Bogie wheel base - long better or short better for stability?

[Granitechops]

I notice that a lot of 45mm track bogies, commercial products, are about 2.25 ins axle centres

However I pesonally think that they can look a little odd

& would look better stretched to 3.25ins centres

also performance wise, I would think that an almost square foot print would be more liable to ocillate than a longer wheelbase

This is a shorter wheel base

 

[Granitechops]

This is the longer 3.25 ins wheelbase

Any one any ideas what works best in full size for example

or has any experience in this field

or even ideas to express on the subject


I do know for example that in my experience through road trailer building,

that a longer wheel base on a close coupled 2 axle trailer

is a whole lot more stable than a shorter one

but that of course does not have the stability of guiding rails

 

[stevedenver]

as someone with a rough and tumble track work due to the nature of my garden and train area, as well as being ............'flexible' ie my track is yet to be fixed as my plans are somewhat changed as well as delayed due to some major house improvements in the works 

i can tell you without qualification 

that shorter wheel base and shorter bogies are better able to accommodate track that shifts in elevation either lengthwise or which is torqued, that is, one end of a piece is not level with the other laterally

since i run not only euro -in which even those LGB cars with brake platforms are less forgiving than thier non brake counterparts

but also US stock of varying lengths, from porters to Genesis,-the longer things get the more important level track

on nice flat track, a longer wheelbase will provide something of a 'lower center of gravity' compared to a little dumpling style car-as there is more car weight to the number of axles etc

but i think the shorter stuff is best suited to true 'field railway' conditions, and i think this is one consideration LGB had in mind for its starter sets-they would best tolerate an inexperienced or sloppy ROW

 

[C&S]

looking at your pictures, I'd suspect that the short w/b bogies are from 2ft gauge wagon designs (eg War Dept stock) while the longer bogies might look right on 3ft gauge prototypes.

 

[JRinTawa]

I'd agree with Steve, especially for rigid bogies (i.e. no springing or compensation on the bogies) the shorter wheel base would cope with track irregularities better, and with tight curves too.

 

[Rhinochugger]

The theory is that a longer wheelbase should be more stable.

In practice it's difficult to say because we are not using scale loads/weight, not using scale wheel profiles, and do not always use body mounted couplers.

My suspicion is that a bogie mounted coupler adds a bit of stability, but the longer bogie should be better.

Apart from the US Jackson Sharpe bogies, I think the L&B carriage bogies are the longest :thinking: 3' 4" from memory

 

[Rhinochugger]

BR Research at Derby worked out that a wheelbase of twice the gauge was most stable. Although whether this only applied at 150mph I can't remember...

Well, that'd be OK for Mike then

 

[pugwash]

BR Research at Derby worked out that a wheelbase of twice the gauge was most stable. Although whether this only applied at 150mph I can't remember...

They weren't quite renowned for getting things right though - ask anyone from Derby, Royces got the guys with GCEs.

 

[johnsaintjim]

Interesting question and discussion Don. I would add:

We don't normally have suspension or even compensation. I was delighted to find that some LGB bogies I bought were compensated though.

Longer wheelbase rigid four-wheelers definitely hold the track less well than short wheelbase ones. When the rails are not in the same plane, especially on a curve, the longer the wheelbase, the more likely the rigid chassis four-wheelers are to ride up on the rail and derail.

As for lorries and cars, as you say, they don't have rails but IMHO even more importantly, they have suspension and most of them don't have rigid bodies. (We had to work hard at the rigid body bit in cars but that is another story entirely).