Wheel slip

[almark]

All depends on what sort of power you apply,no good just ramming it from idle to wide open lol

[plewsy2105]

oh very true although it doesn't help when the 37 is completable knackered....

plewsy2105

[Kariban]

The Class 59s in real life (and subsequent GM diesels) utilised some of the physics of wheel slip to their advantage. The documentation I have in front of me backs up what I learnt as a mechanical engineer. Even when wheels start to slip the tractive effort can still increase provided the slippage is controlled. That is the essence of the GM wheel creep system.

It's the same for road wheels, much exploited by racing cars as of course they move around in two dimensions; maximum cornering force is when you're drifting sideways slightly. ( not quite the same as rally cars, which is more about force vectoring ).

I bet supercreep doesn't do wonderful things for rail life...

[almark]

oh very true although it doesn't help when the 37 is completable knackered....

plewsy2105

Well,that would play a part

[Kromaatikse]

Even on level track, in RW the wheelslip seems to depend quite heavily on train weight, which is incorrect - it should only depend on the tractive effort exerted by the loco.

On diesel-electrics, usually the leading axle is the first to slip, especially uphill. This is because the tractive effort tends to rotate the bogies under the loco, lifting the front ends slightly. With SEPEX or three-phase motor controls, this can be compensated for automatically, but the likes of the 37 are too old to have that. However, some of the 70-series locos had a parallel motor layout which was much better at slip recovery than the series-parallel layout on most DE locos.

This is also why 4-6-0 locos are so sure-footed - the same rotation applies but to the entire frame, and moves some load from the leading bogie to the rear driving wheels. When facing uphill, the (very heavy) boiler water is also moved towards the firebox end, which is where the driving wheels are. With a 4-6-2, the extra weight still falls on the trailing axle, but this is now unpowered...

I don't know much about the Q1, but since it was a very lightweight build due to wartime materials shortages, it is entirely possible that it didn't have the weight for full adhesion. As an 0-6-0 design though, all the weight it did have would have been adhesive. I do know that the Schools class were notoriously slippery, but that's what you get when you put three decent-sized cylinders on only two driving axles.