Axle bearing end float

[ron]

I finally got a set of horn castings, and as I've nearly finished the BFW pump I think I'll have a go at them next rather than the cylinders.
The question I have is, once the wheels, axles and bearing blocks are fitted into the horns how much side float should I aim for between the wheels and the bearing blocks, should I try to get this to an absolute minimum or is there a recognised amount of float to aim for?
Ron

[greasemonkey]

Hi Ron
I aim for a 'rattling good fit'. If you machine everything to fine tolerance then it binds up on our less than perfect model tracks

Andy

[John Lee]

Ahhh, I notice you have nearly finished your pump Ron

;D

Regards,

John

[ron]

Andy, excellent, rattling good fit is something I do well. ;D

John I'll post a pic of the pump when it's finished, there is more work in it than there is in some Stuart Turner engines

Ron

[RobinS]

Acording to the drawings published in M.E. in 1967 the end float for Simplex wheelsets is as follows;- Dimension over frames is 4 7/16" plus 3/16" for 2 axle box flanges = 4 5/8". With a back to back wheel dimension of 4 11/16" this gives 1/16" end float. The drawing indicates that the trailing axle box flanges be reduced in thickness by 1/64" which would give 3/32" end float for the trailing axle only.
Super Simplex published in 1989 gives the end float for the leading axle as 1/32",the driving axle as 1/16" and the trailing axle as 1/8". It would appear that the clearance to the crosshead from the leading axle crank pin and coupling rod is rather tight, hence the reduced float on the leading axle.