Giant DH Comp Electric Bike 2011 Favorite

Nov 29, 2011

Stock Giant DH Comp

This has to be my favorite conversion of 2011.

A 2005 Giant DH Comp, custom drop out adapters, 2808, 48v LifePo4, front fork rack.

The Giant DH comp is a popular platform for electric offroad conversions, some what strange as it is not a simple conversion. The bikes are a great off road bike that can be purchased from $600 second hand and are generally populated with good components and powerful brakes. The pre 2005 models have a straight top tube providing a large frame triangle for fitting batteries, where the newer models have a bent top bar making the space in the frame to small for batteries.
The first big challenge is to create adapters to fit the rear motor. This bike has a 12mm push through rear axle, typical of motorcycles. This means a normal electric hub motor can not be fitted. Some people chop off the rear drop out area and weld, glue, bolt in place a new vertical drop outs.

Well I was quite sure there was a way we could make a drop out with out cutting and spoiling the original frame.
So I set to work in cad, obtaining and modeling the various parts needed to design the adapters.

Eventually happy with the design I created the cut files and sent them to the laser cutter to be cut from stainless steel.

I hand machined the bosses that fit to the axle holes and tig welded the parts together.
Finally I had the parts acid etched to even the colour after welding and make a tidy appearance.

The adapters worked very well, and have since made sets for people around the world to convert their bikes.

Next was the mounting of the battery and controller. Here I used a front rack I also designed which supports the battery and mounts the controller. The LifePo4 battery is housed in a battery bag and strapped in place.

Full twist throttle, 3 speed switch, regen braking button and cycle analyst computer were installed, cables cut to length and connections water proofed.  Controller current limits are programed, cycle computer callibrated and we are ready to go.

The bike has a top powered speed of around 43km/h. I took the chance to ride the bike through the Akatarawa forest before handing over to the new owner, always a good way to test the system for any irregularities. With some pedal contribution from me we climbed most hills at around 17km/h, and cruised the logging roads at 35-40km/h.

I came back down via a single track which the bike handled well, and its an added thrill to be able to accelerate out of corners and maintain down hill speeds on the uphill sections.

I liked this bike so much, I bought one for my self which I will convert over Christmas trailing the new crystalyte motors and controllers.

 

Now I have the motor adapters, I can recommend this bike if you are looking for a great off road platform to convert.