adding a washer?

[gary7]

I hope I am making sense here:
The current (newer) delays in Aerotech single use DMS motors are 14. The Aerotech drilling tool allows for drilling in only 2, 4, 6 ane 8 seconds depending on which end and whether or not the washer is used. If I had another washer only half the thickness of the washer provided with the drilling tool or a washer 50% thicker, would that not allow for 1 sec extra drilling which would allow odd second drilling like 1, 3, 5 and 7 seconds?

Why???

What if my simulations tell me an 8 sec delay may be just a bit too early but a 10 second delay obviously too long. If I could drill down to 9 seconds, the delay time is better. At least addording to my simulations.

I might be willing to pay for professional machining of 1 second thicker and/or thinner washers. Maybe Aerotech could maybe provide it???

 

[jmasterj]

Many plastic credit cards are 1/32" thick. I've made washers out of them to get odd AT delay times.

 

[waltr]

Yes, I do exactly that. I used a piece of 1/32 inch (0.031") thick G10 (epoxy glass) board and drill a hole for the delay bit and then cut it into t a circle. Now I have 1 second delay intervals.

A piece of 1/32 aluminum or other material will also work.

 

[Kelly]

Being 1 second off from 'ideal' only changes peak altitude by 16', so most people forgo that level of accuracy. But, I see no reason it wouldn't work.
Keep in mind that the accuracy of the delay is only certified to within 20% (which would be 1.6s for an 8s delay) and the impulse (which would affect the delay time needed) has similar variation in accuracy, and your simulation is probably off by a bit too. So dialing in super-accurate delays may be an exercise in futility.

 

[jmasterj]

I've read that "exercise in futility" line before, and I don't buy it. I know about the variance, but the closer I am to the ideal delay, the less likely variance will hurt me. If apogee is at 9s and my 9s delay runs 20% long, that's 2 seconds after apogee. If my 10 second delay runs 2 seconds long, that's three seconds after apogee. Seems like it could be the difference between a zipper and no zipper.

It also costs almost nothing to make a washer from an expired CC and use that to drill the delay a little less.

 

[crossfire]

I found some plastic washers used in plumbing that a perfect.

 

[Rocketjunkie]

Normal variation in delay times is far more than 2 seconds. If your recovery system can't withstand 2-3 seconds from optimum, you have a problem. What happens if the flight isn't straight up and the rocket never gets below 100 ft/sec? Drilling within a couple seconds is plenty good enough.

 

[prfesser]

Normal variation in delay times is far more than 2 seconds. If your recovery system can't withstand 2-3 seconds from optimum, you have a problem. What happens if the flight isn't straight up and the rocket never gets below 100 ft/sec? Drilling within a couple seconds is plenty good enough.

This. Run OR or Rocksim on a typical model with, say, a given motor, and find the optimum delay time. Run again but with one second shorter, and yet again, one second longer. The velocity at deployment isn't a problem for any of the three runs. The rocket slows down a lot near apogee, and it takes a little while to speed up past apogee.

 

[jimzcatz]

You don't need any fancy washer or for that matter the delay tool. Just drill your hole to the depth you want taking into account 1/32nd is minus 1 second. A tire tread depth gauge will work or any other measuring tool graduated in 32nds of an inch