Shorten an Aerotech 24mm delay

Is there a way to shorten a delay on a Aerotech 24mm reload?
I have a pack of F24-7s, I would like to shorten the delay to like 4-5 seconds.
The local retailer seems to only carry these long delay reloads.
The cases I have are the 24-40s.

goldlizard said:

Is there a way to shorten a delay on a Aerotech 24mm reload?
I have a pack of F24-7s, I would like to shorten the delay to like 4-5 seconds.
The local retailer seems to only carry these long delay reloads.
The cases I have are the 24-40s.

Click to expand...

It's identical to the 29/40-120 delay shortening: take off 1/32 of an inch per second of delay reduction.

Use a drill bit about 1/3 of the delay diameter and drill into the delay. Don't try to cut it down.

Sent from my TegraNote-P1640 using Rocketry Forum mobile app

I use an Aerotech Delay Drilling Tool. Works great. You can shorten in 2 second increments and it can be used on 18 -38mm RMS. I didn't buy mine here but this is what it looks like:

https://www.siriusrocketry.biz/ishop/18-38mm-rms-delay-drilling-tool-667.html

https://www.aerotech-rocketry.com/

https://www.aerotech-rocketry.com/resources.aspx

https://www.aerotech-rocketry.com/uploads/02a31b31-ee1a-4d91-b134-39d6a6911463_dda_instructions.pdf

Can't find this one on the Aerotech website at the moment:

https://www.artapplewhite.com/images/vendors/rms_delay_mod_inst.pdf

goldlizard said:

Is there a way to shorten a delay on a Aerotech 24mm reload?
I have a pack of F24-7s, I would like to shorten the delay to like 4-5 seconds.
The local retailer seems to only carry these long delay reloads.
The cases I have are the 24-40s.

Click to expand...

Thanks for the help. It actually looks easy to do.
I also read that Aerotech is producing their reloads with the longest delays, then you cut them down to meet your needs.
You guys are the best!
Thanks Again!

goldlizard said:

Thanks for the help. It actually looks easy to do.
I also read that Aerotech is producing their reloads with the longest delays, then you cut them down to meet your needs.
You guys are the best!
Thanks Again!

Click to expand...

Actually you're supposed to use the AT delay drilling tool to drill them out......

Bob

shreadvector said:

Can't find this one on the Aerotech website at the moment:
https://www.artapplewhite.com/images/vendors/rms_delay_mod_inst.pdf

Click to expand...

Yes that, how to drill delays with an ordinary drill bit, used to be on the Aerotech site, and I can't find it there anymore either. Turned out I even had a drill stop already, which otherwise would had never been used. This seems more precise to me than their tool, as well -- I attempt, at least, to drill within 1/2 second, and definitely within 1 second, while their tool is in 2 second increments.

If they're really considering going to a single long delay for all motors, this should not only still be there, it should be linked from the front page! Or in their instructions, in short form. One thing about rocketry that bugs me is the way it can "nickel and dime" you, so many little things you need to buy. Not only expensive but rubs me the wrong way. Although I don't think they're actually doing that with the delays-- there's no sign Hobbyline reloads will be yet, and I think fixed delays appeal to the less experienced. (I do presume they've added some kind of drill instructions to their reload instructions for the single delay reloads, which is overdue anyway.)

bill_s said:

Yes that, how to drill delays with an ordinary drill bit, used to be on the Aerotech site, and I can't find it there anymore either. Turned out I even had a drill stop already, which otherwise would had never been used. This seems more precise to me than their tool, as well -- I attempt, at least, to drill within 1/2 second, and definitely within 1 second, while their tool is in 2 second increments.

If they're really considering going to a single long delay for all motors, this should not only still be there, it should be linked from the front page! Or in their instructions, in short form. One thing about rocketry that bugs me is the way it can "nickel and dime" you, so many little things you need to buy. Not only expensive but rubs me the wrong way. Although I don't think they're actually doing that with the delays-- there's no sign Hobbyline reloads will be yet, and I think fixed delays appeal to the less experienced. (I do presume they've added some kind of drill instructions to their reload instructions for the single delay reloads, which is overdue anyway.)

