From: noel shelley (noel@shelley1722.freeserve.co.uk)
Date: Sat Mar 13 2004 - 07:04:26 PST
> Dear Fred and List,
> Further to your question on the length of
> brake shoes , enquiries to one of the leading manufacturers has resulted
in
> following answer ! The lining length will be arrived at using various
design
> criteria and also the preferences of the individual designer .
> Obviously weight , speed , type of usage , operating environment , drum
> size , and lining material type will all be factors . The leading shoe in
> forward motion may be longer and also thicker since this shoe will do
most
> of the braking , with factors of 3 or 4 not uncommon over the trailing
shoe
> ,{single leading configuration }, meaning that a twin leading set up in
> reverse may only have 25% of it`s forward efficacy .
> Another point worthy of note in the context of braking is the principal of
> weight transfer and it`s effect on stopping the machine . Under braking
the
> load on the front wheels dramatically increases resulting in the front end
> doing about 75% of the retarding , obviously if the balance of front to
rear
> is not correct then a very dangerous situation is created where one end
will
> lock up . In commercial or load carrying vehicles where the load varies
this
> is often compensated for by using a load sensing valve on the rear .
> To sum up , there is no simple answer to the initial question !
>
> Done my best Noel
>
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