OO Back to back,14.50 or 14.75

[ERIC ALLTORQUE]

Running code 75 peco is the back to back better set to 14.75 or 14.50,thoughts on whats best?

What do you run at and any issues?

[roythebus]

Best leave it at 14.5, some flanges are wider and may bind on 16.5 gauge.

[ikcdab]

 measure your pointwork. When the back of the flange of one wheel is just touching the check rail, the other flange should just clear the crossing nose.

[flockandroll]

 

5 minutes ago, ikcdab said:

 measure your pointwork. When the back of the flange of one wheel is just touching the check rail, the other flange should just clear the crossing nose.

So (iirc) for anything rtr with wheels made in the last 20 years you might actually need 14.4 to stop one wheel dropping...

[Dungrange]

1 hour ago, ERIC ALLTORQUE said:

Running code 75 peco is the back to back better set to 14.75 or 14.50,thoughts on whats best?

What do you run at and any issues?

 

For Peco Code 75, back to back dimensions should be 14.4 or 14.5 mm, which is the commercial or intermediate standard.  14.75 mm is for 00 Finescale standards, which is hand built trackwork with a flangeway gap of 1.0 mm (ie the same as EM).

[kevinlms]

2 hours ago, Dungrange said:

 

For Peco Code 75, back to back dimensions should be 14.4 or 14.5 mm, which is the commercial or intermediate standard.  14.75 mm is for 00 Finescale standards, which is hand built trackwork with a flangeway gap of 1.0 mm (ie the same as EM).

It ought to be remembered that the initial standard for Chinese made Hornby, was for a back to back of 13.8mm!*  This explains why early stuff didn't like Peco Code 75 points. Hornby made the decision to change the dimension early 2002 I believe.

 

* 13.8mm is listed as such in the review of Hornby 'Battle of Britain' class in Railway Modeller 2001 December 'Latest Review'. This was a random issue I picked up.

[Andy Reichert]

18 hours ago, flockandroll said:

 

So (iirc) for anything rtr with wheels made in the last 20 years you might actually need 14.4 to stop one wheel dropping...

 

I don't understand that reasoning.

 

Andy

[Il Grifone]

On 18/08/2020 at 02:27, kevinlms said:

It ought to be remembered that the initial standard for Chinese made Hornby, was for a back to back of 13.8mm!*  This explains why early stuff didn't like Peco Code 75 points. Hornby made the decision to change the dimension early 2002 I believe.

 

* 13.8mm is listed as such in the review of Hornby 'Battle of Britain' class in Railway Modeller 2001 December 'Latest Review'. This was a random issue I picked up.

 

13.8 mm is far too narrow and suitable for the old Tri-ang wheels (maybe some confusion arose). up to about 2000, Hornby had been using the old Hornby Dublo wheel standards for which the back to back should be 14.2mm (actually something imperial! 560 thou. IIRC)

Edited August 19, 2020 by Il Grifone

[kevinlms]

28 minutes ago, Il Grifone said:

 

13.8 mmis far too narrow and suitable for the old Tri-ang wheels (maybe some confusion arose). up to about 2000, Hornby had been using the old Hornby Dublo wheel standards for which the back to back should be 14.2mm (actually something imperial! 560 thou. IIRC)

The chart/diagram showing the wheel dimensions seems to have crept in without fanfare about 1992 December. Not sure when they stopped it, but not in recent issues.

But certainly as low as 13.7mm!

[John Tomlinson]

On 18/08/2020 at 02:27, kevinlms said:

It ought to be remembered that the initial standard for Chinese made Hornby, was for a back to back of 13.8mm!*  This explains why early stuff didn't like Peco Code 75 points. Hornby made the decision to change the dimension early 2002 I believe.

 

* 13.8mm is listed as such in the review of Hornby 'Battle of Britain' class in Railway Modeller 2001 December 'Latest Review'. This was a random issue I picked up.

At 13.8mm, if that was the factory setting, the locos made a ghastly crashing noise over the points. I think it applies to Coronation Pacifics of the period also.

 

Probably done to stop the front crankpin fouling the connecting rod. If you amend the back to back you also need to reduce the sideplay on the front pair of drivers otherwise you get mangled rods on curves. Not difficult to do.

 

John.

[Il Grifone]

It would certainly explain problems with pointwork. Even with the original Peco streamline flangeways of 1.6mm it would be tight (16.5 - (2 x 1.6) = 13.3), but they had tightened them to 1.4mm in the meantime (I think these are the correct figures - memory - not was it was...).

