Hot answers tagged

7

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 higher ratios. More specifically, they take up very little axial space and use only one stage of reduction. They are beneficial for high precision tasks and ...


7

Your calculation of about 80 N⋅m torque for lifting 8 kg with a 1 m lever arm is ok; more precisely, the number is 8 kg ⋅ 9.81 m/s² ⋅ 1 m = 78.48 N⋅m. As mentioned in other answers, you will need to scale up to account for gear inefficiency. A simple calculation based on work shows that the Banebots RS-550 DC motor mentioned in the question is not powerful ...


6

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. When it comes to getting the maximum performance out of motors, thermal issues are the main factor. One starts asking questions like: What's the actual duty ...


5

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 be based on the load, gearbox, wheel/pulley diameter, friction and other losses, etc.) then you can ballpark feasibility by evaluating your required torque ...


3

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 efficiency. It's a subtle but significant difference between what you said (torque transmission efficiency). First, efficiency is defined as the ratio of output ...


3

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 at right in the illustration.) Note, this linkage and some other leg mechanism linkages use a rotary crank; ie, rather than using a 180° back-and-forth motor, ...


3

"Precision motors" and "planetary gear motors" aren't really describing the same attribute of the motor. It's like comparing "fine-point pencils" to "red pencils" -- they could be both fine-point and red, either fine-point or red, or neither. Planetary gears are generally used to convert high RPM at low torque to low RPM at high torque. Because each ...


3

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 thickness to get the shear area. I'm assuming 3 teeth in contact and mesh efficiency around 30%. The tooth stresses are a little more than one order of ...


3

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 allowable force for a nylon worm gear (Equation 18-4). A torque of 5 kg-cm caused by a force at (45/2) = 22.5mm (2.25cm) means the force is 2.2 kgf. While I ...


3

This is called a Stewart platform. You can use any linear actuator type, hydraulic, pneumatic or electric.


2

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 tapping acrylic as long as I kept the tool slow so as not to overheat and warp. We have also used self-tapping screws for Delrin and UHMW with good results (and ...


2

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 like this type of thing. Although it does depend on continuous rotation, so maybe not appropriate for your application. With a servo-motor that rotates back-...


2

I doubt you will find a solution in the price range you are looking for. But I will answer your questions as best I can. 1) You need match the gear to the bore, ideally within a thousandths of an inch. A .12in in shaft simply will not work with even a .125. Especially, at any reasonable speed. If you have matching shaft and bore, a setscrew could be used or ...


2

This is not directly answering all your questions, but if you are starting out with mechanical stuff I highly recommend reading pretty much all this guy's web site. http://www.etotheipiplusone.net/ In particular, take a look at his battle robot stuff. There is some gold in there! If you want a more condensed version, he wrote another great article on ...


2

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 the shaft into the bearings, but keep the shaft stopper set screws loose. Then add whatever preload you want and locktite it in place (notice the "red" ...


2

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, with an obstacle of a given height in front of it. Work out the angle the wheel has to "lever" itself up to get over the obstacle, and work out the motor ...


2

It's quite possible for an $8 motor with enough gearing to move a mass as you describe. It's also possible to have gear ratios much more than a hundred. However: Check that the gears you're using are rated for the torque you need. What speed of rotation do you need? This defines the motor power you need (something people often forgot to think about). Power ...


2

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 debates in cycling over the years, about various inventors attempting to "improve" the design of the bike with belts/pulleys, conventional gears, even things ...


2

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/torque isn't higher than the friction, this will work fine. A drop of super glue can also help this along! This works with both plastic and metal gears. Another ...


2

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 hobbyist projects. b) Since you are willing to do build a hobbyist-grade robotic arm, I think it would be better if you define the desired specs of your arm ...


2

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 of transmitting a greater force less likely to strip less precise greater tolerance more sliding friction1 greater backlash Less smooth movement Small teeth: ...


1

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.


1

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 motor (see Maxwells Laws for more information). If your motor is not connected the only fricition you have is the friction of your gears. So you can use a ...


1

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 when the motor is turned in one direction one wheel will turn and in the other direction the other wheel will turn in the same direction as the first. The catch ...


1

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 powered in forward and the other is powered in reverse. You're not clear on the purpose of this device, so I don't know if this fits your needs. A differential ...


1

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 typically not because of any such intrinsic need, but because the control systems (software) were designed decades ago and at its core uses mathematics that assumes ...


1

Thanks for the suggestions guys. I'll consider your suggestions and give an update once I have chosen a motor.


1

One problem I can see is, that you are using stall torque (at 0 rpm) and no load rotation speed (at 0 Nm). If you want the motor to still turn, it will have lower torque than this, and lower RPM. Also, running the motor at (or close to) stall for long time will probably overheat it (it's gonna draw 85A (that is about 1KW) and dissipate it all as heat). I ...


1

As SteveO suggested, it is clear from the exploded diagram that a bearing is part of each Tail Gear Case Plate, and the Tail Output Shaft Stopper is locked to the output shaft using the set screws, which sit in the D grooves in the shaft. The Washer and Poly Slider precisely set the distance between the left bearing and the mesh gear (actually a mitre gear),...


1

You can see exactly this part in your image. It won't rub anywhere. Since your second pictures shows a so called exploded drawing you cant tell a lot about exact metrics.


Only top voted, non community-wiki answers of a minimum length are eligible