Motor rpm and Torque
 

What is the rpm and torque for all of this year's motors. Thank you.

You need to download and read "The Robot.pdf" off of the FRC Documents page. It isn't as good as last year, but the basic information is still there, under "Kit of Parts".

I see it for the new Bosch and for the Fisher Price, but the others don't have any technical data.

Does anyone have the URL's for last year's appendix with the specs on the www2.usfirst.org site? they took the links off the main site. This has the specs for the other motors. I have a copy of the file at work but not at home. Now that i have broadband I'll download it here.

OK, I found a hard copy from 2000 - The motors don't look quite the same but similar enough. Since I haven't seen anybody else posting specs, here's what I've got and it will at least get you started until we see the right ones:

Window Motor (ITT Automotive): 20 Amps Stall Current, 6 Nm @ 41 RPM, 1.8 N.M @ 64 RPM

Van Door Motor (Tiagene): 75 RPM No Load Speed, Stall Torque 37 Nm Clockwise, 34 Nm Counter-Clockwise, Stall Current 40 Amps.

Globe Motor (with Drive Assembly), at 10 Vdc: No Load Speed 87 RPM, Stall Torque 150 In-Lb, Stall current 18.5 Amps, No Load Current .82 Amps.

Globe Motor (Motor Only), at 10 Vdc: No Load Speed 97RPM, Stall Torque 30 Oz-In, Stall current 18.5 Amps, No Load Current .82 Amps.

Gary,

If you still need anything from last year, I just got done archiving it here: http://www.cvhsrobotics.org/resources.htm. You'll find the 2002 documentation toward the bottom of the page.

-Kevin

For motor specs from last year's motors and the van door motor, they may be found at www.team696.org/motorspecs.html There is also a link to download the Joe Johnson motor comparison spreadsheet.

PLEASE NOTE:

the drill motors ARE different this year - do not do calculations using the drill motors on these specs...

Tom

Thanks for the links. Still, the motors look different than last year's, and the manufacturers are listed as different (Nippon-Denso vs Valco for the window and Bosch vs Taigene for the Van door), so as soon as someone gets the official specs please post. These should be adequate for now.

Did anyone else notice a discrepency in the information on the new Bosch with gearbox?

On page 5, the robot manual describes the output of the bosch with gear box as 0-450 or 0-1500, but if you take the 19670 no load RPM with the ratios of 12.07:1 or 42.62:1, you get (approximiately) 461.5 or 1630 RPM.

Efficiencies
 

I believe their numbers, but that means that the efficiencies for these gearboxes are pretty darn good.

After doing some calculations, I get these efficiencies:

Gearbox in High: 92%
Gearbox in Low: 97.5%

The "old" gearboxes had these efficiencies:

Old Gearbox in High: 80%
Old Gearbox in Low: 70%

... so...

With a larger motor, more efficient gearboxes, and a bigger circuit breakers (40A compared to 30A), these drill motors may be close to double the power compared to last year's Bosch motor/gearbox combination. Holy torque, Batman!

Andy B.

This is important... to choose the right motors for the right jobs, and to figure out gearings and such we need to know motor specs. Preferably stall torque, free RPM, torque vs RPM curve.

Specifically the new drill motors vs "chalupa" (if thats how you spell it). Which has more torque, what are they RPM's? Which is better to use for drive train, what are the RPM-torque curves?

ACK :)

Greg

Drill vs. Chiaphua
 

The Chiaphua is the same motor as last year with a different shaft. It was made specifically for FIRST and is the same model number with an "FR" in front of it. See the link below for the Chiaphua spreadsheet, but disregard the pinion information.

The new drill motor has more power than the Chiaphua (see some specs below), but both are very good candidates for a drive motor.

Bosch drill motor specs (@12V):

Stall Torque = 0.87 N-m
Stall Amps = 127
Free Speed = 19670 RPM

THe above is preliminary info, but I should be getting confirmation from Bosch tomorrow.

-Paul

If this is correct, the drill motors are still less powerful then the atwood "chaiupas" (i will never spell that correctly)? By my conversions, the chaiupas stall at about twice the torque as the new drill motors (though both at 100+ amps, ACK!).

Someone check me, stupid english/metric.

