New VEXpro products

If you didn’t catch FUN Recap last night Paul Copioli from VEX was on and discussed some of the new products coming to VEXpro. Here’s the segment where he discusses them. https://youtu.be/miPyKHc_hgM?t=3044

Plastic is fantastic.

Super stoked for these new products.

Paul made a very intriguing comment about being completely on board with MiniCIMs now a days as opposed to full sized CIMs. It would be cool to see some of the testing they did on the dyno for each style of drivetrain alongside the 2018 product reveal.

Versablocks on 1x1 tube ftw! That’s going to open up a bunch of design options for lightweight mechanisms.

You can look at the data on motors.vex.com and figure it out. It isn’t rocket science… it might be electrical engineering or mechanical engineering or physics though… on second thought, better call Musk and get him on this.

I’m a certified rocket scientist. Can confirm this is not rocket science.

It isn’t about the individual motor performance numbers.

Even at 40 amps the CIM motor has more power than the miniCIM (but by only 30 Watts).

It’s about total system performance and total system current draw. The CIM motors at or near stall just draw a ridiculous amount of current from the battery making the actual voltage at the motors much lower.

I will try to get a system test on our last year’s robot.

Good thing I only had to convince my team to switch. I don’t need to convince you all as you can test it and see for yourself.

Looking at the numbers it seems to have to do with motor performance over time… or at least that’s how I’ve heard others describe it and what I’ve bought into by looking at it myself. I’m far from a rocket scientist though. Something about bearings vs bushings and how heat impacts the motor performance over time.

Not to derail the thread… But question for Paul. Did you ever get your team to do the testing as talked about in this thread? Sorry if you posted it… i may have missed it.

During the podcast, Paul mentioned that they couldn’t finish their testing due to a power supply failure on their dyno. In any case, I’m curious if they’re planning to continue testing when that is repaired, and if they’d be willing to share the data they have collected so far.

Thanks… I didn’t catch that part if the broadcast

Sent from my XT1254 using Tapatalk

How does this play with current-limiting on the drive, for teams that use it?

Is that 1x1 versablock aluminum or plastic?
MiniCIM drivetrains… I suppose I’ll have to try that now. At least they are shorter than CIMs, so any flipped-cim gearbox becomes that much easier to fit.

Looked like Nylon in the video (assuming 30% glass fill)

Yeah, the Versablock Mini is plastic. 30% Glass Filled Nylon.

Regarding the miniCIMS, the max power over time curve does tell most of the story, but the smaller stall current also plays a big role in the battery voltage available during a match.

And yes, bearings vs bushings is a big factor in all of these things.

That’s what I’m also trying to figure out, whether the current-limiting is mechanical/design (e.g. traction limits) or programmed. As far as I can see, the mini-CIM has four minor advantages over its larger, more pedestrian brother (using Vex experimental numbers):

  1. It is slightly cheaper (11%) [STRIKE]and has Don’t Panic written on it in large friendly letters[/STRIKE]
  2. It is smaller (The CIM main body is 40% longer and 30% heavier)
  3. It has a slightly higher (10%) free speed
  4. It will “only” try to draw 89A vs 131A at a 12V stall, reducing the likelihood of brown out and/or tripping the main breaker

Under normal design conditions, a CIM will draw up to 30 or 40A for an extended duration, 60A for a relatively short duration. Let’s compare the performance of the CIM and mini-CIM at 12V and each 10A from 0A to 89A. I’m also going to toss in a BAG geared down 2:1 up to its stall current. Again, these are Vex experimental numbers from the performance curves, selecting the row with the current nearest to the target:


           CIM            Mini-CIM        BAG @ 2:1
      Speed   Torque   Speed   Torque   Speed   Torque
AMPS   rpm     N-m      rpm     N-m      rpm     N-m
  10   5010   0.145     5373   0.123     5403   0.156 
  20   4637   0.314     4672   0.282     4151   0.318
  30   4211   0.507     4029   0.437     2899   0.482
  40   3784   0.700     3329   0.606     1581   0.656
  50   3358   0.893     2686   0.761      330   0.818
  60   2932   1.086     1985   0.930
  70   2558   1.255     1285   1.099
  80   2132   1.448      642   1.254
  89   1759   1.617        0   1.409

The CIM clearly outperforms the MiniCIM above 20A, and the performance is comparable, but slight advantage CIM (power and efficiency) all the way down to free current. [STRIKE]Likewise, if the draw was to be 30A or less all the time, the BAG has an advantage (apart from the necessity to gear it down farther). The only use case that I can see the mini-CIM as best is when MOST of the usage will be below 20A, but there will be peak requirements that will overtax the BAG but not overheat a miniCIM. (And that’s leaving out the 775 pro, which may well be actually the champ for THAT use case.) [/strike]

The only advantage I found to survive comparison with the CIM is reducing the likelihood of overdrawing the battery or tripping the main breaker. Monitoring current draw and/or battery voltage seems a more elegant solution than using a smaller motor.

Paul, I’m sure you know what you’re recommending – what am I missing here?

That’s what we were running at MTTD - four MiniCims in flipped gearboxes. Of course, this was nowhere near a typical robot (18"x18", 53 lbs with battery) - but we were quite satisfied with the MiniCIM drive. Space saving and snappy.

This robot was definitely the favorite of many in attendance.

Gus,

The max power curve over time is the biggest indictment for the CIM. I first discovered this when we just weren’t getting the power from the drive base I thought we should in 2011 so I started looking closer.

The CIM motor uses a bushing at the front of the motor and the mini uses a bearing. When the bushing gets hot the CIM shaft has significantly more friction.

This causes losses just not described in the motor performance but the Max power over time Test really shows this.

The CIM was designed for a power jack for RVs. The mini was designed specifically for our robots. Between the 775pro and miniCIMs I probably won’t use the CIM motor ever again.