what does the combination lever do on the valve gear.

Original Post

Big Jim, that link is only to a six-page table of contents.

Steam Punk, the combination lever was also known as "lap and lead lever." This is a hint to its function.

As the book describes it, the movement of the radius rod merges with the combination lever before that movement is transmitted to the valve stem and the valve. The bottom end of the combination lever has a backward and forward movement, in an arc, and this, when transmitted to the top of the lever in combination with the action of the radius rod at this point, imparts the required movement to the valve to keep the locomotive in operation. The combination lever acts on the valve in opposition to the crank when passing dead center.

Which I believe is a complicated way to say that the combination lever keeps the valve from getting into a position that would not allow steam to enter when the piston is at the far end of its stroke in either direction.

@smd4 posted:

Big Jim, that link is only to a six-page table of contents.

 

But comes from a very good reference resource, the ICS Blue Book archives.

Here's a link to the listing of digitized ICS Blue Books.  Railroad/Locomotive related books start at ICS BB 501, about midway down the page.  Some of the books, including the valve gear books, are broken down into multiple files.  

http://www.icsarchive.org/icsarchive-org/bb/

 

Last edited by SantaFe158

Sorry guys for the bad link. I got in a hurry before having to go out.

Let's try this one: VALVE GEAR

Correction made to first post.

Last edited by Big Jim

Big Jim has posted a wonderful reference and thanks for that. Here is one that might serve as an overall introduction- it is one of the better overview documents I have liked over the years, The book is long out of print.

Locomotive and valve gear_Page_2Locomotive and valve gear_Page_1

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@Big Jim posted:

Sorry guys for the bad link. I got in a hurry before having to go out.

Let's try this one: VALVE GEAR

Correction made to first post.

That's a great link, but that volume only covers Stephenson and Southern valve gear.

HERE is the link to the proper volume, which covers Walschaert and Baker valve gears. The description of the combination lever (which I quoted) is found, with a helpful diagram, on page 20.

A more in-depth discussion of the combination lever can be found in Part 2, starting on page 23.

Last edited by smd4

Thank you Steve! That is what I get for getting in a hurry (twice) and not double checking my work!

Last edited by Big Jim
@Big Jim posted:

Thank you Steve! That is what I get for getting in a hurry (twice) and not double checking my work!

Actually, that link you posted to the ICS index is fantastic, and should be marked as a favorite by everyone!

The link is a PDF so, if you have room, you can download it to either read at your leisure or print a hard copy.  I saved a copy to the same folder I have "Catechism of the Locomotive."  Haven't read (completely) either one yet but pick away from time to time.

As information, the Wildwood Publications Co. reproduced the entire set of ICS pamphlets, in 4 bound volumes, back in 1979. Searching various antique book sellers and eBay, might reveal a complete set.

@Hot Water posted:

As information, the Wildwood Publications Co. reproduced the entire set of ICS pamphlets, in 4 bound volumes, back in 1979. Searching various antique book sellers and eBay, might reveal a complete set.

Thanks for mentioning that.  I'll have to look into acquiring a set of those.  I've got a few key originals in my locker at work for reference purposes for the stuff that I generally work on, but it'd be nice to have a complete set of all of them in some form.

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