Two Piece Crossheads

[Bruno TaylorParticipant @brunotaylor21701]

[Bruno TaylorParticipant @brunotaylor21701]

Hi There,

I have been looking at the design and construction of outside cyinder crossheads.

With the advances in bonding agents l am thinking about making the crossheads in two symetrical parts split along the line of the slidebars. I can then mill out a curved recess for the small end. I then propose to use two scews and an epoxy bonding agent to stick them together before milling the slideways and piston boss. The pin would be conventional.

Does anyone have any experience of this type of construction? Any views or comments?

Many thanks.

Bruno

[julian atkinsParticipant @julianatkins58923]

Hi Bruno,

These parts get quite a pounding and I would regard your proposal as totally inadequate in miniature locos. If a job's worth doing…

Sorry to be so blunt!

What loco are you making? And what gauge? I am sure with further details more productive comments will be forth coming.

Cheers,

Julian

[ManofkentParticipant @manofkent]

Hi Bruno.

Finding this one hard to picture – I always like new ideas to consider, so any chance of a sketch?

John

[J HancockParticipant @jhancock95746]

Try, The Model Engineer Pages 582,3,4,5 April 27th 1950.

The article is " Always something new", by Pat ,

All about pre-fabricated crossheads and slippers.

What a memory !

[Bruno TaylorParticipant @brunotaylor21701]

Here is the drawing of the crosshead I am considering.

It is based on Martin Evans usual type except that instead of a cover plate and close fitting!! washer I have designed two similar halves. This is for 3/4 scale loco (Princess Marina) so the bolts are 10BA.

The drop link is integral to the crosshead. I may consider reversing the upper row of bolts and substituting countersinks so that the external view is improved.

A concern is that the boss will be split, but with a horizontal taper pin should be okay.

I have not researched which bonding agent to use but an alternative would be silver soldering or brazing. Not keen on brazing but LBSC stuck all sorts of valve gear bits together that way.

Further comments and opinions most welcome.

[pgk pgkParticipant @pgkpgk17461]

And i can't believe there isn't a suitable glue… finding which one may be the problem. Large parts of aviation are glued together, carbon composites are basically just cloth and glue …Bluebells will be coming up soon for free glue..

[Russell EberhardtParticipant @russelleberhardt48058]

My main concern would be the piston rod/boss fixing. The taper pin will be in shear is the adhesive doesn't hold. Could you make it with the whole boss as part of one side?

Russell.

[Neil WyattModerator @neilwyatt]

Full size approach to fabrication seems to be 3-piece – a solid centre with two slippers bolted on:

[julian atkinsParticipant @julianatkins58923]

Hi Bruno,

Why not stick with the original design which is easy to make? LBSC's 'Doris' and 'Princess Marina' have the same type of crosshead.

As Russell states, the boss where the piston rod fits and is secured should be one piece, and not split.

You are making things far too complicated.

Cheers,

Julian

[JasonBModerator @jasonb]

If you want to split it put the split at one side so you are just adding a plate then the boss can be solid. A "U" shape with a plate either side is another option, the Minnie in my avitar is designed that way

Silver solder would stick it all together OK

[Michael GilliganParticipant @michaelgilligan61133]

Bruno,

These folks seem to have a good range of specialst adhesives for metals:

**LINK**

That said: I think you might have more joy Silver Soldering the job [Jewellery technique, using pallions]

MichaelG.

[Michael GilliganParticipant @michaelgilligan61133]

Posted by Neil Wyatt on 09/04/2016 09:41:51:

Full size approach to fabrication seems to be 3-piece – a solid centre with two slippers bolted on:

.

… and some very dodgy locking pins, and

Christmas Tree lights for back-lighting

[Author]

Posts