Aerotech RMS Delay Drilling

[qquake2k]

But is the delay grain length on the AT site now correct? I have a lot of various "10 second" delays to drill and want to make sure I am starting with an actual 10.

I've only had two delay problems. On one, the ejection charge went off while the motor was still under thrust. Never did figure out what caused it. On the other, the delay grain burned through the side and set off the ejection charge early. Didn't figure that one out either.

 

[qquake2k]

I thought you just ordered delay kits. Am I wrong?

I don't. I buy reloads with the longest delay possible, then drill them to the delay length I need.

 

[KenRico]

I don't. I buy reloads with the longest delay possible, then drill them to the delay length I need.

Have been doing the same so far, looking forward to things standardizing like the new motors with the max delay shipping stock like G138T and the MetalStorm - instead of Medium dealy. I have shown up to a launch thinking to buy am HDK or RDK and the vendor is out of the one I need . Still use rocksim to look at the delays to see if the M is a 8 or 10 second delay, so the new style helps there too.

Have drilled H's , G's , F35 and a D24T so far - the more I do the easier it gets (like which way to face the drilled delay) and no big surprises yet . Sure is a lot easier with the AT tool !

When the TARC teams were in full swing a few monthes ago all the vendors were out of SU Fs with 6 second delay, if they would have used reloads they could have drilled .

Drill and baby, drill !

Kenny

 

[qquake2k]

Have been doing the same so far, looking forward to things standardizing like the new motors with the max delay shipping stock like G138T and the MetalStorm - instead of Medium dealy. I have shown up to a launch thinking to buy am HDK or RDK and the vendor is out of the one I need . Still use rocksim to look at the delays to see if the M is a 8 or 10 second delay, so the new style helps there too.

Have drilled H's , G's , F35 and a D24T so far - the more I do the easier it gets (like which way to face the drilled delay) and no big surprises yet . Sure is a lot easier with the AT tool !

When the TARC teams were in full swing a few monthes ago all the vendors were out of SU Fs with 6 second delay, if they would have used reloads they could have drilled .

Drill and baby, drill !

Kenny

I've drilled everything from D's to I's, 24mm, 29mm, and 38mm. I really like the versatility of being able to drill the delays. That way I can adapt the reload to whichever rocket I want to fly. The only thing I don't like about the AT drill, is that you can only drill in 2 second intervals. In actuality, it probably doesn't matter, but I did make a washer out of some .031" thick aluminum, so I can drill in 1 second intervals.

 

[jd2cylman]

I have the CTI DAT tool (is saying tool redundant after the T? I guess I should ask the redundant department of redundancy department) with the AT adapter. I've only used it on AT reloads, as I've only gotten the Pro 38 cases recently and haven't had a chance to fly any yet. Almost every time I used it, I had early deployments. I had a conversation with a fellow TRF'er tonight and found out something interesting. The Pro 38 set I bought came with a DAT. Interestingly, the DAT had on the side a label that roughly read "prototype, for testing purposes only". So naturally, I had to get out my tool and compare them. Oddly, the prototype was shorter than the production one I originally had. The prototype was 29/32" total exposed drill length, while my production one was 1 1/32" long. An 1/8" longer, yes? So a PM is sent to Jeroen to see which one is correct, but as I said earlier, I was talking to a fellow TRF'er, who also had 2 Pro 38 DAT's in his possession. BOTH of his tools measured under 1". He measured 15/16". His ruler may not have been as accurate as mine tho..... They could have been 29/32", but even still, they were under 1". So........... anyone else want to measure their tool (why did I just giggle?)

Adrian
(who sometimes still thinks like a teenager, until I try to stand)

 

[Winston]

You can go by the color of the spacer, and the info listed in the Hobby delay kit (HDK) .pdf on the resource area of the Aerotech website, to determine which delay you have.

