Quantcast

Probably Bad But I'll ask anyways - changing delay...

The Rocketry Forum

Help Support The Rocketry Forum:

boomer

Member
Joined
Aug 4, 2004
Messages
9
Reaction score
0
Heya,

I have some E16-7s that I wish were more like E16-5s. The reason for this is my Mustang flew on F21-7's and the ejection was pretty late, I'm figuring that my E16 will be a disaster. However, I'm flying on a smaller field so I really want to use E's, and Aerotech does recommend 7 second - maybe I just build them heavy or something.

So..... I thought I would ask. Anyone have any advise as to how to shorten the delay of an RMS motor? :D

No lectures please....

Thanks!
 

shockwaveriderz

Well-Known Member
Joined
May 25, 2002
Messages
2,466
Reaction score
1
Its my understanding that you can "drill" the delay from the top(?) perhaps 1/32" and that will take off a second seconds.....so you might try 1/16" ...
I've not used the technique myself but I know it is a rather common one for HPR motors.... Its sorta like the the tool that you can buy for the Pro38 motors....you drill into the delay X amount and the delay is shorted cause the hot gases break thru earlier igniting the ejection charge.....

heres a URL that uses groups.google.com against RMR where you can read more about the technique:

http://groups.google.com/groups?hl=...ll+delay+charge&meta=group=rec.models.rockets

Now some may say this is an end user modification and against the safety code......I would think that Aerotech may allow this end user modification as Cesaroni Tech allows it....

Cesaroni/Pro38 motors are adjusted in almost exactly this way, except that the delay element unplugs from the front of the propellant assembly, and the manufacturer-supplied tool is used to drill into the surface of the delay propellant facing the main propellant. The net result is the same... there is less thickness of delay-propellant between the main chamber and the ejection powder than the undrilled delay grain had, so the powder ignites sooner.)


If you have any doubts, don't tell and nobody will ask.......
 

BlueNinja

Well-Known Member
Joined
Jan 18, 2009
Messages
2,690
Reaction score
1
I wouldn't try it. It is, imho, motor modification. What you can do however, is ask someone at a launch if they can trade you a 4 second white lightning delay for the 7 second. Not any other delay, a 4 second BlackJack or Blue Thunder delay is NOT a 4 second white lightning delay. Always match the delay with the propellant type of the motor.
 

Justin Horne

Well-Known Member
Joined
Jun 23, 2004
Messages
425
Reaction score
0
I was gonna suggest drilling it out, just like the Proxx motors, but didn't want to.. I did not want to be responsible for a blow by, or some other bad thing happening.. I bet it would work, but the simple fact that it isn't designed to do that worries me...
 

DynaSoar

Well-Known Member
Joined
Mar 15, 2004
Messages
3,007
Reaction score
0
Originally posted by boomer
So..... I thought I would ask. Anyone have any advise as to how to shorten the delay of an RMS motor? :D

Trade with someone.
 

Missileman

Well-Known Member
Joined
Apr 21, 2011
Messages
781
Reaction score
0
Delay elements for RMS motors are available seperately and in different sizes.
Cost is around 2 bucks.
Only drawback is they come 5 to a pack so you end up with extras.
 

boomer

Member
Joined
Aug 4, 2004
Messages
9
Reaction score
0
Hey,

Thanks all for your replies. I will not be launching at a club launch, so no trading available.

Never seen these delays sold separately - got a vendor in mind?
 

Missileman

Well-Known Member
Joined
Apr 21, 2011
Messages
781
Reaction score
0
I may have spoke too soon.
I buy my delay elements from Commonwealth Displays but after just looking at their site I see the smallest delay element they stock is for an F37.
 

Larry

Well-Known Member
Joined
Jan 18, 2009
Messages
638
Reaction score
0
boomer,
Delay cutters are common in HPR. I've used one for everything from an E-18 to a J-350, and it works well. 1/32" is equal to 1 second of delay. If you don't have one then use an 1/8 drill bit (turned by hand only) and make the hole in the center of the delay at the end facing the bp charge powder. I kind of look at it from safety...If the delay is way to long and the rocket separates you have pieces coming down that may be moving lots faster than parachute speed. If you shorten the delay and get the chute out on time the whole rocket will come down under chute in one piece.
Larry
 

SpartaChris

Well-Known Member
Joined
Feb 8, 2009
Messages
2,732
Reaction score
0
Andy from Polecat Hobbies shortened the delay in one of my G-64 reloads, taking it from 10 seconds to 6 seconds by using the screwdriver method. He said his rule of thumb is using a small screwdriver, each twist was one second off the delay.

-Chris
 
Top