Question about black rubber washers on Optimus 535?

Discussion in 'Stove Forum' started by Doc Mark, Nov 12, 2018.

  1. Doc Mark

    Doc Mark SotM Winner Subscriber

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    Greetings, All,

    I am in the midst of fettling TWO Optimus 535 stoves, one is a kero 535, and the other a 535A Meths version. I am blessed to have them both, and am currently waiting for some parts I needed, which I ordered from Mike at The Basecamp. Hopefully, they will arrive soon, and then both stoves will be ready to reassemble and test!! On the kero 535, I found two large, black rubber washers, on the ends of the tank mounting studs, tight up against the fuel tank, one on each side. Are you owners of 535's familiar with these? They appear to be made of Nitrile rubber, or something similar, and look to be used to cushion the fuel tank as it's mounted in the 535 stove body, and the washers and nuts tightened on each end.

    My question is this: Am I correct in thinking this washer is made of Nitrile rubber, or is it some other substance? I'm going to punch out four new ones, and want to make sure I use the proper rubber. The original ones that came with my kero 535 are still somewhat pliable, but are getting a bit brittle in some areas, so replacement seems like a good thing.

    Any advice as to what rubber to use, if something specific is needed, will be appreciated. Thanks, very much, and God Bless!

    Every Good Wish,
    Doc
     
  2. kerophile

    kerophile United Kingdom SotM Winner Subscriber

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    Hi @Doc Mark , you are fortunate to have not one, but two of these great Optimus No.535 ranges. They are excellent cookers

    I checked on my A/B BAHCO Primus No 535, which is an earlier model than yours and the fuel tank has plain, unthreaded studs on its ends. These studs engage in and slide on shaped slots/tracks, which are an integral part of the white vitreous-coated stove case. The tank is then just held in position by gravity. Later tanks had threaded tank studs with a a nut and washer to lock the tank in the frame

    There is a parts diagram and listing for your Optimus version of the Op.535 in this post:

    https://classiccampstoves.com/threads/1972-optimus-household-stoves-ranges-catalogue.126/

    Please can you check against your Op 535 ranges. Can you see the parts you describe for the tank?

    Alternatively, there are some good photos of a stripped-down Pr.535 here:

    https://classiccampstoves.com/threads/restored-primus-535.35302/

    There is of course no indication of the compound used for the “rubber” washer, but I believe that the service environment is relatively mild, not very hot, little or no vibration, and only a slight chance of contact with alcohol or kerosene fuel.

    I believe that Nitrile would be adequate and Viton probably over-kill.

    Best Regards,
    Kerophile.
     
    Last edited: Nov 12, 2018
  3. Doc Mark

    Doc Mark SotM Winner Subscriber

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    @kerophile , Good Morning, George,

    Many thanks for sharing those links, and your thoughts about these rubber washers. I had perused the parts list before, and came up empty, not seeing anything that resembled the two washers on my kero 535. I wonder if some previous owner popped them on there, just to cushion the tank ends from the installation hooks on the stove body? In any case, with your comments in mind, I'll proceed with my original plans to replace the washers in question with some out of Nitrile sheeting. Should work a treat, me thinks!

    I do hope any other 535 owners who's stove has these rubber washers would add their comments to this thread. If no other owners have ever seen such a washer on these stoves, I think it may be safe to assume that these are something added-on later, and were not OEM parts from Optimus. @Staffan Rönn , Staffan, do you have any input on this question? During your tenure at Optimus, was a rubber washer used on the tank bolt ends, to cushion the fuel tank when installing it into the stove body?

    For clarification purposes, here are a few photos of the washer we're discussing:

    DSCN8743.jpg
    They install thusly, on the fuel tank mounting studs:

    DSCN8744.jpg

    Then, the metal washer, and nut are added to hold the fuel tank ends tightly into the mounting slots on the stove body.

    DSCN8745.jpg

    And, another shot, with flash, in case it's needed:

    DSCN8746.jpg

    You can easily see indentations on both sides of the rubber washer, one matching up to the small raised circle of brass around the mounting stud, and the other side matching up the slots into which it was installed and held fast by the metal washer and nut. I hope that helps, if anyone was having a hard time visualizing the setup on my Optimus 535. Thanks for any others who have stoves with these washers, if there are any of you out there. Take care, and God Bless!

    Every Good Wish,
    Doc

    PS George, special thanks to you, my friend, for always sharing excellent information, and your very experienced comments with everyone! You, Sir, are a good man, and a stalwart here at CCS!! Thanks for all you do for your fellow Stovies!!!
     
  4. gideon

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    possibly this can be better
    304-stainless-steel-serrated-lock-washer-internal.jpg
     
  5. dsk

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    Hi Doc
    Mine has no threads and nuts, only those studs sliding in as @kerophile mentioned. since these not are in direct contact to fuel, the material is of less importance, and could probably be of felt or any other soft material. Use what you have.

    dsk
     
  6. Staffan Rönn

    Staffan Rönn SotM Winner SotY Winner Subscriber

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    @Doc Mark
    Hi all. I checked quickly my Optimus 535, and it has the same design as yours Doc. I have the rubber seal type of flat packings, see pictures below. Like mentioned above, nitrile should be perfectly fine for this purpose. I'm not even sure Viton was invented back then...

    It's not unusual that there were changes in designs over the years, so there could well be units without this type of fastening to the enameled frame. Possibly the part you are looking for is 91174 in the parts diagram in the 1972 catalogue.

    I don't know from which year my stove is. I just quickly took some mobile shots without dismantling the stove, but I think you can see the arrangement with a threaded stud, nut and flat packing.

