Aerotech universal delay

Discussion in 'Propulsion' started by g zilla, Jan 25, 2015.

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  1. Jan 25, 2015 #1

    g zilla

    g zilla

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    Tried to use a new never used drill delay and tried to shorten -8 seconds off, and the tip of the bit barely touched the delay grain got my friends delay tool out and his drill bit extends about 1/4" longer than mine.What is length the drill bill is supposed to be? I see a set screw to adjust it how long from face to tip.
     
  2. Jan 25, 2015 #2

    iqsy59

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    Hi Gary. Are you attempting to drill a DMS delay, or RMS? If RMS, Aerotech has a specific drilling tool (RDDT). I inadvertently tried to use the new universal tool on a RMS delay (I have both) but it was quickly detected because the diameters were different. I can't speak to the drill length because I never got that far!

    Cheers,
    Michael
     
  3. Jan 25, 2015 #3

    g zilla

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    DMS delay an H-115 single use withthe universal drill delay.The same one that came with the motor. Mine is approx. 2.030 tip to base no washer.
     
  4. Jan 25, 2015 #4

    cavecentral

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    -8 seconds is 8/32 or 1/4". So guessing you buddy's is correct if yours didn't do anything.
     
  5. Jan 26, 2015 #5

    gltruett

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    It looks like yours needs adjusting. Mine which worked well for me goes 2.1670 tip of drill bit to outer base, 2.0845 with the washer in place which makes it easier to measure with calipers.
     
  6. Jan 26, 2015 #6

    timbucktoo

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    Can the Aerotech RMS DDT tool be used with the hobby line reloads (29/40-120)? I was under the impression that it was but both motors I tried to drill out the delay seemed to have no effect.
     
  7. Jan 26, 2015 #7

    abeckort

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    Mine is 2.1775 to the outer base and 2.110 with the washer in place.
     
  8. Jan 26, 2015 #8

    jimzcatz

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    All AT delays, single use or RMS. 1/32nd inch for each second taken off. If SU, you need to find the top of delay grain and go from there. Been drilling delays for over 20 years with nothing but a drill bit.
     
  9. Jan 26, 2015 #9

    mikeyd

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    If you have an RMS delay tool as well, or a friend with a delay tool, borrow their washer, loosen the set screw, stack both washers on the tool, and set it on the delay assembly , at the 4second side. Let the drill bit just touch the delay grain and tighten the set screw.
     
  10. Jan 26, 2015 #10

    rharshberger

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    The 18mm to 38mm RMS Delay Drilling Tool (RDDT) can be used with all Hobbyline cases and AT RMS 29mm and 38mm cases (I use the RDDT on my Hobbyline 24 and 29mm cases all the time). If I understand correctly the Universal Delay Drilling Tool (UDDT) is for Single use, DMS and EZ-Load type motors/loads, but it may be only for DMS motors.
     
  11. Jan 26, 2015 #11

    mikeyd

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    The UDDT, can not be used on regular delays, unless you make some kind of spacer for it. Unlike the Standard Delay Drilling Tool, The Universal Delay Drilling Tool, is used from the top down, so they have to account for the depth of the delay well, before the drill bit hits the top of the delay grain.
     
  12. Apr 17, 2019 #12

    amiliv

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    If you have RMS delay drill tool (or a friend who has it), you can simply calibrate drill bit length for the universal tool directly in the RMS tool just as if you were calibrating the RMS delay drill tool. The body of the universal delay drill tool is shorter than the body of the RMS delay drill tool. The difference in length of the two tools is the depth of the ejection charge well on DMS motors (from the top of the well, to the top of the delay element). In other words, the distance between the base of the knob and the tip of the drill bit should be exactly the same on those two tools. I.e. take the drill bit from universal tool, insert it into RMS tool (without washer!) and the tip of the drill bit should be flush with the other end of the RMS tool. If it is not, adjust it.

    Or if you don't have RMS tool, find out the length of the RMS tool's body (I measured it yesterday, but forgot what it was, can add that data point when I get back home), and set the length of the drill bit from the base of the knob (without washer) to the tip of the drill bit to be that length.

    Confirmed the above with the AeroTech support.
     
  13. Apr 21, 2019 #13

    amiliv

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    The length of the RMS tool body is 2 5/32", so that should be the length of the drill bit in both RMS and DMS (universal) tools without the washer. Or 2 3/32" if you want to measure with the washer.
     
  14. Apr 21, 2019 #14

    crossfire

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    I was told by a AT Dealer my universal tool will work for DMS and RMS reloads.
     
  15. Apr 21, 2019 #15

    pyrobob

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    Despite the name, the Universal Delay Drill Toll isn't, well, Universal. Without modification, the UDDT is for DMS and the RDDT is for RMS.
     
    Steve Shannon likes this.
  16. Apr 21, 2019 #16

    crossfire

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    Maybe I am thinking universal for the RMS EZ like the J520?
     
