LOC Precision EZI-65 for level 1 cert motor choice

LOC Precision EZI-65 for level 1 cert motor choice

Post by lizardquee » Wed, 30 Aug 2006 15:54:38



Hi,
I have purchased the ezi-65 with intent to certify level 1.  Which
motor choice is best?  It can accommodate a 29mm, 38 mm or 54mm motor.
I am looking for versatile, cheap, and reliable.  I know-pick two, but
now all three.  I am looking at the RMS 38/240 case with an H-123W
reload.  Is this a good choice?  Also, what does the second number
after the forward slash mean in the case size?  For instance 240?
Is there a choice of case that will accommodate an H or and/or I motor?

I appreciate the help.
Laura

 
 
 

LOC Precision EZI-65 for level 1 cert motor choice

Post by Will Marchan » Wed, 30 Aug 2006 20:31:37


The H123W is a nice load.  The 240 is the largest total impulse that
casing carries.  You can use the same closures and get different casings
to give yourself a wider variety of loads.  Take a look at the
https://secure.consumersinterest.com/performancehobbies/store.asp?gro...
"complete motor systems" where Ken sells one set of closures but
multiple casings to give you the complete set of reload possibilities.
For about $150 you can get one set of closures and all three 38mm
casings.  That will get you your nice assortment of H and I reloads.
See Ken's page at
https://secure.consumersinterest.com/performancehobbies/store.asp?gro...
for a list of the reloads each casing takes.
        Will

Quote:

> Hi,
> I have purchased the ezi-65 with intent to certify level 1.  Which
> motor choice is best?  It can accommodate a 29mm, 38 mm or 54mm motor.
> I am looking for versatile, cheap, and reliable.  I know-pick two, but
> now all three.  I am looking at the RMS 38/240 case with an H-123W
> reload.  Is this a good choice?  Also, what does the second number
> after the forward slash mean in the case size?  For instance 240?
> Is there a choice of case that will accommodate an H or and/or I motor?

> I appreciate the help.
> Laura

--
Will Marchant, NAR 13356, Tripoli 10125 L3


 
 
 

LOC Precision EZI-65 for level 1 cert motor choice

Post by Will Marchan » Wed, 30 Aug 2006 20:49:54


Doh!  Sorry, Ken's 38mm motor system just has the lower three casings.
You'd need to buy the upper ones individually...

I forgot to add that there are currently three manufacturers of licensed
Aerotech hardware: Aerotech, DrRocket, and RouseTech.  All the pieces
are interchangeable.  You'll still find some Aerotech motor hardware
inventory floating around.  The http://www.drrocket.com/ and
http://www.rouse-tech.com/ hardware is very nice...

I also like the http://www.lokiresearch.com/ products.

...

Quote:
> For about $150 you can get one set of closures and all three 38mm
> casings.  That will get you your nice assortment of H and I reloads.

...

--
Will Marchant, NAR 13356, Tripoli 10125 L3

 
 
 

LOC Precision EZI-65 for level 1 cert motor choice

Post by Larr » Thu, 31 Aug 2006 02:08:01


H-123W is a good choice.  I certified on a PML D Region Tomahawk with
an H-242T which also fits the 38/240 casing.  It has a higher thrust
and was recommended because it was pretty windy that day and a faster
liftoff has less chance of weathercocking.  I had to chase it almost a
mile through waist high hay.  With the Aerotech casings, you can
usually find 3 or 4 reloads that fit each length casing.  The
propellent formulations are White Lightning (yellow flame and white
smoke), Blue Thunder (blue violet flame and no smoke but high thrust,
Black Jack (orange flame and black smoke), and Redline (red flame and
smoke).  I like to fly the Tomahawk on the H-123W because I like the
smoke, but the rapid acceleration on the blue thunder is nice too.

Larry

Quote:

> Hi,
> I have purchased the ezi-65 with intent to certify level 1.  Which
> motor choice is best?  It can accommodate a 29mm, 38 mm or 54mm motor.
> I am looking for versatile, cheap, and reliable.  I know-pick two, but
> now all three.  I am looking at the RMS 38/240 case with an H-123W
> reload.  Is this a good choice?  Also, what does the second number
> after the forward slash mean in the case size?  For instance 240?
> Is there a choice of case that will accommodate an H or and/or I motor?

