Replaced my Windshield Wipers - Time to Make Engine Hooks!

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tear those things apart and take another picture so that we can see what you end up with, and if you can get the right dimensions you need.
 
If you have a vice ( or extra hands available) they should bend better if you heat them (red hot) with a propane torch.
I've made a couple without heating in the past, just a 90 at both ends (like old school). Didn't trust them enough to use them.
 
If you have a vice ( or extra hands available) they should bend better if you heat them (red hot) with a propane torch.
I've made a couple without heating in the past, just a 90 at both ends (like old school). Didn't trust them enough to use them.

That will anneal them, unless you make sure to cool them at the correct rates to maintain the springiness. I'd have to read up to remember how to do all that and not make them overly brittle.

Also, vise. Unless you also hang out on garage/shop forums and have a habit of collecting too many of them, then vises can become a vice.
 
Wilton vises-You're Nobody unless you own a Wilton over on The Garage Journal (which I quit 5 years ago)

8-incher. 100+ lbs. of garage bad-assitude. Don't know what I'd do without it.

Also have a Panavise that has Long Beach, CA cast into it. And a German Ridgid XF50 Quick Acting swivel-base vise. And the 2.5-inch Wilton that's a total Chinesium POS. And a Wilton woodworking vise.

Yeah, I might have the vice.
 
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Who uses engine hooks anymore....I quit using them long ago and now just leave the motor mount a 1/2" long and use aluminum tape to retain motors of all sizes from13mm to 75mm (I haven't flown a 98mm yet).
 
Who uses engine hooks anymore....I quit using them long ago and now just leave the motor mount a 1/2" long and use aluminum tape to retain motors of all sizes from13mm to 75mm (I haven't flown a 98mm yet).
I do... Then again, I'm into the history of the hobby, and the history of kits.
 
I use my own screw on retainers unless it is a motor that doesn't use an ejection charge. If you want to make the springy things, take a hint from the lock pick crowd, walk a few neighborhood streets and pick up street sweeper brushes that have broken off. You will find lots of them. It is springy, tough, and just about the right width.
 
I have found some wiper spines don't like to be bent 90 degrees to make motor hooks....but I don't know which spines came from which brand of wipers, all I can say is "watch out for cracking".

And that's sage advice. The technique of how the hook is bent is the key to success.

What I've learned when making homemade motor hooks is to ensure there is a radius at the 90 degree bends. I typically use (2) pliers to bend the wiper spine, and not a vise and a hammer.

You only get one chance. If you bend the spine in the wrong location, you can't flatten it out and re-bend it. The forming process work hardens the material... it will indeed crack if over worked.

A nice fluid motion when bending the metal is the result when using pliers... as opposed to multiple blows with a hammer with the steel clamped in a vice.

Hook.JPG DSCF2043.JPG
 
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I thought the top 90 degree bend went into a slot in the tube? :questions:
The one I am showing is for a scratch build that used a AT composite motor (as shown). Composite motors have a much higher ejection force and can zipper the motor hook right out of a cardboard motor tube.

I've proved that theory.... :facepalm:
 
And that's sage advice. The technique of how the hook is bent is the key to success.

What I've learned when making homemade motor hooks is to ensure there is a radius at the 90 degree bends. I typically use (2) pliers to bend the wiper spine, and not a vise and a hammer.

You only get one chance. If you bend the spine in the wrong location, you can't flatten it out and re-bend it. The forming process work hardens the material... it will indeed crack if over worked.

A nice fluid motion when bending the metal is the result when using pliers... as opposed to multiple blows with a hammer with the steel clamped in a vice.

You can also clamp an aluminum block as a heat sink and spot anneal the bends leaving the long section springy(?), I used to use an old Radio Shack mini torch (two CO2 cylinder looking tanks) for that purpose and silver soldering gun sights.
 

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When I make my own, I make them long enough to go over the thrust ring, so the slot is on top of that reinforced part of the motor tube. Estes kits have the hook in a slot just under the thrust ring.
Proceed with caution and....
<<<------

That's sage advice GlenP is offering up! Relying on just the body tube to withstand the motor's ejection charge isn't sufficient for any motor bigger than, let's say.. an 18mm Estes BP C6... IMO.

And the narrower the clip the more likely it is to rip through the body tube.
 
The one I am showing is for a scratch build that used a AT composite motor (as shown). Composite motors have a much higher ejection force and can zipper the motor hook right out of a cardboard motor tube.

I've proved that theory.... :facepalm:
My homemade engine hooks will be used with Estes BP motors. Nothing more powerful than E black powder motor. Is the zipper issue still applicable? Definite don’t want zippered motor tubes!
 
