Estes 18mm motor mount - what were they thinking?

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paul.nortness

paul.nortness

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I have got a few standard engine based rockets in the last year that have a thin walled blue paper tube for the motor mount.

This tube is the most useless POS parts in the entire history of useless POS parts. Each time I have flown a rocket with this blue tube mount, after the second or third flight, the motor and hook begins to travel about a half inch. Of the three I have had this problem on, two of them have big rips in them...no doubt caused by the kick of the ejection charge pushing the motor down against the hook....the third one was scorched badly just below the thrust block and burnt through giving a large hole for the end of the hook to slide through.

I now have a box with about 10 Semroc BT-20J tubes in it just in case I get a kit with this crappy blue motor tube.

Granted, Estes customer service rules all and has replaced the rocket on all three occasions....but why even include such a craptastic part in the first place?

Anyone else had problems with this crappy blue tubed motor mount?
 
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paul.nortness said:
I have got a few standard engine based rockets in the last year that have a thin walled blue paper tube for the motor mount.

This tube is the most useless POS parts in the entire history of useless POS parts. Each time I have flown a rocket with this blue tube mount, after the second or third flight, the motor and hook begins to travel about a half inch. Of the three I have had this problem on, two of them have big rips in them...no doubt caused by the kick of the ejection charge pushing the motor down against the hook....the third one was scorched badly just below the thrust block and burnt through giving a large hole for the end of the hook to slide through.

I now have a box with about 10 Semroc BT-20J tubes in it just in case I get a kit with this crappy blue motor tube.

Granted, Estes customer service rules all and has replaced the rocket on all three occasions....but why even include such a craptastic part in the first place?

Anyone else had problems with this crappy blue tubed motor mount?
Click to expand...
Paul,

I think the blame lies with the nuclear ejection charges as much as it does with the weak tubes.

That said, there are some things you can do to toughen them up a bit. Put a ring of CA inside the aft opening, then sand that smooth. This will help keep the end from getting fuzzy after repeated insertions/extractions.

Use a motor block ahead of the forward tang on the hook.

Beef up the band anchoring the center of the hook. A wrap of light glass cloth (~3/4" wide) secured with epoxy helps.

When you insert the motor, add a wrap of tape to help seal the motor in the tube and to provide some light friction fitting.

Apply a wrap of tape to the hook to secure it to the motor. This will help keep the motor from sliding fore and aft - it will keep the motor, at ejection, from slamming backwards against the hook.

Those are some of the things I do generally, regardless of tube type, but they should be especially helpful with the flimsier blue tubes.

Doug

.
 
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I do not build many Estes rockets, but I had the same experience once.
Now I just replace it with other 18mm MMT tubing I use for scratch builds.

Also glueing the forward half of the engine hook helps distribute the forces.
 
I've never had a problem with the blue tube itself, but the lack of a thrust ring in most cases causes the hook to slide forward in my experience. Now I add a thrust ring to all of those engine mounts. Never had them rip a hole backwards, but most of my rockets don't see more than 5 flights.
 
Estes motor mount tubes used to be normal body tubes with the glassine coating. They got rid of the coating to make then easier to glue (it soaks in better). That made them weaker.

Solution:
1) Tell them directly. Only THEY can change the parts in their kits.

2) Reinforce and use thrust rings as already posted.
 
Estes has the blue thin walled motor mount tubes, Quest has the thin yellow motor mount tubes. Both are garbage! The yellow Quest tubes were meant to be an interior sleeve for the 25mm metric body tubes.

I usually do what you are talking about, switching them out to standard BT-20 tubes. Or better yet, the stronger ST-7 tubes.
The ST-7 tubes (older Centuri style) are a slightly larger diameter and won't fit the Estes centering rings without trimming.

Most of the Dr. Zooch kits have you glue a 110 lb. cardstock band right behind the slit for the engine hook. The reinforcement band is 1/2" wide X 2 3/8" long. That's enough to really beef up a BT-20 right below the upper bend of the engine hook. It's the protection needed for shotgun ejection charges.