> I appreciate the help.
> Laura

 
 
 

LOC Precision EZI-65 for level 1 cert motor choice

Post by Thomas Koszut » Thu, 31 Aug 2006 04:54:36


Laura,

    I chose the 38 casings for my investment into HP reloadable motors.  You
can fly from G's (38/120) to J's (38/720 and 38/1080).  The 29mm casings
don't really cover the L1 range well at the top end.  The 54's are all J and
up, as far as I know.

    The H123W is a very nice choice for that rocket with the 38/240, though
not on the recommended motor list.

    The post by Larry described the four different loads each one will take
nicely.  I like the Redlines and the BlackJacks myself.  In general, the
BlackJack will have the lowest thrust (slowest burn) and impulse for a given
casing.  The Redline and White Lightning are moderate thrust and impulse,
and the Blue Thunder is a very fast burn with high thrust and total impulse.

    If you multiply the weight of the rocket in ounces (loaded, ready to
launch)  by 1.4, you get the minimum average thrust in Newtons recommended
for the rocket to maintain the 5:1 thrust to weight ratio for safe liftoff.

    Rocket Weight (in ounces) x 1.4 = Minimum average thrust (in Newtons)

My Tomahawk was about 100 ounces (with the motor - you have to estimate
first then confirm when you choose a motor) so I would pick a motor with at
least 140 N of average thrust to launch it.  An H148R would be rock bottom
minimum thrust for 5:1.  A J90 would not be enough thrust to safely launch
it.

    The ezi-65 has a published weight of  35 ounces.  Using 42 ounces as a
reference with a motor (G61W is about 7 ounces), the minimum recommended
average thrust for the motor would be 42*1.4=59N.   Any 38mm motor will
launch it with enough authority for stable flight, even the G61W (check the
weight) or G67R.  Some of the big Blue Thunders will have it close to Mach
1.  The I435T will launch it at 54 g's in the simulation.  The EZI-65 is a
light HP Rocket.  Look for the lower thrust motors (my opinion).

    The number after the slash is the approximate maximum impulse that the
particular case will accomodate.  Each increase in impulse of 120 Ns is
another grain.
38/120 = 1 grain (G motor)
38/240 = 2 grain
38/360 = 3 grain
38/480 = 4 grain
38/600 = 5 grain
38/720 = 6 grain (full I and low J)
38/1080 = 9 grain (upper J)

All of the enclosures for a particular size have the same fore and aft
fittings, even between AeroTech and Dr. Rocket.  You only have to by one
full motor (tube and closures) and then just the case (tube) for every other
motor you would like.

I launched a 3" PML AMRAAM on an H148R for my L1 with a borrowed 38/240.  An
I161W in my 38/480 case was also a nice AMRAAM launch.  My first dual
deployment a couple flights later with the PML Tomahawk on an I195J, also in
my own case - 38/600.

Al's Hobby http://www.alshobbyshop.com/store/index.asp had a 25% off thing
going on this summer, maybe until September.  I picked up the 240, 360, 480,
600, and 720 casings for about $200.  All except the 600 - which is a
Dr.Rocket - are Aerotech.  The special is not listed on their website now,
but you may want to give a call.


Quote:
> Hi,
> I have purchased the ezi-65 with intent to certify level 1.  Which
> motor choice is best?  It can accommodate a 29mm, 38 mm or 54mm motor.
> I am looking for versatile, cheap, and reliable.  I know-pick two, but
> now all three.  I am looking at the RMS 38/240 case with an H-123W
> reload.  Is this a good choice?  Also, what does the second number
> after the forward slash mean in the case size?  For instance 240?
> Is there a choice of case that will accommodate an H or and/or I motor?

