The wheeled A-frame that throws 10 lb pumpkins
This is the full-size machine from 2023: a laminated 2x lumber arm on a steel pipe axle, an A-frame base on pneumatic wheels so the whole machine rolls forward on release, and a counterweight box loaded with weight plates. It throws 8 to 10 lb pumpkins. It was built in a driveway and thrown in a school parking lot in Colorado. Several dimensions were never measured, and this page marks each one instead of guessing.
Build walkthrough, YouTube
Specifications
At a glance
| Projectile | 8 to 10 lb pumpkin | measured |
| Counterweight | about 180 lb (from the build walkthrough) | estimated |
| Arm length | not yet measured | unmeasured |
| Short arm | not yet measured | unmeasured |
| Axle height | not yet measured | unmeasured |
| Sling length | not yet measured | unmeasured |
| Release angle | not yet measured | unmeasured |
| Best range | not yet measured | unmeasured |
How to read the values
- measured
Taken with a tape, scale or stopwatch on this machine.
- estimated
A best figure, not weighed or measured. Always written with "about".
- unmeasured
Never recorded. Shown as a gap on purpose, not guessed.
The 2026 build is being measured as it goes, so every row on its page should read measured.
Why it is built this way
Design intent
Why wheels
The base sits on pneumatic wheels so the whole machine can roll forward as the arm drops. A base that has to stay planted fights the throw, and a rolling base is also easy to move out of a driveway and across a parking lot. The wheels do make loading more awkward, and that is the cost of the choice.
Why a laminated arm
One long 2x board is not stiff enough for this job, and long clear lumber is hard to find. Gluing and clamping several 2x boards face to face gives a stiff beam from lumber that any yard stocks, and it spreads out any weak spots in the individual boards. If it ever cracks, it can be rebuilt with the same materials.
Why a plate-loaded box
The counterweight is a box loaded with weight plates, not a block poured in place. Plates change the load in small steps between throws, they go in and out by hand, and they can be put on a scale. That last point is how the "about 180 lb" figure gets replaced with a real number.
Drawings
Drawings
A arm B axle C counterweight box D wheel
[dim] = to be filled from the plans
A laminated arm B axle C eye hook D sling pouch
[dim] = to be filled from the plans
Build log
Build log
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Phase 01
Lumber and layout
Framing lumber and plywood were bought, cut and marked out in a driveway. Cut lengths for this build are not recorded on this page yet, so the drawings carry [dim] placeholders until the 2026 build is measured.
[photo: cut lumber and layout marks] -
Phase 02
Laminating the arm
The arm is built up from 2x lumber, glued and clamped face to face into one long beam. The sling attaches at the tip of the stack.
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Phase 03
A-frame and axle
The A-frame carries a steel pipe axle that the arm pivots on, and a tie plate holds the legs together. The weight plates for the counterweight box sit nearby in this stage.
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Phase 04
Counterweight box and wheels
The counterweight box is loaded with weight plates, and the base sits on pneumatic wheels. Red rope lashing and a white deck panel are visible on the finished machine.
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Phase 05
Sling and release
The sling is a sewn pouch with a cord on each side, hung from an eye hook at the arm tip. A release pin lets the pouch slip free, and the release angle has not been measured on this build.
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Phase 06
First throws
The machine was thrown in a school parking lot in Colorado with the 8 to 10 lb pumpkins listed above. Range was not measured, so the field results below read "not yet measured".
Field results
Field results
| Throw | Projectile | Counterweight | Range | Notes |
|---|---|---|---|---|
| 1 | 8 to 10 lb pumpkin | about 180 lb | not yet measured | [note] |
| 2 | 8 to 10 lb pumpkin | about 180 lb | not yet measured | [note] |
| 3 | 8 to 10 lb pumpkin | about 180 lb | not yet measured | [note] |
| 4 | 8 to 10 lb pumpkin | about 180 lb | not yet measured | [note] |
| 5 | 8 to 10 lb pumpkin | about 180 lb | not yet measured | [note] |
| 6 | 8 to 10 lb pumpkin | about 180 lb | not yet measured | [note] |
Projectile mass is measured. The counterweight is an estimate. Range was never recorded for this machine, so each cell reads "not yet measured".
Hindsight
What I'd change
- 01A longer slingI suspect a longer sling would add range, but without a measured release angle I cannot say how much. It is the first change I would test on the next machine.
- 02A stronger release hookThe eye hook and release pin do the job, but I would want more margin in that part. I think it carries some of the highest loads on the machine, and a bad release ends a throw early.
- 03A lower counterweight boxA box that hangs lower would, I think, be easier to load and steadier while it is being lifted. I have not tested that, so read it as a preference and not a result.
- 04Better wheel brakesThe wheels let the machine roll forward on release, which is the point, but holding it still while loading is awkward. In my opinion some kind of wheel brake would be safer while the arm is cocked.
Parts and materials
Parts and materials
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| Item | Spec | Qty | Where to buy |
|---|---|---|---|
| 2x6 lumber | Framing lumber, [length] | [qty] | Lumber yard |
| 2x4 lumber | Framing lumber, [length] | [qty] | Lumber yard |
| 3/4 in plywood deck | White deck panel, [size] | [qty] | Lumber yard |
| Steel pipe axle | Steel pipe, [diameter] by [length] | [qty] | Amazon |
| Pneumatic wheels and axle hardware | Wheels [size], hardware [size] | [qty] | Amazon |
| Eye hook and release pin | Eye hook and pin, [size] | [qty] | Amazon |
| Steel cable and thimbles | Steel cable [diameter], thimbles | [qty] | Amazon |
| Rope and sling cord | Rope for lashing, cord for sling, [length] | [qty] | Amazon |
Quantities and sizes are placeholders until the 2026 build is measured. Text links only.