Bachmann coaches - close coupling system

[fungus]

 

mick said:

Is the plastic pipe section that you have attached the magnet and heat shrink to, the original pipe coupling that is included in the box as an alternative to the standard tension lock? I assume if it is that you have cut it in half before attaching the magnets? This then gives you the close coupling qualities of the alternative pipe coupling, retains the ability to negotiate sharper curves, and an easier means of coupling/uncoupling?

You're exactly right, Mick. It's the original plastic pipes from the box, with 4mm removed from the middle to allow for two 2mm long magnets. I have also made some now using other material for the pipes, but that's another story!

I am also making a pair of couplings as an experiment, using two smaller magnets with opposite poles outward, one on each pipe. If it works, it will have the advantage that the couplings on all vehicles will be identical, and both ends of the vehicles will be identical, so vehicles can be turned around and moved without changing the couplings. I'll report on this when I've tested it.

[fungus]

 

ba14eagle said:

Crikey Scientific overload

By the way, Iain, I was trained as a scientist and had a long career as an engineer, so you are quite correct, but I'm afraid that the scientists' way of working is ingrained in me! In fact, solving probems to eventually achieve an objective is what keeps me interested in the hobby.

[fungus]

 

ba14eagle said:

I'm lucky enough to be one of those "perfectionists" who marshall their coaching stock rakes in the same way each session - they are even put the correct way around in the stock tray, so others can put them on, the right way around, every time .

Yes, I've just done the same thing while I've been making up my "magnetic couplings test train" (photos will be taken and report written!) ready for the next warm, dry day with no other commitments. My indoor layout is only 5' long, so a train of 12+ coaches has to be assembled and checked a few coaches at a time.

[fungus]

I've tested a pair of double-magnet couplings (which we'll call Mk.2, the single-magnet version being Mk.1), and they were still holding strongly at 190g! That's amost twice what my strongest loco can pull before the wheels start to slip. (Note that 190g is the horizontal force in line with the loco, or the weight it could lift or support using a horizontal cord running over a pulley. It is not the total weight of the train it could pull, which is much greater.) I'll post a full report when I have some pictures.

The advantages of this design over the single-magnet (Mk.1) version are:

- All couplings are identical and interchangeable

- Smaller magnets - looks neater in side view

I have also devised a simple production method which automatically holds the pairs of magnets in exactly the right orientation for assembly, without the need for any special jigs. Again, a report will follow when I have some pictures.

Further developments? Well, a better design is still needed for fitting to locos. And it's possible that an even smaller magnet would still give enough strength for our purposes. Watch this space!

Edited November 30, 2012 by Guest

[ba14eagle]

What have I started

Sounds like youve got yourself a nice little cottage business here - I will order enough for 20 coaches please

[fungus]

 

ba14eagle said:

What have I started

Sounds like youve got yourself a nice little cottage business here - I will order enough for 20 coaches please

Very labour-intensive; I don't think you'd like the price! Once the design is proven however, perhaps I should hand it over to a production team, who would probably get it made in China for tuppence.

[fungus]

I spent a couple of hours today, despite the freezing weather, preparing a length of garden track and running a 12-coach test train round the reverse curves on a 1 in 50 gradient. This was the first fully "live" trial of the "DOGRF* Magnetic Coupling".

[fungus]

IMPORTANT NOTES

One of the best ways to kill a good idea is to not define stadards early on, so that everyone does it slightly differently, and no two systems can work together. Examples include VHS & Betamax, mobile phone chargers, and many more. There is one critical parameter of the DOGRF Mk.2 coupling that I haven't yet defined and will now attempt to do so. For two couplings to mate correctly, they must both have their N and S poles in the same orientation, so that on mating, N attracts S and S attracts N. Having made about a dozen of these couplings now to an arbitrary standard, I have measured which are the N and S poles and will define this as THE DOGRF Mk.2 magnetic coupling standard. In that way, any couplings you make will work with anyone else's, and vice versa.

