Openbike - New pages [en]

Jonny 9.5

2012-04-13T07:00:44Z

Jonny9point5:

[[File:Jonny Python_side.jpg]]

== About me/it ==

I started this build while in the UK, and three years later am riding it in New Zealand, where the roads are quieter and muh more Python friendly.

[[File:Jonny Python_hinge.jpg]]

== The frame ==

The rear of the frame is just the top tube of a kids mountain bike welded to some forks, but the front I welded up from 12mm steel tube, and later added the front "brace" (sea stays from another kids mountain bike) from the bottom bracket to the axle. I added this as a way of getting front brakes but mainly as the very front would twist when pedaling cauing the top tubes to rub on the tyre.

== The seat ==

The seat is plywood and came from an old dining chair that I bought at a charity shop for $2. I took off the fake leather covering and the legs, then I cut back and rounded the seat part.
[[File:Jonny Python_front.jpg]]

[[File:Jonny Python_front 2.jpg]]

[[File:Jonny Pythin_rear.jpg]]

== The ride ==

It's still a bit of a white knuckle ride on the road (I've only done about 8km though so far on the road after about 50 trips up and down the garden). I still don't have full control of it and am too scared to go very fast still.

More to come soon

MonsterbikeFWD

2012-03-04T10:33:08Z

Stevenurseau:

Hi, My name is Steve Nurse from Australia and I have been building a type of front wheel drive bike for about 6 years. The design is called the Monsterbike. I would like to see the design flourish and so have released a pdf plan of the bike, see [http://modularbikes.blogspot.com.au/2012/02/starting-monsterbike-open-source-hpv.html here]

Here are some design guidelines for a Monsterbike.

* Front wheel drive, fixed botton bracket, recumbent bike with 700c, 26" or 24" front wheel and 20"rear wheel. With a 700c wheel, the chainstays are parallel to the main frame as shown in the photo above, with a 26" or 24" wheel, the chainstays are parallel to the ground as shown in the plan.

* Sloping main frame tube at about 20 degrees to the ground. This geometry means that a hole for the steerer tube drilled at a simple right angle through the frame will provide the right geometry for bike stability using standard geometry bike forks. I can ride my bikes no hands but not while pedalling.

* The small back wheel allows a simple, large carrying capacity tailbox to be built onto the bike. The back wheel does not interfere with the tailbox at all, and the tailbox adds visibility, storage capacity and aerodynamics to the bike.

* The seat height is about 600mm allowing for good visibility in traffic and easy stops and starts. It allows sidesaddle trundling of the bike on footpaths. Its a simple flowing manoevre to pick up the bike to go over a curb or gutter.

* Direct front wheel drive, 8 speed derailleur gears with no pulleys guiding the chain. Gearboxes (Schlumpf & Sturmey Archer) have been used to add gearing range.

* The general ride quality relies on rear suspension. Having a large front wheel with good inate suspension characteristics a long way from the rider means front suspension is not required.

* On some of the bikes like the one shown above I use an inertia braking system, turning the brake handles toward the rider, and allowing the natural forward motion of the rider during decelleration to help activate the brakes. Also on the bike shown above there are 2 brakes on the front wheel - this simplifies the bike and also makes it easy to put a home made or other wheels disk on the back wheel. No rim braking required on the back so the rims can be covered by a wheel disk without fuss.

* These bikes work just like any fwd fixed bottom bracket design, that is, the chain comes from somewhere near the steering axis before it goes to the front wheel. So when the steering twists, the chain twists too, but doesn't actually displace much. Standard rear derailleurs mash up the chain in a horrible way during gearshifts, so this drive compromise doesn't worry the bike much. You can either have the chain quite close to the steering axis like some front wheel drive bikes with pulleys, or this [http://www.velovision.com/forum-new/read.php?5,8669 Bevo Bike] or limit the steering during pedalling in some way. I have trouser guards or outside catcher rings on the chainring and limit the steering during pedalling by having my knees inside the steering bars and it all works.

Look forward to your comments and especially bike builds.

