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Author Topic: New M91, running in its new stand.  (Read 100 times)

Adirondack Jack

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New M91, running in its new stand.
« on: August 24, 2020, 03:59:49 pm »
The M91 is a fascinating engine to watch run. It’s also a bit of a hoppy little hot mess when run on the original battery box/stand. Don’t take your eyes off it or let go of the stand.
There really is nothing wrong with the stand. It just needed to be longer, lower, wider, and heavier.
So a piece of clear hard maple 3/4 x 3 1/2 inches, a bit longer, with the engine centered on top a smaller block of the same maple. The blocks were both hollowed out under the engine, to conceal the electrics, and the main piece is hollowed to create a battery box on one end. The battery box has a plywood collar and lid, allowing top side battery access. It is pinned in place with two tapered pins. 
The extra space under the ignition module is filled with steel BBs potted in wood glue for ballast.
The whole affair sits on four tiny stick-on silicone dot feet. As the video shows, even running on a lightweight folding tray table, it no longer hops, and with the engine mounted near the center of the stand and lower, has less ability to even try.  It’s still running a little fast, original governor springs, but progress has been made.

Adirondack Jack

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Re: New M91, running in its new stand.
« Reply #1 on: August 24, 2020, 05:32:29 pm »
Meant to add a pic of the stand without the engine.
As you can see, I tried to minimize both the battery box and ignition compartment. The maple base and motor mount were hollowed out using a scroll saw. 1/8 inch birch ply was used as compartment bottoms, and The battery box lid. The space available under the ignition module filled with BBs potted in glue added a bit more ballast. Centering the engine on the mount, and lowering the center of mass help with stability also.


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Re: New M91, running in its new stand.
« Reply #2 on: August 25, 2020, 01:25:34 am »
Nice job Jack! 

Steam Technology

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Re: New M91, running in its new stand.
« Reply #3 on: August 25, 2020, 04:53:24 pm »
Your new base looks heaps better than the pencil case it came with.
Cheers. Dave.


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