RE: How do you identify a genuine Mills P-75 Diesel?
Dan other than the front end its the real deal. As I guessed earlier the prop driver and spinner nut are not kosher. The prop driver resembles the 1.3 one, with a centre spigot. Since it is likely to have a taper fit, this almost certainly implies that the crankshaft has a matching taper as well-which means the shaft is not original. This is not too surprising as Mills shafts are realtively easily broken in a crash-and invariably they snap off at the strees raiser caused by the two flats where the prop driver fits-leaving about 1/8" projecting from the case-if you're unlucky you lose the entire front end in the grass as well [been there, done that with a Doonside!] So it is quite likely that a previous owner had a shaft made up-and used perhaps some spare 1.3 bits to complete the job. Attached are some photos of an original Mills 75-note the spinner is non original-note the webs in the backplate, the small tabs retaining the tank, the sharp edges to the mounting lugs, and the prop driver. Now another pic with a group of Mills 75s:clockwise from top left: original english Mills(with correct spinner nut this time!), Irvine Mills (you can just make out the serial number stamped on the edge of the RH mounting lug-note also different prop driver and small 'acorn' type spinner), early (mid 80's) Indian Mills-note rounded head profile and more sharply tapered tank [this one should have a hex spinner nut but they strip easily!], Boddington Mills (made by CS)-quite different to all the rest, Russian made ABC Doonside Mills-high quality surface finish, webbed bearing housing,thicker, more parallel fin profile-thick alumium prop driver, and finally lower left an original Australian made Doonside Mills Mk2 -webbed crankcase, coloured head
Next some bits-top left an original Mills 75 prop driver (steel) and spinner-note the 'flattened circle' centre hole, next two complete carb assemblies-the first is a Doonside one-the steel circlip retaining the tank is just visible as a dark line inside the tank top, on the right an Irvine carb assembly-note the blacked needle, and beside that the rarely encountered long range tank which screws into the carb as a direct replacement for the smaller standard tank, if required, for longer run times in R/C models. Below this a broken 1.3 crankshaft-note the taper for the prop driver fitting
Finally, a shot of a 1.3 and 75 crankshaft-in particular note there is no taper on the 75 shaft, and one of the two milled flats for the prop driver seating is clearly visible.
A couple of other points: Indian Mills were manufactured using the original english tooling, jigs and fixtures from Mills Bros-so parts are interchangeable. The Australian made Doonsides were made by averaging measurements from a number of originals-there was a lot of variation in the originals. Parts may or may not be interchangeable-it will be pure luck if they do. Irvines were made to resemble the Mills 75 externally, but are quite different internally-NO parts are interchangeable with originals. The Russian Mills are probably metricated, but some parts may interchange with the Australian Doonsides. The Boddo Mk1 is unique. The Boddo Mk2 looks more like a Mills-but as it is made by CS is probably produced to metric dimensions.
ChrisM
'ffkiwi'