[python] Re: pivot quality
- From: "25hz" <25hz@xxxxxxxxxx>
- To: <python@xxxxxxxxxxxxx>
- Date: Wed, 11 Apr 2007 21:55:22 -0700
For my first python, the BHP, I used sealed 12mm bearings very similar to
the ones Jurgen posted a picture of. They worked fine, were/are likely
massive overkill and after 2000km+ they were as smooth as when they were
installed. Hopefully they are still as smooth for the brave soul who bought
it :)
On the 2nd python of mine, the PC2, I used the "aircraft rods". They're
actually called (at least over here in North America) "rod ends" or "Heim
joints". Anyway, they were not high quality, super strong, or anything
else. They were just plain old farm grade, 1/2" rod ends that were about
$15 Cdn each that I bought at the local hardware store. I sued them because
they were so much easier to build for and I also wanted the pivot to be
adjustable so I could experiment with the pivot angle and find out what the
optimum angle was to make it easier to learn to ride.
http://fleettrikes.com/python%202%20pivot%20final.jpg
There was no machining, all the steel used was stock dimensions and the
pivot bolt is a plain old 1/2" NC Grade 5 bolt with a Nyloc nut. The plate
they bolt to is nothing more than a 1/4" thick piece of mild steel that is
1.5" wide and about 4.5" long. I dabbed a little 3 In One oil on the rod
ends every now and then for lubrication, just in case, cranked the pivot
bolt down good and tight, and that's it. It steers smooth as silk, but not
quite as freely as the sealed bearings. There was about 500km on it when a
guy came running up, asked a bunch of questions about it, and bought it on
the spot. In less than 30 minutes he had learned to balance it and was
riding short distances on it. I weigh around 98 to 100 kg, and there is no
hint of movement or play in those rod ends at all. They will likely last as
long as the bike, the selaed bearings or longer because there is no real
moving part to them like bearings. Even if they do fail, another $15 and
about 5 minutes replaces them. Keep in mind formula 1 race cars use 1/2"
rod ends for their suspension and steering (of course probably higher
quality). Racing go-carts that can go in excess of 120kph only use 3/8" and
5/16" rod ends for their linkages and steering. In my opinion and
experience so far, the rod ends work very well, are cheaper than bearings,
require much less custom fabrication and adaptation. If you want to use rod
ends, get inexpensive ones first. If they end up failing on you, it won't
be catastrophic, you'll probably start to feel a little play first and be
able to see that there is a problem. I think you will be fine with them for
quite a while and might not need to replace them at all, and then you will
have saved yourself a bunch of money. Maybe some of the other people who
used rod ends on their pythons have different experiences with them?
----- Original Message -----
From: "August" <augusthahn@xxxxxxxxxxxxx>
[python] Re: pivot qualityChecked out both sites and yes the auto bearings
look like they would work much better and as an added bonus they can be
bolted on instead of welded.I was thinking maybe ask a aircraft company
about stresses for those rods,they are control rods for alerons,as you have
them installed on your pyton allready you may as well test them for a few
hundred miles and check the results.
----- Original Message -----
From: Thomas P Jahn
To: python@xxxxxxxxxxxxx
Sent: Wednesday, April 11, 2007 12:54 AM
Subject: [python] Re: pivot quality
Hey August,
you name it. I was thinking of such a pivot using "aircraft rods". I just
didn't know, how they are called. :-)
The idea was to use two of them in order to have an adjustable pivot angle
without changing other aspects of the geometry. The lower bearing could be
fixed and the upper one should be movable forth and back.
www.aurorabearing.com/products/aerospace-military/aerospace-series/rod-ends/
male/default.html
I am a little in doubt though that 2 "aircraft rods" will give sufficient
strength/support. Therefore, I was thinking of using a ball bearing from a
cars front wheel suspension as the lower bearing. Those bearings are very
stable and carry 300 kg when the car is just standing still. The dynamic
forces must be much higher.
http://www.yatego.com/atv-schiffke/p,44c9c353c6afa,434630b1776d88_0,vw-traggelenk-vw
I think that should work.
cheers
Thomas
I was looking over various pivot designs on all the Phyton bikes and was
wondering about the aircraft type rods they look pretty simple to consruct
but.is there any info on how they work and hold up I relize aircraft spec
parts are extremly strong but they were never inteaded to be use as pivot
bearings under so much weight is that a proplem?
Jürgen Mages wrote:
> Hej Dirk,
>
> did you use these bearings:
>
> http://dirkb.dnsalias.net/image/python/skf_7201B.half.jpg
>
> As far as I remember, Eduardo from Brazil used the same
> type of angular contact ball bearings (Schrägkugellager).
>
> If so, these pivot types are left for the choice:
>
> - tapered roller bearings
> - rod end bearings
> - cartridge bottom bracket
>
> Could you please send us a photo of the destroyed bearings?
>
> Groetjes,
> Jürgen.
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