chrisb
Part of the e-furniture
Posts: 340
|
Post by chrisb on Sept 15, 2020 8:02:45 GMT
My Wren has a cross head pump as drawn by Ken Swan. It is long stroke and small bore, without a bypass but the feed is regulated by throttling the suction but it has an “air bottle” to take some of the hammer out of it.
|
|
JonL
Elder Statesman
WWSME (Wiltshire)
Posts: 2,907
|
Post by JonL on Sept 15, 2020 21:18:21 GMT
I did wonder about putting a steam pump on something but more for the challenge than anything else. It wouldn't be in keeping with anything and it would be a new level of complexity for no real benefit, but so cool!
|
|
|
Post by Roger on Sept 15, 2020 21:28:30 GMT
I did wonder about putting a steam pump on something but more for the challenge than anything else. It wouldn't be in keeping with anything and it would be a new level of complexity for no real benefit, but so cool! One of our club members has a nice little two cylinder donkey pump and it's delightful. You can set it so that it's hardly moving, and it's lovely to watch.
|
|
|
Post by suctionhose on Sept 16, 2020 0:29:14 GMT
I find with smallish loco's like Speedy, the combination of axle pump and injector provided the most pleasurable driving experience. You put in a constant feed with the pump as a baseline and use the a small injector to top up, avoid blowing the SV etc. It's a realistic driving technique - controlling steam with injector / fire - but you don't have to struggle against losing pressure while you get enough water in. The pump does 90% of it in a nice steady manner (while moving) Re lubrication of the plunger. This a pump I've just finished for my Ploughing Engine. The seal is an oring way down inside in the groove on the tip of the plunger. the gland is a dummy which provides an annulus for oil to enter and be distributed up and down by the grooves in the plunger.
|
|
dscott
Elder Statesman
Posts: 2,438
|
Post by dscott on Sept 16, 2020 6:42:45 GMT
My whole day with a Speedy began with the Immortal words. THE INJECTOR DOES NOT WORK! So the axle pump gave me a wonderful time. Gloved right hand for the interface between the lever and the boiler!!! Dreamed about a double acting hand pump of course. High pressure 12 volt pumps being several years away back then. Roger had just started his 1501.
David and Lily.
|
|
|
Post by andyhigham on Sept 17, 2020 14:51:50 GMT
Sticking balls!! If the suction side valve was horizontal, when at rest gravity would not be holding the valve on it's seat. as soon as the pump started to move water the valve would be pushed onto it's seat as normal. Or is there more to it?
|
|
|
Post by John Baguley on Sept 17, 2020 15:37:33 GMT
Gordon Smith designed a handpump with that feature. I think it was described in EIM. He had one set up as a demonstration at the Midlands ME Exhibition some years ago.
John
|
|
|
Post by andyhigham on Sept 17, 2020 20:31:12 GMT
As the axle pump is usually "up front" I wonder what the benefits would be if the outlet pipe went up into the smoke box and made a few circuits of it before exiting and heading off to the feed clack
|
|
|
Post by suctionhose on Sept 17, 2020 23:19:08 GMT
Sticking balls!! If the suction side valve was horizontal, when at rest gravity would not be holding the valve on it's seat. as soon as the pump started to move water the valve would be pushed onto it's seat as normal. Or is there more to it? Interesting thought. I wonder if it would work expelling air while lifting the water? Hard to get a pump going with a crook suction valve... Although my TE pump is larger than a 5"g one (5/8" dia), you may be interested to see the valves. They have a teflon washer encapsulated in a cup rather like like a traditional tap washer. First time I've done things this way so well see!
|
|
|
Post by runner42 on Sept 17, 2020 23:49:19 GMT
Here is Allan Wallace designed axle pump, it overcomes many of the issues experienced with for example LBSC's axle pump. The major benefit is that it provides better support for the ram and the ability to provide lubrication inside the pump. Brian axle pump by Brian Leach, on Flickr
|
|
|
Post by Jim Scott on Sept 18, 2020 10:26:30 GMT
Brian Allan Wallace's design is a very elegant improvement - and I note it has an oil reservoir....
