14-01-2005 20:31

Arefin Bari

Re: pic: 2005 Motor Information

Thanks so much karthik. This will help a lot of us.

-Arefin.

14-01-2005 20:35

pakrat

Re: pic: 2005 Motor Information

you are a genius! Thank you so much!

14-01-2005 21:22

Ken Leung

Re: pic: 2005 Motor Information

I noticed the Fisher Price motor peak power is 407W, while the motor with a gearbox is 90W peak power. I cannot imagine how bad a gearbox it would take to reduce the power from 407W to 90W.

I know there has been some confusion regarding part numbers and spec sheets, so that might be the reason. Any clarification will be great!

14-01-2005 21:30

Madison

Re: pic: 2005 Motor Information

I can't do it, or it'd have been done already -- but, can someone move this thread to the Motors forum and sticky it to the top?

14-01-2005 22:29

Joe Johnson

Re: pic: 2005 Motor Information

The F-P with the gearbox is obviously wrong.

The Data on the Taigene is strange for 2 reasons: #1 double data, which one is right. #2 it is at 10.5V

I suppose this is from a Delphi spec -- the motor is used solely by Delphi on Power Sliding Door or Power Sliding Door applications. The range is the way we tend to spec things in the auto world and the 10.5V is the voltage that this application happened to want the data shown...

It is easy enough to convert the data to 12V, but the range is more problematic.

I will see if I can get someone (probably Artur Ostrowski who works at Delphi with me but actual helps design team #469's robots -- Chief Delphi can't get all the good robot designers in our building ;-) to pull the print or perhaps even see if they have some dyno data on this motor next week some time.

One more thing:
There are a lot of notes that talk about the 407W being a scary number for that small motor. Find these notes and read them before you decide to actually try to get that much power out of those little beauties.

Joe J.

14-01-2005 22:55

Max Lobovsky

Re: pic: 2005 Motor Information

The two sets of Taigene data are for clockwise and counterclockwise operation as is labelled ("cw" and "ccw")

15-01-2005 07:06

Paul Copioli

Re: 2005 Motor Information

The Globe motor data is also wrong. The gear ratio is misplaced. I think the torque data is for the motor only. I will track it down.


-Paul

15-01-2005 08:02

ZACH P.

Re: 2005 Motor Information

The Van Door motor has advanced timing in the CW direction, hence the double specs. Also, to me the specs for the Fisher Price motor with gearbox seem to be taken at 6V, while the motor without gearbox are taken at 12V.

17-01-2005 10:31

Joshua May

Re: 2005 Motor Information

Are there any updates for the correct motor information yet?

17-01-2005 21:16

Nuttyman54

Re: 2005 Motor Information

Anyone have the power curves or a spreadsheet of motor specs for this year's motors?

17-01-2005 21:36

Madison

Re: 2005 Motor Information

Did you even read the thread you posted to?

The first post in this thread documents the specifications of the motors provided in the kit as provided by FIRST. You can generate power curves using this data.

17-01-2005 22:16

petek

Re: 2005 Motor Information

Here's the spreadsheet I'm working from. I stole karthik's chart and tweaked it a bit - there are some curves on the second tab. Thanks also to JVN for info in his DesignCalc workbooks. I fudged the FP gearbox torque: multiplied the motor torque by the gear ratio (the listed torque is 69% of the motor only, so I used that for the efficiency factor).

I can't say I have a whole lot of confidence in some of the data supplied by FIRST, however. The CIM data looks good, but as Dr Joe, Paul and others have noted, there are some glaring discrepancies for some other motors. I can't reconcile the torque they give for the van door motor with what we did with it on our tower last year. I guess having questionable data is better than no data...

18-01-2005 12:39

Gary Dillard

Re: 2005 Motor Information

Question from the floor?

Why is the stall current on the FP motor different from the FP motor with gearbox? If the motor is stalled, how does it know or why does it care that there's a gearbox attached to it? Shouldn't it have the same resistance and stall current whether you stop the rotation on the output shaft, or the motor pinion, or anywhere in between?

