Focalplane

Western Thunderer
This evening I wired up the centre track on the traverser and drove a Minerva Pannier up and down both Platform 3 and the Release Road, moving the traverser by hand. There is too much slop using only one coupling pin so I am going to drill a second hole and add a second coupling pin. The beauty of the design (!) is that the bolts holding down the screw to the carriage table below can be finely tuned to give good alignment. I just have to drill the second hole in the Tufnol in the right place! Tomorrow seems like the best time to do this.

If this doesn't work it's back to the drawing board.

Edit to add photo:

IMG_0648.JPG
 
Last edited:

Focalplane

Western Thunderer
The Bachmann Brassworks Mark 1 coaches ride too high and something will have to be done about that. Also, the couplers are too long, perhaps they were designed to allow these coaches to go round 3ft curves? As a result, some work on the bogie height will be done and I am also going for MagClic couplers between all the coaches with standard couplers at the front and rear. This is going to be a semi-permanent rake and MagClic are perfect for the job - I already have them fitted between the B Set suburbans. The Bachmann buffers aren't sprung but the Magclic couplers are, so I should be OK without replacing the buffers.

Here is a photo showing the height problem compared to the tender buffer beam of the Jubilee and a Sidelines Period III Open First:

IMG_0647.JPG
 

Focalplane

Western Thunderer
Traverser Mechanics - It's Back to the Drawing Board

I am hoping the above statement is not too serious but the process needs some thought before I tackle a solution The sloppiness wasn't completely cured by installing a second coupling pin and I believe it must be improved upon. The problem may well lie in the small roller bearings that run on the 9 rails. They de-rail too easily. I may replace them with something simpler (i.e. not stick with the prototype design) but retain the nine rails as cosmetic fittings and use a more robust "rolling road" hidden from view.

So, what to do while thinking? There are plenty of other priorities to be tackled.

On that subject, my back ordered DCC Concepts point levers "arrived" yesterday, except the contents in the box were not what I ordered! A quick call to the vendor and the point levers will be mailed out on Monday while I promised to return the point motors I neither want nor need.

So this weekend has been something of a disappointment.

C'est la vie!
 

Focalplane

Western Thunderer
So, back to the Bachmann Brassworks coach height problem. I took one bogie apart and also unscrewed the buffer beam.

IMG_0654.JPG

The good news is that the buffers are indeed sprung, the painter just made sure they didn't spring! The not so good news is that the bogie height isn't easily adjusted. I didn't go any further in dismantling the body and I am not sure it would help anyway. The bogie height is formed by the threaded boss on the body sitting in a cup on the bogie with a spring to allow some movement. Do I remove some of the threaded boss? Or should I forget there is a height discrepancy? That latter suggestion is sure to arouse indignation from true Western Thunderers!
 

Focalplane

Western Thunderer
I also pushed the rake backwards and most of the couplers came undone, mainly due to being stiff from the painter’s work. I can rectify this but in fact the couplers will go, to be replaced by MagClics. Measurement by eye suggests that the MagClics will provide the right spacing between coaches, under tension or compression, and the need for some additional corridor connector material will be minimal.

If you are unaware of the MagClic device, there is one fitted to the Sidelines Period III coach in post #222. The drawbar pull can be at least 7 coaches.
 

Brian McKenzie

Western Thunderer
Use of a second linear drive unit, with the units placed at the ends of your traverser should fix the problem. The drive screws would need to rotate identically, so a chain drive or similar might need to be cobbled to connect the two (in the absence of any stepper motor type control).

This reliability of drive issue is very common with those who assemble inexpensive CNC controlled hobby type routers, often made from aluminium extrusions. This chap rab3D - CNC Router shows photos of a pair of drives for the X axis of his machine (he says to provide extra power), but others do it to achieve reliable tracking of the moving parts.

Great job on Moor Street by the way :thumbs:
 

Focalplane

Western Thunderer
Use of a second linear drive unit, with the units placed at the ends of your traverser should fix the problem. The drive screws would need to rotate identically, so a chain drive or similar might need to be cobbled to connect the two (in the absence of any stepper motor type control).

