I am designing a machine where I need two 3/4HP / 500W motors powered from 110VAC to run in opposite directions, at precisely (+/- 0.3% perhaps) the same RPM, controllable from zero to 5000 RPM by a dial or pedal or other control. The loads are the same, and gears are probably not practical at the form factor (6" wheels 3" apart) and RPM. I don't need computer control, positioning, or major telemetry, I do need a way to know what RPM they are running. What is a good way to handle this economically?
$\begingroup$
$\endgroup$
5
asked Jan 22, 2021 at 4:00
-
1$\begingroup$ Sounds like a job for something like 500 W e-scooter motors and their ESCs. You should be able to set the speed perfectly precise then. $\endgroup$– toweJan 22, 2021 at 5:43
-
$\begingroup$ the missing information is what these motors are driving: If the loads are unequal between motors and over time it will very hard. Also what is the actual problem, why not a gear etc. $\endgroup$– martJan 22, 2021 at 7:07
-
$\begingroup$ Thanks! The loads are the same. It's two rotary elements about 6" in diameter, separated by about 3"; the design has to be able to handle 4500 RPM max, so at that size I have been thinking gears are probably not practical though certainly possible. I am not free to discuss the nature of the loads at this time :-) $\endgroup$– Jonathan Brickman of Topeka KSJan 22, 2021 at 11:40
-
$\begingroup$ With encoder to sense speed you could do it electronically, but the response of one vs the other, to load change etc, would be tricky to synchronize. If you can accept slow acceleration, then can add inertia for this. If matching is more important than speed accuracy, i would also suggest looking at a mechanical solution. $\endgroup$– Pete WJan 22, 2021 at 17:18
-
$\begingroup$ I have been looking at certain precisely RPM-controlled brushless servos which are steadily replacing traditional motors in industrial sewing machines. I'd love to find a way to sync two of their ESCs. Certainly drones are doing a more complex RPM synchronization, of not entirely dissimilar kind, very effectively. e-scooter motors do sound like just the thing, if I could power them with 110VAC. I have contacted a few servo distributors, but depending on costs, I may go with e-scooter parts and batteries. $\endgroup$– Jonathan Brickman of Topeka KSJan 24, 2021 at 0:56
Add a comment
|
2 Answers
$\begingroup$
$\endgroup$
1
Connect them with gears and they will run at the same speed - any sensor / control will have an accuracy range
answered Jan 22, 2021 at 5:49
-
$\begingroup$ True. But large gears at high revs is expensive or risky. $\endgroup$ Jan 24, 2021 at 0:57
$\begingroup$
$\endgroup$
2
As a mechanical alternative to gears, perhaps a double sided timing belt could be used to reverse direction and have essentially perfect sync.
-
$\begingroup$ Indeed, a serpentine double timing-belt method is one of the options being kept on the possibles list. It does tend to throw off symmetric balance, but this can be corrected. Still not sure about doing this above 3000 RPM. $\endgroup$ Jan 24, 2021 at 1:00
-
$\begingroup$ @Jonathan Brickman - yep, it is harder at high RPM, but the same is true of gears and chains. Automotive timing belts are designed for the full engine RPM range, from what I understand. The caveats are details of the tensioning mechanism and vibration. I haven't ever had occasion to use a double sided one, but this sounds like it could be... $\endgroup$– Pete WJan 24, 2021 at 18:45