Why does the 3-part train wheel have one wheel without the flange?

Comments

• madforLEGO Member Posts: 10,837

  October 2020 edited October 2020

  Well IIRC that the middle wheel for LEGO design was to float over the rail as the train set that it initially came with ( #10194 ) had to float over the track around a curve or risk derailing the train from a standard LEGO curve.
  

  

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• 560Heliport Member Posts: 4,269

  October 2020

  Yes, Lego train track curves are much sharper than real railroad tracks.

  

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• scottdd2 Member Posts: 170

  October 2020

  I can't get to my 10194 at the moment but I think that if the center wheel had a flange as well then it wouldn't fit between the 2 outer wheels as they are set close together.

  

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• 560Heliport Member Posts: 4,269

  October 2020

  ^ Good point! I have #75955 Hogwarts Express, same issue.

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• Paperballpark Member Posts: 4,270

  October 2020 edited October 2020

  It's actually quite accurate: https://en.wikipedia.org/wiki/Driving_wheel#Flangeless_wheels
  
  'Flangeless wheels

  Some long wheelbase locomotives (four or more coupled axles) were equipped with blind drivers. These were driving wheels without the usual flanges, which allowed them to negotiate tighter curves without binding.[9]
  
  Some three-driving-axle locomotives also had flangeless wheels on the middle axle , eg the NZR WH class.'

  

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• Switchfoot55 Member Posts: 3,485

  October 2020

  I appreciate this question being asked as I've always wondered what that extra wheel was in my #10254 Winter Holiday Train. It's clearly not included in the instructions. I was always afraid I was missing something. 
  
  For the Winter Holiday Train, is there a way to use the flangeless wheel in the original design? Or, would one need to increase the length of the engine and add another wheel for that to work? It appears I would also need some thin technic lift arms to accomplish the intended result. 

  

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