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serdaruluer 04-02-2017 11:23

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.

Christopher149 04-02-2017 11:28

Re: 2.5" CIM Motor stops when climbing
 
What gear reduction (if any) do you have connected to the CIM? What drum/winch diameter?

serdaruluer 04-02-2017 11:33

Re: 2.5" CIM Motor stops when climbing
 
Any.

s_forbes 04-02-2017 11:34

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.

serdaruluer 04-02-2017 11:42

Re: 2.5" CIM Motor stops when climbing
 
How to send photo easily? Only link?

Ether 04-02-2017 11:44

Re: 2.5" CIM Motor stops when climbing
 
Quote:

Originally Posted by serdaruluer (Post 1640277)
Any.

The problem may be inadequate gear reduction.

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.




serdaruluer 04-02-2017 11:50

Re: 2.5" CIM Motor stops when climbing
 
https://drive.google.com/file/d/0B0L...ew?usp=sharing

serdaruluer 04-02-2017 11:53

Re: 2.5" CIM Motor stops when climbing
 
https://drive.google.com/file/d/0B0L...ew?usp=sharing

Ether 04-02-2017 12:04

Re: 2.5" CIM Motor stops when climbing
 
Quote:

Originally Posted by serdaruluer (Post 1640293)

It looks like you have no gear reduction.

What is the diameter of the winch?

What is the diameter of your rope?



s_forbes 04-02-2017 12:06

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?

logank013 04-02-2017 13:10

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.

Jacob Plicque 04-02-2017 13:16

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

Ether 04-02-2017 13:19

Re: 2.5" CIM Motor stops when climbing
 
Quote:

Originally Posted by logank013 (Post 1640327)
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.

The appropriate gear reduction depends on the winch diameter and -- in some designs -- on the rope diameter.

That's why I've asked the OP to tell us their winch diameter and rope diameter.



serdaruluer 04-02-2017 15:31

Re: 2.5" CIM Motor stops when climbing
 
Winch diameter is 3cm and rope diameter is 1,5cm.

serdaruluer 04-02-2017 15:36

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?

Sperkowsky 04-02-2017 15:50

Re: 2.5" CIM Motor stops when climbing
 
Quote:

Originally Posted by serdaruluer (Post 1640389)
Can we find another solution but using gearbox? On the motor side small gear, on the shaft side big gear possible?

Unfortunately I don't think so. You need a bigger reduction for this than you can get from just a chain reduction. Look into a versaplanetary or a banebots planetary. Shipping may be an issue so id try to contact some local teams to see if they have anything laying around.

cbale2000 04-02-2017 16:28

Re: 2.5" CIM Motor stops when climbing
 
Quote:

Originally Posted by serdaruluer (Post 1640389)
Can we find another solution but using gearbox? On the motor side small gear, on the shaft side big gear possible?

Based on the math I've done you need about a 9:1 ratio between the CIM motor and the spool (assuming a 1" diameter spool and a ratchet strap-style rope) to lift a fully loaded FRC robot with a decent margin of error (stalls at ~277lbs).

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.

Ether 04-02-2017 16:55

Re: 2.5" CIM Motor stops when climbing
 
Quote:

Originally Posted by cbale2000 (Post 1640418)
Based on the math I've done you need about a 9:1 ratio between the CIM motor and the spool (assuming a 1" diameter spool.

Have you taken into account the effective winch diameter changing as the rope wraps around it?



serdaruluer 04-02-2017 17:04

Re: 2.5" CIM Motor stops when climbing
 
Actually no. Not yet.

chapman1 04-02-2017 17:22

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!

Ether 04-02-2017 17:50

Re: 2.5" CIM Motor stops when climbing
 
Quote:

Originally Posted by chapman1 (Post 1640445)
Eventually, the power torque will be "geared down up" enough to lift your robot. A gearbox is another way to do it.

FTFY. The power out of a gearbox is the same as the power into the gearbox, minus any inefficiency in the gearbox. The power is neither geared up nor geared down.



page2067 04-02-2017 18:41

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?

Donut 04-02-2017 19:13

Re: 2.5" CIM Motor stops when climbing
 
Quote:

Originally Posted by page2067 (Post 1640476)
If obtaining or making gear is box out of question, consider 2 stages of chain reduction - 5:1 each?

