Author Topic: Benson inverted steam engine  (Read 2131 times)

Offline BobJohn

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Re: Benson inverted steam engine
« Reply #30 on: July 09, 2021, 12:16:00 PM »
Very nice work, the brass is spectacular. The Benson is already a small engine, scaling it down has to be quite a challenge.

I've just started a Benson Vertical a few weeks ago. However, I've scaled it up X1.6. I'll use aluminum castings from my backyard foundry. It's proving to be a really fun project. I think speeding up the governor is a good idea, I'll try to do the same. I'm in the process of casting the entablature now, I may move the governor mounting hole to make it easier to add a different gear ratio.

I'd be interested in how the piston rod bracket/bushing part of the project goes. It looks like it could be an alignment challenge.

When I get a bit further along I'll share a few pictures.

Bob

Offline gbritnell

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Re: Benson inverted steam engine
« Reply #31 on: July 09, 2021, 08:13:09 PM »
Hi Bob,
I had the same concerns about the alignment of the piston rod support bracket so I made up the bracket without the bushing. I assembled the cylinder/piston/rod in place then soldered the bushing to the bracket. If you're making the whole thing out of aluminum you could maybe make the part of the bracket that extends from the column as one piece then make the arm the goes back to the centerline as another. You could then screw the 2 pieces together and file and adjust as needed for alignment.
gbritnell
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Offline BobJohn

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Re: Benson inverted steam engine
« Reply #32 on: July 10, 2021, 03:42:40 PM »
Good tip, when I get that far I'll see if brass is an option.

I like cutting gears, but helical are a bit much for me. I've looked at SDP and they have a 48DP 20T and 35T that would would put the PD at .7365 and a speed up of 1.75:1. The current dimension on the entablature of the crankshaft and governor shaft is .712. Shouldn't be that much of a change to the pattern. Though I haven't check pricing.

Working on a pattern for the cylinder today. Hope to make it so I can use wood lagging. Should be able to attempt a casting next week some time. If successful, I'll have four parts. I'll post a couple pictures.

Bob
« Last Edit: July 10, 2021, 05:46:22 PM by BobJohn »

Offline BobJohn

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Re: Benson inverted steam engine
« Reply #33 on: July 19, 2021, 07:44:18 PM »
I have four parts now, so I figure I can include a picture or two. The engine will be 1.6 times the original.


Offline gbritnell

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Re: Benson inverted steam engine
« Reply #34 on: July 19, 2021, 08:09:09 PM »
Great looking castings! I'll be following along for sure.
Talent unshared is talent wasted.

Offline BobJohn

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Re: Benson inverted steam engine
« Reply #35 on: July 19, 2021, 09:33:26 PM »
Thanks George. Casting is great fun.

I thought I'd cast the pump body in brass. But, when I looked at the drawings, I had a hard time trying to figure what the plan would be for the pump intake. It looks like it just goes down into the base. Do you have any ideas for your engine?

The author said he added the pump so the engine would have work to do.

Offline gbritnell

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Re: Benson inverted steam engine
« Reply #36 on: July 20, 2021, 11:45:23 AM »
Being as I had no intention of using it I just made it like the drawing and it protrudes through the base.
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Offline Jasonb

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Re: Benson inverted steam engine
« Reply #37 on: July 20, 2021, 01:01:22 PM »
Castings look Good

The layout of the pump as it is shown best suits decorative use where the outlet can pump through an open spout into a tank or barrel with a pipe from the bottom of the container back to the pump hidden in side a wooden plinth, the circulating water is just for show.

If you wanted to use it as a boiler feed pump then a bit of reconfiguring to allow for a side inlet that is above the cast base would be more practical.

I just built mine as a dummy and don't think I even added any gland packing or balls, all helps to reduce friction and get a nice slow running display model.