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Sam*45110*SVR

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Having seen a few videos of real steam locos (ok Bulleid pacifics !) wheelspinning while setting off I was wondering if there was a way to replicate this in miniature. The main problem with this is that locos these days are quite powerful and most of us don't have the room for a train long enough to be on a large tender loco's haulage capacity. Simply turning the control knob quickly would just accelerate a shorter train violently. To prevent this something to temporarily increase resistance is required, my thought is a pad (like a track cleaning one) that can be pressed onto an unpowered axle (as tender wheel would seem the best option) to increase the resistance while more power applied. A function button could be used to trigger the application of the pad, the spinning of the wheels and a recording of the real thing wheelspinning. 

 

Controlling this though is a bit of a problem though as how much pressure is needed to keep the train moving at the same speed while the wheels are spinning. I had thought that the back EMF could provide the answer in one of two ways. 1 By reacting. If the pressure was applied the motor would compensate and spin the wheels but, I don't know much about it so I doubt this would happen. or 2 Providing data. From what I understand back EMF gives data to the decoder about how much work the motor is putting in and the decoder adjusts this to keep the train moving at the same speed. I thought maybe this data could then be used and manipulated by a formula before being fed to the mechanism that applies the pad.

 

A lot of work just to get a loco to wheelspin on a shortish train but I think it would be worth it !

 

Forgive me for any terrible misunderstandings!

 

Sam.

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Having seen a few videos of real steam locos (ok Bulleid pacifics !) wheelspinning while setting off I was wondering if there was a way to replicate this in miniature. The main problem with this is that locos these days are quite powerful and most of us don't have the room for a train long enough to be on a large tender loco's haulage capacity. Simply turning the control knob quickly would just accelerate a shorter train violently. To prevent this something to temporarily increase resistance is required, my thought is a pad (like a track cleaning one) that can be pressed onto an unpowered axle (as tender wheel would seem the best option) to increase the resistance while more power applied. A function button could be used to trigger the application of the pad, the spinning of the wheels and a recording of the real thing wheelspinning. 

 

Controlling this though is a bit of a problem though as how much pressure is needed to keep the train moving at the same speed while the wheels are spinning. I had thought that the back EMF could provide the answer in one of two ways. 1 By reacting. If the pressure was applied the motor would compensate and spin the wheels but, I don't know much about it so I doubt this would happen. or 2 Providing data. From what I understand back EMF gives data to the decoder about how much work the motor is putting in and the decoder adjusts this to keep the train moving at the same speed. I thought maybe this data could then be used and manipulated by a formula before being fed to the mechanism that applies the pad.

 

A lot of work just to get a loco to wheelspin on a shortish train but I think it would be worth it !

 

Forgive me for any terrible misunderstandings!

 

Sam.

 

Hi Sam,

 

Some constructive thoughts here, good luck with your experiments.

 

However, if your intention is to actually induce wheelspin on the track, there will be no need for a special 'wheelspin' recording. The exhaust beats are played in synch with actual wheel movements, so if they are turning more quickly, then the chuff sounds will speed up, too. Remember to back off the regulator quickly, we don't want any excessive wear or damaged cylinders! LOL. 

 

Paul

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For prototypical effect you would need at least ten coaches on. Unlikely on all but the largest layouts. What is vastly more difficult is getting the right amount of spin and the variables as the driver tries to get the wheels to grip by playing with the regulator. It was a canny driver who used a combination of over powering, sand and backing off to get a heavy train on the move without damaging the loco or the rails unduly. Quite often the original arriving loco at a terminus would help by applying a small amount of reverse power as the train moved off. Quite common at Kings Cross in steam days.

 

I have only heard it once on a preserved line and that was Canadian Pacific leaving Ropley towards Alton on a dampish morning some years back. PhilH was driving and we yard pundits felt that he was doing a grand job getting the laden four coaches away uphill on dew laden steel on the first train of the day.

 

Wheelspin is rarely heard these days and was not that common in steam days either as I recall except at known hotspots. It is or was fairly common in diesels as well but with no correlation between engine note and power delivery at the rail, no real need to duplicate in a sound chip although I would imagine that Paul Chetter's Multidrive concept would be ideal to tackle that scenario without the hassle of inducing wheelspin on the model.

