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Author Topic: New coupler development (was Coupling survey)  (Read 27717 times)

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Offline belstone

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Re: Coupling survey
« Reply #60 on: June 15, 2014, 08:09:17 pm »
My wife thinks I am obsessed with couplings. She is probably right. Anyway, at the end of a day of fiddling around with various materials, and rather to my surprise, I have two working prototypes fitted to short wheelbase wagons - one NEM, the other T-shank. Obviously I'm not going to go into design details at this stage, but features include hands off uncoupling and delayed uncoupling, also vehicles can be easily uncoupled from each other by hand and removed from the track. They use ordinary bar magnets either flush with the sleepers or buried in the track bed. Coupling force is minimal, and with these rather crude prototypes (which have an awful lot wrong with them in constructional terms) I'm getting about 90% reliability in coupling, uncoupling and delayed uncoupling. And they don't show any tendency to self-uncouple when drawn over the magnets. There's plenty of clearance under the bufferbeam so they should be fine on tight curves.

However, there are a few issues, and I would be interested to know what people think about the following:

1. They are fairly height-sensitive, which means the shanks have to be mounted rigidly in the pockets with no vertical movement.  I think NEM pockets should be OK provided the shank dimensions are correct, the pocket is fitted at the right height (ha ha) and there's no slop between the pocket and its mounting, but the T-shank version will almost certainly need to be glued in, which means the conversion isn't easily reversible. I suppose it depends what glue you use. I might be able to tweak the design so they cope with larger height differences, but the shank really needs to be rigid in the vertical plane for them to couple reliably.

2. Distance between the vehicles is about the same as Rapidos, and there isn't a lot of scope to shorten it due to the design.  So you aren't going to get the kind of prototypical close coupling that can be achieved with short-shank knuckle couplers.

3. In an ideal world I would have the components injection-moulded in a suitable plastic, but tooling costs rule that out straight away.  I don't think the shape and size will lend itself to 3D printing although I don't really know just what is possible with that technology.  So we are probably looking at a kit, including cast whitemetal and etched parts, which will require two or three very small holes drilling in the right places (dimples in the castings to mark the positions) and steel wire bending accurately to shape, probably with a bending jig included in the etched component fret.  I would reckon between 2 and 3 a pair, and 10 minutes per coupling to assemble once you've done the first couple.

4. Long shank variants are problematic.  It is easy enough to cater for standard length Rapidos (NEM or T shank) which probably cover 90% of applications.  But I know there are some oddball Rapido variants out there, and the one that this design definitely won't work with is the extra-long T-shank in a fixed pocket which I have seen occasionally on long wheelbase wagons with long end overhangs (1970s Minitrix German stuff, mainly). Swivelling pockets (like the Farish horsebox) are fine provided there's no vertical slop in the mechanism. I'd be interested to know of other long-shank couplings, especially on current or recent production stock.

I can't quite believe I've come up with something that works, especially as it is so simple in concept. There must be a catch - maybe someone has already patented the design I have in mind. If they haven't, I think I might.

Offline johnlambert

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Re: Coupling survey
« Reply #61 on: June 15, 2014, 08:52:54 pm »
Sounds very promising.  Are you going to get some other people to test your design?

Looking forward to hearing how other people get on with it, or any other news you have.

Offline belstone

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Re: Coupling survey
« Reply #62 on: June 15, 2014, 08:59:25 pm »
Sounds very promising.  Are you going to get some other people to test your design?

Looking forward to hearing how other people get on with it, or any other news you have.

Early days yet, and I'm trying to work out how to take this forward. I think the next stage is to get a test etch done (I'm fed up with filing hooks out of brass sheet), make up some fully functional prototypes from brass and fit them to a dozen assorted wagons. Build a small shunting layout including Setrack points, sharp reverse curves and maybe an incline with really fearsome gradient changes. And if they cope with all that, I might think I'm onto something.

Offline johnlambert

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Re: Coupling survey
« Reply #63 on: June 15, 2014, 09:54:36 pm »
Sounds like a good plan!

Offline Caz

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Re: Coupling survey
« Reply #64 on: June 15, 2014, 09:57:34 pm »
Looking forward to hearing more, sounds very interesting.  One question, will they be exactly the same coupling on both end of the wagon or be handed as that is why I gave up with the like of MBM and B&B's etc.