Edited August 19, 2020 by Il Grifone

[kevinlms]

19 minutes ago, John Tomlinson said:

At 13.8mm, if that was the factory setting, the locos made a ghastly crashing noise over the points. I think it applies to Coronation Pacifics of the period also.

 

Probably done to stop the front crankpin fouling the connecting rod. If you amend the back to back you also need to reduce the sideplay on the front pair of drivers otherwise you get mangled rods on curves. Not difficult to do.

 

John.

Just checked the first Peco review different to the 13.8mm, was the review of the then new Black 5, in the 2002 August issue, where the dimension is listed as 14.5mm.

No mention of the difference, just the stats.

[Free At Last]

41 minutes ago, John Tomlinson said:

At 13.8mm, if that was the factory setting, the locos made a ghastly crashing noise over the points. I think it applies to Coronation Pacifics of the period also.

 

Probably done to stop the front crankpin fouling the connecting rod. If you amend the back to back you also need to reduce the sideplay on the front pair of drivers otherwise you get mangled rods on curves. Not difficult to do.

 

John.

Ah, that explains why I had to re-gauge 3 of my Duchesses and because of the excess slop I had put overlays on the frames.

[Il Grifone]

I set* all my 00/H0 wheels for a check gauge of 15mm and they then all run on my track without problems - mainly Peco Streamline code 100 and Formoway (yes! that ancient!). Since no-one seems capable of making the flange thickness constant any more, this procedure is essential. (Not helped by British and American wheel standards being different.)

 

*Being lazy, I usually only reset them if problems arise.... (If it ain't broke, don't fix it - the first law of engineering!) A new vehicle might get checked especially if it isn't free running

Edited April 6, 2021 by Il Grifone

[DCB]

I think you need two gauges, one to ensure the back to back is wide enough, and a second to ensure it is not too wide,  Mine are 14.25 and 14.75.  Two different gauges on the ends of one tool.    If neither fit or both fit its a fail. Only if the wheels fit the 14.25 gauge and do not fit the 14.75  is the B to B within my tolerances.   If the B to B is too narrow the wheels will climb over the check rails,  Hornby square axle metal tyre wheels are really bad for this,  If the B to B is too wide one wheel against the check rail will not hold the other wheel one wheel away from impacting  crossing V's.    Using one gauge means a good deal of skill and judgement to get a nice sliding fit, like setting CB points or tappets on old cars, and those are best left to experts.

[polybear]

The B2B dimension will also vary depending on whether or not you are running RTR only, or kitbuilt (AG etc.) wheels too.

[Il Grifone]

18 hours ago, Il Grifone said:

 

13.8 mm is far too narrow and suitable for the old Tri-ang wheels (maybe some confusion arose). up to about 2000, Hornby had been using the old Hornby Dublo wheel standards for which the back to back should be 14.2mm (actually something imperial! 560 thou. IIRC)

 

I measured some Tri-ang wheels to hand B2B 13.8mm flange thickness 1mm

 

  

8 hours ago, DavidCBroad said:

I think you need two gauges, one to ensure the back to back is wide enough, and a second to ensure it is not too wide,  Mine are 14.25 and 14.75.  Two different gauges on the ends of one tool.    If neither fit or both fit its a fail. Only if the wheels fit the 14.25 gauge and do not fit the 14.75  is the B to B within my tolerances.   If the B to B is too narrow the wheels will climb over the check rails,  Hornby square axle metal tyre wheels are really bad for this,  If the B to B is too wide one wheel against the check rail will not hold the other wheel one wheel away from impacting  crossing V's.    Using one gauge means a good deal of skill and judgement to get a nice sliding fit, like setting CB points or tappets on old cars, and those are best left to experts.

 

I was taught that the correct way to set points/tappets is that the feeler gauge one size smaller should fit and the size larger not.

That's one reason I use a vernier caliper gauge to set B2B (I do have a nice digital caliper, but still prefer the vernier.

Edited August 20, 2020 by Il Grifone

[ikcdab]

I can only reiterate what I said before.  The b2b is a derivative of the check gauge. Take a spare set of wheels and set them so that when the back of one wheel is just touching the check rail, then the other wheel is just clear of the crossing nose. Then measure those wheels. That is your desired back 2 back 

[brightspark]

This why the BMRSB was set up as 00 standards were all over the place.

I am hunting through the old magazines  to find out what they ended up with. But of interest in MRC June 1936, it was determined after some experiments that for 00 = 16,5mm gauge track the BMRSB recommended standards are.

