Resources/Information for Crank Lubrication?

[Lopez Mike]

Off topic but my only experience of TV was during my first marriage when for six years she watched anything with guns, sirens and squealing tires. When she ran off in 1976 I gave the infernal beast away. I'm not sure how I would find time for even this forum if one of those wretched things crept into my living room.

I've even tapered off on my classical FM music station as the ads have been getting more numerous and obnoxious. And as far as news, there hasn't been a president since Truman that I would let into my kitchen without counting the silverware afterwards.

That said, as soon as I figure out what photo hosting site I used last, I'll show you a few shots of my new boat under construction. The shape is a twin to Steve Parker's build. I'll swap my power plant into the new hull. I have a tentative offer from the lady down the street to take my old hull out of the yard. She wants to raise asparagus in it.

Back to crank lubrication . . .

I have single row sealed bearings on the mains. Everything else is lubricated with chain saw bar oil. I have a terrible suspicion that the expensive stuff is just bar oil repackaged.

[Lionel Connell]

Yes, the shortness of the 6A conrod is well known, what appears not so well known is that there are many engines with similarly short conrods, the Li Fu engines for example. I purchased the drawings of quite a number of engines and compared many features before I CAD modeled the 6A. My 6A is in fact taller than standard and has 1inch longer rods, also wider and longer cross head slides and shoes equaling 50% larger cross head bearing surface area, larger diameter main journals, larger big end journals and larger diameter little end pins. Around 80 modifications to the original design, including most of the modifications that were made by the late Alex Ritchie ( I have all of his workshop drawings for 6A) who built I believe more than 20 6As in total. The 80 changes include major modifications to the feed and vacuum pumps, lubrication system etc. I have carried out more than a little due diligence on my design work for my 6A.


The best way to reduce Die Block wear is not to reduce it's travel at the sacrifice of good timing events, but to increase it's surface area, use the correct materials and to provide reliable lubrication.

As part of my design work I carried out a comprehensive study of Stephenson's valve gear and spent more that 200 hours building the CAD models and running simulations and checking the results of my work. If you don't have faith in what I have written then please make your own comprehensive study. Let me recommend a good book. Design Procedures for Walschaert's and Stephenson's valve gears by D.L.Ashton. This guy is a mathematics professor and well respected long time builder of model railway engines. Mr Ashton's book is rather heavy reading, but well worth the effort of working through. I followed his process to the letter and proved conclusively, at least to myself, that he knows exactly what he is talking about.

Yes the suspension arms should be long, but they need to be connected to the correct position on the link, not the end of the link. The greater part of the cause of the sliding movement of the die block during running is not in fact the arc or swing of the lifting links, it is caused to a greater extent( in forward motion) by the reverse eccentric rocking the expansion link.


Photos of making all of my valve gear parts are here https://www.facebook.com/pg/steam.launc ... 1781014374
Lionel

[steamboatjack]

Its good to see that some one else agrees with what I have been preaching for many years.
Jack

[Lionel Connell]

Many thanks Jack.


Lionel

[DetroiTug]

Quote: "please make your own comprehensive study."

I agree with what you're writing and it works on your engine, but as I mentioned, to run a solids model simulator on one design and then claim it for all other steam engine designs is a bit cavalier. There are better valve linkage designs like Marhsall, Walscahert, Joy etc, than the Stephenson type, the Stephenson type is common because it is simple and compact which is important on a small engine.

George E Whitney was a brilliant licensed Boston tech (MIT) graduate steam engineer and designer and had complete understanding of valve gear designs as evidenced by his usage of many different types, many patents and mountains of evidence. He built and put steam engines on everything from boats to Singer sewing machines he sold to China for women with feet too small to work the treadle (true story), I'm confident if he had felt that the center suspended Stephenson link was of paramount importance, he would have done it no other way. He opted to place it on the end without concern and it has served well over time.

-Ron

[cyberbadger]

Quote: "please make your own comprehensive study."

