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· Beppe Giannini
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1,698 Posts
Two comments :

A ) The "Speed" command is really a "Volts to motor" command. A train/car will accelerate until it reaches equilibrium @ that voltage. I believe there is a fundamental difference here, trains would seem to be at equilibrium most of the time, while slot cars are notoriously always accelerating unless you have a 10 m long straight and short gearing

B ) One should consider that a slot car has no gears and that a brushed DC motor's torque vs. speed curve is totally different from an internal combustion engine (max torque @ 0 rpm, then decreases linearly)

So, my reasoning (I might well be proven wrong) is that the latest curve would give you too few "low" steps - where the motor response is torquey - and too many "high" steps - where response is sluggish
 

· Beppe Giannini
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1,698 Posts
Hey, you know I'm semi-literate - it took me six months to learn how to post pictures !

I would say the default curve is more appropriate
Rather, have you set Vo=start voltage=CV2 ?
Also, have you tried going to 14 speed steps ?

Ciao
Beppe
 

· Beppe Giannini
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1,698 Posts
Some confusion here - not helped by DCC manuals quite improperly using "speed" and "power" instead of " Volts to motor"

Let's recap :

- CV 2 sets the voltage @ step 1 (just enough so the car moves). This is a % of available (decoder inlet minus rectifier drop) voltage, and for some NMRA reason is expressed on a scale from 1 to 255

- CV 5 sets voltage @ full throttle (step 14, 28 or 128 to your taste) - again as a % of available voltage and again on a scale from 1 to 255. So if you want your kids playing safely, you set it as say 190 [for the same reason, IMO "racing" decoders should have this nailed at 255, forget yellow flags and handicapping]

- the curve we've been dealing with assigns a voltage to each intermediate step, so yes Astro it's related to trigger response - one would mess with it according to driving style, motor winds/gearing and type of track [Doug, if you are bypassing CV 2 and CV 5 and establishing the entire curve directly, it should start with 50-70 @ step 1 - but still "sag" as it goes up to 255 @ step 28]

Now we can go back to the more confortable realm of electro-mechanics : once a voltage has been set, a motor has a well known torque/speed characteristic, while the car has a given inertia and a (less well known) drag/speed curve - it will accelerate and reach steady speed on that basis
 

· Beppe Giannini
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1,698 Posts
QUOTE CV2 is minimum speed: set to 0 (or no volts)

Respectfully, it's not speed, it's voltage - at which step does the car start to move ? You should see which "speed (grr) value" this corresponds to and input that as CV 2 (or CV 67/step 1) in the new curve
 

· Beppe Giannini
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1,698 Posts
I believe Astro is saying that, if you really want to match the Porsche's acceleration curve, you need a quite different set of tools - mainly one or more speed traps (Alberto Elli makes them as an accessory to Wincrono) - and then work on motor and gearing

But first you would have to decide what scale is the track (we all know lengthwise it's not 1:32) and ditto for the speed
 

· Beppe Giannini
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1,698 Posts
Hi Tropi,

I wouldn't worry about the speed curve - after all, it's very much like what committed racers already do with their electronic (say NSR ) controllers, or even screwing/unscrewing diodes on PM ones

I do worry a lot about the yet untapped possibilities : using back-emf for traction control, and overriding general speed limitations (yellow flag, handicaps, etc ) one might think of - that's why I'm basically suspicious of "bells & whistles"

Ciao
Beppe
 

· Beppe Giannini
Joined
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1,698 Posts
Hi Marcus,

Luca - my partner for electronics - has covered all bases : cars are programmed on a separate track segment (to be conveniently located near the cashier
) and you have to insert a jumper on the decoder

This way, you can assign ID, reprogram throttle response curve and brake, even introduce a performance handicap

Since the decoder sits in the pod below the car, access is not an issue

BTW, about your other post on decoder connectors : I agree, and that is why on my track pods cum decoders can be swapped from a car to another just by loosening/tightening an Allen screw, the connection being both mechanical and electrical - the only price you pay is that, if you really want lights, you have to add a conventional light kit on the car

Ciao / Beppe
 
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