Pro38 Friction Fit

[edwardw]

Hey All,

I was wondering how many of you friction fit motors? That's virtually the only way I build mine - I have used blind t-nuts, but I like the friction fit with some 2" masking tape. I'm using Pro38 hardware and am taking out the ejection charges - using and altimeter for deployment. I have yet to have a motor come out the back - and I have had some hefty motors. On my site www.stlrocketry.com the J1383 motor was completely friction fit into the airframe. It didn't fall out and it was a HEAVY motor. I'm guessing it weighed 2+ lbs and at deploy I never had it try and go ballistic. Just wanted to get some ideas on what ya'll thought about friction fit.

Edward

 

[Johnnie]

Edward,

If this is for your L2, I would post this question to whom ever will inspect your rocket before your L2 flight. I know here at HARA, we shun friction fit for cert flights, as a good motor retention system will ease a lot of minds, including that of the flier. If you would like to friction fit for the rest of your flights, that is your choice, but in my opinion, for L2 I would use good motor retention techniques, and get certified first.

Good Luck with your flight

 

[n3tjm]

I friction fit motors all the time... but I do incorperate some sort of motor retention in my larger rockets. I never lost a case, except in the situation of where the ejection charge was to strong for the motor mount in a quest rocket ....

 

[llickteig1]

I have friction fit and still do friction fit SU motors. My feeling, though, is "Why leave anything to chance?" with friction fit?

I paid good money for my motor cases and would like them back. On anything other than minimum diameter it just isn't that hard to add positive motor retention for that bit of extra security.

I also feel like it is a safety issue. When I RSO, if I have any doubt on a friction fit motor, I don't sign the card.

--Lance.

 

[thomasrau]

All of my fleet uses positive retension, mostly slimline retainers with some t-nuts and aeropac's thrown into the mix. I have had to use friction fit from time to time when using AMW cases as they don't always fit my existing retainers. But even then I added a safety tether through the forward eyebolt of the casing which attached it to the rocket as a backup (didn't want to lose a borrowed case)
I know friction fit works well and has been used for years, but adding positive retention can cost little (using t-nuts etc) and gives RSO's a little less to worry about. Besides my biggest fear is hurting someone, making certain the casing(s) stay in the rocket gives me one less thing to worry about.

 

[edwardw]

The friction fit if for an odd shapped rocket - where then end of the motor tube is the back of the rocket. I didn't know exactly how to keept that sucker in there.

For my L1/L2 rocket I used blind t-nuts, until when puting the whole thing together, some epoxy traveled and got into the t-nut and now it cannot be used I'm currently trying to find some really small toggle bolts so I can just use that instead

Edward

 

[Johnnie]

How much of your motor tube protrudes from the back side of your L1/L2?...Hoseclamps put a nice squeeze on motor retention...worked great on my L1 flight.

 

[edwardw]

I don't have any motor tube....I do have a toggle bolt/washer system for that rocket...I'm thinking of adding two, just to be sure. I mean for less than $1 you can keep the casing in there...

Edward