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21st century Stuart Simplex

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JasonB31/12/2021 16:27:04
22560 forum posts
2634 photos
1 articles

Just time to squeeze another little one in before the end of the year :cartwheel:, these small pond boat engines are getting quite addictive :-[

This time the subject is the Stuart Simplex which was produced from 1924 to 1928 and only available as a machined kit of parts or complete engine so no drawings were ever made available. I went with the "New Simplex" which was introduced in 1926 which can be recognised most easily by the trunk guide, the earlier engines having various forms of bar guide for the cross head.

I managed to find a few images on the net and was lucky enough to be given a few main dimensions by someone on the Stuart Models Steam Engines Facebook Group so armed with those a few evenings spent with Alibre had a working design. As per the previous engines I updated to metric but kept the size approx the same so the 5/8" bore x 5/8" stroke became 16mm x 16mm

Looking back at the dates on my photos I started this one on the 17th Dec and got it running yesterday just in time for a quick strip and paint so it could be assembled and videoed today. I did make use of the CNC on a few parts but with only minor alterations to one of them all could be done on manual machines. There are quite a few parts even though it is not that big an engine and some do get a bit fiddly to handle but at least it does not take up too much shelf space <img src=" src="" title="Wink" />

And when they are all put together it comes out like this.

I was happy that it started straight away as soon as the air was connected after a quick sideways knock to get the valve to sit down on the port face and just needed a slight reposition of the eccentric to get it running cleanly and faster. Most of the footage in the video was with the compressor regulator reading 5-6psi and as you will see towards the end of the video it runs quite slowly for what is a "high speed" engine. Though with the regulator opened up a bit to 20psi it was happy spinning over at 1800rpm as you will see if you watch to the end.

Former Member31/12/2021 16:36:06
1085 forum posts

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