01-01-2008 15:40

lukevanoort

Re: paper: JVN's Mechanical Design Calculator (2008)

Note to people who download this: the divide by zero error on the rotary mechanism page is due to a single quote in the motor speed box. Fix that and it works. Other than that, this is very nice. I'm not going to delete my copy of the old version (that modeling feature is quite nifty), but this one will probably end up getting used more chiefly due to quicker loading and the updated specs, among other things. One question though, what do you mean by "# of intake sides?" I can see this as having a couple of meanings.

EDIT: I was looking through the specs, and I am curious which ones were experimentally determined and how. I ask because the small chiaphua and FPCIM have specs listed that are quite different from the ones I memorized out of the FIRST motor documentation.

01-01-2008 15:43

Madison

Re: paper: JVN's Mechanical Design Calculator (2008)

This is a great update, John. It hides a lot of the behind-the-scenes stuff of the original that may have made it seem really overwhelming to some folks, but I agree that it's nice to have the old sheet on hand, too, when someone wants to get a better handle on what's happening to make these things we build go.

01-01-2008 16:29

Holtzman

Re: paper: JVN's Mechanical Design Calculator (2008)

Rev 2 fixes a small mixup in the 1-speed tab. All better now.

01-01-2008 16:47

lukevanoort

Re: paper: JVN's Mechanical Design Calculator (2008)

I've been poking around a bit more in the spreadsheet, and I'm loving this current draw tweaking tool, that is a pretty awesome addition! (Especially for one speed drive systems)

01-01-2008 17:30

AndyB

Re: paper: JVN's Mechanical Design Calculator (2008)

Wow, this is really cool John. Great job.

06-01-2008 14:48

gurellia53

Re: paper: JVN's Mechanical Design Calculator (2008)

this is awesome!

One question though, to get the Drivetrain "Equivalent SuperMotor" Specs for 2 CIM motors, do you just double all the values for the 1 CIM except free speed?

14-01-2008 13:30

JesseK

Re: paper: JVN's Mechanical Design Calculator (2008)

Just put 2 Motors per gearbox and that will do it right.

Excellent spreadsheet, I finally have the almost incontravertible facts I need to explain to other mentors why I chose the designs I did instead of intuition and research.

edit:
On the Linear Mechanism tab, it's easy to add the peak power right next to the Max Loaded Current Draw -- Multiply D23 * C19.

20-01-2010 02:07

JVN

Re: paper: JVN's Mechanical Design Calculator (2008)

I just uploaded a version with the 2010 motor specs, which I shamelessly borrowed from Mark.

Lots of fun gearing calculations to do this year...
Your mileage may vary.

-John

20-01-2010 03:48

=Martin=Taylor=

Re: paper: JVN's Mechanical Design Calculator (2008)

I used the "rotary mechanism" app to calculate gear ratios for our winch.

The data we got from our prototype was close to what the design calc gave us. Thanks JVN!

20-01-2010 10:56

kramarczyk

Re: paper: JVN's Mechanical Design Calculator (2008)

Gosh, I wonder if driving over the bumps plays into the drivetrain gearing?

23-01-2010 10:52

Chris is me

Re: paper: JVN's Mechanical Design Calculator (2008)

This calculator just saved a drivetrain

Assuming I used it correctly.

23-01-2010 11:09

kramarczyk

Re: paper: JVN's Mechanical Design Calculator (2008)

Can you share the lesson?

23-01-2010 17:52

Ken Streeter

Re: paper: JVN's Mechanical Design Calculator (2008)

FYI, I the RPM specifications for the 2010 Mabuchi motors in this spreadsheet are off. It looks like the cut-and-paste from Mark's spreadsheet grabbed the wrong column for RPM of these motors.

