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2.5" CIM Motor stops when climbing
Is the CIM motor enough to lift robot? After rope winds our motor stops and robot can not go up.
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Re: 2.5" CIM Motor stops when climbing
What gear reduction (if any) do you have connected to the CIM? What drum/winch diameter?
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Re: 2.5" CIM Motor stops when climbing
Any.
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Re: 2.5" CIM Motor stops when climbing
Can you post a picture of your robot? It would help us figure out a solution.
A CIM motor is plenty powerful enough to make the robot climb. |
Re: 2.5" CIM Motor stops when climbing
How to send photo easily? Only link?
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Re: 2.5" CIM Motor stops when climbing
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But you need to provide more detail if you want more definitive help. Describe the complete drivetrain from the CIM to the winch, including gear reductions, winch diameter, and rope diameter. And post a couple of well-focused pictures. You can attach them to your CD post, or you can upload them to imgur.com and provide links. |
Re: 2.5" CIM Motor stops when climbing
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Re: 2.5" CIM Motor stops when climbing
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Re: 2.5" CIM Motor stops when climbing
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What is the diameter of the winch? What is the diameter of your rope? |
Re: 2.5" CIM Motor stops when climbing
That works, thanks!
It looks like you need a larger gear reduction than what you have right now. If you can put a gearbox between the CIM and the climbing shaft, then the climbing shaft will have more torque. This would probably work: http://www.andymark.com/ToughBox-p/am-toughbox.htm I am not sure how long shipping takes to your part of the world. Do you have any other gearboxes, or know teams in your area that might have old gearboxes? |
Re: 2.5" CIM Motor stops when climbing
You will need a gear reduction of some sort. Our robot for 2016 used about a 35:1 gear reduction or so for our winch. We also used only one CIM and it worked perfectly fine for us. We usually were able to climb in about 4 to 5 seconds after the hook was put on the bar.
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Re: 2.5" CIM Motor stops when climbing
A 12.75 GR AM Toughbox with a 150# robot, 2"dia winch, and a CIM motor will operate at over 60A of current. It is likely that a 40A breaker will trip during a 5 second climb. Try a GR ratio of ~25:1
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Re: 2.5" CIM Motor stops when climbing
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That's why I've asked the OP to tell us their winch diameter and rope diameter. |
Re: 2.5" CIM Motor stops when climbing
Winch diameter is 3cm and rope diameter is 1,5cm.
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Re: 2.5" CIM Motor stops when climbing
Can we find another solution but using gearbox? On the motor side small gear, on the shaft side big gear possible?
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Re: 2.5" CIM Motor stops when climbing
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The biggest ratio you can get practically with sprockets (at least easily available ones) is about a 5:1. Now that said, at a 5:1 ratio, if you double the number of motors running it (like adding a second CIM to the opposite side of the system) that 5:1 ratio would work just fine. Ideally though you would want a proper gearbox that will get you closer to that 9:1 ratio. |
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Re: 2.5" CIM Motor stops when climbing
Actually no. Not yet.
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Re: 2.5" CIM Motor stops when climbing
I have enough power to climb a hill on my bicycle... but I cannot do it quickly. I have to do it very slowly. I must shift to a lower gear ratio in order to do it without getting too tired.
Similarly, the CIM motor has enough power to lift your robot, but it cannot do it quickly. It must be (as we say in the US) "geared down". That means, you will have to use a small gear on the motor shaft to drive a shaft with a larger gear. That same shaft may need a small gear driving another shaft with another large gear. Eventually, the power will be "geared down" enough to lift your robot. A gearbox is another way to do it. Another thing that could help is to wind your rope onto a smaller diameter. That too will have the effect of "gearing down" the CIM. Good luck, and I hope we have been helpful to you! |
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Re: 2.5" CIM Motor stops when climbing
If obtaining or making gear is box out of question, consider 2 stages of chain reduction - 5:1 each?
