YNWOAN said:
The sub platter i want to drive is 170mm with belt..I was'nt stamping my feet but i was clearly getting no where, but if you feel i was being a bit stroppy, well then it's got me somewhere,as mentioned if i get this problem worked out on the board Crystal it's very helpful to others in the same daunting sitiation..
SY said:
Brainticket, let's keep things civil, especially to those who have given you the means to solve your problem.
Fine SY.These guy have got to remember not everyones as brainy as themselves, this is rather tricky stuff to a newbie...I'm sorry if it's taking so long to sink in but a tad more clarity would'nt hurt would it without being clever, would it Andrew T..?
Brainticket said:
Thanks
Are you then saying that if my platter was 170mm diameter with belt. 170 divided by 7.4925 = a pulley diameter of 22.6mm approx?
Good to get it right as this part of TT design is the most daunting, this being extremely helpful to other.
Hi,
The platter diameter with belt includes two belt thickness, you need one.
So say the platter is 170mm. Belt thickness is 1mm.
Effective platter diameter = 171mm (170 + 2 x 1/2 belt thickness).
Effective pulley diameter = 171mm/7.5 = 22.80mm.
But this includes 2 x 1/2 belt thickness, so diameter = 21.80mm.
This does not include the unknown slip which you can regard as a %.
The above suggests 0.1%. belt slip % you add to the diameter,
i.e. multiply by 1.001 = 21.83mm.
Not taking the belt into account above you get 22.67 and 22.7mm.
This shows that its at the pulley end where the belt thickness
makes the most difference to the effective diameter, regardless of
what has been stated above it not "obvious" that you cannot just
treat the drive system in terms of the belts inside surface.
The above numbers suggest the simple calculation will run 4.5% fast.
However I suspect the effective diameter of a crowned pulley is
not its actual diameter, that is the crown causes belt slip much
higher than the nominal 0.1% given above.
As ever some practical experience and measurements would help.
/sreten.sreten said:
The 0.1% is belt creep NOT belt slip. Slip can be cured, creep cannot (the belt must creep to transmit torque).
In my experience with DC motors the diameter at the crown is the drive diameter for the pulley if it is correctly aligned.
We seem to have lost the somewhat mis-monikered brainticket.
sreten said:
Hi,
The platter diameter with belt includes two belt thickness, you need one.
So say the platter is 170mm. Belt thickness is 1mm.
Effective platter diameter = 171mm (170 + 2 x 1/2 belt thickness).
Effective pulley diameter = 171mm/7.5 = 22.80mm.
But this includes 2 x 1/2 belt thickness, so diameter = 21.80mm.
This does not include the unknown slip which you can regard as a %.
The above suggests 0.1%. belt slip % you add to the diameter,
i.e. multiply by 1.001 = 21.83mm.
Not taking the belt into account above you get 22.67 and 22.7mm.
This shows that its at the pulley end where the belt thickness
makes the most difference to the effective diameter, regardless of
what has been stated above it not "obvious" that you cannot just
treat the drive system in terms of the belts inside surface.
The above numbers suggest the simple calculation will run 4.5% fast.
However I suspect the effective diameter of a crowned pulley is
not its actual diameter, that is the crown causes belt slip much
higher than the nominal 0.1% given above.
As ever some practical experience and measurements would help.
Thanks Sreten you are extremely helpfull.Now all this has sunk in.Does the calculations stick if using a 300rpm motor instead of 250rpm?
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