The tools you need are an ordinary magnetic compass (and no, a GPS receiver won't work unless it includes a nagnetic compass), and a bar magnet (one of the magnets you are using for the coupling will do). Glue your magnet to the end of a non-magnetic stick with the line between N and S in line with the stick. (If you are using the same magnets I did, then one of the two flat faces is glued to the stick.)

Point the magnet end of the stick at the compass, and move it all the way round the compass. If the red (N) end of the compass needle points to your stick, then we will say that your stick ends in a N pole. If the red (N) end of the compass needle points away from your stick, then your stick ends in a S pole. Mark your stick with either S or N at the magnet end, and the opposite at the other end. You can now use the magnet end of your stick to check the polarity of any coupling or magnet, bearing in mind that N and S are attracted, and N and N or S and S are repelled. Couplings can also be checked by ensuring they mate correctly with a known good one. A known good one can also be used to hold a new pair of magnets in position while they are glued to their "pipes". I will try to add some photos to make this clearer.

And which way round should the coupling magnets be? When looking at the end of a vehicle on the rails with a coupling fitted, the mating face of the right-hand coupling magnet should have its N pole toward you.

Finally, a VERY IMPORTANT SAFETY WARNING. If you bought your magnets from a reputable dealed, you will have been given some dire warnings. It is worth reiterating that these tiny magnets can cause life-threatening injuries if accidentally swallowed. So keep them in their original packaging until assembled, and don't leave them laying on the work bench. And don't fit them to anything that could be used by children. If you pass them to anyone else, also pass on the warnings too. It's all common sense really, but so easy to forget, with potentially serious consequences.

[chris]

Whee IanR came over to visit Amblethopre we talked through this close coupling system and we agreed that it was a good idea, Ian had even bought some magnets, but done nothing with them.

We chatted about the pro's and con's of having 1 or having 2 magnets in the coupling and being a DCC man I brought up another aspect, could an uncoupling system work with magnets.

If a loco had an electro magnet on the rear, (there would probably be more room in a steam loco's tender) then a DCC function could be assigned to it and could power the electro magnet. A small Capacitor Discharge Unit may be required to give it enough ummph. The repulsion force of the electro magnet and the permeant magnet may be strong enough to separate, especially if the loco was moving away.

Just a thought that I've done nothing about.

[fungus]

 

chris said:

If a loco had an electro magnet on the rear, (there would probably be more room in a steam loco's tender) then a DCC function could be assigned to it and could power the electro magnet. A small Capacitor Discharge Unit may be required to give it enough ummph. The repulsion force of the electro magnet and the permeant magnet may be strong enough to separate, especially if the loco was moving away.

Perhaps all that would be needed would be to reverse the current through the coil of the electromagnet. I'd need to find some of my old physics text-books before saying any more!

[chris]

Old physics books? Haven't you heard that we have the Internet these days Actually, a well structured book beats the Internet more often than not.

I was thinking that the electro magnet would be switched off most of the time, with only the permanent magnet on the coach creating the force. The electro magnet would receive a pulse of current when an uncoupling was required. This would reduce current draw from the track, and also allow for a CDU if the 500mAmp from the function of the decoder wasn't enough.

[Clay Mills Junction]

Just found this, six years before Hunt couplings made a commercial version.

[ba14eagle]

On 08/03/2022 at 20:15, Clay Mills Junction said:

Just found this, six years before Hunt couplings made a commercial version.

I know - it was quite annoying when people were waxing lyrical about a "game changing" innovation 😂 I have actually bought a pack or 2 of Hunt couplings and, tbh, they arent very good - they break too easily, which for a commercial product sucks. At least when mine break, I only have my own shoddy handiwork to blame and am able to repair them - you cant do that to a Hunt coupling! I have to concede defeat though, when they have produced ones that dont have to be correctly arranged, pole to pole. I have also used the ones that fit the older Hornby mk3's.