mousetail wrote:Stefan, let me ask you a question.

If the spring were replaced with a much, much weaker one, would operating the lever stress the grouphead bolts less or the same?

Less of course because u would only need a weaker force to pull the lever....

13thfloorelevators wrote:Less of course because u would only need a weaker force to pull the lever....

Thanks. So would you also say that the downforce at the roller bearing is in some way related to the strength (elastic modulus) of the spring?

of course...cause the downforce on the lever has to generate INTERNAL force needed to cock the spring...

13thfloorelevators wrote:of course...cause the downforce on the lever has to generate INTERNAL force needed to cock the spring...

OK. And, bearing in mind Newton's 3rd law, where is the equal and opposing force to your INTERNAL force acting?

mousetail wrote:OK. And, bearing in mind Newton's 3rd law, where is the equal and opposing force to your INTERNAL force acting?

just internal of the lever/group assembly, u dont have to think about it when u just look at the bearing situation where the group is mounted on the frame. the force applied on the lever is as big as needed to generate an equilibrium with the spring force (taking the lever arm into account), but when u look at the assembly of the grouphead to the frame thats not of interest!

please just believe me or else will u take responsibility if anyone damages his coffee machine due to your method? maybe someone with a better english can explain it better here, but i guess even then its hard for people without mechanical background to understand.....take a look at my sketch where i sketched the moment and the shear load ....

cheers,
stefan (structural engineer)

Thanks, Stefan, you've been a tremendous help.

I can't believe how lucky I've been in the past two years, and I guess I'll just keep my fingers crossed that my luck holds as the decades roll by...

cheers
Bob

mousetail wrote:Thanks, Stefan, you've been a tremendous help.

I can't believe how lucky I've been in the past two years, and I guess I'll just keep my fingers crossed that my luck holds as the decades roll by...

cheers
Bob

yeah, hopefully. would be a pity about your machine...maybe ask user peacecup what he thinks about your method (site 2 of this thread)....tried my best to explain it, but i think im wasting my time at the moment...

cheers,
stefan

gleichfalls!