Aerotech mid power thrust ring

[brennant]

I recently bought the Aerotech Cheetah and do not want to use the engine hook. Instead, I am using an Estes motor retainer. The Aerotech instructions say to slide the thrust ring till it hits the motor hook’s end. Can I get rid of the thrust ring or do I need to use the motor retainer?

 

[afadeev]

I recently bought the Aerotech Cheetah and do not want to use the engine hook. Instead, I am using an Estes motor retainer.

Good choice!

The Aerotech instructions say to slide the thrust ring till it hits the motor hook’s end. Can I get rid of the thrust ring or do I need to use the motor retainer?

Thrust ring is there to keep an engine from shooting through the motor mount upon ignition. It is not directly tied to hook vs. positive retainer choice. The downside to the thrust ring/block is that it limits the length of the motors you can fit into your rocket.

Most modern non-Estes rocket motors come with a "lip" on the aft end of the motor that achieves the same goal - transfer thrust of the motor to the motor mount/airframe.


If yours doesn't (e.g.: Estes BP motors), you can build up a "lip" by taping a few layers of masking or striping tape. Works just as well.
I bought a roll of 1/8" automotive striping vinyl tape that greatly simplifies this process, but you can achieve the same result by cutting and applying thin strips of regular masking tape:
https://www.ebay.com/itm/383501971647?hash=item594a7fb0bf:g:CnwAAOxyLm9TAe-F
HTH,
a

 

[brennant]

Hello, thank you for responding I think I will omit the thrust ring. Thank you for the advice

 

[CrazyModelGuy]

Why not just get the Aeropack retainer. Its easy to install. And from what ive read it prevents both forward and rearward movement of the motor.

 

[ThirstyBarbarian]

I don’t know about Aerotech’s instructions, but usually the term for the ring that gets glued in place inside the motor mount tube is “motor block”. And the term “thrust ring” is used for the ring of material that’s molded to the aft end of the motor or the part of the casing that keeps the motor from going forward into the motor mount tube and also is held by the motor retainer to keep the motor from falling out of the tube. Motor block is part of the motor mount, and thrust ring is part of the motor, but some people do sometimes refer to the block as a thrust ring.

The advantage of using motors with thrust rings is that you don’t need a motor block, and you can use many different lengths of motors. It sounds like you decided not to use a motor block, and that’s definitely what I would recommend.

 

[ThirstyBarbarian]

Why not just get the Aeropack retainer. Its easy to install. And from what ive read it prevents both forward and rearward movement of the motor.

The Estes 29mm screw-on plastic motor retainer is just as easy to install and use, and it costs a lot less. That’s what I’ve used when upgrading the retainers on 29mm motor mounts.

 

[CrazyModelGuy]

The Estes 29mm screw-on plastic motor retainer is just as easy to install and use, and it costs a lot less. That’s what I’ve used when upgrading the retainers on 29mm motor mounts.

Im just saying I purchased the aluminum one for durability. Plastic, heat and pressure dont usually go well together. But to each their own.

 

[brennant]

I don’t know about Aerotech’s instructions, but usually the term for the ring that gets glued in place inside the motor mount tube is “motor block”. And the term “thrust ring” is used for the ring of material that’s molded to the aft end of the motor or the part of the casing that keeps the motor from going forward into the motor mount tube and also is held by the motor retainer to keep the motor from falling out of the tube. Motor block is part of the motor mount, and thrust ring is part of the motor, but some people do sometimes refer to the block as a thrust ring.

The advantage of using motors with thrust rings is that you don’t need a motor block, and you can use many different lengths of motors. It sounds like you decided not to use a motor block, and that’s definitely what I would recommend.

Yes, I decided to not use the motor block.

 

[ThirstyBarbarian]

Im just saying I purchased the aluminum one for durability. Plastic, heat and pressure dont usually go well together. But to each their own.

The Estes plastic threaded retainers are plenty durable. I’ve used them on every 29mm rocket I’ve flown since the Estes PSII kits came out around 7 years ago. Hundreds of flights. I’ve never had one fail.

The screw-on cap has gotten a little bit toasted on a few, but not to the point of needing replacement. It’s basically cosmetic. Over time you get a surplus of caps from rockets that have been damaged as long as you save the cap when you dispose of the rest of the rocket, so you can use the freshest-looking ones if it matters to you.

The Estes threaded retainers are about $8 for a 2-pack, so around $4 each. An Aero Pack retainer assembly is over $20, closer to $25. They are nice. I have bought them for 38mm and 54mm motor mounts. But for me it would have to be a very special rocket to spend that much for a 29mm retainer.

 

[steveh.jae]

Good choice!



