Close Coupling Round-up

[Hod Carrier]

I hope the board will forgive me for duplicating a lot of information already posted, but as it's mostly been scattered across the board in various other topics I thought it would be a good idea to gather it all together in one place for ease of reference and discussion.

Other threads were this has been discussed are:

LMS Articulated Railcar 1938 - Development of the idea and application for an articulated train

My LEGO Renfe S-130 - Use for a Talgo design

I had been thinking for a while whether it might be possible to come up with a way to close couple LEGO trains in a way that looks more like real life. After spending a while fiddling around with some Technic parts I came up with the following arrangement that offered a possibility.

This design gives a floating pivot point that holds vehicles close in to each other on the straights while still permitting enough movement relative to each other to allow for bend and points/switches. The idea initially was to use this design for conventional bogie vehicles that would need this amount of movement and still centre correctly on the straights, although I am still to test this idea to see how it works in practice.

The first application of this idea was in an articulated railcar, but this presented the first problem. I wanted to isolate the rotation of the bogie from the movement of the cars, as would be the case for an articulated train in which neighbouring vehicles share a pivot point, but such a design would not centre itself automatically. The initial solution was to use an elastic band to pull the vehicles back into line, but this was not a very successful idea and actually caused a few more problems than it solved. What the idea needed was another adaptation.

The solution was to add an additional diagonal linkage across the car mounting points. This prevents the sideways motion of the linkages that is desirable for bogie vehicles but not on an articulated train. It's an awkward length and requires careful set-up and securing as it's important to get the length absolutely right in order that the cars centre correctly. Get the length wrong and you get an offset between the cars.

It turns out that this design also works well for Talgo trains as, in addition to providing close coupling between the cars, it also gives the axle steering effect needed to ensure reduced friction and prevent derailments you might otherwise get with a fixed axle.

Edited June 28, 2023 by Hod Carrier

[Darkkostas25]

Thank you for sharing this! Nice to use in future!
Off-topic, but did you make(put old rails on standard) and double-gauged rails? (for double usage(4 and 6 wide bogies) and reduce usage of rails for economy)?

[Toastie]

This is so ingenious. As simple as that, and it needs its own thread. It is a solution to so many attempts.

On 6/21/2023 at 1:42 PM, Hod Carrier said:

It's an awkward length and requires careful set-up and securing

Correct me please, if I am wrong: As this awkward cross axle on its own may "slip" away if not secured, the securing comes through the Technic pins/axles pointing upwards, i.e., the Technic pieces on the cars receiving these, right?

All the best,
Thorsten

[Selander]

Very nice post ! Thanks for sharing valuable technical information to the community!!

[Hod Carrier]

@Darkkostas25 @Toastie @Selander You're most welcome. I'm always happy to share.

13 hours ago, Toastie said:

Correct me please, if I am wrong: As this awkward cross axle on its own may "slip" away if not secured, the securing comes through the Technic pins/axles pointing upwards, i.e., the Technic pieces on the cars receiving these, right?

The pins/axles pointing upwards is the means of coupling cars together, so the weight of each car is transferred down through the mechanism to the bogie. This should hold everything together and prevent slippage running.

The awkward length is to do with the length of the axle that forms part of this linkage. It needs to be @ 3.5L in order to centre things correctly, but no such part exists. I opted to use a 3L axle instead and glued the pin holders to it to ensure adequate strength and to hold it at the right length, but I could have chosen instead to trim down a 4L axle to the right length.

[Hod Carrier]

Further to the issue of setting the length of the diagonal link, I have a quick design for a jig that would help to set the length correctly. 

[zephyr1934]

On 6/21/2023 at 7:42 AM, Hod Carrier said:

I hope the board will forgive me for duplicating a lot of information already posted, but as it's mostly been scattered across the board in various other topics I thought it would be a good idea to gather it all together in one place for ease of reference and discussion.

On the contrary, it is very helpful. Only one thought, if any of the other threads have greater depth on anything critical, maybe update the first post to include links to them (but only if they have additional helpful info)

 

[Man with a hat]

Very useful!