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| What's the design theory behind knife edges? http://www.international2cvfriends.com/forum/viewtopic.php?f=7&t=1515 |
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| Author: | samfieldhouse [ March 25th, 2010, 1:46 am ] |
| Post subject: | What's the design theory behind knife edges? |
Having services and greased the knife edges at the weekend I started thinking about their design. Why are they like that, and what's with the shape? Would a circular design not have been better, or is the tear drop shape designed to have as little surface area on the 'rubbing' edge as possible? Attachment: Suspension knife edge pivot pin, rear, 43mm x 14mm.jpeg And how come ecas list two different sizes? Finally, how much wear is too much on the end eyes? My rear left has started to show minor notching, probably 2 mm, if that. At what point do you replace them? Attachment: Suspension tie rod end eye.jpeg |
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| Author: | Tom Duckpower [ March 25th, 2010, 9:20 am ] |
| Post subject: | Re: What's the design theory behind knife edges? |
samfieldhouse wrote: And how come ecas list two different sizes? front and rear are different in diameter.. |
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| Author: | Sean [ March 25th, 2010, 9:41 am ] |
| Post subject: | Re: What's the design theory behind knife edges? |
We covered this over on 2cvgb ...at length when people decide that bronze, ball and nylon ball joints are better in theory. The knife edge is a very effective way of reducing and eliminating sliding friction between the highly loaded components In service the knife edge rocks in the eye bolt there is little damaging sliding between the two faces the knife edge is or was standard einginering practice when loads and reduced friction were needed, most commonly seen in weighing scales. Citroen components allowed for quick and easy replacement of the worn parts Most of the wear comes from fretting corrosion and the regular greasing is more of a protective covering rather than a lube as the forces concentrated on the small contact area would almost instantly break down any lubricating film As with much on the 2cv, the design may seem crude and agricultural by the standard of today but the more you look at it its always verging on the genius there is little you can do to improve it. Truly designed by artisan eingineers Sean |
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| Author: | Russell [ March 25th, 2010, 8:03 pm ] |
| Post subject: | Re: What's the design theory behind knife edges? |
The best way i was taught to understand it is to think of the point like the fulcrum of a set of scales, the shackle merely rocks on the knife edge. as sean says, nothing wrong with what Citroen fitted, yeah, they wear, but they aren't expensive. |
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