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accooper

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I, being a Dark Lord Of The Scratch Builders, love to make most of my own rocket parts, like centering rings, stage couplers, engine hooks, and the like.

I really appreciate all of you giving me ideas, and I have been using old wind shield wiper blades to make my engine hooks from.

But being the father of an all knowing freshman, and a room mate, my son brought up the idea that not making the engine hook correctly could hamper engine performance. To be truthful I never really thought about it.

So, my son and his room mate did a little experiment. They said that if the motor hook protruded too far it would obstruct the gases being release from the engine nozzle there by reducing the performance of the engine.

They used two different engine hooks(I don't have the actual ones, but copies of them). One an Estes made hook, and one of my design that is patent pending.

They found that using an Estes type hook you could lose about 150 feet altitude with the 24mm D, 130 - 180 with the 18mm A,B, or C, and on an Estes T size A10, between 80 - 90 feet.

In picture 1 you can see my hook design just barely goes past the engine casing on a 24mm D engine, and an 18mm C (although, the hook on the C could be just a smidgeon smaller.

In picture 2 this is a perfect fit on the 24mm D.

Andrew
Dark Lord Of The Scratch Builders

1.JPG


2.JPG
 
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accooper

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Here are some more pictures of the proper engine hook fit. An engine hook does not need to go much past the cardboard casing, since that is the support structure.

I hope these pictures are easier to tell what I am trying to say.

Andrew
Dark Lord Of The Scratch Builders

3.JPG


4.JPG
 

accooper

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As you can tell in this picture, the Estes Style hook protrudes and covers up almost half of the engine nozzle opening, retarding gas flow.

This really hurt the Estes A10-3T engines altitude capabilities.

Andrew
Dark Lord Of The Scratch Builders

5.JPG
 

accooper

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Here are pictures of my home made hooks and an Estes style hook for T engines. The top image is a 24mm hook made from wider wiper blade stock, the middle image is made from normal width. The bottom an Estes hook.

My son and his room mate flew three 24mm flights (2 D's and a fat C), three 18mm fights (an A, a B, and a C), and two T engine flights both A10-3T.

I hope this will help some of y'all.

Andrew
Dark Lord Of The Scratch Builder

6.JPG


7.JPG
 
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accooper

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By The way, although Estes says you can use an engine hook on their E engine, I do not recommend it. My son's room mate's dad used one and the power of the engine broke the top hook of the engine hook and the motor travelled up through the rocket body. Not doing the rocket any good.

Andrew
Dark Lord Of The Scratch Builders.
 

MarkII

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I always use Semroc's engine hooks in my scratch-builds; they are similar to the old Estes hooks of yore, with no finger tab. Their hooks are both less filling AND they taste great! The finger tab on the style of hook that Estes currently uses may make the act of pulling the hook out of the way marginally easier (and maybe it doesn't), but that spurious benefit is not worth one bit of the extra hassle that the design causes. I never had any difficulty retracting the hook in my old Estes rockets in the 1960's, and I have never had any problem with doing so with Semroc's or anyone else's hooks, either. (That classic style of engine hook is used by most other rocket companies.) It is simple and effective and it never gets in the way.

MarkII
 

MarkII

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By The way, although Estes says you can use an engine hook on their E engine, I do not recommend it. My son's room mate's dad used one and the power of the engine broke the top hook of the engine hook and the motor travelled up through the rocket body. Not doing the rocket any good.

Andrew
Dark Lord Of The Scratch Builders.
I use the longer style of engine hook all the time with D12 and E9 engines, and I have never seen them fail. I always block the upper end of the hook with a thrust ring, but I do that with all of my mounts that are built for black powder engines. There has been some discussion recently of also blocking the upper hook just below it, too (which would require that the builder custom-make a longer hook, but that isn't hard to do). But I have never had a hook rip rearward through the motor tube, either. (If you use a good quality tube and anchor the hook well, you basically eliminate this problem.) I don't use engine hooks with composite motors, though. For them I use either friction, a restraining plate or ring or some variation of the trusty Kaplow clip (attached with machine screws that thread into the mount like Bob designed them, rather than being bolted onto a threaded rod that projects out of the mount).

MarkII
 

gpoehlein

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As I noted in another thread, I just use a hobby file to score the Estes hook and snap off the excess. Takes a couple minutes at most and is easy enough to do.
 

Handeman

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I use the longer style of engine hook all the time with D12 and E9 engines, and I have never seen them fail. I always block the upper end of the hook with a thrust ring, but I do that with all of my mounts that are built for black powder engines. There has been some discussion recently of also blocking the upper hook just below it, too (which would require that the builder custom-make a longer hook, but that isn't hard to do). But I have never had a hook rip rearward through the motor tube, either. (If you use a good quality tube and anchor the hook well, you basically eliminate this problem.) I don't use engine hooks with composite motors, though. For them I use either friction, a restraining plate or ring or some variation of the trusty Kaplow clip (attached with machine screws that thread into the mount like Bob designed them, rather than being bolted onto a threaded rod that projects out of the mount).

MarkII
Actually, the engine hook on the 24/40 composite motors works quite well. You have to file down the forward part so the forward end cap will fit, but the hook works great. I little wire to make sure it can't open up makes the retention great.

Be very careful though, my Stormcaster went into orbit on a F24W. It went up and never came down. Had to be in orbit, right? :rolleyes:

 

Micromeister

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Andrew:
I make my own motor hooks as well, I've never understood why Estes and other manufactures added the "finger saver" extension to their motor hooks. They are simply unnecessary in every way. When I get them I simply use a pair of side cutters to clip off the excess and file the end. When making my own the are usually .080" x 1/8" spring steel heat bent and oil quenched or stainless whiper blade inserts.
Just get rid of the overhangs they'll be just fine;)
 

shreadvector

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Estes changed the hooks by demand. It was either a survey of random customers or massive input from Educational customers. The old style clips/hooks were hard for some users to deflect to remove or install the motor.

