Engines > Restoration of Model Engines

Reconditioning a Stuart Simplex

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This will be my 3rd Stuart restoration project, but this ones a keeper........ it's bruised, it's battered and in need of love and attention, however, I may not be able to do it justice atm without workshop facilities........let's see

I never realised how small one of these simplex engines was until it arrived; very cute. It turns over smoothly and I can feel sucking and blowing which is a good sign, but clearly has several issues which need to be addressed

The engine was mounted in order to power a boat, hence the angle. I took it off the base to understand what is out of alignment; just about everything is the answer!  ;D

1. Valve chest cover is larger than valve chest
2. Valve chest top slopes downward from cylinder
3. Valve chest sides taper inwards towards valve chest cover
4. Cylinder base cover/mount looks like someone has gone crazy with a file
5. Eccentric has no bolts appearing from the bottom
6. Small hole in the cylinder base cover/mount
7. Solder between the cylinder and valve chest underneath
7. The inlet valve has been soldered in an 'interesting' way to the valve chest cover

I don't want to replace/correct everything which isn't right - it'll end up being a different engine, so I'm thinking of:

- Making a new valve chest cover which fits the valve chest (maybe a problem as the studs probably go all the way back into the cylinder)
- Maybe a new valve chest if the holes are too misaligned
- Maybe having the inlet coming through the side or top of the valve chest
- Replacing the cylinder bolts with studs/nuts
- Tidying up the Cylinder base cover/mount
- Bolts/studs for the eccentric
- Lagging around the cylinder
- Strip down, cleanup and repaint

Also, is there anyone out there who knows about these little engines:

- Why is it called a Simplex? When I Googled it I got back Simplex Locomotives? What's the connection, if any?
- I'm not sure what sort of lubricator is on it, but I kinda like it  :)
- From what I have read and from the type of crosshead guide this is an earlier model?
- If this came only as a kit or complete what has happened to the poor thing over the last 100 years!
- Slim chance, given the point above, has anyone got a diagram/ drawing?

Looks like quite a bit has been soldered together in an attempt to seal uneven surfaces and also the problem of holes coming out the side of the valve chest. May even be due to stripped out threads so it can't be screwed together.

Chest cover looks a different colour so possibly replaced with brass at some time, the boss being soldered on suggests the person did not have  a lathe and just soldered on what they had.

It is an early version without the trunk guide but not sure if the round rod came before or after the flat guide. Not seen one with the mounting lugs on the sole plate, they all seem to have holes passing right through

I looked at a lot when I built my replica but was not able to find a drawing, I'll did out some photos with sizes on them.

Thanks Jason, most appreciated.

I think you're right about the valve chest and I'm now thinking about undertaking a more comprehensive rebuild when I have my workshop back. I think the solder between the valve chest and cylinder has been place there as the stud has come through at the incorrect angle into the cylinder ....... I will check when dismantling

I have been told the AJ Reeves Trojan engine designed by Edgar Westbury is a close relation (see picture). I've done a quick measure up and think I could use the steam chest and cover from this engine and machine it to size. I will have to either fill the existing holes in the cylinder or make some new ones in a different position

A pretty little engine,
on the second picture, the steam chest looks to be too small in height, and alas the top of the cylinder has been filed to cope, this sloping side would require to be amended either by adding metal or resurfacing the top of the cylinder if the top of the piston allows.

I hope that putting all the parts apart will not be too difficult owing to the bruised screw slots, and the soft solder in many places.

And the tap on the steam chest cover should not be after the oiler, but before.


I agree with your assessment and the tap is definitley in the wrong place.

Regarding the sloping of the cylinder, the adding metal option is my current thinking. I would first make and fit a new steam chest and cover, the gap could then be seen and filled accordingly.

Its difficult to work out what to do and what to leave when restoring an engine of this age. I want to make it look good, function correctly, but without creating a 'Frankenstein' engine?  ;D


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