Goodhead News

New heads. Posted on 30 Mar 14:38 , 0 comments

Goodhead 3.0

A beefier model that maintains the scooping power of the lighter-weight second generation heads. Maximum diameter allowed, 2.559", and better longevity at the cost of only 10 grams more plastic than the previous batch of Goodheads. (Which are still good -- super light, just not quite as strong as these ones.)

Three lengths, collect them all: 5" (approx. 93g), 4.5" (approx. 87g) and 4.25" (approx. 84g).

Lyer, lyer. Posted on 11 Jan 14:54 , 1 comment

If someone tells you an aluminium seat post is forever stuck in a steel frame, that person is wrong. Pipe up and say "Lye!"


Lye, also known as caustic soda, is a common name for sodium hydroxide, a chemical compound that people use to use to make soap, tan hides and cure foods. Mixed with water, it dissolves some types of organic material -- drain clearing products contain a lot of sodium hydroxide.

It also dissolves aluminium, while having no adverse effect on steel. That seized post is as good as gone. 

You can watch video of parts of the process here.

My awesome new polo bike

I acquired an early-model Fleet Velo Joust from a friend who had switched to a 700 frame. The seized post wasn't his fault. He bought it, already seized at the right height, from someone else. He's the one who told me about the possible use of lye to get the seat post out. I figured it would be fun to try, and started bugging him to sell the frame to me. 

I got the lye I needed from my soap-making friend Sarah at Flatlanders Soap Co. (Her felted soaps are especially awesome -- go buy some.) I needed about 800g (27 oz) in all. For your own lye, check for local soap-making supply shops. I've also read about success using drain cleaners. I tried a liquid drain cleaner at first, but not much happened. If you can get straight sodium hydroxide, get it. It comes as pellets, powder or flakes.

Hydrogen gas means it's working

You want to fill the seat tube with the lye/water solution, with no leaks. I wrapped inner tube over and around the top of the seat post, and used a pipe clamp to seal it. Then, so I could fill it from the bottom bracket, I set the frame upside down in the top of a steel barrel, just in case it leaked. It did leak a few times. You could probably use a big garbage bucket; lye doesn't seem to have an effect on plastic or rubber.

I mixed the lye (about 200 g or 7 oz) and water (about 500 ml or 1 pint) in a glass jar and stirred it gently with a screwdriver, before transferring it to a plastic squeeze bottle. (nb: Water first, then add the lye.) I used the squeeze bottle and two short lengths of narrow plastic tubing to get the lye into the seat tube via a small hole in the bottom bracket. It took not quite 250 ml (half pint) to fill the seat tube.

After a few minutes I heard bubbling. After a few more, the seat tube started giving off hydrogen infused smoke -- lots of it. Tipping the frame now and then seemed to invigorate the process when it slowed down. If you do this, take care moving the frame around -- the chemical reaction going on is "exothermic" and the frame is going to get almost too hot to hold.

After about 90 minutes, I removed the pipe clamp to drain the frame and apply fresh lye water. A dark and thick sludge came out, a mixture of water, lye and what used to be aluminium.

The whole job took eight applications of lye water, bubbling for about an hour each time, over four sessions. Say nine hours in all with refills. During the final round, I tipped the frame to mix up the lye inside when I head a faint "clunk" noise.

Quickly, I unclamped the stop and gave the frame a shake. Half of an aluminium seat post slid out, slowly, on a bed of sludge. The other half came loose with a nudge from a screwdriver. 

The sludge did make its way into the downtube and top tube, so I gave the frame a thorough rinse with a handheld shower head. A day later, a dusty white residue remained. I wiped it off with a damp cloth and admired my work.

A few cautionary notes:

- "Caustic" means don't get it on you. Lye can cause chemical burns. Maybe not as bad as Fight Club might make you think, but be safe anyway. Wear safety glasses and rubber gloves (elbow-length industrial if you can get them, though the Princess brand I got from a dollar store worked fine.) 

- Do the work outside or in well-ventilated area -- the smoke coming off includes flammable hydrogen gas.

- Always add lye to the water; never add water to the lye. Pouring water on lye can cause the reaction to be "explosive" according to various things I read and heard.


