Inconsequential ramblings of an Old Git

[Le_Fromage_Grande]

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.

[Mr. Dazzle]

In fairness to ya man, it does appear that the MT09 risers drop straight into a similar 'simple hole'. I half expected the MT09 ones to have a bunch of ribs or whatever on the underside.

I never did work out how to post a pic from an eBay ad....

https://www.ebay.co.uk/itm/165954154009 ... media=COPY

But...and this is the biggy....the MT09 yoke has those raised sections where the risers bolt in. So even if the argument is "the MT09 risers penetrate through the same thickness of Ali", I would have the assume Yamaha put those raised 'hills' in for a good reason, probably to redistribute stress.

Plus, as above, they're using one piece of metal not two bits semi-stuck together. In terms of getting loads "out" of the risers and into the rest of the yoke those stuck on plates will do little even if they're done perfectly. As you may have gathered, I have serious doubts they're done perfectly

[mangocrazy]

In fairness to ya man, it does appear that the MT09 risers drop straight into a similar 'simple hole'. I half expected the MT09 ones to have a bunch of ribs or whatever on the underside.

I never did work out how to post a pic from an eBay ad....

https://www.ebay.co.uk/itm/165954154009

I was just about to do a search on that and post it up, so thanks. I don't see anything very special about that top yoke.

But...and this is the biggy....the MT09 yoke has those raised sections where the risers bolt in. So even if the argument is "the MT09 risers penetrate through the same thickness of Ali", I would have the assume Yamaha put those raised 'hills' in for a good reason, probably to redistribute stress.

Plus, as above, they're using one piece of metal not two bits semi-stuck together.

Yeah, I get what you're saying, but those 'hills' are the only part of the yoke that is 12mm thick. The rest of it is a lot less - 5-6mm at a guess from the photos. The 'Priller yoke is actually more substantial, with deeper webbing and I've bonded a bunch of metal on top. I'll bet that in its unmodified form the 'Priller yoke weighs more than the Yam. Now I'm fully aware that gluing/bonding metal is never as strong as having a single piece of the same size, but those two substrates are also clamped together by the riser bolts, so are effectively 'almost' as strong. We can argue about 'almost' for days of course.

The Yamaha part looks like something that has had some serious FEA, but whether the engineers were concerned about strength or using the minimum amount of aluminium/reducing weight to a safe minimum is moot.

I dunno what prep you did, but for example in industry that ^^^ sort of joint would have been grit blasted or similar on both sides, chemically decreased, held in a fixture for bonding and then baked during the actual gluing.

Both surfaces were sanded, then degreased using brake cleaner, then clamped while bonding and stuck on a radiator for 24 hours.

[Screwdriver]

Couldn't find a picture of the MT09 top yoke, here's an MT07 for reference.



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.

[mangocrazy]

This is the top yoke off an MT-09 SP, underside view and top view. No steel sleeve or rubber mounting. That was probably done on the MT07 to damp out vibration through the bars.

MT-09 SP top yoke top front.JPG (197.41 KiB) Viewed 336 times

MT-09 SP top yoke underside.JPG (218.02 KiB) Viewed 336 times

For comparison, this is the underside of my top yoke:

DSCF3590.JPG (571.29 KiB) Viewed 334 times

[Screwdriver]

I have seen those and I can't tell what's under that nut.

[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 323 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.

[Screwdriver]

Looks like a steel insert.



Might not be a bad idea to at least fit something like that into your existing solution. Interference fit, press in a steel insert, moves the hardened steel bolt aways from the soft alloy, connects the two "halves", forces are spread over a larger (cylindrical) area.

Given the shape of the yoke though, I'd still be tempted to have that levelling piece built up from weld.

[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

[Screwdriver]

^^ I am certainly in that camp. I know that stress is a thing and I find the physics of "stress risers" fascinating but I certainly wouldn't trust myself to do a stress calculation. Best I can do is seat of the pants; if it looks strong enough it probably is.

I always err on the side of caution though.

Nothing too strong ever broke.

[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.