Double heading

[dolydd]

I have always taken as read that there should only be one engine running off any DC controller at any one time but: is there anything wrong coupling up two locos, provided that their motor speeds etc are compatible? And if that is OK, is there anything electrically unwise in running two trains round a circle of track as a true tail chaser, provided that one doesn't crash into the rear of the other of course?

[Jenny Emily]

Double heading (and even triple heading) works fine on DC. Eventually adding more locomotives will trip out the controller, but with modern locomotives that actually takes more than I've tried. In the following video there are three Hornby Pecketts running quite happily in the same train together on DC:

 

[phil-b259]

I have always taken as read that there should only be one engine running off any DC controller at any one time but: is there anything wrong coupling up two locos, provided that their motor speeds etc are compatible? And if that is OK, is there anything electrically unwise in running two trains round a circle of track as a true tail chaser, provided that one doesn't crash into the rear of the other of course?

To be honest, I don't see an issue running double headed on DC even if the motors are not matched as unless the slower loco is fitted with traction tyres, the slower locos wheels will be able to slip and slide along the rail tops during their rotation.

 

Alternatively if the faster loco is the lighter one of the two and is being 'held back' by the slower, heavier one - then providing it doesn't have traction tyres it can wheel spin a bit as it goes along thanks to the metal - metal interface.

 

Naturally there will be an increase in drag and wear in doing the above, but in the overall scheme of things I wouldn't have thought it to be a significant issue for most modellers.

[davetheroad]

No problem with double heading on DC. I researched online a couple of years ago and the general consensus was its OK as long as one loco is not constantly skidding or wheel slipping. I aim for loco speed matching of better than 10% difference which is what DCCWiki suggests. No need to have that amazing sub 1% match that does not survive the move from test track to real layout anyway.

 

I speed matched a couple of Class 3f 0-6-0's and coupled them light engine with the slightly fastest one in front. As expected on my roundy roundy the coupling was under tension but I was surprised to find at 2 points on the circuit totalling about 4 feet the couplings were under compression. The slow loco was faster than the fast one!.

[Il Grifone]

The only problems are the capacity of the power supply to supply enough current and the possibility of short circuits through the couplings if the loco chassis are live (insulated couplings solve this). I have always found that the locomotives with sort out their differences as regards speed, but would agree that they are better matched. Two separate trains will work just as well, but there is a danger of collision as one is always faster than the other.

[Pete the Elaner]

On a standard DC controller, 2 locos will run more slowly than 1. This is because a power supply uses some of the applied voltage across itself.

By adding a 2nd loco, you will change the way the resistances & therefore the voltages are split, so more of the total voltage will be used across the supply itself & therefore less will be available for the locos.

This is also why you may have 14v across the rails at full power when there is no loco & only 11v with a loco running...with 2, this may drop down to 9v.

Feedback works differently.

[Londontram]

I've always run double headers with no problems even using screw and three link couplings just making sure that if one loco was a tad faster than the other then it went in front to keep the couplings tight to cut down the risk of buffer lock but if your using tension lock couplings then this is not so important. I did try to match them as close as possible so the was no cases of an 0-4-0 pugs double heading with a Duchesses but two of the same class works well like two LMS 4F for example but you can mix and match a bit if you want.

 

On an old LMS themed layout I had as well as things like 3F and 4F double headers I ran a Wrenn 8F and an Airfix 4F together quite happily and despite being different types of model worked surprisingly well

 

Go for it and have fun

[Andy Hayter]

I built an 0-6-6-0 Mallet tank locomotive for the OH,  Both chassis are motorised using the Roco BR50 in N gauge as the donor. [To all intents and purposes this is double heading under one body.]  

It did take 4 chassis however to find 2 that were matched in terms of speed.  This from ostensibly identical models.  The difference in speed between the fastest and slowest at a given setting was enormous - and it has to be said that used alone each chassis worked smoothly and you would not fault any of them as a "bad runner".

Edited August 11, 2017 by Andy Hayter

[Fat Controller]

I built an 0-6-6-0 Mallet tank locomotive for the OH,  Both chassis are motorised using the Roco BR50 in N gauge as the donor. [To all intents and purposes this is double heading under one body.]  

It did take 4 chassis however to find 2 that were matched in terms of speed.  This from ostensibly identical models.  The difference in speed between the fastest and slowest at a given setting was enormous - and it has to be said that used alone each chassis worked smoothly and you would not fault any of them as a "bad runner".

I have had similar problems when 'double-motoring' diesels. Much easier now that central-motor chassis have become commonplace.

