29mm motor - actual outer diameter?

[spudman]

Hi folks. I have a bit of a technical question. I recently assembled a rocket kit that I bought nearly 30 years ago. Yes...life sort of "got in the way" of relaxing and taking the time to get back into my childhood passion of building & flying model rockets! Anyway, the kit was the North Coast Rocketry "Patriot" #3512. This was from the era when North Coast Rocketry was apparently run/owned by Estes. Anyway, back when I bought the kit, I also bought two North Coast Rocketry motors. They are F62-4 (29mm) motors, which the kit instructions recommended. Yesterday, when I was nearing completion of my build, I attempted to slide the motor into the motor mount tube and to me anyway...it felt rather tight. It was going in, but I knew if I continued pushing it in further, it would take a pliers or vise-grip at the very least to get it out. I used a digital caliper to measure the outer diameter of the motor and found it to be 28.6mm. Knowing that I'd prefer not to use the motors that I bought 30 years ago (although they were stored indoors and might very well be just fine yet), I began looking for a new motor online. I came across the Aerotech Economax 29mm F67-4W at Apogee Rockets and figured this would work well for my rocket. There was no actual outer diameter of the motor listed on the website (obviously, it was listed as a 29mm motor), so I called Apogee to see if they could help. While the gentleman I spoke with didn't have that exact dimension either, he did say that a 29mm motor is designed to fit inside a 29mm motor mount tube, which totally makes sense to me. And therein lies my problem. I stumbled across an old review of this Patriot kit from NCR where the reviewer mentions that he wishes that NCR or Estes had included a slightly larger motor mount tube...because the motors seemed to fit overly tight. Too late for me now of course, as the entire motor mount assembly is epoxied into the main body tube. So here's my question; does anyone have the Aerotech F67-4W motor (or any Aerotech 29mm motor) that they could measure with a caliper for me in order to give me an exact outer diameter? I'm thinking I'm going to be OK with ordering them, but I guess I'd just like to be sure before-hand. Thanks in advance for any help you can offer!

 

[SolarYellow]

Should be 1.125 OD. F67 uses this case:

https://www.rocketmotorparts.com/29_X_83mm_Molded_Casing/p1577809_18373070.aspx

 

[pugachu]

The old north coast rockets had slightly undersized motor mounts. You may be able to open it up carefully with a flapper wheel sander. All Aerotech casings are 1.125" in the OD. Both reloadable (metal) and single use.

If you don't feel comfortable opening up the inner diameter of the motor tube with an abrasive, you will be stuck with 24mm diameter motors, and use an adapter. This will limit your available selection to high thrust 'E' class motors (unless you buy a somewhat expensive reloadable casing)

 

[tfish]

Hi folks. I have a bit of a technical question. I recently assembled a rocket kit that I bought nearly 30 years ago. Yes...life sort of "got in the way" of relaxing and taking the time to get back into my childhood passion of building & flying model rockets! Anyway, the kit was the North Coast Rocketry "Patriot" #3512. This was from the era when North Coast Rocketry was apparently run/owned by Estes. Anyway, back when I bought the kit, I also bought two North Coast Rocketry motors. They are F62-4 (29mm) motors, which the kit instructions recommended. Yesterday, when I was nearing completion of my build, I attempted to slide the motor into the motor mount tube and to me anyway...it felt rather tight. It was going in, but I knew if I continued pushing it in further, it would take a pliers or vise-grip at the very least to get it out. I used a digital caliper to measure the outer diameter of the motor and found it to be 28.6mm. Knowing that I'd prefer not to use the motors that I bought 30 years ago (although they were stored indoors and might very well be just fine yet), I began looking for a new motor online. I came across the Aerotech Economax 29mm F67-4W at Apogee Rockets and figured this would work well for my rocket. There was no actual outer diameter of the motor listed on the website (obviously, it was listed as a 29mm motor), so I called Apogee to see if they could help. While the gentleman I spoke with didn't have that exact dimension either, he did say that a 29mm motor is designed to fit inside a 29mm motor mount tube, which totally makes sense to me. And therein lies my problem. I stumbled across an old review of this Patriot kit from NCR where the reviewer mentions that he wishes that NCR or Estes had included a slightly larger motor mount tube...because the motors seemed to fit overly tight. Too late for me now of course, as the entire motor mount assembly is epoxied into the main body tube. So here's my question; does anyone have the Aerotech F67-4W motor (or any Aerotech 29mm motor) that they could measure with a caliper for me in order to give me an exact outer diameter? I'm thinking I'm going to be OK with ordering them, but I guess I'd just like to be sure before-hand. Thanks in advance for any help you can offer!

