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Complete Lift Designer

Torque, speed, stability and the shaft carrying it, checked together. A lift can pass all four individually and still fail, because raising the load is what makes the robot tip.

Inputs

The lift

lb
in
lb
in
in
°

Used for the speed figure.

Power

The robot

lb
in
in
in

Results

Does it work?

—

Torque needed, worst case

—N·m

Torque available

—N·m

Of what the motors give

—%

Time to raise

—sec

CG with lift raised

—in

Tipping threshold, lift up

—g

Shaft safety factor

—

Raise the arm

Raise the armneededmotors
0%

A sketch of the lift, not to scale, starting level and sweeping up through your angle. The bars at the top are the torque the load needs at this angle against what your motors give; level is the worst of it, and the need falls away as the arm rises. Watch the balance point, the CG, climb too: the higher the load goes, the easier the robot is to tip.

The four checks

    How this is calculated

    Each of these four is covered on its own page, and each is easy to pass in isolation. Putting them together is the point, because the trades run against each other.

    Torque and speed pull opposite ways

    More reduction gives the torque to hold the load and takes away the speed to raise it. TheRequired Lift Torque page covers this in detail, including why the worst case is always with the arm horizontal. Here it is combined with the time to sweep through the travel angle, so a lift that holds beautifully and takes six seconds to get there shows up as the problem it is.

    Stability is the one that surprises people

    Raising a load moves the whole robot's balance point upward in proportion to the share of the mass that moved. Every tipping threshold divides by CG height, so the robot that was rock solid empty can go over the moment the lift is up and the driver accelerates.

    This is why the check belongs here rather than only on thetipping page. A lift is not just a lift; it is a change to the robot's stability that happens to carry game objects.

    The shaft is where it actually breaks

    Gearing down for torque multiplies what the shaft carries. A lift geared to hold a heavy load at long reach is exactly the mechanism most likely to twist a shaft, and the numbers are not close: a standard shaft yields at about 1.24 N·m and a geared-down lift can ask for ten times that. The shaft check has the detail.

    What to change when it fails

    • Not enough torque: gear down, add a motor, or shorten the reach.
    • Too slow: gear up, which costs torque, or accept it.
    • Tips over: lower the whole mechanism, lighten what rises, or widen the track. Gearing does nothing here.
    • Twists the shaft: bigger shaft, split the load across two, or move the shaft to the fast side of the gearing.

    Note that the third one is unaffected by everything that fixes the others. That is the reason for checking all four at once.

    Sources & assumptions

    Stall torque is published for the 100 RPM cartridge andderived for the others. Shaft strengths arederived from torsion theory with assumed material properties, as described on the shaft page. The friction coefficient isestimated, since VEX publishes none.

    Models a single rigid arm about one pivot. Four bar and DR4B linkages change the geometry, though the torque peak still lands near horizontal. Ignores friction and rubber band assist, which many lifts depend on heavily: a banded lift can hold far more than this predicts. Size the bands with the Rubber Band Assist calculator and subtract what they supply.

    The speed figure assumes the motors run at free speed, which they will not under load. Treat it as a best case and expect a real lift to be slower, especially one running near its torque limit.

    Every source the site uses, and when it was checked

    Save this run, and compare

    Keeps what is on screen so you can change something and see both sides of the change. Saved in this browser only, never uploaded.

    Make a notebook page

    Turns this calculation into a dated engineering notebook page: the setup, data, results, figures, working and sources, numbered and cited. You add the goal, the decision and the reflection in your own words, plus photos and sketches. Print it, paste it into Google Docs, or download a Word file or slides.

    My notebook

    Notebook page

    More
    Open My notebook

      This page

      Our own layouts

      A layout remembers how a page is set up: its type, its system, which parts print and which of your tables it uses. It never remembers a word, a number or a photo.

