Need Help With Display Layout

[BCR751]

I am part of a group that is planning an N-Scale display layout.  The layout will be on public display with a single train running approximately 8-10 hours per day.  It will operate on DC only.  The layout will have both uphill and downhill grades of approximately 2%.  We want the train to run at a constant prototypical speed both up and downhill.  The number of cars in the consist will not change.

I kinda know what I want to do but don't know how to do it and here's where I need some help.  I'm thinking to achieve a prototypical speed of, say, 25 scale miles per hour, the locomotives (2) with about 30 cars will require 'x' volts dc and draw 'y' amps of current on flat ground.  When it starts up grade, it will require an increase in voltage to maintain the required current.  Conversely, when it starts down grade, less voltage will be required.  I believe the way to achieve the desired result is to have a circuit that senses the change in current requirements with respect to the desired speed and regulate the voltage to the locomotives accordingly.  The circuit could be fed with a regulated and filtered power supply capable of providing 12vdc at about 2-3 amps.  The circuit would then send the required voltage and current to the locomotives through the rails to maintain the required constant speed.

I am open to any and all suggestions as to how to achieve the desired result.  Over to you.......

Doug

[C855B]

The easiest engineering I can think of is to simply jump behind DCC and use BEMF decoders (most any current design). They'll keep a constant speed.

To do it otherwise is going to require custom design including multiple power districts that set the "throttle" separately. It will be hard to tune for consistent operation, finicky, and equally difficult to maintain. Let's just say I've been there.

[peteski]

Why not let the train slow down and speed up  while climbing and descending. After all, don't the 1:1 scale trains do that?

Otherwise I think that the required circuit will be rather complex (and I'm not sure how well it will actually work).  Like C855C said, it will most likely have to be based on BEMF feedback.

[Ron McF]

We want the train to run at a constant prototypical speed both up and downhill.

Can you wire the layout as three separate electrical blocks (from the one power supply), and then use diodes to drop the voltage to those blocks you want the train to run slower on? For example, no diodes on the uphill section, one on the flat, and two on the downhill.

Regards,
Ron

[peteski]

Can you wire the layout as three separate electrical blocks (from the one power supply), and then use diodes to drop the voltage to those blocks you want the train to run slower on? For example, no diodes on the uphill section, one on the flat, and two on the downhill.

Regards,
Ron

Now that is a clever (and very simple) idea!

[BCR751]

Can you wire the layout as three separate electrical blocks (from the one power supply), and then use diodes to drop the voltage to those blocks you want the train to run slower on? For example, no diodes on the uphill section, one on the flat, and two on the downhill.

Regards,
Ron

Now that sounds interesting.  I'll check into that.

Someone mentioned that CTI Electronics makes some sort of computer controlled stuff that may work.  Anyone ever heard of this company and/or their products?

Doug

[BCR751]

Although the 'block' idea sounds plausible, it wouldn't work for a number of reasons.  I still would like to hear about that CTI system but it appears that no one on this form is willing to discuss it.  Failing that, the DCC scenario appears to be the best option and we will explore that one. 

Over and out.

Doug

[peteski]

I still would like to hear about that CTI system but it appears that no one on this form is willing to discuss it. 

Well, Doug, how about the possibility that nobody here has any experience with that system?  I know I don't.  BTW, it was not me how down-voted your post.

[BCR751]

Well, Doug, how about the possibility that nobody here has any experience with that system?  I know I don't.  BTW, it was not me how down-voted your post.

I considered that possibility but given the large membership of this group, I thought someone would have some experience with it or know of someone who did.

As for the down-vote, that sort of crap doesn't bother me.  I just consider the potential source and shrug it off.

Doug

[peteski]

I considered that possibility but given the large membership of this group. . .

Actually, as far as (the active) membership goes, I think this forum is fairly small.  That is actually the reason I enjoy participating in the TRW - there is no flood of 100s of new messages every day. The number of daily posts is to me just right.  Plus the N scale bias is also welcome.  I still think that lack of replies is due to the fact that the currently active set of members simply is not familiar with the product.

[thomasjmdavis]

Doesn't look all that hard to find info on
http://cti-electronics.com/

Computer interface, by the look of it.  But I would suggest just calling them, tell them what you want to do, and let them recommend a product/method.  Their webpage also links to a user group, that I am sure could provide advice.

Frankly, I like the diode idea (never tried it, but sounds good)- or, as was suggested, let the train respond realistically by slowing uphill and speeding up downhill.

[Ron McF]

Although the 'block' idea sounds plausible, it wouldn't work for a number of reasons.

I'd be interested to hear your reasons, because I've been using diodes to slow trains when they enter the 12" radius reversing loops in my staging yards for ~ 30 years and they work very well.  The only problem I've encountered is that if trains are going very slowly when they enter the block (with the diode) the reduced voltage might be too low for the loco to keep moving.

There will possibly be a noticeable change in speed as you cross block boundaries, but it's a lot cheaper than implementing a DCC system.

Regards,
Ron

[Chris333]

If this works please post here. I've always kept my layouts flat because I just let the trains run and the fast/slow kills it for me. If this works it could open up a whole new world for me 


In fact after making sure my current door layout frame was perfectly flat with a 6' level. I still noticed trains slightly changing speed. I put the level up on the rails and saw one side was 1/8" higher. It was an easy fix, but just shows how much I hate model grades.

[peteski]

If this works please post here. I've always kept my layouts flat because I just let the trains run and the fast/slow kills it for me. If this works it could open up a whole new world for me 


In fact after making sure my current door layout frame was perfectly flat with a 6' level. I still noticed trains slightly changing speed. I put the level up on the rails and saw one side was 1/8" higher. It was an easy fix, but just shows how much I hate model grades.

I don't think the diode circuit will work for you because there will be abrupt speed change when the loco enters or leaves the diode-powered block.

In your case I think that using coreless motors with gearboxes would probably be a good solution.  The output shaft of a geared motor has plenty of torque and the coreless motors are very efficient.  I think that the speed difference in running over flat or inclined/declined track would be minimal.

[BCR751]

While I understand the concept behind the diode option, I agree with Peteski that the train would experience an abrupt change in speed when hitting the diode block.  This could cause other issues when the slack runs in/out.  Also, in our situation, although the diode option is sound in principle, we have logistical issues that would preclude using it.

A basic DCC system would likely be the best option but it would be pretty expensive for what we want to do.  Lots to think about.

Doug