Motor delay adjustment

broofa

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Also, how long is an AT "X" HPR delay? e.g. j460t-x, j800t-x, k1100t-x

This sheet says "X = approx. 18 seconds"

For CTI in 29mm and 38mm, are there certified motors with shorter than 13s default delay? I can't think of any. I wish I knew of a guy with a big searchable database of all the motors....

These are all of the Cesaroni motors with adjustable delays of < 13 seconds: (Including 24mm motors because I believe they can be adjusted using the PRO38 DAT tool as well, using this adapter)
  • 55F29-12A (Pro29-1G)
  • 73F30-6A (Pro24-3G)
  • 56F31-12A (Pro29-1G)
  • 53F32-12A (Pro29-1G)
  • 41F36-11A (Pro29-1G)
  • 75F51-12A (Pro24-3G)
  • 57F59-12A (Pro29-1G)
  • HP139G107-12A (Pro24-6G)
  • HP142G117-11A (Pro24-6G)
  • 128G185-12A (Pro38-1G)
  • 143G33-9A (Pro29-3G)
  • 127G46-11A (Pro38-1G)
  • 159G54-12A (Pro29-3G)
  • 108G57-12A (Pro29-2G)
  • HP144G65-8A (Pro24-6G)
  • HP131G84-10A (Pro24-6G)
  • 84G88-11A (Pro29-2G)
  • 216H118-12A (Pro29-4G)
  • 176H123-12A (Pro29-4G)
  • 266H125-12A (Pro38-2G)
  • 217H135-12A (Pro29-4G)
  • 268H140-11A (Pro29-5G)
  • 312H160-12A (Pro29-6G)
  • 282H399-12A (Pro29-6G)
  • 186H42-10A (Pro29-4G)
  • 234H53-12A (Pro29-5G)
  • 168H54-10A (Pro29-3G)
  • 168H87-12A (Pro29-3G)
  • 164H90-12A (Pro29-3G)
  • 567I125-10A (Pro38-5G)
  • 465I150-11A (Pro54-1G)
  • 395I55-9A (Pro38-3G)
 

heada

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Someone previously said CTI allows for a minimum of 2sec delay. So of that list, only 8 could be reduced to less than minimum (10sec and less)

Just don't reduce it to less than minimum. 2sec for CTI and 4sec for AT. I don't recall seeing a minimum delay for Loki.
 

heada

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Do you have more info on the details of adjusting Loki delays?

This post has some info, but again refers to variances between motors: https://www.rocketryforum.com/threads/loki-cti-dat.96381/
The Loki tool is the CTI tool with a Loki sticker on it. It labels the time removals as "L", "M", "S", "XS"

The Loki product page lists the reload delay ranges. For example, the 38mm G80W is 5 to 17 seconds. Only 38mm reloads have ejection delays. 54mm and 76mm are plugged only.

 

kramer714

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Just jumping in,
First of all, John, thanks, a lot, really.. Thrust Curve is a great resource and I know you have put lots of time into it.

Secondly, the point of the motor burn vs delay is lost on a lot of folks. The time for the delay begins on ignition (see note), not at motor burn out. A 6 second delay is 6 seconds from ignition. For a fast burning motor, it is within the error of the delay, but for long burning motors the delay time after burnout may be significantly less. One reason why H13 are plugged...

Note - Chuffing. The delay starts at ignition is PAINFULLY obvious when a motor chuffs, it is possible that the delay grain is burning during the entire time the motor sits on the pad and chuffs. I personally have had high speed deployments due to this.

Mike K
 

waltr

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Correct, delay burns during propellant burn time. However, it is not 1/32" per second during the motor burn. I'm sure this is due to the pressure that causes the delay to burn faster.

Once propellant burn out then delay burns at 1/32" per second.

I've been do dual deploy with 24 & 29mm AT motors. I have been setting the delay for 1-3 second longer than calculated time to apogee. The motor ejection is just a back-up to the altimeter's drogue deployment.
 

Rocketjunkie

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With my 18 mm motors, I use my standard 40-40 delay mix. In a core burner (1 sec burn) with a 1/2" long delay grain I get 10 sec. In a D grain (3.5 sec burn) I need a delay grain 3/4" long to get the 10 sec. The delay burns MUCH faster under pressure than otherwise.
 

JohnCoker

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Secondly, the point of the motor burn vs delay is lost on a lot of folks. The time for the delay begins on ignition (see note), not at motor burn out.
Because of the legacy of (end-burning) BP motors, delays are always counted from burn-out. This means that delay grains in core-burning motors actually are designed to burn longer because as you suggest they start burning at the same time as the motor grains.
 
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