I agree with what you're writing and it works on your engine, but as I mentioned, to run a solids model simulator on one design and then claim it for all other steam engine designs is a bit cavalier.

I think it's a bit cavalier when we all get into assumptions of what authority or proof(read:simulation or any math works) is the correct one and we get into arguments that really are just about what sources we trust.

Just realize that no one on this forum has the exact same set of sources that they trust for all things relating to steamboating. Some of that is just going to differ from person to person.

Some people will come to the table with no experience, some have decades of relevant education and experience. Doesn't mean that a posters opinion isn't as relevant.

Who would have thought... Anything you post on an internet forum really is just an opinion and a conversation and nothing more....

-CB

[marinesteam]

Maybe it's time to take a step back to remember that, in engineering, being perfect often takes a back seat to other aspects of a design. Good enough is just that, good enough.

Cheers

Ken

[Lionel Connell]

There are better valve linkage designs like Marhsall, Walscahert, Joy etc, than the Stephenson type

Yes, that is true. However, if you start modifying any of the valve gears that you mention it is very easy to destroy the motion, the means by which the designer managed to keep all of the valve events in balance. There are critical dimensional relationships and features in all valve gears that must be maintained in order for that particular mechanism to operate correctly and provide the engine with the best possible performance and efficiency.

Unless a person models a valve gear and studies the effects of any change that they make, it is impossible to understand the critical aspects. Otherwise they are just guessing in the dark about what is actually taking place, and, just how much negative effect a seemingly small change can actually make.



My discussion has been contained to Stephenson's valve gear; Stephenson's valve gear only works correctly, regardless of the engine that it is employed on, when the expansion link, and every other part of the valve train is built correctly to Stephenson's design so that it all works in harmony together. Perhaps it is better to put it like this: If a valve gear has the expansion link suspended from the end, then it is not in fact Stephenson's valve gear at all, because Stephenson's patent valve gear has the link center suspended and that aspect serves as a critical part of the motion, as is detailed in their patent documents.

On an engine the size of a 6A, moving the suspension point on the expansion link just 3mm from the correct location can create an imbalance in the cut off from one end of the cylinder to the other of more than 10% of the stroke length when the gear is notched back to 50% cut off. So on one stroke the cut off will be at 45% and the other it will be at 55%. This doesn't make for very smooth running. The unseen additional error is that the exhaust closure is effected by a similar amount, meaning that the compression in one direction will become far greater that the compression in the other direction. It is very easy to make seemingly small change but have it result in significant reduction in efficiency and longevity of the engine.

[Oilking]

Ken reminded me of a part in Robert LeTourneau's (the inventor if the carryall scraper & electric wheel) auto biography where he, as a young lad, was working in a foundry that allowed him to tinker in the machine shop during off hours. The old German machinist gave him the assignment of making a steam engine. Every day Robert would crank out a part to overnight find a way he could do it better. Soon the shop became littered with parts, but no engine. His tutor confronted him with the following,"Parts, parts all I see is parts, better a good engine that works than a better one that's never built."

Later LeTourneau relates what he called the other side to this story. He had finished building the race track at the Stockton CA fair grounds with his first scraper and gave a demonstration at the fair. Afterwords Harris of Massey Harris told him," you've got a neat machine there, might be able to put it on the market when you work the bugs out of it. Now son don't get ruffled, I saw you jumpin around like a monkey in a cage to run that thing. Just remember she's your baby and it doesn't bother you when she cries."

Keep up the discussion, it's sometimes like rethinking ones theology.

Dave

[Lopez Mike]

I'll have to take your word for it that most of our engines have less than optimal valve events. What I'm not sure about is what I might do about it.

There is no way that I'm going to do a simulation of my engine. It would take me a lot of time and right now my spare time meter is hovering around about a negative zillion hours. It sounds like that simply trying to improve things by moving the attachment point from one end or the other to the center isn't some quick fix.

Where might I go from here?