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For prototypical effect you would need at least ten coaches on. Unlikely on all but the largest layouts. What is vastly more difficult is getting the right amount of spin and the variables as the driver tries to get the wheels to grip by playing with the regulator. It was a canny driver who used a combination of over powering, sand and backing off to get a heavy train on the move without damaging the loco or the rails unduly. Quite often the original arriving loco at a terminus would help by applying a small amount of reverse power as the train moved off. Quite common at Kings Cross in steam days.

 

You've hit the nail on the head david, I don't have room for longer trains where wheelspin is more likely so this will have to do! Just playing testing  ;) my sound Black 5 and you're right just speeding up then slowing down in quick succession is all that's needed sound wise. Need to find out about the more technical side of things now.

 

Sam.

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  • RMweb Gold

With a stiff regulator, greasy track or heavy handed driver you can get wheel spin with a light loco. What's harder to replicate is the partial slip then grip that's quite common. You'll probably be better off with a chip that allows you to switch off acceleration to allow a sudden start to induce slip yet still get the more powerful chuffs under load when load control is on with acceleration.

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  • 2 months later...

I have a large OO garden railway and have found that the Hornby MN,BB,WC will only give a prototypical slip with 19 coaches on. However if your train is made up of the pullman coaches with the LED table lamps then a much shorter train is poosible to get a wheel slip due to the pick ups on the axles of the coaches creating more of a drag.

It's odd that not too long ago people were saying that steam models had no haulage power, so manufacturers increased the weight of there steam models and now we complain that they won't slip.

I've also found that the Hornby 28xx/38xx will haul 55 Bachmann 16 ton mineral wagons if driven carefully but an increase in power too quickly will induce wheel slip.

Oddly enough the Bachmann WD will haul 60 16 ton mineral wagons with ease and some have said that the loco wouldn't 'pull the skin off a custard'. 

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With a stiff regulator, greasy track or heavy handed driver you can get wheel spin with a light loco.

 

I'm with Paul. Having spent a few months in a railway training school just outside Waterloo station, i.e. by the throat, I can say that Bulleid pacifics have a propensity to slip whatever the railhead conditions might appear to be. Of course this was 1966, and the remaining locos were not in the best of health in all cases, but it was virtually guaranteed that a slip would occur across the P&C.

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  • 4 months later...

  I'm with Paul. Having spent a few months in a railway training school just outside Waterloo station, i.e. by the throat, I can say that Bulleid pacifics have a propensity to slip whatever the railhead conditions might appear to be. Of course this was 1966, and the remaining locos were not in the best of health in all cases, but it was virtually guaranteed that a slip would occur across the P&C.

 

 -- But wasn't this propensity to slippage of Bulleid's pacifics caused, in part, by the flexing of the oil-bath and the leaking of its oil onto the track and elsewhere?

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Interesting that this thread has been revived now.

 

I've just sent my unrebuilt West Country sound project to Digitrains. This features wheelspin (sound) if you open the regulator too quickly in 'Heavy Train' mode at low speed, but not at other times or when in 'Light Engine' mode. This is not a sound controlled by an F key which plays 'on top off' the normal exhaust beats, and neither is it a sound which plays automatically every time the loco starts to move. It's all down to the way you operate your controls - as with the real loco.

 

The recordings were made aboard Wadebridge and also feature the 'irregular' exhaust frequency this loco exhibits at low speeds, gradually 'tightening' to a more regular beat as speed increases.

 

You may have seen and heard this already as it has been loaded in the Hornby Magazine exhibition West Country locos since June.

 

Kind regards,

 

Paul

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  • 4 weeks later...
  • 3 weeks later...

Here's my attempt. OK, the wheels don't actually slip, but the sound plays IF you open the regulator too quickly. It works from the throttle (regulator)action and does not slip when driven gently, so there's a challenge for all you would-be engine drivers! Ha ha.

 

Those who know what to listen for will be able to hear 5 different cut-off/regulator combinations which adds interest to the exhaust beat sounds.

 

Paul

 

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