CIM Motor Sacrifice

[JamesCH95]

What is possible with a 2-FP shooter from 2006. Six (6) balls air-born at the same time. Needless to say we are building another 5-roller shooter. No need to sacrifice CIMs for it IMO.

[Aren Siekmeier]

Originally Posted by JamesCH95

What is possible with a 2-FP shooter from 2006. Six (6) balls air-born at the same time. Needless to say we are building another 5-roller shooter. No need to sacrifice CIMs for it IMO.

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).

[JamesCH95]

Originally Posted by compwiztobe

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).

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

[onecoolc]

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.

[Aren Siekmeier]

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.

[billbo911]

Originally Posted by onecoolc

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.

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.

[mikegrundvig]

In our testing, the 550 appears more than enough to handle our 12" shooting wheels.

Originally Posted by billbo911

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.

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

[Ether]

Originally Posted by billbo911

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.

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

[billbo911]

Originally Posted by Ether

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

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.

[Ether]

Originally Posted by billbo911

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.

OK thanks, I'm with you now.

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