Monday, March 1, 2010

thoughts. cruzbike rucksack mount

I COULD just drill a hole in the seat post, to keep a backpack mount from pivot-ing sideways.
However, I wish to minimize invasive and destructive mods.
The post will be flush with the top lip of the seat back.
In fact, I may need to trim the seat back - notch it.
Well, the seat back has a complex curve that could be used to brace the pack mount post.
We don't need to imitate the ogive of the seat back.
All we need is cross bar the width of the seat back.
With two prongs that nestle inside either side of the seat lip on left and right.
This should brace the sack/pack mount.

So far, I have a series of 3 tubes that nestle together to work around existing bike architecture.
The seat post has a knurled end that makes the design trickier.
In order, from the bottom:
1) a pipe inside the full width of the seat tube
2) a pipe recessed to fit thru the knurled seat tube end
3) once above the top of the seat post, we can expand back to whatever diameter suits us.
Or just leave the narrow tube- probably more elegant.

The easiest telescoping mount arrangement would be a series of holes with a bolt across, or pin.
But switching back to a standard seat tube width would allow us to use a spare removable seat post lever.
Hmm. We need an adjustable clamp for the seat-brace-stabilizer crossbar, unless we plan to leave the post at one height.
A clamp of some variety seems appropriate.
The telescoping tube is still useful to compact the unit when not in use.
I don't really want it visible when not in use, so I'd like it to drop down behind the seat.
I'd LIKE the 'shoulder/arm hooks' for the sack/pack to fold down when not in use.
But that is pretty fancy.
I suppose the clunktek version would be welding on a flange with a drilled hole in it at the top of the central pack mount tube.
Then we use a bolt or pin to adjust the 'shoulder hook' units on a pivot.
Hmm. Running a strap across would secure the sack/pack into place.

Obviously we wish to keep the centre of balance down. A properly packed rucksack will do this.
There is the issue that we have a front-wheel-drive bike with even more weight over the rear tire.

The FWD inherently suffers from this flaw in a recumbent layout.
This flaw would not exist in a RWD design.

I suppose this favours a seat-forward design for FWD, with a front boom as extending forward as possible.
Looking at a Cruzbike layout, this would require some modification.

Aside: on a standard bike layout, I always thought an additional strut to form an trailer hitch' behind the rear wheel made sense.
Then instead of this huge off-centre trailer arm we would have instead a short and simple one.
This design would have great utility.

The benefit of such a design on the front wheel would be to act as a bumper in the event of an impact.
A soft aluminum tube could be designed with a curve in it. This way, it would deform and absorb energy in an impact.
It could work out cheaper than allowing the front wheel to take the impact.

The front tire, with a boom extension would allow a Cruzbike rider to load payload- ballast - low and in front of both the front tire as well as pedals. However I suspect this arrangement would result in erratic steering.
In this case, the combination of FWD and Cruzbike-front-boom design is not useful.
A standard SWB layout, however, would allow some tweaks to make this design work.
It would likely involve a triangular (or sturdy single tube) extension from around the pedals going downwards.
This could then take some sort of standard luggage mount.
For example, say, a sideways-facing pannier or a luggage rack.
Again, this is only of use to address traction in a FWD layout.

A bike with a seat and boom that can both move forward in SWB layout would allow one to shift the rider's Centre of Balance (CoB) forward to offset the additional weight of a rucksack at the rear.
I think most SWB aim for a weight distribution of 40% forward/ 60 rear.

D: a power-assist FWD non-boom 'bent bike would work well.
Strap the battery pack low and front on the extension I describe.
You can can use a triangular 2-tube design too. A chopped up rear wheel setup could work bolted onto the front wheel.
The low-and-front battery adds ballast to the front wheel for traction purposes. At the same time, the electric motor on the REAR tire distributes the torque on tires, resulting in 2-wheel drive. Both help prevent the front wheel from skipping on gravel on an incline. Dual suspension helps to keep the tires in contact with bumpy ground.
I expect my seat-suspension Mark I approach will NOT accomplish the latter as well.
The mass and momentum of the frame itself will result in 'catching air'. Still, the simple frame geometry and elegant seat-rider-suspension system does keep the mass of the rider from having this result. It is still much superior to no suspension.
It may also result in a cheaper overall cost, with a simple frame geometry sans suspension.
I suppose the design could be supplemented with tire-hub elastomer suspension.
Also, for the purpose of a fairing, the latter is more desirable. I don't want road vibration to induce turbulence, thereby delaminating the air flow in contact with the fairing.
An alternative approach I am considering involves elastomer-vibe-dampening mounts where the fairing contacts the frame.

