[python] Re: pivot maeasurements 2


On Tuesday, April 20, 2004, at 11:54 PM, Eduardo L P Jr wrote:

See some remarks inside of the text below...
 



Clear as a summer's day!

I think perhaps pic no 1 was intended to show the angular bearings instead of the linear ones. But in spite of that I now understand the whole pivot design a lot better. Thanks a lot, Eduardo!


olaf




 
----- Original Message -----
From: "olaf" <noll@xxxxxxxxx>
To: <python@xxxxxxxxxxxxx>
Sent: Tuesday, April 20, 2004 5:18 PM
Subject: [python] Re: pivot maeasurements 2

..................
>
> Did you do this only in order to be able to accommodate a bearing shell 
> of 40 mm height? Or does it also improve the strength of the welded 
> joint?
>
 
 
The chock washers was used to accomodate a 40 mm height shell. The reason wasn't the strenght. The tubes of the front frame are 20 x 30 mm.Welding 30 mm high wall in a 40 mm high bearing shell, leave a remaining portion of 5 mm to each side of the square tube. This is the area occupied by the welding sewing. If you use a 37 mm high shell, the welder must do the sewing in an area of 3.5 mm. A little tremble and the welding material invades the bearing seat, ruining all the work...
 

>
> I see. Do you think it would be in any way disadvantageous to put the 
> arms directly on the surface of the square tube? And subsequently make 
> the bearing shell a little shorter?
>
> The reason I ask is that I haven't decided if I will weld or braze the 
> python frame. If I choose brazing the arms must lie flat on the tubing 
> so capillary action can spread the filler metal beneath.
>
If you intend to braze, I think that you may lost 1.5 mm from each side without troubles.
 
 
>
>
> > Just remembering
> >
> > The "7" series bearings, have a correct side to mount !!!
>
>
> In an earlier mail you wrote:
>
>
> > Using two
> > bearings nose to nose, the couple will work with axial static loads of 
> > 498
> > kgf and axial dynamic loads of 882 kgf...
>
>
> Now I get confused! In your drawing the bearings are turned 'face to 
> face' and that surely seems to be the best arrangement in order to pick 
> up forces from any angle ...
 
See the diagram below (out of scale of course...)
 
<image.tiff>
 
 
As you may see, the inner ring of the bearing is a "cone" and in this type of assembly the pre-loading supplied by the fastening of the bolt and the nut forces the cones to pull the balls against the outer ring of the bearings. This is the same arrangement of the ball collars in the conventional headsets of the bicycles, isn't it? In the diagram below, I've designed the same shell, but with linear single row ball bearings. They don't deal very well with axial loads. When you fasten the nut + bolt, you may damage the balls and races.
 
<image.tiff>

 
>
> Hey, I really hope my questions aren't too stupid for you Eduardo – I 
> have no technical education and have to start this project from zero.
>
>
> olaf
 
 
There are no stupid questions in the world Olaf... I don't have technical education too. I'm a mathematician, but I lived many years in a farm (where my father lives even now...). I've learned to fix dozens of agriculturist machines on the work field. This was my "technical education"... The best lesson I've learned:
 
- "When a nut falls from your hands, you must pursue it with your eyes, because when it touches the ground between the grass leaves, it becomes imediately invisible..." (this is one of the articles of the Murphy's law)
 
 
All the best
 
Eduardo
 
Ypê Bike: http://www.ypebike.cjb.net/
Ypê Mono: http://www.ype.unicyclist.com/
 
 
 

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