      Your team kept on this device
      Add someone to the team list
      Your words never written for you

      These are the parts a judge or teacher reads to see your thinking, so the page leaves them to you. Leave a box empty to get lined space for writing by hand. Start lines with "- " for a list. The notes under each box only count and point things out; they never change what you wrote.

      Rough notes

      Rough notes

      Rough notes

      Rough notes

      Rough notes

      Rough notes

      Rough notes

      Rough notes

      Rough notes

      The word counts can be measured against a target your team sets on My notebook. The reading level is Flesch-Kincaid grade level = 0.39 × (words ÷ sentences) + 11.8 × (syllables ÷ words) − 15.59. Syllables are counted by vowel groups, so the grade is an estimate of the school year the writing reads at. It says nothing about whether the writing is any good.

      One part at a time, with a clock. At the end of practice, while you remember it.
      How you tested your details

      Fill in what applies. These print as a small table under the method.

      Before and after

      Compare this calculation with a run you saved earlier on this tool (under “Saved runs”). The page shows what changed and by how much.

      A line through the data from your recorded table

      Pick two measured columns from the same table. The page plots them and draws the least-squares line, only across the range you measured.

      Robot log a CSV from the robot's SD card

      Load a CSV your robot saved. Pick the time column and up to three columns to plot, and type their units. Only those columns go on the page; the file stays on this device.

      Two versions' trials your data, compared

      Pick a column of recorded trials for each version, from this page or another saved page. The page shows both averages and a 95% range for the difference. The numbers are copied in when you pick them, so later changes to the other page don't change this one.

      Options compared your scores

      Score each option 1 to 5 on each criterion, and weight each criterion 1 to 5 by how much it matters. The page only multiplies and adds.

      Photos and sketches stay on this device

      Up to 4. Paste a screenshot with Ctrl+V, drop pictures here, or pick them. Photos are shrunk before they’re kept, and an unsaved page keeps them in its draft. Use Mark up to draw arrows, labels, dimensions and numbered callouts on a photo. Mark one photo Before and one After to print them side by side.

        Test plan written before testing

        Write this before you test: the question, what you expect with a number, and what result would make you drop the idea.

          Build steps our build

          One row per step, in order, so someone could rebuild from this page.

            Parts used our parts list

            Lengths in holes are also shown in inches between the end holes. Weights are only added up where you type them.

              Plan the cuts: packs every piece of one part (sizes in holes, or inches on the hole grid) onto whole sticks of the stock length you type.

              Ways it could fail our scores

              List the ways this could fail. Score how likely (1 to 5) and how bad (1 to 5); the page multiplies them and puts the biggest risks first.

                Designed against built our measurements

                What the CAD or the plan said, and what you measured on the robot. The tolerance is yours.

                  Changes from the last version our changes

                  What changed since the last version, why, and which result it was meant to move.

                    That page’s settings, results and first photo are copied in and set beside this page’s. The result each change should move is looked up on both pages.

                    Tasks our plan

                    What needs doing, who, and by when. Open tasks carry to the next meeting page until someone ticks them done.

                      The pages behind this idea our evidence

                      The pages in this notebook that show the idea being tried, measured or changed. A judge reading the claim can turn straight to them.

                        Time spent our hours

                        Who worked on this and for how long.

                          Session log what we did, as we did it

                          Notes taken during a session. The time comes from the clock when the note was taken; every word is yours.

                            Size limit does it fit?

                            Type the starting size limit from the current game manual, and the robot's size as designed or measured, in inches. The site doesn't store the limit, because it changes with the game.

                            What broke from your breakage log

                            The breakage log is on My notebook. Copy it onto this page as a table, as it stands now; later entries don't change this page.

                            CAD model which version this page is about

                            Paste a link to the model (Onshape, Fusion or anything else) and the name you use for this version. For Onshape, the page reads from the link whether it points at a saved version or a workspace that keeps changing. Nothing is fetched.

