Motor Mounts, Yeah, Nay or Meh

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lakeroadster

When in doubt... build hell-for-stout!
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Do most of you use engine hooks and motor mounts?

Member Kuirin was educating me on my introduction thread about folks using tape on the back of the engine as an engine block, and then using tape to attach the engine to the body tube.

That just seems so, well, haphazard. But I haven't launched a rocket since the mid 1980's.. so what do I know :surprised:.

But I did find an article on it in the Apogee Peak Of Flight data base.. so maybe this is a great trick for this old dog to learn?

For the scratch built X-wing I am building the tape method would allow me to use either C or D engines.. which would be nice. But I sure don't want the engine to pop out at ejection due to a tape failure.

Any sage advice for a Born Again Rocketeer is sincerely appreciated.
 
I frequently don't use motor hooks or motor blocks because they limit my motor length options, I let most of my motor mount tubes project beyond the airframe tube by .25" to .5" then use a combination of friction fit (tape around the motor to make it snug in mmt) then a wrap or two of masking tape around the mmt and projecting portion of the motor as insurance, haven't popped a motor out at ejection since adding the tape wrap with friction fit. If using motors without thrust rings like Estes BP motors I make one with 5 or 6 wraps of masking tape around the botton .25" of the motor then trim the excess off with an X-Acto knife.

Kuirin and I may use the same methods from the sounds of it.
 
Low power, Estes B, C & D

At that size I personally just go with the stock Estes style- if 24mm, just make sure you leave 3 3/4" of inside space for longer motors. I personally won't fly a CTI 24mm G anytime soon unless it's a specalized performance rocket (they're about 8" long), so I limit my motor mounts to the Estes E length, which also covers Aerotech F's.

I'm not personally a huge fan of tape for retention of any kind- I'd rather stick with mechanical retention and save myself a bit of worry. That's just me though.
 
Tape works fine for me on low power micromaxx thru D.

Tip: if you can leave about 1/2 inch of motor mount sticking out, after you paint your rocket put a wrap of clear cellophane tape around the exposed part of the mount (clear so doesn’t mess up your paint scheme.). Motor then sticks out of mount say 1/4 inch. Once motor is in, a single wrap of masking tape that overlaps both the mount and the exposed motor works fine for me. The underlying cellophane tape make sure the wrap tape comes off clean after the flight and doesn’t peel off your paint.
 
Tip: if you can leave about 1/2 inch of motor mount sticking out, after you paint your rocket put a wrap of clear cellophane tape around the exposed part of the mount (clear so doesn’t mess up your paint scheme.). Motor then sticks out of mount say 1/4 inch. Once motor is in, a single wrap of masking tape that overlaps both the mount and the exposed motor works fine for me. The underlying cellophane tape make sure the wrap tape comes off clean after the flight and doesn’t peel off your paint.

I agree. Great method.
 
Builders preference. Tape just works (for me :) ), my experience includes up to Aerotech F impulse. And it appeals to my frugal (cheapskate) sensibilities as well. No wrong answer here.

My uprated Estes Patriot uses tape to retain the F15-8.

IMG_0991.jpg IMG_0992.jpgIMG_0993.jpg



Of course, sometimes you just gotta have a slick aluminum retainer. Choices ! :grin:


rocketarium 18mm retainer.jpg


Rocketarium is one place get'um: https://www.rocketarium.com/Build/Motor-Retainers
 
Alternatively, if you are mainly using 24mm C and D engines, and would like to occasionally use the longer E engines, then construct the motor mount with the longer "E" engine hook (3 3/4") instead of the shorter standard hook, and use a 1" spacer when flying the shorter motors. This can either be the orange spacer sold by Estes and which comes in many of their 24mm powered kits, or a homemade one cut from an expended 24mm casing. As I said, for low power 18mm rockets you may want to use the hook/thrust ring system for the convenience, since the motor length does not vary. But for larger motors where the length can vary the tape system is cheap and it works, and allows you to use all lengths of engines.

Aluminum retainers are great, but I'm a cheapo so I use the plastic ones by Estes.

P.S. Forgot to add, always check for stability when doing any mod that may affect cg or cp location. That includes using non recommended motors.
 
Do most of you use engine hooks and motor mounts?

Member Kuirin was educating me on my introduction thread about folks using tape on the back of the engine as an engine block, and then using tape to attach the engine to the body tube.

That just seems so, well, haphazard. But I haven't launched a rocket since the mid 1980's.. so what do I know :surprised:.

Yes to all of the above, depending on the intended use of the rocket.
Low power:
- If my kids, or me, build something funky looking, full of non-functional embellishments (Scorpion, Crossbow, QuinStar, etc) that will never see composite re-usable motors, we stick the engine block with the hook, and call it done. That way, they can swap in Estes single-use motors in and out and launch their rockets all on their own.
- If the rocket is likely to see an AT 18mm reusable motor, then I always use a proper motor retainer. Either from Aeropack, or something home made. I had lost one reusable motor in the past that only relied on friction fitment, don't want to repeat that.
- If we have any interest in seeing how high the rocket can possibly go, or at least it looks like it can go high, we always omit the motor hook. Then we either use tape to hold single-use motors to the tube, or eventually, install a motor retainer.

Overall, it's about 1/3, 1/3, 1/3 across the low-power rocket fleet.

For Mid- and High-power rockets, it's motor retainers 100% of the time.

Partly because 24/29mm plastic Estes retainers are dirt cheap, and Aeropack look great, and are not that expensive.
Mostly because I really don't want to loose the reusable motors, or entertain the thought of them ejecting down, towards the spectators, during launch.



For the scratch built X-wing I am building the tape method would allow me to use either C or D engines.. which would be nice. But I sure don't want the engine to pop out at ejection due to a tape failure.

Sounds like you are planning to rely on 24mm single-use motors.
I would stick an Estes plastic retainer in there, and put a thin layer of tape on the end of Estes SU motor to create a "lip" for motor retainer to hold:
https://www.rocketarium.com/Build/Motor-Retainers/24-mm-plastic
https://www.hobbylinc.com/estes-24m...4bncBf57BIq1xppFdi2A20Dz37ZwIKNBoCb7EQAvD_BwE

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Thanks for the advice and comments... much appreciated.

So for those that "tape" ... what brand and type of tape are you using?
 
The cheap kind at the Dollar Store. It's not overly thick and you can build layers to get that "just right"fit.
 
I follow Wildman Tim’s Second Law: No Engine Blocks! I used to think that 13mm motors were exempt - until I bought a case of 13mm Centuri Bs. Now I don’t put a motor block in anything. Tape thrust rings for all sizes.

I’ve 3D printed Estes-style retainers for 13-38mm mounts. Down at 13 and 18mm, they add a lot of poorly placed mass.

For 13-24mm, I often use an engine hook. I bend the upper hook backwards and put a centering ring under it to take the aftward ejection force. Makes a good place to anchor the shock cord, too. I will wrap a little tape around the motor, over the hook, for AT 24/40 casings, just to make sure it can’t slip out.
 
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