Steering Geometry

[bentbuilder_jawnn]

Has any one built bent with a radically shallow steering axis?

I designed this one according to http://bikesmithdesign.com/Design/12Steps.html parameters with 52 degree head tube and 5.6 inch rake to get the .5 inch trail.
[http://www.kreuzotter.de/english/elenk.htm]

Now the only thing I don’t understand is why LWB factory bikes like the Rans use such a steep steer axis as 60 degrees and 2 inch trail.




http://funnyfarmart.com/scans/scanbike2.jpg

[bentbuilder_jawnn]

this is a bike designed by mark stonich http://www.cyclingforums.com/showthread.php?t=99049

[bentbuilder_jawnn]

you are right about the CoG...I improved my drawing sence I did this one , but not so easy to get it scaned.

How long do you think the fork blades will need to be to get enough rake?

[bentbuilder_jawnn]

Is it possable to use one of the blade sets from Nova cycle supply?


build a new fork from scratch

[bentbuilder_jawnn]

If under seat steered bikes don't need a laid back steer axis, why are they not more popular?

Do you know any thing about flexable bike design? I want to build a flexable bike that will take 350 to 375 lbs. I see in the Hostel shop cataloge that the flexable Rans Stratus is rated for only 275lbs as are most others. One is ok for 320lbs, but I think they used tandom wheels.

Will just using larger diamiter tubes will it? The Volae bikes look very flexable, but also very light duty.

[wheelenwilly]

I found this may be it might be helpful to some one because it is way beyond me http://socrates.berkeley.edu/~fajans/pub/pdffiles/SteerBikeAJP.PDF

[bentbuilder_jawnn]

what kind of effect will I get from a 73 degree head tube with 1.5" rake/1.3"trail?

I intend to correct my short bikes steer axis from the 65 degrees it is at now. But if I use a smaller front tire it will be over corrected. well it's gotta be better than the 3" trail wheel flop I have now.

well I think it will be better if I build a new forx with 4 inch rake for .5" trail.

[bentbuilder_jawnn]

wish I could find a scientific paper like this about 'power systems' like the kdrive: http://funnyfarmart.com/Qring.htm








I found this may be it might be helpful to some one because it is way beyond me http://socrates.berkeley.edu/~fajans/pub/pdffiles/SteerBikeAJP.PDF

[bentbuilder_jawnn]

If you can't get self centering from your steering
ergonomics, you may find that low trail leaves a vague feeling to the
steering that's worse than resisting the wheelflop from too much
trail. The only SWB I've ever ridden that handled OK had an 80
degree head angle.

Weight distribution and distance from the riders
shoulders to the steering axis are what determines how well a 'bent
can be made to handle. I have MWBs with wheelbases of 42" and 45"
that are so stable that on steep, fast downhills I ride with one hand
in my lap to reduce wind drag. They have 2/3:1/3 weight
distribution, 6 and 9" of tiller with optimized handgrip orientation.

MWB = BB between 2" ahead of the front axle to 6" behind the
axle. Easy to get good ergonomics and weight distribution. Once
you get the BB even with or slightly behind the axle heel strike is
not a problem.

I was locked into some of the geometry on this one so it could use a
little more tiller and I rarely get a bit of heel strike.
http://bikesmithdesign.com/MyBikes/Raleigh/SideView2.jpg (http://bikesmithdesign.com/MyBikes/Raleigh/SideView2.jpg) 42" WB

On the 2nd MWB I moved the front wheel 2" forward and used a slightly
steeper head angle to eliminate heel strike and optimize tiller. I
moved the rear wheel one inch back to maintain weight distribution.
http://bikesmithdesign.com/MyBikes/RedDwarf/side_apples.jpg (http://bikesmithdesign.com/MyBikes/RedDwarf/side_apples.jpg) 45" WB

This one, built for a customer, has a shallower head angle and a 54"
wheelbase.
http://bikesmithdesign.com/Paul/PaulBlue.jpg (http://bikesmithdesign.com/Paul/PaulBlue.jpg)

All 3 handle about the same.

Mark Stonich;
BikeSmith Design & Fabrication
5349 Elliot Ave S. Minneapolis, Minnesota 55417 USA
Ph. (612) 824-2372 http://bikesmithdesign.com (http://bikesmithdesign.com/)
http://mnhpva.org (http://mnhpva.org/)

[bentbuilder_jawnn]

It is very difficult to find the proper bar placement with out a fit bike.

If your thighs pass up between your hands you can't turn the bars enough with out making them too wide.

I think it would be much easyer to build a bike using sterring linkage like the marader, or under seat sterring.

this is how I fixed the excessive wheel flop on my short bike, 68 degrees to 79 with .5" trail; http://funnyfarmart.com/images/steering.jpg

[bentbuilder_jawnn]

ok try this page: http://funnyfarmart.com/ultimate_touring_bike.htm
http://http//funnyfarmart.com/scans/ultimatetourbike.jpg
http://funnyfarmart.com/scans/ultimatetourbike.jpg

[bentbuilder_jawnn]

so I was thinking agian... a dangerus thing but some one must do it.

:rolleyes4:To use a steeper fork axis a remote steer axis is essential. Half-inch trail should be used even if you must rotate the fork to 80 degrees.



NOTE:
The lower the steer angle the easier it is to turn because the wheel turns on to its side using the arch of the wheel to turn the bike. 0-.5” (or half of the width of the front tire) trial removes the wheel flop. The counter balance of your arms keeps the wheel straight through high speed bumps.
[]
Most recumbent delta trikes use a standard steer fork to save money; set at 60 degrees as a compromise. The wheel must turn on its side because the trike can’t lean like a bike, but that produces wheel flop.
[]
The way to correct that problem is to add more rake for less trail. Best maneuverability can be had by dropping the steer axis down to around 50 degrees and rake the wheel axil to zero trail (or at least no more than 1.3”)



http://funnyfarmart.com/ad_images/zero_trail_trike.jpg