Stuart no 6

A special section just for steam engines and boilers, as without these you may as well fit a sail.
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DetroiTug
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Re: Stuart no 6

Post by DetroiTug » Tue Sep 08, 2020 2:31 pm

On the Locomobile engines its simply a collar with a 1/16" roll pin above and below. Works great. Bottom pic was taken before the engine was rebuilt. The rods and collars are stainless steel now. Valve rod length adjustment is handled at the clevis on the Stephenson link. Added a Pic of a Mason engine rebuilt with new rods and collars.
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DetroiTug
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Re: Stuart no 6

Post by DetroiTug » Tue Sep 08, 2020 3:04 pm

Design consideration:

Note in the above two pics, how they used to do it. The valve rod is in a long slot and heels or pushes near the ends of the valve. This was probably to prevent the force from trying to rock the valve on it's ends and angular to the face as happens with heeling points near the valve center. A simple experiment to display this would be to slide a heavy object across the floor. Pushing on its top near its center and then move lower to it's nearest edge where it would be less likely tilt up and slide more easily. Not sure how important that is but it's something to consider.
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Re: Stuart no 6

Post by RNoe » Tue Sep 08, 2020 3:40 pm

Having rebuilt a locomobile engine last year, I have one more comment off the Stuart No. 6 topic:

Because the Locomobile engine sits vertically installed with the cylinders up, the valve chest can fill with condensate.
Our engine had a drain cock, but not at the gravitational bottom. The chest sat partially filled with condensate and corroded the
non-stainless steel rods quite badly. So after replacing the rods and valve retention collars with new stainless steel ones,
(we had to replace 18 of the 36 moving parts in this engine!)
we made an "extension" pipe from the drain cock that reaches downward to the bottom of the valve chest.

Now when securing the engine between operating sessions, we use compressed air to blow everything out, including
the valve chest, through that altered drain cock. I don't know if our engine represents most Locomobile engines built,
but it presented an issue that required a remedy.

The breaking valve rods on the Stuart No. 6 seem to be a similar engineering issue that some have solved.

Keep building, improving, and steaming
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Re: Stuart no 6

Post by DetroiTug » Tue Sep 08, 2020 4:41 pm

"Because the Locomobile engine sits vertically installed with the cylinders up, the valve chest can fill with condensate.''

Ive ran these engines extensively at pressure, temperature and speed, that hasn't been my experience. There is condensate at start up of course. Once the engine is up to temperature, any condensate is boiled and swept away. I've removed valve covers right after running, I've never observed any water. If the engines is warmed up and driven normally and then parked with the throttle left closed, there shouldn't be any water in the valve chest. If it's being ran on very low pressure temperature steam at slow speeds then there could be. The no 5 engine with the bands on the cylinders was designed to run at 250/406.

"Our engine had a drain cock, but not at the gravitational bottom.''

That is the 1/8" NPT in the valve cover most likely? That is for the displacement oiler only. Notice there are no cylinder drains neither. The engine is warmed through by slowly moving the vehicle forward and backwards a few times. The slide valve can lift off the face in the event of trapped water. I've flooded my boiler a few times and pushed water to the engine, there was only a slight bucking and some clatter from the valves which should obviously be avoided.

"we had to replace 18 of the 36 moving parts in this engine!''

Yes, they are a real experience to work on. for longevity ease of use, I replace the bicycle bearings with sealed ball bearings and make new eccentrics out of 330 bronze. the crankshaft, I just machine a new one. Those are well designed (by George Whitney) little engines, but the crank bearings are very poor, but thats what they had to work with.

Yeah, sorry for the OT
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