high power is required by definition. Obviously at lower speeds, assuming the drivetrain can provide enough torque then the mass on the driven axles is the limiting factor as adhesion is the problem, but to keep applying high tractive effort at speed you need power.

 

I think a good example of this is why a class 88 can go over Shap with 1183 tonnes on the back at 50mph whereas "A similarly loaded Class 66 will gasp over at 15mph" (interestingly also written by Ian Walmsley) despite the 66 having a greater tractive effort at lower speed due to the additional adhesion it has from it's weight, the 88s power allows it to keep applying the effort at a higher speed.

 

 

Yes that's what I meant. Diesel electric offers quite a lot of benefits here in my opinion as it means the engine isn't connected to the wheels. Probably why most high speed DMUs are diesel electric too.

 

 

That is interesting, and sorta on the lines of what we are saying here perhaps. I think the important thing here is "DMU" too, as EMUs it is a completely different matter as it is the engines and gearboxes (and multiples of) that will be the main cause of inefficiency. EMUs should be more efficient than electric loco and coaches because the distribution of drive axles doesn't need the overhead of the loco mass to get traction.

Speaking of the 88s…

[Phil Mc]

On 08/10/2022 at 01:38, Steadfast said:

 

 

Anyway, our toy trains are all powered by a small electric motor so work out the losses on that! 😉

 

Jo

 

Those small electric motors have lost most of us on the forum an absolute fortune over the years........🙃🙃

 

Cheers,

Phil.

[JackB95]

Accurascale posted this video on their Facebook yesterday demonstrating how good the stay-alive capacitors are on their Mk5s. Wow. That's all I can say.

 

https://www.facebook.com/AccurascaleUK/videos/842615173534793

 

Nearly a whole minute before they're out! That's bloody incredible. Wonder how Hornby's APT is feeling after seeing that... 🤪

[TomScrut]

1 hour ago, JackB95 said:

Accurascale posted this video on their Facebook yesterday demonstrating how good the stay-alive capacitors are on their Mk5s. Wow. That's all I can say.

 

https://www.facebook.com/AccurascaleUK/videos/842615173534793

 

Nearly a whole minute before they're out! That's bloody incredible. Wonder how Hornby's APT is feeling after seeing that... 🤪

 

Surely these don't need to last more than 2 or 3 seconds, or am I misunderstanding their purpose?

[ERIC ALLTORQUE]

1 hour ago, JackB95 said:

Accurascale posted this video on their Facebook yesterday demonstrating how good the stay-alive capacitors are on their Mk5s. Wow. That's all I can say.

 

https://www.facebook.com/AccurascaleUK/videos/842615173534793

 

Nearly a whole minute before they're out! That's bloody incredible. Wonder how Hornby's APT is feeling after seeing that... 🤪

So run your layout up to the house power going out,the place will be light up until they get the power restored.

[Accurascale Fran]

7 minutes ago, TomScrut said:

 

Surely these don't need to last more than 2 or 3 seconds, or am I misunderstanding their purpose?

 

Hi Tom,

 

What's wrong with longer than 2 or 3 seconds?

 

Cheers!

 

Fran 

[JackB95]

1 minute ago, Accurascale Fran said:

What's wrong with longer than 2 or 3 seconds?

 

My girlf- wait, I best not 🤣

[Watto1990]

5 minutes ago, Accurascale Fran said:

 

Hi Tom,

 

What's wrong with longer than 2 or 3 seconds?

 

Cheers!

 

Fran 

If less is more, just think of how much more more will be!

Edited October 20, 2022 by Watto1990

[ERIC ALLTORQUE]

19 minutes ago, Accurascale Fran said:

 

Hi Tom,

 

What's wrong with longer than 2 or 3 seconds?

 

Cheers!

 

Fran 

Do you fancy scaling up and trying your hand at the EV........to be honest if something is better than what it is required to be then thats a plus, its been a good week,this and the DART mission exceed the given parameters,model rail and mankind win out.

[TomScrut]

31 minutes ago, Accurascale Fran said:

 

Hi Tom,

 

What's wrong with longer than 2 or 3 seconds?

 

Cheers!

 

Fran 

 

Well, in the case of the requirement only being 2 or 3 seconds, then I don't really like the idea of the capacitors being over specified. I wouldn't think I was doing my job properly if I went over specifying everything at work.

 

OTOH, having thought about it, I presume the real reason for this (although you could have said it) is for when people are on analogue DC and have trains stopping at stations.

[TomScrut]

41 minutes ago, JackB95 said:

 

My girlf- wait, I best not 🤣

 

You done already? Great, I can go to sleep now 😂

[Accurascale Fran]

1 hour ago, TomScrut said:

 

Well, in the case of the requirement only being 2 or 3 seconds, then I don't really like the idea of the capacitors being over specified. I wouldn't think I was doing my job properly if I went over specifying everything at work.

 

OTOH, having thought about it, I presume the real reason for this (although you could have said it) is for when people are on analogue DC and have trains stopping at stations.

 

Hi Tom,

 

Who said the requirement was for just 2 or 3 seconds? We've always wanted it far longer than that tbh to eliminate flickering etc. What we are delivering was in our design brief to the factory.

 

Cheers!

 

Fran 

[TomScrut]

4 minutes ago, Accurascale Fran said:

Who said the requirement was for just 2 or 3 seconds?

 

I asked the question, you said what's wrong with longer as though more is better without any real reason for doing so. You could have explained why it is longer than 2 or 3 seconds, that is why I asked!

[JackB95]

2 minutes ago, TomScrut said:

 

I asked the question, you said what's wrong with longer as though more is better without any real reason for doing so. You could have explained why it is longer than 2 or 3 seconds, that is why I asked!

Because they want it to be longer? They don't have to justify everything

[ERIC ALLTORQUE]

I would have though longer was better, other than tory prime minsters,thats a totally different ball game it seems.........

Edited October 20, 2022 by ERIC ALLTORQUE

[TomScrut]

38 minutes ago, JackB95 said:

Because they want it to be longer? They don't have to justify everything

They don't, but I asked a question, which didn't get answered, and then I am getting questioned on the statement I made based on the question that didn't get answered!

 

I was genuinely wondering why they needed to last a minute, and I think I did a better job of answering my own question than anyone else has who has replied to me.

 

In all honesty the whole thing stemmed from me not understanding your excitement at them lasting a minute when I hadn't thought of a good reason for them to at that moment in time.

 

3 minutes ago, ERIC ALLTORQUE said:

I would have though longer was better, 

 

That depends on the price we pay for that privilege, but at least these coaches are very reasonably priced regardless of the size of the capacitors so I aren't complaining in that respect.

Edited October 20, 2022 by TomScrut

[E100]

Provided the cost to go from a few seconds to nearly a minute is not noticeable then I don't mind. If it's an extra couple of quid added to each coach then I think it becomes an issue which with only limited knowledge I can't believe it does.

 

I assume we are also seeing the combination of ever more efficient LED's as well as smaller and more readily available super capacitors. I'm not expecting to see every hidden space filled with capacitors.

[Andy7]

Amazing job on the stay alive, just what I would want from a system.

 

On a side note, some of the stuff that gets asked of accurascale (the approachable manufacturer) is faintly ridiculous. Hope Fran et al have the resolve to keep laughing and replying.  

[Accurascale Fran]

2 hours ago, TomScrut said:

 

I asked the question, you said what's wrong with longer as though more is better without any real reason for doing so. You could have explained why it is longer than 2 or 3 seconds, that is why I asked!

 

Hi Tom,

 

My next sentence answers your question. I apologise profusely for the confusion.

 

Cheers!

 

Fran