I do agree, those kit supplied engine mount tubes are sub par and don't even go in my models. They go in the trash.
 
The last mount kits I bought was the standard estes sets. That blue tube was the least of my problems. One of the 2050 rings I had to notch for the motor hook, as I did it split appart having to glue it back together. Then the motor hook I layed it over a spent case and had a 3/16" extra gap. 1/16" more and I could install it over the motor block. Looking at the instructions it didn't say to do that.
 
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Haven't seen the problem, yet, but I have several that have not flown yet, too.

I have a few pieces of bt-20 that I got as part of a parts lot, will watch for the blue tubes and replace them with bt20 as I build.

Thanks for the warning!!
 
I've run into the tearing problem on more than just Estes motor tubes. I think the whole motor hook through the tube system is flawed. Backing the hook with a motor block is great for standing up to the motor thrust but does nothing to protect against the ejection charge ripping it the other way. In my opinion motor hooks have always been a weak spot in rocket kits.

I recently saw a Z hook on another thread and this seems to me to be the answer to the motor hook question. With no slot in the tube for the hook to rip out the Z hook would give positive motor retention without the inherent flaw in the system. Still there are some applications where the Z hook isn't ideal like minimum diameter boost glider pods.
 
I use a thrust ring on all my motor mounts, I don't think I've ever seen an Estes kit without one. I have the forward tang of the hook butted up right against the inside edge of the ring and then hold the hook in place with either several wraps of masking tape or if a mylar ring is included that. I also add a thin layer of CA to the ends of all tubes, not just motor mounts. It's definitely not poor construction that causes the failure.

I would be inclined to agree with plano-doug regarding the ejection charge if it happened on any other tube besides the blue tubes. I have flown engines from the same pack in different models and only the blue ones come down with motor mount damage.

Plain and simple it's just poor quality in the part. I have just finished composing an email to Estes to see if it can be addressed in future kits.
 
I always glue a thrust ring on top of the motor hook.

I always use a "strap" -- either a sleeve of BT-20 glued over the motor hook, or if I'm feeling lazy, a couple wraps of masking tape -- to secure the hook to the exterior of the motor mount tube.

Thus, neither the force of the motor's propellant burn or the jolt of the ejection charge is focused entirely on that tiny little 1/8" slit cut into the motor mount tube. It's distributed across several structural parts as it's imparted to the airframe of the model at large.

That said, I'd like it if they just used BT-20 for the motor mount tubes.
 
There was many estes kits that I built in the 90's without the thrust ring in the kit. At least most kits now have that.

In my case I had to cut a notch in the thrust block before glueing it in. I wanted the hook tight enough that the ejection charge would not slam the hook and tear it back. With the block glued down the motor isn't going forward. A bit of JB weld to fill the gap in the ring and bond the top of the hook in place, and stick the hook to the outside of the tube. The top of the hook is between where the thrust ring would be. And the hook is tight with the motor case solid against the thrust ring. This keeps the slide hammer issue under control. Another option would be to rebend the hook to fit the motor case.
 
paul.nortness said:
I have got a few standard engine based rockets in the last year that have a thin walled blue paper tube for the motor mount.

This tube is the most useless POS parts in the entire history of useless POS parts. Each time I have flown a rocket with this blue tube mount, after the second or third flight, the motor and hook begins to travel about a half inch. Of the three I have had this problem on, two of them have big rips in them...no doubt caused by the kick of the ejection charge pushing the motor down against the hook....the third one was scorched badly just below the thrust block and burnt through giving a large hole for the end of the hook to slide through.

I now have a box with about 10 Semroc BT-20J tubes in it just in case I get a kit with this crappy blue motor tube.

Granted, Estes customer service rules all and has replaced the rocket on all three occasions....but why even include such a craptastic part in the first place?

Anyone else had problems with this crappy blue tubed motor mount?
Click to expand...