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Re: 2.5" CIM Motor stops when climbing
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You are going to have a hard time doing more than a 3:1 per stage with shaft driven sprockets, since the large tooth counts tend to be plate sprockets. Not sure what size sprockets are easily available there. |
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If you don't mind the slower speed a 15:1 will give a more comfortable margin. |
Re: 2.5" CIM Motor stops when climbing
To sort of cut through what has been posted -- a single CIM has PLENTY of power to execute a robot climb in a very few seconds. The key factors are -- did you gear down enough so that you can wind up on your drum diameter? How much will your effective drum diameter increase as your rope wraps on top of itself? As a reference point, 3946 is planning to wind some 3/8" line on a 1/2" shaft with a 12.75:1 reduction. Our biggest problem appears to be keeping the rope centered on the robot. Larger diameters will require more aggressive gearing, but will be less susceptible to a wrap or two of line.
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In that case would depend on how that specific cord wraps up. The example I gave was based on my own testing and estimates, individual results may vary. :rolleyes: Quote:
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Effective winch radius = (winch diameter + rope diameter) / 2 = 2.25 cm. Winch torque needed to lift robot = 2.25 x 690 = 1550 N-cm = 15.5 N-m. At maximum power, CIM motor torque = 1.2 N-m. [Note: climbing is fastest at maximum power.] Climbing time = lift height x robot weight / winch power = 1 meter x 690 N / 330 W = 2.1 sec. Gear ratio required = 15.5 / 1.2 = 13:1. Andymark Toughbox with 12.75:1 ratio is in stock as I type this. All of the above calculations are simplified by neglecting fricition losses. A real robot will require more climbing time. |
Re: 2.5" CIM Motor stops when climbing
You've described very well. Thank you all. I'll inform you about the advancements.
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Re: 2.5" CIM Motor stops when climbing
If we can find a gearbox, which model do we need for CIM motor? 15:1 Ratio
Thank you. |
Re: 2.5" CIM Motor stops when climbing
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Alternatively you could buy this 16:1 BaneBots Gearbox from AndyMark that comes with all the parts you need (though costs more). You could also use a ToughBox Micro with a 12.75:1 ratio and add a sprocket reduction using a 12 tooth and a 15 tooth sprocket. I believe both Vex and AndyMark ship internationally. |
Re: 2.5" CIM Motor stops when climbing
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Re: 2.5" CIM Motor stops when climbing
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If you want to continue to use your current setup, it shouldn't be too difficult to integrate a Versa Planetary into it as it has the same mounting holes as the CIM ( you'd would probably need to use a different sprocket). You might not have enough time to get it done before Bag day, but I'm sure there would be plenty of teams who would be happy to help you get it working at the NYC regional. |
Re: 2.5" CIM Motor stops when climbing
Just realized you guys will be at the nyc regional. I'll be there all 3 days without too much to do so if you need me to I an bring some versaplanetary parts and I can help you guys get running.
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Do you have someone local (a physics teacher, perhaps) who can help you with the math? |
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I was responding to someone from Turkey who appeared to have neither an engineering background nor English as a first language. Assuming that, I tried to frame my response in simple terms. "Gearing up" is a phrase that typically refers to changing to a higher gear, either in a car or a bicycle, resulting in more speed and less hill-climbing ability. And, vice-versa. I did not think that a treatise on work per unit of time, torque or RPM was necessary - or helpful - in this instance. Similarly, given that the team is in Turkey, it might not be helpful for any of us to advise ordering this or that gearbox from AndyMark. (he asked, "Can we find another solution but using gearbox? On the motor side small gear, on the shaft side big gear possible?") Just sayin'. |
Re: 2.5" CIM Motor stops when climbing
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But I guess we'll just have to agree to disagree whether it is clearer or more confusing... especially for other students reading this thread who are just beginning to understand the concepts of torque and power and gearing. No treatise is necessary. Maybe just a footnote. |
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