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Bob D
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I'm O-scale, but I figure this would apply to all scales.

I know there's adjustments for the Deltang Rx65x (RCS of Australia ALPHA3v2) concerning Inertia, but I guess I'm really not sure how inertia works.

From the v611 features/instructions, inertia/soft start/momentum are the same thing?

Is there also an adjustment in the transmitters (I use the RCS Tx3 and Tx7k)?  I don;t think so but thought I'd ask.

What can I expect to see when the engine/train starts to move or starts to stop if inertia is changed?

What about inertia in a 0-6-0 switcher that doesn't get over a certain speed most of the time anyway?

Most, if not all, of my engines (steam and diesel) have flywheels on them also, so what effect would the flywheel AND inertia have together?

Would inertia help an engine that has poor-fair-good-excellent gearing?

Would inertia help a larger engine more than a smaller engine?

The v611 instructions indicate there's "immediate" to "8 seconds", is that a delay time or is the speed gradually ramped up during that 8 seconds?

I suppose the best way is to try it and see, but I thought I'd drink from this vast well of knowledge first :thumb:

BobD.

Rod Hutchinson
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I have a deltang TX22 throttle. The inertia is controlled from that. You may use it or not use as you wish.

Inertia slows the start and end of the loco speed cycle.

My locos are geared locos so I don't use inertia at all.

davecttr
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I believe the Rx 'on chip' inertia ramps between 0 and 8 seconds but have only used the default so far. The inertia knob on my Tx-22's are actually timed throttle increases which do not change the 'on chip' inertia. There could be some interesting combinations there!

NevadaBlue
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I use inertia on my Air Porter loco and it makes movement much more realistic I think. Instead of the motor just stopping when you turn down the throttle, there is a 'soft stop' if you will. I like it.
I need to experiment more with all the settings on the transmitter.

DavidT
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Bob, I expect models to have a much higher power to weight ratio than full size trains so can benefit from some electronic aids...

1. The Inertia setting in the Rx does what I expect a flywheel to do which is to dampen speed changes in a short timescale. If you have both then both are having an effect.

2. The Inertia control on the Tx simulates train 'mass' which slows down speed changes over a larger timescale (up to 1 minute with center off motor control). The instructions for your product will tell you if you have this control.

3. BEMF reduces the need for operator skill/finess to control stiction and wheelslip. My Rx do not have BEMF but do have a minimum start power setting which perhaps falls into this category.
Regards, David.

Bob D
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Thanks guys :2t:

So changing the Inertia setting causes the speed to ramp up/down in a 0 to 8 second time frame.

The MIN voltage (Start Power) setting can be set so there's 0 to MAX volts on the motor as soon as it is turned on.

The reason I'm asking is I have 1 or 2 engines where I have to turn the throttle knob almost 40 degrees to get the engine to move, and at that point it suddenly starts moving, quicker than I would like. My other engines (different brand than the 2 in question) start to move at around 20 degrees of turn of the knob.

It may be due to some binding (in which case changing settings probably won't help) and I'll take a look into that. It could also be the gear ratio, my engines with higher ratios (like my Williams brass 4-8-4, 43:1) start off smoothly with a very small turn of the knob.

I may want to change the MIN start voltage first, then play with the Inertia setting.

The 2 engines in question have their engines mounted at an angle with the engine mount screwed to the chassis. The screws may be too tight and causing binding between the gear/worm on the motor shaft and the gearbox. I may loosen them up a bit first and see what happens.

BobD.

NevadaBlue
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I have found that different motors have a lot different starting characteristics. My Air Porter starts so beautifully, I can make it start so slow you have to set stakes to see it going. My Little Mine loco has a different type of motor, one of the old HO locomotive motors. It doesn't like to get going slowly. I'll have to look into the settings on the Rx for it I guess.

Bernd
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I've been experimenting with a mechanical momentum system using an Eddy Current drive.

http://kingstonemodelworks.com/ECDtb.html

Bernd

Bob D
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Bernd, I saw where you had mentioned this before, interesting!

It got me looking at my old magazines and found this Fluid Drive clutch in the August 1951 Model Railroader:


I guess as long as it doesn't leak we'd be OK, but it could mess up all the fancy electronics we now put in our engines.

BobD.

