“The lump” – Engineering Prototype Preliminary Evaluation



In the fall of 1997 I got my first GPS receiver, an Eagle Lorance, for around $130 which was well within my toy budget and became hooked.  I soon realized that it was an ideal accessory for off-road use on my Kawasaki KLX300  while exploring trails and riding dual sport events.  Shown is a picture of my KLX at a ride last year in GA.  Note the Garmin III in the homemade handle bar mount.


With the acquisition of a ’96 BMX GS R1100  in the spring of 2000. For this bike my homemade kludge simply would not do.   So a Touratech mount was purchased – fine German craftsmanship to match the bike.  In fact the mount looks like a very expensive prototype made in a fully equipped model shop so at $89 I consider it a bargain.



After using a GPS receiver for a number of years several problems became apparent:


  1. No matter what the literature says the battery life is finite and the batteries will be exhausted when you are running on fumes, lost in the woods and really do need to find the quickest route to a gas station.
  2. The vibration on a typical off-road bike will trash the contacts on the AA cells in less than an hour of riding.
  3. When you lose power to a GPS receiver for any reason it must restart and reacquire the satellites and come up with a position solution before you can get a map display.  If you are moving at the time another dimension is added to the problem and you may never get a position till you stop and have good satellite visibility.  



To address the problems noted above it is apparent that an accessory power module was needed that had the following features:


  1. Use the ORV's available electrical power.  This falls into two categories; vehicles with a 12 VDC system with an on board battery and those with a lighting coil only and no 12 VDC batteries.
  2. Provide a separate battery backup.  The internal AA batteries for example, would normally provide the battery backup, in the Garmin GPS III.  However, due to the vibration problem noted in (2) these should be removed when using in a high vibration situation such as an off-road bike.  For vehicle with a battery system the auxiliary  power could come from here except that it is more difficult to wire up and when cranking the engine the voltage will drop below the 9V threshold and the GPS will reset. (See item 3, above)
  3. Provide a connection to the GPS unit without having to also buy a rather expensive proprietary power cable.  These cable cost $20 or more if you want access to the serial data lines.
  4. Rugged, vibration immune, and easy to install.  Basically any vehicle with a head light can be easily hooked up to the Lump™ by connecting two wire to the headlight wires using automotive style crimp connectors.  No need to worry about polarity.


After studying a number of different power source options it was decided that perhaps simplest was best.  Two basic design architectures were considered:


  • Single Cell
  • Multi Cell


Initial investigations into a single cell system showed that the voltage multiplier circuitry would be two expensive and inefficient to justify the lower cost of the Nicad cells.  Therefore it a multi-cell system was selected. 


For the Garmin III eight to ten cells are needed.  Prototype 1 uses 10 cells and the planned prototype 2 will use eight cells.  The 10 cell model gives about 70 minutes of battery backup when fully charged.  The eight cell model will obviously be provide less backup time but will have the advantage of smaller size and lower cost.


The pictures below show Lump1 installed on my KLX300.  Note that the view is looking straight down with the headlight assembly’s upper restraint removed and folded forward.  The Lump consists of a cutoff Garmin power connector to a heat shrink package that houses the welded Nicad cells, bridge rectifier, zener and series resistor.  The ends of the package are folded over to provide some “spring” tension so that the tie wraps don’t become loose.  


The blue crimp go to the headlight wires but in this case I already had a power module in place so I connected to those wires which go to the headlight connection.



Line Callout 2: TouraTech mount Line Callout 2: The Lump Line Callout 2: Garmin GPS III+ Line Callout 2: Automotive style crimp connectors Line Callout 2: Old power supply and cable



View from the Pilot’s seat: