Model Railway Forum

RSR Engineer wrote: ↑Wed Mar 17, 2021 2:47 pm <SNIP>
Sorry, I don't see any risk of damage to the track (and certainly not to the loco) from slipping wheels.This happens all the time without traction tyres. In fact, it happens on every curve - that squealing, whispering noise we hear on real-life trains going round sharp curves is caused by it, coz they have no differentials like road vehicles.

Cheers,
Artur

Not quite correct Artur, The noise heard as a real train passes around a curve Squealing/grinding noise is the wheel flanges binding against the inside faces of the rails. That is why rail lubricators (rail greasers) are used in some areas, these apply a thick black grease to the rail/wheels to try and stop or reduce the rail side wear. Rail side wear is consider a very serious issue for the Permanent Way teams and I have known inner rails to be transposed to outer rails on curves to attempt to give the rails more longevity. The shards of removed rail are razor sharp and if they come off in long enough pieces they can even touch across the rails side to side and short the track circuit, causing a signalling failure.

Wheel slip on the real thing is frowned upon, especially by the Permanent way and Train depot people as it creates serious burn marks and damaging ruts in the rail head and excessive wear on the wheel tyres. Result is frequently where serious wheel slip has occurred a section of rail has to be replaced or the wheels to have replacement tyres or wheel sets fitted.

not to mention the knurling on the dock shunter's wheels adding further friction and thus damage.

if you can damage track by using sandpaper or emery board on it, you'll damage it with slipping wheels.

I stand corrected, Brian, about the squealing on curves. Of course, the coning of the wheels compensates for the different radii of the inner and outer rails. I've also seen the kind of wear you're referring to on the outer rails of tram lines, which have to get round street corners. I'll take my chances, Stese, on damage to the track. And the Tri-Ang dock shunter is in any case only to be used (say) twice a year on the dead-end hidden sidings.

As I say, wheelslip happens all the time on model railways because of (a) poor factor of adhesion, (b) steep gradients and (c) rolling stock that doesn't run freely enough. Unless the locos have traction tyres, of course. A case in point is the Liliput Swiss class A3/5 600 4-6-0. This engine has no traction tyres. She can pull 22 axles on the level at a scale speed of 80 kmh without noticeable slipping (Electrotren Spanish Costa coaches with all-metal wheels and well-oiled metal journals). On a 1 in 68 gradient her limit is 14 axles. With 22 she slips to a standstill. The prototype could manage a lot more than that and if overloaded she'd almost certainly stall before she slipped.

Also, model locomotives are all too often run at greatly overscale speeds but this usually goes unnoticed, especially on diesels and electrics, disguising wheelslip. On a two- or four-cylinder loco, it's four puffs per rev. Listen to a recording of a steam loco and dance the Locomotion in time to it and compare that with the average model.

Cheers,
Artur

I don’t recall any of my OO locos slipping wheels but they always started off very slowly. Having said that the M7 lacked traction.

I do remember them pulling away with an enormous amount of slip when I was young but I used to just turn the controller to max.

I personally on all my own and my club layouts have never seen wheel slip occur. Even on gradients. Slowing of the loco/train - Yes, but not wheel slip!
Wheel slip would result in increased motor speed and much more noise due to the motor turning so much faster, never experienced this.

Thank you for your comments, gentlemen. Sorry to be slow getting back to you. I am somewhat surprised that wheel slip is so rare. Could be I was just overloading my locos. I certainly intend to investigate further but I won't be able to judge it properly on my own layout till I have certain models out on the track.

Cheers,
Artur

It is often caused because the rolling stock being pulled isn’t free running.