> I appreciate the help.
> Laura

 
 
 

LOC Precision EZI-65 for level 1 cert motor choice

Post by lizardquee » Thu, 31 Aug 2006 05:01:44


Thank you Will,
Great answer!
Knowing the meaning of the impulse number clarifies much.  I did notice
an apparent discrepancy.  On the page below, an H-238T is recommended
for a 29/180 case.  Am I missing        something?  Does it have to do with
total impulse as opposed to average thrust?

http://www.drrocket.com/sizematters.asp
Also why would I want to put a H-112J into 38/360 as recommended on the
same webpage?
I appreciate your help in this.  When visiting Illinois, I recently
fired what I believe to be an underpowered loc precision 4-29ss using
two F20-4Ws, which was a little scary and embarrassing - not to mention
costly!  (lost airframe tube, and transolve beeper)  No one was harmed;
the crowd enjoyed it, but...  I will NOT repeat it!  I needed to do the
math :-(
BTW, I took a look at your page, spaceflightsoftware.com.  I'm located
near Berkeley, and will be checking out lunar.org, which seems to be
the only rocketry club in the area.
Anyway-Thanks-Laura

Quote:
> Will Marchant, NAR 13356, Tripoli 10125 L3


 
 
 

LOC Precision EZI-65 for level 1 cert motor choice

Post by lizardquee » Thu, 31 Aug 2006 05:22:16


Thanks Larry and Thomas,
I missed your posts before my last reply.

Quote:

> The H123W is a very nice choice for that rocket with the 38/240, though
> not on the recommended motor list.

 Thomas, when you say it's not on the recommended list, whose list do
you mean?  Loc Precision's List?  NAR's list?  Please explain.
I want to make sure that I can recover the rocket and I don't have any
decent electronics for locating other than a transolve beeper.  So I
would rather fly the rocket at a lower altitude to increase my chances,
but I still need to meet the certification requirements.

Thomas you are describing exactly what I needed to know before
launching my 4-29ss on two F20s.  I did not weigh the rocket before
flight, but it had a transolve beeper, a nomax heat pad and some overly
thick fillets.  I'm sure it was too heavy.

Quote:

>H-123W is a good choice.

I saw that some other people qualified on the H-123W so it wasn't my
idea, but why reinvent the wheel.
If anyone has a better suggestion to keep the rocket lower in altitude,
but meeting the requirements please let me know.
Thanks again-Laura
 
 
 

LOC Precision EZI-65 for level 1 cert motor choice

Post by Will Marchan » Thu, 31 Aug 2006 05:26:07


Exactly, Laura!  The total impulse is used to get the limiting number
after the slash and not the average thrust.

Good find on the DrRocket sizing chart.  Interesting question about the
H112J in the larger casing.  Maybe you want the BlackJack smoky
propellant but you need a higher average thrust than the H73J?

Condolences on the loc!  8(  Nothing like seeing a rocket drunkenly
wobble off the launch rod!  There are a couple of ways to do the math
"back of the envelope."  I divide the average thrust by 25 to get an
approximate maximum liftoff weight in pounds.  Of course, running
RockSim is best and looking for an appropriate (45 fps or higher?) exit
off of the rod.

Although I work full time for UCB, I actually live in ***ia!  So I
get to fly with NOVAAR, TRA-VA, and MDRA and telecommute to boot!  I
went to a LUNAR launch many moons ago (sorry, I couldn't resist that 8)
and they were nice folks.  I need to try and schedule a business trip to
coincide with one of their launches...
        Will

Quote:

> Thank you Will,
> Great answer!
> Knowing the meaning of the impulse number clarifies much.  I did notice
> an apparent discrepancy.  On the page below, an H-238T is recommended
> for a 29/180 case.  Am I missing   something?  Does it have to do with
> total impulse as opposed to average thrust?

> http://www.FoundCollection.com/
> Also why would I want to put a H-112J into 38/360 as recommended on the
> same webpage?
> I appreciate your help in this.  When visiting Illinois, I recently
> fired what I believe to be an underpowered loc precision 4-29ss using
> two F20-4Ws, which was a little scary and embarrassing - not to mention
> costly!  (lost airframe tube, and transolve beeper)  No one was harmed;
> the crowd enjoyed it, but...  I will NOT repeat it!  I needed to do the
> math :-(
> BTW, I took a look at your page, spaceflightsoftware.com.  I'm located
> near Berkeley, and will be checking out lunar.org, which seems to be
> the only rocketry club in the area.
> Anyway-Thanks-Laura

--
Will Marchant, NAR 13356, Tripoli 10125 L3

 
 
 

LOC Precision EZI-65 for level 1 cert motor choice

Post by Thomas Koszut » Thu, 31 Aug 2006 05:46:22


The "180" in 29/180 is the total impulse.
The "238" in H238T is the average impulse, in Newtons.  The total impulse of
the motor is 178 Ns.
An H112J has 280 Ns of impulse and is a three grain motor for the 360 N
case.

