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Geared horizontal twin engine

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Steamchick

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Final "Congratulations" on a splendid model, showing an alternative arrangement for the power and valve gear train. A really splendid tutorial.
Thankyou Brian.
 

Steamchick

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Steam,
Could you clarify your first point? The others I get but the first is, unclear?
Hi Richard,
Just spotted this comment and I missed it previously so here is my reply. - sorry for the delay. (But I don't know how to explain it clearly!).
Brian's design has the cap of the cap-screw at the outer-end of the eccentric rod bearing cap, with the thread tapped in the half that also has the rod connected. I have seen alternatives on Motor-cycle engine cramkchafts, where the head of the big-end bolts are on the "piston-side" of the con-rod, with nuts on the "outer-shell" side of the big-end. So would it make any difference to the engine if Brian had taken his cap-screws from the Rod-side through to the "eccentric strap outer half" - with threads tapped in the eccentic outer strap side? Of course "the workshop" would profess it is easier to assemble his way, but in theoretical design it may be better the other way. Because "I don't know" I was asking if Brian had any reason for one way or the other? As it is a bench model, I am sure it doesn't matter, so the easy assembly arrangement is preferred. But on a "real" engine, there can be mass/balance issues, stress issues, material savings issues, and a whole host of things that Design Engineers learn to consider - and I find I have learned certain things that are contrary to how others do it - and often just because I just don't know "Why" best practice is "best"?
So if you have any advice I'll be glad to hear it. I didn't spend all my career in Design, just a small fraction of it, as after 7 years in Design in a few jobs I went chasing more money in a car factory, and after 6 years in engine design the department I was working in went 200 miles away, so I stayed and moved to QA - for 26 years! So I realise I am not the most experienced or knowledgable design or manufacturing engineer on this website. Now in retirement I am enjoying the design and manufacturing stuff of this site. - I learn something new most days.
One word of wisdom that I remember from Mr Honda, founder and owner of the Motorcycle manaufacturer: When asked "why is this bike 2 cylinders instead of 4 - like the previous version in this size? - Is there a design advantage - or something?" - He replied that "Honda can design any size of configuration to their high standards, but this 2 cylinder design was what the marketing people thought would sell more bikes. Both designs have merits - but changing the design would promote more sales, even if a small number of customers were lost because of the change - and profitability would increase"... And he was right. The press and market loved the "new" twin cylinder... So the "best engineered" design was irrelevant - the "highest profitability design" was considered the "best".
So Brian's reason for designing the eccentric strap may be for any one of many reasons. In his reply he said "The advantage of having the bolts set up the way I do is that the heads end up resting against a flat surface. " = post #84. - That's good enough for me. It makes my question irrelevant.
Thanks,
K2
 

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