Pump rod design <> Pumping efficiency

Discussion in 'Stove Forum' started by Odd, Dec 18, 2013.

  1. kerophile

    kerophile United Kingdom SotM Winner Subscriber

    Offline
    Joined:
    Sep 23, 2004
    Messages:
    13,108
    Location:
    Far North of Scotland
    Hi, just had another though:

    It is possible that the integrated pump piston designed for the Enders petrol stoves might serve as a direct replacement for the Optimus No.111 "O" ring piston.
    Have a look at this Post:

    https://classiccampstoves.com/threads/20506

    I do not have a spare "O" ring pump assembly to try this "fix" on and it does depend critically on the diameter and length of the reduced section of the pump shaft.

    The big advantage of the crimped leather piston assembly is that the overall length is less than original screwed assembly.

    Just a thought....

    Best Regards,
    Kerophile.
     
    Last edited by a moderator: Jul 2, 2015
  2. Odd

    Offline
    Joined:
    Oct 4, 2013
    Messages:
    667
    Location:
    Östhammar, Sweden
    That looks like THE solution for an O-ring rod conversion.

    Provided the measurements are the right ones... My O-ringed pump rod have got a reduced diameter of ~5 mm over a 7 mm length, then comes the outermost (4 mm dia) tip carrying the retainer on its ~2.5 mm length. So, all in all it's ~9.5 mm of reduced diameter(s). This would be easy to improve upon though - in a lathe - as long as the diameter of the reduced section is OK for that Enders design idea...
     
  3. kerophile

    kerophile United Kingdom SotM Winner Subscriber

    Offline
    Joined:
    Sep 23, 2004
    Messages:
    13,108
    Location:
    Far North of Scotland
    Hi Odd, I think you might have to reduce the diameter of the reduced section slightly and I will confirm the internal diameter of the "piston" tomorrow. I will also see whether I think the 7mm is enough to allow float of the Enders integrated piston.

    Best Regards,
    Kerophile.
     
  4. kerophile

    kerophile United Kingdom SotM Winner Subscriber

    Offline
    Joined:
    Sep 23, 2004
    Messages:
    13,108
    Location:
    Far North of Scotland
    Hi Odd,

    1. The Enders riveted/integrated leather pump piston produced by Sefa is for a pump cylinder of 15mm nominal bore. This compares with the 14mm bore of Op.00 or 111 pump cylinders. However the leather is flexible and it can be fitted into the smaller bore.

    2. The rear backing washer on the Enders assembly is the largest of the two and it is 13.5mm diameter.

    3. The OAL of the Enders assembly is 10.5mm of which the brass and washers account for only 5-5.5mm

    4. The bore of the Enders piston is approx.4.35mm

    5. The Enders bore is too small to fit on the standard Op. 00 and 111 pump rod. However as you say this could be reduced in diameter if you have access to a lathe.

    6. I have a pump rod in my spares box which has a reduced section of 4.25mm diameter, 11mm long (the thread takes approx 3mm of this).

    7. I mounted the Enders piston on this pump rod and got it to fit a spare Op.00/111 pump cylinder.
    It pumps well with the piston mounted either facing forwards or backwards.... I tried this because it is easier to fit a larger diameter leather piston for the first time, if the bucket is facing away from the NRV.


    I think we now have "proof of principle" and it is probably worth pursuing this idea further.

    If I were to design a direct replacement for the "O" ring piston I think I would get an Enders type piston but with two slight modifications;

    Use the smaller Sefa Pr.210/111 leather bucket.

    Use a larger riveted brass cylinder with a bore to suit the 5mm reduced section you have measured on your pump rod.


    Just thinking...

    Best Regards,
    Kerophile.
     
  5. kerophile

    kerophile United Kingdom SotM Winner Subscriber

    Offline
    Joined:
    Sep 23, 2004
    Messages:
    13,108
    Location:
    Far North of Scotland
    Hi, here are some photos of the "Sefa" Enders pump piston I used in the above experiments:

    1387715871-Enders-Pump-piston-1.jpg 1387715881-Enders-Pump-piston-2.jpg 1387715891-Enders-Pump-piston-3.jpg

    Best Regards,
    Kerophile.
     
    Last edited by a moderator: Jun 26, 2015
  6. snwcmpr

    snwcmpr SotM Winner Subscriber

    Offline
    Joined:
    Nov 16, 2011
    Messages:
    16,226
    Location:
    North Carolina
    Thank you George. I have been following this as I have an o-ring pump on a 111T (my 4th 111) that needs replacing.
    I also have a Baby Enders coming in the mail. If I order a set of these pump cups from Sefa, it will solve both problems.

    Ken in NC
     
  7. Odd

    Offline
    Joined:
    Oct 4, 2013
    Messages:
    667
    Location:
    Östhammar, Sweden
    This is interesting! As you say, we're on to something here. (I wonder if Sefa is reading? I do hope he is...)

    I checked on the nominal material diameter for cutting a thread into the outermost part of the rod; Ordinary M4*0.7 needs a minimum of 3.978 mm for a correct thread-cut while the M5*0.8 needs 4.976 mm so cutting either would be possible even though the M4 would be the prefered thread.

    Imho a threaded nut for locking this contraption in place would be VASTLY superior to the oem solution with a retainer washer pressed/seated onto the rod end... Hm, I think I need to go buy myself a lathe - Santa are you listening...?
     
  8. Leonard Newman

    Offline
    Joined:
    Aug 12, 2015
    Messages:
    3
    I've recently bought a beautiful NBU, optimus 111T. There 's problem with the unit's pump. It has a rubber disc instead of the leather cup! Where can I get a pump spindle that's already threaded so I can use that instead of the old one?
     
  9. kerophile

    kerophile United Kingdom SotM Winner Subscriber

    Offline
    Joined:
    Sep 23, 2004
    Messages:
    13,108
    Location:
    Far North of Scotland
    Last edited: Apr 28, 2016
  10. kerry460

    kerry460 Australia R.I.P.

    Offline
    Joined:
    Aug 20, 2010
    Messages:
    2,357
    G,,day .
    maybe i am missing something in these comments ,
    the BABY is 15mm the 111 is 14mm . round figures .
    the cups from Sefa for the BABY , that i have seen will not fit the 111.
    the leather cup is to large and the hole is to small to fir the 111 pump shaft .
    i am not in any way having a go at Sefas products . stating facts .

    this is why i started making leather cups to replace 111 o rings .

    it is interesting that at least two contributors to this thread have in the past made very complimentary comments about my 111 change over kit that i supplied them with

    if they are no longer happy with the performance of them , please contact me privately , as i have said i stand by my 111 cups .

    thankyou Kerophile

    thats all for now .

    cheers kerry
     
  11. Leonard Newman

    Offline
    Joined:
    Aug 12, 2015
    Messages:
    3
    to all the brothers out there, I'm new to the stove collection gallery! however, I appreciate all of the comments and postsites for keeping these valuable items working properly. I'll post a picture of my new find. thanks!