Wheel width

Hi All
I am intending to replace the plastic wheels on my coaches an freight wagons. My wheels are all 12.5 MM. in diameter but are of varying widths. I have issues with some of my freight wagons derailing on points. On further investigation these all have a width of around 2 MM. When I switched these wheels to the wheels with a width of around 4mm I have no issues.
I have looked at the replacement wheels available from Hornby and the only information they give is the diameter with no reference to the width. Does anyone know what the part number would be for the wider rims as opposed to the narrower ones. I am not too worried if the wheels are solid or spoked.
Any help appreciated.
Shaun

Shaun, freight wagon wheels were 3' 1" or so which scales to 12.5 mm or so.  Coach wheels were 3' 6" in diameter or 14mm in 4mm scale.

If your wheels are 2mm wide they're P4!.  The flanges are probably very small.  These are not intended for RTP points like Peco and will fall into the pit at the common crossing.  No wonder they're derailing. 

OO wheels should be around 2.8mm wide so that they are supported at the point crossing.

I think the wheels from Hornby and Bachmann are very good value and are right for OO trackwork.

John

Thanks John
That would explain the derailing…..I will get some of the Hornby replacement wheels and give them a try. All my coach wheels are 12.5 mm diameter except some Pullman which are14.1 but these are metal anyway so do not need replacing.

Shaun

I've never seen coach wheels that were 12.5 mm are you certain they're right?  What coach are they on?  If the wheels are on old models, the profile may be poor and the wheels should be replaced in that case.

There are three types of 12.5 mm:

1)  square spoke
2)  split spoke
3)  three hole disc

1) are probably the most common and can be found on unfitted stock mostly, but I've seen them on fitted stock with four brake shoes.

2) I think these are quite old and were found on a lot of PO wagons.

3) Are usually found on clasp brake vacuum fitted stock (8 brake shoes).

John

Don't think there are any different width wheels for RTR stock Shaun.

Older metal wheels might be a bit wider than modern replacement wheels and I'm not sure if the Dapol and Bachmann replacement versions are exactly the same width as Hornby, but there can't be much difference.

I used Hornby R8097 12.5mm three hole disc wheels on the rake of mineral wagons I've been working on, but I ran out and used some Hornby R8096 solid disc wheels on a couple, left over from converting coaches.

(Think it is pre-grouping and BR Mk1 coaches that have the larger diameter wheels.)

If some wagons are derailing on points, it's almost certainly the back to back measurement is a bit out, try changing it to 14.5mm.




Ed

Thanks Ed / John



  That was mainly my understanding, I double checked my coaches last night and they are definitely 12.5 mm. On scouring the internet last night I found several articles saying that for an accurate scale (OO) wheels should BE 14.1 mm but due to clearance issues Hornby made there wheels under scale hence the 12.5 mm diameter.



  The diameter is not the issue with my wagons its the width. Again through the power of the internet I read that some older points would not accommodate the newer narrower width wheels that are now common place (Some of my rolling stock is quite old). I would be a bit surprised if it was my points causing the issue as they were all purchased (new) within the last two years although the issue is only with two of them so could be that I was sold a couple of older ones in amongst them.



  I have checked all the back to backs and they are fine. I have a nice little brass gadget that I got from Hattons which I use.



Shaun

Hi Shaun,

Recent Bachmann wagon wheels - 2.8mm back to front, tread is 2.15mm.

Some possible issues:

If you have re-gauged to a BTB of 14.5mm that might be a problem depending on what the actual gauge of the track is.  Back-off a tad to around 14.3mm, as turnouts seem to have a tighter tolerance than flex track. I can't speak to Peco code 100, but my Peco code 83 flex track has a gauge of 16.7mm compared with the turnout's 16.55mm. I had this issue with a Hornby Castle that was regauged to 14.5mm from 13.7mm. It would always derail on one Peco turnout. Backing-off to 14mm solved the problem.

The wheels need to have a bit of lateral movement, otherwise they have issues going around the turnout curves and across frogs. The angled tread and frog guard rails will keep them on the track. Helps to have a decent micrometer rather than a BTB gauge for this. [The gauge has to be appropriate for the minimum/maximum track gauge].

Do the "derailers" have Kadee's? If so check the height of the trip pin, if it's too low it will hit the frog and derail the wagon. Common issue, and difficult to find with a wagon in the middle of a rake. If you're using tension locks is a hook hanging too low? ("Dapol Droop").

