Instrumented Rowing Machine Handle

This handle was born from a desire to measure the force applied to a rowing machine. This effort reached only a prototype stage, and never a production design. My direction was to make a cost-effective prototype as quickly as possible.

Foundation For speed and cost reasons, I chose an aluminum tube and u-bolt from McMaster-Carr as the foundation for this prototype. For the four holes to accomodate the U-Bolt, I decided calipers and marking fluid would provide adequate hole location precision for the two holes which I drilled with a drill press. 

I drilled and tapped two smaller hole in the top of the pipe, to screw on a small plate with more holes I tapped to accomodate a small PCB my EE teammate designed, and a battery holder I specced for the battery my EE teammate required.

Load Cell Coupling For the coupling between the aluminum pipe and the units’ load cell, I decided more cost was necessary to prevent off-axis loading on the load cell from affecting measurments. 

I designed a two-part swivelling coupler comprised of:
 1.  An aluminum coupler designed for turning on a lathe, with one post-process milling  operation. This part includes:

  -- 3/8 - 24 tapped hole for the LCM-200 500 lb load cell used in this design (existing company property)

  -- Flange for retention of a brass bushing

  -- Thru-hole for pass through of U ring



 2. A bushing CNC machined from SAE 660 Bearing Bronze
This bushing requires a complex milling operation to form the sliding interface for the OTS U-fitting
                                               


Other Fittings / Interfaces For cost and speed reasons, I replaced my initial 3D printed grip concept with bicycle handlebar tape. 

For strength and longevity reasons I ordered an aluminum bracket to be CNC machined locally, and used a simple bolt and unthreaded spacer to retain hydrow’s webbing (as shown at right)



Outcome After receiving the prototype parts, I assembled the handle, added a custom board from our electrical designer, and passed it to our firmware engineer for programming.  

Management initially planned further development after this prototype, but chose to shut the project down to allocate our time to a different project.