Author Topic: 3.5" Northumbrian Loco  (Read 2177 times)

Offline Baner

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Re: 3.5" Northumbrian Loco
« Reply #15 on: July 17, 2018, 03:07:02 PM »
The pump body needed prepping for the outlet soldering. A bit of scrap was chucked in the lathe, a section turned to 6.35mm and threaded 1/4x40. One of the port ends was screwed on and the live center brought up to support the other side. The outside of the port was cleaned up, the pump body flipped and the process repeated for the other side:

Northumbrian by DAVID BANER, on Flickr

The pump body is then taken to the mill and outlet port counter bored with the 8mm slot drill same as the inlet elbow. Missed a photo of that.
The parts to be soldered are fluxed and installed:

Northumbrian by DAVID BANER, on Flickr

Northumbrian by DAVID BANER, on Flickr

Parts are then soldered a dropped in the pickle:

Northumbrian by DAVID BANER, on Flickr

Dave.
« Last Edit: July 28, 2018, 10:13:30 AM by Baner »

Offline Ye-Ole Steam Dude

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Re: 3.5" Northumbrian Loco
« Reply #16 on: July 17, 2018, 03:14:21 PM »
Hi Dave,

Love the looks of your Loco and will follow along.

Have a great day,
Thomas

Offline Baner

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Re: 3.5" Northumbrian Loco
« Reply #17 on: July 17, 2018, 05:04:00 PM »
Thanks for looking in Thomas.


I've done a little research into ball valves so I thought I do a post on what I found.

For those who don't know ball type valves are found all over model locomotives. They're variously called 'check valves' or 'clack valves' and elsewhere 'one way valves' or 'non-return valves'. Here's a picture:

Ball and seat by DAVID BANER, on Flickr
 
Basically liquid comes in from the bottom,the ball lifts, liquid flows. If it tries to come back down the ball is pushed onto the seat and flow stops. This only works if the ball seats properly.

The traditional method for creating the ball seat is to drill the port, ream, drop the ball on top the hole and smack the ball with a hammer, the ball is thrown away and a new ball is used in service. The ball is typically made of Stainless Steel.

My own experience is fairly limited, but I vaguely knew that some people had problems with sealing. So looking about I found, (in typical internet fashion) that the traditional method works for about the same amount of people that it doesn't work for...Some problems are as follows:

-Not hitting the ball hard enough.
-Hitting the ball to hard.
-Not reaming the hole.
-Not hitting the ball square on.
-Not replacing the ball after hitting.
-Cheap, out of round balls.

And solutions:

-Press, rather than hit the balls.
-Ream the hole. The hole needs to be perfectly cylindrical to fully contact the ball. Also, the reamer helps debur the seat area.
-Use a close fitting drift. Machine something up that's a tight fit in the bore to make proper straight contact with the ball.
-There's a few options for balls to use. Good quality stainless will generally work but is a bit wasteful and there can be minor differences between hit ball and service ball. Some people use rubber balls,(O-ring material) but they can get stuck on the seat or sucked into the pipe. There is also ceramic balls, (silicon nitride being the most common) which have the advantage of being super hard. These can form the seat without having to be replaced. They are a little more expensive than stainless steel, however.

So what I took from all that, and what I plan to do myself, is use the vice to press in silicon nitride balls with a suitable drift.

Two other things to consider. One is ball/seat size. Fortunately this resource is available:

http://ibls.org/mediawiki/index.php?title=Design,_Care_and_Feeding_of_Check_Valves

Here is a table from the link:

Everett Clem Ball Seat Table1 by DAVID BANER, on Flickr

I'm unsure how the data was compiled but plenty of people claim it sound. So in the case of my axle pump, the seat is 4mm or 5/32 so I've got 7/32 balls on order.

The other consideration is the finishing of the seat area. A concave finish such as left by a drill is considered unsuitable. Flat is better, and some say convex is best, though I found nothing definitive other than don't drill finish. I made a D-bit style cutter for a convex finish.

That's about it for balls. There is also another type of 'T' valve sometimes used instead of balls, (think tap washers) but I think I've gone on enough. If you got this far well done. I'm not anywhere near an expert on this, I've just collected other peoples experiences into this post. If there is anything I've missed (or got wrong) please chime in.

