your thoughts on the FP CIM/2.5 CIM motor drive setup versus 2 2.5 CIM motors

[waialua359]

......using the AM2 shifters.
How much torque difference? We haven't seen any links or posts of other teams that have done this.

[jgannon]

We made the switch from FP + 2.5 to dual 2.5 in our shifters between events last season. The weight savings was substantial in our quest to move down a weight class, but you give up a lot in torque, too. I don't have much in the way of quantitative data to offer you, but my drivers complained immediately that we no longer had any advantage in pushing matches, and we obviously struggled to turn in high gear. Both of these problems could have been mitigated with a better selection of sprocket reduction, but if you do your math based on the FP specs and then swap the motors later, you're in for a world of hurt.

[AdamHeard]

Originally Posted by jgannon

We made the switch from FP + 2.5 to dual 2.5 in our shifters between events last season. The weight savings was substantial in our quest to move down a weight class, but you give up a lot in torque, too. I don't have much in the way of quantitative data to offer you, but my drivers complained immediately that we no longer had any advantage in pushing matches, and we obviously struggled to turn in high gear. Both of these problems could have been mitigated with a better selection of sprocket reduction, but if you do your math based on the FP specs and then swap the motors later, you're in for a world of hurt.

really? When the speeds are matched, the FP doesn't even come close to the torque the small CIM puts out.

[Billfred]

For 2007, 1618 used one of each on our AndyMarks by design. Doing so allowed us to use a small CIM on our arm, which gave us some off-the-shelf options for interfacing with #35 chain. (Well, rather, it gave us options better than those we could've kludged together ourselves.) The sprocket selection was done using JVN's calculator, which I'd recommend for anybody. (We used 30-tooth sprockets on the wheels driven by the gearbox; wheel diameter was about 5.5". Those choices worked great for us, but might well have been dangerous in other hands given the designer's inexperience at the time; check them yourself to be sure.)

If you have the weight (we did) or really want to use your smaller, lighter CIMs elsewhere (we did), they're worth considering.

[IndySam]

We used one CIM each in AM shifters and nobody out-pushed us. Not even multi-motor monsters.

It not all about what the motors can put out it's about how much of that energy you can transfer to the floor.

Lots of power is nothing unless you can use it effectively.

[Cory]

We used 1 CIM 1 FP in 2006. We swore to NEVER use FP motors in a drivetrain ever again. By the end of the season we had fried at least 8-10 of them. We replaced four in a row in the eliminations during Atlanta.

My understanding is that in 2005 when we did the same thing, it worked fine. it's possible that was because there was no pushing. It's also possible that the AM planetaries we used were a lot better, since we replaced the standard needle bearing with a ball bearing.

In 2006 we had numerous issues with the AM planetaries seizing the sun gears to their pins, the ring gear having enough slop in it's pocket to cause seizing, and the output shaft sliding in and out, causing the rear end of the planetary assembly to push against the motor plate. We also had issues with keeping the motor concentric to the rest of the assembly. It's possible these issues were what led to us killing so many FP's, but we aren't willing to take the risk to find out.

We used the AM planetaries with FP's in 2007 to power our elevator, and they were fantastic. Totally trouble free from the start. Andy resolved every issue we had with them, and then some. The 2007 version is totally reliable, and we would use it (and any other AndyMark product) without reservation at any point in the future.

[AdamHeard]

Wait.....

Are we talking about the FP motor w/ an AndyMark planetary a la 254, or are we talking the Big CIM (FP) and a small CIM.

Either way; two small CIMs is more powerful then any of the above combination. The Big CIM is more powerful than the FP, but the small CIM beats both.

[Cory]

Originally Posted by AdamHeard

Wait.....

Are we talking about the FP motor w/ an AndyMark planetary a la 254, or are we talking the Big CIM (FP) and a small CIM.

Either way; two small CIMs is more powerful then any of the above combination. The Big CIM is more powerful than the FP, but the small CIM beats both.

Oops I can't read. I saw FP in the title subject and assumed it meant fisher price motors... now I see it said FP CIM.

My bad. You can disregard my comments then. I suppose anyone considering FP/CIM transmissions can benefit from our misfortune, so I'll leave them there

[waialua359]

thanks for the comments.
I am assuming then that a FP CIM / CIM combination will not outdo a CIM / CIM combination.
We understand the whole transfer of power to the floor issue and traction effectiveness. However, with all else equal, just wanted to know.
Due to timing issues, we are debating whether to plan to modify the AM supershifter plates to accept the big FP CIM motor, since there are no provisions for it at the moment.
If it makes a difference in a pushing match, we will go that route.
Our robot had tractions issues also last year and we were looking to improve on that and several related areas. Our function designs were fine last year when trying to score ringers.

[=Martin=Taylor=]

Here's a pretty definitive answer:

We built two identical drive trains last year. One for the competition robot and one for practice/prototyping. The practice/prototyping robot used one FP CIM (The Big CIM) and one small CIM on each side. The competition robot used two small CIMs on each side.

Our driver didn't seem to notice any difference. Handling wasn't affected. They both worked identically.

However, we saved a significant amount of weight by switching to the small CIMs.

[IndySam]

Please keep in mind that we may not get either CIM motor in the kit of parts this year. But it is a good exercise, modifying the plates in case we do get a curve ball.

But I guarantee if there is a switch Andy and Mark will be burning the midnight CAD on the 5th coming up with adapter plates

[waialua359]

Originally Posted by Hachiban VIII

Here's a pretty definitive answer:

We built two identical drive trains last year. One for the competition robot and one for practice/prototyping. The practice/prototyping robot used one FP CIM (The Big CIM) and one small CIM on each side. The competition robot used two small CIMs on each side.

Our driver didn't seem to notice any difference. Handling wasn't affected. They both worked identically.

However, we saved a significant amount of weight by switching to the small CIMs.

thanks for the response. if we have time, we may prototype adaptor plates since we look to go direct drive with the supershifters. weight tradeoff is definitely a huge factor.
we made adaptor plates to our am2 shifter plates since we wanted to try a direct drive, however, using one Big CIM motor made it considerably heavier.
Of course, the speed would be too fast without an addtional reduction using the AM2's.
We were toying with the idea of using the FP motors with planetaries also, but after hearing Cory's comments, we may use that as a last resort, if necessary.

thanks.