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John Street - BR(E) - 1960 - Members Personal Layouts. - Model Railway Layouts. - Your Model Railway Club
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 Posted: Tue Dec 18th, 2018 05:34 pm
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Dave C
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Well, that's the Terminus more-or-less completed.
 
Over the past week or so I've been working on trying to get an uncoupling ramp to work. Time has been at a premium recently so not much progress has been made on it. At the moment it's in two parts - first part (the ramp) is only on a spare length of track and the second part is still in the "I'm still working on it" phase - but the idea, culled from a number of various ideas from across the model rail community, appears to work nicely - up to a point! In the process of this project I'm learning quite a lot about controlling servo motors.
 
One important point I wasn't aware of (and doesn't exactly get mentioned on the 'spec sheet') is the amount of current these little devices take - and I get the impression that I'm not alone in this respect. Given that these devices can be used in model aircraft, I expected they would be relatively low current devices and so I thought a 7805 (a 1amp device) power supply would be more than adequate to run a single servo at a time out of a bunch of six. How wrong I was. That poor 7805 got stinkingly hot when two or more were connected, but with only one being operated!
 
But then again, all the servos did appear to be randomly 'jittering' while ever there was no command to move one of them. So I guess I need to find out why that is happening - then the current might drop (to the delight of the 7805!). There's plenty of code snippets out there so I have a few ideas to work on.
 
The controlling device is a PICAXE chip (18M2+ in my case - it's capable of controlling up to 8 servos; but only 6 will be used here) with a rotary selector switch and a push-button to activate/raise a particular ramp/servo. Following a 10 second delay the ramp lowers. That's the premise of it all. With only one servo in the program it works well, very well; add a second routine (servo no.2 control) and the jittering starts. Back to the drawing board on this one - I'll not be beaten, but time at the moment is not being kind to me.
 
Anyway, the following is a brief description of my version of the uncoupling ramp for standard tension hook couplings.
 
The servo used is an SG90 mini servo, bolted onto an angle offcut from an old VHS tape case, a length of 3.5mm OD tube and a couple of thin nails to keep the ramp aligned between the rails. The ramp itself is yet another VHS case offcut which sits down on the baseboard itself (once a few sleepers have been removed - this aligns itself nicely to the height of the remaining sleepers). The length of tube is glued into the ramp and passed down through the baseboard - the tube will be linked to a servo horn with a short length of wire (piano wire would be ideal). The nails and tube are all a loose slip-fit through the baseboard.
 


A sprinkling of ballast over the top of the ramp will hide it nicely. That's the 'plan'.
 
I had hoped a few more items might get installed before the festivities get fully under way - some street lighting at the rear of the terminus and a set of traffic lights. Then once all the uncoupling ramps are installed I can get on and get the ballasting down, followed by the platform lights.
 
That's it for now. Soon be time to down tools and enjoy the festivities for a few days.
 
Here's wishing you all a peaceful Christmas - I hope Santa brings you whatever is at the top of your wishlist.
 

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 Posted: Tue Dec 18th, 2018 08:12 pm
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Woodside
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S’mae Dave

I do like the look of your station, very nice. I’ve only used the Peco ramps/standard couplings on Woodside and found them to work reasonably well, but adjustments to get some couplings at the same height is needed on a fairly regular basis. Two methods I’ve used to disguise the ramps – in stations, darkening the ballast around the ramp – particularly Woodside Station, where the ballast is fairly dark to begin with near the buffers and in the marshalling yard putting the ramps ‘in’ the boarded crossing. Also, with the overall roof at Woodside, the ramps can’t really be seen. On Woodside station I’ve put a baggage trolley on the platform perpendicular to the track at the centre of the ramp – makes ‘seeing’ the ramp very easy when trying to uncouple an engine. In the fiddle yard I’ve got marker posts to do the same thing. No doubt all your computery stuff will be able to stop the train exactly over the ramp, but we simple souls need some help. I’d caution putting ballast on the ramps, certainly with my simple set up it could be that the coupling ends up between individual stones and then may not lift the coupling sufficiently to operate properly – if you see what I mean. If this is all rubbish, and I’ve got the wrong end of the stick, not unusual, please ignore.

