Stuart Oilfield pump

[Robert DoddsParticipant @robertdodds43397]

Hi,

Is anyone building or has built a Stuart Oilfield pump to the as supplied detail drawings?

I’m nearing completion and find the beam stroke at approx 2 7/8″ is more than the pump likes. The pump piston pops out of the top of its body at the top of the stroke.

In the 1980s ME did an article on Neddy based on the beam frame but they used a much different pump (maybe Tom Walshaw knew something.)

I can think of ways out of the problem but would welcome views on previous attempts

Bob Dodds

[Robert DoddsParticipant @robertdodds43397]

[Geoff Walton 1Participant @geoffwalton1]

Hi Bob

I'm new to the forum from Australia. A young model engineer in the UK is building [machining] an oil pump for me and I wonder what the fix was for this stroke problem

Hope to hear from you

Geoff

[FMESParticipant @fmes]

Hi Bob

Can you see anything obvious from this hastily grabbed Youtube video? **LINK**

[Neil WyattModerator @neilwyatt]

I was going to suggest the Neddy series, but obviously not.

Could you extend the piston down through the base of the pump – a crude bodge, I know.

Neil

[Robert DoddsParticipant @robertdodds43397]

Geoff and Lofty
After 3 years+ I had come to the conclusion that I was alone on the planet with this Nodding Donkey but they do say "Never give up hope"
My research back in 2011 found Alan Dake, author of the video and collector of model engines, whom I spoke to and it was clear that his model had subtle differences around the horse's head. My detail shows two clamp bars for fastening the wire links and the lower one fouls the horizontal guide bar, preventing full rotation of the mechanism.
Alan's version does not have or use that lower clamp. However he didn't have an in depth history as it was an acquired model rather than being home built.
At the end of the day the pump part is a bit of a compromise since in working practice the Nodding Donkey , also known as a Sucker Rod Pump did its work with the wires in tension, pulling oil UP the well tube whereas our model works on the down stroke, pushing the wires and only working as a model by virtue of the relative stiffness of the wires.
See http://web.mit.edu/2.972/www/reports/sucker_rod_pump/sucker_rod_pump.html for more detail of the working principles.
My other concern was regarding the slip motion at the top of the pump.

The pump's max stroke is 1 7/16" and there is 1 13/16" slip motion above that. I measure about 2 7/8" for the head stroke( if you disregard the offending clamp ). The upper pump body, which contains the slip mechanism is just 1 13/32" long so on each stroke the little cross pin pops out of the top of said body and has to find is way back in on the down stroke. No lead ins or chamfers are indicated and it is probably a bit much to expect a 3/32" pin to stay a press fit for very long. Some sort of retaining cap needs to be fitted on the piston slide to act as retainer and guide for the pin as it transits across the mouth of the upper pump body..
Knowing someone else is out there with one of these may spark me back into actively working on it and finalising a solution for the cross pin on the pump..

Regards

Bob D

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