38mm motor retainer

[bill2654]

Heres an idea I came up with for an easy and inexpensive (less than $2)motor retainer. This works great on 38mm where you have at least 3/8" motor mount exposed. I made it from a 1-1/2" theaded PVC adapter. The one in the pic is for electrical applications but they are identical. I used a 1' abrasive wheel but a dremel will work also. Take out enough of the inside of the PVC adapter so it fits over your motor mount and then cut off 3/8" to 1/2" of the threads. JB weld the threads onto your motor mount. I used a 1-1/2 by 1-1/4" threaded nut on the end of the threads. Easy, fast, inexpensive and doesn't look half bad! Bill

 

[JDcluster]

If it is used for electrical use, it might be ABS plastic.


Just a little heads up.


JD

 

[troj]

Yep, 'tis indeed an inexpensive way to do it!

I've seen them used before, and they typically hold up to quite a few flights before they need to be replaced.

Just make sure to use a standoff so that the motor exhaust doesn't cook it on the pad.

-Kevin

 

[MontanaSoftware]

Hello: The image seems to show a metal retainer nut-cap screwed onto the PVC threads. Being metal would be much better than a PVC cap screwed on. What type of nut-cap is this, and where can it be found? Thanks!

 

[Bat-mite]

Keep in mind that this is a five-year-old thread. You might want to PM bill2654 in case he doesn't see this.

 

[McKailas Dad]

Hello: The image seems to show a metal retainer nut screwed onto the PVC threads. What type of nut is this, and where can it be found?

Thanks!

I -think- that is a nut they typically use with electrical conduit? Like hooking up wires into a circuit breaker, but I'm not positive.

 

[rharshberger]

Hello: The image seems to show a metal retainer nut screwed onto the PVC threads. What type of nut is this, and where can it be found?

Thanks!

That is actually the compression fitting from plumbing hardware, look under your sink and you are likely to find one there.
Something like this only modified. I have seen threads on them before. They can be metal or plastic.

https://m.homedepot.com/p/Everbilt-...-_-mobileweb_search_rr-2-_-NA-_-205154109-_-N

Editing on a phone sucks, basically the retainer is just a modified compression fitting from a sink p-trap.

 

[MontanaSoftware]

basically the retainer is just a modified compression fitting from a sink p-trap.

Yes! Thanks ... I knew that looked familiar. Here is a link: https://www.homedepot.com/p/C8031C/205153821

I've seen so many PVC nuts on motor retainers ... I'd feel a little more comfortable with a metal one, depending on the weight. Come to think of it, the weight could be reduced by grinding off the excess metal around the grip -- just don't take off too much, and it will still be stronger and more heat-resistant than PVC. I'd also grease the threads before screwing it on, to make for easier removal.

Thanks again to everyone who took the time to reply. This is a great forum. I should really try to hook up with more people. I'm in western Montana, and there are no clubs in my town. I've been doing rocketry with just me and my kids for a long time ... you can learn a lot from others.

 

[McKailas Dad]

Thanks again to everyone who took the time to reply. This is a great forum. I should really try to hook up with more people. I'm in western Montana, and there are no clubs in my town. I've been doing rocketry with just me and my kids for a long time ... you can learn a lot from others.

Yes, this is a great forum! A few little cat fights may break out here and there, but you'll have that. Old men+strong opinions=bickering lol

You may surprised what you find here, there may be someone near you that wonders the same thing, "who around here launches rockets?!"

I've met people through the forum, that ended up to be literally miles from my house! Start a post in the Watering hole asking about people from your area of Montana, you may just find out like I did!

 

[bill2654]

Hello: The image seems to show a metal retainer nut-cap screwed onto the PVC threads. Being metal would be much better than a PVC cap screwed on. What type of nut-cap is this, and where can it be found? Thanks!

The metal nut is a 1 1/2" x 1 1/4" slip nut. It's for connecting your 1 1/4" lavatory drain to an 1 1/2" drain opening. Found in any plumbing store.

 

[MontanaSoftware]

Thanks Bill. An awesome DIY retainer.

And thanks also to McKaila's Dad ... I'm "Christina's Dad." My daughter is 10 now. I also have a 5 year old son who's crazy about rockets.

 

[MontanaSoftware]

Hey ... I just wanted to update this thread ... I used this method to make a 24 mm retainer, and it works great. I used an ABS nut in the Lowes Electrical conduit section. (Home Depot doesn't have that nut). Unfortunately, I couldn't find a metal nut that size. I think the NPT thread sizes I used were 1". Took a lot of grinding to make the threads fit over the motor mount tube, but It turned out great.

