# Paper: JVN's Mechanical Design Calculator 2016

So I’ve been trying to use the linear mechanism tab and for some reason the current draw per Motor isn’t calculated using the gearbox efficiency, am I using an old version or is their a reason for that?

It depends on how your intake is built. # Intake Sides is used to calculate the speed - a one-sided intake implies that the opposite side of the intake is stationary (and that the game piece is approximately round at least in the plane of the intake wheels). Note that the way Drag Load is used, this is “drag load per gearbox”. So, if you have the most common intake this year of independently powered dual intake (4 motors in your case above), you would only put half the total drag load here. If you have both intake sides powered off a single gearbox (2 motors in your case above), you would put the full drag load here.

It doesn’t make much sense to me, either. The gearbox efficiency only affects (in dependency order): Stall Load (G17), Loaded Linear Speed (F13) and Loaded Arm Time (G13). The rotary and intake mechanisms do the same thing. Caveat: Arm Time is based on “terminal velocity” only and does not account for the time required to accelerate the load from a stationary position to that terminal velocity.

Looking at a couple of drive tabs (Custom 1 and Custom 2), the drivetrain efficiency IS used to calculate pushing current (and nothing else) by dividing the traction limited torque calculated at the motor by the efficiency to get the motor torque required and the current from there. This usage I get.

If you want the gearbox efficiency to be used the same way in the linear mechanism tab, change the formula in F17 by inserting the four bolded characters as follows:

``````=((((F\$5*C\$8)-(G5*C\$8))/(E\$5*C\$8))*(F\$8*G\$8**/D\$8**/2*(C12*C13*C14*C15/D12/D13/D14/D15)/(0.2248*39.37))+(G\$5*C\$8))/C\$8
``````
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Are there plans for the calculator to support the NEO Motor in the near future?

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Still hoping for this!!

You can make your own NEO motor in the calculator.

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Just go to the Data tab and enter in the stats for any motor you want, and they will populate in the drop down cells for each tab you use.

Does anyone have a google sheets version of the calculator available? My school issued laptop doesn’t currently have Office on it

i got you.

edit: shared it with you on your gmail…

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Alternatively, the calculator made by Aren Hill and Dillon Carey is native to google sheets and its pretty useful too. FRC Mechanical Design Calculator (By Dillon Carey and Aren Hill)

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Hadn’t tried it yet but wanted to ensure it doesn’t lose any functionality.

I’m planning to keep the links at https://johnvneun.com/calc updated.
I just fixed them to reflect the changes to Chief Delphi.

I have plenty of updates to the sheet halfway done, but my 2018 “got away from me” due to some job changes. My ambitions keep seeming to over-reach my capability. (maybe this is a good opportunity for me to remind myself to “build within my limits.”)

-JVN

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JVN’s calculator works fine after import in my experience. Some of the image/text formatting goes weird is all, don’t let that scare you.

The iterative-calculators for sprint distance that Ari and Alpard have built in Excel (at separate times) do not work in Google Docs. Fortunately, Aren & Dillon’s calculator is native to Docs and does Follow SPang’s link above.

Aren & Dillon’s calculator goes into significantly more depth, so I find JVN’s easier to teach with more inexperienced students - basically, JVN makes a larger number of invisible assumptions, on things that don’t matter to >95% of teams, so we can move faster to answer questions like “what gears do I need to use 6” wheels to move 14fps" instead of getting side tracked on exact DC wire sizes and run lengths.

Is there a spreadsheet calculator with 3 Neo as an option? Has anyone created one? Please share it if you have

JVN Calc.xlsx (1.4 MB)

As the first page says – Note, this calculator is provided as a design reference ONLY.

Great! Thanks so much.

I think it’s worth mentioning that @JVN has announced he will be making no further updates to the calculator.

As someone who has maintained something far more frivolous for almost (but not quite) as long, thank you for the years of maintaining a cornerstone of the semi-enlightened-or-better robot designer world.

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Hi everyone, I’m now using this Design Calculator to make an Intake but I have the question about how to obtain de Drag Load on Intake Mechanism, I don’t understand what it is and how to calculate it

In most cases (as in when you’re picking up an object off a flat floor) this will just be the weight of the object. If it’s on a incline, the drag load will be smaller, but it’s really just safest to put this value at the weight of the object.

The bottom line is this value is going to be nearly impossible to actually calculate. It’s very dependent on the geometry of your intake, the object you’re trying to intake, and a few thousand other factors.

My suggesting for calculating intakes is to look at the mechanism’s free speed. The rule of thumb is you want it to be at least double the speed of your drivetrain so you can intake while driving at full reverse (instead of having to wait to finish intaking before beginning to reverse). Then as long as you have a reasonable amount of power, you should be fine.

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