Is this the right board?
 

I remember seeing a you tube video of a Western diesel (running on one engine) trying to pull it's train away from a station with sparks flying from the powered bogie !

slipping
 

TBH if the rail head is greasy, almost anything will "dance" if power is applied too harshly. But as to what loco class is the worst. I've no idea!

I've seen some extreme examples of how not to control a slip, and some drivers successfully coping with repeated attempted slips.....
IIRC some classes of diesel have an automatic detection / control for wheelslip! (takes the fun out of coping with wet leaves on the rail....)

I'm a bit too washed out to trawl back for the details....

Diesels dont like slipping because the enigne will just give more power as the wheels spin faster it thinks it is working harder and responds accordingly. So wheel slip indicators cut the power to prevent current from surging into the traction motors where it isnt needed until grip is restored. Load a train too heavy stick it on a wet gradient which is curved and anything will slip. For any bogies of 4 axles with 8 wheels the amount of contact with the rail surface is about the same area as your finger nails!

At the other end of the scale if you have something too light it will also slide along nicely! As experienced arriving into Bradford-on-Avon (notoriously ice rink-like) on a Class 153 early this morning. A nice loud set of wheelflats were produced in no time at all!

The class 87 was another notorious type for wheelspin. It was alleged that they would spin if there was a cloud in the sky! As for sliding, well I've just spent the last four weeks skidpan training on the St Albans branch, and believe me, the 350 Desiro is difficult to induce slide, even with fairy liquid.

Seen class 87 wheelspin few years ago now,was prity funy to see at the time....:D

I would have thought that Bullied Pacifics could be one of the candidates for being the steam engines most prone to slipping. All pacifics were quite"light on their feet" because of the natural tendancy to sit back on to the trailing wheels when starting, so losing adhesion.

Best wishes,

John H-T.

Most modern Muliple Units have WSP - wheel slip/slide protection (Slip is when you apply power, slide is when you brake).

WSP is considered necessary nowadays because if Loss of Adhesion is occuring elsewhere than on the leading bogie where you're sat, you may be unaware of it and thus can damage the traction motors/wheels/railhead.

Even if you do feel a slip or slide, damage can sometimes occur quicker than you can shut off power or release the brake. Sometimes in the Leaf Fall you can be braking nicely and then suddenly the speedo dips massively as the leading wheels start to slide. Blowdown valves quickly release the air from the brake cylinders on the affected bogies, but even so the wheels sometimes start clattering away like 50p pieces ! It seems incredible that their profiles can be altered by just a few second's slide, but then I suppose there's an enormous amount of kinetic energy at work.

Banging wheels are very irritating when you're stuck on that unit all day and it feels like your fillings are shaking out - Just one of the many 'joys' of Autumn driving. :(

FP

On the old steam locos there was a dry sand feeder in front of the main drive wheels; it was the fireman's job to check and top up the sand boxes before leaving the shed. The modern diesel and electric power units are not fitted with sand systems so far as I know.

On the Rhodesian Railways, all the diesels were fitted with a sand box and sand was jetted onto the track by air. They also had a warning bell when there was a wheel slip.

As far as i know all modern locos are fitted with sand boxes, an the class 66's are from what i've been told an heard are all auto sanding so as soon as wheel slip/slide is dected they inject sand onto the rail to gain traction. An interesting thing i heard a few years back when the 66's were new, they were blowing sand in copious ammounts into any S&C (Switches an Crossings) an it was costing Network Rail loads due to the sand wearing out the slide chairs. When the sand mixed with the grease, it formed a extreamly abrasive paste. So Network Rail asked for the auto sanding to be modified so as the drivers could apply the sand manually like any decent British Loco design.

A comment on Southern Pacifics

Bullied put their running motion
In a kind of oily potion
Thus it was the wheels went round
But seldom ever touched the ground.
Clad in a kind of cardboard vest
They steamed quite quickly to the West.

I'm trying to devise a similar rhyme for A2/2s, which Toram Beg said "would slip on Portobello Sands."

DSD