So I finally got my plastic "prototype" adapter plate back from the machine shop and was able to do a little bit of work on it today.
While,making an ea-ej adapter is common stuff,I am the first that I know of to experiment making it in HDPE rather than out of the more common steel or aluminum.
Anyway here is the plate after it got back from the machine shop.mostly anyway.I cut some of the excess material off,oveled out the top holes,and inserted a steel bushing before remembering to get the camera.
From there I inserted the steel bushings into all of the various oversize holes.
Inserting the bushings was actually a fairly time consuming process for a couple reasons. 1: the steel bushings I got where the closest inch bushings that I could find.The 8mm dowel pins fit just inside 7/16" OD bushings,and the 10mm dowel pins and bolts fit just inside 1/2" OD bushings,BUT I could only find the 1/2" bushings locally 3/4" in length.So the extra 1/4" had to be ground down.So I bored out one of the holes in my old steel adapter plate to use as a jig.It was pretty cool how much heat the much larger mass of the adapter plate soaked up from the steel bushings.I could grind the bushings down to where they were flush with the adapter plate,getting them red hot in places during the process,push them out and hold them in my hand just seconds afterwards.Although the steel adapter plate got hot enough after the last bushing that it was too hot to hold..
The 2nd issue was just how SOFT the HDPE is.I beveled the leading edge of the bushing so it would go in easier,but I had to be very gentle in pushing the bushings in because just like in drilling it, the HDPE offered no resistance to sideways motion of the bushings.All of the bushing were put in by hand using my fingers because any more pressure would cause them to go sideways.Its really surreal to push steel bushings in and have the plastic deform out of the way just using the pressure between thumbs/fingers.Maybe HDPE isnt such a good idea..
the 3rd issue comes from the fact that I am using standard bushings on metric dowels/studs.They are close but all of the bushings needed some gentle dremeling for easier installation.One of the studs on the engine had a deep burr on it,and where the steel deformed upwards was enough to jam up and stop the adapter plate from sliding on so it had to be dremmeled smooth again.
Finally here is the pudding,the black HDPE adapter plate on the engine,with all holes lining up.
then I started to make the siamesed studs but didn't get very far.I figured out the length to make each sides of the studs but I didnt have any nuts to hold the bolts in the vise without damaging the threads so I went to the store and it closed just a few minutes before I got there,so I figured that was a decent stopping point.next up will be the siamezed studs and cutting out the rest of the adapter plate.
*NOTE: the extra hole seen at the top of the plate in the various pics is one of 3 extra holes the machine shop used to figure out the best way to drill the correct holes...
I'm really hoping this plate holes up because it is incredibly lightweight and easy to work with.It cuts like frozen butter and requires nothing but woodworking tools to cut/drill/mill etc.I would say its easier to work with than wood because it is dimensionally stable,and it doesn't chip at the edges of a cut like wood does. However,despite my optimism for it,it might just end up failing like a few of my other ideas,but only time will tell.