Ever since Bruce Hodges (aka "bruce2000ltc") introduced his brilliant idea of motorizing the Bak-Up backrest adjuster in spring 2007 I had it on my farkle list. Check this: http://www.bmwlt.com/forums/showthread.php?postid=161005#poststop The general principle of the mod is described so well by Bruce that I will not repeat every detail.
I had hard time finding just the right kind of a small battery powererd screwdriver so Tony K. (aka "deputy5211") helped me out and he sent me one. Here I have already taken the unit apart and used some epoxy glue to glue the gearbox halves together.
It was a very tight fit so I had to grind one side of the gearbox flat.
I used fiberglas putty to make a "nest" for the motor. I covered the motor first with masking tape. Then I applied the putty in the backrest support and pressed the motor in the soft putty. After the putty had hardened partly I trimmed off the extra and removed the masking tape from the motor so it did not get messed up with the putty.
In this picture I still had the hose clamp which I was going to use to fasten the motor/gearbox in the backrest support but it was a bad idea. The hose clamp squeezes the plastic gearbox housing too hard and the result was that my epoxy glue that holds the gearbox halves together cracked.
Using zip ties is the right solution. They hold the motor tight enough without breaking it.
Shrink tube protects the electric motor.
Just like Bruce did, I also cut the other side off of the return spring. This relieves the load of the motor.
Here is the 3,6 V battery pack. At first I tried to create a voltage regulator that would drop the voltage from 12 V to 3,6 V but then I decided to use the battery pack and charge it when needed from the bike.
For charging I used a Nokia cell phone charger. This charger gets power from a relay that is commanded by one of my numerous switches on the dash.
Commanding the motor to run to two directions was done with a help of two 12V dual pole relays. The relays are all connected and taped together in the left. On top you can see the what kind of relays I used.
There was plenty of empty space in the bike's main electronic box (under the gas tank). So I installed my Nokia charger and the 3,6 V battery pack in there.
The ex-radio control button commands the backrest front / aft adjustment and also my seat up / down.
I had to have a bit larger cover made for the backrest support so that the motor fits nicely inside.
