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The back - back on my bachmann 37 seems in general to be around 14.2 mm. #
I thaught a general rule was the B- b should be about 14.8?

I have a back - back guage (got two actually as lost one then found it when another was baught!) and this is 14.8.
Now I am getting the odd loss of pick up in pointwork where it seems the bogie needs just a tiny prod to pick up current again, I am beginning to thing the b-b is too short on the 37?
 

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If it is staying on the rails I wouldn't begin with b-t-b. For hesitation on points from a twin bogie pick up diesel, the first thing to check is the continuity of all the electrical paths from wheel tyre through to motor terminal. With at least four wheels picking up on each of the bogies, stalling on pointwork should be near impossible...
 

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I don't know if this is a practical proposition with diesels, but I use my rolling road rollers to check the pickups on my steam locomotives. I set it up so that the power is going through just one set of rollers and run at slow speed. When the motor stalls, I use a flying lead to "skip" the wheel contacts in turn. This helped me identify some invisible oxide on some wheel backs.

David
 

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QUOTE (Piemanlarger @ 19 Dec 2007, 19:39) <{POST_SNAPBACK}>The back - back on my bachmann 37 seems in general to be around 14.2 mm. #
I thaught a general rule was the B- b should be about 14.8?

I have a back - back guage (got two actually as lost one then found it when another was baught!) and this is 14.8.
Now I am getting the odd loss of pick up in pointwork where it seems the bogie needs just a tiny prod to pick up current again, I am beginning to thing the b-b is too short on the 37?

***You are right about the fac that the BTB is too narrow, and if you can tweak the wheels out to 14.7~14.8 you will get a better running locomotive.

I do this on all my stock and loco's, even having gone to the trouble of having square holed washers etched for my Markits/Romford axles to move the wheels from the standard markits 14.5 to 14.8~14.85.

Many modellers are skeptical about the benefit of this, but it sorts out many problems and the improved running, even through RTR turnouts is remarkable.

Having said that I do agree with other advice on tweaking pickups and removing the blackening from pickup contact areas... Often pickup problems are just due to careless assembly of the loco.

A surface treatment of pickups and wheel surfaces with Deoxit or Gold (usually available from better hi fi or electronics stores) will also do wonders for pickup quality.

Kind regards and best wishes for a happy Christmas and a New year full of smiles

Richard
DCCconcepts
 
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