--[[User:Stevenurseau|Stevenurseau]] 12:39, 3 March 2012
[[Image:tweed9.jpg|250px|thumb|left|Monsterbike Direct Drive FWD]]
[[Image:tweed10.jpg|250px|thumb|left|Newly completed Monsterbike on a shopping trip]]

FS24P

2011-11-23T03:09:32Z

DarkSilverR53: /* Links */

[[Image:FS24P01.JPG]]

{| border="1" cellspacing="0" cellpadding="5" align="left" class="prettytable"}
| [[Pivot Angle]] [°]
| [[Trail]] [cm]
| [[Seat Height]] [cm]
| [[BB-Seat Diff.]] [cm]
| [[Ground Clearance]] [cm]
| [[Wheelbase]] [cm]
| [[Weight]] [kg]
| [[BB-FWA]] [cm]
| [[BB-EOS]] [cm]
| [[Turning Circle]] [m]
| [[Front Tubing]] [mm]
| [[Wheel Size]] [inch]
| [[CG]] [%]
|-
| 60
| -22
| 36
| 10
| 13
| 117
| 16
| 30
| 48
| ~3
| MTB
| 24" 24"
| 48
|}

== Concept ==

Front suspension python for absorbing road bump, and reducing disturbance to steering (by foot).

== Design ==

Mountain bike front shocks are used basis of the front suspension. The chainstay is welded to the bottom of the shocks, while the pivot below the seat is connected to the top of the shocks.

== Build ==

The larger wheel turned out to be more difficult to deal with then the suspension. The seat ended up quite high to reduce [[BB-Seat Diff.]] and [[BB-EOS]] to accommodate shorter inseam, making the bike closer to a mid racer than a low racer. For the shock clearance, the legs have to spread a little bit thus reducing pedal reach. Very short cranks (140mm) was used, plus bringing the BB closer eventually...

== Testing ==

The original build [http://www.youtube.com/watch?v=liEgAoT_8eI (video)], got modified after several months of testing.

[[Image:FS24P02.JPG]]

[[BB-EOS]] length is shorted ~3in (4in tubing), to reduce pedal reach and to increase the knee clearance of the shock posts. Legs are more comfortable now. Reaching the pedal too far can put strain on the legs, despite having smaller wheelsize (24") than the [[FP02]] (26") [http://www.youtube.com/watch?v=ursy9LxXlqc (video)] Compared to the [[FP02]], seat height is 20cm less, but at 36cm, it still high relative to the survey. We'll see how it fairs in comfort vs. the FP02 over the next few months...

The pivot joint is reinforced, after it broke during testing, It's still the weakest point of the bike. Perhaps another round of reinforcement is in order...
[http://www.youtube.com/watch?v=SsK3sF1P-HQ The video] also includes some build details, the idler, fork modification for sprocket clearance, front frame, and rear frame...

== Links ==
[[User:DarkSilverR53|Vi]], [[Futon Express]], [[Bango]], [[Flintstones]], [[Micro Python|μPython]], [[Mini Python]], [[Guinea Pig]], [[Bipolar]], [[FP02]], [[FS24P]]

[[Category: Python Project]]

Stokid Python

2011-10-02T16:26:42Z

Babypython:

[[File:Stokidpython.jpg|300px|left]]

The stokid python uses the front part of the [[pythoon]] replacing the rear with a new module. Thus forming a tandem where the stoker position is sized for a child, hence the name "stokid" (stoker kid, see http://sheldonbrown.com/gloss_st-z.html#stokid).

More pictures can be seen at
[https://picasaweb.google.com/115289830560831073762/StokidPython?authuser=0&feat=directlink Picasa stokid python]
and there is a video on [http://youtu.be/Jovnjd0YVHo youtube]

=== The construction of the rear part ===

The bottom tube is a 40x40mm tube of 1.5mm thickness.

The chain stay, seat post and bottom bracket are taken from a mountain bike. The seat post is shortened down to accommodate the inseam of the child.

The top tubes and seat stays are taken from a mixte bike (http://sheldonbrown.com/gloss_m.html#mixte).

The steering tube of the stokid is a recycled seat post from some bike - the diameter matching the standard headset diameter of 1⅛ inch.

The rear frame as a whole is quite stiff, which is important for good handling of the bike.

