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  1. #1

    Seal Disk Wont Fit

    Ordered case liners for an experimental motor, but the seal disk for my Dr. Rocket motor wont fit at all, suggestions?


  2. #2
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    The seal disc only fits AT liners. If you use any other; you are on your own.
    What size hardware are you talking about?
    If it's 38mm: Just buy a end burner style forward closure and don't use the seal disc.


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  3. #3
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    ^^^

    That.

    If you didn't order from the RCS website, the liners will probably be the wrong ID/OD for the aerotech hardware.
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  4. #4
    what exactly is an endburner closure? I have a plugged closure with a delay well... will that work? Are there substitutes for the seal disk (ie fender washers?)

  5. #5
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    If you look at the motor assembly drawing pdf's on Aerotech's website of the I49N and I59WN, they show the endburner-style closure. It has no provision for a smoke grain, and I have no clue where you might obtain one. And I don't think that it would make the seal disk unnecessary, either. Maybe use two fiber washers or machine your own seal disk to fit the liners.
    Several rocket motors burned this year.

  6. #6
    Unfortunately, since I am currently under 18, and will not be 18 until about a week before my permit flights and thus my first experimental flight the next day, I am unable to order from RCS... Under recommendation of other in the experimental motor field, I am using a fender washer for the fiber washer by the nozzle as a subsititute for the fiber washer. Could two fender washers with High-Temperature RTV sealant between the liner and the casing, and between the wasters and the liner, with the liner firmly pressed against the washers work?

  7. #7
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    Quote Originally Posted by rpmaurer View Post
    Ordered case liners for an experimental motor, but the seal disk for my Dr. Rocket motor wont fit at all, suggestions?
    But it(seal disc) does fit inside the motor case? The seal disc does not go IN the liner, it sits at the TOP of the liner..
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  8. #8
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    Quote Originally Posted by Pantherjon View Post
    But it(seal disc) does fit inside the motor case? The seal disc does not go IN the liner, it sits at the TOP of the liner..
    John the FIBER seal disk fits on TOP of the liner... a METAL seal disk fits INTO the liner with an O-ring.. so it depends which one you are using..
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  9. #9
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    The seal disk was used to assist blowing out the forward closure o-ring.(from what i know of it...)

    My guess is that endburn style will not fix your problem, as it does not shoulder the liner, and an end burn has an inhibited burn area agains the insulator, so no chance of blowing out the O-ring.
    http://www.aerotech-rocketry.com/cus...49n-p_assy.pdf


    aerotech closures do not sholder the liner such as snap ring cases do. so the seal disk provides that benefit.

    if you look at some Kosdon cases, he made some stuff that the liner did not shoulder the FC or the Aft closure/nozzle... But the o-rings are not exposed to burning surfaces...

    So the chances are that you may not need a seal disk period... put a good amount of grease in the cavity, and use a fiber washer to protect the o-ring.

    other option, is to have someone make you or modify a seal disk to fit the liners your using... place grease between your seal disk, and o-ring as a bit of insulation security...
    http://www.aerotech-rocketry.com/cus...50w-l_assy.pdf

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  10. #10
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    Quote Originally Posted by rpmaurer View Post
    Unfortunately, since I am currently under 18, and will not be 18 until about a week before my permit flights and thus my first experimental flight the next day, I am unable to order from RCS... Under recommendation of other in the experimental motor field, I am using a fender washer for the fiber washer by the nozzle as a subsititute for the fiber washer. Could two fender washers with High-Temperature RTV sealant between the liner and the casing, and between the wasters and the liner, with the liner firmly pressed against the washers work?
    Fender washers if made of steel is not allowed and an extreme danger.

    Since you are a minor you should seek some major, assistance from people with experience.

    "Dad, I am going to put a big motor in this skinny rocket... its going to disapear like a ghost!!!.....

  11. #11
    Seal disk is aluminum, fits in casing not in liner. And thanks will seek assistance, as I have been for the five years I have been doing experimental rocketry. I am new to using reloadable casings in experimental rocketry, which is why I am here asking questions. thanks for advising me not to use metal washers.