Bob--Sorry, but I had to remove the Model Railroader article. Kalmbach is very nasty about their copyrights

Herb

Budd
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Bernd wrote:
I've been experimenting with a mechanical momentum system using an Eddy Current drive.

http://kingstonemodelworks.com/ECDtb.html

Bernd


Who is Eddy Current and what scale does he model in?

???

Wayne from Oz.

Bernd
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Budd wrote:
Bernd wrote:
I've been experimenting with a mechanical momentum system using an Eddy Current drive.

http://kingstonemodelworks.com/ECDtb.html

Bernd


Who is Eddy Current and what scale does he model in?

???

Wayne from Oz.


He's a friend of mine with a very magnetic personality and he models in both HO and TT scale. :Salute:

Bernd

Bernd
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Bob D wrote:
Bernd, I saw where you had mentioned this before, interesting!

It got me looking at my old magazines and found this Fluid Drive clutch in the August 1951 Model Railroader:

I guess as long as it doesn't leak we'd be OK, but it could mess up all the fancy electronics we now put in our engines.

BobD.


They did leak. The other problem was the seals. To much friction. The Eddy Current drive has very little friction using miniature ball bearings. I need to expand further on this subject. I have much more experimenting I want to do.

Bernd

Budd
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Bernd wrote:
Budd wrote:
Bernd wrote:
I've been experimenting with a mechanical momentum system using an Eddy Current drive.

http://kingstonemodelworks.com/ECDtb.html

Bernd


Who is Eddy Current and what scale does he model in?

???

Wayne from Oz.


He's a friend of mine with a very magnetic personality and he models in both HO and TT scale. :Salute:

Bernd


Is he the son of D.C. and A.C. Current? shocking family, I think they used to drive a Voltswagen.

That's it from Wayne from Oz.

Budd
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On a serious note, my set up is Tx22 and Rx65 in a diesel, the engine has a flywheel fitted, on 'zero' inertia setting there is some inertia effect, just the right amount for my liking. On 'max' inertia setting, the only change was that it took a l..o..n..g time to start then acceleration was very brisk any way and shutting it of had little effect in that it wouldn't stop. The Tx was 'centre off' then, I have since changed it to 'low off' and found I need about 40% of throttle movement before the engine moves off, I have wondered if this was having an effect on any 'max' inertia setting. It doesn't matter now as I have removed the inertia knob/control from my Tx, so other than getting some engine movement at a lower throttle setting I am very happy, I just turn my knob slowly.

Wayne from Oz.

Bob D
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Budd wrote: On 'max' inertia setting, the only change was that it took a l..o..n..g time to start then acceleration was very brisk any way and shutting it of had little effect in that it wouldn't stop.

Wayne from Oz.

Wayne,  that's what I'm seeing also.

When I turn the throttle knob on my RCS Tx7k or Tx3 I have to turn it approximately 25-30 degrees to get the engine to move.  When it does it's not a jack-rabbit start, but not a slow ramping up of movement as I would like.

I only have this problem with 2 out of 8 engines, so I'm pretty sure it's not the electronics but the mechanics (weight, gearing, mass, etc) inside the engines.

So...if it takes "X" voltage to overcome the mechanics, changing the Inertia setting IMO won't entirely solve it, but changing both Inertia and Min (Start Power) voltage may (so I don't have to turn the knob 25-30 degrees before the engine begins to move).  Or maybe changing just the Min setting will fix the issue.

It's been so long since I dealt in physics (or electronics theory) that I may not be saying this correctly.

BobD.

Bob D
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Hey!!! I've been on the forum for a year now.

HAPPY ANNIVERSARY [toast]:2t::moose:

BobD.

fallen
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As I understand it, the inertia knob on the TX adjusts the speed at which the TX responds to the settings of the speed knob. No inertia and the signal follows the knob, high inertia and the signal lags behind the movement of the knob.

So if you set the inertia knob to high, then start off the loco, it takes a while for the signal being transmitted to get up to the threshold at which the loco will start. This causes the delay in starting.

I suspect Bob's solution of adjusting the start power should do the trick.

Frank

davecttr
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To amplify a little on what Frank said. As i understand it the TX transmits about 50 data packets per second. If you set the inertia knob to say 10 seconds the Tx will ramp up the 0% to 100% throttle settings by 1% 10 times a second???

