adjustable slabby

[vizman]

my pal just sent me these images, no details....better content than the filth he usually sends me.

[vizman]

[vizman]

[vizman]

[Madb]

thats pretty cool and different piece of engineering. like that.

[SiBag]

Errrrrrrmmmmmmmm, that don't seem right. Just used to seeing the headstock been beefed up to keep it uber stiff..

Edited July 6, 2017 by SiBag

[Gammaboy]

Yeah, doesn't look particularly rigid to me!

The adjustable headstock on Leblowski's Bakker is probably a better way to do it. Or just weld in an enormous headstock tube to take a Ducati/MV steering head eccentric.

Edited July 6, 2017 by Gammaboy

[vizman]

i don't like it, almost solving an non existent problem on an 1100 slabby in the most complicated way.....it's not like you could really fine tune it any more than you could by up grading to more modern running gear in 'road guise' and i'm unsure as to what 'race series' would allow or warrant this modification that upgrading to more modern running gear couldn't solve either......

....it looks ugly and it looks flimsy (even if it's not) but if the fabricator nailed the 'brief' (if indeed there was a brief) then fair play. 

i just thought it was worth sharing as i'd never seen it done to a slabby this way before.

[Dezza]

Looks very odd, and an overcomplicated way of achieving the same result as a more simple combination of eccentrics in the steering head and adjustable yokes. Different though.

[dupersunc]

That's from  the drag bike rolling chassis that was on Eblag for the last few months.  The bike looked like it was very trick.  That looks nicely done but ultimately not sure what it achieved.

[vizman]

41 minutes ago, dupersunc said:

 That looks nicely done but ultimately not sure what it achieved.

[FJD]

Pretty obvious it was for a dragbike, so you can move the front wheel back as much as possible, and then get the rear out as far as you can, while still maintaining the given wheelbase

[no class]

Closest I came to adjustable fork angle was via the tripple trees..... had these on my slingy fighter..... yoshimura made them .

Edited July 7, 2017 by no class

[1168turbo]

ian king has a slingshot years ago with adj steering head.i think metmachex built some..

[nlovien]

I've got a set of spondon adjustable offset yokes that were originally for a slabby - 41mm diameter forks - used them on a few projects to find the offset sweet spot then replace with solid triple clamps - i'll post a pic up the morn, my head says - hmm two bolts holding the bit the holds the forks to the bit that holds the stem, dodgy - but never have I experienced an issue, I've even tried fitting smaller spacer in the bottom triple versus the top and yanking up the bolts to reduce rake - it worked - noticed on Niel Makenzies motogp spondon rotax - has the same - ok forsure this weighs about the same as a rizzla 5 skinner yet again, recon he put a shit load more braking force through them than i'll ever do, so good enough for him = dam't fine by me

Edited July 15, 2017 by nlovien
pic added

[nlovien]

On 07/07/2017 at 10:32 PM, no class said:

Closest I came to adjustable fork angle was via the tripple trees..... had these on my slingy fighter..... yoshimura made them .

can you explain how these work ref: rake angle ? - I can see them work ref: offset but I can't get my head around rake -  how  the top and bottom clamps line up with the fork tubes when the angle of the stem changes relative to the forks - is there a big spherical ball joint type bearing inside the coloured alloy bits ? - its of interest because i'd like to reduce the rake on a P&M without touching the frame

[Duckndive]

On 08/07/2017 at 7:24 PM, 1168turbo said:

ian king has a slingshot years ago with adj steering head.i think metmachex built some..

They made two frame,s with adjustable head stocks if I recall. And they looked fragile to say the least....