Dimension A (wheel width) 2,25mm

Dimension B (Back to Back) 15mm

Dimension C (Flange depth) 0,75mm

Dimension D (Flange width) ,5mm

The outside faces of check rails should be 14,5mm

The gap between running and check rail should be 1mm

 

Also of interest 19,00mm track, referred to as "true 4mm scale track, the back to back is 17,5mm with check rails set at (outside face) 17mm.

 

[Il Grifone]

9 hours ago, brightspark said:

This why the BMRSB was set up as 00 standards were all over the place.

I am hunting through the old magazines  to find out what they ended up with. But of interest in MRC June 1936, it was determined after some experiments that for 00 = 16,5mm gauge track the BMRSB recommended standards are.

Dimension A (wheel width) 2,25mm

Dimension B (Back to Back) 15mm

Dimension C (Flange depth) 0,75mm

Dimension D (Flange width) ,5mm

The outside faces of check rails should be 14,5mm

The gap between running and check rail should be 1mm

 

Also of interest 19,00mm track, referred to as "true 4mm scale track, the back to back is 17,5mm with check rails set at (outside face) 17mm.

 

 

The standards were modified later (most/all were retained for H0). Wheel thickness became 2.5mm, flanges remaining at 0.5mm. The back to back was eased to 14.5mm and flangeways to 1.25mm.

19mm became 18 (EM) for clearance reasons - it remained 19mm in the states as their larger loading gauge and central rather than lateral framing of rolling stock favours a wider gauge. EM became 18.2mm later, as it was found that there was insufficient tolerance (play, slop) for reliable running.

Legend has it that Peter Denny didn't have the running problems others were having and it was found his track gauge was faulty and gave 18.2mm rather than 18mm.

Wheel profile is also a factor and has received considerable research across the pond. I refer you to the NMRA website for further information.

 

I think I am correct in saying than Gibson wheels are rather finer and require a slightly greater B2B (intended forEM).

 

Since the advent of Hornby Dublo in 1938, the 'average*' standards have been back to back of 14.2mm with 0.7/8mm flange thickness, with flangeways to suit (wider on the curve than the straight  on Dublo pointwork). Lesser makes had coarser wheels, but adopted these in the sixties. Peco Streamline was intended as a 'universal trackwork' when it first appeared at this time (1963?).

The turn of the century saw Hornby (as in Tri-ang) adopting the BRMSB standards and Bachmann NMRA. Luckily these are are not significantly different and run happily together.

 

* As promoted by the 'Railway Modeller' (For the Average Modeller).

 

I could go on but that's enough Grifone waffle for now! (If anyone's still here!)

 

 

[DCB]

21 hours ago, ikcdab said:

I can only reiterate what I said before.  The b2b is a derivative of the check gauge. Take a spare set of wheels and set them so that when the back of one wheel is just touching the check rail, then the other wheel is just clear of the crossing nose. Then measure those wheels. That is your desired back 2 back 

Yes up to a point. But Points vary.   I prefer to measure a wheelset which has run happily through all my point work as a baseline. As I had several hundred  Hornby Dubo  wheels moulded in one piece as  two wheels plus an axle which ran very nicely I used one of them as a baseline.    From that wheelset I made up a B to B gauge to be a sliding fit and then I measured the gauge.  I wrote 14.25mm on it.  Any wheel set which failed as in was too narrow to gauge was set aside for alteration. Triang and Peco one piece wheels  were binned two piece spaced apart to give 14,25.

Then it became clear Hornby 2000 type wheels with narrow tyres (Narrower than Bachmann) were hitting crossing noses so I made a fail gauge to fit a wheelset which hit crossing noses easing the wheels in until it just hit (rather than ikab's just missed) the crossing nose. I made a sliding fit gauge ( the other end of the 14.25mm tool and measured that at 14.75mm, So now I can quickly check if the B to Bs are too wide or two narrow. I always say if you can easily adjust the wheels to gauge using a vernier caliper you should bin them because they are loose on the axle.

[Il Grifone]

At the price they are today*, binning wheels for being a bit loose on the axle seems a bit drastic. there are various adhesives that cure this failing. Loctite make one specific for the job (usual disclaimer).

