Junkyard Dog project update

So it was a pretty shit back half of 2022, with arsehole generational Italian orchardist neighbours making life pretty fukn miserable to the point my good lady was too scared to leave the house. I was pretty keen to investigate the ring-tone a shovel bouncing off their heads would make, but working away from home and leaving my better half exposed meant sucking it up (hardest thing I've ever had to do) while going through the motions of selling up and moving on.

Apologies, it's a roundabout way of saying my dedicated bike shed is gone-burger and I'm now working out of a 2 car garage, with 2 cars, with a lil' strip of Ducati-land at one end. Such is life, I still I have a (well worn) path to the beer 'fridge so it's all good compared to many.

But while activities are somewhat restricted, and the jobs related to a new (to us) house/property are never ending, every now and then I sneak off for a bit of bike 'n beer time and potter away on the 749R/999RS junkyard dog project.

I haven't made any progress on that exhaust/swingarm issue (discussed/whinged/whined about here)....actually, now that I think about about it I have been sneaking up on having a crack at it with some other lil' welding projects, they aren't in the same league of importance but baby steps and all that.

The bike was sort of thrown back together just for ease of transport during the move. A point to note for anybody else doing the same: getting a bike, even a relatively light one, off a trailer is not quite as simple as it sounds when you have no effective brakes....just sayin': don't be me, ask for assistance, it'll save your pooper valve no end of strain.

Firstly, I have to now admit to becoming a member of EAA: Ergal Addicts Anonymous. Ergal? Otherwise known as 7075-T6 aluminium.

Compared to common old 6061, 7075-T6 is made by adding a touch more zinc and a smidge of magnesium, so far so boring, its properties aren't hugely altered. But the magic happens when 7075 is tempered (the T6 tacked on the end) during the alloying process.

It turns out "homogenizing the cast 7075 at 450 °C for several hours, quenching, and then ageing at 120 °C for 24 hours creates an alloy that is 1/3 the weight of steel yet is stronger than some of the steel alloys."

Hmmm, I'm sensing some bullshitometers going nuts right about now, but check this out:


This all came about with the purchase of a Corse 999RS Ergal swingarm pivot shaft:



Which lead down a rabbit hole of investigating the properties of Ergal/7075-T6.

Obviously there are a heap of different properties involved between steel, titanium and aluminium but you have to ask yourself what is the point of using an expensive uber-tough Ti bolt given the weakness of the cast aluminium it might be threaded into? Or the carbon fibre it might be securing? Wouldn't something as strong as steel , but 1/3 the weight be a more appropriate choice? I mean not only is it half the weight of Ti but it is a fraction of the cost and infinitely easier to machine.

But it's horses for courses: Ergal has an Ultimate Tensile Strength equivalent to steel but it does have a significantly lower Yield Point (the point at which it is permanently deformed). But then Ti is quite brittle so applications subject to flexing are prone to breakage. Ti is also very "notch sensitive", where a small surface imperfection propogates to a major failure. Both of which explain why Titanium axles are verboten by most racing governing bodies.

Plenty to ponder!

So my sexy new pivot shaft was affordable because it didn't have the appropriate bolt. I could use the OEM steel bolt, but that just seemed like putting Eva Mendes' lipstick on crooked. I actually looked for a flanged Ti bolt, in vain thanks to the unusual 1.25pitch of the M15 thread, but after my proselytizing above I kinda felt I had to walk the talk and make an Ergal equivalent. Pretty sure the Corse bolt is Ti, but then it's being removed/replaced (70Nm) half a dozen times a weekend, something I have no need to do.

I don't have a rotary or dividing table for my lil' mill so it was just marking-blue and careful marking out (not a strongpoint!), then waiting to see what emerged from the swarf. The machining gods must have been fresh back from the pub and in a good mood:



Corse pivot vs OEM:



Hmmm, in for a penny in for a pound (pun intended), I came across a very clever gent who had helped me out with parts in the past who was producing 999 rear axles in 7075-T6. How could I not?

And, if you included the 7075 wheel spacer not shown (I had to machine a custom unit for the Galespeed rear wheel fitment) it saves pretty much bang on 500gm in unsprung mass:



Realistically there aren't too many other ways of losing 0.5kg in 5 minutes that don't involve laxatives.

Next up, way back when dinosaurs still roamed the earth, I'd installed a CDR radiator/oil cooler set, basically an MB Motorsport replica as used by Larry Pegram on his AMA 749RS, except mine has a filler neck/cap installed. When the Pierobon DP fairing brace wouldn't allow fitment of the RS water tank I thought the filler was a genuine godsend, allowing me to simply not fit the water tank......but this was a complete honey trap: the filler neck/cap took up the exact space needed for the RH RS intake duct.

Seen here against an MB Motorsport radiator:


So just swap them out right? Nope. The CDR rad/cooler are a matched set, in both manufacturer and mounting arrangement, but looking closely you'll see the MB unit has slightly different oil cooler mounting tabs. I just happen to have a damaged-in-storage-but-still-serviceable MB Motorsport oil cooler....but it also has the CDR-style mounts (as I understand it 996/998/999/1*98 RS's all used the same radiator but the oil cooler and mounting arrangement variations seem deliberately designed to drive me to drink) Look even more closely and the top MB rad mounts are badly cracked, needing repair.

With a new welder sitting in the corner, albeit still a mystery, I could have blanked off the filler neck on the CDR unit but thought it might just be handy for something else down the track, so repairing/remounting the MB setup got the nod. The welding gods aren't half as kind as the machining gods but it's a solid enough job....just don't put your glasses on:



This really was deja vu all over again: the CDR oil cooler had threaded OEM style ports, where the MB cooler has the usual Corse plain ports requiring O-ringed push-fit connections on the hoses, the same as the RS crankcases. So I had to machine another couple of AN to push-fit adapters for the (now too long) hoses:



The short top hose became the long bottom hose which left just one hose to shorten, job done and and it's beer o'clock:



See you tomorrow for the next class in "Idjit Engineering 101"....