8
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Accepted
Harmonic drives in hobby projects
The core reason for choosing harmonic drives is desire for zero backlash. Moreover, regarding mass and size, they become more beneficial for higher gear ratios as their size and mass do not scale for ...
- 562
7
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Motor Choice given size constraint and load requirement
If you have some budget for your project, both Maxon and Faulhaber have good DC motors and motor-gearhead combinations.
Maxon publishes a nice set of formulas and background theory on electric motors....
- 4,385
6
votes
Motor Choice given size constraint and load requirement
20kg is a mass. It makes a force on Earth (20*9.81 = 196N), but that's not a torque. Motors make torque - what is your maximum torque specification?
Once you know how much torque you need (that will ...
- 16k
4
votes
Lifting robotic leg with only one servo
Going forward, a Klann linkage has a near-vertical leg drop action. (See the legs at left in the wikipedia animated GIF.)
It has a near-vertical leg lift action if running in reverse. (See the legs ...
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3
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Harmonic drives in hobby projects
It is also worth thinking about why you want to minimize backlash. Is it something intrinsic to the task your arm needs to perform?
Industrial robots use these drives to minimize backlash ...
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3
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Harmonic drives in hobby projects
Two parts:
a) If we take into account the cost of harmonic drives and the fact that hobbyist projects aren't intended to make money (no revenue in return), harmonic drives aren't feasible at all for ...
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3
votes
Accepted
What is the torque transmission efficiency using a bycicle chain/setup for robot?
I agree with @Andy 's answer, that chain efficiency is over 90%. I'll point out that your terminology is not quite right - using bicycle chain (or any other transmission) affects power transmission ...
- 16k
3
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Suitable gear construction for a robotic extender - plastic?
I've done a couple worm drive designs and I threw the numbers you gave (Assuming sd-spi nylatron gears) into my calculations.
I'm using AGMA 6022-C93 Worm gear design guidelines for tooth width and ...
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3
votes
Suitable gear construction for a robotic extender - plastic?
What's the point of the middle gear? It's not doing anything for you reduction-wise because it's on a different shaft than the larger gear.
There's an equation here that should give you the maximum ...
- 16k
3
votes
Accepted
Robot mechanism parts names
This is called a Stewart platform. You can use any linear actuator type, hydraulic, pneumatic or electric.
- 491
2
votes
Attaching a M5 screw shaft to a cog wheel
A full answer depends on what plastic and what the load will be. Having a depth of 30 mm does give you a lot of options.
You can drill and tap ABS just fine, and I've had success drilling and ...
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2
votes
Accepted
Lifting robotic leg with only one servo
The linkages suggested by jwpat7 are great, and I would probably prefer to use something like that. But, if you want something really simple, then you might be able to get away with a four-bar linkage ...
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2
votes
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Is this supposed to be a bearing?
A shaft stopper like that is made to let you assemble the device more precisely. The bearings look like they are in the "Tail Gear Case Plate" subassemblies. By using a shaft stopper you can insert ...
- 4,386
2
votes
What is the torque transmission efficiency using a bycicle chain/setup for robot?
From a cyclists' perspective - a good modern bike chain transmission is very efficient - percentage efficiency is somewhere in the high 90s and has been for decades.
(From anecdotal evidence: endless ...
- 1,041
2
votes
Motor Choice given size constraint and load requirement
Thanks for the suggestions guys. I'll consider your suggestions and give an update once I have chosen a motor.
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2
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Motor Choice given size constraint and load requirement
Approach 1: based on the total weight and how steep a slope you would expect it to climb, calculate the power required. (Basic physics)
Approach 2: draw a diagram of the wheel size you'd like to use, ...
- 1,041
2
votes
Accepted
Mounting gear on a servo
The attachment of something that's screwed in is not so much the screw, as it is the friction between the material around the screw (the "faying surfaces.")
If you have good friction, and the load/...
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2
votes
Accepted
What does the number of teeth in a gear determine (when meshing identical gears)?
So, assuming that the more teeth that there are, the smaller the teeth become (and logically for gears with few teeth, the bigger the teeth are):
Big teeth:
Capable of handling higher load
Capable ...
- 1,437
2
votes
Accepted
Stepper drive resolution
G'day,
For question 1, your knowledge of the standard convention for notation is correct. However, it's worth noting that the listing for the gearbox ratio isn't 1:64, it's 1/64, which is a slightly ...
- 46
2
votes
Accepted
Stepper Motor: Direct Drive vs. Belt Drive vs. Geared Stepper Motor
Vibration is a matter of optimal motion control problem, not the type of motor that is used (as long as you used more than 16 micro steps for your steppers). You already used AccelStepper which is the ...
- 1,527
1
vote
Accepted
Driving a gearbox with another?
I think that on the attached picture, the two things from the right, are a stepper motor and encoder. Notice that both have wires coming out of them. So it is not an example of two gearboxes in series....
- 953
1
vote
Making a motor controlled joint passive
Depending on the motor type, you may be able to freewheel the motor. With a brushed DC motor this could be achieved with most commercial H-bridges, controlled with fast current decay.
Flyback diodes ...
1
vote
motor controlled lazy susan
You can design, or purchase, a simple rotary table. I have used Arrick robotics over the years, and they have a relatively turnkey system for $300 here: https://www.arrickrobotics.com/rt12.html
If ...
- 4,386
1
vote
Why are strain-wave/harmonic gears used in robots?
Strain wave gears have practically zero backlash and high torque density (i.e. torque per unit weight) compared to other solutions available. Gearbox weight is important in articulated arms, since it ...
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1
vote
Accepted
Increasing Torque by either doubling servos or building a gear box
Installing a second servo for moving the same axis might be problematic from a controls point of view. Since (I assume) your servos are position controlled (and not torque controlled) delays in ...
- 6,652
1
vote
What do the model numbers in Harmonic Drive gear drives represent?
It is the pitch diameter of the flex spline in inches/10. You can see it used it their equations for thrust force on the wave generator.
- 4,385
1
vote
Robot clutch to disengage wheels
If your robot's drive wheels always move in the forward direction, you may be able to design in a wrap slip clutch device. This device would tighten a beefy spring around the driven shaft when the ...
- 4,386
1
vote
Robot clutch to disengage wheels
How about a electronix solution, at the moment i guess your motors are controlled by a H-Bridge or similar, by rotating the motor you are generating a current which generates a magnetic field in your ...
- 37
1
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One motor, two wheels (motor direction rotates one wheel forward, reverse for other wheel)?
A freewheel clutch attached to each wheel will do what you want.
When turned in one direction the clutch will transmit power to the wheel but in the opposite direction it will free spin.
This way ...
- 111
1
vote
One motor, two wheels (motor direction rotates one wheel forward, reverse for other wheel)?
Are you talking about a bevel gear? Here's a video - the gold gear would be connected to the motor and the blue gears would be connected to your wheels.
Both wheels are always powered - one is ...
- 16k
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