This reliability of drive issue is very common with those who assemble inexpensive CNC controlled hobby type routers, often made from aluminium extrusions. This chap rab3D - CNC Router shows photos of a pair of drives for the X axis of his machine (he says to provide extra power), but others do it to achieve reliable tracking of the moving parts.

Great job on Moor Street by the way :thumbs:
Many thanks for this, Brian. I am working on a simpler solution at the moment but it still may not be satisfactory. The linear drive units I bought should be more than adequate for the job, it’s not the mechanical connection to the surface traverser design that is the problem. The prototypical design is proving to be the weak link so that is what I will address first. The link you provided makes for interesting reading - we live and learn!
 

3 LINK

Western Thunderer
Evening Paul,
In my opinion I would want to sit the coach body's lower, not only to correct the buffer height , I just think they look better. I had the same problem with a couple of B set coaches I built, so much so that when I tried to lower the bodies the wheel flanges were rubbing on the underneath of the floor . In the end I actually cut away some of the floor to correct the height problem, out of sight out of mind :cool:.

Martyn.
 

Focalplane

Western Thunderer
Martyn

You are right, it’s not the buffer height alone, it’s the entire coach, with a significant air gap between body and bogies. At the moment I am concerned with the amount of butchery that may be required.

Paul
 

Focalplane

Western Thunderer
Four photos to show the poor coupling design and how MagClic can change the gaps.

First, under tension on the straight:

06877DA7-0927-4A0C-B140-CB36CF88D51C.jpeg

Next, under tension on a 6ft approx curve:

A6C5EBD3-170D-404E-8856-A33E8D1E98E5.jpeg

Next, closed up on the straight:

6F5A1220-835D-4983-8C46-03ECA84B6268.jpeg

And finally, closed up on a 6ft radius approx curve:

AD6EC01E-4EA8-4169-ADDC-FADE7D9C8184.jpeg

In none of the cases are the sprung buffers involved. So, In theory the amount of additional material needed to create proper corridor connections is actually minimal. MagClic couplers will permanently hold the coaches as close together as photos 3 and 4.
 

3 LINK

Western Thunderer
I think the coaches look great, so the relatively quick fix with the MagClic would be well worth the effort, and being able to lower the bodies would be the icing on the cake.

Martyn.
 

Yorkshire Dave

Western Thunderer
Do I remove some of the threaded boss? Or should I forget there is a height discrepancy?

I'm of the same opinion as Martyn, I would be looking to lower the ride height.

Rather than attempt to remove material from the threaded boss is it possible to deepen the cup on the bogie?

Or drill all the way through and use washers or brass tube?
 

simond

Western Thunderer
Ride height, needs fixing. I like the idea of reducing the cup height on the bogies but it’s not clear how the cup and the boss on the coach underframe interact. It’s a few years since I had one in bits. Would that actually fix the issue?

Magna clicks? I’d go with Kadees. They’re not handed, but that might not matter.

Atb
Simon
 

Peter Cross

Western Thunderer
With this traverser, would peg or two with a slot and a spring on them to pull the traverse down onto the rails help. I know this will make the whole thing stiffer but would solve guidance and derailing.
 

Focalplane

Western Thunderer
It shouldn't be surprising that, because of the time zones I always seem to wake up to several new posts and all the above are most useful. While waiting for the coffee to brew, here are some comments.

MagClic couplers are indeed handed which means that a coach cannot be turned around without turning round all the others in the rake As the set will be kept as a set, Simon is right that it might not matter. I have had lots of experience with Kadees in 4mm scale and 3.5mm scale since they were first on the market and now avoid them if I can as custom fitting can be a nightmare (many of my HO locos were made prior to Kadee being invented).

Dave's suggestion of modifying the bogies (all 14 of them) makes a lot of sense and I need to take another look at the arrangement. Leaving the threaded brass boss untouched would be a good idea.

Switching to the traverser, Peter's idea is similar to my next approach, still using the ball bearings but with extra weight and guides under the traverser table to hold them in place. The traverser actually runs better when a locomotive is on it, hence the need for more weight for when it is moving without a load. The diameter of the brass rod they run on is also o.1 mm too thin (it is 2.9mm, not exactly metric as it was advertised at 3mm) so replacing the rod would help but that would require a complete strip down. I might bite the bullet and do this if I can source real 3mm rod locally. But the day is young and I need that mug of coffee. . . .
 
