Ejection Charge can they be eliminated.

[Thruster]

I'm making the BSG Viper with a BT-50 and there is no need for the 3 engines that are mounted to the main tube to have an ejection charge. Can the ejection charge in the B &C size engines be eliminated?

[Vanel]

The Viper had only a single motor in the main tube - the 3 "engines" are just empty tubes.

Unless, of course, you plan to turn it into a 4 engine cluster. If so, add PLENTY of nose weight. heck, it needs a fair amount with a single motor.

[Thruster]

The 4 engine cluster version is called the Hyper Viper, I don't know if I'm ever going to launch it with 4 engines but, well ok yes I am. :D
As far as the weight and balance issue, I can make an extension for the BT-50 main tube with more weight and extend that weight a few more inches from the CP. This would be for when I launch it as the Hyper Version, giving the weight a little more effect on the CG.

[barone]

I'm making the BSG Viper with a BT-50 and there is no need for the 3 engines that are mounted to the main tube to have an ejection charge. Can the ejection charge in the B &C size engines be eliminated?
The model rocket safety code doesn't permit modifying motors. Now with that said, don't try to remove the charge. If you want to eliminate the effects of it, you can plug the end with a PVC screw plug (or jam a wood dowel into it). When the ejection charge goes off, it will actually vent through the nozzle and give you a little added boost. ;)

[Thruster]

The model rocket safety code doesn't permit modifying motors. Now with that said, don't try to remove the charge. If you want to eliminate the effects of it, you can plug the end with a PVC screw plug (or jam a wood dowel into it). When the ejection charge goes off, it will actually vent through the nozzle and give you a little added boost. ;)
Thanks Don, I'm going to test that out tomorrow.
What effect will putting engines in the 3 engine bays have on this birds flight characteristics?

[barone]

Thanks Don, I'm going to test that out tomorrow.
What effect will putting engines in the 3 engine bays have on this birds flight characteristics?
Well, if you build it like the Hyper, looks like you need to add slightly more than 3.5 oz to it. If your clusters all ignite, it should be a really good looking flight. If one of the outboards fail to light........ :rolleyes:

By the way, I'd go with the screw plugs over the dowels. Positive retention without glue and re-usable....take a motor with you to make sure you get the right size.

[Thruster]

Check this site out Barone.
http://vernarockets.com/id26.html

[Doug Sams]

I'm making the BSG Viper with a BT-50 and there is no need for the 3 engines that are mounted to the main tube to have an ejection charge. Can the ejection charge in the B &C size engines be eliminated?Thruster,
If you decide you want plugged motors, I recommend using the B6-0 or C6-0. There's no ejection charge to remove or worry about. A short length of 1/2" dowel can be epoxied into the forward end quite easily. I use these often in my clusters.

Also, if you fly this cluster, use a burn string on the main motor.
http://home.flash.net/~samily/burn-string/

Doug

[Doug Sams]

If you want to eliminate the effects of it, you can plug the end with a PVC screw plug (or jam a wood dowel into it).I've never heard of either of these techniques. Do you have much experience with them?


When the ejection charge goes off, it will actually vent through the nozzle and give you a little added boost. ;)If it doesn't expel the nozzle...or the plug :)

Doug

[Thruster]

Thanks Doug, Thats a great idea. What happens if one of the clustered engines does not fire?

[Doug Sams]

Thanks Doug, Thats a great idea. What happens if one of the clustered engines does not fire?Normally it's not a big deal. Usually, on a typical rocket, the outboards aren't far enough off the centerline to impart significant torque steer.

In your case, I'd fly it on a single motor the first flight, then try the cluster :)

Doug

[pantherjon]

Looks interesting Thruster! 2 ideas for your pod motors:

Use -0 motors(B6-0/C6-0) as they don't have an 'ejection' charge..They have no delay(hence the -0) so you may have some burning embers/gas come out the front of the motor on burnout...

Adapt it for 13mm and use A10-PT motors, these are PLUGGED motors that do not have e-charges...

[tbzep]

Looks interesting Thruster! 2 ideas for your pod motors:

Use -0 motors(B6-0/C6-0) as they don't have an 'ejection' charge..They have no delay(hence the -0) so you may have some burning embers/gas come out the front of the motor on burnout...

Adapt it for 13mm and use A10-PT motors, these are PLUGGED motors that do not have e-charges...

The zero delay motor will have a fairly high pressure blow through even without an official delay and ejection charge. It is strong enough to eject a recovery system. I never really noticed it when I used them as boosters, but the first time I saw a flying saucer kit fly, the booster motor looked like it was shot out of the saucer with a cannon. It needs to be plugged, vented, or allowed to eject the casing in order not to damage the rocket.

[Doug Sams]

...so you may have some burning embers/gas come out the front of the motor on burnout... Jon,

Ain't no "may" to it; they will have burning crap coming out the end and it has to be accounted for, either by allowing the motors to eject themselves, or by having a vent forward of the motor. Or by plugging them.

The keys are that there can be lots of nasty crap coming out the end, and the pressure can be quite high. I've seen it high enough to rupture the ariframe/motor tube on tape-together stagers. Hence why I recommend plugging.



Adapt it for 13mm and use A10-PT motors, these are PLUGGED motors that do not have e-charges...The A10-PT is a good idea. Besides installing 13mm mounts, these can also be used in 18mm mounts with disposable adapters - ie, spent more cases.

Doug



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