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Biggest fork tubes?

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Pete.
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PostPosted: 20:20 - 05 Jan 2014    Post subject: Biggest fork tubes? Reply with quote

I need to source a single fork tube (the chome/nitrided slider bit) for a non-bike-related project. It's got to be perfectly straight and good finish and as large as possible in diameter. What bikes have the largest diameter tubes in the forks? I'm looking for a minimum of 42mm ID but ideally I'd like at least 46mm.
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CaNsA
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PostPosted: 20:29 - 05 Jan 2014    Post subject: Reply with quote

1200 Bandits used a 43mm unit and 1250 Bandits do too.
01-04 FZ1 Yamaha's use a 43mm unit also

46mm
SV1000 not sure which year though.
ZX6R 98-02
ZX9R 98+
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Kickstart
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PostPosted: 20:30 - 05 Jan 2014    Post subject: Reply with quote

Hi

Looking at the ABE catalogue at the dimensions, the KTM 620 Duke from 1998 with a 50mm o/d fork, which is the largest I can find. MV F4 might be easier to find has a 49mm o/d.

All the best

Keith
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Wafer_Thin_Ham
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PostPosted: 20:31 - 05 Jan 2014    Post subject: Reply with quote

MV Agusta F4 1000S uses a 50mm fork. Fairly sure there's a special edition that goes up to 53mm. EDIT-Damn you Keith. Laughing
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Pete.
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PostPosted: 20:34 - 05 Jan 2014    Post subject: Reply with quote

Are we talking OD of the top sections of USD forks or OD of the sliding tubes? I'm after the largest diameter sliding tube.
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Wafer_Thin_Ham
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PostPosted: 20:36 - 05 Jan 2014    Post subject: Reply with quote

Pete. wrote:
Are we talking OD of the top sections of USD forks or OD of the sliding tubes? I'm after the largest diameter sliding tube.


Sliding tube bit.
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Kickstart
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PostPosted: 20:36 - 05 Jan 2014    Post subject: Reply with quote

Hi

Those are the dimensions of the fork tubes (ie, chromed bit). Can double check for most of them against the fork seal size on Wemoto.

All the best

Keith
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Nick 50
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PostPosted: 20:39 - 05 Jan 2014    Post subject: Reply with quote

Can i ask what it is for, would something else not work? Hydraulic Actuator perhaps??
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Wafer_Thin_Ham
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PostPosted: 20:40 - 05 Jan 2014    Post subject: Reply with quote

Vincent wrote:
GSXR1000 K4, (2004?), stanchions, (sliders), up are 46mm I believe. Should be a few used ones around I reckon.


They're 43mm. Thumbs Up
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Kickstart
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PostPosted: 20:40 - 05 Jan 2014    Post subject: Reply with quote

Hi

Looks like a few others might use 50mm fork. Ducati Hypermotard and the Bimota DB10 both seem to use a 50mm Marzocchi fork. However these are probably new enough that finding a spare fork will be expensive.

All the best

Keith
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sidewinder
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PostPosted: 20:42 - 05 Jan 2014    Post subject: Reply with quote

Wouldn't motocross bikes have large ones?
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Wafer_Thin_Ham
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PostPosted: 20:48 - 05 Jan 2014    Post subject: Reply with quote

sidewinder wrote:
Wouldn't motocross bikes have large ones?


A quick google says they're of a broadly similar size, but the damping and spring rates would be way off, and you'd have far too much travel.
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Pete.
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PostPosted: 20:49 - 05 Jan 2014    Post subject: Reply with quote

Nick 50 wrote:
Can i ask what it is for, would something else not work? Hydraulic Actuator perhaps??


Very possibly.

I'm building an air bearing spindle - works on the same principle as the air hockey game where you have a floating puck, except that this has a floating shaft. Research shows that I need a clearance of about 1 thou per side from spindle to housing and a very fine finish. You can buy them, but they are quite expensive and then you have to buy the collets. I have a full set of very nice collets but no-one makes a suitable spindle for that particular type. My collets have an OD of 41.28mm and I'd ideally like a draw-tube so need another 5mm on top of that, but failing that I could fudge a system where I thread the collet into the tube directly.
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Az
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PostPosted: 20:59 - 05 Jan 2014    Post subject: Re: Biggest fork tubes? Reply with quote

Pete. wrote:
I need to source a single fork tube (the chome/nitrided slider bit). I'm looking for a minimum of 42mm ID but ideally I'd like at least 46mm.