Then we have 'stiction' which I believe is the effect of all the motor and drive train issues that mean the loco won't move until a certain voltage is reached.

We want smooth starts so our tiny passengers don't get hurled off their feet or put in compensation claims for backlash neck injuries!

Increasing the MIN setting may help although I would leave a little bit of dead throttle as driving for real is fun. back in the day the driver had to learn the 'feel' of the loco and did not have inertia control or back EMF.

Back EMF might help but Deltang RX does not have it. I am interested in trying a Bluetooth receiver which may?. I have one loco with an ancient tender drive that accelerates at high G to about scale 15mph, killing all the little people in the process.

ps - there is another reason for keeping some flexibilty in the throttle - lighting. I have not converted my diesel multiple unit yet but when i do it would be good to have the lights working. There is lighting control in the Rx. Stop the train and the lights remain on. Reverse and the front/rear lights swop over. If you set the MIN so the train does not start immediately you can 'blip' the throttle and the lights will change without the train moving, just like real life.

W C Greene
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Happy anniversary Bob...maybe it's my anniversary also, I have been "wireless" for about 16 years now. Been having fun while everybody else looks for brite boys and short circuits.

Outlaw Troublemaker-my official title in the Texas Outlaws On30 group

Bob D
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Thanks guys (and thank you "Outlaw")

I think I'll adjust the MIN a bit and see what goes.

If I adjust it, what happens at the top end?

If the voltage is set higher at the low end (let's say the engine starts moving at 15 degrees, I would think I would top out at 85% (movement of the knob) and the rest of the throttle knob movement wouldn't do anything?

Bob

davecttr
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Bob D wrote:
Thanks guys (and thank you "Outlaw")

I think I'll adjust the MIN a bit and see what goes.

If I adjust it, what happens at the top end?

If the voltage is set higher at the low end (let's say the engine starts moving at 15 degrees, I would think I would top out at 85% (movement of the knob) and the rest of the throttle knob movement wouldn't do anything?

Bob

According to David T if you set MIN to say 10% and MAX to say 85% the full movement of the knob will give 10-85% rather than 0-100%, I think ?

Last edited on Sun Apr 3rd, 2016 05:54 pm by davecttr

Bob D
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Dave,

See if this makes sense, I'm probably leaving something out but this is about as easy as I can explain what I'm thinking:

I have an 11.1v battery, the RCS Tx3/Tx7k has 300 degrees of throttle knob rotation.  If I leave the settings alone I get:

0---------11.1volts
0---------300 degrees of throttle knob rotation
(so 1 degree of rotation = .037 volts)(11.1/300)

Now if I change the low end (MIN) to 10%:

1.11 (10% MIN change)------11.1volts
0---------300 degrees of throttle knob rotation
(so 1 degree of rotation = .033 volts)(11.1-1.11=9.89) (9.89/300)

Are these things that linear or have I completely fallen off the track???

I guess the only good way of showing this would be on a scope, which I don't have.

Anybody buy one of these yet:

NANO SCOPE

Bob

davecttr
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That calculation looks OK if the pot is truly linear but apparently manufacturing tolerances will mean the voltage curve will not be a straight line but wobble about a bit. I tested this some time ago the hard way by measuring the output voltage with different throttle settings, not an accurate way of doing it.

Last edited on Sun Apr 3rd, 2016 11:00 pm by davecttr

Budd
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Bob D wrote:
Budd wrote: On 'max' inertia setting, the only change was that it took a l..o..n..g time to start then acceleration was very brisk any way and shutting it of had little effect in that it wouldn't stop.

Wayne from Oz.

Wayne,  that's what I'm seeing also.

When I turn the throttle knob on my RCS Tx7k or Tx3 I have to turn it approximately 25-30 degrees to get the engine to move.  When it does it's not a jack-rabbit start, but not a slow ramping up of movement as I would like.

I only have this problem with 2 out of 8 engines, so I'm pretty sure it's not the electronics but the mechanics (weight, gearing, mass, etc) inside the engines.



BobD.


And to add to this thread, I have just fitted Rx60's to an Athearn Mikado and a shunter powered by 2 Steam Era Black beetle drives, both programmed for low off, and they run superbly from near zero throttle, so it must be all about the mechanics of a drive. All have some inertia effect even though I have removed the inertia pot from my TX22.