Oops, I see that Mike Betts asked the same question in the FP pinion thread. I'll wait and see what all the empirical data provides.

18-01-2005 18:09

ZACH P.

Re: 2005 Motor Information

As I said earlier, with the power of the FP being roughly 1/4 with the gearbox of the power without the gearbox, and the stall current about 1/2 with the gearbox I feel it is safe to assume that the w/ gearbox specs were taken at 6V, the motor's intended voltage.

19-01-2005 20:37

jaustin

Re: 2005 Motor Information

Can anyone help with a question related to the "Intro to Motors" [Heinzmann & Mikus] presentation posted on the 2005 Kick Off Workshop List? Near the end they list a "simple strategy" of assuming a higher motor resistance to calculate a new power curve. They then say to "operate at half the new peak power". I'm wondering if it was supposed to say "... half the new peak torque". Half of the already greatly reduced power seems REALLY low.

Thanks!
Jeff Austin
Team 372
Mukilteo, WA

21-01-2005 12:32

ErinColleen

Re: 2005 Motor Information

So are we in agreement then with the specs that were in the excel sheet?

~Erin

21-01-2005 12:58

petek

Re: 2005 Motor Information

I updated the spreadsheet, with a few corrections and new data - attached here. I haven't heard from Brandon if I can update the link in my post earlier in this thread.

21-01-2005 14:26

Joe Johnson

Re: 2005 Motor Information

I would use THIS SPEC for the Taigene motor.

Joe J.

27-01-2005 17:04

sciguy125

Re: 2005 Motor Information

Hold on a sec...
I think the oz-in numbers are wrong on the van door, jideco and denso. They're WAY too low. lb-ft numbers look right though.

ok...maybe I should investigate before I speak... When the numbers were converted from Nm to oz-in, they used mNm to oz-in conversion. I've fixed them, assuming that the spec actually is Nm and not mNm.

27-01-2005 22:22

petek

Re: 2005 Motor Information

Good catch! Funny how simple conversions can get screwed up at 10 at night... I hadn't paid too much attention to the oz-in numbers (obviously).

05-02-2005 12:06

Tom McCurdy

Re: 2005 Motor Information

I have had members of our team who are saying the gear ratio is wrong still instead of 1:124 for fisher price is 1:12.4 would this make any difference.... basically right now we are looking for the torque on the fischer price motors

05-02-2005 13:54

petek

Re: 2005 Motor Information

It would appear there are a couple of other errors in the data:
- According to other threads, this year's Van Door motor apparently has a no-load speed of about 50 rpm;
- The Globe gearmotor stall torque is way off - it is lower than the window motors', but I don't know what is the real value.

If and when I get "real" data, I'll update the spreadsheet. Sorry for posting bogus data.

08-02-2005 17:18

HPA_Robotics_13

Re: 2005 Motor Information

I don't understand this data.
I find it impossible to believe that the torque from the FPs is less than one Nm. Can someone explain what "stall torque" is? And then, what is the motor's "normal" torque?

08-02-2005 19:41

jgannon

Re: 2005 Motor Information

The torque from the FP without the gearbox is less than 1Nm. With the gearbox, it's a whole lot more. The data for the FP with gearbox is wrong on that sheet, as pointed out by Dr. Joe earlier. Stall torque is the amount of torque provided when you are at 0 RPM. When you are at maximum RPM, you have 0 Nm of torque. There really is no "normal" torque... it depends on what speed the motor is going. I think there are power curves for the motors around here somewhere, which will tell you how much torque you get for a certain speed. If not, you can probably construct one yourself.

09-02-2005 00:38

sciguy125

Re: 2005 Motor Information

As far as I know, brushed motors are linear. Plot torque vs speed. 0 speed, stall torque is your first point. Full speed, 0 torque is your other point. Draw a straight line and you have your "curve."

09-02-2005 00:57

russell

Re: 2005 Motor Information

I dont think thats right. Dont know why, but something seems funny about it. For I think because you are plotting the speed at stall at the beginning then the rest of the time you plot the free speed. Something like that.

