Bogie Design

[alandoyle]

I have recently been building my first tracks and fitting w irons to wagons. I now need to move on and build my first coach bogies for my 21mm gauge Irish stock.With axles 28mm long instead of 26mm, I cannot just adapt rtr bogies. I need to either adapt a P4 commercial product or build my own from scratch.

The Brassmasters / Jim Smith Wright design seems quite straightforward to convert, simply building a central filler that is 2mm wider than the one supplied, though I have reservations about how easy it will be to make that filler accurately. The Bill Bedford design seems very good, but unconvertible: I would need to build a completely new bogie on the same lines. The same seems to apply to the Exactoscale ones. I don't know what other designs are available.

I've read what I could find on this forum, and a reasonable amount of the articles on CSBs for locos, but I'm still some way from taking the plunge and trying to build something.

I have a number of questions:

1. What other bogie designs are out there, either commercial or home made?

2. Can anyone supply drawings or photos showing the parts required for different systems and how they fit together?

3. What experiences have people had of different systems? What works and what doesn't? What's relatively easy and what's horribly difficult?

Ideally, I'd like to work out a short list of techniques to try, and see what works for me. If anyone has any information or views on the above, I'd be very grateful.

Thanks,


Alan

[allanferguson]

The late Mike Gilgannon was a very highly respected modeller, and his stock looked and ran beautifully. After his death I aquired some of his bits and pieces, including some cast whitemetal Caledonian bogie sides. (We have had these available in the past). The original intention was to construct them as solid, with a cast whitemetal centre, and the problem was that attaching them outside an etched brass unit gave a bogie which was too wide overall. Mike's solution was as shown, giving a bogie of correct width, with all wheels sprung. (None of your primary and secondary springing, mind you!) I haven't yet tried it out myself, but it looks like a good idea, and as said, Mike's stock ran beautifully.

Allan F

Gilgannon Sprung Bogie.jpg

[Russ Elliott]

I thought the Brassmasters CCUs were a good design when I played with them at Scaleforum - an 'improved MJT'. If you wanted a lot, it would be only a quick change of artwork to accomodate the extra 2mm width on a custom etch.

If you're feeling a bit more DIY, Peter Denny adopted an internal bearing solution in 1960 for his wide gauge - it's the original 4mm sprung bogie (he held the bearing plates in a little wooden jig when soldering on the bits of spring):

peter-denny-sprung-bogie.png

[alandoyle]

Thanks for those replies.

Allan, I'm a little puzzled by the Caledonian design. I can see the springs but am not clear whether the design uses pinpoint axles in brass bearings, with the spring on the bearings, or if there was some sort of horn block where the white metal has been narrowed down.

Russ, that Peter Denny design rings a bell: I must have seen it somewhere in my pre P4 past. At the moment, it certainly seems that the Brassmasters route may be the easiest path so the first one to try.

Thank you both.

Alan

[allanferguson]

Alan

These bogie castings are very good representations of the CR bogie sides, and were supplied with cross beams and bolsters, the whole intended to be glued or soldered together as a solid unit. To attach it outside any of the etched frames available meant losing all the cast bolster detail, which is quite conspicuous on this bogie. So there was a desire to spring or compensate the bogie somehow, and I struggled for some time to get a workable compensation design (we didn't think of springs in those days!). I don't know how Mike meant to work this, but I deduce it was something like this -- a pin point bearing soldered into a wee backing plate. I've folded over the top to leave a wee ledge for the spring. I certainly intend to do them like this when I get round to them. Other ways will no doubt suggest themselves to the fertile imagination. Incidentally the spring appears to be 10 thou material, and is soldered to the top of the casting -- not a CSB!

Allan F

DSCF0075.JPG

[Guy Rixon]

If you're feeling a bit more DIY, Peter Denny adopted an internal bearing solution in 1960 for his wide gauge - it's the original 4mm sprung bogie (he held the bearing plates in a little wooden jig when soldering on the bits of spring)

Do you know if the bearing plates ran in guides or whether they moved in an arc on the end of the springs? I'm trying hornblock-less springing for a coach at present and prior art is always helpful.

[Will L]

Do you know if the bearing plates ran in guides or whether they moved in an arc on the end of the springs? I'm trying hornblock-less springing for a coach at present and prior art is always helpful.

As I remember it they moved in an arc, and were pretty stiff with it.

Will

[Guy Rixon]

I tried a variant of the Denny springing, but for a four-wheeled coach. I used 0.315mm phospher-bronze wire for the springs, and the axle bearings were the Exactoscale kind set into a brass tube (2mm OD, 1.5mm ID). The springs are just soldered to the tube. The spring support is a hoop of brass wire.

20130711_165928.jpg

20130711_165817.jpg

In the test unit I made last night, the free length of the spring between the tube and the hoop is 7mm and I get 0.5mm deflection for a load of 13g on one wheel, which is at the low end of the likely range of weights. This is about half the deflection seen in a wire of the same length without the tube and hoop.

[billbedford]

Where will the grease nipple go on that tube?

[Guy Rixon]

Where will the grease nipple go on that tube?

Would you use grease? I was going to oil it.

[billbedford]

I wouldn't have used a tube at all, but if you insist on using one a piece of 1.5mm ID tube with exactoscale bearings in each end would be mechanically much sounder.

[grovenor-2685]

Bill,
This is the original description of the tube!

and the axle bearings were the Exactoscale kind set into a brass tube (2mm OD, 1.5mm ID).

Keith

[Guy Rixon]

I wouldn't have used a tube at all, but if you insist on using one a piece of 1.5mm ID tube with exactoscale bearings in each end would be mechanically much sounder.

Quite.

The idea of the tube is that the bearings are kept in good alignment so the friction is lower. This may or may not work and I don't know a good way of measuring it (other than building two trains identical other than their bearings). I would not care so much about the alignment if they were pinpoint bearings.

I wouldn't normally use inside bearings at all for coaches; I'd use your springing etches with outside pinpoints, which would be quicker, easier and have lower friction. However, this is a special case in that the axleguards are outside the solebars and are way more than 26mm apart. The axleguards are also etched as part of the solebars and are nothing like anything in the Bedford range (actually the NLR kind). If I had adapted the kit's axleguards to use Bedford spring carriers, then I'd have needed custom, pinpoint axles which I have no way to turn accurately. Therefore, inside bearings.

One other approach that I considered was to mount Bedford axleguards inside the wheels, and to solder the bearing tube into the Bedford spring-carriers. But this would require the spring carriers to tilt with the suspension movement and I suspect that things might lock up. Ditto with sleeve bearings in the spring carriers and no tube.

[billbedford]

What I have done when designing underframes with outside axleguards is to double the w-irons. The outer one is purely cosmetic. The inner one is a standard width to hold the axle in place, but has only the vertical legs and the slot for holding the bearing. The axlebox and spring fit between the two w-irons and once the step boards are in place the inner w-irons become all but invisible from normal viewing angles.

You can replicate this by either using BWF083 w-irons and making adjustments for the larger coach wheels or by using one of the w-iron frets designed for coaches, BWF003, BWF020 or BWF031 and removing the diagonal legs. All these should be available from Eileen's Emporium.