Couldn’t agree more about lighting – definitely does bring a layout to life, day or night – and yes, don’t just light every ‘room’ – much better just to box in a couple of rooms or floors in a factory, and vary the brightness too, it all helps.

All the best for the festivities.

Keith



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 Posted: Tue Dec 18th, 2018 09:36 pm
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Dave C
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Hi Keith

All my computery stuff, as you kindly put it, doesn't stop the trains - that part of it is still manually and visually needed to make the 'stop' in just the right place. OK, so I use DCC, but it's still a visual job. Signposting is a definite must fit.

Where the computer thing comes in is to remotely activate the uncoupling ramps, mostly in places where I'd not be able to physically reach, or it would become too fiddly to use some form of manual rising mechanism. It seemed a good idea at the time, sounded promising - at least in my own mind!, and others have had a go at it. Not sure of the success rate, but who's counting?

Once we get the festivities out of the way, I'll give it some more thought and have another bash at it. There is already a glimmer of thought of one way to achieve what is required but...... I'll leave that for a last ditch method.

All understood about the ballast on top of the ramp possibly fouling the uncouplers - maybe I'll need to give that some more thought and just colour the surrounding ballast to that of the ramp itself. I'll keep posting on progress - one way or the other.

Anyways, have a good Christmas - here's to you and your family (and also to other readers of this thread).

Cheers
Dave

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 Posted: Sat Dec 29th, 2018 10:40 am
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Dave C
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Update on the uncoupling ramps .....
 
Hmmm! Not overly good progress initially - but finally, there is success. After many attempts at getting the program to function correctly (worked ok in simulation mode) and having spent a fair amount of time trying to get the servos to operate on the bench I found they kept twitching whenever they're not operating. When each servo is called to raise the ramp, it works nice and smooth, taking around a second an a half to lift (nothing too fast or jerky), and then slowly drops down again after around 10 seconds. And then, while in 'doing nothing mode', they all just twitch every few seconds. And this is where I was having a problem - getting rid of the twitching. And I've had to break out my trusty old oscilloscope to see if I could figure out what was going on and causing the twitching - all to no avail. I could see the pulses ok and also whatever was causing the twitching - certainly not the servo(s) themselves. Nice to see the waveforms though! So it was all down to the software/my programming.
 
A question was asked on the relevant forum and a few suggestions came back to me, such as power rail and layout and decoupling (capacitors) and some programming hints - there's some commands there I've never come across before and in routines that do not use the - what might be considered - 'normal' servo commands.
 
A change I made, initially to try to be rid of the twitching, was to use a more substantial power supply rather than my trusty old (power limited) item built many, many years ago. Break out an old, redundant computer power supply. Now that should be able to provide enough power for the entire layout. Currently 12v, then a 7805 regulator to the chips and 5v to the servos - nice and totally separate supplies, and hopefully nice clean supplies.

But, thanks to those guys on the PICAXE forum who kindly offered code samples, I now have a working mechanism that can uncouple tension locks remotely. It still needs to be mounted onto the layout though, but I'm now able to make slight adjustments to the code to make it do what I need it to do; and without twitching! What's more, the same code - with a few minor changes - can now be adapted to operate and control other bits of kit still in the thought processes of my mind.

I should add that this uncoupler design is not entirely new. I have compiled it from a number of designs - Alan being one contributor on RMWEB some years ago and also an 'N' gauge design (author currently unknown, sorry) as well as a few other contributors to my research.

The following photos were taken using a spare length of track on a scrap piece of baseboard material.


Ramp in the lowered position.


Ramp in the raised position.


Under the baseboard before the servo gets fitted showing the activator tube and the guide nails.

