what are the effects of excessive trail



G

geepeetee

Guest
Hi

Still on this recumbent building project, i read that increasing the trail
helps stability, but there must be an optimum when the trail gets tto much,
what are the effects of this.

thanks

Gary

--
visit our website at www.justjents.co.uk
 
geepeetee wrote:
> Hi
>
> Still on this recumbent building project, i read that increasing the trail
> helps stability, but there must be an optimum when the trail gets tto much,
> what are the effects of this.
>
> thanks
>
> Gary
>

Trail increases all the forces on the handlebars. So you may experience
a tendency for the bike to wobble more at low speed. I call this the
ant'spring. It only effects most bikes below 5 miles an hour. You will
also experience more fork flop. The fork tends to turn in the direction
that the frame leans. IMHO this is a good thing. It allows us to balance
without having to think about it. The lean angle of the bike can be felt
in the hands and corrected by the hands without involving the mind.

Other forces are increased such as peddle steer etc. Many recumbents are
built with too little trail. It may be that the designers are all
criterium riders, but there you go.

I think that the general acceptance of recumbents would be better if
more production machines had more trail, or at least paid more attention
to handling. When a road racer gets off a recumbent and says "that's too
twitchy" we lost another convert.

That's why I wrote the book. All these values can be quantified and
predicted. We built 300 or so different bikes in my class and they
worked fine if the students followed the theory.

I am an old guy, and ham fisted. The students convinced me that we could
decrease trail by half and still have reasonable bikes.



Bill

--
Don’t be a 0 to 60 sheep, be a 60 mpg wolf. Yes Miles Per Gallon.

See some Bikes At:

http://home.earthlink.net/~wm.patterson/index.html


Class and Helicopter

http://www.calpoly.edu/~wpatters/

The Pony Express
http://www.geocities.com/Pentagon/Base/6850/PonySong.html


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>
> That's why I wrote the book.
>
>
> Bill


What book is that Bill? I am looking to design a bent in a cad program.
I have a welding friend who wants to help. I am looking for any
pertainant information.

Slugger
 
geepeetee wrote:
> Hi
>
> Still on this recumbent building project, i read that increasing the trail
> helps stability, but there must be an optimum when the trail gets tto much,
> what are the effects of this.
>
> thanks
>
> Gary
>

You would get too much stress on the fork crown, and you'd need really
really strong forks. In a typical bicycle the trail is set to get the
wheel to follow the CG to make the front wheel inherently stable, and
then the head tube is tilted back so that when you hit a bump, the fork
is forced back+upwards, "into" the head tube. So the fork crown (where
the steering tube and fork blades attach) is basically under
compression, not torque. .....Now you could build a bike that had 12
inches or more trail, and it would still be stable--but the fork blades
would need to reach backwards from the head tube, to reach the wheel.
And you'd get a LOT of torque-force put on the fork crown area. It would
work, it ould be stable and rideable but *I* would get the thickest MTB
head-tube + steerer tube, and build them forks WAY strong. No standard
bicycle fork out there is built for that much stress, applied in that way.
 
Thanks for replies, what would be a nominal amount of trail for a SWB
recumbent.

I have had half an inch suggested but thought it was a small amount because
this may reduce slightly when the suspension lowers due to the riders
weight.

So was thinking of going for one and a half inches, does this seem about
right.

thanks

Gary
"geepeetee" <[email protected]> wrote in message
news:[email protected]...
> Hi
>
> Still on this recumbent building project, i read that increasing the trail
> helps stability, but there must be an optimum when the trail gets tto
> much, what are the effects of this.
>
> thanks
>
> Gary
>
> --
> visit our website at www.justjents.co.uk
>
 
Slugger <[email protected]> wrote in news:160420052106354470%
[email protected]:

>
>>
>> That's why I wrote the book.
>>
>>
>> Bill

>
> What book is that Bill? I am looking to design a bent in a cad program.
> I have a welding friend who wants to help. I am looking for any
> pertainant information.
>
> Slugger


Bill Patterson's book is called "The Lords of the Chainrings" and should be
available on his web site.

<Chas>
 
DougC wrote:

>>

> You would get too much stress on the fork crown,

Bending the fork back does add stress to the fork and head tube area. If
you are building a bike, you can take that into account.

I would suggest that you start at 3 inches of trail. Build a fork with a
slot so that you can move the front wheel for and aft to get the feel
just the way you want.

Also, I do have some books available.

Dave Wilson from MIT was kind enough to review the book.


____________________
Professor Bill Patterson has been enthusing generations of students
wanting to divert their over-abundance of human power into building and
pedaling helicopters and, mainly, bicycles. He has assembled his advice
on designing bicycles of all types (including motor-cycles) into a
cheerful and copiously illustrated volume that has become something of a
classic: "The Lords of the Chainring". It is now in its third
edition. The emphasis is on steering design for stability and
responsiveness. You will find Bill's advice, given in a few equations
and graphs and in many photographs, not only on what to do but on what
not to do. It's a delightful and instructive book.

David Gordon (Dave) Wilson
author, Bicycling Science, third edition.
________________________________
You can get ordering info at"

http://www.calpoly.edu/~wpatters/lords.html

You can use paypal with my email [email protected]. I don't
know how that works, not being a business type

Bill


--
Don’t be a 0 to 60 sheep, be a 60 mpg wolf. Yes Miles Per Gallon.

See some Bikes At:

http://home.earthlink.net/~wm.patterson/index.html


Class and Helicopter

http://www.calpoly.edu/~wpatters/

The Pony Express
http://www.geocities.com/Pentagon/Base/6850/PonySong.html


Reply to [email protected]
[email protected]
[email protected]
 
Bill Patterson wrote:
> DougC wrote:
>
>>>

>> You would get too much stress on the fork crown,

>
> Bending the fork back does add stress to the fork and head tube area. If
> you are building a bike, you can take that into account.
>
> Bill
>
>

ALso you could do a trailing-arm type front suspension, that would help
smooth out a lot of the mechanical shock loads more evenly. If you
wanted it solid, I would bet that the crown area would need to be quite
a bit thicker than a regular fork to be as safe.
 
DougC wrote:

> ALso you could do a trailing-arm type front suspension, that would help
> smooth out a lot of the mechanical shock loads more evenly. If you
> wanted it solid, I would bet that the crown area would need to be quite
> a bit thicker than a regular fork to be as safe.

Take a look at my front drive moving BB low racer. It has a trailing
link front suspension. I also have a front suspension for the WYMS
tandem that I will try soon. Gary Dinsmore has a similar WYMS tandem
named "Green Dragon".

--
Don’t be a 0 to 60 sheep, be a 60 mpg wolf. Yes Miles Per Gallon.

See some Bikes At:

http://home.earthlink.net/~wm.patterson/index.html


Class and Helicopter

http://www.calpoly.edu/~wpatters/

The Pony Express
http://www.geocities.com/Pentagon/Base/6850/PonySong.html


Reply to [email protected]
[email protected]
[email protected]
 

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