Inconsequential ramblings of an Old Git

[Mr. Dazzle]

Nothing too strong ever broke.

And as if by magic an example pops up

Not picking on you here Screwd but it's a perfect case in point! If something is too chunky it can break because it "sucks all the load up". Stress is split between things in the ratio of their stiffnesses, so if you make one thing particularly chunky it ends up carrying all the load and breaking earlier

I have no idea who you man is Mango...but I'm a qualified engineer too and I wouldn't trust my self to turn a spacer down and retain all my fingers in the process It's a big field!

EDIT: BTW, in case you're wondering what one would do in this situation "for real". We'd FEA it We'd probably FEA the stock bar set up and then the new set up and see what's changed. Then maybe fuck around with how 'stiff' the riser to top yoke connection is to investigate the effect of rubber. It's actually fairly unlikely you'd get a yes/no FEA answer but by comparing it to the stock set up you can at least get an idea of whether it's better/worse.

Then we'd do a simple test. Just built a fixure to hold the yoke vertically probably then push on the end of the riser to see how much force that takes to break it (and where it breaks) then compare to some reasonable guestimates of in services forces. Realistically we'd probably make half a dozen or so, including the one you actually want to use.

This is why anything from a factory OEM is $$$. On the plus side though, you know it's not likely to kill you

[mangocrazy]

Yes, I'd assumed that FEA would be a big part of it, along with destructive testing. Before I commit to using the part I've modified I'd want to have the OE MT-09 SP part in my hand so I could have a proper look at it - see if they've used steel inserts where the risers bolt through, what the material thickness of the rest of the yoke is like - that kind of stuff, which probably means tracking down a breaker with one in stock and visiting him/her. But that will have to wait - I'm now busy throwing stuff in the van for a month in the S of F.

[Mr. Dazzle]

Bear in mind that the strength of the ally itself can easily be ±50% or even 100% depending on the grade.

Likely as not they're all made from similar types, but still...

[mangocrazy]

Bear in mind that the strength of the ally itself can easily be ±50% or even 100% depending on the grade.

Likely as not they're all made from similar types, but still...

I'd wager there's a better than average chance that the OE Yam one was made in China. Pretty sure the Aprilia one was made in Italy (before I had the cast-in lettering milled off). Not sure if that's better or not...

[Mr. Dazzle]

Means nothing basically. Plenty of high end aerospace stuff is made in China and plenty of utter crap is made in Sheffield. And vice versa.

[Screwdriver]

Nothing too strong ever broke.

And as if by magic an example pops up

Not picking on you here Screwd but it's a perfect case in point! If something is too chunky it can break because it "sucks all the load up". Stress is split between things in the ratio of their stiffnesses, so if you make one thing particularly chunky it ends up carrying all the load and breaking earlier

I have no idea who you man is Mango...but I'm a qualified engineer too and I wouldn't trust my self to turn a spacer down and retain all my fingers in the process It's a big field!

EDIT: BTW, in case you're wondering what one would do in this situation "for real". We'd FEA it We'd probably FEA the stock bar set up and then the new set up and see what's changed. Then maybe fuck around with how 'stiff' the riser to top yoke connection is to investigate the effect of rubber. It's actually fairly unlikely you'd get a yes/no FEA answer but by comparing it to the stock set up you can at least get an idea of whether it's better/worse.

Then we'd do a simple test. Just built a fixure to hold the yoke vertically probably then push on the end of the riser to see how much force that takes to break it (and where it breaks) then compare to some reasonable guestimates of in services forces. Realistically we'd probably make half a dozen or so, including the one you actually want to use.

This is why anything from a factory OEM is $$$. On the plus side though, you know it's not likely to kill you

If you substitute in the word "chunky" you might be onto something but if ANYTHING breaks, then it clearly wasn't strong enough.

Nothing too strong ever broke.

I assume you refer to something like having a chunky cast iron bracket bolted to say a table and the table breaks. That's an entirely different scenario. My favourite epithet stands. Clearly, the table wasn't strong enough...

Anyhow, enough of the semantics, I stopped playing with finite element analysis when Fusion 360 stopped it being free. Annoying but really, all I was after was the generative design to make things look pretty. Before anyone jumps on that (I'm looking at you Mr Dazzle ) I happen to think things look pretty to my eye when they are obviously well engineered.

But like I say, it's a seat of the pants thing for me and getting back to the original issue, looking at the prototype riser construction definitely set off a pucker alert.

[Mr. Dazzle]

The classic example is a beam with more than one support.



Say for example that middle support on the bottom diagram broke. Your inclination might be to reinforce it - that would potentially make it worse. The solution could very well be to make it more flimsy. This is my point really, erring on the side of caution isn't necessarily so.

A more accurate but less pithy saying might be "nothing which has been correctly designed to withstand the forces placed upon the system within which is resides ever broke, but the stress distribution in parts can be counter intuitive".

Bit of a mouthful

Perhaps..."eyeballing how strong something is may not be wise". It's shorter at least

I deffo agree with Screwd on one thing though, this sets the bum pucker off. I think in a work context I'd look at this and declare "to the FEA cave bat man!"

[Screwdriver]

...and that's fine but again you have to change my words and my meaning to argue against such an epithet. The system within which everything resides, is the thing I refer to. Without first breaking it up into component parts, you cannot argue with my statement.

Secondly, you are ignoring the consequence of your own argument. The "thing" you break is never the component which you decide is the thing I must refer to as being "too strong". Even under those circumstances, you are breaking something else in "the system" by moving the goalpost to a different sub component.

Nothing too strong ever broke.

[Mr. Dazzle]

Well yeah, if something is "too strong" it can't break, that'd be an oxymoron

My point is that correctly spotting what "too strong" is, is not something most people could do.

[Screwdriver]

Well yeah, if something is "too strong" it can't break, that'd be an oxymoron

My point is that correctly spotting what "too strong" is, is not something most people could do.

On that we can agree. But you don't have to run a fea to see that handlebar conversion has issues.

In my shed, I can most certainly make something "too strong". I did that once with a massive vice I bolted onto a wall. It wasn't one of my biggest, just a Record 36 iirc and I mounted it to a framework of cross bolted, glued railway sleepers. Attached firmly with rawlbolts.

At that point your "wider system" scenario comes into play since it was so strong I might risk tearing down the wall. But of course I realised that at the time and unless I drove into it with a forklift truck, I wasn't going to generate sufficient force to break either sub component of my shed system.

Had a devil of a job getting the bastard out when I no longer needed it. I had to peel those six inch wide beams off the wall one splinter at a time!

[Mr. Dazzle]

On that we can agree. But you don't have to run a fea to see that handlebar conversion has issues.

Nah, but that's where you'd go to get rid of them

I would offer to do it for you Mango, but for two problems.

- I'm not allowed to use work software for "homers"
- There's no enough info to go on!

[mangocrazy]

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]

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.

[mangocrazy]

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.

[Le_Fromage_Grande]

Could you use a Tuono top yoke on the Falco?

[Mr. Dazzle]

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?

[mangocrazy]

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.

[Screwdriver]

My guess is they will use your angled inserts but bolt them down with self tappers onto some fresh glue. Then bore out the mounting holes press in some steel sleeves for an interference fit.

Alloy welding would appear to be the better option but is fraught with problems regarding the composition of the existing yoke and potential problems with warping and spoiling whatever heat treatment they may have.

I suppose Tig welding those angled adapter mounts (plus the insert) would be a good compromise between the two, again, so long as the yoke is a good candidate for welding. Problem is, you don't find out about that until you try it which can be a painfully expensive lesson.

[mangocrazy]

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...?

[KungFooBob]

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