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Old 12-20-2013, 09:43 PM
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astronot astronot is offline
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Join Date: Sep 2013
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Default Question about delay times for RMS reloads

I'm seeking a little bit of clarity on RMS reloads if I may impose on you fine folks for a minute.

This how I understand things and please correct me if I'm wrong.

Let me post the specs of a motor if I may and take it from there.

Reload Designation: F12-5J
Hardware Designation: RMS-24/40
Outer Diameter: .938" (24mm)
Length: 2.75" (70mm)
Loaded Motor Weight: 67 g
Propellant Weight: 30.0 g
Propellant Type: Black Jackô (J)
Total Impulse: 43 N-sec (max)
Burn Time: 3.6 seconds
Delay Time: 5 seconds
Maximum Recommended Liftoff Weight: 15 oz/425 g

Fits: Rockets designed for black powder `D` motors

For it to be a 24mm reload this motor is pretty powerful. 43Ns not too shabby.
Now the way I understand it is, the delay and the propellant are ignited at moment of ignition and liftoff. Correct?
If that is so, with a 3.6 sec. burn time and a 5 sec. delay, then recovery deployment should happen approx 1.4 sec. after motor burn out. Is that the correct way to look at this?

If it is, then why do some websites, like Hobbylinc don't list burn time for their reloads? How am I suppose to choose the correct delay? Say a I want a 3 sec coast after burnout. How would I choose the correct motor for the desired effect?

I'm just asking. Obviously some websites, hobbylinc is not the only one, expects me to do my homework before I go shopping. Fair enough.

Where might I go to discover, uncover, educate myself on these new reloads for the smaller motors. I would love to know what I'm looking for before I shop, and at least learn while I shop. All the data is important but really what is most important to me when shopping is
Reload designation, Max lift off weight, propellant weight, total impulse, delay time, and burn time.

Some of the specs on the motors don't really jive with what I would expect on sites like hobbylinc for instance.

These specs are for an E28-7T

The average thrust of the motor is 6.3 pounds (28 Newtons).
Time delay of 7 seconds between propellant burnout and the firing of the ejection charge.
Uses the exclusive Copperhead single lead igniter.
Motor Diameter: 0.94" (24mm)
Assembled Weight: 1.9oz (54g)
Maximum Liftoff Weight: 10.6oz (301g)
Total Impulse: 40 Newtons

Aerotech Product Number: 52807

And then these specs are listed for an F24-4W

Impulse energy- F-class
Average thrust in Newtons- 24N (5.4 lbs)
Delay in seconds between propellant burn-out and activiation of the ejection charge- 4 seconds
Propellant type- White Lightning
For use in- RMS 24 Motors
Primary use- Single Stage
Motor diameter- .94" 24 mm
Assembled weight- 2.2 oz. 62 g
Maximium liftoff weight- 9.5 oz. 269 g
Aerotech Product Number: 62404

That is very confusing to me. An F class motor has less thrust than an E class motor?

Am I looking at this totally wrong or something?
Thanks in advance for the help.

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