09-02-2005 01:27

Tristan Lall

Re: 2005 Motor Information

In fact, sciguy125 is mostly right, except that usually, you plot speed vs. torque with stall torque (the max.) at the extreme right of the x-axis, and the torque corresponding to free speed (i.e. 0 torque) at the origin.

Maybe you were thinking of current?

09-02-2005 03:55

HPA_Robotics_13

Re: 2005 Motor Information

So, then what is the stall torque on the Fisher-Price motors (with gearbox)?

09-02-2005 10:19

jgannon

Re: 2005 Motor Information

We don't have any official numbers, but Paul Copioli figured the gearbox reduction to be about 180:1. Take the torque listed on the data sheet for the motor alone, multiply it by 180, and subtract a bit for energy losses. That will give you a ballpark figure.

09-02-2005 10:43

Paul Copioli

Re: 2005 Motor Information

Please see this thread, post #23:

http://www.chiefdelphi.com/forums/sh...light=Fish er

I took apart the gearbox and counted teeth.

09-02-2005 16:09

HPA_Robotics_13

Re: 2005 Motor Information

My AP physics teacher (along with my school's freshman physics teacher) just explained to me that gear reduction does not do anything to change the motors torque. Thus, after the 1:180 reduction of the gearbox and then another 1:10 to get it down to 12 rps, your system still has only .324 Nm at 6V.
We decided that a system using the fisher price motors should have a worm gear to give it the torque that the motor lacks to lift a 1.5 meter 100+ newton arm.

Am I just completely ignorant to have assumed that you would be driving the arm from a direct chain link to the FP gearbox shaft or is my teacher wrong?

I must be missing something becaue many people here, such as jgannon, have explicitly stated that the torque is greater after reduction.

09-02-2005 16:53

ChrisH

Re: 2005 Motor Information

Your teacher is right when they way that adding gear reduction does nothing to change the motor's torque. A motor with .324 Nm of torque will always put out that much torque, AT THE MOTOR SHAFT.

However adding a gearbox to the system changes the system and therefore the output will change. Power = Torque x omega, where omega = rotational speed in radians/sec. Since the motor is putting out a given amount of power at a certain speed, and we can assume that power in to the gearbox is equal to power out (we'll neglect losses for the moment), then reducing the RPMs will result in a proportional increase in torque.

As I've said numerous times before, design your systems so the motor is operating at no more than 25% of stall torque and at least 75% of free speed and you should be fine. Electric motors like to run fast and this is especially true of the FP motors. By setting up you system this way, the motor actually starts producing more power when it bogs down and is more likely to pull through should it meet a higher than expected load.

Running the motor that fast also means that there is lots of gear reduction. The gear reduction helps reduce the holding torque required to help the arm hold position. If you go far enough with the reduction, then the inherent braking of the speed controller will be enough. If you can't go that far, then you are at least reducing the amount of voltage and current your motor requires to hold position. Either way you are helping your motor to "live long and prosper".

Keep 'em cool, run it fast!

09-02-2005 17:39

HPA_Robotics_13

Re: 2005 Motor Information

Thank you!

(PS. so, then, assuming your gear reduction is sufficient, the worm gear stuff isn't necessary, I suppose.)

09-02-2005 17:46

HPA_Robotics_13

Re: 2005 Motor Information

My teacher says you're wrong...

I'm going over to my garage right now to do a test, and find out experimentally.

I am inclined to believe the people involved with FIRST in this case, as they have physical experience with the issue.

Thanks, ChrishH

09-02-2005 19:33

ChrisH

Re: 2005 Motor Information

I hope your test works out OK and that you don't burn anything up. One of our former students, now a graduated engineer and mentor in his own right, pointed out recently that the only time we have ever fried an FP motor was in my garage, doing torque vs speed tests. I'd forgotten about that. It must have been back in 99 or so.

