Corbin's Treehouse - Corbin Dunn, Santa Cruz, CA
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Archive for 2009

Madagascar: HDR Town

HDR Town, Madagascar


A cool picture, in that it looks like a mini-model.

f/22, Canon digital Rebal, ISO 200, 3 shots HDR, 17.0mm

Adjustable Unicycle Handlebar

I was never happy with the last handlebar I made for my KH36 road unicycle. It attached underneath the base of my seat, and despite it being carbon fiber it still flexed quite a bit and I was afraid it would break. It also never felt quite right — I wanted it to be slightly lower, and slightly more forward. On my KH24 geared muni I have a handlebar that attaches to the seat post and has always felt great. Using the seat post wouldn’t work for my KH36, since I’m short and run the seat all the way as low as it can go when using 150mm cranks. In fact, I think I cut down the top tube on the KH36 frame a bit so I could get it extra low.

To work around this problem I made a new version that attaches to the frame and adjusts vertically when I use different cranks.

Here is a picture of the completed setup:


The individual pieces I made mainly from 22.2mm tubes (purchased from Aircraft Spruce) brazed together. The small piece at the bottom is an adapter to attach the brake in the direction that I like. I make the little seat post clamps on my lathe, and trim some fat off of them with the milling machine.


The base attaches to the frame:


The top T goes in, and can be adjusted up and down. I could also replace it if it ever breaks or doesn’t work the way I want.


After the brake is installed:


Top view. Notice that I run a set of bar ends backwards. I use these when riding rough terrain, or for climbing steep hills. I really prefer it to the typical front plastic handle found on nearly ever unicycle.


After I finished making it, I painted it with 2 coats of gray primer, 2 coats of black, and 2 clear coats.

Riding with it is a dream — it is exactly the handlebar I want. In theory I could also use this setup like a “V frame” unicycle, by tilting the seat forwards a lot and dropping the front handlebar post down all the way, but I haven’t tried that yet.

Tandem Unicycle Video

Here is a short video of me (in the back) riding the tandem unicycle with Jason. This was our third try. Click to download the little iPhone 3g movie.

Screen shot 2009-12-14 at 7.05.57 AM.png

You tube version: Tandem Uni on YouTube

With practice, I’m sure we’ll be able to ride it. Louise and I also tried, but only for a short bit. We were going to work on riding it this past weekend, but she had to go to Shasta for a family emergency.

EDIT: For all the traffic visiting, I recommend watching the Africa Unicycle Video. It is much better!

Building a Tandem Unicycle

My last post introducing my Tandem Unicycle originally started out with a step-by-step process of how I built it, but for some reason I lost the post. Here is how I made my tandem uni:


This idea is not my original idea. A few years ago at a “California Mountain Unicycle Weekend” a guy named LobbyBobster on the unicycle forums brought one and I gave it a try with Beau Hoover. Here’s a picture of the creator and their tandem, which looks much nicer than mine!

tandem unicycle P4060001.jpg

So, from seeing this uni two years ago and based loosely on this picture I set about making my own for no cost. I already had two old bikes that I got for free, so I was set to begin.

* 2 Huffy Mountain Bikes

* 2 Unicycle Seats

Tools Used:
* Sawzall (with a bimetal blade)

* 4.5” angle grinder

* MIG welder

* Half round file

I took the wheels off of the old Huffy mountain bikes. One of the two rear wheels was going to become the main unicycle wheel, so I removed the rear cassette and saved the sprockets:


The intent was to weld the two rear halves of the bikes together, utilizing the rear triangle that already exists. I used the sawzall to cut the front half of the bike off:

(NOTE: in this picture I already had removed the seat post clamp for another project — you should leave it on if you are making your own tandem).

