Getting your CSB loco sitting level and the buffer heights right

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Will L
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Joined: Sun Jul 20, 2008 3:54 pm

Getting your CSB loco sitting level and the buffer heights right

Postby Will L » Thu Jan 18, 2018 8:03 pm

The question of how you go about getting a CSB loco sitting level and with the correct buffer height has come up elsewhere on the forum. I’ve come up with a quick summary, but, rather than lose it at the end of another thread, I’ve put it here were we can all find it easily.

Firstly, remember that a CSB chassis will automatically sit levels, so long as it is built in accordance with the fulcrum locations plot from the spread sheet, and the Loco Centre of Gravity (CofG) is where the spread sheet said it should be. However, the fit of the body to the chassis can affect the apparent level and buffer height of the finished loco. The routine for building a CSB fitted loco that sits level and with the right buffer heights is as follows.

  1. Design the CSB chassis using the spread sheet, or, ask your friendly CSB expert (who will consult the spread sheet for you)
  2. Try and sort out the chassis body interface before construction starts based on a good drawing and how the chassis will fit the body. This isn't final but should avoid major surgery later.
  3. Build the chassis. I like to fit the chassis with the stiffest possible wire that will fit through the fulcrums (usually 20 thou) so the wire doesn't really bend at all under the weight of the bare chassis. It should sit with all wheels touching on the traditional sheet of glass, proving you've built it flat and square. Don't expect that fitting CSBs will make up for a badly out of square chassis.
  4. Track test the bare chassis, it should run without problems round your test track (which will have a curve set to your minimum permitted radius, wont it). If it falls off at this stage it almost certainly isn't the suspension at fault.
  5. Build the body. Check the fit of the chassis. Check the obvious parallels (that the axle centre line and the foot plate) are parallel. Check the chassis works when inside the body, and there is sufficient clearance for wheels and motor to move with the suspension.
  6. Weight the body to get the CofG in the designed position. Weigh the body and chassis (perfectionists will do this without wheels and motor) and use the spreadsheet to work out the right wire size. Fit CSB wires of that size.
  7. Assemble body and chassis and check if the loco sits level and at the right height.
  8. If it does not sit level, adjust the chassis/body fit till it does.
  9. If the buffer height is wrong and it is marginal (+-0.1mm either way) change the wire size up or down to suit.
  10. If the buffer height is wrong by more than that, adjust the body/chassis fit and re do steps 5 and 7 onward. (And don't forget the possibility that the buffers can be in the wrong place)

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