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Post by nigel21 on Jul 11, 2010 6:51:03 GMT
Hi all,
Awhile ago I seam to remember seeing an article on a double acting hand pump in ME, does anybody have this information or details of the issue please.
It may be some time ago while I was scanning through some old issues on a book stand.
Regards
Nigel
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Post by baggo on Jul 11, 2010 9:14:28 GMT
Peter Lewis described a fairly simple one in ME Vol.189 Issue 4179. Martin Evans also described one for Super Simplex, based on his double acting axle pump, which is more compact although more complicated (Vol 163 Issue 3852)
John
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firebird
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Post by firebird on Jul 11, 2010 17:27:10 GMT
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Post by nigel21 on Jul 15, 2010 6:30:48 GMT
Hi
Thanks for the information, Although not having much luck finding the mags,
Is anybody able to scan and send me copy particular the Martin Evans one please.
Regards and thanks
Nigel
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redmog
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Post by redmog on Jul 15, 2010 9:56:40 GMT
Martin Evans NOT Double Action Pump. Hi Thanks for the information, Although not having much luck finding the mags, Is anybody able to scan and send me copy particular the Martin Evans one please. Regards and thanks Nigel Here's a photo of the Martin Evans axle pump, from his Simplex book. It wouldn't take much modifying to a hand pump. But is this a true double acting pump? I don't see it as one, as the water is transfered from one side the piston to the other. So what's the point of this? Anyway, it might be of some help. Chris 
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redmog
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Post by redmog on Jul 15, 2010 10:08:00 GMT
Martin Evans Double Action Hand Pump. OK, I've found this one from his book. Now this is double acting. Chris 
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Post by houstonceng on Jul 15, 2010 17:47:12 GMT
Chris wrote
"But is this a true double acting pump?
I don't see it as one, as the water is transfered from one side the piston to the other.
So what's the point of this?"
Yes Chris. It is a double acting pump. Must say, I was sceptical when I first saw the design, but do a little calculation on areas (ie Volumes) on each side and you'll see that the annular volume on the pump-rod side is as near as makes no diference 1/2 of the volume on the other.
So when the rod moves fropm L to R, one 1/2 of the rh volume is pumped into the left side and one 1/2 leaves the pump via the outlet valve. When the pump rod moves R to L, the same volume leaves via the outlet, whilst a new (full) volume fills the rhs.
Shimple !
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redmog
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Post by redmog on Jul 15, 2010 17:52:58 GMT
Single action or Double action.
Gotya, and well spotted.
So it's a one and a half acting pump.
It's interesting, I'll have to do some calculations and see how more efficient it is.
But as you have pointed out - it must be about 50% more efficient. Thanks,
Chris
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Post by baggo on Jul 15, 2010 20:24:22 GMT
Martin wrote a later article on an 'improved' axle pump for Simplex as the original design (shown above) is not actually double acting. It only has a water inlet to one side of the piston and so could only draw in water on the outward stroke. The water drawn in is then pumped out split between the inward and outward stroke, which gives the impression it is double acting. In other words, the pumping capacity is only that of a single acting pump.
The later improved version has two water inlets, the same as the hand pump version, and is truly double acting.
John
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Post by houstonceng on Jul 15, 2010 20:55:49 GMT
John
It is double acting in that nearly the same volume of water is pumped out on the "downstroke" and "upstroke" (or Instroke/Outstroke ?).
A single acting pump only pumps out water when the plunger is pushed (or pulled) by NOT both.
Think about it ! Then think about a single acting steam engine vs a double acting steam engine and you'll see what constitutes the terms.
Andy
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redmog
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Post by redmog on Jul 15, 2010 21:04:26 GMT
Baggo's Right Again. Martin wrote a later article on an 'improved' axle pump for Simplex as the original design (shown above) is not actually double acting. It only has a water inlet to one side of the piston and so could only draw in water on the outward stroke. The water drawn in is then pumped out split between the inward and outward stroke, which gives the impression it is double acting. In other words, the pumping capacity is only that of a single acting pump. The later improved version has two water inlets, the same as the hand pump version, and is truly double acting. John John, I've just studied it and done some calculations. You're right. It only pumps the same capacity as a single acting pump. It can only be considered more efficient by its mechanical advantage, the fact that less pressure is applied on the input lever. 66% in push, 33% in pull, compared to 100% in push and 0% in pull on single acting. The fluid dynamicists will have their calculators out. Oh look what I've started. And who said this forum was becoming boring. You wait until DJ gets out of bed the other side of the world. Pity JB's not around; or is he 'lurking'? Andy, you're also right - it is double acting Chris
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steam4ian
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Post by steam4ian on Jul 15, 2010 21:34:46 GMT
G'day Chris
The Martin Evans pump can be made to deliver the same quatity of water for the in stroke as the out stroke. What is needed is the correct relationship between the cylinder diameter and the piston rod diameter. True, the volume pumped is only the water induced on the out stroke; to get double the volume you need to increase the cylinder diameter by a factor of 1.4.
