revtothelimit - motorbike forum

Well, for approximately 4 weeks I'm going to forget all about it and let the subconscious deal with it. Instead I'll be turning my conscious mind (and hands) to final plumbing and commissioning of a solar thermal system, finding out where the leak is in my woodburning stove back boiler circuit, ignoring the Lancia and its (probably) broken cylinder head gasket and trying to figure out why the VFR goes 'clonk' over slow, sharp-edged bumps (we have discussed this before)...

There will be a mountain of other, smaller stuff but that's enough for the moment.

Screwdriver wrote: Tue Apr 11, 2023 7:33 pm Possibly the best mod I made to my venerable old Fazer thou was to stick on a set of Fat Bars (and Fat Bar risers!).

There is something immensely satisfying about having the bike just exactly as you like it.

You definitely have something to look forwards to when the bars are sorted and the sun pops out.

Yes, I've always been quite fussy about that kind of thing, especially suspension and brakes. But as I get older (and older) riding position becomes really, really important. When I was younger it was all ace bars and clip-ons. In 1980 I regarded the OE bars on my LC as far too sit up and beg. Now they feel quite sporty... I'm definitely looking forward to setting off on the Falco once it's effectively been turned into a Tuono.

Could you use a Tuono top yoke on the Falco?

Le_Fromage_Grande wrote: Tue Apr 11, 2023 9:37 pm Could you use a Tuono top yoke on the Falco?

I have been wondering that since about 10 pages ago

I assume there's some reason not?

This is where it all gets a bit confusing. Most of the top yokes on Ebay for RSV Milles also list them as interchangeable for Tuonos, but most of these top yokes don't show any provision for bolting a set of risers on. This is the only one I can find with holes in the top yoke for the risers:

https://www.ebay.co.uk/itm/314246217049

What makes it even stranger is that these just look like a top yoke off an RSV or Falco but with a hole drilled through the angled portion of the top yoke (the very part I tried to 'level up' using an ali wedge)...!

So I don't know. I think the best thing I can do is to pay Griff Wooley of AP Workshops a visit and talk to him.

In fact, on thinking about it, I should have done that first thing...

Gen 2 Tuonos are a different beast entirely and I don't believe fork parts are interchangeable between generations.

I've already ruled out aluminium welding due to potential warping with heat, and to be honest I can't see what benefits ali welding would bring to the party as it stands. The wedges are already firmly bonded to the top deck and the only thing that welding would do would be to weaken or destroy that bond. While I'm away my engineering shop will be pressing in hardened steel inserts with a 2mm wall thickness, this should further tie the various pieces together and spread the various loads.

Before I leave I'll be ringing Griff and find out for definite how the Gen 1 (non-Ohlins) risers were attached to the top yoke and how (if at all) the Tuono top yoke differed from the RSV/Falco item. That should give me good clues about how Aprilia dealt with the stresses involved. Who knows - maybe a Gen 1 Tuono top yoke and risers should have been The Plan all along...?

The parts diagram is on Fowlers website, I'd post a link if it wasn't for this dashed idleness.

Not sure if it helps much ( if at all) , as mine's the Factory but couple of pics below of my standard Gen1 Tuono top yoke.
On mine the "leveling up" is part of the top surface casting

Now that makes more sense... a flat surface to mount something to

Think it might be a finished machined casting, looking at the underside?

Screwdriver wrote: Wed Apr 12, 2023 9:45 am

To my untrained eye, that looks a lot more like it's been machined from billet.

Would that make it stronger/better ?

weeksy wrote: Wed Apr 12, 2023 9:49 am

Screwdriver wrote: Wed Apr 12, 2023 9:45 am

To my untrained eye, that looks a lot more like it's been machined from billet.

Would that make it stronger/better ?

Received wisdom of the internet is that billet is stronger.

Reality is far more complicated! It's undeniably true that you see a lot of "billet" (no-one calls it that) in motorsport and the like, but that's mostly for lead time and low volume production reasons.

Looking at the pics again, I think Screwd is probably right, I think the underside is just dirty. Doubly so when you look at the risers themselves, clearly machined from plate. I suspect the driving reason was cost more than anything, Aprilia probably don't/didn't make enough to bother setting up castings.

That yoke is what....40-50mm deep overall? 50mm Ally plate is basically an off the shelf product, cheap as chips.

Mr. Dazzle wrote: Wed Apr 12, 2023 9:51 am

weeksy wrote: Wed Apr 12, 2023 9:49 am

Screwdriver wrote: Wed Apr 12, 2023 9:45 am

To my untrained eye, that looks a lot more like it's been machined from billet.

Would that make it stronger/better ?

Received wisdom of the internet is that billet is stronger.

Reality is far more complicated! It's undeniably true that you see a lot of "billet" (no-one calls it that) in motorsport and the like, but that's mostly for lead time and low volume production reasons.

Looking at the pics again, I think Screwd is probably right, I think the underside is just dirty. Doubly so when you look at the risers themselves, clearly machined from plate. I suspect the driving reason was cost more than anything, Aprilia probably don't/didn't make enough to bother setting up castings.

That yoke is what....40-50mm deep overall? 50mm Ally plate is basically an off the shelf product, cheap as chips.

It's a machined casting.

They are Ohlins forks in my model- I don't know whether Aprilia buy the whole assembly including the top yoke from Ohlins or just the fork legs, but whatever, the top yoke is quite different (and a lot more substantial) looking than the one on the non-Ohlins variant of the Tuono.

So now he needs yokes, forks, calipers and a wheel?

Mrs.Mango will have his balls.

Mr. Dazzle wrote: Wed Apr 12, 2023 9:51 am Reality is far more complicated!

Told ya

Generally. I don't think it is as simple as you make out with the skin thing though.

I wouldn't mind betting Aprilia (and others) also have a common parent yoke casting whcih gets machined into different models.

That Touno one does look to be machined all over though, it's all chamfers and corners, no rads or swoops...which is why l reckon/reckoned its machined from solid. The risers are blatantly plate.

Mr. Dazzle wrote: Thu Apr 13, 2023 6:54 am

Mr. Dazzle wrote: Wed Apr 12, 2023 9:51 am Reality is far more complicated!

Told ya

(As you suggested earlier) The whole 'billet' thing probably adds more confusion than light. Probably because of steel billet which is hot forged/rolled and has particular properties as a result. Aluminum/alloy 'billet' is usually just a cast lump.

I'm pretty rusty on all this stuff now (the last time I was involved was making Hepolite pistons - cast, machined).

Unless it's Ally plate, which is rolled to thickness....

Honestly...of all the bits of metal I've seen stacked up in the machine shop, it's almost universally rolled/drawn plate and bar.

Pistons on the other hand are often pressure die cast, rather that just straight up cast. Exactly what it sounds like. They're pretty much universally post cast heat treated too, which completely changes the effects Screwd mentions. Indeed, that's the point of doing it!

Mr. Dazzle wrote: Thu Apr 13, 2023 7:42 am Unless it's Ally plate, which is rolled to thickness....

Honestly...of all the bits of metal I've seen stacked up in the machine shop, it's almost universally rolled/drawn plate and bar.

Pistons on the other hand are often pressure die cast, rather that just straight up cast. Exactly what it sounds like. They're pretty much universally post cast heat treated too, which completely changes the effects Screwd mentions. Indeed, that's the point of doing it!

Some alloys work harden on rolling too. I don't suppose they anneal it after - unless it's part of the continuous rolling operation. As you say, the heat treatment of pistons was a big part of the operation (along with some pretty thorough NDT).

Complicated business.