That PDF is here:

https://www.aerotech-rocketry.com/c...ary/Catalogs_Flyers_Data_Sheets/hdk_x-ref.pdf

 

[Winston]

I have the CTI DAT tool (is saying tool redundant after the T? I guess I should ask the redundant department of redundancy department) with the AT adapter. I've only used it on AT reloads, as I've only gotten the Pro 38 cases recently and haven't had a chance to fly any yet. Almost every time I used it, I had early deployments. I had a conversation with a fellow TRF'er tonight and found out something interesting. The Pro 38 set I bought came with a DAT. Interestingly, the DAT had on the side a label that roughly read "prototype, for testing purposes only". So naturally, I had to get out my tool and compare them. Oddly, the prototype was shorter than the production one I originally had. The prototype was 29/32" total exposed drill length, while my production one was 1 1/32" long. An 1/8" longer, yes? So a PM is sent to Jeroen to see which one is correct, but as I said earlier, I was talking to a fellow TRF'er, who also had 2 Pro 38 DAT's in his possession. BOTH of his tools measured under 1". He measured 15/16". His ruler may not have been as accurate as mine tho..... They could have been 29/32", but even still, they were under 1". So........... anyone else want to measure their tool (why did I just giggle?)

Adrian
(who sometimes still thinks like a teenager, until I try to stand)

Mine is not a prototype and the exposed drill length (with the drill and its holder removed from the tool body) is exactly 0.914 as measured with a digital caliper. 15/16ths is 0.9375, 29/32 is 0.906, 1 1/32 = 1.031. So, my production tool is the same as your prototype. Haven't actually used the drill yet.

Perhaps the various lengths are due to different tool internal spacer lengths? After all, it's the depth of the hole drilled that counts.

 

[accooper]

I've drilled everything from D's to I's, 24mm, 29mm, and 38mm. I really like the versatility of being able to drill the delays. That way I can adapt the reload to whichever rocket I want to fly. The only thing I don't like about the AT drill, is that you can only drill in 2 second intervals. In actuality, it probably doesn't matter, but I did make a washer out of some .031" thick aluminum, so I can drill in 1 second intervals.

I use a 3/16ths inch drill with a stop on it and use calipers to measure seconds. Never had a problem.

Andrew:y:

 

[jd2cylman]

Mine is not a prototype and the exposed drill length (with the drill and its holder removed from the tool body) is exactly 0.914 as measured with a digital caliper. 15/16ths is 0.9375, 29/32 is 0.906, 1 1/32 = 1.031. So, my production tool is the same as your prototype. Haven't actually used the drill yet.

Perhaps the various lengths are due to different tool internal spacer lengths? After all, it's the depth of the hole drilled that counts.

The spacers were identical. Thanks to Jeroen at CTI for a quick response to my PM. My production tool was made incorrectly. He just told me to have Tim to swap it out.

Adrian

 

[Winston]

The spacers were identical. Thanks to Jeroen at CTI for a quick response to my PM. My production tool was made incorrectly. He just told me to have Tim to swap it out.

Adrian

OK, so to make it clear for anyone who wants to check their CTI Delay Adjustment Tool, the proper overall length of the drill bit is 29/32".

 

[jd2cylman]

Straight from Jeroen, the exposed length of the drill bit is exactly 0.925", anything longer is zipper bound.
Good luck. May you all have the correct length and mine was the fluke.

Adrian

 

[gary7]

Quake, how many times have you used your 1 second delay drilling washer? Has it worked ok for you? How do you determine your delay length need?

 

[qquake2k]

Quake, how many times have you used your 1 second delay drilling washer? Has it worked ok for you? How do you determine your delay length need?

I haven't had a chance to use it yet. I use Thrustcurve.org to determine delay times. It's worked very well for me. I print out the page from Thrustcurve for each rocket, and put them in a binder.

 

[Winston]

Straight from Jeroen, the exposed length of the drill bit is exactly 0.925", anything longer is zipper bound.
Good luck. May you all have the correct length and mine was the fluke.

