Shortening front forks.
in [Tech]
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From: Greg.Procter on 25 Oct 2009 22:13 On Mon, 26 Oct 2009 10:32:03 +1300, The Older Gentleman <totallydeadmailbox(a)yahoo.co.uk> wrote: > little man upon the stair <macmiled(a)gmail.com> wrote: > >> So you see the lorry coming around the bend and he's taking up more >> than his share of the road and you countersteer by pushing the left >> hand bar forward. >> >> If the scooter initially out-tracks, the chassis follows the direction >> of the front wheel, which is pointed towards the lorry for a >> terrifying split second, before the >> scooter begins to turn left. > > <snip> > > As you've never actually ridden a scooter, let alone on (for you) the > 'wrong' side of the road, where does this advice come from? > The "driving side of the road" doesn't make much difference to the handling, other than when one goes against the flow, when it makes a considerable difference! As to road surfaces, it's hard to make absolute comparisons because not all US roads are the same and not all NZ roads are the same :-) However, we have half the population density of the US and the country is generally lumpy. Where I live is geographically near a sub-join between the Pacific and Australian techtonic plates with the two crunching upwards. In addition the region is made up of recent volcanic activity so the soil is very unstable - the roads are always moving. (slowly) Result paved but uneven surfaces, hills and valleys and regular 45-50mph bends on 60mph roads.
From: Greg.Procter on 25 Oct 2009 22:20 On Mon, 26 Oct 2009 11:12:17 +1300, paul c <toledobythesea(a)oohay.ac> wrote: > Greg.Procter wrote: >>> ... >> I think changing the rake would be more than I'm prepared to attempt, >> given that it's set by and within the body structure. It shouldn't be >> hard to increase the trail a fraction. (it's 75mm/3") Either making new >> and extended leading links or triple plates if I go with alternative >> front forks. >> ... > > Okay, you're closer to it than I am. I just assumed that using > non-leading forks would move the wheel rearward so the rake would have > to change. Photos seemed to suggest same, but my eyes aren't too hot, > so maybe I was wrong to think about rake. Rake seems adequate. Triple clamps are easy to mill to set the trail. (advantages of having CNC mill in workshop) In fact, the axle and head would have (exactly) the same relationship whether leading link or telescopic were used. The leading link design appears to have been used by the designers so they could use "parts- bin" rear suspension units rather than making new telescopic forks. As my motor design will have vastly more power and stopping distances have become more critical in the 50 odd years since the original design, I think the forks strength might be suspect. Greg.P.
From: little man upon the stair on 25 Oct 2009 22:28 On Oct 25, 7:13 pm, "Greg.Procter" <proc...(a)ihug.co.nz> wrote: > Where I live is geographically near a sub-join between the Pacific and > Australian techtonic plates with the two crunching upwards. > In addition the region is made up of recent volcanic activity so the soil > is very unstable - the roads are always moving. (slowly) Result paved but > uneven surfaces, hills and valleys and regular 45-50mph bends on 60mph > roads. North Island or South Island? BrianNZ is always ranting and raving about drinking in the pubs and hooning around near New Plymouth over on rec.motorcycles.
From: Greg.Procter on 25 Oct 2009 22:41 On Mon, 26 Oct 2009 15:28:04 +1300, little man upon the stair <macmiled(a)gmail.com> wrote: > On Oct 25, 7:13�pm, "Greg.Procter" <proc...(a)ihug.co.nz> wrote: > >> Where I live is geographically near a sub-join between the Pacific and >> Australian techtonic plates with the two crunching upwards. >> In addition the region is made up of recent volcanic activity so the >> soil >> is very unstable - the roads are always moving. (slowly) Result paved >> but >> uneven surfaces, hills and valleys and regular 45-50mph bends on 60mph � >> roads. > > North Island or South Island? BrianNZ is always ranting and raving > about drinking in the pubs and hooning around near New Plymouth over > on rec.motorcycles. I'm in the far North (AKA Northland) All dairying and pot-growing. New Plymouth is waaay south of here on the sides and base of a volcano that is the spitting image of Mt.Fujiama. (ie much flatter)
From: little man upon the stair on 25 Oct 2009 23:13
On Oct 25, 7:20 pm, "Greg.Procter" <proc...(a)ihug.co.nz> wrote: > The leading link design > appears to have been used by the designers so they could use "parts- > bin" rear suspension units rather than making new telescopic forks. Well, an Earles fork with rear suspension units is not all that bad an idea, if you're interested in suspension compliance. The shock absorber shafts are small diameter, so there's little stiction compared to a strut type fork. Problem with an Earles fork is that there is a lot of mass in front of the steering pivot, so the front end will waggle and hunt on rough pavement. I rode a friend's 250cc Greeves MX-5 in the Mojave desert a few times. It had too much weight on the front tire and the front end waggled and hunted in the dry sandwashes. I couldn't go fast enough to get the front tire up on top of the sand, so the Greeves wallowed along like a pig. Another Earles fork-equipped machine in those days was the popular Sachs 125. Problem was that the front brake drum was anchored to the Earles fork swing arm, and if the brake was applied it affected suspension compliance. Not good, having the brake make the front tire skid early. The next motorcycle my friend bought bought was a pretty Ossa Stiletto with conventional forks and much less weight on the front tire. It handled more like a Yamaha Enduro model like I was riding. But, by that time, the Japanese had caught onto lightweight motocrossers with long travel suspensions and those machines could skitter across the whoop-de-doos like they weren't even there... |