A great, free performance calculator for rockets is wRASP
http://www.wrasp.com.  Use it to simulate the launch before you fly on an
unknown configuration.  Watch the "Launch Rod Velocity".  If it is below 30
MPH, you do not have enough thrust to safely fly the rocket.

The 4-29ss at 29 ounces should leave a 6 foot rod at 39 MPH.  If both motors
lit, then your rocket was either significantly heavier than the 29 ounces,
or it was sticking to the launch rod.  Even at 50 ounces, it should have
been fine at 29 mph.


Quote:
> Thank you Will,
> Great answer!
> Knowing the meaning of the impulse number clarifies much.  I did notice
> an apparent discrepancy.  On the page below, an H-238T is recommended
> for a 29/180 case.  Am I missing something?  Does it have to do with
> total impulse as opposed to average thrust?

> http://www.drrocket.com/sizematters.asp
> Also why would I want to put a H-112J into 38/360 as recommended on the
> same webpage?
> I appreciate your help in this.  When visiting Illinois, I recently
> fired what I believe to be an underpowered loc precision 4-29ss using
> two F20-4Ws, which was a little scary and embarrassing - not to mention
> costly!  (lost airframe tube, and transolve beeper)  No one was harmed;
> the crowd enjoyed it, but...  I will NOT repeat it!  I needed to do the
> math :-(
> BTW, I took a look at your page, spaceflightsoftware.com.  I'm located
> near Berkeley, and will be checking out lunar.org, which seems to be
> the only rocketry club in the area.
> Anyway-Thanks-Laura

>> Will Marchant, NAR 13356, Tripoli 10125 L3


 
 
 

LOC Precision EZI-65 for level 1 cert motor choice

Post by Darrell D. Moble » Thu, 31 Aug 2006 06:44:15


Quote:

> I have purchased the ezi-65 with intent to certify level 1.  Which
> motor choice is best?  It can accommodate a 29mm, 38 mm or 54mm motor.
> I am looking for versatile, cheap, and reliable.  I know-pick two, but
> now all three.  I am looking at the RMS 38/240 case with an H-123W
> reload.  Is this a good choice?  Also, what does the second number
> after the forward slash mean in the case size?  For instance 240?
> Is there a choice of case that will accommodate an H or and/or I motor?

I certified Level 1 on an EZI.  I used an AeroTech I-161.  Flew it again
on an I-211.  I-161 with medium delay worked perfect.  Flew it,
certified, rocket fell in road way, truck driver flattened nosecone with
front tire.  Seasoned!

--
Visit Rocketry Planet - http://www.rocketryplanet.com

 
 
 

LOC Precision EZI-65 for level 1 cert motor choice

Post by Bruce Sexto » Thu, 31 Aug 2006 09:00:45



Quote:
> The "180" in 29/180 is the total impulse.
> The "238" in H238T is the average impulse, in Newtons.  The total impulse
> of the motor is 178 Ns.
> An H112J has 280 Ns of impulse and is a three grain motor for the 360 N
> case.

> A great, free performance calculator for rockets is wRASP
> http://www.wrasp.com.  Use it to simulate the launch before you fly on an
> unknown configuration.  Watch the "Launch Rod Velocity".  If it is below
> 30 MPH, you do not have enough thrust to safely fly the rocket.

> The 4-29ss at 29 ounces should leave a 6 foot rod at 39 MPH.  If both
> motors lit, then your rocket was either significantly heavier than the 29
> ounces, or it was sticking to the launch rod.  Even at 50 ounces, it
> should have been fine at 29 mph.

I'll also recommend "pRASP" and "RocketCalc" utilities for your Palm OS
handheld devices: http://members.shaw.ca/whortens/index.html. I never leave
home without them...