Building this rear part went quite easy. Once the square bottom tube was brazed to the pivot and the rear triangle, the rest was just building up on that using the square tube as a base. I was finished in less than a week even though I have to mind a day job and am not a quick builder at all.

The cranks are shortened down to accomodate to 100mm. I used some [http://www.biltema.dk/da/Fritid/Cykler/Tilbehor/Kranksat1/ cheap cranks] to 100mm. The crank size of 100mm is a little less than 1/4 the inseam of the stokid, matching about the proportions of an adult inseam and adult cranks. These cranks come with a non removable single gear chainring. Such a chainring is wider than what would fit for a 8 gear chain, but the difference is only about 0.5mm which I grinded off.

The stokid drives the rear wheel using a 7-gear dérailleur, and he is able to follow at all speeds.

=== Maneuvering ===

I can best compare to the [[pythoon]] which is a long bike too.

The angle of the pivot on the stokid python is more shallow (57.5 instead of 60, togethyer with a slightlý shorter trail). This change has an effect that is immediately felt. For example the bike turns lighter (less self centering force to surmount), and this makes it easier to maneuver at low speeds.

I had my first accident right from the start: the CoG of the stokid is high, care must be taken when leaning into the curve at very low speeds. While with the [[pythoon]] it was possible to use leaning+acceleration to do a sharp turn when starting, I got nasty surprise trying to do the same with this bike: we fell over ---luckily no damage was done.

Because the pivot angle is slightly different from the [[pythoon]] I had to adapt to the slight different behaviour before I could start cleanly (=without a sway). In the beginning I had the tendency to over-steer when starting (front part swaying over to the left when starting with my right foot). After 100kms this is gone at the bike feels natural.

=== Riding at speed ===

We've been riding this bike in the last 2 weeks (about 100km together). Both of us are still learning.

There is interference with the steering when the stokid is pedaling. But either I am getting used to it or my son is riding smoother, because often I am unaware of this. I expect that after some time it won't be visible anymore.

When my son is not pedaling I have not noticed any [[Pedal/Steering_Interference|PSI]]. The bike rides like a train.

Without my son on the bike the tandem is more aerodynamic than the [[pythoon]]. Probably the box + child seat of the [[pythoon]] was a real drag.

=== Safety ===

Seen from the point of view of safety the [[pythoon]] is unbeatable. Even compared to other solutions the [[pythoon]] really shined: the bike is compact compared to an upright + trailer; the position of the passenger is really low; and even though the box was open he was very effectively protected by it.

The stokid python is not that safe for the stokid. And because of that I try to limit our speed just in case we would be involved in an accident.

Another reason to limit the speed is the need for braking. I have already been able to push the stokid forward out of his saddle just by braking strongly. He seems not to be strong enough to withstand the deceleration. Luckily the effect is that he falls down to the top-tubes instead of being flipped over.

Outside of Town our cruising speed is about 30kms (max has been 45kmh up to now). Though I limit the max speed, we are not that much slower than on the pythoon. Inside of Town speed is determined by outside factors so I can't really give any numbers.

The positive side of the stokid python is that we are much more visible: my son now wears a reflective vest and this works as a beacon for the cars.

=== Ergonomics ===

On the pythoon my son was always looking sideways into the landscape. Now his head sticks out up over my head, so he can overview the situation in front of the bike.

Our trips vary between 5 to 15kms single way. These are quite long rides for a 5 year old and he can feel it in his bottom and arms. Just the typical problems of an upright...

=== Conclusion ===

The main goal was to involve my son into the ride and that has been a real success. He loves riding this bike and is now very active with both his legs and mind. He often shows direction with his arms, or tells what way I could go. Or warns me about cars coming from behind. (he even tells me that he is taking a rest from pedaling ;-)). There is also a lot coordination going on. If he wants to slip his hands he has to tell me. Or when a bump is coming up I have to call out so he can brace himself.

All these things are missing when you put a child on a half-cycle. On a half cycle pulled by an upright the child can help pedalling, but is still just being pulled along.

On the down side: Controlling the stokid python is "advanced level" and I would only recommend it for those who already now how to ride a regular python well.

[[category: Python Project]]