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[bogstandard]

Can anyone explain to me either thru text or pictures how piston porting works.
The reason is that I want to design and build an engine for model boat use that is easy to reverse using a simple porting switch rather than all the linkages that have to be used with a slide valve, and thus can be run using only one servo.
I have no problems with the eccentrics, just the way the valve area works.

[HS93 (RIP)]

http://mokei-jouki.hp.infoseek.co.jp/eW-pvalve.htm

this site is verry good I have been folowing it for a few years , I think the way the piston works is that if you move the piston TUBE you alter the timing , giving reverse.

http://mokei-jouki.hp.infoseek.co.jp/e-Wiltop.htm


http://www.modelsteamenginesuk.com/model_steam_engines_avon.asp#specifications

JOHN HEMMENS did a piston valve engine, if you can get a look at one

It seems the way to go I have a protius and its a pain to set up reverse, and there is so much exxtra work , The avon looks a nice engine and from what I have heard works verry well

Peter

[Aussie Bruce]

Hi Mate

Sent an email to you 

Enjoy

If you need more sing out

Just to advise people that model engineer ran a series of articles on Borderer a engine that could be built in many options piston ported or link motion and in different bore and stroke versions ie 1/2 to 5/8 bore and 1/4 to 5/8 stroke you choose

The series also then went on to desribe a smaller version called Marcher this version is 7/16 bore etc and can be built in two versions link motion and piston ported

If people refer to my post in the steam section of my Borderer Donk you will see elements of both these designs in my engine

The series ran from 1 st Dec 1989 to 18th October 1991 you should be able to get hold of them in the uk

Castings etc are available from Reeves but as can be seen from my example i have not used one casting.

The easiest wayto desribe piston porting is to think of a round hydraulic spool valve taking the place of the flat D valve thats all as to the steam switching valve all it does is send steam to the exhaust port or the inlet port of course this will only work on double acting engines

Just a note most wilesco steam engines are piston port

[bogstandard]

Peter,
Thanks for the links, explained a lot.

Bruce,
Seeing your build has explained a lot.
I think I will try to keep the same bore and stroke as my twin oscillator build (which is just coming to the end), that way I can use a lot of the same design of parts. Does your Borderer use any form of piston rings?


John

[Aussie Bruce]

No mate no rings for me, not even o rings they are to fiddly all i use is a length of Teflon packing that i got from the local engineering shop years ago it was a piece of 1/2 inch gland packing cost a few dollars thats all and de laced it to 1/16 or less strings

I find it nips well and does not leak and lubricates up the shaft really well

By the way there is still a heap of it left

[bogstandard]

Thanks very much for the info, will be starting to design in the next few weeks.