They did not go with the original MPC type clip/hook because if anyone (like a child $$$$$) should reach out to catch the rocket while it is descending and get hit in the palm of the hand with the hook tip, they will suffer a puncture wound. Did I mention $$$$$$$$$ ?

That is why the new style Quest clips/hooks have a small flat return bend on the bottom end.

The new style hooks are only a problem on the 13mm motors, where they extend into the exhaust and deflect the thrust and created vectored thrust which will easily make a Gnome type model fly unstable.

As a result, they have been in our club's "Safety Advisory" for years.

And for the record, when I make my own from windsheild wiper inserts, I make them the old style.

http://home.earthlink.net/~mebowitz/safety.pdf
 

jadebox

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I've seen several cases where the Estes-style hooks have caught on the blast deflector, stand-off, or launch controller leads which is another reason to use the simpler design.

--Roger
 

Swampworks

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By The way, although Estes says you can use an engine hook on their E engine, I do not recommend it. My son's room mate's dad used one and the power of the engine broke the top hook of the engine hook and the motor travelled up through the rocket body. Not doing the rocket any good.

Andrew
Dark Lord Of The Scratch Builders.

I have always used an engine hook on my Estes powered rockets and never seen them fail due to thrust, which is the failure described above. I'm not disputing that something happened and the motor travelled up the tube, but if I am not mistaken, the E9 is a fairly low thrust (comparatively speaking) motor. I would be curious as to whether this failed hook was a "factory hook" or a scratch-built.
 

accooper

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I have seen them fail. If they are too much into the path of the escaping gases of the engine nozzle they burn off, and If the ejection charge is too powerful they break.

Seen them both on home-made and Estes made.

Andrew
Dark Lord Of The Scratch Builders
 

MarkII

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I have seen them fail. If they are too much into the path of the escaping gases of the engine nozzle they burn off, and If the ejection charge is too powerful they break.

Seen them both on home-made and Estes made.

Andrew
Dark Lord Of The Scratch Builders
In 10 years of flying rockets, I have never experienced, nor have I ever seen anyone experience a broken engine hook due to either one of those causes, or any other. Classic-style engine hooks do not get blasted by the exhaust jet. Yes, I can see how it might be possible with finger-tab style hooks, but in the three rockets in my fleet that have them, this has never been a problem. Classic style clips are simple, effective and durable.

Last year, for the first time ever, I began finding that some of my rockets were kicking their black powder motors, even though in all three instances of this, the recovery system had deployed normally. I started wrapping some 1/8" wide masking tape around the aft end of the hook and around the motor when I prepped my rockets so that the end of the hook couldn't get deflected by the kickback from an unusually strong ejection charge. I had no further problems with ejected motors, and this is now part of my standard prep routine. If this same phenomenon is what you are seeing, then I can understand, but it is not due to a broken hook, just one that is not rigid enough to retain the motor when it fires an extra strong ejection charge. A fix for it is simple: just give the hook and motor a couple of wraps of tape.

MarkII
 

accooper

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The guys I fly with now don't require any engine hook, but my church where I fly on my own does due to the fact that we have had the worst draught the past two years and they don't want any grass fires.

I have been using blue painters tape to wrap my engines in the rockets of mine that don't have an engine hook.

Haven't had any engines kick out on me yet.

Andrew
Dark Lord Of The Scratch Builders
 

luke strawwalker

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By The way, although Estes says you can use an engine hook on their E engine, I do not recommend it. My son's room mate's dad used one and the power of the engine broke the top hook of the engine hook and the motor travelled up through the rocket body. Not doing the rocket any good.

Andrew
Dark Lord Of The Scratch Builders.
On any "high thrust" or "heavy" rocket you want to use a thrust block in addition to the motor hook-- something to transfer the g forces of acceleration and thrust from the engine casing into the motor tube, centering rings, and on into the airframe. The tiny contact patch of the motor hook concentrates the forces and can lead to the sort of problems yall have encountered.

Thrust rings are cheap and easy to come by. Either order a mess of them from Semroc with your next order, or spring for a pack at the LHS next time your in there, but they kinda burn you pricewise. The simplest way to get them, though it requires a few minutes and some elbow grease, is to cut off the top 1/4 inch of an old expended motor casing using a razor saw. You can get handful of motor rings from a single engine casing, ready to glue in to the motor mount above the hook, for very little investment in time and effort and no money... (you should already have a razor saw or consider getting one at Hobby Lobby with a 40% off coupon-- they're VERY handy tools to have!)

Good luck! OL JR :)
 

luke strawwalker

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In 10 years of flying rockets, I have never experienced, nor have I ever seen anyone experience a broken engine hook due to either one of those causes, or any other. Classic-style engine hooks do not get blasted by the exhaust jet. Yes, I can see how it might be possible with finger-tab style hooks, but in the three rockets in my fleet that have them, this has never been a problem. Classic style clips are simple, effective and durable.

Last year, for the first time ever, I began finding that some of my rockets were kicking their black powder motors, even though in all three instances of this, the recovery system had deployed normally. I started wrapping some 1/8" wide masking tape around the aft end of the hook and around the motor when I prepped my rockets so that the end of the hook couldn't get deflected by the kickback from an unusually strong ejection charge. I had no further problems with ejected motors, and this is now part of my standard prep routine. If this same phenomenon is what you are seeing, then I can understand, but it is not due to a broken hook, just one that is not rigid enough to retain the motor when it fires an extra strong ejection charge. A fix for it is simple: just give the hook and motor a couple of wraps of tape.

MarkII
DItto! OL JR :)
 
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