Last edited:

simond

Western Thunderer
Just having that coffee before heading to the office...

In the current design, the traverser table itself needs to do six things reliably.

It must move through the full travel in (let’s call it) X without deviation, hesitation, etc.
It must stay aligned in Y (track axis)
It must support the weight in Z.

It mustn’t Roll, Pitch or Yaw either, indeed, the guidance system must prevent Yaw, and both guide rail top and wheels should be flat and level, so roll and pitch are irrelevant.

The drive system, including the connection between the quite rigidly-guided carriage & the traverser table needs to do rather fewer things.

Travel through the full X range without deviation...
Not apply any loads in Y
Not apply any moments in Roll, Pitch or Yaw

Downwards Z loads may be acceptable. You could have a “pull-down” spring.

A single rigid post, fixed to the carriage of the drive unit, which engages in a socket (ideally a ball-joint) in the middle of the table, at guiderail top height will minimise or prevent the transmission or creation of moments at the table.

Note that a similar post pointing down from the table to meet the drive system will create a lever arm, and therefore will create a moment that will tend to lift the table off its rails.

To avoid applying any loads in Y, you can consider hinging the post, or making the socket in the traverser table into a slot.

The alternative approach is to rigidly fix the traverser table to the carriage of the drive system. In this case, the model traverser guide rails will be there for show, but will play no part in guiding or supporting the table. I’d take any wheels you can’t see off, and make any wheels you can see sufficiently flexible (sliding on their axles) so they can not provide any guidance at all - just go “along for the ride”.

You’ll then need to arrange a means of adjusting the supports for your drive system so that you can easily adjust the alignment in Y, Z and Yaw. Either screw thread & locknuts, or clamps with shims underneath.

Either approach should work fine. I suspect that the rigid approach might, eventually, prove the easier, and you’ll need it for the lift, so I would tend to go that way.

Have a great day y’all
Simon
 

Focalplane

Western Thunderer
I am on my second coffee of the day having just been paddle boarding (retirement is good, y’all) and have just read Simond’s previous post (236). Luckily I have worked with petroleum engineers all my career life so I do understand the technical stuff. Geologists hit things with an Estwing hammer and usually break rocks in the process, we are not known for our finesse!

Well, Simon, I think it’s back to the drawing board with serious intent to get it right. I’ll turn your post into a check list and hang it over my workbench. Thank you!

With family arriving in early July I want to finish the wiring and that will include the point motors when I receive the correct order of levers. But the traverser remains a priority for thought and design, that I promise. Moor Street would not be Moor Street without them.
 

Focalplane

Western Thunderer
Back to the Bachmann Brassworks coaches. Replacing the couplings isn't going to be so straightforward as I had hoped, first I can't remove the existing couplers because the springing is soldered, second the hole in the buffer beam is circular. So, we'll delay that one.

Next the bogie height adjustment. Having done some fiddling around I have come to the conclusion that the bogies have springing which has been soldered tight (by Bachmann?) and painted over. To demonstrate this I took some photos after unsoldering the springing:

First, no weight on the bogie, check the gap between bogie and body:

IMG_0661.JPG

Next, with the coach body's weight:

IMG_0662.JPG

Some improvement, but with my hand pushing down on the coach:

IMG_0663.JPG

This position starts to look good, particularly when the Sidelines coach is end to end:

IMG_0664.JPG

I could solder up the springing in a compressed position but that seems to be a bit drastic.
 

Focalplane

Western Thunderer
Visited Leroy Merlin today and bought a few bits of material. No exact 3mm diameter brass rod, though. Steel bar is going to be tried to constrain the traverser wheels, keep them aligned and also weight the traverser platform down. And I got some platform wall timber as well at a very good price. Adding the platform walls will be a low-tech solution to adding some "feel" to the layout before the grandchildren arrive. If the traverser re-design works I will have one installed for hand-of-god movement and wait until September to expand on the electronics, etc. The kids won't notice the ride height of the coaches, so they can stay as they are. It's now up to the delivery of the point levers for real progress to be made. I sent the "wrong items" back this morning, their weight meant a 15.20 euro postage for which I expect a full credit. I hope the poor soul who made the packing mistake gets an ear full, it's the best way for him/her to learn.
 
Top