Its called the bottom line...their kits are MADE IN CHINA...what do you expect a real rocket kit?
 
Aksrockets said:
I don't know I think the Mean Machine couplers would give it a run for it's money.

Alex
Click to expand...

OK....I concede. The couplers on the MM are pretty useless. I mean seriously....you have a 6 foot rocket and you can only afford to give us 1 inch couplers?
 
I have to agree about general disappointment. I haven't built many Estes kits in several years. I am currently building a scratch BT-50 based Darkstar clone and picked up the Estes 18mm motor mount kit. It had parts to achieve two objectives I had: an 18mm MM for the Darkstar and a 18/24 adapter that I could use in some of my other projects. For the $5 i paid for it at the LHS, it appeared to be an ok deal for convenience.

The blue tube was noticeably weaker when notching it than standard BT-20. Also, the instructions called for the "centering rings" to be cut to accommodate the hook. I don't like hooks in general but overall was just disappointed with the kit. I really wish there was a decent inexpensive solution for retention on 13 and 18mm projects that didn't involve a hook. From now on I will just drop the $12 on Rocketarium retainers for anything that I care about and use standard bulk BT-20.
 
paul.nortness said:
I have got a few standard engine based rockets in the last year that have a thin walled blue paper tube for the motor mount.

This tube is the most useless POS parts in the entire history of useless POS parts. Each time I have flown a rocket with this blue tube mount, after the second or third flight, the motor and hook begins to travel about a half inch. Of the three I have had this problem on, two of them have big rips in them...no doubt caused by the kick of the ejection charge pushing the motor down against the hook....the third one was scorched badly just below the thrust block and burnt through giving a large hole for the end of the hook to slide through.

I now have a box with about 10 Semroc BT-20J tubes in it just in case I get a kit with this crappy blue motor tube.

Granted, Estes customer service rules all and has replaced the rocket on all three occasions....but why even include such a craptastic part in the first place?

Anyone else had problems with this crappy blue tubed motor mount?
Click to expand...

The blue engine tubes have been in Estes kits for twenty years. I think they were an attempt to have some sort of color code construction standard and they also tried to get away with having cheaper tubes (no glassine outer wrap). I don't know if there's a rhyme or reason which kits get the blue tubes and which get normal tubes, but I bet it's something like, the cheaper the kit, the bluer the engine tube.
 
JStarStar said:
I always glue a thrust ring on top of the motor hook.

I always use a "strap" -- either a sleeve of BT-20 glued over the motor hook, or if I'm feeling lazy, a couple wraps of masking tape -- to secure the hook to the exterior of the motor mount tube.
Click to expand...

I've done this on my past few builds, but also I put epoxy between the engine hook and the motor mount tube. I measure the tube and cut a slot where the end of the hook goes, then I mark a line on the tube where the bottom of the wrap will be. I put a little epoxy on the tube and put the hook on top of it, then a thin strip of blue painters masking tape to hold the engine hook in place temporarily. After the epoxy hardens I take the blue tape off and glue on my final wrap and glue in an engine block. Now I'm confident that the engine hook can't go forwards, backwards, or peel off of the motor mount tube.
 
This is interesting. So far 3 of my 10+ flight rockets with the estes 18mm mounts have not demonstrated this flaw, and the others have so few flights on them that they are still tight as heck.
 
Many new kit parts are crap. The new laser cut CR's are junk.

Made in china kits do not impress. Wonder if Estes will comment here as In other threads. I understand needing to make a profit, but make it work.
 
Worsaer said:
Really? I assume you're just trying to be funny.
It doesn't really matter where it's made, if it's made to spec.
Click to expand...

OK let me rephrase it. They are just junk.

I hope that makes it clear. They use poor quality materials and cheap labor to keep the costs down, but the quality of the kit is reduced.
 
DizWolf said:
Many new kit parts are crap. The new laser cut CR's are junk.

Made in china kits do not impress. Wonder if Estes will comment here as In other threads. I understand needing to make a profit, but make it work.
Click to expand...