I have to say that in the past when I was a GWR modeller, I hated tender driven models because a little wheelslip from the loco while starting off a heavy train was prototypical. Yes, the drivers did all they could to prevent wheelslip, but on damp rails it was common.
It is still fairly common today. I worked on the railways and one early morning train on icy mornings could easily get trapped on a certain branchlines due to wheelslip and would have to wait two hours for the secons service to couple up so the two trains could join (And the second train would have gone over the icy rails a second time so there was less ice) so that the line could be cleared ad trains would run normally.
This happened a fair few times when they used to run class 158's on the first service down to Pembroke Dock which used to often run down as a class 5 (Empty stock) down to the Dock. On the way back there is a steep hill to climb out of Tenby and it was my job as a guard (And we sometimes had the catering trolley staffs assistance) to position ourselves above the driven wheels as those things are only driven by one pair of wheels per vehicle, so we would jump up and down in the coach when we felt the wheels slipping and this was just enough to get those train up the hill, though we were often late due to the delay of getting up that hill.
They tried other units instead. First the class 143's as it was thought that they were a better choice having more weight with passengers over only four wheels but nope. They had similar issues.
The 153's in pairs were tried which were not too bad, but it was the class 150's that saved the day, so we always ran class 50's in the winter timetable on that branch in the morning.
The second service had less issues as the first service would have cleared the ice on the hill.

Wheelslip is actually more common on the real railways then one might think. Modern diesels that pull heavy goods trains have special electronic equipment to limit wheelslipping problems but DMU's don't.

Mountain Goat wrote: ↑Mon Mar 22, 2021 1:27 pm
Wheelslip is actually more common on the real railways then one might think. Modern diesels that pull heavy goods trains have special electronic equipment to limit wheelslipping problems but DMU's don't.

Modern cars also have this electronic control. Different names by different manufacturers, but basically the same.

IanS wrote: ↑Mon Mar 22, 2021 4:13 pm

Mountain Goat wrote: ↑Mon Mar 22, 2021 1:27 pm
Wheelslip is actually more common on the real railways then one might think. Modern diesels that pull heavy goods trains have special electronic equipment to limit wheelslipping problems but DMU's don't.

Modern cars also have this electronic control. Different names by different manufacturers, but basically the same.

Urmmm, yes. I had that in a Volvo 850 T5 estate and it was known as traction control. While it kinda worked, it proved a little dangerous to use in certain conditions, and in practical terms it meant that instead of shredding one tyre, it would shred both tyres. If I was heavy footed I could go through tyres in 2000 miles, though being light footed had 4500 miles out of a pair. Those cars (I also had a standard 850 2.5 10 valve estate before it) would not only shred tyres, but they needed their rear trailing arms replacing at every MOT and the parts looked identical, but it was £250 a time just in parts for the ordinary 850, and £500 a time on the T5 (I argued with the garage saying they were the same part and to put rhe cheaper ones on the T5 (They looked the exact same size and shape) but they said they must fit the specified part).
Money pits those cars were. The older versions like the 9 series and the 7 series were excellent cars and the 740GLT was quicker in a straight line too, though the handling upgrades on the 9 series meant I could follow a T5 through the bends, so I just don't know why the T5 had such a good write up. It did feel like a go cart for the first month or so after having yet another new set of suspension parts (The standard version felt similar) but in reality, the rear wheel drive older models were better cars and far cheaper to run too. Admittedly the traction control was there on the T5 which in a straight line it helped, but on corners on a wet road the T5 could end up in a ditch, as what it meant was that instead of one drive wheel sliding as those cars were far too powerful for their chassis, one ended up with both front wheels wheelspinning at the same time and the front of the car had no actual grip at all... And it wasn't that one was being heavy footed either.
Yet the older rear wheel drive versions did not have this issue as even if they were wheelspinning going down the road at 70mph they could be controlled.
I did not get to try one, but the four wheel drive T5's that the police had would have solved some of the issues at a guess? But in reality the saloon versions of the car which were lighter at the back would be the ones to go for.
One good thing about them though was their load carrying capability. Amazing space in those estated and I had a full 10 ft with the front seat folded flat as well. One could fit a whole 6x4 layout in the back and run trains on it too! And both the estates I had had 7 seats with a built in child seat as part of the armrest. A very clever design which also was fitted to the 9 series cars (Basically a 7 series with the little niggles sorted out). The 7 and 9 series estates were easier to load and unload as had wider back doors. The V70's were narrower still so they were less practical. They said they solved the traction issues on the V70's but some owners were not so sure.