Do you need a thrust ring?

[Bone Daddy]

If you friction fit a low power rocket motor, do you need a thrust ring?

Just curious.

 

[gpoehlein]

Actually, a couple wraps of tape around the aft end of the motor can double for a thrust right. That's what I'm doing in my latest A cluster altitude model for an upcoming contest. I also left out the anchor for the shock cord - I will tie that around the central motor on the outside of the body tube, add a couple wraps of tape for a thrust ring and tape the motor into the rocket.

I'm pretty pleased with the build - it is made from astrobright 67# cardstock, soaked with CA and sanded supersmooth.

 

[ScrapDaddy]

friction fitting for anything is a no-no for me i always think its enough but it never is.......... wishhhhhhhhhh pop (engine hits ground)
but no engine block because in the entire 13mm/128mm motors there are ones that are longer than the "standard"

 

[gpoehlein]

Most of my contest models are friction fit, but rather than wrap tape around the motor to make the fit tight, I wrap tape around the aft end of the rocket and motor. This makes a solid connection between rocket and motor and, if the tape is good quality (try Tamiya masking tape) it won't let go.

On the other hand, I use tape wrapped motors in my Ranger clone (three motor cluster). I've flown it about a half dozen times so far and not kicked a motor yet. The trick seems to be putting the tape on the front of the motor. This is the part of the motor that doesn't swell as the motor fires, so you can get the fit nice and tight and the motor won't swell so much you can't remove it after the flight. Add just enough tape to make it hard to get in with a twisting motion.

 

[MarkII]

If you friction fit a low power rocket motor, do you need a thrust ring?

Just curious.

Although I have never tried it, I suspect that you can get away with just friction fitting the motor into a tube that lacks a thrust ring if you are using 13mm 1/2A or 1/4A motors. Just make sure that the fit is firm. I think that in those situations, the greater risk is that the motor will kick when the ejection charge fires. I wouldn't recommend doing this with Micromaxx motors, though, because they have pretty hefty thrust spikes for their size. The same is definitely true of 13mm A10 motors.

Of course, you never have to use a thrust ring in a rocket such as an Estes Mosquito, Astron Sprite, Astron Scout or a FlisKits Tumble Weed. The motors in those designs stop up against the base of the nose cone.

ADDENDUM: I forgot - the motor mount in my AAW Popsicle Stick monocopter has no thrust ring. I have flown it on 13mm A3 and A10 motors without taping the motor to the mount and without making a tape thrust ring; IOW, nothing but friction was keeping the motors in the mount. Yet in flight after flight, none of the motors budged a millimeter. It probably helps that the motor mount (actually, it's just a sleeve) in mine is rather tight. But if the motor can get the craft going without having to overcome very much inertia, then friction (good firm friction) might often be enough to keep it in place. I wouldn't try it with anything larger than 13mm A motors, though.

MarkII

 

[green dragon]

I've flown many birds with friction fit motors through D12's .

If you make sure the fit is nice - then the motor will nto slide forward, or kick out at ejection.

Especially on contest flights where we want to save weight, I always leave out engine blocks and friction fit. ( although been years snce I cojmpeted ) .

I would nto try it with a high thrust motor, but for any normal modroc motors, no worries.

~ AL

 

[cwbullet]

I have done it up to a G, but would reccomend against it.

 

[Micromeister]

Low power models do not require a thurst ring. They are nice motor stops but once you have learned how to friction fit and/or are using an external wrap around the motor/motor mount tube they are no longer all that important. Personally I use motor stops in minimum diameter models more as shockcord mounting point then motor stops

 

[Bone Daddy]

Thanks everyone.

 

[Neutronium95]

I use tape thrust rings and tape to friction fit on everything up to "F" motors, and I have never had a problem.