Dave.
« Last Edit: July 22, 2018, 02:32:14 PM by Baner »

Offline Ye-Ole Steam Dude

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Re: 3.5" Northumbrian Loco
« Reply #18 on: July 17, 2018, 05:16:38 PM »
Hello again Baner,

A light compression spring centered over the top (outlet side) of the ball also aides in getting a good seal and it prevent swirling of the fluid causing the ball to chatter.

Have a great day,
Thomas

Offline crueby

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Re: 3.5" Northumbrian Loco
« Reply #19 on: July 17, 2018, 05:22:20 PM »
Great tips. I have always had trouble with them, one thing I had not done was ream the smaller hole, that could well be the issue I had.




Thanks!

Offline Baner

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Re: 3.5" Northumbrian Loco
« Reply #20 on: July 22, 2018, 02:24:48 PM »
Not a lot done on the loco this weekend, just one easy part, the axle pump ram:
Just a piece of 5/16" Stainless steel round cut and cleaned up to 26.2mm - whoops - drawing misread; make that 30.95mm:

Northumbrian by DAVID BANER, on Flickr

Then clamped in the collet block to mill a flat and cut a 2mm slot about 5mm deep:

Northumbrian by DAVID BANER, on Flickr

Then just drill through 3/32":

Northumbrian by DAVID BANER, on Flickr

Quick and easy:

Northumbrian by DAVID BANER, on Flickr

Shop time wasn't quite that dismal however, I also managed some lubricator pump bodies, half finished:

Lubricator by DAVID BANER, on Flickr

and put a new shelf up above the small lathe and mill for tooling:

Workshop by DAVID BANER, on Flickr

The old storage spot was the tool box under the lathe, but my two year old son has claimed it as his own and 're-organized' it all over the workshop.

Dave.



« Last Edit: July 22, 2018, 02:28:22 PM by Baner »

Offline Baner

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Re: 3.5" Northumbrian Loco
« Reply #21 on: July 28, 2018, 02:48:45 PM »
The pump continues:
I'd planned to ream the pump barrel to size, but for a similar price I decided to get something that would be used more than once:

Northumbrian by DAVID BANER, on Flickr

Small bore gauges are not super accurate but will get me close enough. Now I needed a small boring bar. I make these by cutting off a piece of HSS, then mill a flat on a length of silver steel (in this case 5mm). I cut a little piece of silver solder sheet, then stack all the bits up on and flux. Heat from underneath until the solder flashes, then grind to shape:

Northumbrian by DAVID BANER, on Flickr

So the pump body was chucked up again, and I'm back where I was 2 1/2 weeks ago. The bore is drilled, then slowly bored to size. Little boring bars like this are tricky due to deflection, but I got there in the end (and forgot a final photo):

Northumbrian by DAVID BANER, on Flickr

There's still more to go, this pump seems to be taking forever to finish...

Dave.



 


 

Offline Baner

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Re: 3.5" Northumbrian Loco
« Reply #22 on: July 30, 2018, 03:22:23 PM »
Next job is to turn down the barrel and thread it 1/2 x 32. I've got a Die to do the threading as the lathe is metric. I also managed to forget my lathe Die Holder is metric too. :wallbang:
More tooling! On the plus side the bigger lathe got some use for a change. An adaptor was turned up:

Northumbrian by DAVID BANER, on Flickr

And the barrel threaded:

Northumbrian by DAVID BANER, on Flickr

The pump ram is sealed by a gland that threads onto the end of the barrel. This part had been previous rough turned and threaded; it is now screwed onto the barrel and the bore finished to size, concentric with the barrel bore. Then off to the mill for some spanner flats:

Northumbrian by DAVID BANER, on Flickr

Dave.

Offline Baner

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Re: 3.5" Northumbrian Loco
« Reply #23 on: July 30, 2018, 03:46:07 PM »
Almost done!
I don't need the chucking piece on the pump anymore so that gets parted off and cleaned up:

Northumbrian by DAVID BANER, on Flickr

I need a lock nut to clamp the pump to the stay. I didn't have the right sized Hex bar so a stub of 3/4 round goes to the rotary table and get milled into shape. Then to the lathe and finished off:

Northumbrian by DAVID BANER, on Flickr

All that's left is to form the ball seats, (the balls have yet to arrive) clean up a bit and I'll probably paint the leftover raw cast areas. Here it is installed in the chassis:

Northumbrian by DAVID BANER, on Flickr

Dave. 

