Abstruse CSB Theory

[Alan Turner]

As you are probably aware my version of the spreadsheet works in a different way to that of Will's in that my sheet imposes an equal deflection to all axels and then calculates the resulting axel load. The percentage, relative to total unsprung model weight, is also calculated. In addition to that the calculated Cof Action is graphically compared to the CofG of the model. There is always a solution of suspension points (within reason) that will ensure that the actual CofG of the model will be coincident with the suspension Cof Action.

However there is one underlying principal that applies to all the spreadsheets and that is they provide a static solution to the weight distribution. They do not and cannot provide a dynamic solution to the chassis. It is quite possible (probably?) that the dynamic performance of the chassis will not match the static weight distribution. The more difference that exists between the "spans" of the various spring sections the greater the difference between static and dynamic performance will be.

In model terms I don't think the above maters in the slightest.

Regards

Alan

[Chris Mitton]

Will - some of your comments imply aiming for an equal weight distribution across all axles - but this is impossible unless the wheelbase is symmetrical (the J15 isn't) - simple consideration of moments about the centre axle will show that.

Sorry Chris but this is not true

Hi Will
On reflection I realise I'm talking gibberish and you're probably right....of course the moment of the front-axle-weight about the centre axle (or anywhere else!) isn't cancelled out by the moment of the back-axle-weight, it's cancelled out by the equal-and-opposite reaction of the rails on the wheel that I'd forgotten about, so the axle loads don't have to be different, or the same for that matter. Another senior moment!

many people already think it a bit complicated but if anybody is interested....

....I'm interested even if no-one else is!

Regards
Chris

[Russ Elliott]

I've added a cell (M58) to Roger Wyatt's spreadsheet to show the model CofG location derived from the input model axle weights and wheelbase.