Jump to content

Consisting and Double Heading ref speed matching.


Recommended Posts

Hi Guys,

I probably know this question has been asked before....but a quick answer would be appreciated.

 

Never having run double headers or consists previously......my understanding is that it is ALWAYS necessary to ensure locos are speed and acceleration and deceleration matched before doing this procedure, otherwise the motors are fighting each other to a greater or lesser degree.

 

A friend of mine said he had been told that just by merely consisting two locos using the DCC method, that this procedure does all the matching for you.?

 

That has never been my understanding...it would be wonderful if it did though.

 

Could someone confirm this for me please one way or the other.

 

Thanks...................Bob.

Link to post
Share on other sites

Hi Bob,

 

I'm afraid not, consisting will only send your throttle commands to each loco in the consist.

 

It's possible to consist loco's that are running in the wrong direction and that have vastly different performance from each other. You have to balance the loco's to get the best results.

 

Cheers, Mark.

Edited by Vonzack
Link to post
Share on other sites

Never having run double headers or consists previously......my understanding is that it is ALWAYS necessary to ensure locos are speed and acceleration and deceleration matched before doing this procedure, otherwise the motors are fighting each other to a greater or lesser degree.

 

Basically correct.

There are ways to reduce the amount of "fighting" without getting the speeds totally matched; reducing (or turning off) the BEMF influence is the usual method. By reducing the BEMF influence, you stop the decoder trying to compensate for the loco going at a different speed to the the speed the decoder expects the motor to be running at.

 

But the usual negative effect of reducing BEMF is to make slow speed control much worse. Thus, quite a lot of decoder makers allow you to run with lots of BEMF influence until a modest speed is reached (user settable CV for this value), then reduce BEMF influence at higher speeds.

 

 

A friend of mine said he had been told that just by merely consisting two locos using the DCC method, that this procedure does all the matching for you.?

 

Your friend is either wrong, or you have misunderstood what was said.

A "consist" on any system is simply a mechanism to control multiple locos from one throttle. You send the same speed instructions (eg. run at speed 15) to all locos in the consist, nothing else happens.

 

 

- Nigel

Link to post
Share on other sites

Could the friend be referring to use within a computer program such as TrainController?

 

In this case (unless I have misunderstood the manual!) the locos do not need to be speed matched as long as a full speed profiling of each loco has been carried out beforehand. TrainController does the matching.

 

Keith

Link to post
Share on other sites

The only way I have managed to double head without the locos fighting each other is. Turn of BEMF. match a near as possible the CVs. Once i have done that, I time each loco over a distance and try by changing CV 5 on one to match the others time. Even so I am not covinced that they are still not matched. trouble is, it looks all to easy from the instruction book/ manual, Nothing ever said about speed mismatch.

Link to post
Share on other sites

So in other words DCC isn't all it's cracked out to be :scratchhead: .

 

Er, you're incorrect.

 

DCC will do whatever you want with regard to this subject, you just need to tell it what to do!

What would the DC method of speed-matching two differeng loco's be - re-gearing? adding/removing resistors? which is easier? ;)

 

FWIW - from the point of view of this US modeller (who runs multiple loco's together all the time) - whilst I agree it's better if two loco's are exactly matched, 'somewhere close' is normally adequate to get them to work together - they *don't* have to be perfect, resistances in the drives and drag of the train affect things too, so a loco that starts slightly before another just overcomes the resistances in the drive of the second loco slighty before it would naturally, to an extent the two balance out as long as they are somewhere close meaning that they *don't* fight each other - similarly if you have a heavy train coupled then even with exactly matched loco's the first will be 'helping' the second as the second has the train weight on the coupler holding it back.

Edited by Glorious NSE
  • Like 1
Link to post
Share on other sites

Hi Guys,

Many thanks for taking the time and trouble to respond to my question. Your replies confirmed exactly what my thoughts were....but I wasn't confident enough on the subject to give my friend an accurate reply.

 

My friends pal is a US modeller....and he says he just takes his models to his club, and drops them into consists with other folks models. They obviously work reasonably well, possibly because they are all similarly set up in the first place.

 

Where I would have a problem is towing my Electric AL5 around a depot, with no catenary, with a diesel shunter, as a consist. The two models would be wildly out of sync.

 

I am absolutely clear on the subject now, and will pass the information to my pal.

 

Regards.......................Bob

Link to post
Share on other sites

I would suggest testing them by consisting them without coupling them up, then run them up and down a few times to see if they are somewhere close or not...if not, you'll need to tweak one to perform nearer the other.

 

Yes, most US makes will be 'somewhere close' straight out of the box, although there are ones that don't fall into that. I'd expect 'like' mechs to be essentially the same (say a Bachmann 24 with a 25), and i'd expect all modern Bachmann and Hornby machines to be probably similar enough to get away with, but something like an 08 may have been geared to have a vastly lower top speed.