 

* I bought quite a lot of Hornby wheels when they first appeared (Nice metal wheels to BRMSB standard on 26mm pin-point axles and correctly a bit over a scale 3' in diameter) at a bargain price of 10 sets for less than £3 (2000ish). at the time, I had pretentions of a layout in EM gauge and promptly regauged them to 16.5mm B2B, so never checked what they started at.  The price has gradually crept up to £15/16 (I have seen £35 or so asked!). I would like to think this is because the Chinese workers who make them are now paid five times as much, but I doubt it.

 

The EM layout fell through - not quite enough space for the generous curves required for scale 3-link couplings - and temporarily became a small shunting layout in 3 rail Hornby Dublo. From there it just grew into the layout I've posted elsewhere (Hornby Dublo Layout). Retirement brought on downsizing....

[Ravenser]

On 19/08/2020 at 15:03, Il Grifone said:

 

13.8 mm is far too narrow and suitable for the old Tri-ang wheels (maybe some confusion arose). up to about 2000, Hornby had been using the old Hornby Dublo wheel standards for which the back to back should be 14.2mm (actually something imperial! 560 thou. IIRC)

 

Just to clear up the confusions:

 

(modern) Hornby used 13.8mm back to back up to around 2000.

They then moved to 14.5mm nominal,

although in recent years some models have used a B2B of 14.2mm (I found that on some Mk3 coaches, and it seems common on the rolling stock wheels sold in packets. I adjust these to 14.4mm using a back to back gauge before using them)

 

Airfix in the late 70s /early 80s used 14.2mm (I have a Class 31 to prove it!)

 

Quote

Since the advent of Hornby Dublo in 1938, the 'average*' standards have been back to back of 14.2mm with 0.7/8mm flange thickness, with flangeways to suit (wider on the curve than the straight  on Dublo pointwork). Lesser makes had coarser wheels, but adopted these in the sixties. 

 

I'm sorry, but this is comprehensively misleading. The "Average" family has 2.4 children, but no real family ever does... During the 20th century there was a jumble of different standards from different manufacturers - in the 1990s Hornby used 13.8mm , Bachmann 14.4mm and Lima 14.5mm and to say that they were working to an "average of 14.2mm" is wholly misleading. Put very simply Bachmann and Lima stock would go through a point built to BRMSB standards and Hornby would jam every time and needed rewheeling.

 

On 20/08/2020 at 22:39, brightspark said:

This why the BMRSB was set up as 00 standards were all over the place.

I am hunting through the old magazines  to find out what they ended up with. But of interest in MRC June 1936, it was determined after some experiments that for 00 = 16,5mm gauge track the BMRSB recommended standards are.

Dimension A (wheel width) 2,25mm

Dimension B (Back to Back) 15mm

Dimension C (Flange depth) 0,75mm

Dimension D (Flange width) ,5mm

The outside faces of check rails should be 14,5mm

The gap between running and check rail should be 1mm

 

Also of interest 19,00mm track, referred to as "true 4mm scale track, the back to back is 17,5mm with check rails set at (outside face) 17mm.

 

 

Brightspark has done some research, and fallen down one of the more curious twists of 4mm history. 

 

The 1936 "recommendations" have nothing to do with the BRMSB as people historically knew it . In 1936 the Model Railway Constructor was a one-man band , and the man was E.F Carter. At one point he was even personally binding the magazines as well as posting them out to subscribers. 

 

The 1936 "BRMSB" seems to have been another pseudonym for Carter - a resounding title under which he could try to push some very finescale standards at the hobby . Really what they probably represent is the aspirations of pre-war finescale HO

 

19mm - now known as "American OO" - seems to have originated in the late 1920s when people realised that 16.5mm gauge was underscale for 4mm scale

 

The actual BRMSB was a wartime initiative, a little cabal of people involved with the then two magazines who tried to clean up the OO standards confusion while the hobby was largely shut down by the war. It ultimately failed because they had no influence over RTR (which they thought of as "the toy trade" , something outside the hobby) and in the end we discovered that 4mm was largely to be driven by accurate RTR ,not by people who made everything themselves at home.

 

For OO the key BRMSB standards were 1.25mm flangeway, 14.5mm back to back, 16.5mm gauge, all nominal. These were first published in the Model Railway Constructor March 1942 - they were slightly elaborated when reprinted as a booklet by the BRMSB in the early 1950s but these key dimensions remained unchanged [ As "the BRMSB" was in fact the editors and proprietors of the magazines, they  clearly had no difficulty arranging for printing and distribution of a booklet...]