The giant motors in the penthouse of the big buildings I work in use an array of giant springs to keep the motors suspended. Little vibration reaches the building frame.

I reiterate my aesthetic concern about the Cruzbike Conversion Kit- as well as their other designs.
The narrow steel tubes slapped onto a fat aluminum mountain bike frame looks out of place.
The kit would look right at home on a narrow steel tube diamond frame.
Though we'd need a lower top tube for the seat.

A kit made for a mountain bike ought to have the visual theme of the bike frame tubing.

Just to test, Maybe I'lll slap together 2 old alum. MTB frames. This would test for how light a bike can be.
It would also show how a bike can be visually more pleasing.

The Conversion Kit ought to be wide-diameter tubing, even if it remains steel.
The floppy front end suggests that every effort should be made to keep the weight of the kit down.
I certainly noticed a difference when I acquired aluminum pedal cranks!

Since I don't have kids, I tend not to think of them regarding bike design.
But the vicinity of the rucksack mount could as easily accommodate a children's seat.
This would allow them better sightlines, with something to look at other than an adult's back.
D: the elevated rear kid seat on an upright would be VERY unstable.
D: in low position, rear, on upright. The CoB is low but again, the kid looks at the adult's back.
The cargo bike layout is sooo handy but soo rare.
I wonder if anybody has designed a modular standard/cargo bike dual layout.
Just pull off the rear and swap out.
Even more fun would be telescopiing frame struts.
It recesses and nestles forward to be a 'standard bike'.
Just pull coupla pins- or use clamps - and pull out to telescope into carbo bike position.
Alotta overdesign - and mass- to do so though...

D: to avoid stray straps and feet in the rear tire, just building the bike from the get-go with a rear mount for luggage makes sense. We can mount a find wire guard around the rear tire.

Using mounting points for panniers, we can easily modify standard commercial folding luggage racks to hook on in the same fashion.
The only design that makes sense for permanently (standard commercial) affixed folding racks would involve a recessed edge.
The folded rack becomes the base of a higher mounted pannier. This would be a pretty heavy arrangement, though.
I remain intrigued by the idea of a standard-size folding luggage rack that mounts on an overly-wide pannier mount.
Hmm, a few months later and the design is pretty much complete in my head.
Keep in mind that I write stories and compose music as I drift between wakefulness and dream.
My subconscious is much more clever than my conscious, LOL!

In retrospect, I should get a mountain bike frame with 29" tires.
If I see a Y-frame of this variety, then I'll likely go to the effort of pulling the bent bike kit off the youth 24" tire frame.
I suspect I'm too heavy for the shocks also.
The 24" tires with standard gears would spin out around 25kph.
I cheaped out and bought a new bottom gear. That eked out a few KPHs.
The bigger improvement was prohibitively expensive- a new chainring.
It would have had me spinning out at 30kph.
But I CRUISE at 30kph.
Even a 26" tire would have led to the same problem.
Thus my desire to switch to a 29er frame.
I am checking in at Recycle Cycles, a used bike shop that operates as part of the Kitchener Work Centre.
Those guys have been very helpful!
I doubt they'll have something as particular as a 29er alum. frame y-suspension bike.
But hope springs eternal.

Since the Mark I design is simply NOT in the budget this year, I need to fiddle with the kit I have.


Dino Snider said...

very sweet backpack- converts to/from pannier
d: ouch 80 bux. could wear 2 strapped front/back of torso. I had to lug all my worldy possession 40km to nearby city bus terminal once. Strapped a rucksack on rear and backpack front.
I tried standard backpack front of toso on SWB bent rental. Damn thing kept hitting my knees.
A tiny folds-into-small-pouch backpack I found hikes up high enough - but tears if you fill it. Otherwise nice.

奇奇怪怪 said...