Aerotech G76-G delays

[MarkH]

Anyone know what delays (i.e. HDK #) are used for the G76G reloads? The delay instructions on the Aerotech site don't include G76Gs. I've got a G76G-10 and I'd like to swap the delay with one from another motor rather than drill the delay to reduce it.

 

[shreadvector]

If you phone or e-mail Aerotech, they will both provide you with the correct information (as opposed to what 'we' tell you which might be incorrect) and they will add the missing information to their website in a ridiculously short amount of time.

They are quite amazing at posting updates and correcting omissions.

 

[kelltym88]

Not going against the grain, but "drilling" a delay down is really not a big deal. You could do it by hand and it only takes a minute. Of course, if you want to use it for something else... Just my .02 cents, or in todays economy .005.

 

[Garoq]

If you phone or e-mail Aerotech, they will both provide you with the correct information (as opposed to what 'we' tell you which might be incorrect) and they will add the missing information to their website in a ridiculously short amount of time.

They are quite amazing at posting updates and correcting omissions.

I will be revising the HDK instructions today.

 

[Garoq]

If you phone or e-mail Aerotech, they will both provide you with the correct information (as opposed to what 'we' tell you which might be incorrect) and they will add the missing information to their website in a ridiculously short amount of time.

They are quite amazing at posting updates and correcting omissions.

The HDKs for the G76G reloads are as follows:

G76-4G: HDK-15 (delay P/N 03203 .375", spacer P/N 03059 .375" red)

G76-7G: NEW HDK-25 P/N 43525 (delay P/N 03208 .469", spacer P/N 03057 .282" silver)

G76-10G: HDK-19 (delay P/N 03212 .562", spacer P/N 03053 .188" magenta)

A revised set of HDK instructions will be uploaded to the AeroTech site soon.

 

[Garoq]

The revised 29mm HDK instructions are now available for download from the AeroTech Resource Library.

 

[jimzcatz]

I drill mines,why buy delay kits???

 

[MarkH]

I drill mines,why buy delay kits???

Never tried it. Guess I don't trust my accuracy in removing seconds 1/32 " at a time.
Thanks Gary.

 

[RKT_ROB]

I am looking for an HDK-25 delay kit to change a G76-4 to a G76-7. I have tried my traditional vendors with no luck (most only go up to HDK-24). Any referrals for sourcing? Thnx- R_R

 

[rcktnut]

I think they forgot to make them, really!!! They were supposed to be out about 3 years ago. I think your only choice is to get the HDK-19 and drill it to 7 seconds.

 

[RKT_ROB]

RCKTNUT,

Thnx- why not an HDK-20 which is for a G64-7. The burn time of the motor (G64 vs. G76) is less than a tenth of second difference. The coding of these delays and the motors they are specific to is nonsensical. Why are they specific to a motor and not just specific delay times? Rocksim recommends optimal delay times based on the difference between the time to apogee minus the burn seconds of the motor. Just give me the the right delay number of seconds and I will make it work with my motor application (given the case and closure are the same). Makes no sense. R_R

 

[michigander]

Buy the #19 pack and drill to 7 sec ?

 

[dhbarr]

Anyone have an opinion on an hdk23 in a g76? My hunch is that it will be like a 14sec delay ; if all else fails I'll just order one and find out ( on the test stand )

 

[RKT_ROB]

Thnx - it looks like the consensus is HDK-19 and drill. That may be the best option anyway since it gives me flexibility. I still do not understand the naming convention and logic behind these HDK/RDK kits and why they just can't be specific delay times that can be used with different motors in the the same case/closure arrangement. R_R

 

[dhbarr]

This had been banging around in the back of my mind for about six months, but I finally wrote it all down:

https://www.rocketryforum.com/showthread.php?136672-29-40-120-HDK-Chart-AKA-g76-Is-The-Best&p=1627193#post1627193

It's a fairly logical relationship of increasing delay grain depth == increasing HDK number, but then they had to go back and add the 24 & 25; and they skipped XX, YY, and ZZ.

HTH!
-dh.

 

[Rex R]

one problem with doing a mix and match to get the right delay time, chamber pressure varies with each reload, and since delay burn rate during the thrust phase is dependent on chamber pressure...a 7 sec delay for a blackjack motor might well be a good bit shorter with a blue thunder reload.
Rex

 

[dhbarr]

one problem with doing a mix and match to get the right delay time, chamber pressure varies with each reload, and since delay burn rate during the thrust phase is dependent on chamber pressure...a 7 sec delay for a blackjack motor might well be a good bit shorter with a blue thunder reload.
Rex

Yup, I believe the chart shows exactly that. Post-burnout all but the slow .750 (hdk23) should behave exactly the same, though. Since AT says the delay composition is the same, they all differ from each other solely on length.

Further, since the cert authorities (and hundreds of fliers) have already cross-checked the first two or three values for us, we can be pretty confident of linear increases on the right side of the chart.