Click to expand...

There is one Hobbyline reload like that: the G138.

An easy way to do this is to take a drill bit and wrap it with masking tape at the desired 1/32 of an inch per second depth. Drill to the bottom of the masking tape and you are done (the drilled end of the delay is then placed so it faces the nozzle end of the motor). Bear in mind the + or - 20% variance of aerotech delays. Record the results of the flight for future reference in selecting delays. I usually buy the long delay hobby line reloads as you can always shorten them (not as easy to make them longer). Do not drill shorter then 4 seconds as there is a risk of it blowing through from pressure rather then burning through.

I am a poor boy so I have always just hacked them down with an Xacto knife. The certified high power model rocket scientists that supervise my uncouth activities were appalled and brought out that expensive and fancy drill. Much to their dismay I was getting better results. Now the Pad Fuhrer hacks his delays down with the knife as well, He doesn’t drill or cone, he carefully hacks out a flat surface. Drilling (hacking) AT delays is more Art than SCIENCE. OMG forgive my heresy! Different motors and delays burn at different rates and given the”20% + or – variance” it turns into a bit of a crap shoot where experience counts. Again, I apologize to the book learned model rocket scientists reading this. But the Pad Fuhrer really has it down now. He cut a G76-4 down to a G76-1 and it worked on a very odd rocket at the last launch. He cut down my H242 medium to a short on my Cosmodrome Vostok and it was perfect both times. What you do have to be careful with are those Black Jack delays, they burn real fast so cutting down a 4 could turn into a 0 or worse very easily. After three Black Jack hack jobs I have moved from a partial blow by that wasn’t enough to damage my forward closure (but fried my thin LPR tube) to almost getting it right. Still, three strikes and you are out so I have to tread carefully while under strict supervision. When the Newbies want their delay cut I just tell them to go over to the Pad Fuhrer and watch and learn.

To maintain your insurance and follow the manufacturer's instructions, you must not attempt to drill a delay down to a shorter delay time than the shortest delay time they certified. The simple reason is that if the delay gets too short, there is not enough delay material left to retain the high pressure as the propellant is burning. This can result in a cato and the malfunctioning ocket motor can make the rocket crash and cause injury and/or fire.

I'm sure you're right but I once launched my LOC Warlok (7.5", 6.5lbs) on an H242. It only reached about 500' and I needed a 2 second delay. I used the 1/32" per second rule of thumb and the delay was perfect. The chute came out right at apogee. I'm sure that was the biggest rocket ever launched at that field.

Once you get below the shortest delay offered by the manufacturer YMMV, proceed with caution, etc. :duck:

shreadvector said:

To maintain your insurance and follow the manufacturer's instructions, you must not attempt to drill a delay down to a shorter delay time than the shortest delay time they certified. The simple reason is that if the delay gets too short, there is not enough delay material left to retain the high pressure as the propellant is burning. This can result in a cato and the malfunctioning ocket motor can make the rocket crash and cause injury and/or fire.

Click to expand...

That is why the odd roc fliers get the "I have my eye on you" hand motion and are automatically on double secret probation with strict supervision by at least two certified members. If they would just fly decent 3FNC and maybe cut a 10 to a 7 then we could all truly relax.

shreadvector said:

To maintain your insurance and follow the manufacturer's instructions, you must not attempt to drill a delay down to a shorter delay time than the shortest delay time they certified. The simple reason is that if the delay gets too short, there is not enough delay material left to retain the high pressure as the propellant is burning. This can result in a cato and the malfunctioning ocket motor can make the rocket crash and cause injury and/or fire.

Click to expand...

Fred said "CATO"!

Nope. I said "cato", not "CATO" because I am not an idiot and I do not try to bully others into being an idiot.

qquake2k said:

Fred said "CATO"!

Click to expand...

shreadvector said:

Nope. I said "cato", not "CATO" because I am not an idiot and I do not try to bully others into being an idiot.

Click to expand...

Wow.