My homemade engine hooks will be used with Estes BP motors. Nothing more powerful than E black powder motor. Is the zipper issue still applicable? Definite don’t want zippered motor tubes!

Sure, they'll work but the top end of the hook needs needs a centering ring or a motor thrust ring to bear against.

Motor Hooks.jpg
 
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When I make my own, I make them long enough to go over the thrust ring, so the slot is on top of that reinforced part of the motor tube. Estes kits have the hook in a slot just under the thrust ring.
Odd'l Rockets used to sell an extended engine hook like that.
Two benefits:
The forward motor thrust is distributed by the thrust ring rather than by the narrow area in front of the engine hook.
At ejection the rearward motion of the engine hook is stopped by the thrust ring.
I think the hook was 1/4" longer than standard.
 
I work in a garage and will be digging in the trashcans for a blade that has the metal spine. Not all do anymore. The cheaper ones are all plastic. I need to bend up one for a 13mm mini I'm getting reading to start.

I never saw that about the opposite bend for centering rings (post 23). Learned something new today.

Oh, but I also learned a bunch about BT-20 based rockets with 13mm motors

-Bob
 
Who uses engine hooks anymore....I quit using them long ago and now just leave the motor mount a 1/2" long and use aluminum tape to retain motors of all sizes from13mm to 75mm (I haven't flown a 98mm yet).
Does removing the aluminum tape damage the tube or do you reinforce the tube? Is aluminum tape the stuff they use on heating ducts?
 
Starting a couple of builds I thought I might have to make some engine hooks so I dug up the scraps I saved from sold old windshield wipers and took some measurements. I still have a few old Estes hooks so I could measure them also. For a control we'll use the Estes engine hook. Mine measured 0.125" wide x 0.025" thick.

One of the scraps I had measured 0.162" wide x 0.030" thick. Using the Estes as a control this one would be 1.9 times as strong and 2.2 times as stiff. Maybe this is of benefit for 24mm and maybe even 29mm motors. (Strength comparison is assuming the steels have equal yield strength. For a rectangular section the strength is a function of the square of the thickness but stiffness is a function of the cube of the thickness.)

The other scrap I had measured 0.100" wide x 0.030" thick and looks like the picture in post #20. Again using the Estes as a control this one would be 1.15 times as strong and 1.38 times as stiff. This is probably suitable for 18mm motors.

I read all of the previous comments to I went out in the garage and tried the bend test. I was able to easily bend both of my samples to less than 1/16" radius which is probably sufficient for rocketry use. Compared to the Estes it had a little bit less radius, hardly enough difference to tell. If you have studied engineering statics and strength of materials you would see that bending a rectangular cross section to a tight radius is very difficult. You have to apply the force very close to the point where you want the bend. I was doing this with 2 pair of needle-nose pliers. Someone mentioned the hammer and vise trick which mutilates the metal a bit but will get a tight radius. If you clamp a rectangular strip in a vise with say 1 inch sticking out and you pull at the end of the strip you will get deformation in a zone maybe 1/4" out from the vise, varying deformation, and you will end up with a radius close to the 1/4". Using a pair of needle nose pliers I was able to get the force applied about 1/8" or 3/16" from the point of bending. This is what bending theory says, I should have tested this while I was out in the garage but it is too hot out there today for leisurely work. I worked on some centering rings, cut a couple of LPR tubes, measured the strips of metal and that was about all I could stand.

I had the concern before about engine hooks slipping or tearing tubes. The hook at the end doesn't do anything to resist motor thrust because there is an engine block there too, and if you are using a composite motor you should have a thrust ring at the back end. The hook at the front can get in the way of some composite motors. I had the idea similar to LR in post #13 to bend the hook to the outside and put several layers of material over that end of the hook so there would be a lot more material to rip through. I usually have scraps of body tube that I could cut into maybe 1" lengths and slot so the could wrap over the hook and most of the way around the tube. I thought worst case I could use 3 layers and this would provide good tearing resistance. Also I normally cut off the excess shapes at the back end leaving just a short bend like the way engine hooks used to be. When my rockets land usually the engine hook is the first thing to contact ground and I don't want it being bent or loaded in a way contrary to how it is supposed to function. I've had them deform before upon landing.
 
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Does removing the aluminum tape damage the tube or do you reinforce the tube? Is aluminum tape the stuff they use on heating ducts?
I wrap the exposed motor tube with clear shipping tape, as soon as the paint is dry. This tape stays in place.

Then when you install the motor retention tape* it doesn't stick to, and tear off, the cardboard motor tube.

*No need to use aluminum tape. Just use regular old masking tape.
 
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