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Pumpkin Putter : 2001 Enhancements
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We built the Pumpkin Putter in 2000. After critical failure during last years 2000 punkin chunk we decided that the putter needed an upgrade for the 2001 punkin chunk. This page describes our upgrade path. Our longer term goal is to build Mista Ballista, using the putter as an interim machine.

Big problems included a weak trigger mechanism, run out on the fulcrum and jack shaft, too much wind resistance, and deadness while pedaling. The upgrade plan was to fix these items.

One of our big problems last year was too much runout. The connection between our fulcrum and the extension we welded was apparently not very straight. Using Dave's lathe, we made a new coupler that would keyway inside our fulcrum and jack shafts. This removed much of our runout.


Next, we had to broach a slot inside our fulcrum and jack shaft. This is done with a press, a broaching cutter, and a broaching arbor. In this picture, the press is labeled, the fulcrum is the silver shaft at the bottom. The arbor can be seen on top, with the cutter being pressed down into the shaft. Cohort Jeff then let us use his milling machine to cut a matching keyway into the coupler (above)

Once a slot is broached in the shaft, a key is then added to lock the keyways in the fulcrum and side coupler to make them spin together. This also allows us to adjust the chain location by sliding the plug in and out along the key.


After fixing those shafts, and updating the attachment of the jack shaft, we assembled the machine. Here is Dave attaching the fulcrum to the top of the machine.


The jack shaft is now housed in a metal frame which is bolted to the machine directly. Last Year the jack shaft was on a separate platform. When someone pedaled hard, the platform the bike was on would be lifted into the air, causing deadness in the pedaling stroke. This time everything will be clamped together, with bracing in line with all chain pulls. Unfortunately, the stands the bearings are on flexed outward, so that needed to be fixed.


Trevor decides he wants to help.


Eric welds additional braces to the back side of the jack shaft. This is to counteract the flexing of the bearing stands. Despite this, some small flex remains, but we decided that enough was enough.

Here I'm using a Craftsman gassless MIG. It's the smallest and least expensive MIG at Sears. It has several limitations, but I haven't broken a weld yet.


Kevin installs the upgraded Jack Shaft box into the machine. Unlike last year, the pedal chain ring will directly power the jack shaft. As such, the derailleur for the free wheel was moved and attached to the jack shaft box, and the shifter cable was extended.


Roger does run time modification to make room for the derailleur. When shifting to the large gears, it rubbed one edge of the bottom of the Jack Shaft box.


Roger attaches the arms to the fulcrum. You can see the stays are now attached part way up the arm. Half chain-links scavenged from Home Depot were welded onto the sides to do this. The stays were suspect of wind resistance last year, and pulling them closer to the fulcrum reduced that problem.


Roger adjusts our new trigger actuator near the fulcrum. Tuning the trigger to release the pumpkin for a proper 45 degree angle upward proved to be challenging.


Our new pumpkin pouch is truly a work of art and overreaching engineering enthusiasm. A basket ball was cut in half to provide a stiff shell to hold the pumpkin. A spring from an old stove was attached to the two angled cables which go toward the top of the image from the sides of the pouch. On top of the pouch, is a bar-lock using a similar technique to vice-grips. In this picture, a bit of pink nylon line is tied to the bar-lock central hinge. Pulling this line cause the bar-lock to open, and allowed the spring to pull the pouch completely open with great rapidity. This pouch was designed to overcome problems of the pumpkin getting tangled in the pouch which was a problem last year.


A pumpkin toss without the bicycle lands us a few feet in from the machine proving basic parts of the system were working. Later this night, the bicycle was hooked up and water jugs were thrown out to the center of the street.

See more of the putter in 2001 at the 2001 Butsi Hurl and the 2001 Punkin Chunk pages.


Video Clips

Here is a video of the the 'Putter in action.


Google Video Service
Pumpkin Putter 2001 Busti Chunk


Information:
Pumpkin Putter competing at the 2001 Busti Fire Chunk
1 min - Jun 26, 2006

The putter flings 70 ft. in Busti 2001
Video: MPEG
Size : 696324

Putter launches a pumpkin at Chunk 2001
Video: MPEG
Size : 727044

Close up of a putter launch at Chunk 2001
Video: MPEG
Size : 806916


Additional Pages for Pumpkin Putter
Pumpkin Putter In 2000 we decided to take a two prong attack to our siege craft. We simultaneously started building both a gigantic Ballista, and a centripetal human powered machine.
Pumpkin Putter: Construction In 2000 we decided to take a two prong attack to our siege craft. We simultaneously started building both the gigantic Mista Ballista, and a centripetal human powered machine. The centripetal machine was used in the 2000 punkin chunk and the ballista will be our long term machine.
Pumpkin Putter : 2001 Enhancements
(This Page)
We built the Pumpkin Putter in 2000. After critical failure during last years 2000 punkin chunk we decided that the putter needed an upgrade for the 2001 punkin chunk. This page describes our upgrade path. Our longer term goal is to build Mista Ballista, using the putter as an interim machine.
Pumpkin Putter : 2004 Enhancements In 2004, Team Tormentum got a call from Don Young of the "Junkyard Spinner" team with an interest in creating a "Human Powered Centripetal" division. Junkyard spinner was lonely since we had retired the 'putter in preference to Mista Ballista. There was a plan for a second spinning machine. All they needed was one more to make a new division at the World Championship Punkin Chunk. (Notice the picture on the lower right on the front page of that web site.)


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Last Modified: 11/26/16