Wayne from Oz

Bob D
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Thanks Wayne [toast][toast]

I haven't had a chance to do any testing of my own, a couple of projects got in the way and my daughter, son-in-law, and grandson came in late last month from Sicily for a few weeks.

Being I have all but 1 or 2 engines running fine and using the same gear, I'm calling it mechanical as well.

BobD.

Bob D
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Wow, it's been a year since I last posted to this topic.  Not sure what made me even look at the post L:
Kinda strange, it's also been 3 years since my wife passed.
Anyway, I haven't done any testing, things seem to be working fine as they are. I did notice that my 2 best slow running engines have 15vdc motors in them where the others have 12vdc from what I can tell.
I'm considering converting an AtlasO F3 from TMCC to BPRC, this will be my first diesel to get the Rx65b.
All my diesels have 2 motors (the steamers had only 1), I hope they don't draw too much current, I think there's a flywheel on both motors, but need to open it to make sure and to make sure there's enough room for the battery.  Hiding the on/off switch and the charging jack will be a challenge, I want to locate them so I don't have to lift the engine off the track.
Has anyone done any testing with the inertia settings?

Helmut
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I use the inertia control 'as is' on the Tx22 and only as a brake. That is, when starting the inertia knob is mostly set to the low position, but before slowing down, I turn it fully up, close the regulator and use it to control the rate of slowdown. Works fine for me.

Bob D
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Helmut,

I might have to get a TX22 so I can easily change the inertia.  I have the Tx 2, 3, and 7 from Tony W. at RCS Australia, but they don't have a knob specifically for inertia.

A knob would be much easier than changing the programming.  However, the RCS Tx are doing fine for my purposes right now.

Again I would like to thank TonyW and DavidT for offering their great products.  Going on 3 years now and ZERO failures or glitches (other than those caused by "pilot error").

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@BobD,

I have worked with the inertia control on most of my models.  It seems a little goes a long way, I rarely turn it beyond 1/4.  I plan to play around with different pots to see if I can adjust the full travel more to my liking.

I have used the inertia setting on some receivers to limit acceleration for motors where rapid acceleration can overload the voltage step-up converter that I used.

There was a question about a NanoScope, I have a PicoScope (2204 low end) and am really happy with it and the software.

boB

DavidT
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Bob, So you know what you are dealing with, Inertia in my Tx2 product has 32 steps. You can add resistors to make the pot only give you access to a smaller number of steps. Regards, David.

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David,
thank you for the information!  Are the 32 steps linear?  Now I am thinking of using a rotary switch with resistors to provide a positive selection.

boB

DavidT
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Not quite. I believe these are the timings of the 32 steps:
0.028
0.117
0.352
0.704
1.408
2.347
3.520
4.693
5.280
7.040
8.213
9.387
10.560
11.733
14.080
15.488
16.896
18.304
21.120
22.528
23.936
25.813
28.160
30.507
32.853
35.200
38.720
42.240
44.587
49.280
51.627
56.320

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Thanks again David, this is very useful information!

boB

Bob D
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Bob and David, thanks for keeping this going!

I haven't been doing much on the train hobby lately, my daughter & family moved in with me back in April and just last week moved out and into their new house. Now I plan on getting my kitchen remodeled so I may have less (or hopefully more) time for trains in the next months.

Last edited on Thu Aug 17th, 2017 11:38 pm by Bob D

Richard A-J
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Yes Bob, let's talk inertia. Great to see this thread on the subject, I look forward to studying it, but first I would like say something about the model railway world's relationship with inertia. It has always puzzled me that inertia is seen as an add-on feature. Something you can have or not have. This way of looking at inertia for a model I find very puzzling. To me it's the like asking yourself 'Shall I do it right, or not right?'. The way I see it there are models and there are toys:-

Toys are simple representations of the real thing
Models are accurate.

If you are going to make your model move, it means its movement must, by definition, model that of the real thing otherwise it is not a true model. It does not mean that it should only sometimes move like the real thing, just as it should not only sometimes look like the real thing. It also does not mean that the operator should be given a choice in the matter. Whether a model models the real thing or not should be down to the model maker, not the model operator. An operator of the real thing cannot extinguish inertia when they feel like it, and even if they could, would they be able to survive the G forces? The performance specifications of the real things are fixed, the locomotive driver / engineer cannot alter those specifications whilst driving (well not drastically anyway), they cannot make it accelerate or stop faster than its specifications just because they are late in the timetable or want to get some shunting done quickly.  If a certain locomotive has an acceleration rate of 0-60mph in 1 minute, the model should not be capable of scaled 0-60 in 1 second.

