Quantcast

Questions/advice???

The Rocketry Forum

Help Support The Rocketry Forum:

Steward

Well-Known Member
Joined
Jan 18, 2009
Messages
871
Reaction score
1

My son is ready to begin building his "BIG BERTHA".
I'd really like to convert it to 29mm...Question...would 1/8 balsa work for the engine mount centering rings/bulkheads? I have the balsa on hand...BTW I've just finished the 29mm motor mount for my "VENUS PROBE" so I'm comfortable building outside the box.

We would like to go with the mount large enough for the "E" size motors and then adapt it down to "D" for smaller fields...When I showed my son the size of the "E" all he could say is "OH YEAH...!!!"...Advice??? TIA... Steward
 

jetra2

Well-Known Member
Joined
Jan 25, 2009
Messages
2,792
Reaction score
2
Steward,

What I do sometimes, especially if i want to make a balsa centering ring set or bulkhead, is do what I like to call the "balsa ply" method. What it involves is taking three pieces of your choice of balsa thickness, then layer them up and clamp them together.

1. Choose three pieces of balsa, still square.
2. Spread yellow glue, epoxy, or Gorilla glue on each piece
3. Layer up the balsa at opposing angles, i.e., vertical, horizontal, vertical.
4. Set your now completed, but not finished, balsa play bulkhead or CR under a stack of VERY heavy books or clamp it in a vise for at least 12 hours.

After this, you will be able to make CR out of them by drilling out the MMT hole and cutting and sanding to fit the outside. An option you might want to consider is, for some EXTREME strength, for bulkheads only, I would advise, is to use epoxy and put a layer of fiberglass in between each layer. Talk about a lot of strength! :cool:

Jason
 

Joel E.

Member
Joined
Oct 9, 2003
Messages
10
Reaction score
0
Check the advice posted about two months ago in "18mm Motor Mount Adapter Question." My advice would be to definately built the BB with the larger engine mount because flying a D powered BB is a lot of fun. The flight is quite impressive. Of my BB's six total launches - I finished building it two weeks ago - three have been on D engines. I have not yet dared to send my BB up on an E engine. My guess is that she will go nearly out of sight. This simple modification is well worth the effort.
 

loopy

Well-Known Member
Joined
Dec 13, 2009
Messages
4,570
Reaction score
1
I'm guessing when you say 29mm you actually mean 24mm? If that's the case, then yes, you should be fine. You might coat them with epoxy just to make them stronger if you decide to put 24mm reloads in them for more power. Also I recommend using LOC or similar motor tube to handle the heat of the composite reloads.

Loopy
 

Steward

Well-Known Member
Joined
Jan 18, 2009
Messages
871
Reaction score
1

You're right loopy...that was my intention...I've had entirely too much cold and flu medicine this week...I indeed meant 24mm. Funny though...about the same time I posted this thread...another one just the same appeared...!!! Guess everyone is "movin' on up"...LOL Thanks...!!!
 

eugenefl

Well-Known Member
Joined
Apr 22, 2009
Messages
4,344
Reaction score
6
Originally posted by n3tjm
29mm Big Bertha is a cool idea... would fly great on G25 motors :).
Doug, if you could fit a J into a 13mm Mosquito you'd do it. :p

The Big Bertha is slow and very true to a real rocket lift-off on a C6. I see the craving for more power has struck. A D will certainly get it up there in a hurry. Let us know how it goes.

I agree with the consensus. A stock built BB should be fine on Estes D and E power. If you get into E15+ territory, then you may consider using epoxy here and there to stiffen up the joints a tad.

Good luck!

PS - For something really unique and something that requires no extra MMT parts, use 3 "A-C" sized motor tubes and cluster that bad boy! Three 18mm (A-C) tubes glued together fit snug and perfectly in a BT60 (1.637") tube.

