AT Reload Delays

[RCBrust]

Sorry for the dumb question guys, but slowly getting back into HPR after being out for a while. Most of my 29mm and 38mm rockets still use motor ejection. I want to order some AT reloads and it looks like everyone now only sells them with medium delays? So, it looks like I just buy mediums and then pick up the other delays separately?

Thanks,
Randy

 

[H_Rocket]

In my experience most medium delays are on the order of 8-10 seconds. I've never needed anything longer. You might and would have to locate either -L reloads or get the appropriate RDK/HDK. If you need shorter, I suggest you look into drilling them down.

Which raises an interesting question:


Gary R. -> why not simply sell all the reloads as long as possible and employ the drilling process as part of the assembly in the same manner AMW/Loki/CTI does? It's a little less convenient, however, IMHO, a bit more flexible.

 

[atticus]

To shorten the delay, you can drill. The AeroTech delay modifications are here:
http://www.aerotech-rocketry.com/cu...tions/RDK_Instructions/rms_delay_mod_inst.pdf

If you assemble at the field and on-site vendors have them you can buy the needed RDK+ delay from them as needed.
If you are going to be flying a lot and/or assembling in advance, it may be worth investing in an assortment of delay kits (they come in three packs).
Remember, you don't need to buy the mediums for the motors you will be flying as you will be swapping them out. Just keep them in a marked zip-lock to use as needed.

Here is the link to the AeroTech cross reference:
http://www.aerotech-rocketry.com/cu...Flyers_Data_Sheets/aeroTech_delay_lengths.pdf

Here is a handy table from ROC with interpolations for delays between the S,M and Ls:
http://www.rocstock.org/wizards/rms-delays_2938.pdf

Note that neither of these two include the newest motors.
If the AT links don't work, they can be found on the AT site under 'resources'.

Tim

 

[RCBrust]

Thanks guys. Buying extra delays to keep on hand is no problem. Just wanted to make sure I wasn't missing something.

Randy

 

[ttabbal]

It would be nice if AT had a nice little delay adjustment tool like CTI uses. That's one feature I really like about CTI motors, that and the 5 second build process.

 

[cls]

I assembled a collection of every RDK and put them in an organizer box. With a cross-reference chart, you can pick pretty much any delay you want for any motor.

I used to get burn-throughs with drilled delays - dunno why but haven't had any since I started just substituting them.

Here's a couple cross-reference charts to get you started:

from the ROC "wizards" page:
http://www.rocstock.org/wizards/rms-delays_2938.pdf
http://www.rocstock.org/wizards/rmsdelays_54.pdf
http://www.rocstock.org/wizards/graphs.pdf

Tony Cooper's list
http://uscoopers.org/rockets/AerotechRMS.htm

 

[SteelyEyed]

Forget AT. I don't know why everyone doesn't fly Cesaroni. They have a great (and recently expanded) set of reloads to choose from. Get the Delay Adjustment Tool and set the delay the way you want/need it. They are much, much easier/faster to assemble. Similarly, the clean up is fast and easy. I've never had a CTI fail to light on the first try. After flying CTI motors once you will never want to use AT again...

 

[fox_racing_guy]

Recently I've been hearing about Cesaroni M loads (CTI M1400)going BOOM at ignition, I think I'm sticking with AeroTech in the near future. If you need dead nuts accurate delays AeroTech does make a electronic forward closure (timer based) that works well and I'm surprised more people don't use it. http://www.aerotech-rocketry.com/index.php?main_page=index&cPath=18

 

[sumo310b]

Does anyone know which RDK grains suit Mojave Green motors? I can't find any information on them

 

[n5wd]

Recently I've been hearing about Cesaroni M loads (CTI M1400)going BOOM at ignition

What you're probably hearing is mumblings from folks used to AT motors huffing, puffing, and chuffing before they light off! When the button gets pushed and the CTI load fires off instantly, it scares 'em 'cuz they weren't expecting it! :roll::neener::y:

Wayne

 

[cjl]

What you're probably hearing is mumblings from folks used to AT motors huffing, puffing, and chuffing before they light off! When the button gets pushed and the CTI load fires off instantly, it scares 'em 'cuz they weren't expecting it! :roll::neener::y:

Wayne

Funny - I've had the experience that in the larger motors at least, CTI lights slower than AT. Of course, in the small motors, CTI lights faster than almost any AT load with the possible exception of W9.

 

[fox_racing_guy]

Start reading at post 25 here http://www.rocketryforum.com/showthread.php?t=2331&highlight=cherry+bomb

 

[bobkrech]

Recently I've been hearing about Cesaroni M loads (CTI M1400)going BOOM at ignition, I think I'm sticking with AeroTech in the near future. If you need dead nuts accurate delays AeroTech does make a electronic forward closure (timer based) that works well and I'm surprised more people don't use it. http://www.aerotech-rocketry.com/index.php?main_page=index&cPath=18

What you're probably hearing is mumblings from folks used to AT motors huffing, puffing, and chuffing before they light off! When the button gets pushed and the CTI load fires off instantly, it scares 'em 'cuz they weren't expecting it! :roll::neener::y:

Wayne

Gentlemen

Please read the sticky on the top of this forum. http://www.rocketryforum.com/showthread.php?t=2567

"CTI Pro75 Classic propellant used in the K510, L800, L1115, and M1400 motors reloads manufactured prior to November 2008 may have a reliability issue due to propellant grain cracking. This condition can cause motor over-pressurization resulting in motor failure."

