Steering angle.

Balor

Balor

Zen MBB Master
I wonder, what dictated decision of conventional steering angles of ~70 on vendetta and silvio? Ok, I can understand Silvio, due to telescoping forks that would not work for large bumps otherwise, but why Vendetta? It is rigid.

After all, you still need a custom fork, any offset for proper trail can go.

http://www.tonyfoale.com/Articles/RakeEx/RakeEx.htm

According to this article, even a high as 85 degrees of can go, one just needs some negative offset for trail, or even simply none for 700c wheel.

The braking (disk brakes) would not be affected due to triangulated, sorry for tautology, front triangle.

That would reduce wheel flop to nearly zero, and given that we have our legs tangled with front triangle all the time - it cannot be anything but good.

This article seems to confirm it:

http://www.recumbents.com/wisil/brown/alltogether.htm

Moving bottom bracket front wheel drive - sort of like the Cruzbike Vendetta. because you can fit a big front wheel, this is one SWB with the ride of a LWB. Fast too! It took me a long time to learn to ride them. Steering seems best to me with a fairly upright steering axis and short-ish (5 cm or less) trail.

I'm intending to go with about straight forks and 85 steering angle. It would also make pedal steering feedback more apparent, which I find a GOOD thing.

Any obvious caveats I might have missed?
Or is it only a marketing decision to make it more conventional for mere conventionality sake? I understand it is important on a production bicycle that has any chance of becoming popular, people are afraid of 'recumbent' position and moving bottom bracket enough as it is, but for a DIY project anything can go so long as it is functional.
 
RojoRacing

RojoRacing

Donut Powered Wise-guy
I've always wondered this same thing as well but with experience in the field of design nor any method to test other variations I haven't spent any time on the subject. I think any 2 wheels vehicle should be about to coast on it own in more or less a strait line. If you propel any DF bike or motorcycle without a rider it will proceed in a strait line until it drops below a jogging pace, hell motorcycles often toss their riders off and right themselves to continue on for another 1/4 miles. I haven't checked to see if the V will coast on it's own but I really doubt it would. I would of other RWD recumbent can old their own strait line without a rider?

I think if a Cruzbike could hold a strait line on its own it would be easier for some riders to learn to ride it and expand it's market appeal. Then again you rarely get something for nothing so what would you be giving up to gain that feature?
 
RAR

RAR

Well-Known Member
Balor said:
I wonder, what dictated decision of conventional steering angles of ~70 on vendetta and silvio? Ok, I can understand Silvio, due to telescoping forks that would not work for large bumps otherwise, but why Vendetta? It is rigid.

After all, you still need a custom fork, any offset for proper trail can go.

http://www.tonyfoale.com/Articles/RakeEx/RakeEx.htm

According to this article, even a high as 85 degrees of can go, one just needs some negative offset for trail, or even simply none for 700c wheel.

The braking (disk brakes) would not be affected due to triangulated, sorry for tautology, front triangle.

That would reduce wheel flop to nearly zero, and given that we have our legs tangled with front triangle all the time - it cannot be anything but good.

This article seems to confirm it:

http://www.recumbents.com/wisil/brown/alltogether.htm

Moving bottom bracket front wheel drive - sort of like the Cruzbike Vendetta. because you can fit a big front wheel, this is one SWB with the ride of a LWB. Fast too! It took me a long time to learn to ride them. Steering seems best to me with a fairly upright steering axis and short-ish (5 cm or less) trail.

I'm intending to go with about straight forks and 85 steering angle. It would also make pedal steering feedback more apparent, which I find a GOOD thing.

Any obvious caveats I might have missed?
Or is it only a marketing decision to make it more conventional for mere conventionality sake? I understand it is important on a production bicycle that has any chance of becoming popular, people are afraid of 'recumbent' position and moving bottom bracket enough as it is, but for a DIY project
Click to expand...
Balor said:
I wonder, what dictated decision of conventional steering angles of ~70 on vendetta and silvio? Ok, I can understand Silvio, due to telescoping forks that would not work for large bumps otherwise, but why Vendetta? It is rigid.

After all, you still need a custom fork, any offset for proper trail can go.

http://www.tonyfoale.com/Articles/RakeEx/RakeEx.htm

According to this article, even a high as 85 degrees of can go, one just needs some negative offset for trail, or even simply none for 700c wheel.

The braking (disk brakes) would not be affected due to triangulated, sorry for tautology, front triangle.

That would reduce wheel flop to nearly zero, and given that we have our legs tangled with front triangle all the time - it cannot be anything but good.