[DCB]

I habitually double head and bank trains.   The trick is getting both locos to run on the same voltage, or accurately pairing similar locos up.

 

I use Morley, On Track, Playcraft and H&M variable Transformers.   All these control track voltage, and will provide a progressively higher maximum voltage as the knob is turned even off load, and I can double head a Hornby 42XX with a Triang Hall despite a 3 or 4 to 1 disparity in maximum speeds. I have a YouTube clip of them on a 24 wagon freight.

This also means my Triang  chassis GWR Prairie tanks can bank most locos up the 1 in 30 without slipping.

 

With resistance controllers, Duette, etc which show 14 to 21 volts off load on minimum speed you have to accurately match the locos. I haven''t used a feedback controller for about 20 years, but I suspect they are totally confused by two sets of back EMF and double heading may well be completely impossible with them, unless the locos are essentially identical.

 

On my floor layout with Triang super 4 track which has graced holiday houses and patios from Devon to Scotland, I find dodgy fishplates cause power drop problems so I simply put two resistance controllers on one track, at opposite sides of the layout.  As long as they are turned the same way its fine.

 

Radio Control is the answer for  banking, and double heading, two operators/ drivers for one train real teamwork, just like the real thing.

 

Not sure if you can control two locos on separate controllers on the same track with DCC.

Edited August 11, 2017 by DavidCBroad

[kevinlms]

To be honest, I don't see an issue running double headed on DC even if the motors are not matched as unless the slower loco is fitted with traction tyres, the slower locos wheels will be able to slip and slide along the rail tops during their rotation.

 

Alternatively if the faster loco is the lighter one of the two and is being 'held back' by the slower, heavier one - then providing it doesn't have traction tyres it can wheel spin a bit as it goes along thanks to the metal - metal interface.

 

Naturally there will be an increase in drag and wear in doing the above, but in the overall scheme of things I wouldn't have thought it to be a significant issue for most modellers.

But perhaps having the fastest loco on the front, isn't what is required. For example a common combination on the LMS, was for a 2P 4-4-0 to double-head, something like a Jubilee as the train loco. Putting the Jubilee on front would be wrong, unless  assisting a failure.

[kevinlms]

I've always run double headers with no problems even using screw and three link couplings just making sure that if one loco was a tad faster than the other then it went in front to keep the couplings tight to cut down the risk of buffer lock but if your using tension lock couplings then this is not so important. I did try to match them as close as possible so the was no cases of an 0-4-0 pugs double heading with a Duchesses but two of the same class works well like two LMS 4F for example but you can mix and match a bit if you want.

 

On an old LMS themed layout I had as well as things like 3F and 4F double headers I ran a Wrenn 8F and an Airfix 4F together quite happily and despite being different types of model worked surprisingly well

 

Go for it and have fun

But on the Somerset & Dorset, there is a famous photo of a Jinty, assisting a Bulleid Pacific on the 'Pines Express', taken by a certain Ivo Peters IIRC! Probably a last minute replacement for a 2P.

 

Yes, photo is by Ivo Peters and appears in Fowler Locomotives, page 57. Loco is 47496 24 December 1959.

 

Prototype for everything department.

[Chris M]

I have posted this clip before but it does show double headed steamers running quite happily together. In fact this whole layout is run from just two basic Gaugemaster controllers. One hand held and one panel mounted. All the trains running in the same direction are just powered by one controller.

[Chris M]

I also double head out in the garden using dc. Here speed matching isn't important because the load is so heavy that both locos will be pulling hard. In this case the issue is having sufficient amps and a controller that can cope with the amps being used. These two will be pulling circa 6 amps. This video doesn't become relevant until about 50 seconds through.

[Titan]

To be honest, I don't see an issue running double headed on DC even if the motors are not matched as unless the slower loco is fitted with traction tyres, the slower locos wheels will be able to slip and slide along the rail tops during their rotation.

 

Alternatively if the faster loco is the lighter one of the two and is being 'held back' by the slower, heavier one - then providing it doesn't have traction tyres it can wheel spin a bit as it goes along thanks to the metal - metal interface.

 

Naturally there will be an increase in drag and wear in doing the above, but in the overall scheme of things I wouldn't have thought it to be a significant issue for most modellers.

 

I generally find that even with mismatched motors, you will not get wheel slip of either loco unless they are very mismatched. What happens is the 'faster' loco just takes a greater proportion of the train weight. The motors have to be pretty dramatically mismatched before there is any kind of issue, i.e. the faster loco is capable of hauling itself and the entire train weight faster than the other one runs light engine. Even then a little extra push/pull (depending on if the faster loco is leading or not) will just push/pull the slower loco a little bit faster than it runs light engine before wheel slip occurs.

