Tricycle design advice requested



Finished building my first tricycle (tadpole) a few days ago. Never
ridden one before, in fact, I've never seen one other than on the
Internet. I've got most of the bugs worked out and have about 25 miles
on it so far. It's faster than my MTB and seems to climb better than
my "normal" LWB recumbent but so far I've been reluctant to go over
about 18 MPH. The reason being that it has very quick steering. It's
stable and straightens out if I let go of the steering bars with only a
small amount of oscillation about neutral. It may just be me not being
acclimated to a trike but I'm a bit scared of it at speed. After my
first tumble I've learned how to stay in the seat until the inside
front tire lifts :) Kind of like flying a hull on a Hobi.........

A few facts:
Wheel base 43in
Front track 32in
Center of gravity - The over all balance seems to be good.
Turning radius about 12 ft - Don't really need it that tight
Steering 2 bars direct to kingpin with neutral ackerman geometry
(I like the simplicity and ergonomics) Trail is around 20mm.
Wheel size(s) 20x2.125 front 26x2.1 rear

I don't really have any complaints about the steering geometry other
than a bit too much scrub radius, due to some poor jigging/measuring.
It's not all that much - about 15mm - and even with 100% asymmetrical
brake application is very controllable. Bump steer is noticeable but
not objectionable.


What I would like to know is, if this steering quickness and
sensitivity are normal for a trike and if not what might I do to reduce
the sensitivity?

2 obvious solutions are increased wheelbase and/or a steering mechanism
with reduced ratio. I really don't want to mess with the wheelbase as
I find the overall balance of weight front to rear to be very good the
way it is now. I also like the simplicity of the direct steering, but
I'll change whatever needs to be changed to feel comfortable at higher
speeds.


It's fun to ride the way it is but I was hoping for a practical
commuter vehicle. I'd really like to be comfortable/confidant at 45+
mph. Is this at all realistic?
================
Leon McAtee
I can't pedal 45mph but we have plenty of hills.........
 
S

Sunset Lowracer [TM] Fanatic

Guest
[email protected] wrote:
> Finished building my first tricycle (tadpole) a few days ago. Never
> ridden one before, in fact, I've never seen one other than on the
> Internet. I've got most of the bugs worked out and have about 25 miles
> on it so far. It's faster than my MTB and seems to climb better than
> my "normal" LWB recumbent but so far I've been reluctant to go over
> about 18 MPH. The reason being that it has very quick steering. It's
> stable and straightens out if I let go of the steering bars with only a
> small amount of oscillation about neutral. It may just be me not being
> acclimated to a trike but I'm a bit scared of it at speed. After my
> first tumble I've learned how to stay in the seat until the inside
> front tire lifts :) Kind of like flying a hull on a Hobi.........
>
> A few facts:
> Wheel base 43in
> Front track 32in
> Center of gravity - The over all balance seems to be good.
> Turning radius about 12 ft - Don't really need it that tight
> Steering 2 bars direct to kingpin with neutral ackerman geometry
> (I like the simplicity and ergonomics) Trail is around 20mm.
> Wheel size(s) 20x2.125 front 26x2.1 rear
>
> I don't really have any complaints about the steering geometry other
> than a bit too much scrub radius, due to some poor jigging/measuring.
> It's not all that much - about 15mm - and even with 100% asymmetrical
> brake application is very controllable. Bump steer is noticeable but
> not objectionable.
>
>
> What I would like to know is, if this steering quickness and
> sensitivity are normal for a trike and if not what might I do to reduce
> the sensitivity?
>
> 2 obvious solutions are increased wheelbase and/or a steering mechanism
> with reduced ratio. I really don't want to mess with the wheelbase as
> I find the overall balance of weight front to rear to be very good the
> way it is now. I also like the simplicity of the direct steering, but
> I'll change whatever needs to be changed to feel comfortable at higher
> speeds.
>
>
> It's fun to ride the way it is but I was hoping for a practical
> commuter vehicle. I'd really like to be comfortable/confidant at 45+
> mph. Is this at all realistic?


Oversensitive steering has been a complaint about several commercially
available tadpole trikes, and is generally considered to be a matter of
steering geometry. While there is obviously much information about
steering geometry design for multi-track vehicles, solving this issue
is not a trivial problem.

Since it may not be practical to modify an existing trike, one possible
solution would be attach a dashpot (hydraulic damper) to the steering
linkage.
--
Tom Sherman - Fox River Valley
Hominid - The Other White Meat!
 
>>While there is obviously much information about
steering geometry design for multi-track vehicles, solving this issue
is not a trivial problem. <<

Seem to have found some luck. 'Tis kind of amazing what another 3-4
degrees of castor does. Didn't get much time to ride last night (no
lights and tired) after re-welding but I expect good things today. I
now have too much trail, resulting in more bump steer but it's still
not all that objectionable. I'll just have to re-jig before I add any
fairings.

Haven't had this much fun on a bicycle since my old Atala.......When I
was still young and in shape :)
===============
Leon McAtee