This article seems to confirm it:

http://www.recumbents.com/wisil/brown/alltogether.htm

Moving bottom bracket front wheel drive - sort of like the Cruzbike Vendetta. because you can fit a big front wheel, this is one SWB with the ride of a LWB. Fast too! It took me a long time to learn to ride them. Steering seems best to me with a fairly upright steering axis and short-ish (5 cm or less) trail.

I'm intending to go with about straight forks and 85 steering angle. It would also make pedal steering feedback more apparent, which I find a GOOD thing.

Any obvious caveats I might have missed?
Or is it only a marketing decision to make it more conventional for mere conventionality sake? I understand it is important on a production bicycle that has any chance of becoming popular, people are afraid of 'recumbent' position and moving bottom bracket enough as it is, but for a DIY project anything can go so long as it is functional.
Click to expand...
I'm pretty sure the steering would be so fast you couldn't ride it. A mountain bike has low head tube angle and it steers slowly, a road racing bike has a steeper head angle and it steers very quickly.
 
ratz

ratz

Wielder of the Rubber Mallet
Robert has tested the by swapping the forks for the current Silvio and the vendetta. The Silvio with a vendetta fort bike gets too twitchy at speed to be ridden safety down hill. Bike geometry in the real world is always an interesting test of theories.

As for stable coasting. There is a great thread here in the forums that studied and measured the math behind that. Someone (not posting from a cellphone) can dig up the link
 
castlerobber

castlerobber

Zen MBB Master
Balor

Balor

Zen MBB Master
ratz said:
Robert has tested the by swapping the forks for the current Silvio and the vendetta. The Silvio with a vendetta fort bike gets too twitchy at speed to be ridden safety down hill. Bike geometry in the real world is always an interesting test of theories.

As for stable coasting. There is a great thread here in the forums that studied and measured the math behind that. Someone (not posting from a cellphone) can dig up the link
Click to expand...

You cannot simply swap the forks without modification to offset. Otherwise you'll might get nearly zero or even negative trail, which was likely the case: after all, due to very different A2C (suspension) using vendetta fork on a Silvio would likely steepen the angle beyond indended 72 degrees, hence trail would get dangerously low.

The linked angle/rake/trail article showed that running motorcycle forks with 85 angle and zero offset makes for a stable ride at high speed AND lighter steering at slow speeds, but would result in heavy brake shudder and, unmentioned by likely possible, forks failing to react to 'square-edged' large bumps due to stiction when bump force would bent the stanchions.
 
Last edited:
MrSteve

MrSteve

Zen MBB Master
Rake and trail works hand in hand with C.G., wheelbase and wheel diameter.

Some people can learn to ride anything on wheels or on a wheel anywhere; Others ... not so much.

Alright, the original Sofrider V1 came stock with a rear shock which has a choice of three mounting holes for the front/frame mounting point.
Changing where the shock mounted in which one of those three holes changes the effective head angle.
My experience with this is:
-With a slack head angle, it took a lot of effort to combat flop when starting uphill. At first, this was no fun.
I kept it like this for weeks and learned to like it when I learned how to ride it well.

-With the minimum head angle, it took a lot of presence of mind to keep calm and steady during fast descents.
I kept it like this for months and learned to love it when I learned how to ride it well.

-With the shock mounted in the middle, the bikes handling was the least compromised, overall.
This is how the bike has been set up for years now.
John Tolhurst did a pretty good job, I think, with the geometry of these things.
But, as I learned for myself, so did the French with their very slack head angles.

That's my experience which is valid for me.
Your experience will be your own.

Carry on.
 
Balor

Balor

Zen MBB Master
Well, yea. Point is, you were changing only angle caster changing the rake.

If you could adjust rake too, I suspect that you might have gone all the way to 105 angle with negative rake and get massively improved handling at low (and zero - front triangle would no longer flop at all) speeds AND stability at high speeds.

Did John actually try that? Gotta ask him.
 
Robert O

Robert O

Well-Known Member
Balor said:
Hmm! Things are getting even more interesting!http://www.fastfwd.nl/index.php?id=35

Anyone tried FWD MBB with angle larger than 90 degress and negative offset?This is going to make heavy front triangle completely self-stabilizing!
Click to expand...
I think a couple of concepts have gone that way. Flevobike had a negative headtube angle; I've never ridden (or actually seen) one, but they manufactured them for a number of years. Pythons have a positive, pretty shallow angle on the center-steer pivot, but negative trail due to the big offset between the front wheel and the pivot point. Apparently they're stable at low to moderate speeds, but high speed stability is trickier. Hard to generalize, because all of them are homebuilt and there's no standard design.
 
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