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TT:120 Back to Back / Gauge setting


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a couple of weeks ago I made a video on why ‘gauge’ matters for reliable running, how you can set it correctly and why it sometimes comes ‘undersize’. A few people have mentioned it recently so though it was better to have it as its own thread to help people find the information. 
Purely by chance I found a set of pliers that had the right sizing to give me the optimum setting. A few others have not been that lucky, so here is an alternative. 
If you search for ‘Pin Gauge’ you can find a company who make precision ground calibration tools and these are available in 10.4mm diameter which will help set the wheel back to back. Ideally a Slip Gauge would be used as it’s a block rather than a rod but these are not made to 10.4mm. The end of the Pin Gauge can be used to push between wheel backs for an accurate setting. The DCC concepts gauging tool is 10.2mm and so does not help eliminating running issues in most cases. 

 

 

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Hope the pliers give the right gauging, I wouldn’t expect a noticeable difference on same product but just in case I have found an alternative as mentioned. The pin gauge means people don’t need to worry about having accurate measuring tools as the gauge itself is precision ground. 

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They are working great, have you come across where the screw that goes into the nut in bogie is stuck? It turns and the bolt drops out but then it won’t move anymore. It needs fixing as the washer is at the bottom. @Peachy  

Fixed Scotsman he now runs perfectly at slow (15) mid (50) and high (70) through all my curves and points. 

Now on to William Whitelaw for his bogie service, tbh he runs great atm.

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If the captive nut has come out that means the pivot bolt must have unthreaded sufficiently, if you unwind it gently and apply a little pressure to the (nut) end of the bolt it should come free. It’s probably the plastic washer that is holding the bolt in place. There are no threads in the bogie casting so nothing to damage in there 

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8 minutes ago, Rallymatt said:

If the captive nut has come out that means the pivot bolt must have unthreaded sufficiently, if you unwind it gently and apply a little pressure to the (nut) end of the bolt it should come free. It’s probably the plastic washer that is holding the bolt in place. There are no threads in the bogie casting so nothing to damage in there 

Thanks will give that a try on Thursday on my day off.

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Try and watch closely and see if the rear set of bogie wheels are coming in contact with the leading set of driving wheels. Careful adjustment of the bogie bracket will get that sorted. 

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19 minutes ago, Rallymatt said:

Try and watch closely and see if the rear set of bogie wheels are coming in contact with the leading set of driving wheels. Careful adjustment of the bogie bracket will get that sorted. 

Thanks it’s the front bogies that seem to be the problem, I am sure I will get it sorted, have to get the phone camera and do some recording me thinks

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On 01/04/2024 at 10:33, Postman On The Rails said:

Very apt as I am about to take a look at my scotsman as it is having issues, I managed to get the pliers from Amazon 

I think I must have the worst luck ever with those pliers ! the first single one I ordered a while back was 9mm, so was returned. I just got the set linked (well their was a link, not sure where it went !) and they are a shade under 10mm, but as this was a set of 3 (long nose and wire cutters) for under a tenner I'll keep 'em 😁

I think I'll print myself a B2B gauge !

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  • 2 weeks later...

Thank you for your post.  I am currently building a TT layout and have had running issues with the William Whitelaw A4.  It is a lovely loco however it can derail over points, particularly on reverse.  Also as it was going round curves it would slow very slightly as it passed over fish plates.  Clearly something was causing it to drag.  I purchased a TT back to back gauge from DCC Concepts and found the gap in the tender wheels was too large.  I gently closed the gap in each set of wheels to match the gauge.  It resolved the problem amicably.  However, the bogie wheels do make contact with the front driving wheels.  The inside set of wheels going around the curve are raised off the track by about 3 or 4 millimetres.  This does not happen with my A1.  The bogie does make contact with the front driving wheel.  I shall try your fix.  I have had the bogie off, although I have not dismantled it.  I did note the washer was not in the same place as yours in the video.  I assume therefore it had not been assembled properly in the factory.  I am hoping your suggestion will work.  Thank you.

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26 minutes ago, Muhammad-354651 said:

However, the bogie wheels do make contact with the front driving wheels.  The inside set of wheels going around the curve are raised off the track by about 3 or 4 millimetres.  This does not happen with my A1.  The bogie does make contact with the front driving wheel.

Check the bogie mounting arm, it must be tight and dead straight. If it is angled sideways at all, even a slight amount, the bogie wheels will catch the front drivers.

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I would avoid setting the back to back to the DCC Concepts gauge as it is the absolute minimum for TT (10.2mm)  a slightly wider setting of 10.4 seems to remove the majority of running issues and Hornby stock seems now to be coming set at that spacing from the factory in most cases. 
Work through the different solutions in the video and let me know how you get on. As Silver Fox says, setting the bracket on the front bogie is a good place to start. 

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On 05/04/2024 at 13:35, Rallymatt said:

Try one of these

https://www.ebay.co.uk/itm/284318561567?mkcid=16&mkevt=1&mkrid=711-127632-2357-0&ssspo=r1kfqhqZStS&sssrc=4429486&ssuid=Q02lvap8QMe&var=&widget_ver=artemis&media=COPY

you can get a 10.4mm one (or tiny increments either way) 

A printed one will squash and change size in heat 

For some reason the 10.4mm are out of stock so went for 10.39

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