In the real world there is no such thing as zero inertia, it is not switch offable. The whole design and maintenance of track, wheels and the need for signalling, catch points, the speed operators drive and all safety features are all massively influenced by that one fact.

I believe that all models (to earn the title) should have inertia, and it should not be switch offable, so therefore the main means of giving a model inertia I suggest should be mechanical. The trouble with electronic inertia is that it can be switched off, either intentionally or unintentionally, consequently I think it should only be used as an aid to mechanical inertia so therefore I applaud Bernd's attempt at doing this … well done Bernd, excellent work. Of course mechanical inertia could also go wrong but with the biggest of flywheels possible even if it did go wrong it would hopefull not show in a sudden stop (one of the worst illusion spoilers). A flywheel should always be bigger than the motor, and preferably made out of tungsten (if anyone knows how the do that, where to buy it without costing a fortune, please enlighten me).

I think inertia should be easily adjustable by the operator whilst driving … BUT … there should be no zero inertia setting. The lowest setting should aim to replicate the inertia of a 'light' engine i.e. a locomotive with no train. The operator then should have the ability to adjust the inertia whilst driving in order to simulate that of pulling and stopping a train. Of course, if that could be done mechanically aswell then all the better.

Rich

Last edited on Wed Sep 13th, 2017 11:18 am by Richard A-J

Tony Walsham
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In large scale I can never understand the attraction of any inertia options at all.
If you want to simulate the speed up and slow down of a heavy train, just turn the speed control knob more slowly.

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Since we are trying to simulate accelerating many tons with a tiny flywheel our results are not likely to be realistic. Electronic inertia has a different problem where the control does not know actual motor speed. One solution is to look at back electromotive force (BEMF) and many DCC controls do just that. A potentially better method (especially at low speed) is to use a speed encoder to provide feedback. With either of these methods the speed control knows the actual motor speed instead of just providing a certain PWM and hoping it looks realistic.

Pololu sells inexpensive ($8.95) encoders (optical or magnetic) that are made to fit some of their motors but could be adapted to many others by using NWSL adapters/joints/shafts. We would need something to read the encoder output and control motor power accordingly, probably a microcontroller and a motor driver board. Hey, who said realistic inertia was easy? With a microcontroller reading 12 pulses per revolution of the motor we can precisely control acceleration to simulate any amount of inertia required.

Total cost would be less than $20 for a do-it-yourself kit (programming not included).

Reading BEMF is not difficult either, we just shut off power to the motor for a brief time and read the voltage into an A/D converter. The microcontroller I use converts the voltage in about 25 uS and takes another 25 uS to send a correction signal to the motor. The downside of BEMF may be poor response at low motor speeds where the voltage is too low or erratic to provide a good signal. Some testing will determine which method works best.

I like the eddy current idea (and may try it) but the electronic methods look easier and even the eddy current plan would probably work better with an encoder and feedback.

Or we can turn the knob slowly, which is what I do for now. :)

Helmut
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As I'm using DT's transmitters, the 'inertia control' on them does it for me satisfactorily. BEMF as such has nothing to do with inertia simulation, it only helps to follow the set speed value.

Richard A-J
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Tony Walsham quote "If you want to simulate the speed up and slow down of a heavy train, just turn the speed control knob more slowly."
Bobquincy quote "Or we can turn the knob slowly, which is what I do for now. :)"

What I am pointing out is that I think prototypical movement should really be the job of the model, not the operator. A driver of the real thing does not have to slowly push the throttle lest the locomotive should shoot off like a rocket … or likewise be carefull with the brake in case it stops dead. (Sorry Bob, I'm not knowledgeable enough about electronics to understand your idea).

