CONWAY 0-4-0 3 1/2" GAUGE LOCO

[Kim]

Great update, Rich.  And nice work on the valve rod!  It's always hard getting things bent a the correct angles AND in the right place at the same time, and you did admirably.

There's always alignment issues, isn't there?  I'm sure you'll sort that out too.  Looking forward to seeing how you accomplish it.
Kim

[cnr6400]

Hi Rich,

Just a thought - could you make the bent link from flat steel stock, and make the ends as clamps? I'm thinking of the link part and two separate clamps like bearing caps with a pair of clamping screws each, maybe to the side of the valve and eccentric rods toward the pump. That way, you'd still have adjustability of the valve to link joint but the clamp screws would be accessible from under the engine vertically, no need to turn the link next to the wheel at all.

I've studied several of Martin Evans' locomotive designs and have noticed there's a lot of things that are easy to draw but hard to make. He was not good at thinking through things to make assembly easy.

[g0rph]

Hi Rich,

Even easier than cnr6400s suggestion is to make the offset of 3/16" to the rear of the leading axle by means of a small block with two parallel 5mm holes separated vertically by 3/16+.   That block can be silver soldered to the two stubs of stainless going in the opposite directions.   

Then make the "valve spindle coupling" with an offset of 5/16 horizontally (as Martin Evans drawing) AND 3/16+ vertically.    There is no need for the adjustable (LH and RH threaded) coupling to be in line with the bearing, it will work just as well 3/16 higher!

I do agree though on the difficulty of making some parts.....the weighshaft bearing is a case in point that you have neatly "productionised".

Regards,   Richard.

[Firebird]

Hi

Thanks for the suggestions Kim, cnr6400 and Richard 

I had thought of fabricating somehow 

It will have to wait until the weekend now though

I wonder if Martin Evans ever actually built any of the loco's he designed 

Cheers

Rich

[Firebird]

Hi

The modified valve rods start life as 2 pieces of 3/8" x  3/4" flat steel bar. In the mill and machine away the centre section.

Knock the corners off with a 45° cutter

Drill and ream 5mm

Drill and tap for grub screws. I have a bag of assorted grub screws so in this case 3/16" UNF was used

A trial fit

There should be no need for the right hand/left hand thread adjuster now

Cheers

Rich

[cnr6400]

Looking good Rich, simple and robust solution, well made. Shame Mr Evans didn't think of that.......

[NickG]

Looks much better than bending the rod. I hate bent rods, so difficult to get the axes in the same plane and usually means alignment issues.


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[Ye-Ole Steam Dude]

Hello Rich,

That is slick and a great piece of engineering on your part.

Have a great day,
Thomas

[zeeprogrammer]

A little off topic...I'm curious as to how you are doing your posts...

I see text left justified and the photos seem either left or middle justified.

How are you doing that?

I like it because the text shows more clearly between photos (it's easy to miss the text in other posts).

[Firebird]

Hi

Thanks cnr6400, Nick and Thomas 

Carl. I have absolutely no idea. I write the text  and then insert the photo link 

Now then my learned friends question time 

I need some help in setting the eccentrics on the axle and the slide valve

Can anybody help here, preferably in the simplest of terms that a 5 year old could understand

Cheers

Rich

[NickG]

Stephensons valve gear is a right pain in my limited experience! Should be ok though as long as your method of locking them to the axles is robust and they don’t move. I doubt my explanation will be very clear but here goes!

Start with setting for forward motion:

Set leading piston to top or front dead centre and the expansion link / reversing lever in the full forward position. It’ll be much easier if the reversing lever is linked up.

Adjust the forward eccentric for that cylinder so that you can just see a hairline crack developing between valve and front port. Apply slight pressure to valve in direction it is moving whilst doing this, takes up any clearance in the system. Remember the eccentric should be set such that, as the wheel rotates (forward direction) the port is opening! So it’s pulling the valve backwards.

Do the same for the other side, remember to set the piston to top / front dead centre first by rotating in forward direction (90 degrees)

Now set for reverse:

Stay on the same side but put the expansion link in the reverse position. Same drill as before but set the reverse eccentric so that the hairline crack appears at the front port. Remember this time that the port should open as the wheel rotates in the reverse direction.

Go back to the other side, move piston to top / front dead centre by rotating in reverse direction (90deg). Same as before, set reverse eccentric so that the hairline crack appears in front port, again ensuring it is moving in the correct direction, opening the port as the wheel rotates in reverse direction. Always remember to apply the slight pressure to valve in direction it is moving.

I think this is correct, hopefully somebody will say if not! I had trouble with my 3 1/2” Mabel trying get ready to test on air. It had inside cylinders and not much distance between the frames so even less room. The grub screws that held the eccentrics in position weren’t man enough and things kept moving. Also the eccentric sheaves were so thin and has no way of rotating without taking the cap off the strap! Terrible! hopefully yours will be far better.


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[Firebird]

Hi

Thanks Nick

I shall sit and read and inwardly digest until hopefully the penny will drop

The reversing lever and stand has been temporarily fitted

A reach rod has been made. As yet not hardened or fully machined

The pins for the lifting links I am using M4 socket head cap screws, the shank being just the right length. I am going to make some brass spacers to go go between each pair of links

A bit of video

<a href="https://www.youtube.com/watch?v=7zBF6McxUjQ" target="_blank">http://www.youtube.com/watch?v=7zBF6McxUjQ</a>

Cheers

Rich

[Firebird]

Hi

To make some valve chest gaskets I printed out exact size then used that as a template

The right hand valve chest fitted with its slide valve

Cheers

Rich

[Firebird]

Hi

I'm having one of my moments again 

Take a look at the following snip from the article

It shows the right hand side of the loco.

The side view shows the top eccentric rod, which is the straight forward rod, fitted to the inner of the eccentrics and the lower bent backward rod fitted to outer eccentric

But the top view seems to show the reverse??????

Cheers

Rich

[crueby]

You are right!
Hand drawn vs CAD drawn strikes again?