[no class]

4 hours ago, nlovien said:

can you explain how these work ref: rake angle ? - I can see them work ref: offset but I can't get my head around rake -  how  the top and bottom clamps line up with the fork tubes when the angle of the stem changes relative to the forks - is there a big spherical ball joint type bearing inside the coloured alloy bits ? - its of interest because i'd like to reduce the rake on a P&M without touching the frame

The inserts are color matched and are machined with angled holes ....each color has a certain degree....some were negative ogher ones go positive

[nlovien]

thanks - that's brilliant - so, if for example you want to reduce the rake from std ( dictated by the headstock angle) you effectively end up with the top triple clamp having more offset than the lower clamp and the forks no longer run parallel with the centre bearing stem - apologise for getting into the nitty gritty detail but what i've described is what I want to do inorder to change the rake without modifying a frame - thing is, it seems an obvious thing to do for older frames with shallow rake angles, yet you don't see it being done

noting - this is not about reducing trail, forsure this is easy done ref: offset, its about pulling the front wheel spindle back inorder to shift the cog fwd a bit

thanks for the info

[Gammaboy]

Changing the rake in the triples is exactly the same as changing the offset of the triples. Head angle is only driven by the frame.

[no class]

......yes ....you are correct . The use of angled yoke stems is still used today in the Harley aftermarket ......but we won't go there .

[nlovien]

17 hours ago, Gammaboy said:

Changing the rake in the triples is exactly the same as changing the offset of the triples. Head angle is only driven by the frame.

not quite, for impact on trail - yes, i.e. you can adjust trail using both rake and offset

in my case i'm looking at a tighter rake to bring the front wheel back ( its presently out like a chopper with what must be around 27deg) - aim is to shift weight fwd onto the front wheel

thanks

[Gammaboy]

16 minutes ago, nlovien said:

not quite, for impact on trail - yes, i.e. you can adjust trail using both rake and offset

in my case i'm looking at a tighter rake to bring the front wheel back ( its presently out like a chopper with what must be around 27deg) - aim is to shift weight fwd onto the front wheel

thanks

Fork rake altered by the triple, ie the stem and the fork leg now being not parallel, has exactly the same as effect as fucking around with the triple offsets.

If you want to pull the steering angle in tighter, you can't do it with the triples. Your options are chop the headstock and weld it back on at the agle you want, or crank a bunch of rear rideheight in to rotate the frame.

What you're talking about doing will result in keeping the 27 degree steering head angle, but you'll have about a foot of trail.

[nlovien]

good point, tried a few +/- drawings and it seems what happens is "with respect to pulling the wheel back", forsure it works but by the time you then increase the offset (pushing the wheel back out again) to get back to the same trail your almost back to where you started, there does seem to be a slight gain ( few mm) i.e. the wheel contact ends up a few mm further back for the same trail but not enough to make the kind of difference i'm looking for - thanks, i'll not waste anymore time in this direction - ok so the only solution without modifying the frame is eccentric bearings for the headstock - 

 

[Gammaboy]

11 hours ago, nlovien said:

good point, tried a few +/- drawings and it seems what happens is "with respect to pulling the wheel back", forsure it works but by the time you then increase the offset (pushing the wheel back out again) to get back to the same trail your almost back to where you started, there does seem to be a slight gain ( few mm) i.e. the wheel contact ends up a few mm further back for the same trail but not enough to make the kind of difference i'm looking for - thanks, i'll not waste anymore time in this direction - ok so the only solution without modifying the frame is eccentric bearings for the headstock - 

 

The Bimota head stocks used a tapered barrel roller bearing and inserts - the bearings are famously difficult to find, they're a steering column bearing from a mercedes truck. Much better off picking up the headstock eccentric from a Ducati or MV and machining up the enourmous "head tube" to weld in (actually, if you're modding a steel frame, try to find a crashed Ducati or MV F4 frame and just cut the head stock from it).

There's a thread on an italian 2 stroke board with excellent photos of doing this (and widening at the same time) to a Yomomaha TZR125 frame to build YZR500 replicas.

I have a vague recollection that the TL1000R had the facility to change head angle, but the insert from factory was concentric - the race kit had the adjustable insert.

Edited July 17, 2017 by Gammaboy