Stuart 5a stationay build

[Bob Sorenson]

Hi GreenTwin. Thanks.


Time to start final assembly. First take everything apart and clean in acetone. Mask and paint. This #5a is in gloss black. Stuart traditionally uses an olive drab green for the upper part of the engine and black for the base. I think gloss black looks great. Start assembly.

For gaskets, I used heavy paper soaked in steam oil. Our son has a 10-watt laser attachment for his 3d printer. I drew up the gaskets in FreeCad and had him cut them out with the laser. They came out perfect. They look like scissor cut.

I am horrible at sheet metal work. As for cylinder cladding – just get it done. Since the eccentrics are keyed to the shaft there is no adjustment. They either work or they don’t.

The plan for the valve rod fork is totally wrong. Making the fork according to the plan will bind and foul the radius link. There is no way to fix it, just make another. Add a full 1/8”.

The valve is set on the valve spindle by a pair of opposing jam nuts. The photo below shows a length of thread on the bottom portion of the valve rod and none at the top. The top jam nuts are fully engaged, just can’t see any thread. The valve spindle is the correct overall length, but it may be a good idea to shift the threaded portion up about 1/8”

Next time is the finish up and air test.





Take care, Bob

 

[Steamchick]

Excellent work, Bob. Keep it up!
K2

 

[GreenTwin]

Nice work on the link.
.

 

[Bob Sorenson]

Thank fellas.


Well, this is it. Last of the assembly. Get this 5a running on air today. The plan does not specifically show a locking nut for the shifter arm. There is one part on the plan that did not have a clear purpose. Maybe it was the locking nut, I just could not figure out how it worked. Anyway, this locking nut requires square ends on the drop arm.

There is a bracket attached to the valve chest that holds a pivot. Like the rest of these parts, it’s a brass and silver solder fabrication. The shifter arm and bell crank arm (I don’t know what these parts are called) are fixed with tapered pins. The pins are size 5/0. One pin is drilled, and hand reamed in place. For the second pin, tap 2 x 56 for adjustment. Use a sharped 2 x 56 machine screw for adjustment. Once everything is in place, sinch the screw tightly to leave a witness mark on the pivoting pin. Drill thru and hand ream. Everything fell in place on the first try.

And here’s the prom photo.

Set up for an air test. Oil everything up and let it go. It runs good on about 12 PSI. Runs great on 20 PSI. It screams at 30 PSI.











That’s going to wrap it up for now. The engine needs some better cylinder drains, a mechanical lubricator and a 4-line gravity feed oiler for the standard and main bearings. That will come along in a bit. Going to add the three more features suggested by a friend: drain on the valve chest, a flat on the valve spindle and a threaded plug on the top cylinder cover.





Thinking about putting this engine on a two-seat go-kart. Wood frame, metal frame gussets, spoked bicycle type wheels. Make it look really old school. My wife can steer, I’ll run the boiler and engine. In these parts everyone drives ATV’s all over, don’t think the sheriff will mind a steamer.





I want to thank everyone who checked in and commented during the build. Thanks again. The next stationary is a Stuart Beam, that will probably start in the fall.



Take care, Bob

 

[krypto]

Great build article and a lovely engine!

 

[Steamchick]

A big "WELL DONE!". Some "non-Stuart" (Proper) engineering has been applied in the build too. Which I like!
K2

 

[Bob Sorenson]

Thanks fellas. Trying to figure out a boiler for this. At least some kind of test boiler.

vr bs

 

[packrat]

Your a very good machinist, the 5A is a nice size engine. Well done.

 

[ScottP]

Thanks fellas. Trying to figure out a boiler for this. At least some kind of test boiler.

vr bs

Martin Evans drew up a vertical boiler suitable for the Stuart 5A in Model Engineer magazine - 21 November 1975 issue.

Plan M30

https://www.sarikhobbies.com/product/vertical-multi-tube-boiler-m30/

Might be a reasonable place to start...
Regards,
Scott

 

[Bob Sorenson]

Thanks Scott. The plan is on order.