Offline belstone

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Re: Coupling survey
« Reply #65 on: June 15, 2014, 10:07:45 pm »
Looking forward to hearing more, sounds very interesting.  One question, will they be exactly the same coupling on both end of the wagon or be handed as that is why I gave up with the like of MBM and B&B's etc.

Same on both ends. I wouldn't accept a coupling that only worked one way round.

Online Bealman

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Re: Coupling survey
« Reply #66 on: June 16, 2014, 07:40:46 am »
This is indeed most interesting. I wish you every success with the project! Good luck with your testing programme, which sounds pretty thorough to me!  :thumbsup:
Vision over visibility. Bono, U2.

Offline Karhedron

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Re: Coupling survey
« Reply #67 on: June 16, 2014, 09:49:57 am »
Whilst I am generally happy with Dapol Easi-shunts, I appreciate they are not a perfect solution so I will be wating this thread with interst. Well done for having the motivation to tackle a tricky subject.  :thankyousign:

1. They are fairly height-sensitive, which means the shanks have to be mounted rigidly in the pockets with no vertical movement.  I think NEM pockets should be OK provided the shank dimensions are correct, the pocket is fitted at the right height (ha ha) and there's no slop between the pocket and its mounting, but the T-shank version will almost certainly need to be glued in, which means the conversion isn't easily reversible. I suppose it depends what glue you use. I might be able to tweak the design so they cope with larger height differences, but the shank really needs to be rigid in the vertical plane for them to couple reliably.
In this regard they have the same restriction as the Dapol couplers. One simple solution would be to fit the stock with NEM pockets. That way the Rapidos can be reinstated if necessary.

2. Distance between the vehicles is about the same as Rapidos, and there isn't a lot of scope to shorten it due to the design.  So you aren't going to get the kind of prototypical close coupling that can be achieved with short-shank knuckle couplers.
It depends where it is used. If you just have them fitted to locos and the ends of a rake, this is not really a problem. You can still use short-shank knuckles within the rake to keep it closely coupled.

3. In an ideal world I would have the components injection-moulded in a suitable plastic, but tooling costs rule that out straight away.  I don't think the shape and size will lend itself to 3D printing although I don't really know just what is possible with that technology.  So we are probably looking at a kit, including cast whitemetal and etched parts, which will require two or three very small holes drilling in the right places (dimples in the castings to mark the positions) and steel wire bending accurately to shape, probably with a bending jig included in the etched component fret.  I would reckon between 2 and 3 a pair, and 10 minutes per coupling to assemble once you've done the first couple.
People have printed rapido and NEM couplings quite successfully on Shapeways although without knowing what your coupling looks like, I do not know if it would work. Also you would need to work up the designs in 3D with a CAD package. Obviously I would prefer a ready made solution because I am lazy. ;) But I would certainly not rule out a kit if the design is a good one.

4. Long shank variants are problematic.  It is easy enough to cater for standard length Rapidos (NEM or T shank) which probably cover 90% of applications.  But I know there are some oddball Rapido variants out there, and the one that this design definitely won't work with is the extra-long T-shank in a fixed pocket which I have seen occasionally on long wheelbase wagons with long end overhangs (1970s Minitrix German stuff, mainly). Swivelling pockets (like the Farish horsebox) are fine provided there's no vertical slop in the mechanism. I'd be interested to know of other long-shank couplings, especially on current or recent production stock.
I am inclined to think that a solution which is good for 90% of stock is good enough. For people who have unusual items in their collection, they could modify them or use a translator vehicle with your enw couplings at one end and a regular rapido at the other.
Well, that's just not good enough. Some fount of all knowledge you are!  :no:  ;)

Offline SmileyFace

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Re: Coupling survey
« Reply #68 on: June 16, 2014, 10:56:29 am »
You're to be commended, Belstone, as your ideas sound very intriguing. N-gauge couplings have always been a weak area although Dapol's easi-shunts were a step in the right direction but not without problems. I'll watch your developments with keen interest.