Greg

Power, not torque
 

The Drill motors have much more power: .87 N*M/2 * 19670RPM/2 *2*PI/60 = 450 Watts

Chiaphua power = 500RPM/2 *2.2 N*m/2*2*PI/60 = 317 Watts

Hope this clears it up. In other words, if you gear the drill to the same output free speed of the Chiaphua, the drill will have more torque.

-Paul

but the chiaphua is bigger! that means it MUST be better?!

heh, go small but powerful. If only we could replace out chiaphuas with more bosch drill motors.

Anyone want to trade (just kidding, i read the rules)

Are you sure about this? The motors aren't turning when they are stalled, so you cant use RPM and stall torque together...?

Greg

If you check today's team update, it has something about reusing motors, so I take it as the motors you are allowed to reuse are essentially the same, while the motors you can't reuse are different.
You CAN reuse the Chalupa/Atwoods and Globes, so I'm guessing they're the same.
You CANNOT reuse the Fisher-Price, drill-motors and window motors, so I'm guessing that means they're different

Im going to have to agree with those that think the Chips are more powerful. My reasoning does have to do with the size of the motor, but of the windings. Since the Chip is bigger it MOST likely has a larger gauge wire for the windings and can draw more power without heating up as much and is less likely to blow the breakers. And even if the chip doesn't have larger gauge I'm pretty sure the its has more windings and probably more sections (I know theres a more technical term im trying to say the amount of coils on the armature itself) If someone is willing to take one apart to see whats really in there that would be great. I don't think my team would appreciate me taking it apart since i will most likly not be able to get it back together.

The number of turns is how many times the wire goes around the armature. Less turns means more power/rpm. The winding is the number of strands in the wrap. Usually between one and four. More strands will give you more torque at a higher RPM, less strands will give you more torque at a lower rpm for more "punch" As for why things work ou this way, I really don't know. This is just what an expert in the industry told me.

Running the numbers on the two through the Motor Calc spreadsheet from last year and using the drill specs found in this post:
I get a peak power of ~450W for the drills and ~300W for the Chiapuas.

Stall torque at our proposed gear ratios is 106N-m vs 80N-m

It is RIDICULOUS that we don't have spec sheets!!:ahh:

Absolutely Positive
 

GregT,

Believe me when I tell you that the calculation for DC motor max mechanical power is approximately:

PMax = (Tstall/2) * (FreeSpeed/2) *(2*PI/60)

The 2*PI/60 is the conversion from RPM to rad/sec which will give you power in Watts. This calculation is used to determine the peak motor mechanical power.

To those that agree with GregT: In this case size doesn't mean anything. The drill motors have more power than the Chiaphuas no doubt about it.

-Paul

Trust Paul on this one
 

I would go with Paul's calculations on pretty much anything,
any doubts go look in the white papers at the CCT!!!!!

Chalupas
 

NOTE: Chiapuha, Chippawa, Atwoods, etc. will henceforth be known as "Chalupas"

The difference between the Bosch and Chalupa motors is where they develop their power (torque) just like in automotive engines. Truck engines (Chalupas) develop huge amounts of low-end torque, but don't do too well at high speeds and need to be geared up substantially. An RX-7's rotary engine (Bosch) gets crappy low-end performance but does great at high speeds. I don't know how different the new drill motors are, but going by last years specs it comes out like this:

The Bosch motors (sans gearbox) have insanely high rpm but crappy torque. Also, the torque they do have is only developed when running full-bore.

The Chalupas have great low-end torque, with decent speed.

The advantage of the Bosch motors is that with the included gearbox, they can be slightly more powerful than the Chalupas (approx. 340 watts to 320 watts by last years specs)

The disadvantage is that their is an ever so slight lag from when the motor spins up to 20,000 rpm, to when the power comes out of the gearbox at 400-1500 rpm. With the Chalupa, you can use a simple 1:7 reduction, and have all of the power exactly when you need it.

Personally, I perfer the Chalupa's because I think they are easier to work with, and the difference between the two motors is negligible.

But if what everyone is saying is true, that the Bosch's this year are considerabley more powerful, then the drill motors may be the best bet.

Background for Paul's Calculations
 

Paul's calculations are correct. I threw together a quick explaination of the math behind it. I hope this helps anyone that still doubts his calculations.