  17. Apr 22, 2019 #17

    pyrobob

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    Excellent point crossfire, the UDDT will in fact work on the J520W RMS. Take a look: http://prntscr.com/nf269p
     
  18. Apr 22, 2019 #18

    amiliv

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    I'm speculating AeroTech intended to transition from classic RMS (reusable delay bulkhead) to RMS-EZ (disposable bulkhead with pre-installed delay element, see pics here). In which case "universal tool" would be universal. But that obviously never happened. Until that happens (if it ever happens), you still need RMS delay drilling tool for old-school RMS delay elements.
     
    Last edited: Apr 22, 2019
  19. Apr 22, 2019 #19

    beeblebrox

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    Y'All are making the process more complicated than necessary. Remember one thing: The delay material burns at approx 1/32" / sec. If adjusting a disposable motor, carefully remove whatever cap is over the black powder charge, save the cap and black powder. Some DMS motors have a stainless steel washer in there, that is to constrict the hole below the black powder so it won't blow out the nozzle, don't loose that! AT 24mm motors don't have that washer for example. Put a 1/8" drill bit in to motor touching the delay material. Make a masking tape flag square with the end of the case...a depth gauge. Cut back the tape for how much delay to reduce. The photo example is -4 sec. hand twist the drill into the delay material until the flag just touches the end of case. then twist the drill back and forth without pushing in anymore to get the loose stuff out. Reinstall the washer if applicable, then your powder. If the delay material is directly available, such as with a reload kit, drill into the delay on the combustion chamber side of it. if flush just make your tape flag using a ruler. if recessed, Typical for CTI reloads. use same method as the bulkhead end way. It is best to drill the combustion chamber side whenever possible, due to delay material burning after ejection when you drill the charge end. This can burn your rocket a little bit (The hibachi effect). delaydrill.jpg drill2.jpg
     
  20. Apr 22, 2019 #20

    amiliv

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    Yup. However the reason I prefer the tool to the drill bit wrapped in masking tape is that the tool provides hard stop to prevent accidental overdrilling. 1/32" is very tiny.
     
  21. Apr 22, 2019 #21

    pyrobob

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    I believe this is correct :).
     
  22. Apr 23, 2019 #22

    beeblebrox

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    I believe you are correct also, my previous suggestion, was to avoid the need to buy another tool and neither of those universal tools work on 24mm or smaller motors. The delay material is dense enough that it is not that difficult to use my tape method...been doing it for 30 years...
     
  23. Apr 23, 2019 #23

    pyrobob

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    Yeah, I still kick it old school and use a tire tread depth gauge and small drill bit on some fixed delays from time to time :).

    [​IMG]
     
  24. Apr 24, 2019 #24

    jnobels

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    Aerotech delays can be so variable (in my experience anyway) that absolute precision here isn’t really that critical. After adjusting a couple dozen RMS delays with the tool, you get a pretty good feel for how large a dimple you need to drill to get reasonably close to the result you desire and what 1/32 looks like.

    Adjust conservatively (-2 seconds if you want -3 for example) then remove a ‘little more’ material carefully to adjust by single seconds.
     
  25. Apr 24, 2019 #25

    amiliv

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    I see the variance in delays as additional reason for having repeatable consistency and accuracy. Because the errors add up. If a delay element burned 2 seconds longer, user overestimated how much delay is needed by 2 seconds, and then drilled 2 seconds too few on top of that, the deployment will trigger full 6 seconds after apogee. If it's possible to eliminate one out three sources of error, it reduces the probability of damage to the rocket (e.g. zippering).

    On a real world example, I recently had one rocket badly damaged. The delay element in an AeroTech I170 took way way longer to burn through than it should have (it's specced at 14 seconds max, it was drilled down, and I still estimated it burned for *longer* than 14 seconds), and on top of that I under-drilled about 3 seconds too few. Those 3 seconds could have made a difference how much (if any) damage was inflicted on the rocket, as the speed at deployment would have been considerably lower. Ironically, the source of that 3 seconds of user error was the delay drill tool. I used a brand new drill tool for 54mm motors, just unpacked it. I blindly assumed they come out of factory correctly calibrated (now I know they don't), because CTI tool I used in the past comes out of the factory correctly pre-calibrated (CTI tool can't even be user-calibrated, it's not an option). In my case, the tool was off by at least 3 seconds.

    In retrospect, while the hole looked plausibly deep on visual inspection, it was a bit on the shallow side. It should have raised red flag and I should have stopped right there. But it was end of the long day, assembling AeroTech reload out in the field on a hot day (not my definition of fun), and it just kinda slipped. Lessons learned there. IMO, I'd be much more likely to repeat that error with "drill bit + masking tape" than with the tool. Especially now that I learned to always double check the tool is correctly calibrated before using it.
     
    Last edited: Apr 24, 2019

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