[davetheroad]

I habitually double head and bank trains.   The trick is getting both locos to run on the same voltage, or accurately pairing similar locos up.

 

I use Morley, On Track, Playcraft and H&M variable Transformers.   All these control track voltage, and will provide a progressively higher maximum voltage as the knob is turned even off load, and I can double head a Hornby 42XX with a Triang Hall despite a 3 or 4 to 1 disparity in maximum speeds. I have a YouTube clip of them on a 24 wagon freight.

This also means my Triang  chassis GWR Prairie tanks can bank most locos up the 1 in 30 without slipping.

 

With resistance controllers, Duette, etc which show 14 to 21 volts off load on minimum speed you have to accurately match the locos. I haven''t used a feedback controller for about 20 years, but I suspect they are totally confused by two sets of back EMF and double heading may well be completely impossible with them, unless the locos are essentially identical.

 

On my floor layout with Triang super 4 track which has graced holiday houses and patios from Devon to Scotland, I find dodgy fishplates cause power drop problems so I simply put two resistance controllers on one track, at opposite sides of the layout.  As long as they are turned the same way its fine.

 

Radio Control is the answer for  banking, and double heading, two operators/ drivers for one train real teamwork, just like the real thing.

 

Not sure if you can control two locos on separate controllers on the same track with DCC.

I have been thinking about the possibilities of double heading of locos that have different transmitters but only having one operator. It should be easy for banking if the banker has an old style broad tension lock without the hook. Set the lead loco going and bring the banker up to the rear of the train. you can then take up some of the load and the lead locos speed should increase as its load lessens. At the top of the incline drop your banker back. actually you can do this with one transmitter.

 

For piloting/double heading I am thinking of trying replacement speed knobs (potentiometers) with multiple indents. speed match the locos and when you want to double head just ensure both transmitters are set to the same indent!. Four locos on each of 2 transmitters gives you 16 possible double head pairs!.

Edited August 11, 2017 by davetheroad

[Fat Controller]

But on the Somerset & Dorset, there is a famous photo of a Jinty, assisting a Bulleid Pacific on the 'Pines Express', taken by a certain Ivo Peters IIRC! Probably a last minute replacement for a 2P.

 

Yes, photo is by Ivo Peters and appears in Fowler Locomotives, page 57. Loco is 47496 24 December 1959.

 

Prototype for everything department.

Express trains to West Wales were regularly piloted by a pannier tank from Swansea High Street as far as Cockett station.

[knitpick]

Generally having 2 powered locos running double headed under the same DC controller doesn't cause problems; I have done it many times.  However, the old Hornby Silver Seal locos weirdly had loco and tender of opposite polarity.  So if you tried to double head (say) 2 9Fs or 2 Back Fives, then you got a short through the old Tri-Ang style metal tension lock couplings.  Also once, I got some very odd jerky fast/slow running once - I think with a Lima plus old Hornby steam loco combo.  A case of the two motors interfering with each other. 

 

Of course with a decent length train, as a general rule, the front loco will pull the second loco which in turn will pull the train.  So there shouldn't be any wheel slippage - unless the train is too heavy?

 

Then again, I do also run HSTs with a power car at each end rather than power plus dummy. 

[orford]

The biggest problem is actually coupling two or three locos together 'on-scene' with DC unless you have several loco length switched isolating tracks in the appropriate place so that you can park one loco on the front of a train whilst running the other up to it, before moving off ........and it probably works best if you do this 'off-scene.

 

This is just one of the things which is so much easier to do with DCC, although I fully appreciate that DCC is not for everyone.  Personally I would absolutely hate to go back to the 'dark ages' of DC now.

[Pete the Elaner]

 

Not sure if you can control two locos on separate controllers on the same track with DCC.

Yes you can.

You can only have 1 command station running the layout but it can be receiving instructions from multiple controllers (throttles in DCC terms), each driving a different loco.

[DCB]

The biggest problem is actually coupling two or three locos together 'on-scene' with DC unless you have several loco length switched isolating tracks in the appropriate place so that you can park one loco on the front of a train whilst running the other up to it, before moving off ........and it probably works best if you do this 'off-scene.

 

This is just one of the things which is so much easier to do with DCC, although I fully appreciate that DCC is not for everyone.  Personally I would absolutely hate to go back to the 'dark ages' of DC now.

