friction fitting?

[Schuyler]

I'm just about to finish my first mid-power kit, the Red River Merlin, and I'm wondering about motor retention. I bought a reload casing from Apogee and they told me that it was OK to "friction fit" it by wrapping tape around. It makes me a little nervous because that casing cost me almost $80. Is this method really reliable? If so, how tight does it need to be to stay in place?

 

[Conan4480]

I have used friction fitting on several rockets. As long as it is a tight fit you should have no problems.

If you are worried about it then you can add positive motor retention to the rocket. Home Depot and Lowes sells insert you can glue into the aft centering ring to add screws with washers or the Kaplow style clips. That is if you have enough space on the centering ring to put those in.

Lynn

 

[skycopp]

To be honest with you, i wouldn't recommend only friction fitting. Some people generally don't have problems with friction fitting, but I've lost several cases using only friction fitting. Therefore I would recommend friction fitting in addition to some other positive retention.
I have a trick in which I tie a piece of strong string to the top of the motor at the ejection well. Then I wrap electrical tape around it a few times. The other end of the string is then fished up the motor tube and tied to the shock cord. If the motor gets kicked out, the string will hang onto the case. This has saved me several times.

 

[KHamel]

I have used friction fitting many times with great success. In addition to friction fitting I also tape aft end of the motor to the aft end of the motor tube.

Skycopp has given some great advice also. I will be trying that at some point.

 

[Schuyler]

I like Skycopp's idea. The only problem with this rocket is that it has a baffle so I can't connect it to the shock cord. Maybe I could figure out something similar though.

 

[Handeman]

Another thing that can be done if you can't put a threaded insert into the aft centering ring, is use wire loops. On one of my rockets, I trimmed large paper clips and epoxied them into the fin fillets so the loop extended about 1/4" below the bottom of the BT. I then use some 20 to 24 ga. copper wire throught the loops and around the nozzle and twist them together.

It doesn't look the best, but it sure works well. In fact, when I lost the nose cone during main deployment on my L2 attempt I had to try again. Instead of using another K motor in a 54mm casing, I used a J420R in a 38mm. When I installed the motor and adapter, I didn't have any clips that would work. I used the copper wire from each retaining screw and around the nozzle instead. It worked great. It was a good thing too, because the casing was borrowed.

 

[jimzcatz]

I have been using tape forever,on everything from minis to the great L-750. Also on all my reloads. The reason you have lost hardware is because they were not in tight enough,plus you may have put to strong of an ejection charge in. And get rid of the baffles,JMHO. The baffles make it easier to lose hardware.Remember guys,before there were so many members across this great land of ours,we relied on the advice of each other,which is what we are doing now. Im not preaching here,but in the old days,tape was an essential tool in the range box. Dont be afraid to use tape for retention or thrust rings,it WILL work,trust me.

 

[MitchR]

I've never had any issues with friction fitting, I just always make sure it's done right. If you are friction fitting larger motors like J+ I highly recommend you bring something to aid you getting your case OUT of the tube when your flight is over. haha =)

There are cheap alternatives though that are more reliable, if you're seeking other alternatives.

 

[madsen]

The reason you have lost hardware is because they were not in tight enough. in the old days,tape was an essential tool in the range box. Dont be afraid to use tape for retention or thrust rings,it WILL work,trust me.

I agree. I also agree with the comment about bringing someone along to help get the motor out. If you use any amount of maskiing tape--the heat from the motor will melt the adhesive--and that will hold the motor in place. If you have a tight fit going in--it will be a super tight fit pulling out. Just be sure to remove the motor as soon as possible. Once the adhesive cools--forget it.

 

[jimzcatz]

I agree. I also agree with the comment about bringing someone along to help get the motor out. If you use any amount of maskiing tape--the heat from the motor will melt the adhesive--and that will hold the motor in place. If you have a tight fit going in--it will be a super tight fit pulling out. Just be sure to remove the motor as soon as possible. Once the adhesive cools--forget it.

I have found the opposite to be true. If the motor has cooled,it usually comes out easy. I guess I should have been more specific. Most of my tape fits are in paper adapters. I friction fit the adapter into the MMT,and there usually is enough of the adapter MMT to allow me to wrap tape around the forward end of the casing.

 

[dpower]

..In addition to friction fitting I also tape aft end of the motor to the aft end of the motor tube...

This is the key to retaining RMS casings with tape (at least for the mid-power hobby-line casings). Use a full wrap of regular 1" wide masking tape around the exposed motor tube and aft closure ring. I like the motor tube to protrude at least 1/2" from the aft CR for this method so the tape has plenty of surface area to grab.

 

[jimzcatz]

I like the motor tube to protrude at least 1/2" from the aft CR for this method so the tape has plenty of surface area to grab.

No,no,no.... All my rockets are flush on the aft end. Otherwise landings destroy that little bit of tube left exposed.

 

[Schuyler]

Does anyone have an opinion on Aero Pack retainers? The only obvious problem I can see is that they are quite expensive.

 

[blackjack2564]

Does anyone have an opinion on Aero Pack retainers? The only obvious problem I can see is that they are quite expensive.

Once you use one, you won't go back. I have them on most of my rockets. They can be recycled if you crash a rocket, to another one.
Larger motor mount sizes can be adapted down with ease, to use adapters that just slide in. 38mm to 29mm for instance.

Also I friction fit upon occasion too, a good idea is to write your name,ph
#, and club on the tape,in case it does get lost. Twice they have found their way back to me several months later when found.

 

[Bill P]

Does anyone have an opinion on Aero Pack retainers? The only obvious problem I can see is that they are quite expensive.

AeroPack retainers are great. As blackjack said, "Once you use one, you won't go back."

They may be a little pricey but they are cheaper than a motor casing.