Aluminum 18mm motor retainers

[mh9162013]

I love the Estes plastic 18mm screw-on motor retainers. However, because they're plastic, they're a bit larger than their aluminum counterparts, such as the one from Rocketarium.

I'd like to use the Estes 18mm retainers on my BT-50 rockets, but the fact that they're a smidge wider than the BT-50 tubing bugs me. Based on my online research, it appears that the OD of the 18mm retainer from Rocketarium is narrower (by about 1-2mm) than the OD of Estes BT-50 tubing. Assuming this is correct, here's my question:

Is the OD of the Rocketarium 18mm retainer less than the ID of Estes BT-50 tubing? In other words, would the Rocketarium 18mm retainer fit INSIDE Estes BT-50 tubing?

This is a specific question, so maybe I won't get a definitive answer unless I try things out myself. But maybe someone here already knows the answer, hence this post.

 

[SolarYellow]

A member recently PM'ed me this info:

...the knob of Rocketarium's 18mm retainer is 24.4mm OD, that of their 24mm retainer is 31.2mm OD, and that of the Giant Leap Slimline retainer is 36.2mm OD (site claims 36.4mm, but the two I've measured were 36.2).

BT-50 ID is 24.1mm, OD is 24.8mm.

BT-55 ID is 32.6mm, OD is 33.7mm.

BT-60 ID is 40.5mm, OD is 41.6mm.

 

[mh9162013]

A member recently PM'ed me this info:



BT-50 ID is 24.1mm, OD is 24.8mm.

BT-55 ID is 32.6mm, OD is 33.7mm.

BT-60 ID is 40.5mm, OD is 41.6mm.

Amazing information; thank you!

 

[bad_idea]

A member recently PM'ed me this info:

To elaborate, that Giant Leap retainer is their 29mm. Good fit for BT60 as you note.

Edit:

To elaborate more, I measure the OD of the retainer flanges that slip over the motor tubes as:

Rocketarium 18mm: 21.2mm

Rocketarium 24mm: 28.0mm

Giant Leap 29mm: I don't have a recorded measurement, but Giant Leap's Slimline Qwik-Lok knobs are nearly exactly as wide as the flanges of the retainers. I wish they made 18 and 24mm retainers along the same lines.