Wheelslip

2282 Views 6 Replies 5 Participants Last post by John, Oct 3, 2007

5696Arethusa

Discussion Starter · Sep 25, 2007

I was running one of my A1s this afternoon and as I'm still on DC I'm able to control the power reaching the loco and slip the wheels when starting a heavy train. This got me thinking, with all the things you program DCC to do I've never seen or heard of this being done on DCC, is it possible? If so can you program the sound to match, there's nothing that says steam quite as much as the battle between touque and friction when touque gets the upper hand.

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Brian Considine

· #2 · Sep 26, 2007

QUOTE (5696Arethusa @ 25 Sep 2007, 21:53) <{POST_SNAPBACK}>I was running one of my A1s this afternoon and as I'm still on DC I'm able to control the power reaching the loco and slip the wheels when starting a heavy train. This got me thinking, with all the things you program DCC to do I've never seen or heard of this being done on DCC, is it possible? If so can you program the sound to match, there's nothing that says steam quite as much as the battle between touque and friction when touque gets the upper hand.

You could try setting CV3 (acceleration) to a custom speed curve if the decoder you are using supports it.

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34C

· #3 · Oct 1, 2007 (Edited by Moderator)

It is very easy to do manually with DCC, with a heavy train on, exactly as you would with a DC controller. On the Lenz system I would get the loco just started on speed step one or two in 128 speed step mode with function 4 (direct drive) activated, then push the 'big speed up button' once or more, then when you have had enough wheelslip push the 'big speed down button' as required. Similar routines should deliver the same sort of result on other systems. If the sound decoder is properly integrated to rotational speed of the wheels, the 'eruption' effect should be obtained. (Pause for happy reminiscence of A1's and other ECML pacifics 'blasting off' on a wet and greasy rail at the Cross and elsewhere - aaahhhhhh.)

Automating this comes up against the difficulty that decoders work from a single speed curve for both acceleration and deceleration. When starting light engine the loco will take off like a scalded cat, and then decelerate sharply; and the sudden surge when close to rest when declerating would look very strange. Is there a system which will toggle between the factory set speed curve and a user defined speed curve with the 'wheelslip' built in? If this were arranged so that the 'wheelslip curve' was only used in starting a heavy train the effect would be achieved; note however that the deceleration surge would still occur, but this might be acceptable if for example it was 'off-scene' in a fiddle yard. Might be worth investigating with Zimo or ESU, as their products are very much oriented to operational refinement. A good example from Zimo is directional assymetry, so that with a tender engine, progress in the reverse direction can automatically be made to vary from normal forward operation.

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Brian Considine

· #4 · Oct 1, 2007

QUOTE (34C @ 1 Oct 2007, 09:37) <{POST_SNAPBACK}>It is very easy to do manually with DCC, with a heavy train on, exactly as you would with a DC controller. On the Lenz system I would get the loco just started on speed step one or two in 128 speed step mode with function 4 (direct drive) activated, then push the 'big speed up button' once or more, then when you have had enough wheelslip push the 'big speed down button' as required.

Won't work if you have very steady (prototypical) acceleration set for CV3 - if the decoder supports it you could use the function for shunting speed which overides accelleration/deceleration but then you will only get half of your top speed.

Tried it on both the LH100 & a FLM Twin-Centre.

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Edwin

· #5 · Oct 1, 2007

QUOTE (dbclass50 @ 1 Oct 2007, 11:30) <{POST_SNAPBACK}>Won't work if you have very steady (prototypical) acceleration set for CV3 - if the decoder supports it you could use the function for shunting speed which overides accelleration/deceleration but then you will only get half of your top speed.

Tried it on both the LH100 & a FLM Twin-Centre.

I think the previous poster is using one of the decoders where f4 can be set to disable the limiting of acceleration but has no effect on top speed. Zimo MX620 certainly does this, probably others too.

I think MX620 can also store multiple sets of CVs and load one instantly when wanted, but it's controlled by writing a CV not by operating a function.

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34C

· #6 · Oct 1, 2007

QUOTE (dbclass50 @ 1 Oct 2007, 11:30) <{POST_SNAPBACK}>Won't work if you have very steady (prototypical) acceleration set for CV3 - if the decoder supports it you could use the function for shunting speed which overides accelleration/deceleration but then you will only get half of your top speed.

Tried it on both the LH100 & a FLM Twin-Centre.
Lenz silver and gold decoders are factory set to have function 4 overriding all acceleration and deceleration delays; should have made that clearer in my earlier post, rather than just 'Lenz system'. Similar effect to the shunting speed mode, but top speed is unaffected.

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John

· #7 · Oct 3, 2007

Dear All,

Looking at the Zimo Manual for the MX620, MX63 and MX64 family of decoders (N and H0/00 loco decoders), I found the following :-

QUOTE Shunting and half-speed functions:

By defining the different Configuration Variables (#3, 4, 121, 122, 123), a prototypical acceleration and deceleration behavior is achieved that often makes shunting very difficult. With the help of CV #124, a shunting key can be defined (either the dedicated MAN key within a ZIMO system or the keys F4 or F3) with which the acceleration and deceleration rates may be re-duced or eliminated all together. CV #124 may also be used to define either F7 or F3 as low gear key. With this function turned on, the throttle is used for half the decoder's full speed range, which is just like shifting down into low gear.

Example: The F7 key should act as low gear and the F4 key should reduce the momentum down to ¼. According to the CV table, the bits in CV #124 are to be set as follows: Bit 0 = 0, Bit 1 = 1, Bit 2 = 1 and Bit 3 = 1. The sum of the individual bit values (0+2+4+8 = 14) is entered as a decimal value.

CV124 controls Shunting key functions, Momentum reduction or deactivation and Low gear and SUSI assignment.

CV124 can have the following values (0 is the default value) :-

Bit 2 = 0: "MAN" key for shunting, = 1: F4 key for shunting (see Bit 6 for F3 key instead of F4)
Bit 0 = 0: no effect with above key's = 1: removes momentum of CV #121+122
Bit 1 = 0: no effect, = 1: CV #3 + 4 reduced to ¼.
Bit 0 + Bit 1= 0: no effect = 1 removes all momentum above.
Bit 3 = 1: F7 as half speed key
Bit 4 = 1: F3 as half speed key
Bit 5 = 1: For "DC" stopping method *)
Bit 6 = 1: F3 as shunting key (instead of F4 as in Bit 2).
Bit 7 = 1: SUSI deactivated. Solder pads can be used as FO3 and FO4 instead.

*) If "DC" stopping method is used, set CV #29, Bit 2 = 0 and CV #124, Bit 5 = 1 !

So you can have the shunting (half) speed, or you can reduce momentum (reducing or removing the effects of CV 121 and CV 122), but you can't really have a completely different speed curve, just a modified version of the speed curve currently loaded. I am not sure if this give you what you want for slipping?

Of course, you can assign a slipping sound to a function key and then just press this key when you start up and need the slipping noise. With computer control, you can probably automate this function key under certain conditions, but I have never looked that far into computer control.

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