OK, I'm curious. How do you remove a couple grams of propellant from each of
5 slugs in an I motor and end up with a J motor?
Bob Kaplow NAR # 18L TRA # "Impeach the TRA BoD"
>>> To reply, remove the TRABoD!
That's not what happened. The original 5-grain
motor was a lite J, the 670J300-15A. The first
pass at a 62.5g/grain version was an I, the
610I360-15A. Due to demand, they went back and
tweaked it to get a J again, a very lite one,
tho, the 648J285-15A.
I plan to do my L2 with this one.
How did they get more impulse without adding
mass? Well, IANAME, but I do know other
factors affect total impulse such as
pressure, nozzle, grain/core shape, etc, so
it makes sense that they can get a little
more (38Ns, 6.2%) impulse without adding
any propellant mass.
Or maybe they got a Chicago butcher to put
his thumb on the load cell :)
I think the evolution of the 5 grain went like this. Mike Dennett will
correct me if I'm mistaken...
J300 > stay on the cert list until they expire so that motors in the pipeline, i.e.
>> in dealer's or flier's hands, can be used at launches for some time after. >>
>> The current 5 grain 38mm classic propellant motor is the 648J285. The 5
>> grain motor is of more interest/use to most, it seems, as a light J rather
>> than an I. Quite a few have been used for L2 certs due to that fact (mine >> included).
> OK, I'm curious. How do you remove a couple grams of propellant from each of
> 5 slugs in an I motor and end up with a J motor?
> Bob Kaplow NAR # 18L TRA # "Impeach the TRA BoD"
>>>> To reply, remove the TRABoD!
> Save Model Rocketry from the HSA!
The new digs are cool iz. I'm chilling in my old hood (literally - the wind
chill was negative all day yesterday). Instead of helping to run one club's
launches, I now get to fly with (and vend at) 5 Michigan clubs' launches!
Hopefully CATO will catch a break (weather wise) and finally get a launch
off this weekend. Say Hey to the Connecticut gang for me.
You can forget using this motor for the Bowling ball loft ;-)
It was a fluke.
Cesseroni cut their grains down so they weighted 62.5g each. Then had them
They wanted the 5G to be a J class motor for L2 certs so when the testing
revealed it to be an I they tweaked the design to make the J300.
They may only have made one batch of the I360's for cert testing.