[python] Re: Thanks Chris! Any everyone else.
- From: Tihamer Juhasz <balamber@xxxxxxxxx>
- To: python@xxxxxxxxxxxxx
- Date: Wed, 3 Apr 2013 14:39:37 +0300
Hi Kelvin,
Great idea with the tie rods used for pivots. One more idea to make it
possibly better: instead of bolts in the hole of the tie rods you can use
these quick release bicycle thru-axles, see for example here:
http://www.amclassic.com/en/products/components/10mm-quick-release.php
They come in 10, 12, 15, 20 mm diameters so there should be a size which is
good for your tie rod, and breaking up the bike in two becomes more elegant
and quicker this way.
I am building my python now, and just made a pivot of a modified 1 1/8 inch
head tube. Will probably redo it with the tie rods because this is much
better especially for breaking up the bike. Thanks.
No riding experience with a python yet, just SWB recumbents, but no
suspension is better indeed (lighter, better power transmission) for road
use and foam cushion on the seat.
Regards, Tiha
On Wed, Apr 3, 2013 at 12:51 PM, Kelvin Arthur <kelvin.arthur@xxxxxxxxx>wrote:
> Hi Ivan
>
> Nice to have another Kiwi keen to do the python thing. I have built one
> here down under, it started out as something of a mongrel and was
> progressively modified over about a year to the final version for now.
>
> My thoughts, having read a lot on the web, built, and riden. Don't worry
> about suspension, if you're really concerned about a soft ride, build a
> textile seat (some sort of sling arrangement), this softens the ride no end
> without sacrificing too much in the power department. It is also easy to
> make and adjust. I built a curved wooden seat for a Bachetta clone, rear
> wheel drive recumbent recently, while a great seat, MUCH more work than the
> sling and it makes the position of it much more critical.
>
> As for pivots, I tried steering ball ends, complete disaster, I then went
> to a cup and cone bb, less of a disaster, still not very good. I then got
> 2, 12mm male tie rod ends and never looked back, easier to construct for,
> gives you about 2 degrees of angle adjustment each way and plenty strong
> enough. The final version of pythonui has an adjustable bb at the front
> for leg length, a sling seat, and even with a 3 metre wheel base (yes, it's
> a monster!) and my 4 year old boy in the back, I never had the feeling that
> the pivot wasn't up to the task. My python was transported by car a lot,
> being able to undo 2 bolts, and have the bike split was a real bonus, and
> allowed me to get it into my hatchback with ease, even the big version.
>
> On the gears front, my early version had a derailer, while functional, I
> never looked back after getting an in hub gear. It's only a shimano 3
> speed, but it's enough. Using an 8 speed hub gear with a coaster brake
> would have been a real dream for me, but I built with no budget, scrounging
> what I could.
>
> When you first build it, build it to be crashed, a LOT, it will save you
> the heartache of having to repair your lovely work!
>
> My few cents worth, and sorry for the novel.
>
> Kelvin (yes, it turns out it is a very small world after all!)
>
> Sent from my iPad
>
>
>
> On 3/04/2013, at 21:46, Patrick van Gompel <patrick_van_gompel@xxxxxxxxxxx>
> wrote:
>
> Hello,
>
> The option I use for an adjustable pivot point is a 'rod end joint'. You
> can see it here: http://cycle.free-creativity.com/images/python5.jpg The
> rod ends are protected by a rubber boot. The cheapest and best seller I
> have found is:
> http://mcgillmotorsports.co.uk/index.php?act=viewCat&catId=25 They have 3
> types, but I prefer the 'High Performance'.
> At the moment I use M12 size, which is strong enough, but for my next
> project I am going for M14 as I am building a utility trike and needs to be
> very strong.
> Not sure how many degrees I can adjust the pivot, but it depends on your
> design (the distance between the two rod ends and the size of them). If you
> need detailed info about those rod ends, like thread length or max. angle;
> it's available (just ask).
> Though, you can't adjust the pivot 'on the go'. You need to detach the
> front and rear part and use shims to fit the rod ends on the pivot axle
> without play.
>
> Ivan, I don't think you need suspension. Of course, my big apple 26" tires
> are more comfortable than racing tires, but it is like you compare a ride
> on a mountainbike with fat tires to that of a racing bike, I think. My
> experience with recumbents in general is that a nice seat with a good
> cushion does also give you a more comfy ride.
>
> Greetings,
> Patrick
>
> ------------------------------
> Date: Wed, 3 Apr 2013 10:53:21 +0300
> Subject: [python] Re: Thanks Chris! Any everyone else.
> From: balamber@xxxxxxxxx
> To: python@xxxxxxxxxxxxx
>
> Hi Ivan,
>
> A working adjustable pivot is technically very difficult to do in my
> opinion. I tried to build a test bike with an adjustable pivot to test
> different bike geometries but it tended to buckle all the time. I would
> suggest that if you really need to change the bicycle geometry, instead of
> an adjustable pivot add front and/or back suspensions with a pretty large
> range of adjustment and use them to raise/lower the front and rear of the
> bike. This way you change the pivot angle as well.
> If anyone has a good idea/mechanism of an adjustable pivot with a +/- 15
> degrees of range or even more please share it. Infinitely
> adjustable/stepless adjustment preferred.
>
> That's my two cents.
>
> Tiha
>
>
> On Wed, Apr 3, 2013 at 10:09 AM, Ivan van Hoof <zl3tiv@xxxxxxxxx> wrote:
>
> That sounds like one nice seat! Bending ply or snake ply, I will have to
> make my seat out that stuff. Any thoughts on the main pivot? I like the
> simple bottom crank design but I want a design that is simple looking,
> sleek and adjustable angle by a few degrees to account for other riders
> weights and lengths. Good to see the group is active, very quick replies
> from you guys is great!
> I have shown, told a few work mate and friends the web site and they are
> keen to see me finish my python and ride it.( and a few think am crazy.)
> How smooth is the ride of these bike with 700c or 26 inch wheel on the
> road( no off road) would I need suspension? I intend to only use the bike
> for touring on the road. I'm thinking no suspension to save weight.
> Thanks guys for your help.
>
> Ivan van Hoof
> ZL3TIV
>
> Sent from my
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