The rear triangle after I cut it free. Notice that the seat post tube is at an angle — I later cut it off and re-welded it vertical so it would be more “unicycle like”:


And the rear triangle of the other huffy after I cut it free:


I removed the main drive hub — one of the two has to be switched to the opposite side, and it worked well to remove both and re-grease everything after I welded it back together. Removing the hub was easy, even though I didn’t have the proper tool. I used a screw driver to get the reverse-threaded hub “bolt” out:



The next thing done was to cut off the vertical tube and cleanup the two holes left in the hub housing:


I then needed to weld the seat post tube vertical. I used a half-round file to cut a slight fish mouth out of the tube so it would fit nicely over the rounded hub housing. I then created a hokey setup to hold it vertical, testing the straightness with a square:


I tacked it, and welded it on. Note that the big holes are left:


I cut a piece out of one of the horizontal seat post tubes to use as a patch:


I tacked it on:


and then completed the weld. There is a patch on each side to cover up both holes. I then repeated the process for the other bike half. At this point I attached the two halves to the wheel to get a feel for it, and cut a top tube to size after making sure the bottom pieces were inline with each other:


The next thing I needed to do was to weld the two halves together. I prepped the steel and cut off the angled slot on one side:


I clamped them together, making sure the bottom pieces were in the same line with each other — that way, each seat post tube is parallel with the other.


After they were MIG welded together:


At this point I decided to weld the freewheel on the rear hub’s cassette so it wouldn’t freewheel. Note that the hub spindle still turns free.


The next part was to tack weld in the top tube in place, and cut some side tubes to fill in the frame:


For the other side doesn’t look as good. It turns out the two bikes were different frame sizes, and I wanted the top tube to be horizontal, so I had to do some funkiness to get it that way:


At this point I put the sprocket and hubs back together and stuck some unicycle seats in:


The only thing left was to weld on two sprockets in the wheel’s hub. I took two sprockets of the same size (one from each cassette), with about the same number of teeth as the smaller hub sprocket (in order to get a 1-1 gear ratio). I made a spacer by grinding off some of the teeth on one of the sprockets and used some of the plastic spacers that were left.


I then welded this to the hub (sorry, no picture).

At this point, the whole thing was put together with two chains, and I temporarily used a large sprocket in between two of the chains to keep the chain a little tighter:


Left todo is to create a chain tensioner, and to paint the thing.


Tandem Unicycle

The Tandem Unicycle Project


EDIT: Here are the tandem unicycle construction details for the makers out there.

EDIT: A short video of me and Jason trying to ride it: riding the tandem uni.

EDIT: For all the traffic visiting, I recommend watching the Africa Unicycle Video. It is much better!

Madagascar: Chameleons at Night

Chameleons at Night


While in Madagascar Louise and I did two guided night walks. It was quite amazing, as you could shine the flashlight in the trees and chameleons would show up bright white. They varied in size, and this one was tiny (think pinky size). It was difficult to photograph them; the first night it was raining and I didn’t bring the camera, and the second night we didn’t see any close enough to get good shots. This shot turned out “okay”, but not great.

Madagascar: KH24 on Isle Saint Marie


While in Madagascar Louise and I did a short ride from Isle of Nattes to Isle Saint Marie and up the road a bit. The picture needs to be cropped slightly; you can see the power lines in the top right of the image.

Zanzibar: Monkey Looking

Monkey Looking


The red colubus monkey in Jozani Forest, Zanzibar off the east coast of Africa.


Darn cute monkeys!

Madagascar: Ring Tailed Lemur in Tree

Ring Tailed Lemur in Tree


HDR from three exposures. Taken on 7/29/09 12:00pm. ISO 100, f/6.3, 100mm.

Louise and I were treated to seeing a TON of lemurs in Isalo Park, Madagascar. This guy was sitting up in a tree and holding still enough for me to capture three shots and create a subtle HDR. The non-HDR version doesn’t look as vibrant as this one.

Madgascar Natural Pool

This was a great little oasis at Isalo Park in Madagascar. The area was called “Piscine Natural”.


HDR from three exposures. f/22, ISO 100

(c) 2008-2017 Corbin Dunn

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