How much profit do they need to make? They are getting dirt cheap labor, and what are the raw materials involved? Some paper, some flimsy, warped balsa, some plastic and some rubber. Sometimes I love estes, sometimes I hate em'. I love them when they had great customer service and when they make kits like the cosmic explorer. I hate them when they sell one inch couplers with a 6 foot rocket and when the body tubes crimp when even looked at.

Alex
 
The Zooch kit method is the best I've seen to beef up ANY motor tubes...

A wrap (white glue and cardstock strip about a half inch wide) wrapped around the motor tube just below where the hook is "slitted" through the tube to prevent the ejection charge from blowing the motor back and forcing the hook to rip the tube. This can be done on ANY rocket just by cutting a strip of typing paper a half inch wide and long enough to go around the tube at least twice overlapping itself. Coat one side with white glue thinly and roll it onto the motor tube.

A drop of CA to harden the paper tube itself where the motor hook penetrates the tube at the top end.

A thrust block glued against the top of the hook. For a free lifetime supply grab a razor saw and start cutting 1/4 inch long pieces off the ends of old expended motor casings.

I quit using tape and switched to a long strip of printer paper about 1/2 inch wide coated with a thin layer of white glue and wrapped around the motor tube OVER the motor hook where I would normally use tape. Guaranteed permanent (as permanent as the rocket anyway).

Works like a champ! OL JR :)
 
Aksrockets said:
How much profit do they need to make? They are getting dirt cheap labor, and what are the raw materials involved? Some paper, some flimsy, warped balsa, some plastic and some rubber. Sometimes I love estes, sometimes I hate em'. I love them when they had great customer service and when they make kits like the cosmic explorer. I hate them when they sell one inch couplers with a 6 foot rocket and when the body tubes crimp when even looked at.

Alex
Click to expand...

From all reports, Estes customer service is still very good.

The Mean Machine coupler indeed sucks -- I ordered a 34" length of BT-60 coupler from BMS a couple years ago for $5 bucks or something, I figure it should last for a couple years unless I go absolutely crazy building monstrous BT-60 rockets. :eek:

So when I built my MM, I cut a 4" length of coupler. That holds it pretty well.

As far as the 1" BT-60 coupler now left over from the MM kit, I'll use it to make a motor mount for something else.
 
This is how I deal with the problem. Yeah, this isn't the infamous "bloo-toob", but the effect is the same. Wrap with either heavy twine or nylon, and soak in CA, Titebond, or epoxy (lightest-to-heaviest).

m-mount2.JPG
 
luke strawwalker said:
The Zooch kit method is the best I've seen to beef up ANY motor tubes...

A wrap (white glue and cardstock strip about a half inch wide) wrapped around the motor tube just below where the hook is "slitted" through the tube to prevent the ejection charge from blowing the motor back and forcing the hook to rip the tube. This can be done on ANY rocket just by cutting a strip of typing paper a half inch wide and long enough to go around the tube at least twice overlapping itself. Coat one side with white glue thinly and roll it onto the motor tube.

A drop of CA to harden the paper tube itself where the motor hook penetrates the tube at the top end.

A thrust block glued against the top of the hook. For a free lifetime supply grab a razor saw and start cutting 1/4 inch long pieces off the ends of old expended motor casings.

I quit using tape and switched to a long strip of printer paper about 1/2 inch wide coated with a thin layer of white glue and wrapped around the motor tube OVER the motor hook where I would normally use tape. Guaranteed permanent (as permanent as the rocket anyway).

Works like a champ! OL JR :)
Click to expand...

Ditto! OL JR (and Dr. Zooch) have the best solutions right here!
 
Is epoxy known to be better suited than wood glue for applications that are exposed to hot ejection gases and/or the energy of the ejection charge?

I've been using wood glue on my thrust rings and engine hooks and centering rings, but I'm wondering if I ought to switch to epoxy to prolong the life of the engine mounts?
 

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