Those kits came with <29mm motor mounts..IIRC..my son sanded the ID to get reall 29mm motors to fit..

25 years ago..

Tony

 

[pugachu]

That's the AJ I remember.... with the crazy Estes fat boy on the I435...

 

[SolarYellow]

There are a variety of single-use, 24mm F motors from Quest and AeroTech (same company, different case technologies).

With a rocket that big and heavy, you'll probably want to sand the MMT ID.

 

[OzHybrid]

By specifying motor sizes as the metricised version of the imperial size they are, it allows you to easily differentiate motor mount tubes from body tubes. MM Tubes are specified in mm and are the ID of the tube which are an easy fit on the metricised motor body od size. Body tubes are specified generally in inches and are the OD of the tube size. Then there's the BT sizes...... And the exceptions. There are other threads here on the BT sizes....

 

[tfish]

That's the AJ I remember.... with the crazy Estes fat boy on the I435...

He's a tad older now..

Tony

 

[sghioto]

Can the outside of the those F62-4 motors be sanded to fit better?

 

[SolarYellow]

The motor case contains pressure. You'd have to sand every one, and sanding would make them "experimental," requiring an L2 certification. Sanding the MMT ID one time solves the problem for all motors ever used.

 

[sghioto]

How much difference would it really make to fit better?

 

[Art Upton]

Hi folks. I have a bit of a technical question. I recently assembled a rocket kit that I bought nearly 30 years ago. Yes...life sort of "got in the way" of relaxing and taking the time to get back into my childhood passion of building & flying model rockets! Anyway, the kit was the North Coast Rocketry "Patriot" #3512. This was from the era when North Coast Rocketry was apparently run/owned by Estes. Anyway, back when I bought the kit, I also bought two North Coast Rocketry motors. They are F62-4 (29mm) motors, which the kit instructions recommended. Yesterday, when I was nearing completion of my build, I attempted to slide the motor into the motor mount tube and to me anyway...it felt rather tight. It was going in, but I knew if I continued pushing it in further, it would take a pliers or vise-grip at the very least to get it out. I used a digital caliper to measure the outer diameter of the motor and found it to be 28.6mm. Knowing that I'd prefer not to use the motors that I bought 30 years ago (although they were stored indoors and might very well be just fine yet), I began looking for a new motor online. I came across the Aerotech Economax 29mm F67-4W at Apogee Rockets and figured this would work well for my rocket. There was no actual outer diameter of the motor listed on the website (obviously, it was listed as a 29mm motor), so I called Apogee to see if they could help. While the gentleman I spoke with didn't have that exact dimension either, he did say that a 29mm motor is designed to fit inside a 29mm motor mount tube, which totally makes sense to me. And therein lies my problem. I stumbled across an old review of this Patriot kit from NCR where the reviewer mentions that he wishes that NCR or Estes had included a slightly larger motor mount tube...because the motors seemed to fit overly tight. Too late for me now of course, as the entire motor mount assembly is epoxied into the main body tube. So here's my question; does anyone have the Aerotech F67-4W motor (or any Aerotech 29mm motor) that they could measure with a caliper for me in order to give me an exact outer diameter? I'm thinking I'm going to be OK with ordering them, but I guess I'd just like to be sure before-hand. Thanks in advance for any help you can offer!

Nobody said the quiet part out loud yet.

Estes under the management at the time, made the DarkStar motors just smaller then the Aerotech motors on purpose. They made the motor mount tube smaller on purpose. This was to make you buy their motors only. Many people were upset with this after finding out when trying to put an AT motor they had in the rocket after they built the kit.

There is on this site descriptions on how to "Peal" the inside of the motor mount tube to take a layer of the inside of the tube off so Aerotech motors will fit. I can't search for it right now but maybe I can in the morning.

Also, before Estes bought NCR, NCR sold Aerotech motors relabeled to NCR, and at that time non-Estes NCR kits used real 29mm motor tubes, not the 28.5mm motor tubes.

Do your Motors say "DarkStar" on them? If so they should fit.

Here is an old post about 'sanding': https://www.rocketryforum.com/threads/north-coast-rocketry.93796/#post-1041008
But I would go with sanding or pealing the inside of the motor tube.

