The experts in our Hereford club advocate that an O ring should roll when in contact with a sliding surface. You have the make the groove large enough, so that the ring is not gripped. The groove should have a slightly bevelled edge as the ring wil try to leave the groove and you don't want to damage it. The ring should be slightly compressed, but not enough to trap it in the groove. The theory seems to be sound for water pumps and the like. Andy >----Original Message---- >From: clif.gwr@xxxxxxxxxxxx >Date: 21/11/2008 10:58 >To: <modeleng@xxxxxxxxxxxxx> >Subj: [modeleng] Re: O rings > >Hi All, > >I tend to use Viton O rings for steam and sliding joints, the only snag >being that untill I read Craig's e-mail I did not realise that there were >different types so perhaps I have been lucky. > Long before Martin Evans started specifing O rings for the steam pipe >joints at the front tube plate I had worked out that it was far easier to >make a compression joint using O rings than all the fun and games of trying >to screw a bush onto the steam pipe from the regulator while at the same >time screwing the bush into the front tube plate and get it all steam tight. >I also make compression joints for the steam and exhaust connections to the >steam chests. >I have never used Silicone O rings for sliding joints,despite the fact that >ME suppliers recommend them owing to the fact that the O ring manufacturers >say that Silicone cannot mechanical wear. Any comment please Craig? > >Regards > >Clif > > > >----- Original Message ----- >From: "Craig Gluyas" <craig@xxxxxxxxxxxxxxx> >To: <modeleng@xxxxxxxxxxxxx> >Sent: Friday, November 21, 2008 10:08 AM >Subject: [modeleng] Re: O rings > > >> As a former seal specialist for a valve manufacturer, i guess this is my >> area! >> >> O-rings are very suited to our uses, we just have to be careful what >> material to use. Silicone is about the best & most widely suitable for -15 >> to 200'C. Other materials vary, even to within blends. For example Viton A >> is not recommended for use with steam where as Viton B or Viton GF is. >> Viton is good for about the same temperatures as Silicone. >> >> Other seals such as EPDM and Nitrile are readily available, but are less >> tolerant to chemicals (Natural Rubber does not like Oils for example) >> >> An excellent compatibility website used in the industry is available here >> http://www.coleparmer.com/techinfo/ChemComp.asp >> >> >> Hope that helps! >> >> Craig >> >> >> >>> There is a discussion on a message board about the use of O rings in >>> model >>> steam engines. >>> Both the types and where they are, or are not, suitable, together with >>> the >>> advantages /disadvantages of them compared to other forms of seal. >>> >>> What opinions do members here have? >>> >>> Alan >>> >>> >>> >>> MODEL ENGINEERING DISCUSSION LIST. >>> >>> To UNSUBSCRIBE from this list, send a blank email to, >>> modeleng-request@xxxxxxxxxxxxx with the word "unsubscribe" in the subject >>> line. >>> >> >> >> MODEL ENGINEERING DISCUSSION LIST. >> >> To UNSUBSCRIBE from this list, send a blank email to, >> modeleng-request@xxxxxxxxxxxxx with the word "unsubscribe" in the subject >> line. > > >-------------------------------------------------------------------------------- > > > >No virus found in this incoming message. >Checked by AVG - http://www.avg.com >Version: 8.0.175 / Virus Database: 270.9.7/1799 - Release Date: 19/11/2008 >08:58 > >MODEL ENGINEERING DISCUSSION LIST. > >To UNSUBSCRIBE from this list, send a blank email to, >modeleng-request@xxxxxxxxxxxxx with the word "unsubscribe" in the subject line. > Money Saving Vouchers - http://www.tiscali.co.uk/shopping __________________________________________________________ MODEL ENGINEERING DISCUSSION LIST. To UNSUBSCRIBE from this list, send a blank email to, modeleng-request@xxxxxxxxxxxxx with the word "unsubscribe" in the subject line.