Re: CIM Motor Sacrifice
 

And that's with the older, less powerful (if the specs out there right are to be trusted) FP. With 2 of last year's, the 00673, you are much closer to CIM performance. 289W vs only 172W (approx).

Re: CIM Motor Sacrifice
 

That sounds about right. Though the FP specs seem to change every darn year... including one year where they gave us 6V FP motors :ahh:

Re: CIM Motor Sacrifice
 

Have any teams used two RS-550s in a CIM-U-LATOR in place of a CIM? If so, what were your results?

I've seen a lot of posts in this thread with grievances towards the RS-775 (and case shorts), so I'm wondering about experiences with the RS-550s, if anyone can share.

Re: CIM Motor Sacrifice
 

Today we tested an RS 775 into a CIMulator with a 10 to 42 sprocket reduction (#25 chain) to 8 inch wheels. Gear ratio of 11.3, calculated free speed at tip of wheel of 40 ft/s. The wheels didn't appear to spin down very noticably on shooting the ball, but we don't know yet exactly what the exit velocity was or where we are for making some of the shots we need (top goal from key, half court, etc.). We are sticking with the FP/775 substitution plan, and at worst might need 4 of such motors. Hoping for only needing 2. It's too important to keep our CIMs in the drivetrain.

Re: CIM Motor Sacrifice
 

My team is looking into motors for a launching device and you seem to know what you're talking about. Now for the amateur question: what is the BB 775 motor and the CIMulator? Where might I find specs on it or at least somewhere to buy it?

Re: CIM Motor Sacrifice
 

Based on all the contributions you've given to this post thus far, I don't doubt this estimation, but where are you getting these ratios? Is it just based on experience with the FP's or did you do some calculations to figure it out, and if so could you share? 'preciate it!

Can I just point out real quick that your robot BROKE the match that we were supposed to be allied with you!! :ahh: Yes I'm still bitter about that, you had an AMAZING robot that year! Haha can't wait to see what you guys put out this year!

Re: CIM Motor Sacrifice
 

BB775 is a BaneBots M7-RS775-18 Motor. Specs can be found here.

CIMulator is a gearbox that will mount 1 or 2 BB 775s and give you an output shaft and output mounting holes of a CIM motor (Basically it allows you to fit BB775s where you'd use a CIM motor). Specs can be found here.

Re: CIM Motor Sacrifice
 

Those are the specs at 18 volts.

The 12 volt specs are here.

Or you can go here.

Re: CIM Motor Sacrifice
 

I just looked at that link and I think you are slightly mistaken. It appears that there are 2 different cimulators from BB, one for RS-775s and one for RS-550s. Only the one for the 550 says it can accomodate 2 motors, the RS-775 cimulator can only accomdate 1 motor. Is this correct?

Also, when people talk of using the 775s for shooting, should I assume you mean the RS-775-18v?

Pardon my ignorance, but I was wondering what is meant by the numbers before the motors. I know it has something to do with size or power, but I don't know much more than that. Could someone give me a brief explanation?

Thank you.

Re: CIM Motor Sacrifice
 

Your assumption about the gearboxes is correct. I was just looking at our cimulators for 775s today noting how they only take one, likely because the motor is just too big to fit two with that shaft separation.

We would certainly use the 18V motors since they are less likely to fry due to the higher volt rating. I haven't actually looked at the specs for the 12V, but I imagine they can't be much better than the 18V at 12 volts.

The 550 or 775 business (or 00673, 9015, 9012 if you're talking about the FPs) is for the most part just a part number. The first digit implies something about the size, as the 550s are 500 series motors, a common DC motor size (the FPs are as well, and will mount in many of the same places as the 550). The 775 is a bit bigger and more powerful, as the bigger number implies, but there is no overarching protocol of any sort determining these numbers (that I'm aware of....)

Re: CIM Motor Sacrifice
 

After testing our prototype shooter, powered by a single CIM, we decided to make a change. The CIM was more than sufficient for our plans, but we believe they are better suited for our drive train.

Based on the results of our testing, we made the following adjustments:
The single 340Watt CIM, driving 8" wheels, reduced 1.8:1 with chain sprockets will be replaced by 2 250Watt RS550s attached to a 5:1 reduction CIM-Sim from AndyMark. The output will either be direct driving the shooting wheels or go through a 1:1.8 chain sprocket increase. Either way will work out, but the 1:1.8 increase should have the motors running at about 50% power.

We plan on using and encoder and PID loop to maintain the desired RPM. Running the motors at 50% power will allow us plenty of overhead to control RPM during shots and when the battery starts to fade near the end of a match.

Re: CIM Motor Sacrifice
 

In our testing, the 550 appears more than enough to handle our 12" shooting wheels.
This is exactly our plan as well. We went with custom machined shooting wheels so we can move all the mass to the very lip of them to get the most bang for the buck. Two 550s geared down seems more than enough all told.

-Mike

Re: CIM Motor Sacrifice
 

What do you mean by 50% "power" in this context?

Re: CIM Motor Sacrifice
 

Ah, I see I was a little more vague than I intended to be.

Our intent is to run the motors as close to (Max No Load RPM/2), technically at or near the motors maximum power point. So, my statement was termed incorrectly. I should have simply said 50% of max RPM.

Thanks for calling me on this. Clarifying this point does make a HUGE difference.

Re: CIM Motor Sacrifice
 

OK thanks, I'm with you now.

See my earlier post in another thread on this same design question.