Inconsequential ramblings of an Old Git

[mangocrazy]

Courtesy of Polish ebay, an MT09 top and bottom yoke, no risers.

MT-09 SP top bottom yoke no risers.JPG (82.35 KiB) Viewed 574 times

What the above discussion has made me think of, is that I would do well to clean up the underside of the yoke where milling has taken place and smoothly radius all sharp edges and stress risers (as Screwd pointed out earlier).

[Mr. Dazzle]

Just FYI clamping epoxy (or anything similar in this context) joints will massively degrade the strength.

You want about 0.1-0.2mm of glue thickness, if you just clamp it tight you could well be too thin. You can pretty much have no strength at all if you have a thin joint. That's why I said a 'fixture' rather than just clamped.

You can buy 0.1 etc. sized glass beads (ballotini) to hold the joint at the right thickness while it's clamped. Or even just the correct SWG wire cunningly placed.

Baking in an oven at 80 or so would massively help too, but check the datasheets very carefully.

Buy some good glue too DP490 or EA9323 would be some things to Google.

Edit: oof maybe not the EA9323, seems you can only buy it in £250 'quart kits'. Those little double syringe kits of DP490 are good though. You'd need the special gun, but it means anything you glue has half a chance of being right.

[mangocrazy]

Yes, I did some research on epoxies and some of the Loctite stuff features glass beads to give the correct thickness of bond. 'Clamp' was probably the wrong word - I gave the top yoke surface a good coating of epoxy, laid the wedges in place, then applied gentle pressure. Too much pressure just made the wedges move off centre so that was the limiting factor. Then I turned the yoke face downwards onto a large aluminium plate and applied gentle pressure so that the yoke centre and wedge tops were all level and left the whole thing on the radiator to cure.

Anyway, it's done now, so all I have to decide is whether I trust my handiwork or not. I might also google additional life insurance...

[Mr. Dazzle]

The steel sleeve and rubber insert move any stress away from the point of maximum leverage, to the edge of a wide washer which bears on the outer ring of the mounting. The design is effectively flanged out to a much wider area.

BTW just to close this thought, I suspect the "hills" and the rubber inserts ^^^ might be shooting to achieve the same thing. That's why the hills start off 12mm thick and then slim down to 5mm at the bottom, as you come down the side of the hill the material transitions down to a lower thickness to (more) gently introduce the load into the rest of the yoke.

Or it could be entirely different, maybe Yamaha wanted the headstock in one place for suspension reasons but the bars somewhere else for ergonomic ones....

[A_morti]

Courtesy of Polish ebay, an MT09 top and bottom yoke, no risers.

MT-09 SP top bottom yoke no risers.JPG

The left hole on that seems to show a sleeve pressed in. Or idk, but seems like there's a raised lip there.

[mangocrazy]

Courtesy of Polish ebay, an MT09 top and bottom yoke, no risers.

MT-09 SP top bottom yoke no risers.JPG

The left hole on that seems to show a sleeve pressed in. Or idk, but seems like there's a raised lip there.

Hard to tell, but I suspect it's due to the way the risers have been machined. The base of the riser has a narrow ring machined around where the stud enters that's about 2mm deep and wide, which would correspond to the ring you see on the LH hole. I don't believe there is any steel insert in that yoke.

[mangocrazy]

I'm pretty sure there is no steel insert in the MT09 yoke, but I agree the idea has merit, for all the reasons you give. I'll ask my local machine shop if they can do that. What part of the Aprilia top yoke would you fill in with weld? And wouldn't there be a real danger of heat distortion through the welding process? There could also be problems with welding to cast ali - the welders I know can stick pretty much anything to anything else, but they do grumble when faced with cast ali...

[mangocrazy]

The Yamaha yoke has turrets where the risers bolt through, yours is flat-ish.
All I know is with risers half that length, several people had some serious squeaky bum moments.

But the depth of the area where the risers clamp is the same - the length of the riser stud guarantees that.

Do you have a link to the top yoke that failed with lower risers? Was it an FZ or an R1 yoke? Be very interested to see any pics of it.

[mangocrazy]

Get a role yoke made, your life is worth more than £200, if you need help finding someone to make a yoke I know if two people that will do it, neither will be quick. Also check out moto cnc on eBay, he may already make something that will do the job.

Thanks, I've had a look at moto-cnc's stuff and they do replacement yokes with risers for RSV1000, which use the same yoke as a Falco. The yoke I'm using for my experiments is an RSV one and is interchangeable. I've messaged him to see if he can make a yoke with a higher rise than his standard models. We'll see.

[mangocrazy]

While I was waiting for a reply from moto-cnc I went to see my local engineering shop to ask their view on the stresses going through the yoke and also to ask them to press in some hardened steel inserts. They were completely unfazed by what I'm doing and were of the view that there's nothing to worry about, especially once the inserts are in place. Just to cover all bases I've ordered a 3mm and 6mm ball end carbide burr so I can properly clean up any sharp edges left by the milling process.

It's probably good that I'm heading off to the French gaff tomorrow. I'll be there for best part of a month and by the time I get back I should have had time to reflect on the best course of action.

[Mr. Dazzle]

No offense like, but IME machinists know fuck all about stress. Not saying anything about your bars here, but I really wouldn't take a metal basher's* view on what a safe stress situation is. I've seen some right nonsense in this area. In fact it's often been my job to unpick what happened when stuff was changed/made differently "off piste" by people who didn't know they didn't know, IYSWIM.

On the flip side, don't ever ask me about how to make something

*other semi-derogatory terms are available

[mangocrazy]

The guy I spoke to is a qualified engineer and runs his own engineering firm, so he's not just your average lathe-monkey. But I accept that I'm out on my own here; if it did fail in use I would have absolutely no come back on anyone.

[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.

[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!"

[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.

[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!