Testing is generally the best way to convince yourself that something is or isn't true. However you can't necessarily test everything for yourself, if only because there are too many things to test! In that case you often have to rely on the experience of others. In this case I can prove the answer mathematically as well as practically, and there are generations of engineering and science textbooks to back it up. The case is pretty solid, though your teacher kind of scares me. If this person is teaching Physics, they really should understand the concept of the lever. It is the Basic Machine that is operating here and any Physicist should recognize it as such. I hope it is just a lack of mutual understanding as to what you are really asking.

Christopher H Husmann, PE (Mechanical)

10-02-2005 04:21

HPA_Robotics_13

Re: 2005 Motor Information

I think it was pretty much a lack of understanding.

I played around with the motors, gearboxes, and some sprockets and convinced myself that the reductions I was planning to do to have the FP run our arm will in fact have more than enough torque, with one FP motor, to lift the arm.

Just to make sure I understand: The "stall torque" of a motor is the torque it provides (or the torque it takes to turn it) when the motor is not moving. So if I am to take a motor that is not hooked up to any sort of power source, the torque I apply to force the output shaft to rotate is that motor's "stall torque."

Thus: The reductions on my robot's FP system are such that with a full load (a tetra at the end of the arm) and no power, the system does not move. This means that I am putting no load on my FP motor when my arm is stopped at a 45 degree angle. I am producing no heat! This means that I do not have to worry about overheating my motors, because I have done such a large reduction on my system.

Does this all sound valid?

10-02-2005 10:53

petek

Re: 2005 Motor Information

Sorry, but Stall Torque is the torque developed by the motor at the specified supply voltage with the rotor held stationary. Another way to look at it is the torque load applied to the motor which causes its rotation to stop (stall) when energized.

If you are relying on the de-energized motor magnetic torque (and drive friction) to hold your arm stationary, beware of unexpected loads caused by inertia, other robots, etc. and of changing system losses (gears wearing in, etc.). You may find your arm starts dropping at unpleasant times - like when the buzzer sounds and you just got clear of the tetra you capped with.

10-02-2005 12:05

HPA_Robotics_13

Re: 2005 Motor Information

Thank you for the clarification, petek.

How would one normally go about having the arm stopped at a certain height, then? Hopefully you don't keep going up until the torque of the arm is such that the motor reaches stall torque so the system stops there. What is the usual method for this? Obviously, I want to be able to stop at various positions.

10-02-2005 12:36

Zanella BR

Re: 2005 Motor Information

Really great job!

Unfortunately, when I discovered this, our robot was almost done...

10-02-2005 15:38

sciguy125

Re: 2005 Motor Information

I was plotting speed as the independent (x-axis). I should have mentioned that you can just find the inverse to switch the axes.

10-02-2005 22:31

MASherry

Re: 2005 Motor Information

if u guys want motor specs or a motor spec clauculator..go to www.montclairrobotics.org and click downloads u can d/l the spec sheet for each motor or the calculator which calcuklates the torque and speed at a given amperage... (at least i think thats what it does)

19-02-2005 00:34

Nuttyman54

Re: 2005 Motor Information

Sorry, I didn't explain myself. I needed the CORRECT power curves for the Jideco, seeing as the ones FIRST gave us for it is incorrect. I have double checked and also confirmed with Ken Stafford, an ME Teacher at WPI and mentor of team #190.

02-03-2005 11:58

the_short1

Re: 2005 Motor Information

ok.. i have a little issue...
the globe data seems to be off
for the runnign current: 0.58 is right, i tested that b4..

but when i tested the stall current (we were thinking on using a resetable fuse, instead of limit switches for our manipulator instead of running wires etc)

.. it only ammounted to aprox 5amps... not 20.. . i was using a mastercraft multimeter with 10A max . .. i also tested our robot running in the air full throtle at 11A... .so...meter can go a lot higher then 5... is anyone else getting less then 20A for stalling?

also if u know any vehicles (specific) that i could find a Taigene motor out of (at a junk yard etc).< please email me short1@gmail.com. .thx