Fork stanchions?
Someone said that bandit 12 forks are 43mm and a quick ebay search later... and i found these
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Pete.
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PostPosted: 21:09 - 05 Jan 2014    Post subject: Re: Biggest fork tubes? Reply with quote

Az- wrote:
Pete. wrote:
I need to source a single fork tube (the chome/nitrided slider bit). I'm looking for a minimum of 42mm ID but ideally I'd like at least 46mm.


Fork stanchions?
Someone said that bandit 12 forks are 43mm and a quick ebay search later... and i found these


43mm OD won't get me 42mm ID unfortunately, it only allows half a millimeter wall thickness.
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132.9mph off and walked away. Gear is good, gear is good, gear is very very good Very Happy
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Kickstart
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PostPosted: 21:13 - 05 Jan 2014    Post subject: Reply with quote

Hi

I would be a bit unsure that he inside of a fork is finished to anything like an accuracy of 1 thou. I would think for bike use the finish there is fairly irrelevant so little effort would go into making it accurate.

All the best

Keith
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Nick 50
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PostPosted: 21:30 - 05 Jan 2014    Post subject: Reply with quote

What about hyrdaulic honed tube?

https://www.indiamart.com/gpmhydraulics/hydraulic-honed-tubes.html

"Internal Roughness:Ra value 0.2 - Ra 0.3 (Micron)"

That would be way smoother than a fork imo
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Pete.
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PostPosted: 21:31 - 05 Jan 2014    Post subject: Reply with quote

Kickstart wrote:
Hi

I would be a bit unsure that he inside of a fork is finished to anything like an accuracy of 1 thou. I would think for bike use the finish there is fairly irrelevant so little effort would go into making it accurate.

All the best

Keith


The ID isn't so important - it's the OD that needs the fine finish since it is a mating part of the air bearing. The ID needs only be fairly concentric.
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132.9mph off and walked away. Gear is good, gear is good, gear is very very good Very Happy
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Pete.
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PostPosted: 21:35 - 05 Jan 2014    Post subject: Reply with quote

Nick 50 wrote:
What about hyrdaulic honed tube?

https://www.indiamart.com/gpmhydraulics/hydraulic-honed-tubes.html

"Internal Roughness:Ra value 0.2 - Ra 0.3 (Micron)"

That would be way smoother than a fork imo


That'll be my second option I think. I could manufacture either an ID or an OD hone but I thought I'd look into finding a suitable tube for at least half of it first, and fork tubes seemed the obvious place to start.
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132.9mph off and walked away. Gear is good, gear is good, gear is very very good Very Happy
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kramdra
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PostPosted: 22:06 - 05 Jan 2014    Post subject: Reply with quote

A fork stantion is not going to be anywhere near that tollerance espeically a used one Laughing However having a straight-ish bit of tube to begin with probably saves some machining costs or effort from the project?


Intresting project.. please post a thread about it.
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Suntan Sid
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PostPosted: 11:57 - 07 Jan 2014    Post subject: Reply with quote

Have a look at this!

https://scandalon.com/2009/06/motorcycle-fork-diameter-chart/

Hope it helps.
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daemonoid
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PostPosted: 12:45 - 07 Jan 2014    Post subject: Re: Biggest fork tubes? Reply with quote

Pete. wrote:
I need to source a single fork tube (the chome/nitrided slider bit) for a non-bike-related project. It's got to be perfectly straight and good finish and as large as possible in diameter. What bikes have the largest diameter tubes in the forks? I'm looking for a minimum of 42mm ID but ideally I'd like at least 46mm.


Streetfighter pogostick?
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Pete.
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PostPosted: 21:56 - 28 Jan 2014    Post subject: Reply with quote

kramdra wrote:
A fork stantion is not going to be anywhere near that tollerance espeically a used one Laughing However having a straight-ish bit of tube to begin with probably saves some machining costs or effort from the project?


Intresting project.. please post a thread about it.


Somebody sent me a well-used 'busa fork tube and I stuck in on my comparator stand.

Top of the tube = .0004" oval
Bottom of tube exposed part (on the bike) = .0009" oval with .0005" wear-spot where it rides on the bottom bush.

So no, not good enough. I could make a hone and try to halve those figures, might still do that, but really I think I need to be down to a couple of tenths at worst to have a chance of this thing gliding on air.
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132.9mph off and walked away. Gear is good, gear is good, gear is very very good Very Happy
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