 

A detailed account of the wartime BRMSB's activities is provided here: OO 1939-45

 

and there is some discussion of the odd little 1936 episode at the end of the previous "installment"

here

 

[Ravenser]

Returning to Eric Alltorque's original question:

 

Use 14.4mm back to back, not 14.8mm back to back , if using Peco trackwork

 

- Peco Streamline was originally compromised so it would take Hornby's 20th century 13.8mm back to back. This applies to both code 75 and code 100.  The rail section of code 75 is "finer", but the "track standards were exactly the same..... "universal" is actually a polite version of "bastardised"

(for the record Setrack used to be even coarser than Streamline. But it's a long time since I bought a Setrack point - so I don't know if it still is)

 

- Historically Peco have been very coy about telling anyone what the actual "track standard" dimensions of their track are. This allows them to change them when they want, without mentioning it, and allowed the hobby to think that code 75 was "finer" when it wasn't.

 

- A few years ago , someone at Peco indicated to a contact in DOGA that they were likely to tighten up the flangeway on Streamline points as the tooling fell due for renewal, to bring it in line with modern wheelsets, which are basically to RP25/110 - a US NMRA standard, which all the Chinese factories are thoroughly familiar with, and which has therefore become the de facto global standard for 16.5mm gauge

 

- I've no idea whether Peco have actually done this. The place to check would be the new "Unifrog" points which they are rolling out so that retailers no longer have to stock separate "live frog" and "Insulfrog" ranges. Plus, of course, the new Bullhead range. If you were going to "go fine" on any pointwork, that would be the product. (what with lockdown, and the fact I'm not actually building a new layout, and life getting in the way, etc.. I've not actually bought one to check yet)

 

- One awkward fact that nobody ever discusses is the manufacturing tolerances at the factories. It is really rather pointless discoursing about the metaphysical subtleties of the difference between 14.4mm back to back (NMRA) and 14.5mm back to back (BRMSB) when the actual back to backs on a loco from the Kadar factories frequently vary from 14.3mm to 14.5mm on adjacent axles for the same loco! (as you will find they do, if you measure them)

 

Do not ease out any wheelset beyond 14.4mm back to back if using Peco track. Peco Streamline is not designed to work with wide back to backs.

Edited August 22, 2020 by Ravenser

[Ravenser]

Finally , the relevant modern OO standards are:

 

Intermediate or Commercial OO wheel standard   (note that the back to back should be 14.4mm , plus or minus 0.05mm). It is based on RP25/110, so modern RTR wheels should be to this standard. Romford wheels are a near equivalent.

 

Intermediate track standard  (note that "BRMSB OO" track using the traditional "scale" flangeway of 1.25mm is - just - compliant with the outer limits of this)

 

Since Peco Streamline is either coarser than this track standard , or just compliant with the outer limit, don't use finer wheel standards than Intermediate with it

 

Modern commercial wheels are (broadly speaking) to this 

 

OO Fine standards are here:

 

OO Fine track standard  (note the flangeway is as tight as 1.0mm)

OO Fine wheel standards (these are effectively Gibson or Ultrascale wheels)

 

The OO Fine standards originated in the late 1980s - early 1990s. 4mm Finescale modellers of the time felt that the old BRMSB OO standards from the 1940s were a bit coarse and inconsistent. Some therefore thought  a better solution could be arrived at by working back off the 1979 EM standards - effectively an "EM minus 1.7mm" standard (EM gauge is 18.2mm, OO 16.5mm)

 

The main proponents of this seem to have been C+L under their earliest owners . They were making components for EM modellers - an "EM minus 1.7mm" concept allowed them to sell their EM built-up Vs with 1.0mm flangeways to OO gauge modellers.

 

Similarly Gibson and Ultrascale were producing wheels to the 1979 EM profile - they generated economies of scale by selling them to OO finescale modellers as "better" (because finer) than Romfords. To do so, they reduced  the back to back pro rata , from EM's 16.5mm B2B to 14.8mm B2B for 16.5mm gauge. 

 

At some point, Gibson decided to reduce their back to back gauges from 14.8mm to 14.7mm. Of course they didn't tell anyone they were doing this, or explain why....  C+L sold Gibson's B2B gauges to their customers as setting the wheels correctly for the track they would be building.

 

14.75mm back to back is a new one to me..

 

The DOGA OO Fine standards simply codify this practice, so everyone knows what it is and what the values are. The concept was originally developed by people who assumed that modellers would - as a matter of course - rewheel all their locos and build all their own points. If you use Peco track - ignore it

Edited August 22, 2020 by Ravenser