I have seen the ME design with the transfer valve in the piston; sometimes using a floating piston ring to open and close the transfer ports.
Due to the piston rod having cross sectional area a truly double acting pump will not deliver balanced water quantities.
Regards
Ian
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Post by baggo on Jul 15, 2010 23:53:48 GMT
It is double acting in that nearly the same volume of water is pumped out on the "downstroke" and "upstroke" (or Instroke/Outstroke ?). A single acting pump only pumps out water when the plunger is pushed (or pulled) by NOT both. Think about it ! Then think about a single acting steam engine vs a double acting steam engine and you'll see what constitutes the terms. Ok Andy, I agree on that  Both sides of the piston are used so that suggests double acting. It was Martin himself who said that it wasn't. Apparentally he copied a design by Edgar Westbury, which he (Edgar) called a 'differential' double acting pump. In any event, I think most hand pumps don't have enough capacity to get water into the boiler 'in a hurry' and a proper double acting pump can shift more water than a larger diameter single acting with a lot less effort involved. John |
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Post by houstonceng on Jul 16, 2010 10:09:12 GMT
John wrote :
"In any event, I think most hand pumps don't have enough capacity to get water into the boiler 'in a hurry' and a proper double acting pump can shift more water than a larger diameter single acting with a lot less effort involved."
Totally agree, in which cae I'd build something like the double acting hand pump that Chris posted - but I'd definitely NOT waste half the capacity on the lhs by having a 3/8" piston rod in a 5/5" bore.
The only problem about trying to get a lot of water into the boiler when it's at 100psi is that you need a big pump AND a very long pump-handle. On one of our club locos, the handle is about 4" long and the pump has a bore of 3/4" !!!!!
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Post by maunsell on Jul 19, 2010 22:05:19 GMT
Roy Amesbury had a vertical handpump design in which there were no inlet valves, water being drawn in through a ring of small holes near the top of the ram stroke, and the outlet ball valves were below the tender floor. The rams utilised "O" rings and the beauty of the design is its simplicity and that if an outlet valve sticks it is easily accessible from below the tank.
The handpump can be either a single or twin ram to choice but is only single acting.
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Post by jo479 on Jun 5, 2019 20:19:56 GMT
couldn't find the article, what was it called? |
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Post by springcrocus on Jun 5, 2019 21:58:15 GMT
couldn't find the article, what was it called? This thread is nine years old and firebird hasn't logged in for about six months. You might wait a long time for a reply. Steve |
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dscott
Elder Statesman
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Post by dscott on Jun 6, 2019 1:36:07 GMT
Another way is to use two single pumps either end of a single ram therefore keeping it simple and if one happens to fail you still have one working!! I am fitting two Speedy axle pumps on the footplate of the Fowler Complex I am trying to get done in another month!!!! Hence I have just left the drawing board with tomorrows batch of bits on it! (Some modified as they did not quite work in the flesh!!!)
Anyone fitting one of these so called DOUBLE ACTING on a Simplex is down for trouble as it is pumping stuff all over the place? And it has two Glands or seals which add to the drag? Someone clearly was having a joke at the builders expense!!!!
SO, One gland at the handle end! Do not fix the tank round it! Make a nice handle! And fit an electric pump with a big RED BUTTON!!!
David.
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Tony K
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Post by Tony K on Jun 6, 2019 8:14:37 GMT
Another way is to use two single pumps either end of a single ram therefore keeping it simple and if one happens to fail you still have one working!! I am fitting two Speedy axle pumps on the footplate of the Fowler Complex I am trying to get done in another month!!!! Hence I have just left the drawing board with tomorrows batch of bits on it! (Some modified as they did not quite work in the flesh!!!) Anyone fitting one of these so called DOUBLE ACTING on a Simplex is down for trouble as it is pumping stuff all over the place? And it has two Glands or seals which add to the drag? Someone clearly was having a joke at the builders expense!!!! SO, One gland at the handle end! Do not fix the tank round it! Make a nice handle! And fit an electric pump with a big RED BUTTON!!! David. That was your opinion David, and I respect that. My experience has been different. Having cared for a Simplex with the Martin Evans type of axle pump at my club, I found the pump very good - and pumped in loads more water than needed - a good fault when novices are learning on a club engine. I wouldn't spend too much time arguing about whether it is/is not a true double-acting pump - that's for the armchair pontificators (RIP DJ). Just to say it worked very well for me - therefore, for me, it is a very good design.  |
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Post by builder01 on Jun 6, 2019 10:13:03 GMT
I have both the axle pump and hand pump in my Super Simplex (Martin Evans). They both work fine and do exactly what they are supposed to do. I made the axle pump from a casting and the hand pump I machined from the solid. These are both good performers.
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Both sides of the piston are used so that suggests double acting. It was Martin himself who said that it wasn't. Apparentally he copied a design by Edgar Westbury, which he (Edgar) called a 'differential' double acting pump.
