Resources/Information for Crank Lubrication?

A special section just for steam engines and boilers, as without these you may as well fit a sail.
Lionel Connell
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Re: Resources/Information for Crank Lubrication?

Post by Lionel Connell » Thu Mar 15, 2018 6:27 am

CAD model of my 6A

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Re: Resources/Information for Crank Lubrication?

Post by TriangleTom » Thu Mar 15, 2018 6:31 am

Thanks for that Lionel! It explains a lot.
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Re: Resources/Information for Crank Lubrication?

Post by Lopez Mike » Thu Mar 15, 2018 6:36 am

Well, if you can pull it off it will surely be a museum piece.

Backing off and looking at the overall scene, are you sure you are not designing a complicated condenser? I'm not at all prepared to cough up any numerical analysis but it sure seems like the ratio of surface area to volume in that small of an engine might be just as efficient in a two cylinder compound.

But I'm making assumptions that your reason for building a quad is efficiency. I can certainly understand and applaud other motives.

It will certainly be a sight to see.

As to how I align the pressed together cranks, yes. I set up the assembled crank between some robust centers with a dial indicator and keep giving it strategic whacks. I am able too get a crank within less than .001" runout. Not rocket science at all.

I have repeatedly assembled three cylinder, six main bearing 750 cc racing I.C. engines that run up to 9000 r.p.m. with no failures due to the crank shifting. Barbaric, I know. But it works very well.
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Re: Resources/Information for Crank Lubrication?

Post by TriangleTom » Thu Mar 15, 2018 6:45 am

You're right that the quad is for efficiency, but it's a strange engine to think about. Essentially it's a small superheated HP engine that exhausts at 120 PSI and a large superheated LP engine that exhausts around 5 PSI. Based on the math I've done so far, there won't be any condensation in the HP and LIP cylinders, so I'm hoping it's more than a complex condenser.

The other reason I'm doing a quad is because I like the challenge, and I've had a fun time designing it so far.

Unrelated, but why 6 bearings instead of four on a 3-cylinder?
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Lopez Mike
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Re: Resources/Information for Crank Lubrication?

Post by Lopez Mike » Thu Mar 15, 2018 6:54 am

These were 2 stroke engines. Essentially three separate 250 cc engines with one crank. Early seventies G.P. bikes. Total beasts.

I was thinking less of any internal condensation than the problem of it having a disadvantageous ratio of volume to surface area on small cylinders in general. Sort of the old problem of why a mouse needs to eat all the time while a cow can live out in the rain and not get hypothermic.

Bigger cylinders will always radiate less energy away for a given volume.

I hope you build it and post videos of it running at low speeds. I am as susceptible to engine hypnosis as anyone. Wait a minute! you are going to hide all of this? Booo!
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Re: Resources/Information for Crank Lubrication?

Post by TriangleTom » Thu Mar 15, 2018 7:02 am

I see what you mean now regarding the SA/V ratio. I'm actually planning on tapping the reheated line for a steam jacket around the HP cylinder so that heat actually flows inwards, but like I said the math isn't done yet.

When I eventually do get it built, I'll be certain to post it everywhere. And the enclosure is going to be lexan, so the interesting bits will still be visible.
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Re: Resources/Information for Crank Lubrication?

Post by Lionel Connell » Thu Mar 15, 2018 7:07 am

If you are planing on doing an enclosed engine you could save yourself an enormous amount of work by using an existing truck engine for the bottom end, replace the truck pistons with crossheads and bolt your cylinders on top where the head would normally be.

You then get a crankshaft, all of your bearings, con rods, oil pump, oil galleries, oil filter and oil sprayers for your cross heads as a pre-built unit.

Just a thought.
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Re: Resources/Information for Crank Lubrication?

Post by Lopez Mike » Thu Mar 15, 2018 8:01 am

Wouldn't even need to be a truck engine. Something small would probably handle the load. Like a Suzuki Samurai or some such thing. The limit would be the minimum bore spacing at the low pressure end.

How many crank throws does this dilithium crystal need anyway? Whadaya think, Scottie?
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Re: Resources/Information for Crank Lubrication?

Post by TriangleTom » Thu Mar 15, 2018 8:15 am

Lopez Mike wrote:Wouldn't even need to be a truck engine. Something small would probably handle the load. Like a Suzuki Samurai or some such thing. The limit would be the minimum bore spacing at the low pressure end.

How many crank throws does this dilithium crystal need anyway? Whadaya think, Scottie?
I'm planning on 5 throws, with an offset sprocket driven shaft for the eccentrics.

Lionel, I know a truck engine would probably be easier, but one of the reasons I wanted to do this was that it was something I could do more or less from scratch.
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Re: Resources/Information for Crank Lubrication?

Post by Lopez Mike » Thu Mar 15, 2018 8:25 am

I have my doubts about a roller chain drive providing enough accuracy. You might think about a gear drive or a timing belt.
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