Author Topic: Rider Ericsson expansion globes  (Read 538 times)

Offline Lodalodge12

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Rider Ericsson expansion globes
« on: September 26, 2021, 09:51:32 PM »
I am undertaking the building of the 2" Rider Ericsson pumping engine and I cannot find any info, dimensions, material or method of making the globe shaped expansion chambers.  Are they real, "ie" hollow inside or just dummies?
An info appreciated..Carson

Offline Bobsmodels

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Re: Rider Ericsson expansion globes
« Reply #1 on: September 28, 2021, 10:20:34 PM »
Carson

Your note really hits home, I am procrastinating on the globes.  I spent time measuring full size ones.  They were different sizes.  I think one person told me Ericsson just purchased from suppliers so got different ones.  I made up a CAD drawing of an average of all the sizes.  Then I used the scale feature and came up with different sizes and mounted them on the pump for a visual look.  Never did go any further.  I am including a 3D pdf showing different sizes.  If you have not used 3D pdf just click on the screen.  Then you can rotate the image in all axis.   I included some full size pictures also. 
I assume you have read the threads posted here, there are at least three that I recall all great information.

Makes a real nice model.

Bob

Offline crueby

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Re: Rider Ericsson expansion globes
« Reply #2 on: September 29, 2021, 12:35:59 AM »
Am I right that the globe is on the output water pipe? If so, its there to reduce pressure pulses and water hammer in the pipes. For a model that at most will be pumping water in an out of a bucket, the globe can be dummied with no effect on the engine.

Offline cnr6400

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Re: Rider Ericsson expansion globes
« Reply #3 on: September 29, 2021, 02:29:37 AM »
Carson, if you wanted to fabricate a hollow globe, there are a number of ways.

One way would be to make a cone on the lathe with a male lip or a male thread at the big end, and make a half sphere on the lathe with a matching female lip or female thread at the big end. The cone and half sphere could have the lip joint soldered together or the thread joint tightened with some sealant or epoxy. A second way would be to turn a wood buck or form to the shape of the globe, then form copper sheets over it with an overlap down the sides, to form halves that could be soldered together.  A third way would be to make a wood pattern and core box and cast the globe in aluminum or brass in a home foundry or commercial foundry. Casting is not difficult but there is skill needed, and much practice, there is a fairly long learning curve for patternmaking and casting.

Or as Chris suggested a dummy globe could be made. If you turned a globe out of hardwood on the lathe, bored to fit a pipe passed through it, that might be simplest. A few coats of epoxy and maybe some added-on zinc casting letters / part numbers glued in place and it would be very hard to tell it wasn't a real cast metal hollow globe.

Good luck with it and keep us posted of course!  :cheers:

Offline Jasonb

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Re: Rider Ericsson expansion globes
« Reply #4 on: September 29, 2021, 07:22:44 AM »
If you are going to polish the life out of them and have them bare and shiny and don't want a joint line as the solder tarnishes then I would start with a bar in the lathe and drill out tapping side for the threaded nipple as far up as you can go then put a very small boring bar or endmill into the toolpost and make a series of tapered boring cuts offsetting the topslide angle more each time.  Then tap and turn the outside. Finally use the thread to draw it into a holder so you can round the top off. This would give a reasonable size void without the need for joints.

If you are going for painted pipework and fittings then a two part one will be a lot easier to make.

Online Jo

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Re: Rider Ericsson expansion globes
« Reply #5 on: September 29, 2021, 08:46:28 AM »
On the full sized engines there are two of these water hammer globes:

1, On the inlet (top of the water jacket) - this captures air coming up the feed pipe and reduces any pulsing from the pump ramp when it rises.

2, On the output from the pump - this, as Chris said, is there to reduce the peak pressure imposed on the output water pipes and to hopefully minimise broken pipes.

On your model they are too small to be functional ( except if it was feeding a pressurised boiler and then they would probably reduce the water volume going into the boiler) so you can leave them solid  :-X


Bill Lindsey did a two part build for his air chambers: https://www.modelenginemaker.com/index.php/topic,328.msg12062.html#msg12062 I never fitted any on mine as I decided they would get in the way and probably easily damaged  :-\

Jo

Enjoyment is more important than achievement.

Offline Jasonb

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Re: Rider Ericsson expansion globes
« Reply #6 on: September 29, 2021, 09:24:14 AM »


Bill Lindsey did a two part build for his air chambers: https://www.modelenginemaker.com/index.php/topic,328.msg12062.html#msg12062 I never fitted any on mine as I decided they would get in the way and probably easily damaged  :-\

Jo

I thought Bill's were from one solid piece and just drilled and tapped

Also thought the incoming one had a low vacuum created as the piston drew in water and that is what damped the flow, The outlet builds up a low positive pressure which does the damping. If the inlet one were there to trap air you would need a valve of some sort on the top to vent the air as required otherwise it would fill with air and be no further use.
« Last Edit: September 29, 2021, 09:30:38 AM by Jasonb »