 

[lr64]

Can the outside of the those F62-4 motors be sanded to fit better?

That would let him use those 2 motors. Any other single use motor would probably have to be sanded to fit as well. Or the mount could just be sanded once. Seems like very little material* would have to be removed to make the motors fit. Maybe even just put those two motors someplace really dry for a while if they have paper cases.

*1.125" is 28.58 mm

 

[Art Upton]

Maybe even just put those two motors someplace really dry for a while if they have paper cases.

The motors do not have paper cases

@spudman , Do your F62's say Estes on them like this one of mine?

Also here is a nearby to you [Neenah, Wisconsin] rocketry store: https://www.siriusrocketry.biz/ishop/aerotech-economax-f67-4w-29mm-single-use-motor-2-pack-1884.html

 

[KenECoyote]

Anyone ever tried lube? (Seriously.)

Also try a dowel wrapped in sandpaper and you can remove the sticker on the single use motors.

 

[sr205347d]

Hi folks. I have a bit of a technical question. I recently assembled a rocket kit that I bought nearly 30 years ago. Yes...life sort of "got in the way" of relaxing and taking the time to get back into my childhood passion of building & flying model rockets! Anyway, the kit was the North Coast Rocketry "Patriot" #3512. This was from the era when North Coast Rocketry was apparently run/owned by Estes. Anyway, back when I bought the kit, I also bought two North Coast Rocketry motors. They are F62-4 (29mm) motors, which the kit instructions recommended. Yesterday, when I was nearing completion of my build, I attempted to slide the motor into the motor mount tube and to me anyway...it felt rather tight. It was going in, but I knew if I continued pushing it in further, it would take a pliers or vise-grip at the very least to get it out. I used a digital caliper to measure the outer diameter of the motor and found it to be 28.6mm. Knowing that I'd prefer not to use the motors that I bought 30 years ago (although they were stored indoors and might very well be just fine yet), I began looking for a new motor online. I came across the Aerotech Economax 29mm F67-4W at Apogee Rockets and figured this would work well for my rocket. There was no actual outer diameter of the motor listed on the website (obviously, it was listed as a 29mm motor), so I called Apogee to see if they could help. While the gentleman I spoke with didn't have that exact dimension either, he did say that a 29mm motor is designed to fit inside a 29mm motor mount tube, which totally makes sense to me. And therein lies my problem. I stumbled across an old review of this Patriot kit from NCR where the reviewer mentions that he wishes that NCR or Estes had included a slightly larger motor mount tube...because the motors seemed to fit overly tight. Too late for me now of course, as the entire motor mount assembly is epoxied into the main body tube. So here's my question; does anyone have the Aerotech F67-4W motor (or any Aerotech 29mm motor) that they could measure with a caliper for me in order to give me an exact outer diameter? I'm thinking I'm going to be OK with ordering them, but I guess I'd just like to be sure before-hand. Thanks in advance for any help you can offer!

I bought a Phantom 4000 recently, and discovered the problem. I also discovered that the Estes F15 will fit. However, the F15 doesn’t have enough thrust. So I added 24 mm motor pods for E12 boosters.

Thread 'Black Powder High Power'
https://www.rocketryforum.com/threads/black-powder-high-power.185762/

 

[DJRNY]

does anyone have the Aerotech F67-4W motor (or any Aerotech 29mm motor) that they could measure with a caliper for me in order to give me an exact outer diameter?

I don't have an F67-4w but I measured a few randomly selected Aerotech 29 mm motors and got the following (English measurement converted to metric):
F67-6W - 28.55mm
F42-4T - 28.65mm
G80-7T - 28.78mm
G74-6W - 28.58mm
Hope this helps.

 

[rcktnut]

I have the Big Brute, and the Dark Star motors slide in without problems. Other single use motors (Aerotech) did not fit but the Aerotech 29/40-120 case- Dr. Rocket 29mm. HPR cases fit as good as the Dark Star motors. I'm thinking that over time your MMT may have swollen due to humidity if you are having problems with fitting the motors that are supposed to fit in the first place.
Sanding the MMT should do the trick.
BTW this is an NCR by ESTES kit. Took a pic.

 

[spudman]

The motors do not have paper cases

@spudman , Do your F62's say Estes on them like this one of mine?

