A couple of things..

Firstly another instance of lying by Royal Mail. I was told my parcel from the NGS was to be delivered Sat between 10.35 and 13.35. Needless to say- nothing

I'm so fed up with the bombardment of mails from Rails of Sheffield. It wouldn't be so bad if they asked my preferred gauge. I could unsubscribe but something may get missed so I guess I'll have to put up with it

As @PLD says, different items/designs of stock may well have different sized wheels, that in itself is not a cause of derailment.

You need to be looking for problems with:

mixed/different wheelsets on the same model (ie. someone's fiddled about and removed/replaced wheels incorrectly)

a wheelset that's been pushed out of the pinpoint axle bearings by bad handling or storage
any back-to-back problems

stiff bogies not swivelling freely

coupling droop causing the pin to catch on the rails

couplings too high and catching buffers on curves

dog-legs or "missed" rail joints

All the wheels on a single vehicle should be the same size but they don't have to be the same on every vehicle in the train.

The right size is whatever was intended for that vehicle which  could be any of a range from 6mm - 7.5mm depending on the type.
From your description it is a specific issue confined to one coach so leave the others were alone. Far more likely is an axle out of gauge or something catching stoping a bogie pivoting or if it has pivoting couplings those sticking.

I have been slowly (very slowly) building my layout and collection of rolling stock over the last 3 years and have just stumbled across an issue I have not noticed until now. All my coaches have run beautifully until the other night when one kept derailing at two specific places. Upon investigating, it was then i noticed that some of my coaches have different sized wheels to the others, which I think may have been the cause of the derailing. It's probably just luck that I haven't had coaches with different sized wheels coupled together before.

Therefore I guess the correct action is to change the wheels on some of the coaches so they all match. However, which size is the 'standard ' size? I am going to be very untechnical here and say I have some with small wheels and some with larger wheels!

All coaches are from Farish but guess some are a lot older than others, not sure if that is a factor.

Any help or advice would be appreciated. My layout is a preserved line so I do change the rakes about so I wasn't planning on keeping specific sets of coaches together all the time.

Looks like I'm going to have to go the magistrates court to stop the idiots at Ovo applying for a warrant.

Going to be fun when I explain to the beak that Ovo are not the energy provider at that property 

I've taken to signing messages to them "Yours, hope you go bankrupt soon" at this point.

I have been double heading with DC for years and so long as the loco speeds are reasonably similar there is absolutely no problem. There are a few examples, both diesel and steam, to be seen in this video. You have to watch carefully or you will miss them.

Here's a few more.

You can even do banking with DC. Go to 1:06 on this video.

The problem with factory dummy locos is modellers that expect the dummy for the price of a coach... With economies of scale,  per unit, it's probably only pennies difference to produce 500 motored and 500 dummy as it is to produce 1000 motored...

As to double-heading on DC, unless the locos are substantially different, I think the issue is over-thought. I've never found two of the same type that were sufficiently different to worry about (if they are it probably means the slower is in need of a good service!) but I'd always put the slower loco as the pilot and the faster inside having the couplings between the two compressed rather than stretched.
Top & Tail admittedly might be more of an issue because of the dynamics of forces on the coaches, especially on tight train-set curves...

Quote from: Newportnobby on February 06, 2026, 11:59:58 AMSpeed matching for me is putting two locos on an oval of track and seeing whether one catches up with the other. Even if they're close, it's still not something I tend to do. Just take a motor out of one of them, I hear you say. Simples.

This is exactly what I do, run 2 on the same track and see if they run at similar speeds. Here are some very old videos of my double headers which run absolutely fine using this method:




Anyone who watches my videos will know I have a 'thing' about car transporters, usually Ford cars involved, and with my Cartic rake which is loaded with 112 Oxford Diecast cars and my Kato rake with 104 OD cars I often use double heading as it definitely helps with what are very heavy trains.

I have also used the 1x powered, 1x dummy method and in this case I usually push the dummy with the powered loco as I find they run better that way especially if the dummy is a Dapol 73 which is very light.

I may video some more later today (depends if I go to the pub instead). Or tomorrow (depending on whether or not I go to the pub instead). Or maybe another day (when I'm on call and not allowed to go to the pub).

And finally. I think I have only ever run 1 train top and tailed and it seems to run fine by me. Some of you will have seen it before but here it is in case you missed it:

I have three pairs of locos that run as powered plus dummy, albeit they haul one or two wagons.
The dummy Farish class 20s and 37s have had the motors and gears removed and haul one and two nuclear flask wagons respectively.
The Dapol class 153 defied all attempts to remove the faulty motor so the gears were removed from the bogies so that they free wheel but I left the pickups so I could have lights on the unit, this is hauled by another class 153.

Geoff 

It's gone.

Thanks for the innovative ideas, though!