crosshead design

[mark rusche]

Does any one have suggestions on crosshead design ? Is it better to go with a concave type shoe style or machine tool v-way style or would linear bearings work on this application ? Be kind , this is my first engine attempt and I am still working on the piston pattern . Thanks Mark

[willy]

Mark you havent told us the major imortant thing here.

Size

On our models "keep it lubricated" applies. If it runs dry, it will wear out quickly. Yet if you oil it, it will last a long time.

For me I would be more concerned with how to easily be able to get oil to the area of friction. A groove running the length to allow oil to reside (some one mentioned a saw cut). Maybe a hole that is packed with cotton that allows oil to "wick" to the area.

If you are dealing with some massive weight, then you might consider like sealed ball bearings??? I really cant answer this area, as I mostly deal with scale.

Hopefully GWR will give some good enlightenment here. http://bbs.livesteam.net//biggrin.gif

Willy

[GWRdriver]

Mark,
Why don't you repost this on the other forum. You'll get a lot more input.

[Bill Shields]

mark:

Big question for most of us...what type of engine...stationary, locomotive, marine...????

Almost any well-designed, lubricated crosshead will work, but different types were used on locos, marine, etc:...

[mark rusche]

O.K. 7'bore x 8"stroke stationary type engine . 250 rpm max. Later ,Mark

[willy]

Did you mean 7 feet? or 7 inch bore?

[mark rusche]

oops , another typo, 7" bore is correct. Thanks

[GWRdriver]

We still need more information. Is the engine a hortizontal or vertical? Is the bed or column cast or built up? The crosshead design is going to be to a great extent dependant upon your bed design (or column design if it's a vertical). There two principle types of crossheads, the single shoe type and the double shoe. The single shoe is generally used on an open slideways which are integral with the column or bed. The double shoe type is used with a tunnel trunk guide which also can be on both horizontal or vertical engines.
There also bar-slide types but those are generally only seen on toy engines.

[mark rusche]

The plan so far is a horizontal type engine of cast iron construction with the cylinder being removable to make this as least difficult as possible to machine and make patterns for .Would the double crosshead type need to be machined on a shaper with a poke bar ?

[GWRdriver]

You could make the engine with seperate cylinder and trunk guide castings, or the trunk could be fabricated from steel (or cast iron) tube and could either be bored on a lathe or on a mill using a boring head. I don't know whether a shaper would be a necessity or not, might be, but lacking more detailed information I'd say that all the work could be done on a large'ish lathe and mill.

Have you done any research, as in looked in old books or catalogues to see how typical mill engines were built? This will give you a better idea of construciton details and assemblies than I can describe here. There was an amazing range made for actual work (as opposed to models) which varied from dead simple to extremely complex. It might be that one of the various model designs enlarged several times and adjusted for scale might work for you.


[This message has been edited by GWRdriver (edited 02-14-2006).]