Aerotech Delay Grain Burnrates

Are the Std. Aerotech delay grains w/ same dia. and length the same burn rates ?
For example - HDK 05, 06, 10, 17 are the same dia and length.
But different part numbers for different motors.
HDK 06 is listed as Slow, all the rest Std.

Any Aerotech gurus out there ?

If you look at this document :- https://www.aerotech-rocketry.com/c...ary/Catalogs_Flyers_Data_Sheets/hdk_x-ref.pdf ,you will see the delay grain in the HDK5,10 and 17 all have part No03209 , but as each is used in different motor caseings they require different spacers and other parts for the delay assembly to fit hence the different HDK kit No's.

Any of the delays marked "slow" use a slower burning delay material.

rocketsaway said:

Are the Std. Aerotech delay grains w/ same dia. and length the same burn rates ?
For example - HDK 05, 06, 10, 17 are the same dia and length.
But different part numbers for different motors.
HDK 06 is listed as Slow, all the rest Std.

Any Aerotech gurus out there ?

Click to expand...

All non-slow delay grains burn 1/32" (conveniently awfully close to 32 thousandths of an inch) per second after the main propellant burnout.

The differences in length are to compensate for the varying amount consumed during the various motor burns.

My chart is different. No date.
Shows D13-7W as 41307 - HDK-05
Last 2 digits correspond to Secs (07) not Type
The chart shows all delays. 18mm-54mm

Posted one shows 43505 D13-7W- HDK-05, Date 2008.
Last 2 digits correspond to Type (05) not Secs.

I assumed all Std burned the same under Atm, until I found a diff chart w/ diff P/N.
Thats whats got me spinning.

Yea, what CarVac said. It has been common knowledge to adjust all Aerotech delays drill 1/32" for each second you want to trim. This has come straight from Gary and is also included in reload instructions. So quick answer, if you know motor burn time and delay length, theres your total. Regarding the RDK kits, sorry you are on your own. Good luck.

This question is best addressed by the manufacturer. Manufacturers can and do adjust compositions as material suppliers change. This may result in slight changes in the burn rate. Check the resources folder on the AT website for documentation. If you can't obtain the information there, contact AT by e-mail or phone.

Bob

The best answer would come from AeroTech.
However until that happens...
The 1/32 inch (.024 - .031 inch per Aerotech delay modification document) per second is for the burn rate AFTER propellant burnout.
Under presssure the delay grain will burn faster and at different rates depending on propellant type.

All but the longest delays on slow burn propellants (think Black Jack) use the 'std.' composition.

As to length, the overall delay element length is the same for any particular hardware, but the delay and spacer lengths will vary with the HDK (or RDK) numbers.

Tim

Is HDK-Slow a slow delay composition compared to Std ?

What are the delay spacers for ? To keep the grain in or so the user doesnt mix delays to motors ?
If I recall, the delays were hard to push in the closure. Once in, you couldnt remove.
Its been about 10ys since used AT.

rocketsaway said:

Is HDK-Slow a slow delay composition compared to Std ?

What are the delay spacers for ? To keep the grain in or so the user doesnt mix delays to motors ?
If I recall, the delays were hard to push in the closure. Once in, you couldnt remove.
Its been about 10ys since used AT.

Click to expand...

In Hobbyline motors, the spacer is what squeezes the grain against the o-ring. In the RMS+ motors, the o-ring is around the outside of the grain so I suspect it is less critical but just helps keep everything in place.

rocketsaway said:

Is HDK-Slow a slow delay composition compared to Std ?

What are the delay spacers for ? To keep the grain in or so the user doesnt mix delays to motors ?
If I recall, the delays were hard to push in the closure. Once in, you couldnt remove.
Its been about 10ys since used AT.

Click to expand...

Ed, the AT delay parts were redesigned several years ago. They assemble much easier, and are easily removed if need be.

The spacer also maintains the proper space above the delay. Too much BP fall through and it could blow up. The bit that does go through is like a "touchhole" on a cannon, but the main part must be in the outer well.

Maybe, what Im not quite understanding is, RCS lists a 5/8"OD x 9/16"(.563")ID delay insulator tube.
HDK delays are .563"OD. Thats a tight fit, delay into insulator. Both are paper.
The fiber washer will push against the insulator containing the tight delay, both sealing the delay oring.
No need for a delay spacer.

Unless OEM AT insulator IDs are larger, making a loose fitting delay. (which defeats the purpose of extra insulation)
Then there would be a need for a delay spacer to help push the delay against the oring.

Drawing taken from mr 29-20 140

rocketsaway said:

Maybe, what Im not quite understanding is, RCS lists a 5/8"OD x 9/16"(.563")ID delay insulator tube.
HDK delays are .563"OD. Thats a tight fit, delay into insulator. Both are paper.
The fiber washer will push against the insulator containing the tight delay, both sealing the delay oring.
No need for a delay spacer.

Unless OEM AT insulator IDs are larger, making a loose fitting delay. (which defeats the purpose of extra insulation)
Then there would be a need for a delay spacer to help push the delay against the oring.

Drawing taken from mr 29-20 140

View attachment 159457

Click to expand...

The insulator is paper and will not seal to the o-ring. The delay grain has a plastic sheath that seals properly.