Thrust ring is there to keep an engine from shooting through the motor mount upon ignition. It is not directly tied to hook vs. positive retainer choice. The downside to the thrust ring/block is that it limits the length of the motors you can fit into your rocket.

Most modern non-Estes rocket motors come with a "lip" on the aft end of the motor that achieves the same goal - transfer thrust of the motor to the motor mount/airframe.
View attachment 471315

If yours doesn't (e.g.: Estes BP motors), you can build up a "lip" by taping a few layers of masking or striping tape. Works just as well.
I bought a roll of 1/8" automotive striping vinyl tape that greatly simplifies this process, but you can achieve the same result by cutting and applying thin strips of regular masking tape:
https://www.ebay.com/itm/383501971647?hash=item594a7fb0bf:g:CnwAAOxyLm9TAe-F
HTH,
a

Could you not mount a permanent motor block set to the maximum length of the motor selections and retain the ability to use all sizes by utilizing multiple (tube) spacers of varying lengths?

 

[MidOH]

Sure can. But I have no idea what motors I'll be running.

The Estes Highfler XL has a block set for E's, and includes a spacer for D's. I set mine up with nothing though. Tape ring and friction fit. Olde school.

So just tape rings and friction fit for me on my small stuff. Maybe an Al retainer on my MPR's, since they'll use reloadable motors.

 

[jrap330]

Sure can. But I have no idea what motors I'll be running.

The Estes Highfler XL has a block set for E's, and includes a spacer for D's. I set mine up with nothing though. Tape ring and friction fit. Olde school.

So just tape rings and friction fit for me on my small stuff. Maybe an Al retainer on my MPR's, since they'll use reloadable motors.

Have you flown a Highflyer on an E Or Higher Engine? And recovered it?

 

[MidOH]

Not yet. D was cake.

I have a Apogee bt60 dual deployment extension almost ready for one of them. That'll be a streamer then an 18" chute with its center cut out.

 

[DES]

I have a Hi-Flyer XL. I did install the motor block, positioned for Estes blackpower E motors. But I typically fly it with either D motors, using the cardboard spacer Estes provides with the kit.

I have flown it with an Aerotech composite E, and it that case, the thrust ring on the motor fits inside the screw on motor retainer. And I did get the rocket back. Flight was on a big frozen lake in the winter, and since there is snow covering the ice, I use smaller than typical parachutes.

 

[ThirstyBarbarian]

Could you not mount a permanent motor block set to the maximum length of the motor selections and retain the ability to use all sizes by utilizing multiple (tube) spacers of varying lengths?

I think part of what the OP wanted to accomplish was to get rid of the motor hook. Most hook designs have a piece at the forward end that pokes through the motor mount tube and limits the length of the motors, even if no block is installed. Hooks and blocks are good for motors that have no thrust rings and a set length (or two lengths with a spacer), basically Estes motors. If you are using a motor system with a thrust ring, screw-on retainers are nicer than hooks, and no motor block is required, so it’s better to leave it out.

 

[afadeev]

Could you not mount a permanent motor block set to the maximum length of the motor selections and retain the ability to use all sizes by utilizing multiple (tube) spacers of varying lengths?

Mostly "yes", if you only plan to fly one type of motors (e.g.: Estes BP only).
If you start mixing and matching Estes vs. AT vs. Quest vs. CTI motors, you will find that their length and ejection canister shapes all differ. Thus, you would be committing to maintaining and managing a very long inventory of spacers of different lengths and diameters for different motors. This will be come a major PITA before too long.

The other thing to keep in mind is that as you start flying higher thrust motors, the Estes metal hook-type retainer will become inadequate. I've spit out multiple 18mm RMS motors, which is highly undesirable for cost reasons, but also because a motor that ejects out the back end is likely coinciding with failure to eject the nose cone and the chute out of the forward end of the airframe.
Long story short, positive motor retention with dedicated motor retainers JB-Welded to the aft end of the motor mount are way more reliable and desirable. They are slightly more expensive, but even Estes now sells them, on a side.

An all around simpler solution is to transfer the motor thrust via the "thrust ring" on the motor itself, and call it done. Those are included on most of the higher thrust motors, and you can easily add them to the Estes BP motors on your own.
Couple that with a positive motor retainer (Estes, AeroPack, something else), and you will be flying reliably and safely all your 18mm though 98mm motors !

HTH,
a

P.S.: There are a few exotic kits where a positive motor retainer simply will not fit. Usually, due to some decorative elements on the aft end of a rocket (e.g.: tail cone), or due to performance reasons on competition airframes. In those cases, I install the motor stocking a 1/4" out the tail end of the motor mount, and tape it in place with masking tape.

 

[jimzcatz]

tape thrust ring and friction fit retention works on motors up to and including O. I have seen it and done it with multiple K and L motors.Trust the tape!!!