A couple of engines for GreenTwin

[Jasonb]

I know Greentwin has said he does not like making small engines and when I saw these yesterday on the Stuart stand I thought of him, start saving now💲💲💲💲 About a 14" flywheel

Also a double size Otto on another stand

 

[GreenTwin]

LOL, das what i'm talkin about !!
Big ole working-class engines, and you can get a free workout carrying them into the show, without even going to the gym.

I really like the larger models, and the machining work is so much more forgiving.
When I try to machine tiny parts, it seems like I can blink and ruin a part.

The advent of the larger format 3D printers like the Prusa XL is helping a lot with these grand-scale engines.

Very nice engines indeed !

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[Jasonb]

I thought the opposite. Simply scaling up the very basic 10 V & H designs does not really work you end up with a chunky and clumsy engine. For example they still have the "extruded" profile bearings and simple one piece eccentric strap. At the very least on an engine of that size you want split bearings and a split eccentric with more than the end of a screw running in a slot to locate it sideways. Modern BZP nuts don't do it any favors either.

In this case big is not beautiful, at least in my eyes

 

[GreenTwin]

Myers had some nice sized engines and castings at the 2019 NAMES show.
Some significantly larger than I would attempt, but most impressive castings.

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[GreenTwin]

I thought the opposite. Simply scaling up the very basic 10 V & H designs does not really work you end up with a chunky and clumsy engine. For example they still have the "extruded" profile bearings and simple one piece eccentric strap. At the very least on an engine of that size you want split bearings and a split eccentric with more than the end of a screw running in a slot to locate it sideways. Modern BZP nuts don't do it any favors either.

In this case big is not beautiful, at least in my eyes

They took a few shortcuts, but I will forgive them, since they made the effort, and made the engines.
3D printing of patterns could easily add the find detail back into their design.

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[GreenTwin]

I like machining hardware (nuts and bolts) that are large enough to easily see and feel, like this one.

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[GreenTwin]

You can get into some pretty chunky risers when making larger castings.
A large enough casting could require either a large crucible, or a double-pour.
Quite a bit of metal is required in addition to the casting itself.

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[Jasonb]

The difference is that the large Myers offerings look right. That is due to them having been scaled down from real full size engines. The Stuarts have been scaled up from small freelance engines were originally designed for ease of casting and machining.

I'm almost certain those large Stuarts were from 3D printed patterns. It is not the type of pattern that will "easily add back detail". That stems from whoever is doing the enlarging be it with pen, paper and wood or a Cad package then 3D printing etc

A double size Stuart No1 would have come out around the same size and not looked so bad but I suppose saying it is a 5 times No10 sounds more impressive than a 2 times No1

Given the basic bed, frame, cylinder and valve chest castings a sympathetic build could be done that looked a lot more appropriate for the size of castings.

 

[GreenTwin]

With 3D modeling and 3D printing, there is no reason to lose any detail, from say scaling down the O-S shown below.
It is not very hard to just model it exactly like it is built.

In this day and age, I am excited to see anyone doing any type of modeling.

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