Go Guzzi Go

By Alan Shipton

 

Question: What does 4340 and Titanium have in common!!

 Answer: Nothing at all apart from the fact that I have some in my shed at home.

 

Having decided that I would like a lightened flywheel and ring gear for the Mk4  I decided that I did not want to lighten the original in case I did not like it and wanted to put the stock item back in place.

            With that decision made and after asking a few questions on what may be the best steel to use I put my lathe to good use and turned up a blank flywheel out of 4340 alloy steel (also known as chrome moly). This was then normalized, (‘what the?’ I hear you say as often quoted by Rove) this is where the steel is heated above the upper critical range and cooled in still air at room temperature. This process is intended to put the steel into a uniform, unstressed condition of proper grain size and refinement.

 

   

 

      Rough Turning Blank                             Roughed Blank after Normalizing

 

The blank was then rough machined and finish machined, milled, drilled and internal gear cut to come up with the item below. The start weight of an original Mk4 flywheel and ring gear assembly is 5.5kgs as weighted on the other half’s trusty kitchen scales after a lot of machining I reduced the weight of the assembly to 4.2kgs (as measured on the scales) or a reduction in weight of 23.64%. However I feel I can reduce this even more but that’s another one-day job.

 

  

 

     Finishing Touches                                             Lightened Ring gear

The assembly was balanced and only required 10 grams to be removed to achieve 100% balance, which made me pretty happy. As you can see below it has all been assembled into the motor and so far I have been happy with my results. The motor spins up quicker on startup and seems too spin up a lot quicker (seat of the pants feeling) as well as making the gear changing smoother which has resulted in me having adjust my riding style, (what style I hear the critics cry out) somewhat.

        

 

            Would I do it again? Yes! I would remember, the Titanium I have in the shed (every man needs a shed is what I say) well if it’s the right grade for my  purposes just imagine how light I can go with a flywheel. If not it would make really neat brackets and top and bottom fork triple trees etc.

 

            However the next job on the agenda is two twin plug the heads, so until the next exciting development keep the rubber on the road where it belongs and the shiny side up!

 

Ciao for now Alan  

 

Oh and by the way I am still looking for that long lost relative too pop off!!