[espee]

Good start, in the sense that a middle bogie will move, but it seems to be over compensating for the given curve...

The longer the wheelbase the more pronounced the error.

click on pic to get larger image...

[darwins]

There is already a working solution for the centre axle of a three axle carriage.

This is create two 'virtual' bogies. Each bogie has a centre half way between the outer axle and the centre axle.

One 'virtual' bogie has two axles (front and centre) the other 'virtual' bogie has only one axle (rear).

Hence a long wheelbase three axle vehicle can be made to follow the curve appropriately.

Now to do the same with a three bogie vehicle rather than a three axle vehicle then rather than axles being children of the 'virtual' bogies then the real bogies need to be children of the 'virtual' bogies. (As in Erik's post).

Supporting additional bogies to be children of existing bogies (or virtual bogies) will solve both the three and four bogie problem and the Garrat problem.

[ianmacmillan]

Unfortunately the 6wheel carriage fix described by Darwin cannot be used with two axle bogies.
It requires the front virtual bogie to be made by joining the front and middle axleguards and spring as bogie1.
Using 2axle bogies, The bogie frames can be joined as bogie1 but you cannot join the wheels or they will rotate about their common centre.
You could make an invisible wheel as wheel11 and wheel12 and model the visible wheels as as part of the bogie but they would be non rotating.
You just need to hope nobody would notice.

I also tried making a three part wagon using a complete wagon as bogie1and bogie2 but this added the additional problem of how to position the load.

As I said in my previous post a 3bogie model is impossible.

Prove me wrong------Please.

[darwins]

Quote

As I said in my previous post a 3 bogie model is impossible.

...at the present time Ian.

I may be wrong, but I think the purpose of this thread is to bring about a change in Open Rails, such that it will be possible in future. If the bogies were able to parent to bogies rather than to main then it should be possible for the wheels to rotate about the centre of their bogies and for the bogies to rotate about the centres of their "span bogies".

If bogies were allowed to be children of other 'span bogies' it should be possible to solve all of the problems under discussion. (In the Garrat case the span bogies would themselves have the driving wheels associated with the.)

Other than the span bogie idea, the only solution I can imagine is allowing separate vehicles to be "grouped" together as a single vehicles - not sure if that would mean allowing muliple shape files to be a single eng or wag entity or if it would mean adding bogies as freight anims - which would need a new kind of freight anim...

[SP 0-6-0]

copperpen, on 16 February 2018 - 01:49 AM, said:

I have one from the old Abacus trainsim pages. It is a transfer locomotive that has 4 two axle bogies, with each pair of bogies attached to a bolster with the loco body riding on the bolsters.

I also have the part built Little Joe with 4 bogies sans wheels right now.

The NALW UP 4500HP gas turbine model is setup with two trucks per bolster. 4 trucks total under that machine.

Robert

[espee]

Quote

The NALW UP 4500HP gas turbine model is setup with two trucks per bolster. 4 trucks total under that machine.

Robert

If it the ones on Trainsim, the two trucks are a one piece rigid part, it only has two "bogies" and depending on the curve it may not swing too far, but the 4 trucks are not individual they are a D truck in essence...

[midneguy]

This is all a very interesting discussion, and one definitely worth having in order to try to develop OR's capabilities for complex models... Fundamentally this could lead to a workable solution for models such as the Milwaukee Road articulated electric locomotives, Articulated steamers of all types (Garratts, Fairlies, Big Boys and Challengers, etc). This has been on my mind a lot lately as I've been working on my Mason Bogie steam locomotive model...

I see several needs as critical as far as including more Bogies than the two we have now:

• It must be possible to define powered wheels in a Bogie, such as if "Wheels1", "Wheels2", etc. steam locomotive drivers are modeled as children of a Bogie group. This would allow for things like wheel slip to be animated correctly.
• Bogie groups must also be capable of supporting complex animations such as all the rods, valve gear, and pistons that are associated with with the driving wheels. Main and side rods will also need to be able to be child groups of the Drivers (Wheels1 groups etc) and able to be animated as they are today. I think it would be reasonable for other groups such as Pistons and other valve gear parts to be direct Children of the Bogie group they're associated with.
• It must be possible to be able to define a Bogie as a child of another Bogie in the model hierarchy. The group centers for the various bogies would dictate the attachment points, and the way the Bogies pivot relative to each other and therefore the main model.
• It will be necessary to be able to define Light and Steam FX as being associated with a particular bogie if required. An example would be when a head light is present not on the main model, but rather is mounted on the articulating portion of the locomotive. The light would then need to move with the Bogie, instead of being fixed on the main model.
• Each Bogie should have the ability to have a wheel radius or diameter assigned to it specifically. Steam locomotives have a particular need for this, since the lead and trailing wheels are often different diameter, and both are different than the main Driver wheel size. This could also be applied to things like driveshafts.

Of course this isn't necessarily a complete list of all the eventual needs in this area, they're just my initial thoughts after contemplating this for a long time... More flexibility in the use of Bogies certainly has the potential to solve a lot of problems and eliminate the need to build multi-part models :)

[darwins]

Thanks Midneguy. That looks like a clear, concise and hopefully complete analysis.

Where do things go from here? Will the developers pick up what you have said or would it be appropriate to paste that into the OR roadmap?

[edwardk]

I am back. The easy part that can be done which I am going to change is officially adding support for 4 bogies. I did test the locomotive with the 3 bogies. The default count of 3 axles per bogie is specifically tested for, but there was always a test that will cover any other addition not specifically tested for. This is all I can do for now. The other topic is out of my hands.

Edit: I did read in another post that MSTS does support 3 bogies so it was important that this was done.

Edward K.

[edwardk]

I was just reminded of one issue. During my initial work in this area, I did come across models that did not work properly for some reason so there were specific tests and hack fixes that involved bogies with more than 3 axles. Since one of the topics included more than 3 axles, I will request that specific models with more than 3 axles be posted here so I can test them.

Edward K.