Having undertaken many one-off mods in the past to enable the fitment of Microtrains couplings to a wide range of British stock I have no problems with a kit /unassembled approach.

p.s. I've still not done that mod I promised you feedback on using MT1131 pockets - sorry, I will get round to it if it's still of interest to you.
SF

Offline belstone

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Re: Coupling survey
« Reply #69 on: June 16, 2014, 11:12:13 am »
After a bit more thought I'm now leaning towards offering this (if the tests are successful) as a kit with simple fold up etches, square plastic strip for the shank, fold and glue assembly. Only one hole to drill and the etch will give the exact position. The etch design will include a couple of assembly jigs for the tricky bits.  This approach has a couple of advantages: the shank length can be customised for non-standard applications, one kit will cover NEM and T shank, and if I don't use castings or mouldings it will be very, very cheap - possibly down to the magic 1 per pair, sold in a kit of 10 pairs. The way I plan to do this, assembly should be well within the abilities of anyone who can put together a simple plastic kit. Tools required - minidrill and appropriate sized bit, sharp knife, razor saw, wire cutters, needle nose pliers, paint, Superglue and Mek-Pak.  I reckon most modellers should have those already.

I also have in mind a starter kit including a pair of ready assembled and tested (but unpainted) NEM shank couplings, some uncoupling magnets, plus the standard kit. That would probably sell for around 20. Any comments?

Karhedron - thanks very much for your input. Having looked a bit more into 3D printing I don't think it will work as the hook dimensions are absolutely critical - there's some tricky geometry at work here.  I don't think I'll get the strength and accuracy I need with 3D, but I reserve the right to change my mind on that one.

SF - I think the J39 was a one-off. It looks to me as though Farish designed it for T-shanks, then decided to change to NEM pockets after the chassis tooling had been signed off.  Hence that strange little rotating tumbler inside the pocket which I haven't seen on any other NEM equipped loco. You certainly can't convert a 2MT the same way I did the J39.

Offline MikeDunn

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Re: Coupling survey
« Reply #70 on: June 16, 2014, 11:14:38 am »
You mentioned some assembly jigs - would they be in each pack, or in the starter pack / sold separately ?

Offline belstone

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Re: Coupling survey
« Reply #71 on: June 16, 2014, 11:26:10 am »
You mentioned some assembly jigs - would they be in each pack, or in the starter pack / sold separately ?

I plan to include them within the etch. They are pretty simple things.

Offline Howlin`baz

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Re: Coupling survey
« Reply #72 on: June 16, 2014, 11:48:05 am »
One area which I am sure is a concern to most N Gaugers is the unexpected uncoupling.   While you are correct to say that coupling pockets "should be" at the same hight, they are often not.   I am operating a post privitisation stysem using mostly block trains (like manu others who have responded).
It seems to me that there is almost a bigger demand for a bar type coupling to avoid most of the problems.    it would need to be based on a two-part bar with perhaps a ball and socket arrangement in the middle, but NEM fixings at the ends.   Perhaps this would be a good project for 3D printing?

Offline SmileyFace

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Re: Coupling survey
« Reply #73 on: June 16, 2014, 12:03:18 pm »
SF - I think the J39 was a one-off. It looks to me as though Farish designed it for T-shanks, then decided to change to NEM pockets after the chassis tooling had been signed off.  Hence that strange little rotating tumbler inside the pocket which I haven't seen on any other NEM equipped loco. You certainly can't convert a 2MT the same way I did the J39.
Ahh that explains it! Actually I've now had a go at that mod and it works perfectly- thanks for the idea. Took 10mins and was tricky to hold the sprung shank in place whilst gluing the cut down MT1131 pocket to the NEM pocket in order to retain the shank. However, it sounds like you've moved on considerably since then. All sounds very exciting!

Offline Karhedron

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Re: Coupling survey
« Reply #74 on: June 16, 2014, 12:06:28 pm »
It seems to me that there is almost a bigger demand for a bar type coupling to avoid most of the problems.    it would need to be based on a two-part bar with perhaps a ball and socket arrangement in the middle, but NEM fixings at the ends.   Perhaps this would be a good project for 3D printing?

Something like this perhaps? ;)

http://www.shapeways.com/model/656500/n-scale-nem-fixed-bar-couplings-3-5-5-7mm.html?li=search-results&materialId=25
Well, that's just not good enough. Some fount of all knowledge you are!  :no:  ;)

 

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