This is what I would suggest. When I was a rookie in 2004, and COTS gearboxes weren't easily available, we had to make a drivetrain using two stages of chain reductions.

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.

cbale2000 04-02-2017 19:15

Re: 2.5" CIM Motor stops when climbing
 
Quote:

Originally Posted by Ether (Post 1640433)
Have you taken into account the effective winch diameter changing as the rope wraps around it?

Yes, though it's partially based on the assumption that the strap we're using doesn't wrap exactly straight (which in our testing it typically does not). Even so, you need about an inch of extra strap wrapped up before it starts to cause problems.

If you don't mind the slower speed a 15:1 will give a more comfortable margin.

GeeTwo 04-02-2017 19:43

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.

Ether 04-02-2017 20:00

Re: 2.5" CIM Motor stops when climbing
 
Quote:

Originally Posted by cbale2000 (Post 1640488)
Yes, though it's partially based on the assumption that the strap we're using

He's not using a strap. He's using a 1.5 cm diameter cord:

Quote:

Originally Posted by serdaruluer (Post 1640387)
Winch diameter is 3cm and rope diameter is 1,5cm.



cbale2000 04-02-2017 23:14

Re: 2.5" CIM Motor stops when climbing
 
Quote:

Originally Posted by Ether (Post 1640505)
He's not using a strap. He's using a 1.5 cm diameter cord:

Didn't see that response.
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:

Originally Posted by cbale2000 (Post 1640418)
Based on the math I've done you need about a 9:1 ratio between the CIM motor and the spool (assuming a 1" diameter spool and a ratchet strap-style rope) to lift a fully loaded FRC robot with a decent margin of error (stalls at ~277lbs).

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.


Richard Wallace 04-02-2017 23:47

Re: 2.5" CIM Motor stops when climbing
 
Quote:

Originally Posted by serdaruluer (Post 1640387)
Winch diameter is 3cm and rope diameter is 1,5cm.

Maximum robot mass = 70 kg. Maximum robot weight = 70 x 9.8 = 690 N.

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.

serdaruluer 05-02-2017 06:24

Re: 2.5" CIM Motor stops when climbing
 
You've described very well. Thank you all. I'll inform you about the advancements.

serdaruluer 06-02-2017 09:27

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.

cbale2000 06-02-2017 09:54

Re: 2.5" CIM Motor stops when climbing
 
Quote:

Originally Posted by serdaruluer (Post 1640996)
If we can find a gearbox, which model do we need for CIM motor? 15:1 Ratio

Thank you.

For a direct 15:1 ratio you could get a VexPro VersaPlanetary with a 3:1 and a 5:1 reduction (which combine to create a 15:1), you would also need a CIM Adapter and 2 ring gears.

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.

serdaruluer 08-02-2017 05:31

Re: 2.5" CIM Motor stops when climbing
 
Can we use
http://www.andymark.com/PG71-Gearmot...-p/am-2971.htm

pilleya 08-02-2017 05:44

Re: 2.5" CIM Motor stops when climbing
 
Quote:

Originally Posted by serdaruluer (Post 1641925)

Not without a sprocket reduction between the output shaft and the shaft of your climber, even then chances are it won't be able to lift your robot all the way up the rope within the 30 second end game period. It has 1/10th the power of the CIM, so it will be much slower compared with a properly geared CIM.

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.

Sperkowsky 08-02-2017 07:26

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.

pfreivald 08-02-2017 10:53

Re: 2.5" CIM Motor stops when climbing
 
Quote:

Originally Posted by serdaruluer (Post 1641925)

In theory, any motor can lift anything, if geared properly. But the power of the motor will determine how fast it can (theoretically do so).

Do you have someone local (a physics teacher, perhaps) who can help you with the math?

chapman1 08-02-2017 11:22

Re: 2.5" CIM Motor stops when climbing
 
Quote:

Originally Posted by Ether (Post 1640452)
FTFY. The power out of a gearbox is the same as the power into the gearbox, minus any inefficiency in the gearbox. The power is neither geared up nor geared down.




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'.

Ether 08-02-2017 13:09

Re: 2.5" CIM Motor stops when climbing
 
Quote:

Originally Posted by chapman1 (Post 1642009)
I tried to frame my response in simple terms.

I understand you were trying to help, and I applaud that.

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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