Static Motor Speed Under Dynamic Load

Click For Summary

Discussion Overview

The discussion centers around selecting an appropriate motor for a project that requires maintaining a constant speed while managing a dynamic load ranging from 20 to 500 lbs at a speed of approximately 1 ft/sec. Participants explore various motor types and their suitability compared to hydraulic systems.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant questions whether a motor is the right choice or if hydraulics should be considered for the project.
  • Another suggests that AC induction motors maintain a fairly constant speed, while brushless DC motors can achieve constant speed with electronic speed control and are lighter.
  • A participant inquires about the weight of the DC motor and its ability to handle the maximum load of 500 lbs.
  • It is noted that to achieve the required speed of one foot per second, the motor will need to be geared down, with a power requirement of approximately one horsepower.
  • One participant mentions that many industrial motors can handle fluctuating loads while maintaining constant speed, emphasizing the importance of the motor and controller combination.
  • Another participant discusses the use of flywheels for energy storage in motors that drive fluctuating dynamic loads, comparing this to hydraulic systems that utilize accumulators for energy storage.
  • A specific example is provided of a DC brushless motor that can deliver one horsepower, but it is noted that it is not inexpensive and will also require gearing down.

Areas of Agreement / Disagreement

Participants express differing opinions on the best approach, with no consensus on whether to use electric motors or hydraulic systems. The discussion remains unresolved regarding the optimal motor type and configuration for the specified application.

Contextual Notes

Participants have not reached a conclusion on the specific motor type or configuration, and there are uncertainties regarding the weight and load capacity of the proposed motors. The discussion also highlights the need for further exploration of power requirements and gearing options.

omalleyt
Messages
15
Reaction score
0
Hi. For a project of mine, I need a motor that can dole out and pull in a wire at a constant speed under a dynamic load. The load will be anywhere between 20-500 lbs. The speed will be about 1 ft/sec. Any idea about how I can achieve this effect? Is a motor even the right way to go or should I be looking at hydraulics? Thanks for any help!
 
Engineering news on Phys.org
I have a suspicion weight will be an issue.

AC induction motors turn at fairly constant speed. But a brushless DC motor can be made to rotate at a constant speed using an electronic speed control and is far lighter.
 
How much (approximately) would the DC motor weigh, and would it be able to withstand the 500lb load?
 
At one foot per second, the motor will need to be geared down. The question is not how much weight, but how many horsepower. This happens to be one horsepower, or a little more, for your one foot per second requirement.
 
Many industrial motors can operate on this kind of condition. For example, think of a motor on a lathe. The loads are drastically changing but the speed remains constant. The combination of motor and controller will dictate how the motor runs.
 
Some motors driving fluctuating dynamic loads use large flywheels as temporary energy storage to smoothe out the torque requirements; e.g., air compressors. For larger energy storage, hydraulic systems use compressed air reservoirs.
Bob S

[edit] The reservoirs are actually called accumulators. They have a bladder in them to prevent direct contact between air and fluid.
 
Last edited:
You can get one horse power out of an outrunner DC brushless motor 2" diameter and 2" long. It isn't cheap, and will need to be geared down like any other motor selection. If affordable, it would be the way to go to cable lift for the batman thing.
 

Similar threads

Replies
24
Views
3K
  • · Replies 2 ·
Replies
2
Views
5K
  • · Replies 3 ·
Replies
3
Views
2K
Replies
13
Views
4K
  • · Replies 19 ·
Replies
19
Views
4K
  • · Replies 15 ·
Replies
15
Views
4K
Replies
6
Views
2K
Replies
6
Views
5K
Replies
14
Views
3K
Replies
34
Views
5K