Adrian

Ideally, the exposed length is supposed to be exactly 0.925". Mine measured exactly 0.914" which is close enough since slightly over 1/100ths of an inch difference isn't going to make much of a difference in the delay time. Anything significantly shorter is zipper bound on the way down, anything significantly longer is zipper bound on the way up.

 

[jd2cylman]

Ideally, the exposed length is supposed to be exactly 0.925". Mine measured exactly 0.914" which is close enough since slightly over 1/100ths of an inch difference isn't going to make much of a difference in the delay time. Anything significantly shorter is zipper bound on the way down, anything significantly longer is zipper bound on the way up.

Yup. What he said!

Adrian ( I knew it wasn't operator error on all those short delays recently!)

 

[DeltaVee]

Yes, the drilled end faces the propellant grain.

Wait a sec.... I've had LOTS of people telling me exactly the opposite. in principle, it shouldn't make a difference I would think but I'm not entirely sure of anything these days.

Come to think of it, with the AT DMS motors, it's not possible to NOT drill the ejection charge side of the delay.

 

[o1d_dude]

That’s an EIGHT year old thread resurrection!

To answer your question, I don’t think it really matters which way the divot faces but I always try to keep it facing the propellant grains. My thinking (right or wrong) is that I don’t want the BP flowing down into the case. If I mistakenly insert the delay grain the other way, I’m not going to remove it and try again. It’s an “oh, well” thing and I move on.

Advisory: My statement pertains to 38mm motors and smaller.

 

[mbeels]

Wait a sec.... I've had LOTS of people telling me exactly the opposite. in principle, it shouldn't make a difference I would think but I'm not entirely sure of anything these days.

Bob Kresh has a good post on this topic somewhere. One reason to have the drilled end towards the propellant grains is that the entire delay grain is more completely burned up by the time the ejection charge goes off. Delay grains are basically very slow burning propellants, so if you put the drilled end towards the ejection charge, it burns through there first, sets off the charge, and a ring of delay grain continues to burn, slow cooking the inside of your rocket.

 

[mbeels]

Found it:

https://www.rocketryforum.com/threads/delay-drilling-drill-bit-size.11489/post-108787

 

[DeltaVee]

Bob Kresh has a good post on this topic somewhere. One reason to have the drilled end towards the propellant grains is that the entire delay grain is more completely burned up by the time the ejection charge goes off. Delay grains are basically very slow burning propellants, so if you put the drilled end towards the ejection charge, it burns through there first, sets off the charge, and a ring of delay grain continues to burn, slow cooking the inside of your rocket.

Hmmmm sounds like a good point there!

 

[mbeels]

Hmmmm sounds like a good point there!

Bob Krech had a lot of very smart and useful things to say. When ever I come across one of his posts, I usually find it is worthwhile to read it. Unfortunately I don't believe he posts here anymore.

 

[beeblebrox]

Bob Kresh has a good post on this topic somewhere. One reason to have the drilled end towards the propellant grains is that the entire delay grain is more completely burned up by the time the ejection charge goes off. Delay grains are basically very slow burning propellants, so if you put the drilled end towards the ejection charge, it burns through there first, sets off the charge, and a ring of delay grain continues to burn, slow cooking the inside of your rocket.

Yes, Exactly. It is called the Hibachi effect... BUT if you are only drilling out a couple seconds, it is not that big a deal. The delay pellets for AT motors are cut to the length for the stock delay time. With a reload, the other reason to drill the side facing the propellant is that you have a solid cut face on the ejection side where the seal takes place. Drilling the ejection side weakens that and can cause a blow thru. I HAVE seen that happen. BTW I used to work for AeroTech, so I know what I am talking about...

 

[mbeels]

Drilling the ejection side weakens that and can cause a blow thru. I HAVE seen that happen. BTW I used to work for AeroTech, so I know what I am talking about...

That's arguably a much more important reason!

 

[tOD]

That's arguably a much more important reason!

I just measured the drill bit diameter of my various delay adjusting tools.
AT Universal Delay Tool
AT RMS Delay Tool
CTI Pro54
CTI Pro38
All of them measured 0.250"