Rotary valves graphite bearings

Home Model Engine Machinist Forum

Help Support Home Model Engine Machinist Forum:

This site may earn a commission from merchant affiliate links, including eBay, Amazon, and others.

Drei

Well-Known Member
Joined
Feb 20, 2010
Messages
87
Reaction score
0
Im planning to use the rotary valves on my next engine but im worried about what type of bearings should i used because they will effect a number of factors:
the bearing should be self lubricated
accurate enough to achieve proper compression

I found this type of material that might be good for the application http://uk.rs-online.com/web/p/peek/2970147/. First question is that i thick it can be machined which i think it can. and does it wear quickly thus start loosing compression after few runs.

I also found these on ebay http://www.ebay.com/itm/New-12-18-2...ultDomain_0&hash=item43abd9d446#ht_1329wt_905. Are these better for my application or better from the other material.

As for the wear rate, should i incorporate a type of seal like an o ring etc to compensate for the wear thus reducing the compression loss. But i think that this is not possible due the high temperatures in the cylinder head. if one of these materials is used should i make small holes for lubrication.... and i was also thinking about ceramic bearings which are difficult to find and i think expensive. and as for the wear and tear, the shaft will take all the wear which preferably not thus avoiding the need to make new shafts. any ideas please..

the engine is a 100cc v8 which im planning to use rotary valves which will have separate heads to be able to insert 2 sleeve bearings on each inlet and outlet valve. then align the four head and fix them to the block. then engine will have medium usage thus wount have long and continues running and maybe short intervals of running.

thanks
Drei
 
Hi Drei

The PEEK is easily machinable with sharp tools, and actually very wear resistant, but does not work well with the higher temperatures that one would expect on an IC engine - it expands/shrinks quite a lot with temperature differences.

I'd say go for the graphite impregnated brass bushes for your use.

Kind regards, Arnold
 
Thanks for the advise I also thought that when i saw the 3% expansion rate on the spec sheet.
Drei
 
Back
Top