Boosting Claw Power: Tips for Increasing Strength and Efficiency

[PrudensOptimus]

Hello,

I have a 40 teeth gearing driving a 24 teeth gearing, and on the 24 teeth gearing attached another 24 teeth gearing to drive a 40 teeth gearing...

The axle with two 24theeths are the left side of the CLAW, and the other is the Right.

I noticed a problem is that it does not have the power i need to "CLOSE" Claws when there are some objects there to be picked it. The object seem to keep the claws from being closed... yet they are very easy items.

How do i increase the "CLOSE" power of the claws? Thanks

 

[minger]

I've attached a little drawing. Someone should probably confirm this, but I'm pretty sure it's correct. You basically are trying to increase the gear ratio. Increasing the gear ratio lowers output RPM, but increases output RPM.

 

[PrudensOptimus]

Bravo drawing, minger.

So you are suggesting that I change the driving wheel to a 24T and drive a 40T?

 

[DaveC426913]

I've attached a little drawing.

Hey! How'd you do that?

 

[minger]

If that first gear is driven by just an axle, then yes. Look at the drawing and imagine how the two different setups will work. Can you see that in my recommended drawing, that moving the first gear a full revolution will only result in a slight movement in the final gear (actually a little more than 1/4 turn). As the first gear moves 24 teeth (1 revolution) 24 teeth is just a little more than 1/2 way for the second gear. That half turn is then transmitted directly to the 3rd gear (24T) which will turn 1/2 way, which at this point is now only 12 teeth. So the final gear turns 12 teeth, which is just a little more than 1/4 revolution. The RPM loss is "transferred" to torque.

Thanks for the props on the pic too, haha. If you need further explanation or anything, just let me know, as I'm just waiting here to get off work so I can go drink some green beer!

 

[PrudensOptimus]

is that drawing the best ratio i can get for power??

 

[minger]

Hey! How'd you do that?

Instead of doing the quick reply thing, if you actually click Reply, or Quote, it takes you to a screen where you can enter smileys, and there is a button below that says "Manage Attachments," and it works just like uploading attachments in an email.

 

[minger]

is that drawing the best ratio i can get for power??

Given [2] 24 teeth gears, and [2] 40 teeth gears, yes. You can of course further increase output torque by getting smaller and larger gears respectively, and increasing the ratio of teeth.

 

[PrudensOptimus]

btw, do you happen to know how to calculate torque required to pull something say at a 89 degree angle?

 

[minger]

Draw a free body diagram. Torque doesn't neccessarily 'pull' things though. Torque can be used to create a force which can pull something, but the definition of torque is that it is a moment generated around a shaft.

For example, say you have a shaft with 20 ftlb of torque applied to it (through your gearing of course), and say your gear is 6in in radius. Then you can generate a force of 10 lbf at the tip of the gear. Sooo...you could wrap a cord aroung the gear, have it go around a pulley and lift a <10lbf item.

I can draw you a picture if you want...

after lunch of course ;)

 

[PrudensOptimus]

noo, do you have AIM...

 

[minger]

Well I'm at work right now...can't really have AIM and look like I'm working, haha. I can try to answer your questions on here (at least I can alt+tab outta this window quickly)

 

[PrudensOptimus]

Pulley

Hi,

I have made a pulley using needle threads on those "roll-up" thingies you see on powerplant trucks.

Anyways, I have mounted 2 of those "roll ups" on an axle which is connected to a motor. It is suppose to pull up something... which it does... but not as good as I want... What can I do to increase power and speed? (power is priority).

The pulley is about 3 inches about the thing being pulled... Will reduce the height of the pulley increase pullying power?

 

[DaveC426913]

For a given motor, lifting power and speed will be a trade-off. The only way to increase both is to get a bigger motor.

If you want more power at the cost of speed, you could reduce you gear ratio (eg. one turn at the motor produces 1/10th turn at the lift), or you could make a block & tackle system - as in the attached schematic.



(Cool!)

 

[PrudensOptimus]

Nice diagram, however my situation is a little different.

I'm not exactly lifting something up at 90 degrees.

I'm "pullying" an axle, which pulls the "white thingies" on both sides... thereby "dragging" the thing up an angle, so as to "lift" the claw a little up.

Pictures: (note taken prior to my assembly of the pullies)
http://www.hinst.net/~tom/robot/1.jpg
http://www.hinst.net/~tom/robot/2.jpg
http://www.hinst.net/~tom/robot/3.jpg

 

[DaveC426913]

Well, regardless of the actual arrangment, the principle is the same. For a given motor, you trade off speed for power. Changing gear ratios is the most obvious way.


Another way though, is to move the fulcrum of your lever.

Needlenose pliers have a long business end and a short handle supplying the power - i.e. the fulcrum is very far from the business end. Little movement in the handle produces a large, but weak, movement in the pincers.

But bolt cutters have a very short business end operated by a very long handle supplying the power. i.e the fulcrum is very near the business end. You must move the handles of bolt cutters a lot to produce just a little motion in the pincers, but what little movement you get is very powerful.

Your arrangment is more akin to the needlenose pliers. Try finding something in between.

 

[PrudensOptimus]

will connecting more needlethreads help with the pulleying?