Again for completeness, the servo is a Tower Pro (others are available) SG90 9g, the mount is an off-cut from a VHS tape case, the uncoupling ramp is likewise ex-VHS, the tube is a short length of flexible 3.5mm tube with the short link to the servo arm an off-cut of wire (from a resistor) and a pair of thin 25mm nails as guides. The ramp lays on the baseboard (sleepers cut away) and needs to be raised by around 9-10mm. The controlling chip is a PICAXE 18M2+ with a rotary selector switch (for 6 servos) and a push-button activator.

All I need now is to transfer the design (many times over) onto the layout in spaces where a mouse would have little headroom! That'll be 'fun' - or not, as the case may be!

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 Posted: Sat Jan 5th, 2019 09:05 pm
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Dave C
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That's the first (of many) uncoupling ramps finally installed, tested and working.
 
What a job that was! Talk about difficult, frustrating, and a pain in the right arm. Not easy fitting a servo on a bracket to the underside of the upper baseboard when there is only 85mm clearance between that and the tracks on the underneath board and the fitting is at near full arm's length away; not to mention you can't see what you're doing, such as putting in the bracket mounting screws (due to the logistics of where my head is located in relation to my arm and shoulder - head above the top board and arm under it) and the screws being at the back of the bracket and only visible in a mirror. Now, if I were a contortionist.....maybe with x-ray eyes....
 
So it was a case of curse and curse some more till I managed to get the bits fitted. And to think this is the first of possibly 12 (maybe more) ramps to fit. At least this was the worst of them all (I hope).
 
Only two small changes from that described in my last post, and that was for a stronger piece of linkage wire between the servo horn and the tube. I found, almost as expected I guess, the wire offcut used was too flimsy. This time I've used a length of 1mm copper wire (from some old twin&earth cable) - this provides a tight fit to the holes in the servo horn and is strong enough not to bend. Seems to do the job just fine. The other change being that the ramp lowers after 5 seconds; 10 seemed a little excessive (but that's trial and error programming).
 
No photo of the finished/fitted item at this time as it's not a million miles from the prototype posted previously (post #81) - a little longer, but that's all. It'll look better when I get some ballasting around it, maybe on top of it also, but at least it will be blended in to the surrounding trackwork. But I want to get some more ramps fitted before starting to do the ballasting. Hopefully, the next ramps will not be quite so awkward or take so long to fit.
 
 

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 Posted: Sat Jan 5th, 2019 09:24 pm
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Sol
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Dave C wrote:
What a job that was! Talk about difficult, frustrating, and a pain in the right arm. Not easy fitting a servo on a bracket to the underside of the upper baseboard when there is only 85mm clearance between that and the tracks on the underneath board and the fitting is at near full arm's length away; not to mention you can't see what you're doing, such as putting in the bracket mounting screws (due to the logistics of where my head is located in relation to my arm and shoulder - head above the top board and arm under it) and the screws being at the back of the bracket and only visible in a mirror. Now, if I were a contortionist.....maybe with x-ray eyes....
   

I understand those type of "modelling" problems Dave and the older we get  we seems to get less flexible in arm & head movements and the eyes don't want to see what we want them so see either.
But outside of that, looks the goods....



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 Posted: Sun Jan 20th, 2019 05:32 pm
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Dave C
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Thanks for the comments Sol. Apologies for the (very) late response, but it's good to know I'm not alone with these ageing problems - growing old ain't much fun; but on the positive side it does allow a fair degree of time to follow this wonderful hobby of ours (if you're lucky! - at least, that's the theory and that's the reason behind the gap between my last post and this - life got in the way.... again). I like to, via the forum, give my view on my layout, as to what I'm doing and how I'm getting along with it (or not), warts and all.
 
Having said that, we bravely battle on. One day the layout will be finished (if layouts are ever fully finished?).

Not been able to get much done over the past few weeks, but hoping to get back in there this next week to finish off the next few ramps and get them working.

Dave

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