-Chris

could you put that in a mac-compatable format please?

Stupid macs

PDF Version
 

I attached a PDF version to this. If you can't open this, let me know.

-Chris

Question about Paul's calculation
 

Just wondering. Since the circuit breaker on the drill motor is a 40 amp, are TStall/2 and FreeSpeed/2 really the correct operating points, since they imply a current draw of around 63 amps, which will blow the breaker? Seems like TStall/3 and and FreeSpeed/3 are more appropriate, or am I just confused? Or do people just hope the breaker takes longer than 2 minutes to blow? If this change is right, it reduces the effective power available by a factor of 4/9, or to about 44% of the absolute maximum power.

Thanks for letting me debug my meager motor knowledge here.


-- Jeff

You Got It!
 

You actually hit the nail right on the head! I was just demonstrating that the drill motor is more powerful than the Chiaphua. If you look at the following whitepaper, it will tell you all you need to know. It is my presentation at the Novi Kickoff in Michigan.

http://www.chiefdelphi.com/forums/pa... SC&sort=date

This should clear up a lot.

-Paul

Thanks
 

Thanks for the excellent upload. Really helpful stuff.


-- Jeff

Paul's calculation clarification
 

I would recommend that anyone hazy on this stuff take a look at Paul's presentation. I had the sign of the slopes wrong, so my earlier remark that the drill motor power @40A should be 44% of the maximum power was incorrect. Turns out to be more like 82% of the maximum power (which is much nicer). Thanks again, Paul.

-- Jeff

Question on Paul's Presentation
 

In the derivation for the maximum velocity near the end of the slides, it defines a 0.9 for "drive friction slowing the robot down". However, there is already an "eff" (efficiency) defined for drive losses. Is the extra 0.9 meant to account for rolling friction, or something else?


-- Jeff

:confused: So what is the torque of the drill motors at high and low speed?:confused:

Fudge Factor
 

It is a total fudge factor accounting for the loss of speed due to drive friction.

If you notice, only the torque is effected by efficiency. So, in theory, you could achieve the free speed of the motor. In reality, the drive friction will also slow you down to something less than free speed.

The actual equation that this comes from is:

F= ma + Ffdrive

You can derive top speed from this equation. Ffdrive is the friction losses in the drivetrain. What we do is disconnect the motors and pull on our robot with a spring scale at constant (approx.) speed.

Historically, we see 10% losses in the calculated free speed.

-Paul

Figure it out yourself
 

BerserkerSpyke,

Read my presentation. Use my motor numbers. Take apart the transmission and count the teeth in the planetary gearbox. Use the equations I gave you in the presentation and determine it yourself.

The reason I don't have the transmission numbers is due to the fact that we will not be using the transmission. We make our own.

-Paul

Also, I got a lecture note I give to my students when I teach them about motors. It's here:

http://www.chiefdelphi.com/forums/sh...threadid=15479

I will upload an updated one really soon that fix all the grammar error in it, but this one should show you the correct information. It's basically base on Chief Delphi's motor presentation, only the missing details from the power point.

hmm looks like we will have to beg steal buy or borrow a tach and a torquometer. no clue how to spell that.

I wasn't doubting you, just making sure :)

The advantage of the "Chalupa" motor is it's ability to run at 100% duty cycle (or closer to 100 then the drills)? I'm assuming it is larger because the winding wires have a larger radius giving them less resistance...?

Greg

Answer to BerserkerSpyke
 

See the attached file. I modified a slide in Paul's presentation to deal with the high and low speed modes of the Bosch drill motor.


-- Jeff

A torquometer?????? All you need to calculate torque is a shaft attached to the motor at the length you want your units at and a scale.

Drill transmission
 

Jeff,

Good job on adding the drill transmission numbers. I will add them to my preso.

It doesn't look like you included efficiency of the gearbox in your torque calculations. In high torque, it should be .95*.95*.95 and in low torque it should be .95*.95.


Paul

Efficiencies of Bosch Gearbox?
 

I thought they'd be included automatically, since I used the output RPM (450, 1500) instead of the actual RPM calculated by the 42.62:1 and 12.07:1 gear ratios (which give you 461 and 1629 RPM, respectively). But I'm often wrong.


-- Jeff