AeroTech Delay Drilling

[tjkopena]

Just about to order materials for an L1 certification, specifically a 29/180 case+closures and an AeroTech H128W-14A reload. I had thought AeroTech's RDDT would be used to adjust that delay, but Sirius' webstore links that reload to the UDDT specifically & clearly:

Motor comes with 14-Second delay that can be adjusted. To adjust time delay, drill delay 0.025" per second of adjustment using twist drill or optional AeroTech Universal Delay Drilling Tool (UDDT).

That's a mistake, right? I realize the tool's just a spacer for a drill bit and you could probably adjust/calibrate either to work (or just use a drill bit), but my understanding is:

• The UDDT has a shorter body in order for the bit to reach the delay grain down inside the pre-assembled DMS motors.
• The RDDT has a longer body because the delay grain in the RMS/RMS+ reloads is inserted into the tool directly so only minimal length of the bit is needed.

Correct? Long story short, I want the RDDT for the RMS+ H128W, yes? That text & link on Sirius' store gave me pause so I wanted to double check before ordering.

Thanks

 

[TheTank]

Just about to order materials for an L1 certification, specifically a 29/180 case+closures and an AeroTech H128W-14A reload. I had thought AeroTech's RDDT would be used to adjust that delay, but Sirius' webstore links that reload to the UDDT specifically & clearly:


That's a mistake, right? I realize the tool's just a spacer for a drill bit and you could probably adjust/calibrate either to work (or just use a drill bit), but my understanding is:

• The UDDT has a shorter body in order for the bit to reach the delay grain down inside the pre-assembled DMS motors.
• The RDDT has a longer body because the delay grain in the RMS/RMS+ reloads is inserted into the tool directly so only minimal length of the bit is needed.

Correct? Long story short, I want the RDDT for the RMS+ H128W, yes? That text & link on Sirius' store gave me pause so I wanted to double check before ordering.

Thanks

Correct. You want the RDDT for RMS. The UDDT is for DMS.

 

[TheTank]

And side note, H128W in the 29/180 is a good motor. Used it on my L1. H165R is also great.

 

[UhClem]

Correct? Long story short, I want the RDDT for the RMS+ H128W, yes? That text & link on Sirius' store gave me pause so I wanted to double check before ordering.

It depends. Aerotech has been shifting from the old assembled by user delays to a new preassembled delay/closure (RMS-EZ) that is very much like the DMS motors. And uses the DMS tool.

If it really is RMS+ then it uses the old tool. If it is RMS-EZ then you need the new one. (You need the old one to calibrate the new one so you might as well get both.)

 

[tjkopena]

Thanks @TheTank. Order's placed, looking forward to it.

It depends. Aerotech has been shifting from the old assembled by user delays to a new preassembled delay/closure (RMS-EZ) that is very much like the DMS motors. And uses the DMS tool.

Is RMS-EZ actually a thing anymore, or at least currently? I'm sure people still have them around, but I haven't seen any for sale. My read of the history is the original RMS-EZ debuted ~2013 but was halted by ~2015 or so because of delay adhesion issues leading to burn-through and early ejection. In 2020 AeroTech said that issue had been resolved but the only EZ load available was the J520W and that in general going forward the EZ concept had been subsumed by the DMS motors. Doesn't really matter to these questions as the DMS uses the same UDDT drilling tool, or to me at all personally for the moment, but I'm curious.

Thx

 

[jimzcatz]

You don't need a delay tool for the H128,or ANY reload. It just makes it easier. Take a 1/4" drill bit and drill 1/32nd of an inch into either end of the delay grain for every second you want to remove from the factory delay to reach your desired delay time. The end facing the propellant is preferred but I have done both sides.

 

[rcktnut]

You don't need a delay tool for the H128,or ANY reload. It just makes it easier. Take a 1/4" drill bit and drill 1/8th of an inch into either end of the delay grain for every second you want to remove from the factory delay to reach your desired delay time. The end facing the propellant is preferred but I have done both sides.

Drilling 1/8th in. would be 4 seconds off the delay!!!

 

[jimzcatz]

Brain fart, Its indeed 1/32nd inch per second. I edited my post

 

[tfish]

post not needed....

Tony

 

[rocket_troy]

You don't need a delay tool for the H128,or ANY reload. It just makes it easier. Take a 1/4" drill bit and drill 1/8th of an inch into either end of the delay grain for every second you want to remove from the factory delay to reach your desired delay time. The end facing the propellant is preferred but I have done both sides.

That's a pretty substantial statement. I'm not saying it's wrong, but it's a big call. You're pretty much suggesting there that the pressure exponent in *all* delay grains is low enough for the flyer to treat the burn regression rate of the delay during motor operation to be close enough to that post operation (propellant burn) to treat it as a constant rate regression - FAIAP.
It wouldn't surprise me that that's the case, but it's a risky call as a universal one.

TP

 

[jimzcatz]

That's a pretty substantial statement. I'm not saying it's wrong, but it's a big call. You're pretty much suggesting there that the pressure exponent in *all* delay grains is low enough for the flyer to treat the burn regression rate of the delay during motor operation to be close enough to that post operation (propellant burn) to treat it as a constant rate regression - FAIAP.
It wouldn't surprise me that that's the case, but it's a risky call as a universal one.

TP

I have no idea what you are trying to say, but 1/32nd is a constant in Aerotech and CTI motors, but Never drill below 4 seconds of delay, with 6 being a better safety margin. Starting from the factory set delay this allows motor burn time to be factored into the delay timing.

 

[rocket_troy]

Probably a misunderstanding my end. Apologies.

TP

 

[Zeta]

Just about to order materials for an L1 certification, specifically a 29/180 case+closures and an AeroTech H128W-14A reload. ......

cool what rocket will you use ?

 

[hball55]

The universal delay tool used to be given out free. I had two and gave one to a guy needing one last Saturday. You should ask around . . . somebody’s liable to offer you one free of charge.

 

[tjkopena]

cool what rocket will you use ?

Scratchbuilt, currently a work in progress.

 

[hball55]

Thanks @TheTank. Order's placed, looking forward to it.




Is RMS-EZ actually a thing anymore, or at least currently? I'm sure people still have them around, but I haven't seen any for sale. My read of the history is the original RMS-EZ debuted ~2013 but was halted by ~2015 or so because of delay adhesion issues leading to burn-through and early ejection. In 2020 AeroTech said that issue had been resolved but the only EZ load available was the J520W and that in general going forward the EZ concept had been subsumed by the DMS motors. Doesn't really matter to these questions as the DMS uses the same UDDT drilling tool, or to me at all personally for the moment, but I'm curious.

Thx

Now I know why it was recommended to me to request a standard delay for the rms-ez I357 I had in a ziploc bag. It was loaded for launch but never launched, so I disassembled the motor and stored it in a ziploc. I have lots of old motors in my inventory, and even launched another I357 rms-ez last saturday without incident. Going to go through my inventory and look for other rms-ez motors. Thanks!