There seems to be a thinking that inertia is just for heavy trains. Blimey, locomotives are heavy beasts also and they have some considerable inertia all on their own. I still think electronic inertia should be kept to adding the final touches to mechanical inertia. I reckon the key to inertia is the fact that with the real things, starting and stopping is difficult. With our models it is ease peasy lemon squeezy. We need to make it difficult and I think the way to do that is by using weaker motors, motors that are too weak to shoot off your locomotive like a Formula 1 racing car.

So, how do you then get your locomotive moving if the motor is too weak? Answer - you use a higher gear ratio, in fact you use a CVT (Continuously Variable Transmission). A weaker motor could get a model moving if it is starting off in a gear ratio of, say 400:1. If it also has a massive flywheel, once it has got going it will have the energy from the flywheel to keep it going and give it extra power. As the locomotive increases in speed the CVT moves down in the gears.

Of course, making a CVT is going to be difficult, but I think it needs to be tried. A one gear ratio to fit all speeds is not really a good system in my opinion.

I think such a system might also make wheel slip starting much more realistic, in fact, I get the feeling it might mean a locomotive could pull heavier loads, because it is not trying to start in top gear, but I don't know. The motors being smaller and the help of a flywheel might also be an advantage for battery life, not sure about that either, does anyone have any ideas on that?

Rich

Last edited on Thu Sep 14th, 2017 07:38 pm by Richard A-J

bobquincy
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As an electrical engineer (retired) I will leave the flywheels and CVT to the mechanical engineers, electronics is more my thing.  A weaker motor is easy to do, on a very basic level the motor power is from the magnetism which is governed by amps x turns of wire.  The turns of wire being set, less amps = less power and we can easily control the amps.
The problem is how do we control the amps properly in order to provide a smooth, consistent acceleration?  A lookup table (as used by Deltang) is one way (also the simplest way) but cannot account for stiction; motor nonlinearity; or any other of the complex parameters of a moving device.

A speed control system without feedback does not work well: think of cruise control in a car where the system could only set a certain throttle opening (from a lookup table) and assumes that will maintain a certain speed.  It doesn't work, feedback (in the form of a signal reporting the actual speed) is necessary for the system to maintain a given speed.  Our trains require a certain current to start but once friction is overcome the current should be quickly reduced to provide a smooth (and slow) acceleration.  Feedback on motor speed can provide the correction.
Disney's Disneyland Mark VII monorail model comes with a remote control, on/off, zero inertia!  I added a microcontroller programmed to ramp up a PWM output to the motor from zero to full power over 5 seconds, it works nicely to provide a soft start/stop but I can see the nonlinearities and quirks in the system.  It is still a lookup table type with 64 steps of PWM and no feedback.
I plan to add a speed sensor to the motor and program the microcontroller to maintain a constant acceleration, it should work a lot better.  You may think this is a lot of electronics and programming just for inertia, you would be correct!  But it is probably less than the DCC manufacturers did to add BEMF to their decoders, apparently they considered it useful and worthwhile.

Richard A-J
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Bobquincy quote "A weaker motor is easy to do, on a very basic level the motor power is from the magnetism which is governed by amps x turns of wire.  The turns of wire being set, less amps = less power and we can easily control the amps."

I wasn't thinking of actually making a weaker motor, just buying one :)  I'm afraid the rest of your post is beyond my electronic know how. I do mean to learn more about electronics, it is knowledge needed for this hobby, it's just that I consider inertia too important a feature of modelled movement to be left entirely to electronics alone. For me the sudden stop or start of a model totally ruins the effect. I then see a toy, not a model, and I think all steps should be made to stop it ever happening.

Actually you can make electronic inertia unswitch offable to a certain extent, as long as nothing goes wrong with the electronics.  The photo shows what I have done to my Deltang transmitter to make operations more realistic.

The screws on the inertia dial (top right) and the transmitter body stop the dial from being turned all the way around anti clockwise to the zero inertia postion which is at about 7 o'clock. Its travel is now limited to the 12 o'clock position where I have estimated that that simulates the inertia of a light engine (i.e. no train). Of course such a setting has to be general, it would be different for a little shunting engine than for a big express engine. If the loco then starts to move a train the inertia can easily be adjusted clockwise to suit.

E-Stop stands for Emergency Stop, which is a prototypical emergency stop. I do not believe zero inertia should be available for a model. To me that goes against the whole ethics of modelling.

Rich

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Last edited on Sat Sep 16th, 2017 09:39 am by Richard A-J


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