For comparison I have attached a couple of photos of LBSC's original axle pump design for Maid of Kent published in Model Engineer circa 1948. The first shows the pump layout which was pretty conventional for its time. The second shows the difficulties he had in accommodating the pump into the overall design, where there is no direct drive available from an axle. However the rocking lever with floating pivot must be regarded as adequate given the number of MoK's built over the years. Bought as something to play with whilst building my own loco, an early failure was the fracture of the rocking lever across its centre bearing. This allowed the end of the eccentric drive rod to drop into the track bed, literally catapulting the loco off the track. Luckily I was moving quite slowly and as the loco dismounted from the raised track at a grassy area no serious damage was caused. Gave me a bit of fright though...!
It is thought that a contributory factor in the failure was increased loading due to lack of lubrication of the stainless steel ram working in a bronze bore. Unlike the drawing above, at some point previously the ram had been modified with an o-ring at the working end so not even water lubrication was present.
Jim S
|
|
|
Post by andyhigham on Sept 18, 2020 15:53:58 GMT
What causes balls to stick? I have always had good results using a 90 degree included angle seat, the ball rests tangentially not on a corner
|
|
|
Post by Roger on Sept 18, 2020 18:58:34 GMT
Here is Allan Wallace designed axle pump, it overcomes many of the issues experienced with for example LBSC's axle pump. The major benefit is that it provides better support for the ram and the ability to provide lubrication inside the pump. Brian axle pump by Brian Leach, on Flickr That's more complicated than it needs to be. You only need a groove in the ram to take the 'O' ring, you don't need to contrive a pocket outside. The oil reservoir can be in the main body or in a separate cup like I've done.
|
|
|
Post by Roger on Sept 18, 2020 19:02:54 GMT
What causes balls to stick? I have always had good results using a 90 degree included angle seat, the ball rests tangentially not on a corner I imagine it sticks with the limescale that's deposited when the water evaporates. I think any metal to metal contact when it dries out will cause it to stick, regardless of the shape. That's why I don't let the ball rest on the seat until there's reverse flow to fully close it. That way it can't stick. Any method will do, a spring, or O-ring cord across under the ball is all you need. The lift only needs to be about 0.2mm and the force required to do that is tiny. I used 1mm section cord.
|
|
|
Post by andyhigham on Sept 18, 2020 19:27:01 GMT
Maybe I'm just lucky to live in Lancashire. Beautiful soft water, no limescale and makes a perfect cup of tea
|
|
|
Post by andyhigham on Sept 18, 2020 19:32:24 GMT
How well does water lubricate a stainless steel plunger running in a bronze/brass cylinder? If I fit axle pump(s) to the "Jack" it will be submerged in the well tank so could easily be water lubricated
|
|
|
Post by Roger on Sept 18, 2020 19:42:06 GMT
How well does water lubricate a stainless steel plunger running in a bronze/brass cylinder? If I fit axle pump(s) to the "Jack" it will be submerged in the well tank so could easily be water lubricated I should imagine that Water is pretty useless as a lubricant, but I may be wrong. It might be marginally better than nothing though.
|
|
|
Post by builder01 on Sept 18, 2020 22:38:22 GMT
So, if the metal ball is not on the metal seat when the water evaporates, where does the lime scale go? Is is evenly distributed all over the inside of the valve and the outside of the ball? It seems like the lime scale will still be there if the ball is on the seat or not. Will the ball be able to re-seat with lime scale on the seat?
I use hard viton balls in both my hand pump and axle pump. These seal even if the seat is not perfect as they are slightly elastic, they seem to not stick either. I also use a viton ball on the clack between the injector and the boiler.
|
|
JonL
Elder Statesman
WWSME (Wiltshire)
Posts: 2,907
|
Post by JonL on Sept 18, 2020 22:47:53 GMT
I'm very tempted to try viton balls. Who do you usually get them from please?
|
|
Gary L
Elder Statesman
Posts: 1,208
|
Post by Gary L on Sept 18, 2020 22:53:49 GMT
Here is Allan Wallace designed axle pump, it overcomes many of the issues experienced with for example LBSC's axle pump. The major benefit is that it provides better support for the ram and the ability to provide lubrication inside the pump. Brian axle pump by Brian Leach, on Flickr That's more complicated than it needs to be. You only need a groove in the ram to take the 'O' ring, you don't need to contrive a pocket outside. The oil reservoir can be in the main body or in a separate cup like I've done. Agreed. Never use a so-called anti-airlock pin either. Water is incompressible, so what happens when you block its only exit with a pin before the ram finishes each stroke? Gary
|
|