Originally posted by BobZilla
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I am not commenting on Johns manual that was mentioned, I haven't read it. To answer the question freeenergy asked
The sweet spot is easy once you understand what you are looking for. Some will start slow and work up, others will start fast and work down, but here is what you are looking for and an easy way to find it.
Connect an analogue current meter from the primary, use a digital if that is all you have.
Get your machine running and going FAST (low resistance on pot). Later you do not need to do this as it will waste a little energy and you will know where to dial in from going through the procedure, but for learning this is an easy way.
Once the RPM's are fast and steady start to back you pot down a little at a time, wait for the RPMs to settle at each adjustment. The wheel needs to catch up to your adjustment before making another adjustment.
As you back down(add more resistance on pot) you will find a spot where your input current drops back significantly, disproportional to the small amount of adjustment you have made. If you turn it back up slightly again the draw shoots back up, back it down to make sure you have found the spot. This is the sweet spot. You are getting pretty much the same RPM for less input. There is more than just one sweet spot but you need to learn to find at least one of them and the one at the top (closer to really fast) is easier to find.
For example lets pretend you are pulling 1amp at full speed, you back down a little and now it is .95, a little more and .80, a little more and .65 hey that was a big jump,, go back up again, .84,, ok now back again, .64 OK this must be the sweet spot.
You have probably observed the sweet spot while spinning up your machine. Watch the amp draw as it spins up. It will "shift gears" and the input current will go high then drop off. Most machines will do this a few times as they get up to speed. When you see that you are seeing the machine go through the sweet spots. WHat you are trying to do is dial them back in and run there.
Do you understand? You are looking for the spot at which you are getting the same spin for less input. Most of the time the pot and input will be directly proportional but when you identify a sweet spot a tiny adjustment on the pot = a big decrease on input. ---Bob
The sweet spot is easy once you understand what you are looking for. Some will start slow and work up, others will start fast and work down, but here is what you are looking for and an easy way to find it.
Connect an analogue current meter from the primary, use a digital if that is all you have.
Get your machine running and going FAST (low resistance on pot). Later you do not need to do this as it will waste a little energy and you will know where to dial in from going through the procedure, but for learning this is an easy way.
Once the RPM's are fast and steady start to back you pot down a little at a time, wait for the RPMs to settle at each adjustment. The wheel needs to catch up to your adjustment before making another adjustment.
As you back down(add more resistance on pot) you will find a spot where your input current drops back significantly, disproportional to the small amount of adjustment you have made. If you turn it back up slightly again the draw shoots back up, back it down to make sure you have found the spot. This is the sweet spot. You are getting pretty much the same RPM for less input. There is more than just one sweet spot but you need to learn to find at least one of them and the one at the top (closer to really fast) is easier to find.
For example lets pretend you are pulling 1amp at full speed, you back down a little and now it is .95, a little more and .80, a little more and .65 hey that was a big jump,, go back up again, .84,, ok now back again, .64 OK this must be the sweet spot.
You have probably observed the sweet spot while spinning up your machine. Watch the amp draw as it spins up. It will "shift gears" and the input current will go high then drop off. Most machines will do this a few times as they get up to speed. When you see that you are seeing the machine go through the sweet spots. WHat you are trying to do is dial them back in and run there.
Do you understand? You are looking for the spot at which you are getting the same spin for less input. Most of the time the pot and input will be directly proportional but when you identify a sweet spot a tiny adjustment on the pot = a big decrease on input. ---Bob
Sweet has no place. 
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