 

I'd be wary of Heljan too just because they seem to have some products with some 'interesting' running characteristics.

 

I can see you'd also not want the AL5 to move before the 08 either, or that would look silly! :)

 

My suggestion would be not to consist them, but to pop the worm gears out of the AL5 and make it a 'dummy'.

Link to post
Share on other sites

Where I would have a problem is towing my Electric AL5 around a depot, with no catenary, with a diesel shunter, as a consist. The two models would be wildly out of sync.

 

You might be able to do this if the AL5 has a decoder with a "shunt" speed mode which halves the speed range. Then consist using Command Station assisted consist would certainly work, the shunter at "full" speed, and the AL5 at "half" speed. Not sure how different decoders would behave on half-speed and decoder assisted consists (CV19). There's still be some speed matching to sort it out, but the ranges might at least overlap.

 

Another approach would be to setup the AL5's speed range with CV2, CV5 and CV6. When performing yard shunting, drop CV5 with ops-mode changes to a low (but known) value, thus massively dropping its speed range, and then consist with the shunter. When finished, reset CV5 back to its old value. This might need a few paper notes of appropriate values.

 

 

- Nigel

Link to post
Share on other sites

I speed and acceleration match my locos into groups (slow/medium/express/A4) and arrange for bottom quarter speed to match reasonably well on all, as the final part of the decoder set up. As a low tech guy, this is done on a half mile test circuit with a stopwatch.

 

Being in the GraNd tradition, double heading is not to be thought of generally, but groups of locos can run together on and off shed routinely for movement economy. The speed match means that when I am modelling a diesel (15, 21, 23, 105) or L1 failure, it is no problem to hook something else on and run together.

Link to post
Share on other sites

I would suggest testing them by consisting them without coupling them up, then run them up and down a few times to see if they are somewhere close or not...if not, you'll need to tweak one to perform nearer the other.

 

Yes, most US makes will be 'somewhere close' straight out of the box, although there are ones that don't fall into that. I'd expect 'like' mechs to be essentially the same (say a Bachmann 24 with a 25), and i'd expect all modern Bachmann and Hornby machines to be probably similar enough to get away with, but something like an 08 may have been geared to have a vastly lower top speed.

 

I'd be wary of Heljan too just because they seem to have some products with some 'interesting' running characteristics.

 

I can see you'd also not want the AL5 to move before the 08 either, or that would look silly! :)

 

My suggestion would be not to consist them, but to pop the worm gears out of the AL5 and make it a 'dummy'.

 

I already did the worm gear removal on one of my paired class 20's(always paired)...best solution at the time, rather than buy another sound decoder.

 

With my AL5, I intend to use it on passengers, but being dragged, by class 40's, steamers etc, i.e early 60's era. I dont have catenerary, and dont intend to have it either. So it will be shunted around by an 08 in the depot.......gear removal is the best option here, and also the most realistic option too.

 

To adjust CV's etc each time it gets towed by another loco is not something I want to do.....it will always be dragged.

 

Thanks.................Bob

Link to post
Share on other sites

I speed and acceleration match my locos into groups (slow/medium/express/A4) and arrange for bottom quarter speed to match reasonably well on all, as the final part of the decoder set up. As a low tech guy, this is done on a half mile test circuit with a stopwatch.

 

Being in the GraNd tradition, double heading is not to be thought of generally, but groups of locos can run together on and off shed routinely for movement economy. The speed match means that when I am modelling a diesel (15, 21, 23, 105) or L1 failure, it is no problem to hook something else on and run together.

 

I assume you talking about a scale half mile..!!!!!

Its a good idea to group the locos, every one of mine is completely individually set up to my liking, but if I were to want to double head regularly, then this is a good option.

Cheers....Bob

Link to post
Share on other sites

Er, you're incorrect.

 

DCC will do whatever you want with regard to this subject, you just need to tell it what to do!

What would the DC method of speed-matching two differeng loco's be - re-gearing? adding/removing resistors? which is easier? ;)

 

FWIW - from the point of view of this US modeller (who runs multiple loco's together all the time) - whilst I agree it's better if two loco's are exactly matched, 'somewhere close' is normally adequate to get them to work together - they *don't* have to be perfect, resistances in the drives and drag of the train affect things too, so a loco that starts slightly before another just overcomes the resistances in the drive of the second loco slighty before it would naturally, to an extent the two balance out as long as they are somewhere close meaning that they *don't* fight each other - similarly if you have a heavy train coupled then even with exactly matched loco's the first will be 'helping' the second as the second has the train weight on the coupler holding it back.

