Fully suspended MBB with 90 deg steering angle.

[Balor]

The project is nearly complete, I think I can showcase it now .

With bars (not entirely happy about them, but I need wide bars to clear my monumental thighs - this one has 680 wide bars, at least in line with a 'conventional' MTB and must fit ALL the doors .)

This is a very budget build, using 'wallmart' FS bike components. My goal was eliminate wheel flop and keep steering inertia to a minimum and BB and seat as low as possible, yet keep 'tiller length' in check because my last project, while perfectly rideable and even decently fast, is not very comfortable in that respect.

Should be perfect for bad roads and mild offroad, where MBB is great due to no foot-wheel conflict in turns and ability to install dual large wheels with wide tires.

It would be a while before I, myself, will be able to ride it, but the builder reports that suspension works great and does not bob much, and he was able to hop on and ride off right away, almost no 'MBB learning' required.
It is made of steel and, obviously, weight about as much as two Vendettas

By the way, there is a funny thing about FWD 'reverse bob' (it extends instead of compressing, due to reversed weight transfer and tire forces) and climbing steep inclines.

As you climb steep stuff, you front end is unweighted, hence, if you run little sag - you get zero sag and, therefore, zero bob exactly when you need it most! Kind of 'intelligent lockout', only 100% passive.

Cannot have that on RWD, ehehe. Talking about 'turning a liability into an advantage'.

 

[dtseng]

It's really great to see the project comes to fruition.

 

[bladderhead]

Actual springs at both ends. Underseat rack. Lots of space for another rack above the back wheel. The bars make it easy to prop it against a wall. All of which is cool.

I agree that angular momentum is bad, but the big black rectangle in front of the steering-axis looks like a ton. Maybe you could make it out of bamboo.

 

[Balor]

I agree that angular momentum is bad, but the big black rectangle in front of the steering-axis looks like a ton. Maybe you could make it out of bamboo.

Not exactly a ton, and radius makes much more (squared) difference than sheer weight. Plus, most of the weight comes from the legs (certainly in MY case).

What I'm not happy about is bars. I'm currently in brainstorming phase with the builder - how to improve them, possibly.

 

[bladderhead]

Linkage?

 

[Balor]

Linkage?

What linkage?

 

[Balor]

 

[dtseng]

It's a very nice looking recumbent/liegerad! I would suggest using Cruzbike's "dynamic boom" and drop handlebar.

 

[Balor]

That's a possibility, yea. "'Superman" bars are good offroad however, because they allow fully unimpeded entry/exit and ability to manuever sitting up, which is much easier... and this bike is not intended for speed records anyway.
I think I'll order a "cruzbike type" boom in addition for test, if it will not turn out took expencive .

 

[Balor]

The builder embarked on a 50 km ride, found it easier than on MTB - he swapped bikes with his buddy, who also hopped on and rode off right away, and also was faster than on MTB.
Neither of them are strong cyclists though.

 

[McWheels]

That's quite the thing, and I definitely appreciate the courage of your convictions to see it through to a working prototype. We now stare starkly at the difference between Can We (yes) and Will We (?). I certainly think there's quite a lot of scope to simplify the design around the key concept of the steering column being slightly ahead of the front axle, although in fairness you did add the suspension in there too, and with non-bespoke parts.

 

[Doug Burton]

Clever design - nice fabrication job! Good onya for making it a reality.

 

[dtseng]

How about this? You can move your knees sideways and the bar is out of the way. You can hold on the drop handlebar at three locations plus one on the brifter hood.
I would like to try 90 degrees steering angle just to see the riding characteristics without front and rear suspensions.

 

[Balor]

That's quite the thing, and I definitely appreciate the courage of your convictions to see it through to a working prototype. We now stare starkly at the difference between Can We (yes) and Will We (?). I certainly think there's quite a lot of scope to simplify the design around the key concept of the steering column being slightly ahead of the front axle, although in fairness you did add the suspension in there too, and with non-bespoke parts.

Well, there is nothing "magical" about negative offset, in fact zero offset with about 80 deg steering angle also have its merits (search velodreamer on facebook, he made MBB with cruzbike-like boom using this geometry).
It allows to have much less flop (above zero tho) and steering inertia as well, but with more conventional-looking geometry and less "tiller".

But if you want to have a suspencion, a combination of 90-ish steering angle and negative offset seems like a good design choice.

Besides weight, only disadvantage is "people below 170 cm need not apply" - due to space needed for suspencion travel, unless designed around 24" wheels.

 

[Balor]

How about this? You can move your knees sideways and the bar is out of the way. You can hold on the drop handlebar at three locations plus one on the brifter hood.
I would like to try 90 degrees steering angle just to see the riding characteristics without front and rear suspensions.
View attachment 6829

Hey, it does look good! I'll have it in mind, but I'll want to try such an arrangement first.

Anyway, I can say from my current (actually, a slight negative angle) prototype that it works great, but long tiller, combined with lots of recline, is a bit of a bother - very "twitchy".

If you sit upright and grab the bars near the stem (see photo):

(I've added some bar tape there) - it steeres nothing short of "great" - better than MTB.

I suspect that steering damper will work, but cycling-specific are rare and expencive, while fitting a moto damper is tricky to say the least - they are huge.

 

[bladderhead]

I was talking about a steering linkage like on LWB. I thought it was the tiller effect that was your problem.

 

[Balor]

I was talking about a steering linkage like on LWB. I thought it was the tiller effect that was your problem.

Oh, remote steering - I've tried that, even a few iterations. Didn't work out - it has to be fully triangulated like drivetrain, cause pedal feedback forces, amplified tenfold by leverage (it has to be compact) results in actual buckling of the frame and this "slop" makes steering imprecise to the point of "unrideability".

I may try that again sometime - once I'll think of a way to make it work.

 

[bladderhead]

I should have known that you would have already thought of all my ideas. Interesting seeing it evolve. What do you do with all the old frames?

 

[Balor]

I should have known that you would have already thought of all my ideas. Interesting seeing it evolve. What do you do with all the old frames?

WEll, the 'orange' 'semi-Zockra I'll likely be selling for a pittance, red prototype will be used as a stationary training bike most likely - this way it matters not that it weights a ton

 

[Balor]

By the way, I need to mention one downside builder described:

Wheel-calf contact when pedalling in sharp turns due to negative offset (first iteration of my negative angle prototype had 10 cm of negative offset and it was rather noticeable...
this one has to have about 6cm with sag, but fatter tires exacerbate it I guess) - which leads to 'rear' portion of the tire to 'extend' more outside of the turn and rub on the calf when the cranks are in about 3-6 o'clock position.

More of an annoyance though, because it is not likely to lead to a fall like foot strike on RWD bents (and can be avoided just the same by not pedalling and getting your leg out of the way), and totally not a problem riding on asphalt, but may be when riding, say, singletrack (especially in the mud, yuck).