Have fun!
 

sandman

Well-Known Member
Joined
Jan 18, 2009
Messages
10,468
Reaction score
5
PS - For something really unique and something that requires no extra MMT parts, use 3 "A-C" sized motor tubes and cluster that bad boy! Three 18mm (A-C) tubes glued together fit snug and perfectly in a BT80 (1.637") tube.
jetra2,

Then it's not a Big Bertha anymore.

That would be an Astron Ranger!

http://www.dars.org/jimz/k-06.htm

Still a cool rocket!

My Mini-Quad kit has a 13mm 3 engine cluster mini version of that!

sandman
 

eugenefl

Well-Known Member
Joined
Apr 22, 2009
Messages
4,344
Reaction score
6
Originally posted by sandman
jetra2,

Then it's not a Big Bertha anymore.

That would be an Astron Ranger!

http://www.dars.org/jimz/k-06.htm

Still a cool rocket!

My Mini-Quad kit has a 13mm 3 engine cluster mini version of that!

sandman
Uh, you mean Eugene? ;)

Yep, that's right. I know about the Ranger. I guess I was still a seedling back then. :p :D
 

sandman

Well-Known Member
Joined
Jan 18, 2009
Messages
10,468
Reaction score
5
Oops...my bad...LOL!

Seedling...heck jetra yer DAD was a seedling then!

sandman
 

NewEntity1

Well-Known Member
Joined
Dec 4, 2003
Messages
273
Reaction score
0
Heh Heh, what a coincidence...On another thread I was also talking about my intentions of converting a Big Bertha to use a 24 mm engine mount instead of the stock 18 mm mount...must be a popular 'mod' :)

I would be restricting it entirely to Estes black-powder engines, though...the rocket strikes me as being to light to withstand any composite motors.

Note: message edited for clarity; first version didn't sound right .
:eek:
 

jflis

Well-Known Member
Joined
Jan 18, 2009
Messages
15,353
Reaction score
34
Originally posted by eugenefl


PS - For something really unique and something that requires no extra MMT parts, use 3 "A-C" sized motor tubes and cluster that bad boy! Three 18mm (A-C) tubes glued together fit snug and perfectly in a BT80 (1.637") tube.

Have fun!
Eugenio,

That would be a BT60 (the BT80 has a 2.6" OD)

As for conversion, again the FlisKits EMK-24-60 motor mount kit is all you need!

jim
 

NewEntity1

Well-Known Member
Joined
Dec 4, 2003
Messages
273
Reaction score
0
Mr. Flis sir:

I will be buying a *couple* of those motor mounts you mentioned, as well as some elastic shock cord and other miscellaneous parts, plus a praetor as well. I want to buy all these items at one time, so my charges don't consist primarily of shipping.

However, I am goin to hold off until the stuff I already ordered from A2Z Hobbies comes in, or I at least get a UPS shipping tracking number from them.

So tell A2Z to get off their butts and get me that number :D .

PS: If it seems like I'm posting a lot today, its because I'm at home sick...stupid bugs going around :( .
 

jflis

Well-Known Member
Joined
Jan 18, 2009
Messages
15,353
Reaction score
34
Originally posted by NewEntity1
Mr. Flis sir:

I will be buying a *couple* of those motor mounts you mentioned, as well as some elastic shock cord and other miscellaneous parts, plus a praetor as well. I want to buy all these items at one time, so my charges don't consist primarily of shipping.

However, I am goin to hold off until the stuff I already ordered from A2Z Hobbies comes in, or I at least get a UPS shipping tracking number from them.

So tell A2Z to get off their butts and get me that number :D .

PS: If it seems like I'm posting a lot today, its because I'm at home sick...stupid bugs going around :( .
not a problem, the part's'll still be here :) As for A2Z, give'm a chance, they'll come through for you. Couple of good guys there :)

Now, about you posting so much.... ...well, no I'm certainly not the one to comment on how much someone posts around here... :p
 

Steward

Well-Known Member
Joined
Jan 18, 2009
Messages
871
Reaction score
1


I guess it's better late than never....
anyway, it's almost ready to go....

 

Latest posts

Top