Which dimensional drawing is actually true
- Thread starter Just_Another
- Start date
Help Support The Rocketry Forum:
NTP2
Well-Known Member
they are 2 sheets of the same drawing. The first is a assembly and the second is a actual dimension drawing.
Just_Another
Member
Are you sure because first ones nozzle looks a lot more longer?
Then i have to make my design as taking reference second one?
NTP2
Well-Known Member
The first is probably for the specific motor and the other is probably a general design for all 29mm models.
Ps yup you should use the last one.
rharshberger
Well-Known Member
One has a Medusa nozzle (shorter, multiple nozzles), the other is a standard single port nozzle hence its longer...both could be correct depending on the age of your particular motor. The single port nozzle is the newer version iirc.
The one on the right is the drawing for the casing you'll use (ignore the nozzle/fuel grains), the one on the left is the assembly drawing showing the actual nozzle/grains and the forward seal disk. Both drawings are correct.
Just_Another
Member
First they gave us second one then they deleted that and added a open rocket file because the one in the app's itself wrong then they gave us first one i don't know what the hell are they doing.
Thanks for replying i really appreciate
Just_Another
Member
Then i will use second one? Sorry my english isn't that good
NTP2
Well-Known Member
Just_Another
Member
They gave us first one at last. The first ones lenghts same as second one then except nozzle?
This response is correct:
Multi-throat medusa nozzle:
Single throat nozzle:
Both use the same motor case, the one you get will depend on the manufacture date of the reload kit.
Ask your motor supplier if it will be the single-throat nozzle.
Just_Another
Member
Turkish
Just_Another
Member
Probably single throat. In other hand except nozzle all other parts are the same? Then do you know where can i find the lenghts of single throat nozzle?
NTP2
Well-Known Member
Cool!
Just_Another
Member
Thanks!
According to the reload kit drawing, part #3, it’s a 75mm single throat, 0.685” dia
Double check me.
https://d11fdyfhxcs9cr.cloudfront.net/templates/170652/myimages/rcs_01770_nozzle_dwg.pdf
Just_Another
Member
Does 2.730 DIA means 2.73 inches?
Yes.
Just_Another
Member
Does both forward seal disks are the same? It's important because i'll design my engine block according to that.
Just_Another
Member
And one last question does both forward seal disks and rest of the motor (case ect.) are same as second one. I'm sorry if i'm repeating myself. I'm very nervous right now because i don't wanna make any mistakes and thanks again for responsing.
Never assume that because a motor case has a designated size, that the designated size is the ACTUAL size.
The case size for the 75 reloadable cases is ACTUALLY slightly over 75mm. 2.965 x 25.4= 75.31mm. It was PROBABLY made from 3"OD material and machined down to clean it up from the 3" extruded aluminium. The cleaned up size being just over 75mm. NOT 75mm.
The Aerotech drawings for the designated case sizes are correct for the Aerotech cases.
If a motor is a SINGLE USE motor, who knows.....
The case size for the 75 reloadable cases is ACTUALLY slightly over 75mm. 2.965 x 25.4= 75.31mm. It was PROBABLY made from 3"OD material and machined down to clean it up from the 3" extruded aluminium. The cleaned up size being just over 75mm. NOT 75mm.
The Aerotech drawings for the designated case sizes are correct for the Aerotech cases.
If a motor is a SINGLE USE motor, who knows.....
Hi, I am curious just what you are trying to build for this motor case. A motor mount tube? Also what do you mean by engine block? The item to keep the motor case from flying out the front of the rocket?
Just_Another
Member
Yes i heard and because of that i was planning to give tolerance to engine mount about 1-2 mm but before, i have to be sure about lenghts of the motor and that's where all my problems. Start thanks for advice tho.
Just_Another
Member
Yes exactly!
The aft closure has an integrated thrust ring (gold in the image below) for this purpose.
Just_Another
Member
But isn't i have to still attach motor to the rockets itself? Actually it has attached from the front closure but this is for extra safety.
Just_Another
Member
This is the old one right?
The 75/3840 “motor hardware” is the same for all loads that fit that 75/3840 case. It hasn’t changed. The hardware is: the 75mm/3840 N-sec case, the forward seal disc, the forward closure and the aft closure. The aft closure will work with either nozzle type. These parts are reusable many times and for many years if you don’t lose them.
The L1520 “motor” is a kit with the fuel grains, the nozzle and the consumable internal components needed. All of that goes inside the 75/3820 motor hardware. This stuff, or what’s left of it, goes in the trash after the rocket is recovered.
Last edited:
If the motor hardware you buy has the "Screw Eye" optional front closure you can use that as an "extra" safety margin.
You generally use this to hold the motor case in from the rear>
https://aeropack.net/pages/motor-retainers
What are the goals from the contest you must perform?
Just_Another
Member
I want to go over the topic again. First ones and the second ones case is actually the same but because the first one is for a spesific rocket motor (L1256), nozzle look different. But except nozzle all other lenghts are the same because as i said they use same case as 75/3840 am i right?
Similar threads