 

Hi Martyn,

 

Thank you for your info I do intend to go DCC with my next 7mm layout which at the moment is still at the planning stage, my remark was a bit tongue in cheek as at present I can just about tell the difference between a fuse and a resistor.

 

ATB,

 

Martyn.

  • Like 1
Link to post
Share on other sites

I had this problem with a pair of Bachmann class 20's which were forever fighting each other, in the end I passed them on to a friend at my club who has a rolling road with speedometer on it. He spent a bit of time ajusting various CV's until at all speed settings they were running at the same speed. I still have a very small difference at odd speeds but on the whole they work really well.

silverlink

Link to post
Share on other sites
  • RMweb Gold

Could the friend be referring to use within a computer program such as TrainController?

 

In this case (unless I have misunderstood the manual!) the locos do not need to be speed matched as long as a full speed profiling of each loco has been carried out beforehand. TrainController does the matching.

 

Keith

 

You are indeed correct. With Traincontroller you drive a train at a speed in MPH and not at a DCC speed step. If the train has more than one loco, then TC will drive each one separately. This can - and usually does - mean each engine is running on a different speed step in order to run each engine at the same speed. All that's required is that each loco has been fully profiled via TC's calibration process, the profile from that process is nice and smooth, and Back EMF is working accurately. As you've found with some TCS decoders, this is not always the case!

Link to post
Share on other sites

Guys,

Thanks so much for your help so far.

 

Tell me, can I just wire through to the other "dead" class 20 loco using the sound decoder in the first class 20 in order to power both locos.?

 

Or am I likely to overload the decoder.?? These are a permanently couple pair of locos.

 

This would be taking only the red and black feed wires through to the other loco motor.

 

Bob

Link to post
Share on other sites

Bob,

I don't think it is just down to the decoder, motors vary wildly & as such can have different resistance in the motors. Mine were idendical and fitted with same sound decoder and yet one always ran away faster than the other at the same speed steps. I understand they have very different settings of the decoders to get them running at simular speeds.

Ian

Link to post
Share on other sites

 

Tell me, can I just wire through to the other "dead" class 20 loco using the sound decoder in the first class 20 in order to power both locos.?

 

Or am I likely to overload the decoder.?? These are a permanently couple pair of locos.

 

Simpler to disconnect the drive in the second loco and have it as a push-along. Its only an issue if you need massive power to haul really heavy trains.

Either remove a spur gear in the bogies so they roll freely, or remove worms. If you want really good sound, cut out much of the chassis in the second loco and install a really high quality speaker enclosure, with the biggest speaker that can fit, and wire that to the sound decoder.

 

The problem with a decoder controlling two motors is sensing the BEMF from the loco. With two motors, they will each give a component of BEMF back to the decoder. Now, it may all work out, if both motors perform similarly and the load on the motors is always the same in each loco. But it may lead to less good control as the decoder can't get the running of two motors to behave correctly.

 

 

There are a few sound suppliers offering "twin" class 20 projects, which have two loco motors running slightly out of synch, just like a real pair. Also, it may be worth asking a dealer whether ESU offer a "trade-in" price on a V3.5 for a V4 decoder, which would give a more powerful amplifier (better sound quality) and a wider range of speakers.

 

 

- Nigel

Link to post
Share on other sites

Hi Bob

 

Been on this consisting road for a while now ( see my post on this subject )

I have two DRS Class 37's which I wanted to consist,but one of them was sound fitted

The non sound loco ran faster, not a lot,but enough

I contacted Olivia,s of Sheffield as I wanted advice on how to alter the speed steps.

They informed me it was impossible to marry the speed of the two loco,s as the sound example will always move slower than the non fitted one,even with speed stepping.

I have bitten the bullet and had the worm gear removed from the non sound 37, and I have now reached my goal of prototypical double heading of the two loco,s

I didn,t really want to do this,but now I have I,m pleased with the results

It is no great deal to have the gear replaced should I want to revert back

The conclusion for me?

Remove the worm gear and run the loco,s that way,the rest just isn't worth the hassle !

Link to post
Share on other sites

Hi Superam

Yes, I remember talking to you on the 37 consisting issue......and for about 4 years now, I have been running one of my 20's without the worm gears. But I have gradients and heavyish trains, and sometimes they struggled for adhesion. Having replaced my worm gears this week, and wired the motor through from the decoder in the other loco, they both work perfectly together, in complete harmony. If I didnt have the gradients, I probably would have left one without the worm gears and left it as a free wheeler.

I actually quite enjoyed the challenge of wiring it all together, then putting a screw coupling on to join them together. The joining wires are very inobtrusive.

post-21-0-84534600-1344545005_thumb.jpg

Edited by 250BOB
Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
×
×
  • Create New...

Important Information

We have placed cookies on your device to help make this website better. You can adjust your cookie settings, otherwise we'll assume you're okay to continue.