It definitely works. How? I don't know. Chemical magic. I took the following from a forum discussion. I can't follow the chemical notion, but as I understand it the lye basically makes aluminum eat itself, forcing it to continually produce aluminium oxide. Here it is:

Under normal circumstances, aluminum does not react with water, as an impermeable protective layer composed of aluminum hydroxide either forms within seconds or is already in place. With the addition of sodium hydroxide, the formation of a protective layer is prevented. With the production of aluminates [ Al(OH)4 ]-, the amphoteric (capable of acting as either an acid or a base) aluminum hydroxide Al(OH)3 goes in solution:

2 Al + 6 H2O --> 2 Al(OH)3 + 3 H2

Al(OH)3 + NaOH --> Na+ + [ Al(OH)4 ]-

A layer of aluminum oxide previously formed by passive corrosion is dissolved by the addition of sodium hydroxide. For this reason, the reaction takes place at the beginning relatively slowly:

Al2O3 + 2 NaOH + 3 H2O --> 2 Na+ + 2 [ Al(OH)4 ]-

The aluminum completely dissolves and the water acts here too as an acid.

So that's what happens, I guess. I know that it got hot -- almost too hot to touch while moving the frame at one point. If you're interested in more chemical notation of the process, or a demonstration of aluminium foil dissolving in lye:


The Goodhead manufacturing process Posted on 24 Apr 23:42 , 0 comments

Making a Goodhead starts with rods of 2.5” ultra-high molecular weight polyethylene (UHMWPE), ten feet long.

Step one cuts the rod on the band saw into pieces that are a little bit longer (0.2”) than finished heads will end up as. The saw leaves marks on the heads, and isn’t reliable enough to count on precise cuts; a CNC lathe will ‘face’ the pieces to make them exactly 5, 4.5 or 4 inches long.

Step two moves the will-be heads to said lathe for facing, along with ‘turning’ to get the pieces of rod to the right diameter. (When you buy 2.5” UHMW, it comes in pieces that are 2.6” thick.) This step has two steps -- I face and turn one end, then the lathe program pauses so I can flip the part to face and turn the other end. If you get one, you can look and see where the two passes overlap.


Step three drills out a big portion from the middle of the rod. Capped heads get drilled through most of the way to come out like cups. Open-ended heads get drilled right through and come out as tubes.


In step four the lathe bores out the contours of interior diameter, in three incrementally smaller passes. This step makes the awesome scooping chamfer and the internal ribs that give the heads their resilience. The open-ended heads get flipped for a subsequent pass to round off the heavy edge on the shooting end.


In step five, the lathe drills shaft holes and bolt holes into the heads.


Step six, on a plain old drill press, puts a chamfer (an angled edge) on the bolt holes. This way, the bolt displaces less plastic as you tighten it, for less warping in the head’s shape.

Who doesn't like Goodhead? Posted on 31 Jan 23:46 , 0 comments

About a year-and-a-half ago, I was working in a machine shop and becoming very fond of hardcourt bike polo.

The two things had nothing to do with each other until it occurred to me that I could make my own mallet heads on the CNC lathes at work. So I made some, about 15, with sub-standard but pretty inexpensive HDPE. I traded them for ski poles and six packs, and sometimes a ten dollar bill. They wore quickly on the uneven surface and cracks of our local court.

The second small run I made from UHMW polyethylene. Local players appreciated them much more, and the heads came just in time to quell complaints about the first run. Another 20 ended up being used, including by a few out-of-towners who came to Winnipeg for one of the excellent tournaments hosted by the Winnipeg Urban Polo Association (WUPAss). 

That was enough interest to warrant a third run, about 80 in all. Of those, I managed to sell a few dozen to a local bike shop that set up a polo section. The shop is called Natural Cycle -- great bike shop. And I sold a bunch more to more out-of-towners.

With the heads that were left as the start of an inventory, and drunk with the idea of being an exporting manufacturer who gives people good mallet heads, I decided on a fourth run and that brings us here. 

Please buy all the heads I have. More plastic is on the way. If you buy one, please tell me how to make it better.