The spreadsheet from 20 Jan 2010 needs two corrections on the first page (specs):
* RPM of Mabuchi RS555SH-2670 should be 4500 RPM (rather than prior entry of 471)
* RPM of Mabuchi RS555VC-3754 should be 4100 RPM (rather than prior entry of 429.4)

10-02-2010 13:09

Bill_B

Re: paper: JVN's Mechanical Design Calculator (2008)

While I was figuring out how to use this workbook, I noted that the orange areas correspond to motor specification data in the "specs" sheet. However, the table in Specs has the column "peak power" first instead of the operating voltage as required on the calculation sheets. So I increased the table to accommodate the voltage first and the power last (since I cannot find that value being used elsewhere in the workbook.)

Next up, I changed the formatting of the specs table entries from "text" to numbers, more or less at Excel's urging. Then I defined named ranges for the specification data on each row of the table. I think this will allow the orange input areas to be changed to controls that select the motor specifications from the specs table. I haven't done that yet. In the meantime, it is easy to select the named range for the desired motor, copy, navigate the sheet of interest and paste values into the orange area. This will reduce transcription error for entry.

Does anyone see anything basically wrong with this approach so far? Is anyone interested in getting my modified version?

10-02-2010 13:38

Collin Fultz

Re: paper: JVN's Mechanical Design Calculator (2008)

This is basically what I've done with the version I have on my computer. I think the reason "Peak Power" is first on the specs sheet is because it is the most important motor characteristic when you're trying to decide which motor can do which job. However, it is a derived number which isn't needed for any of the calculations on the other sheets, thus you don't have to copy it over.

What I did was put in a cell where you just pick which motor you want to use from a drop-down menu on each sheet and it automatically populates the requried information (free speed, stall torque, ...) using a lookup table. While mostly trivial, it allows me to play around with different motors without having to jump back and forth between sheets.

07-04-2010 22:53

Rion Atkinson

Re: paper: JVN's Mechanical Design Calculator (2008)

Sorry for posting in this decently old thread. But I felt that this was the best place.

I can not figure out how many Amps per motor a typical gearbox should have. It's very possible that my coefficient of friction is to high. (I didn't touch the default of 1.4) When I plugged in the specs for a typical toughbox with 1 CIM each. And then the 8 inch wheels from this year. I got 221 amps per motor. I'm fairly certain that this is WAY to much of an amp drainage from the battery that only has 18 amp hours. Can anyone help me out with this?

Also, on a semi-side note. What is the typical amount of total amps a drivetrain should pull?

Thanks,
-Rion

EDIT:

Could I get a copy of this by any chance?

11-01-2011 01:31

JVN

Re: paper: JVN's Mechanical Design Calculator (2008)

I just uploaded a 2011 version with the new motor specs. Nothing exciting, but it may save you a few minutes.

-John

11-01-2011 13:00

Dad1279

Re: paper: JVN's Mechanical Design Calculator (2008)

More like Hours/days, and smoked motors.

Thank you John.

-Alan

11-01-2011 13:21

Chris is me

Re: paper: JVN's Mechanical Design Calculator

Aww. I hate it when the numbers tell me that my seemingly perfect solution won't work.

20-01-2011 13:35

jhouser

Re: paper: JVN's Mechanical Design Calculator (2008)

Hi John,
I'm wondering if you would mind if I sent this to PTC to convert to Mathcad?
I don't know if it would be better or worse, but it may be interesting to see. I can post it back here once I get it.

By the way, this is still a fantastic resource for teams!

Thanks!

24-01-2012 17:48

jason701802

Re: paper: JVN's Mechanical Design Calculator

Shouldn't the "Roller Diameter" in the intake mechanism sheet be roller radius, it seems to disagree with my hand calculations and the linear mechanism sheet?

The output of unloaded intake velocity is "=E27*PI()*2*D19/360*(G19/2)" where E27 is the unloaded intake speed in degrees/sec, D19 is roller diameter, and G19 is the number of intake sides. (degrees/sec)/360 gives us rev/sec, then multiplying that by pi and the diameter gives the linear velocity of the belt, but that is then multiplied by 2. I might be missing something, but it seems that either the extra 2 needs to go away or the roller diameter should be labeled radius.