I have a one yard long isolated section in the platform just over 1 loco length from the platform end so train loco can be isolated and the pilot can back down and couple up, the up end of the platform is one section and the down end a different one so a banker can come up behind.

For  trains taking a pilot from the hidden sidings or terminus the Pilot and Train engine couple up in the loco sidings where there are lots of isolated sections before backing on to their train.   This needs designing in to a layout from the outset, but with 1 in 30 gradients and 7 coach trains pilots and bankers are a necessity.

Uncoupling is usually in the loco depots after the stock has been pulled off.

Most railways put the Train engine on the front including the GWR.  But between Newton Abbott and Plymouth different rules applied and effectively any loco with a bogie could act as pilot despite the fact that Bulldogs, Dukedogs and Manors could not release the brakes effectively on trains of more than 10 coaches. Normally 5'8" wheel locos were used as pilots here but from Stratford on Avon 2251s were often coupled inside Counties etc for the leg to Birmingham.

The SDJR often double headed 7ft wheel 2Ps with 4'7" 2-8-0s and 5'2" 4Fs, the Midland put 2Ps in front of Jubilees following accelerations on the line out of St Pancras, don't know why, it would probably have beet better to leave the 2P in the shed.

 

Banking needs more thought, Tension lock couplings tend to ride over each other when pushing, so I use Peco type (Kadees would be better) and I make a coupling mounting bar which is guided by a pin engaging in the bogie or pony truck but free to float up and down between so the coupling does not lift and derail the leading wheels. I regularly push 20 wagons over a code 100 long diamond and up a 1 in 30 and around a short 3rd radius curve.

Edited August 12, 2017 by DavidCBroad

[davetheroad]

As I use radio control with battery power any loco can be backed onto another anywhere. Uncoupling is a different problem of course. 

 

Why a 2P with a Jubilee? My prototype inspiration is Cumbria so I imagine a pilot would be needed because due to diversion between the WCML and S&C or vice versa the main loco crew do not know the road well enough so a pilot is attached. Is it plausible?

[timbowilts]

Anything is plausible, after all it's your railway

 

In practice if the crew haven't signed for the road a driver who had signed for the road would accompany the regular crew as a "conductor" - they wouldn't attach a pilot engine, unless they needed to get one wherever the diversion was going. Doing that would save a separate traffic movement having to take place.

 

Tim T

 

(43 years on the Railway, finishing at christmas - yippee)

[DCB]

As I use radio control with battery power any loco can be backed onto another anywhere. Uncoupling is a different problem of course. 

 

Why a 2P with a Jubilee? My prototype inspiration is Cumbria so I imagine a pilot would be needed because due to diversion between the WCML and S&C or vice versa the main loco crew do not know the road well enough so a pilot is attached. Is it plausible?

The Midland main line expresses out of St Pancras were accelerated in the mid 50s and many were too heavy for 6P (Jubilee) locos and Black 5s and really required a 7P, Scot, rebuilt Patriot or Britannia so the Jubilees and Black 5s were piloted, and rather than waste a useful locomotive they dragged some 2Ps off branch line duties and probably the scrap line and stuck them on the front of expresses on the basis that they could probably just about manage to pull the 30 ton or so overload...

 

I don't know much about Cumbria, always sounds like Black 5 territory to me, with the occasional Mickey Mouse after the last LNWR Cauliflowers finally fell apart.  I guess the coast line is fairly level buy the line across to Penrith was anything but with lots of pics of Mickey Mouses (Ivatt 2mt's) double heading on as few as 5 coaches. I guess f they sent the Mid Day Scot round the coast it would only have had a pair of Black 5s, I don't think Stanier Pacifics were allowed in BR Steam days.

 

As Timbowilts says Pilotmen rather than Pilot Locos were provided for diversions where the Driver, and sometimes the guard, did not know, or did not sign for the road, lots of anecdotes in various enginemen's reminiscences, Drivers getting upset with Pilotman's handling of "His" loco etc.

[Londontram]

I did run a couple of old but detailed 3F Jinty's as a pair of bankers and I removed the motor from the second one but cross wired them so the combination picked up from both chassis. It was quite impressive to see three locos on the one train with something like a 4F pulling a well loaded coal train and the bankers pushing from the back. Matching locos was important as I had three link couplings so in this case found it better to keep the couplings "stretched" slightly so as not to get buffer lock but not to much that the bankers would drag the wagons off on curves, this was done by trial and error adding or removing wagons until it looked and performed just right.