This notice was jointly posted by NAR S&T, TRA TMT and CAR MTC.

Bob Krech, TRF Propulsion Moderator
Member, NAR S&T

 

[Garoq]

In my experience most medium delays are on the order of 8-10 seconds. I've never needed anything longer. You might and would have to locate either -L reloads or get the appropriate RDK/HDK. If you need shorter, I suggest you look into drilling them down.

Which raises an interesting question:


Gary R. -> why not simply sell all the reloads as long as possible and employ the drilling process as part of the assembly in the same manner AMW/Loki/CTI does? It's a little less convenient, however, IMHO, a bit more flexible.

We have found that at least half of the reloads are flown in the medium delay configuration without modification. If we sold the reloads with the long delay standard, all medium and shorter delay users would need to drill or switch delays...which would amount to about ~75% of users instead of the current ~50%. However, if there was enough demand we would consider a change.

 

[Garoq]

It would be nice if AT had a nice little delay adjustment tool like CTI uses. That's one feature I really like about CTI motors, that and the 5 second build process.

AeroTech sells an adapter that fits the CTI 38mm adjustment tool and allows precise drilling of the 29 & 38mm RMS delays...P/N T062705-1.

Remember that for about 1/2 of flights, no delay drilling or modification is required.

 

[Garoq]

Funny - I've had the experience that in the larger motors at least, CTI lights slower than AT. Of course, in the small motors, CTI lights faster than almost any AT load with the possible exception of W9.

Some customers have told me that they enjoy the anticipation of the smoke curling out of the nozzle and the sound of the motor coming up to pressure. Others use Pyrodex pellets or thermite for "instant on" ignition.

 

[ttabbal]

AeroTech sells an adapter that fits the CTI 38mm adjustment tool and allows precise drilling of the 29 & 38mm RMS delays...P/N T062705-1.

Remember that for about 1/2 of flights, no delay drilling or modification is required.

Well, you officially rock Gary. I'll have to get me one of those. Using the same tool on AT delays is worth looking into.

Yeah, Medium works most of the time for my needs, but once in a while I have an "in between" rocket that really just deploys too fast without adjustment. I also like getting Long delays as backups for the apogee charge when I'm using electronics. If the motor doesn't come with a Long, I just buy an RDK from my vendor. He usually has the one I need.

BTW: I love the ValueRockets SU motors. I'll be ordering more of them soon. The E30 is damn fun for rockets designed to fly on D12s.

 

[Garoq]

Well, you officially rock Gary. I'll have to get me one of those. Using the same tool on AT delays is worth looking into.

Yeah, Medium works most of the time for my needs, but once in a while I have an "in between" rocket that really just deploys too fast without adjustment. I also like getting Long delays as backups for the apogee charge when I'm using electronics. If the motor doesn't come with a Long, I just buy an RDK from my vendor. He usually has the one I need.

BTW: I love the ValueRockets SU motors. I'll be ordering more of them soon. The E30 is damn fun for rockets designed to fly on D12s.

Thanks! I think we will produce an instruction sheet with photos that clearly shows how to use the adapter...it's reasonably intuitive already, but more explanation is usually better than less...

 

[Donaldsrockets]

Some customers have told me that they enjoy the anticipation of the smoke curling out of the nozzle and the sound of the motor coming up to pressure. Others use Pyrodex pellets or thermite for "instant on" ignition.

I know I for one love this effect.

In some cases you can hear the pressure building up inside the motor case. It tends to make a swish like sound.

 

[Garoq]

I know I for one love this effect.

In some cases you can hear the pressure building up inside the motor case. It tends to make a swish like sound.

In the '70s we used to coat the propellant core with catalyzed HTPB and fill it with Anthracene crystals, then shake the loose Anthracene out and let it cure. You wouldn't believe the effect, especially with the larger (3") motors!

 

[RCBrust]

Hey guys, I don't see any other delays listed for the new H250G green 29mm reload. Can this only be flown with a medium delay?

Thanks,
Randy

 

[terryg]

Hey guys, I don't see any other delays listed for the new H250G green 29mm reload. Can this only be flown with a medium delay?

Thanks,
Randy

I emailed aerotech and received this info:

"We have not worked up any further delay combinations for these motors yet.
For your information I have provided the following

For both the I245G and the J500G their Med. (10) sec. Delay works out to be an RDK 11 .500 delay and a .344 spacer (red). Using the rule of adding a 32nd of a inch per second, a long would require a delay length of 0.625 and a spacer 0.219 (yel) this works out to be a RDK 13...conversely this rule works in reverse to shorten a delay time...all this tempered by the industry 20% wag factor allowed by the NFPA.

The H250G uses a delay 0.406 in length and a 0.312 (pink) spacer (Med. (10) sec) A long for this motor using the above rule would require a delay length of 0.531. We currently do not cut a HP delay in this size, adding another 32nd you would come up with an RDK 05 with a delay length of 0.563 with a spacer length of 0.156 (aqua) this delay would provide a delay time of 15 to 16 seconds +- the 20% rule."
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