Also here is a nearby to you [Neenah, Wisconsin] rocketry store: https://www.siriusrocketry.biz/ishop/aerotech-economax-f67-4w-29mm-single-use-motor-2-pack-1884.html

View attachment 653921

Yes, Art Upton...my F62 motors do have the Estes logo on them. Looks like I'll be doing a bit of sanding to the inside of the motor mount tube if I end up using the Aerotech motors. Thanks for the info!

 

[spudman]

I don't have an F67-4w but I measured a few randomly selected Aerotech 29 mm motors and got the following (English measurement converted to metric):
F67-6W - 28.55mm
F42-4T - 28.65mm
G80-7T - 28.78mm
G74-6W - 28.58mm
Hope this helps.

Thank you VERY much! I appreciate the info; looks like I may have to do a bit of sanding on the inside of the motor mount tube.

 

[spudman]

Thank you VERY much to everyone for all of the information and suggestions! I really appreciate it. Looks like I have a slight amount of sanding to do.

 

[OzHybrid]

Thank you VERY much to everyone for all of the information and suggestions! I really appreciate it. Looks like I have a slight amount of sanding to do.

Or replace the motor mount tube with a proper one.

 

[spudman]

Or replace the motor mount tube with a proper one.

Kind of hard to do when the current one is epoxied to three centering rings and those rings are epoxied in place inside of the main air-frame tube.

 

[OzHybrid]

Kind of hard to do when the current one is epoxied to three centering rings and those rings are epoxied in place inside of the main air-frame tube.

The only difficult part is making the decision. If I were doing it, I'd 3D print some guides for a small dia boring bar rig. You only have to replace the section the motor goes in, not the full tube.
But go with the sanding option first. As it's easier. You have to remove a small amount. But it takes longer than you think to evenly remove a small amount by sanding.
If sanding fails you still have options.

 

[lr64]

Maybe use a small cylinder hone? Not especially cheap, though. I wonder if they make abrasive reamers? Maybe glue a flap of sandpaper to a rod and put the rod in a drill, and sand with that. That might tend to be even, though I don't know if it would necessarily be centered.

 

[lakeroadster]

Looks like I have a slight amount of sanding to do.

Might be worth making a sanding fixture out of a wooden dowel, glue some sandpaper to that dowel, and chuck it in a drill. Viola!​

​

Edit.... Ah man.. @lr64 beat me to the punch. ​

​

​

 

[Art Upton]

Maybe use a small cylinder hone? Not especially cheap, though. I wonder if they make abrasive reamers? Maybe glue a flap of sandpaper to a rod and put the rod in a drill, and sand with that. That might tend to be even, though I don't know if it would necessarily be centered.

There is a Wooden dowel at craft, hobby, and even hardware stores that have the large "Dowel Display" rack. One of them its perfect inside 29mm reload cases to push the insides out after using. I used to get mine at Michaels crafts.

Wrap that in about 220 or 320 sandpaper and sand away by hand easy checking very often. You don't need a drill to do this. A drill will likely get you in trouble.

 

[spudman]

Maybe use a small cylinder hone? Not especially cheap, though. I wonder if they make abrasive reamers? Maybe glue a flap of sandpaper to a rod and put the rod in a drill, and sand with that. That might tend to be even, though I don't know if it would necessarily be centered.

This was exactly what I thought of after others suggested the sanding option. I have a good friend who is a machinist (and motorcycle fanatic like myself) who has quite a selection of cylinder hones. He actually just showed me this collection a few months back when we were rebuilding a brake caliper on a vintage bike. I think either the honing method or maybe even machining a few thousandths off the outer diameter of the motor casing (possibly less safe?) will be the way to go.

 

[spudman]

There is a Wooden dowel at craft, hobby, and even hardware stores that have the large "Dowel Display" rack. One of them its perfect inside 29mm reload cases to push the insides out after using. I used to get mine at Michaels crafts.

Wrap that in about 220 or 320 sandpaper and sand away by hand easy checking very often. You don't need a drill to do this. A drill will likely get you in trouble.

Thanks! That's a great idea as well!

 

[Art Upton]

Thanks! That's a great idea as well!

It's thinking it is the 3/4" one they sell at home depot even. You need room for the sand paper.

I misplaced my set of "motor pokin' tools" which we called these Dowels when I traded my truck in for another in 2018. 'Cause if you get a motor stuck in the motor mount tube you need a motor pokin' tool to push it out from the other end; using a rubber mallet gently.