                            Your code
                            Comments notes for the team, not the page

                            A teammate or coach can leave a note here. Comments stay beside the page, travel with it in exports and links, and don't print unless you tick them under Include.

                              Sources you used besides this tool

                              Videos, other teams, manuals, people. The tool’s own sources are cited for you.

                                Sign-off
                                Include

                                Press a ? to see what an option is for, or read them all on How the notebook tools work.

                                What “The calculator’s figures” is for

                                The calculator’s own diagrams and charts, numbered as figures and drawn from your numbers. Judges look for pictures that explain a design.

                                What “How it was calculated” is for

                                The formulas and steps the calculator used, so a reader can check the arithmetic for themselves.

                                What “The calculator’s warnings” is for

                                Things the calculator flagged, such as a motor near stall. They’re quoted and credited to the calculator, so they never read as your conclusion.

                                What “The calculator’s notes” is for

                                The calculator’s plain-language notes on the result. Off at first, because they read like conclusions, and the conclusions on a page should be yours.

                                What “Lined space” is for

                                Ruled lines under any part you haven’t written yet, so a printed page can be finished by hand.

                                What “Writing space as” is for

                                The blank space for handwriting as ruled lines, a dot grid or quarter-inch squares. Dots and squares suit sketches and hand-drawn graphs.

                                What “A summary under recorded data” is for

                                The number of readings, the average, the spread, the lowest and the highest under each table you recorded, worked out from your numbers. It shows every run counted, not just the best one.

                                What “Words used” is for

                                A small box with the site’s one-line definitions of glossary terms the calculator used, for readers who don’t know them. It never looks at your own writing.

                                What “Robot at the time” is for

                                The Robot Profile as it was when the page was first saved, so weeks later you can tell which version of the robot a test was run on.

                                What “Long tables in full” is for

                                Long calculated tables printed complete on an extra page, instead of every few rows on the page itself.

                                What “Fit on one sheet” is for

                                Smaller type and shorter tables, aiming for one printed sheet. Use it when every entry in your notebook should be a single page.

                                What “Wider left margin” is for

                                A wider left edge, so the page can be hole-punched or bound without losing any words.

                                What “Larger type, for reading aloud” is for

                                Bigger print with more room between lines, for the team member who reads the page to a judge. It overrides Fit on one sheet.

                                What “Our rubric scores” is for

                                Your own scores against the rubric, on a sheet of their own, for checking a page before a judge does.

                                What “When this page was first saved” is for

                                The day the page was first saved, printed beside its date. It shows the notebook was kept while the work happened.

                                What “Teammates’ comments” is for

                                Prints the comments teammates left on this page at the end, marked as not part of the page. Off at first, because comments are notes for the team, not for judges.

                                What “Show every table and block” is for

                                Shows every table and block in the editor, not only the ones this type of page usually uses. It changes the editor, not the printed page.

                                Rubric check

                                  This checks what is on the page, not how good it is. Clear, specific writing in your own words is what earns the top marks.

                                  Preview, letter size

                                  Write it now

                                  Where this goes next

                                  Explore further on the full map

                                  Where the answers on this page can be used, and which tools could have given you the numbers it asks for.

                                  Comes after

                                  Required Lift Torquefills in your lift load hereLift Speed & Gear Ratiofills in your lift load here

                                  You are here

                                  Complete Lift Designer

                                  Where your answer goes

                                  Tipping & Wheelie Thresholdcheck sideways tipping and ramps, not just forward and backbrings your center of gravity height with itShaft Deflectionsee how far the pivot shaft sags and if the gears still meshuses your lift load againRubber Band Assist Calculatortake load off the motors with bands if the torque is marginalbrings your lift load with itWhole Robot Design Checkroll these numbers into a whole-robot check with speed and pushingbrings your center of gravity height with it

                                  a number carries across the next question it raises

                                  Keyboard shortcuts

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                                  Copy a link to these exact numbers
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                                  Letter keys do nothing while you're typing in a box.