 
« Last Edit: August 04, 2018, 03:22:56 PM by Baner »

Offline Admiral_dk

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Re: 3.5" Northumbrian Loco
« Reply #24 on: July 30, 2018, 08:48:57 PM »
Nice result on the pump  :ThumbsUp:

It looks to me like there is more than one eccentric on the axel next to it - are there more "service items" that will be driven from it ?

Best wishes

Per

Offline Baner

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Re: 3.5" Northumbrian Loco
« Reply #25 on: July 31, 2018, 03:39:16 PM »
Thanks Per -
The other two eccentrics operate the valves. Here's a drawing of the layout from the magazine:

Northumbrian by DAVID BANER, on Flickr

You can see the other eccentrics connected to a rocker shaft which transfers the motion outside the frame to the cylinders. The other 'service item', the lubricator, is connected to the same eccentric as the pump by ways of the pump ram; in post#20 I milled a flat on the ram - that is where the lubricator drive connects.

Dave.

Offline Admiral_dk

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Re: 3.5" Northumbrian Loco
« Reply #26 on: July 31, 2018, 08:39:21 PM »
Thank you David  :cheers:

I hadn't realized that it was the main driving wheel axel I was looking at in the picture, but seeing the sketch certainly made it clear to me and explains it all  :ThumbsUp:

Per

Offline Baner

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Re: 3.5" Northumbrian Loco
« Reply #27 on: August 04, 2018, 03:03:47 PM »
Up next are the eccentric straps.
I'm not overly impressed with the castings I'd received, but they can be made to work. They're not going to match the drawing but the critical dimensions should be achievable. First a clean face:

Northumbrian by DAVID BANER, on Flickr

Now that there's something flat to clamp against I started to chase flat surfaces around the straps:

Northumbrian by DAVID BANER, on Flickr

 Eventually they all came in at matching, usable dimensions. Then the straps are marked for the next operations:

Northumbrian by DAVID BANER, on Flickr

Dave.
« Last Edit: August 06, 2018, 11:03:13 AM by Baner »

Offline Baner

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Re: 3.5" Northumbrian Loco
« Reply #28 on: August 04, 2018, 04:35:56 PM »
Now I drill through at 2.3mm and then drill 3mm clearance to 6mm deep, which is about half the depth of the side boss. Then the bottom half is tapped 6BA:

Northumbrian by DAVID BANER, on Flickr

Then it's over to the mill to split the piece in two. I'm using a 0.5mm saw here so I take it easy and make several passes to get through:

Northumbrian by DAVID BANER, on Flickr

Then 6BA studding is screwed in with a bit of loctite 243 for good measure:

Northumbrian by DAVID BANER, on Flickr

Dave.
« Last Edit: August 06, 2018, 11:06:42 AM by Baner »

Offline Baner

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Re: 3.5" Northumbrian Loco
« Reply #29 on: August 12, 2018, 03:29:53 PM »
I haven't had a lot of time for the loco lately so just a little bit more on the straps:
The rough cored hole leaves no reference for centering in the four jaw so a piece of flat bar is clamped in the tool post and the top edge brought to center height. Then we can eyeball the split line and the vertical center marked out on the surface plate back at post#27:

Northumbrian by DAVID BANER, on Flickr

Unfortunately the boring bar is going to hit the outside jaws, so the set up is changed and the straps are bored to size:

Northumbrian by DAVID BANER, on Flickr

The easiest way to machine the straps to width is to make a mandrel to clamp them to. The diameter is turned to just slightly larger the the strap's bore so they will clamp on without spinning. This also ensures the sides of the strap will be machined parallel to the bore:

Northumbrian by DAVID BANER, on Flickr

All three are done in the same way:

Northumbrian by DAVID BANER, on Flickr

Though these castings will be functional, as can be seen in the photo, they are not the nicest looking things. They'll be hidden from view inside the chassis, but I might need to do something about their appearance.
If I can figure out what to do.

Dave.