A sprocket, is a sprocket, is a ...?

How nice is the Tree home page?
Maybe it's just my inner hippy speaking, but I really like it.

They don't make everything at Tree, but the stuff that they do make, they make really well.
I've pretty much always had a tree sprocket.

The original ones were perfect. When they first came out with them everyone else was making sprockets out of 6061 t6 aluminium, which is pretty soft really. Tree had an ingenious idea to make a sprocket that didn't just bend, break or wear out. Now how the hell did they come up with that?

So they ended up using 7075 t6 aluminium which according to them is "84% stronger than 6061 t6 and 51% stronger than 6013 t6." They really are hard, they're 5/16" thick - and they pretty much last forever. I've had mine 4 years and it's got plenty left in it.

This is from their website about testing the sprocket. Pretty funny:
We tested the 7075 sprockets by doing repeated air to sprocket bashes on a coping to coping spine while using a motorcycle chain so we didn’t have to keep replacing links. First I tried it with a Tree 7075 sprocket and then I tried it with the common 6061 sprocket. I would slam the sprocket into the coping as hard as I could to try to bend it. When I tested the 6061 sprocket the teeth were smashed in and miss-shaped after 5 hits. With the Tree sprocket I slammed it as hard as I could with the same force of hits in excess of 25 times. It did not bend and the teeth had scratches on the side of them along with the tooth valleys being pushed in just a little bit!!
Such a simple innovation, but one that was so obviously better than what else was around that now pretty much everyone makes 7075 sprockets.

So you'd think that's it. Sprockets = Done.

Choose one that's 7075, choose one that's CNC'd, choose your favourite brand, choose from one of the hundreds of designs that are only slight variants of one another. A sprocket is a sprocket is a sprocket.

You just wouldn't think that someone would go and try to reinvent that (chain) wheel.
But Tree did, and they came up with this:
For something so simple, it's tech as hell. It kind of takes sprockets too far - in a good way.
Each of the spokes uses an I-beam section to achieve maximum strength to weight ratio. So you end up with a 25 tooth weighing just 61 grams or 2.2 oz.

From the Tree site:
I designed this sprocket from the idea of the structure of the bike wheel has a hub, spokes, and a rim. I used our 3D drawing program where we can actually test the sprocket strength on the computer. This allows us to make a very high tech sprocket with a tremendously high strength to weight ratio.

We have designed the spokes of this sprocket to be tapered and I-beam shaped. This makes the best use of the material used to form the bridgework of the sprocket. Every single detail has been thoroughly thought out. Many all nighters have put into designing this thing.
I love it! There is no way that anyone has ever put so much effort into designing a bmx sprocket!
I'd bet that no else even bothers to do the breaking strain analysis that they talk about, let alone do an all nighter for a sprocket.

I don't know if I'll be swapping over to the splined version, but I do like the idea of having two plain crank arms with no crank bolt or boss on your drive side crank arm. It'd just add a nice simple detail to your bike - and it'll drop an oz or two and that's bound to be popular.

If you're interested, Profile are selling crank sets specifically for the Tree splined sprocket. Basically they are just putting two non-drive side cranks in the box instead of a regular set - nice and simple.


Clod said...

two non-drive side cranks?

that's what I thought at first. But this is what Christian Henrich of Profile had to say about them..

« We never really made many right hand crank arms with no boss on them in the past. 99.9% of the LHD cranksets we ever made came with cranks with bosses on both arms.»

These cranks are especially made for the splined sprocket design.

digahole said...

yeah you're right... or he's right. you're both right, more specifically - i'm wrong.
different pedal threads on the left and right sides. either way a clean set up.

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