Have you checked the frog? It should be slightly rounded, not razor-sharp. With a  BTB of 14.5mm and "tight" track the wheel will catch it on the wrong side and often bounce, with a derailment. If it's razor-sharp round it with a bit of #400 emery (or a nail emery board).

I just ran some semi-fine scale wheels (tread 1.5mm) through my Shinohara code 100 turnouts. Nary a problem, but the BTB is around 15.5mm and the track is 16.7mm.

Old turnouts have wide spacing between the frog and the closure rails to allow for 3mm+ treads.

Nigel

I bought a B to B gauge whilst I was in UK last month and, being very excited to check my stock wheels when I got home, I found most were out !!!  Either that, or the gauge is wrong ………………. :hmm

I'm a "OO" man and so far, all the wheels I've checked have been under that - new or old.  I then started doubting so, as derailing is not a problem, decided to leave well alone and the gauge is now in a drawer.

Checking too much "stuff" can lead to identifying problems you didn't have before checking …………….IMHO, of course !!!   :roll: :roll: :roll:  A bit like reading Blake's Medical Dictionary.  Since reading mine, I've come to the conclusion all my doctors are useless - in spite of what they tell me, I have hundreds of very dangerous diseases …………………. :cheers :cheers

[user=6]Petermac[/user] wrote:

I bought a B to B gauge whilst I was in UK last month and, being very excited to check my stock wheels when I got home, I found most were out !!!  Either that, or the gauge is wrong ………………. :hmm



I'm a "OO" man and so far, all the wheels I've checked have been under that - new or old.  I then started doubting so, as derailing is not a problem, decided to leave well alone and the gauge is now in a drawer.



Checking too much "stuff" can lead to identifying problems you didn't have before checking …………….IMHO, of course !!!   :roll: :roll: :roll:  A bit like reading Blake's Medical Dictionary.  Since reading mine, I've come to the conclusion all my doctors are useless - in spite of what they tell me, I have hundreds of very dangerous diseases …………………. :cheers :cheers

Ha Ha very good Peter :doublethumb I too am usually in the "if its not broke don't fix it" camp…Unfortunately for me its broke so I have to fix it.

All part of the fun

Shaun

All very interesting. I gave up on my BTB lump as well, I now use the micrometer. I have a feeling that flex track is wider than gauge to allow for the contortions it goes through. Turnouts maybe not. For hand laid track using 3 point jigs the curves are automatically widened.

My guiding rule for wheel sets is that they should have a bit of lateral movement, i.e. the flange is not in contact with the rail head. We're not talking a lot here - somewhere around 0.5mm. The absence of a 5° cant to the rail (as in the prototype) means the cant is instead made on the tread. A tread of around 2mm gives plenty of leeway. The cant to the tread means that the wheels are automatically centered on the railhead.

I suspect the reason why a BTB of 14.5mm works with 16.5mm track is that the flange is around 0.6mm, which gives around 0.4mm wiggle-room. More if the track is not truly 16.5mm.

If the BTB is 14.5mm on everything and one wagon still derails then it's not the gauge. As I said, gauging may not actually be the issue. Especialy with tension locks.

If you use finer-scale Kadee couplers gauging does become an issue - too tight (wide) and the coupler is raised. Slight dip in the track and it decouples as the preceeding wagon/car drops.

Nigel

Had a play around last night and did as Nigel suggested. I set the BTB on the wagons that were causing problems (narrower wheels) to around 14.2 / 14.3 and hey presto no issues.
I then went on to check wagons that were running fine without de-railing and found them to be 14.5. The only thing I can think off is what I mentioned in my original post and its down to the overall width. Wagons with the wider wheels and a BTB of 14.5 run just fine but the wagons with the newer narrower wheels need to be set at around 14.2 /14.3.

No idea why but I am now happy and my wagons run freely. Many thanks for all the comments.

Shaun

Hi Shaun,

One of those "If in doubt try the obvious (and easiest and cheapest) solution". Interesting that there may be differences in tread width. When you model in HO you get used to the NMRA standards re wheel dimensions very quickly.

I got some OO wheels from Ultrascale as replacements for my mainline Warship and Lima GWR diesel railcar in the mail on Friday - the tread is around 1.85mm. I may have to mess around with the BTB a bit as this is slightly narrower than the originals.

I asked one of the reps at the Peco stand at Warley on Saturday what the actual gauge was on code 100 HO/OO track (which is now termed HO track since their introduction of the new OO track). Clueless.

Nigel