"Understeering" on a motorbike

[Mr Moofo]

What impact wrench did you buy? What’s the spec on it? NM?

I use them for stripping down engines and they’re worth their weight in gold.

I bought a Ryobi - just because it fits the battery pack I have.
But it is "high power" spec - so 400nm rather than the 270 of the normal one.
Whether that is a real 400 NM , who knows!

[Mr. Dazzle]

Maybe don't max it out when you do the nut back up then

[The Spin Doctor]

Impact wrench now bought to try and get the rear wheel nut off the bike. Ducati setting is 220 nm. A big breaker bar and a length of scaffold pipe have not made it move at all

Figures. I couldn't get the front sprocket undone on mine. Took it to the local car garage and got them to put their airgun tool on it.

[The Spin Doctor]

Wouldn't the RAC/AA be able to use it if you called them out?

We got Homestart out a few years ago after a camper tyre went flat on the drive and I couldn't shift the wheel nuts. He couldn't either. I managed to find a neighbour with a scaffolding pole and with both of us leaning on it we finally got the nuts undone.

What is it with people, torqueing things up to crazy levels?

[Mr Moofo]

Maybe don't max it out when you do the nut back up then

I had already worked that out ...
Think I will do it up just finger tight ...

[Mr. Dazzle]

I managed to find a neighbour with a scaffolding pole

I've got a 2m long carbon fibre driveshaft intended for an A380 which is my last resort.....its yet to be defeated!

Its the one just between the tee gearbox and the system torque limiter in this diagram.

[mangocrazy]

Isn't using a CF pole in that manner not playing to its strengths? I thought that CF in flexing/bending moments is not particularly strong. If it were to fail it wouldn't fail gracefully, that's for sure...

[Mr. Dazzle]

OK so this is a touch off topic

That particular shaft has alot of axial fibres in it. Fibres which run mostly along the length rather than at +/- 45 degrees as you'd expect in a torque shaft.

Reason being is twofold:

A) Its really long. Needs to not whirl (I.e. resonate) at high speed and hence needs a high flexural stiffness.
B) That particular shaft is a so called "compliant shaft". You see how its before the system torque limiter? The system torque limiter does pretty much what it says on the tin, but this shaft doesn't benefit from its protection. The reason for that I used to know, but I've forgotten. Something to do with failure modes and "catchers".

Anyway...that first shaft can withstand full motor torque and will just stall the drive unit if needed. However it also has to have a low torsional stiffness so you get the right torsional vibrational behavior in the system. The net result is a shafr which is bloody strong in torque (>4000Nm) but which can also wind up by more than 180 degrees before failing. It also has a high flexural stiffness.

All of that is achieved by having an usual laminate design which has loads of high strength material at all sorts of non typical angles.

Incidentally, before this kind of carbon fibre tech was developed (I think we were actually the first to qualify it) compliant shafts were a more complicated affair of two concentric metal shafts. One narrow solid shaft made from titanium or managing steel up the middle to give you the required low stiffness/high strength balance, then one hollow tube like a drainpipe riveted over the top to give you the vibration.

This is a textbook example case of how using carbon 'properly' can do so much more than make nice looking bodywork.

[mangocrazy]

Fair do's. It's a bit bloody over-engineered to be used as a scaffold pole though...

[Mr. Dazzle]

T'was also free I'd actually have to go out of my way to acquire a scaffold pole.

Oh, and it only weighs 1.5kg!

[Mr Moofo]

T'was also free I'd actually have to go out of my way to acquire a scaffold pole.

Oh, and it only weighs 1.5kg!

Can I have one ?

[The Spin Doctor]

Impressive )

[Mr. Dazzle]

T'was also free I'd actually have to go out of my way to acquire a scaffold pole.

Oh, and it only weighs 1.5kg!

Can I have one ?

I'd post you mine, but what it saves on weight it undoes again on being bloody long

[Hot_Air]

@Mr Moofo Once you’ve sorted your tyre, I’d consider the suspension setup.

While the Diavel (and Xdiavel) come with excellent suspension, the factory settings are dreadful. Ducati fits these bikes with Sachs or Öhlins, then lets a toddler do the settings. They all understeer and have a jarring ride on the factory settings.

And perhaps because of their geometry and that rear tyre, the suspension settings are crucial but finicky to get right. A professional suspension setup will transform the bike’s handling. It can handle beautifully with the correct setup.

[Mr Moofo]

The suspension on the original Diavel was rubbish. Forks were rock hard ( i ran with no compression and no preload) and the the rear was a soft as shit ( and bottomed out everywhere.
Which is why I has suspension mods done

[Hot_Air]

@Mr Moofo Which suspension mods did you have done?

I had this bike and the same issues (rock hard, bottomed out, understeered). I was weighing up the expense of suspension modifications, but saw a suspension guru first (much cheaper than suspension hardware!). A professional suspension setup alone transformed the bike; there’s no way my amateur suspension enthusiasm would have achieved this result.

[Mr Moofo]

K-Tech Front fork cartridges
Nitron "Track" rear ...

The rear is a million times better that the duke item ... just trying to fine tune it

[MrLongbeard]

Single sided swingarm (SSSA) problems. You don't get that nonsense on a bike with a conventional swingarm.

Was never a problem on my Speed Triple.

[Mr Moofo]

It was a lot easier to get the rear wheel back on ...

[Mr Moofo]

Interestingly, I found the rebound setting (the mount is tucked up behind the swing arm). I initially thought in had just 4 "clicks" - but in fact it has 18.
And it was fully open - so maximum rebound