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Originally Posted by Jeremiah H
Looks great. We're going to try to implement such a system on our custom gearboxes, so I have a couple performance questions:
-How long does it take to shift? (and what is the throw in that time period?-ours needs about 1 1/2" travel in as little time as possible)
-I don't know a lot about servos, so could a longer arm on the servo be used to decrease shift time? Would the servo be strong enough?
-How long could said arm be before the servo wouldn't have enough power to shift? Thanks. -JH
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The Acroname page for this product gives good specs:
60 degrees of throw in 0.19 seconds
41.6 oz-in of torque.
The servo arm has about 3/4" distance from the center of rotation of the servo out to the shift shaft. So, this translates into 55.4 ounces or ~3.46 lbs of force. This force is adequate, but it definitely does not give an immediate shift like a pneumatic cylinder does. If the arm was made longer, then the force of the servo arm would be less. I suggest not making your arm any longer.
As for shift time, the 0.19 seconds is the length of time it takes for that arm to swing 60 degrees. However, don't expect your gearbox to switch in exactly that amount of time. The first 0.1 seconds will remove the dog gear from where it was mated and then it will try to engage the other gear. Since the arm is pushing with only 3.4 lbs. of force, the engagement will not happen as quickly as it would if it was being pushed by 20 lbs from a 3/4" bore air cylinder. It may take longer (up to a full second or so) for that shifting dog gear to line up and slip into the mating dogs on the other gear.
Like any engineering decision, there are trade-offs here. For the benefit of giving up pneumatics, you are paying the price in having a lower force shifter that may take longer to engage and complete a shift.
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Originally Posted by Justin M.
Looks great.
Two years ago we built and installed custom servo shifting gearboxes with the DeWalt motors and casings in our robot...so much torque that it bent the chassis - we had to switch out for the standard FIRST gearboxes with CIM's.
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Yep, servo shifters have been utilized for a few years. We (team 45) had one in 1999 and then decided to publish a
Servo Shifting Gearbox whitepaper in the summer of 2000.
Back then, the gearbox had to stop before the servo would shift. With the above design, the dog gear can just slam back and forth all day between the two gears, not caring what the motor speed is. Today's robot drivers have it pretty good.
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Originally Posted by Billfred
Is anyone else getting a 404 for the Gifts page?
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Yep... me too. grrr.
Andy B.