    Happy fettling!!
    .
    IMAG7315.jpg

    IMAG7316.jpg
     
  7. kerophile

    kerophile United Kingdom SotM Winner Subscriber

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    Hi @Staffan Rönn . I too thought that part # 91174 might be the rubber washer Doc was looking for. However, it is quite clearly intended for use with #14816 Nut for support bar and #11590 the lock nut. As you know, the support bar is at the front of the stove, whereas the tank is at the rear.
    Is it possible that # 91174 was also used on the tank supports?

    Best Regards,
    Kerophile.
     
  8. Doc Mark

    Doc Mark SotM Winner Subscriber

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    Good Morning, @Staffan Rönn , @kerophile , @dsk , and All,

    Staffan, many thanks for responding to my question, and since yours is the same as mine, I believe that these came that way from Optimus. Personally, I think that the Nitrile washer to cushion the tank a bit, makes for a more from mounting, without scoring up the fuel tank. So, I'll punch out a could of gaskets, and go for it on both of my 535's!

    George, your thought about part #91174 seems credible. However, the first 535 that I got does not seem to have that gasket installed. I'll check again, just to make sure I didn't miss it, or just forget about it being there. Either way, I can also punch out a new gasket for that area, as well, as I have plenty of Nitrile rubber sheets, and that would be a great use for them.

    Dag Ståle, thank you for your comment, as it always great to hear from you! I didn't consider felt, but that's a good idea, too. But, since I have the Nitrile, and don't use if for fuel cap gaskets, like I used to, I might as well use it for projects like this. Best to you and your family!

    Thanks, again, to you all for your excellent suggestions, comments, and information! Now, as soon as my box of parts arrive from The Basecamp, I'll be able to complete fettling both stoves, then test them to see if I and blessed with the "Blue Flame" of success!!! Take care, and God Bless!

    Every Good Wish,
    Doc
     
  9. Rif

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    G'day Doc,

    I intend to pique your interest Doc with some pics of what I suspect to be a very late 535 albeit Primus.

    I just now came to the site after quite a spell away, having just recently acquired said stove.

    Spotting your thread here, I went out to the garage to see what my latest 535 purchase had by way of tank washers, in order to offer another answer to your question assuming you valued different perspectives from actual owners.

    I was surprised to see the tank wasn't held in with a washer/nut arrangement but rather a clip methodology I've not seen done before with the 535 stoves.

    As you can see, it appears they skimped on the brass when it came to the tank.

    I grabbed it feeling unwilling to fire up my unused one which I've managed to hang onto.
    Whilst not in quite the same league as regards the mint one, its still a tidy unit and appears to be a great runner.

    I'd previously shown pics of my acquisition of a unfired 535 in thread: https://classiccampstoves.com/threads/my-primus-535-purchase.33030/

    I intend to unpack that one to have a look at what might be the washer arrangement but likely in the morning.

    The pics are with a phone I'm unfamiliar with being another recent purchase so are somewhat a roll of the dice.

    IMG_0616.JPG IMG_0617.JPG IMG_0618.JPG IMG_0619.JPG IMG_0620.JPG IMG_0621.JPG
     
  10. Doc Mark

    Doc Mark SotM Winner Subscriber

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    Good Morning, @Rif ,

    Thank you for sharing your own 535 with us! Yes, I've seen the type you have, before, and I think that our member @marco5150, has one of that same type, and possibly others have that one, too. You can see his stove here, and read what others had to say about it:

    https://classiccampstoves.com/threads/primus-535-stove-alcohol.14836/

    From what I read, your type still works great, so no worries there. Thank you, again, for posting here. As an update to my own pair of 535 stoves, I've now received all the parts, bits, and bobs, that I need to complete the pair of them, but have not had the time to do so. Hopefully, after Christmas I can get them both together, and will post them in the Stove Reference Gallery thread about them. Have a great Christmas, and God Bless!

    Every Good Wish,
    Doc
     
  11. Rif

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    Ditto to you Doc, have a great Christmas.

    Yes indeed I'm putting the 535 to work keeping myself in hot cuppa's and have much enjoyed cleaning and getting it up and running.

    I'll look forward to seeing your update and pics in the Stove Reference Gallery.
     
  12. Peter Ockenfels

    Peter Ockenfels Subscriber

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    Doc... I am very interested to hear about your expereinces with fettling the two 535 stove. I have three of them (two kerosene and one alcool) but still havent started to work on them.
    I have some questions. For example did you remove the whole pump assemby from the tank or just took out the valve and replaced the litte rubber part and the spring. If you removed the whole thing, did you use any sealing when you you replaced it into the tank?

    All the best and be the Blue Flame with you..
    peter
     
  13. Doc Mark

    Doc Mark SotM Winner Subscriber

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    Hi, @Peter Ockenfels , Peter,

    Nice to hear from you, Sir! In dealing with the pump assembly, once you disassemble the stove, that part will actually unscrew from it's mounting on the fuel tank. Then, the NRV is right there in the open, and easy to service. Is that what you wanted to know? And, when reinstalling the pump tube, I just screwed it in, with no extra sealing added. I'll let you know if that causes some problems, but in truth, in both stoves, I saw no evidence that there ever was anything added to actually seal that setup, other than tightening it down enough, which does not take much effort to achieve. More later..... have to head down the mountain to run errands, and pick up my SB from the airport!! Take care, and God Bless!

    Every Good Wish,
    Doc
     
  14. Peter Ockenfels

    Peter Ockenfels Subscriber

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    Hi,

    yes you are right, I wanted to know about the NRV and its assembly. I will start working on one of this stoves soon. I have two new Optimus burners for it. So I will check regularly if you have posted any news/infos about how you get along with it. It has to be ready for the next camping season.

    All the best and have