 

[Handeman]

Hey ... I just wanted to update this thread ... I used this method to make a 24 mm retainer, and it works great. I used a pvc nut in the Lowes PVC Electrical conduit section. (Home Depot doesn't have that nut). Unfortunately, I couldn't find a metal nut that size. I think the PVC thread sizes I used were 1". Took a lot of grinding to make the threads fit over the motor mount tube, but It turned out great.

You might want to consider buying them premade from Estes, They are $8 and $9 for 24mm and 29mm. Probably more expensive than making your own, but a lot easier and a lot less time.
https://www.estesrockets.com/009750-estesr-24-mm-motor-retainer-set
https://www.estesrockets.com/002950-pro-series-ii-29mm-motor-retainers

 

[rharshberger]

You might want to consider buying them premade from Estes, They are $8 and $9 for 24mm and 29mm. Probably more expensive than making your own, but a lot easier and a lot less time.
https://www.estesrockets.com/009750-estesr-24-mm-motor-retainer-set
https://www.estesrockets.com/002950-pro-series-ii-29mm-motor-retainers

And those prices are for 2 retainers!

 

[MontanaSoftware]

You might want to consider buying them premade from Estes, They are $8 and $9 for 24mm and 29mm. Probably more expensive than making your own, but a lot easier and a lot less time.
https://www.estesrockets.com/009750-estesr-24-mm-motor-retainer-set
https://www.estesrockets.com/002950-pro-series-ii-29mm-motor-retainers

Those look like good retainers, and I've got nothing against people who would buy them, but I notice that they appear to be longer than my homemade version ... the plastic nuts I bought from Lowes are thinner, which allowed me to shorten the threaded section. This saves weight, and also rides the motor a little higher, which helps to move the CG a little closer to the nosecone for improved stability.

And for some reason, I've just always had a hard time resisting the lure of DIY -- even when it makes more sense to just buy the thing you need. Not really because of money ... it just feels satisfying to make things yourself. My 7-year-old son and I are building rockets completely from scratch now, and we're having a great time. We're enjoying the building process just as much as flying. And he's learning a lot about using tools and creatively solving problems. This kid is a born engineer. Not everything in life is available as a kit, and I want him to be able to make his own solutions to life's challenges.

And besides ... for only 1 hour of work, I saved $6.00!!!! LOL.

 

[swatkat]

You can print them in any size and they are lighter, cheaper and stronger. 24mm to 54mm shown here.

 

[markg]

You can print them in any size and they are lighter, cheaper and stronger. 24mm to 54mm shown here.

What material are you printing those from? Do you have a file you can share? I think I'd like to give this a try.

cheers - mark

 

[jnobels]

I print them from PLA or ABS... ABS is probably the better choice. they’re at least as durable as the Estes version, though a bit larger. I’ve launched a PLA 29mm version a dozen times. Still looks perfect. No deformation or charring.

If you know how to use OpenSCAD, I’ve done up a quasi-parametric retainer. I can post the STL files too but they would be specific to the OD of your motor tube...

https://github.com/barnstar/ParametricRocketComp/blob/master/RocketComponentLib.scad

There are some other goodies in that file and in that repo too.

 

[markg]

I've used OpenSCAD for designing centering rings and getting them laser cut. I grabbed your files and it looks relatively easy to use. I generated an outer motor retainer and was able to export it to STL and import that into Cura. I'll see about print a 38mm to try out.

Thanks!

cheers - mark

 

[Handeman]

Those look like good retainers, and I've got nothing against people who would buy them, but I notice that they appear to be longer than my homemade version ... the plastic nuts I bought from Lowes are thinner, which allowed me to shorten the threaded section. This saves weight, and also rides the motor a little higher, which helps to move the CG a little closer to the nosecone for improved stability.

And for some reason, I've just always had a hard time resisting the lure of DIY -- even when it makes more sense to just buy the thing you need. Not really because of money ... it just feels satisfying to make things yourself. My 7-year-old son and I are building rockets completely from scratch now, and we're having a great time. We're enjoying the building process just as much as flying. And he's learning a lot about using tools and creatively solving problems. This kid is a born engineer. Not everything in life is available as a kit, and I want him to be able to make his own solutions to life's challenges.

And besides ... for only 1 hour of work, I saved $6.00!!!! LOL.

Completely understand the DIY, I usually go that way myself. At least the first time. Usually once I've done it the DIY method, I tend to buy the parts the next time.

Good Luck and have fun with that young engineer!

 

[captbk]

Cool to see how this thread has evolved over the past 8 years since I started it. Cant wait to see it in another 8 yrs or so.

 

[Wallace]

I am a huge fan of modifying/re-purposing common items for my specific needs. Simply ordering and assembling everything seems like cheating at times, but there always seems to be a random occasion where I get lazy and just order parts I could have easily made. Vendors gotta eat too....