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Little Otto
Alyn Foundry:
Little Otto.
Back in 1873 Nicolaus August Otto had a patent granted for a Caloric engine. We now call this type of engine a Vacuum or flame gulper.
The working principle is very simple. At piston TDC a port is opened to allow a volume of heated air to be drawn into the cylinder. This heated air is furnished by the addition of either a flammable gas or liquid hydrocarbon. As the piston descends towards BDC the admission port is closed, sealing the cylinder. As the heated air is now enclosed within the water cooled cylinder it rapidly loses its heat and becomes much smaller in volume. The volume decreases so rapidly that a partial vacuum now exists within the cylinder. Now atmospheric pressure provides the force against the underside of the piston and draws it up towards TDC. Once the pressures have equalised and then slightly increased within the cylinder, an exhaust valve opens to purge the remaining spent air. Thus the cycle repeats over and over until the fuel supply is turned off. Because these engines rely on atmospheric pressure as the power source they weren’t very powerful, as the force is directly related to the piston cross sectional area. However they found uses for driving sewing machines, Dentist drills etc and required little to no experience with things mechanical to operate.
The engine in question, rumour has it that Otto used it to pioneer his now well known 4 stroke cycle. The engine was kept at the Deutz museum for a while before it vanished. Recently a group member sent me some photos and a video of a full scale replica that he was building, needless to say I fell in love with the design and a model was planned. I decided that the flywheel from my Robinson hot air engine would be just right for this project and was used to provide the datum for all the other dimensions needed for pattern making.
That’s all from me for now. I am trying to finish the model in time for the Neunen show next month where, I hope, it will join it’s full scale replica’s debut.
Special thanks to Wayne Grenning from who’s research work I have borrowed.
The bottom picture clearly shows the engine in question in the bottom left hand corner.
Alyn Foundry:
Otto used a couple of interesting features in his design.
The gaseous fuel was only supplied on demand by the use of a valve that was incorporated into the port slide. Just a small pilot flame remained lit.
The Scotch yoke gave a rapid down/induction stroke followed by a much slower return stroke.
Alyn Foundry:
I approached Jason several weeks ago with the idea of a model, his help previously providing the last remaining patterns for the Brayton Ready-Motor project was invaluable. The CNC process ensures high accuracy and near perfect results.
We used the Robinson hot air engine flywheel as a scale datum and Jason then used the picture to find all the rest of the measurements using his program. I had callipers, rule and calculator to make my patterns…. :lolb:
I will now had over the reins to Jason with an overwhelming debt of gratitude for his help in getting yet another of the great pioneers in the world of IC into model form.
:cheers: Graham.
Admiral_dk:
Getting the :popcorn: and :cheers: ready and thank you for the introduction on this historic engine :ThumbsUp:
Per
Jo:
--- Quote from: Alyn Foundry on May 20, 2022, 09:06:01 PM ---I will now had over the reins to Jason with an overwhelming debt of gratitude for his help in getting yet another of the great pioneers in the world of IC into model form.
--- End quote ---
We will have to wait for him to first finish the engine and gets his running before he posts the build ::)
Jo
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