  12. #12
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    Quote Originally Posted by rpmaurer View Post
    Seal disk is aluminum, fits in casing not in liner. And thanks will seek assistance, as I have been for the five years I have been doing experimental rocketry. I am new to using reloadable casings in experimental rocketry, which is why I am here asking questions. thanks for advising me not to use metal washers.
    I am certainly not trying to stave of the inspiration or belittle your ability.

    the majority of the aluminum used in experimental rocket motors and commercial hardware is 6061 aluminum.
    For good reason, youll see this isnt even an aerospace aluminum, just a nice good industrial aluminum. its properties lend to a failure mode that is better in my opinion.

    i have been into highpower rockets for about 5 years, and making motors just over a year. what your trying to do with this system is hold the ends on... "with threads" protect the threads from damage of hot gasses and seal the pressure vessel with "o-rings" and protect the orings from the hot gasses with liners, or sealdisks, or closure/nozzle material..
    The liner serves to inulate the motor case from the burning grains....

    I suppose you have gotten that far, and is how you got the liner...

    If this was ME... there are many ways you can make your own seal disk.
    1 way is to go buy gasket material... the fiber stuff. cut mutliple rings together and epoxylaminate them together use 2 hard boards with some vice grips and laminate till its 1/4" thick or so... .. this could be epoxied into your liner and should work, you dont need to put a hole in it as the seal disk has, since that is incase there is a delay element for an ejection charge...
    i would then put some rtv or such around the inside of the liner at the insulator...


    you should look into snapring style cases, a lot of us use them, as the closures house the o ring where insulators and seal disks are not ever required.
    I machine a lot of my own nozzles, and other stuff, so i like the snap ring stuff... i cannot cut threads that well so the snap ring stuff works great for my needs....

    clay

    "Dad, I am going to put a big motor in this skinny rocket... its going to disapear like a ghost!!!.....

  13. #13
    No problem, I may have over reacted a bit, I fully appreciate all advice and input. I found a website that sells Aerotech liners (albeit through rcs, but they were cheaper) and coincidentally hard fiber washers, which solves both problems. The incorrect liners are being returned tomorrow with a full refund. Thanks for the info and opinions from everyone, i'm sure I will have more questions as time goes on.

  14. #14
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    I bought mine from Common Wealth displays a bout 2 years ago. I don't fly many commercial motors these days but still have the hardware....

    I've never actually tried making a motor for AT styled hardware.

    AT designed their stuff to compress the o-rings where Kosdon and any other the snap ring hardware it's different.


    JD

    Quote Originally Posted by CarVac View Post
    If you look at the motor assembly drawing pdf's on Aerotech's website of the I49N and I59WN, they show the endburner-style closure. It has no provision for a smoke grain, and I have no clue where you might obtain one. And I don't think that it would make the seal disk unnecessary, either. Maybe use two fiber washers or machine your own seal disk to fit the liners.
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  15. #15
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    Did I miss something with this thread? I thought you have to be level 2 and a member of Tripoli to be legal for experimental rocketry?
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  16. #16
    To FLY a research motor, yes a level two is required... but to experiment for personal on on your own property doesn't require any permit.

  17. #17
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    Quote Originally Posted by gldknght View Post
    Did I miss something with this thread? I thought you have to be level 2 and a member of Tripoli to be legal for experimental rocketry?
    Only to launch at a Tripoli sanctioned research launch. There are other places, methods and launches that allow experimental launches that are not associated with Tropoli.
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  18. #18
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    ^^^

    I now attend a test site that launches both commercial and home made solid, hybrid, and liquid motors.

    A friend of mine will be launching a commercial M, and he asked me if any L3 people would be there to "legally" assemble the motor. I explained that since it was not a Tripoli/NAR launch, and the waivers/permissions granted to the site allowed for both static testing and flights of all motors under Class 2 requirements, there was no need.

    If there are any such groups in your area, search them out. This group (FAR) has a multitude of test stands and bunkers, in addition to the bathrooms, storage containers, and hanger they have on site for both rockets and people to work comfortably.

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