Uh oh.

[Dee55]

Think I might have a problem. Back in oct 2020 I started building the mini mean machine and just got the engine mount done. But as anyone can see from the pics the engine hook is kinda off, but the engine does fit snuggly and tight. So before I take it any further I want to get some advice, will she fly like this as long as the engine is in tight?

 

[cerving]

Bend the hook out slightly so it catches the motor, then use a few wraps of masking tape around the hook to keep it from falling back. Been there, done that.

 

[waltr]

Yep, what Cris said.

 

[BABAR]

Bend the hook out slightly so it catches the motor, then use a few wraps of masking tape around the hook to keep it from falling back. Been there, done that.

yep, I've had engine hooks fail. Adding some tape is an effective "belt and suspenders approach."

 

[mh9162013]

Question: why can't the OP just sand down the ends of the motor casing just a smidge? I understand it's something you'll have to do before every flight for that rocket, but so is adding tape.

Or maybe it's an NAR code violation or something?

 

[BABAR]

Question: why can't the OP just sand down the ends of the motor casing just a smidge? I understand it's something you'll have to do before every flight for that rocket, but so is adding tape.

Or maybe it's an NAR code violation or something?

part 1. Sanding down the casing would by a NAR violation. I absolutely agree it would be an extremely minimal one, but it would be one. I don't do much club flying, so I can't say whether an RSO would have heartburn with it or not.

 

[David_Stack]

Since the motor hook is a pre-established length with bends front and rear to match the motor casing length, what is keeping the motor from moving forward in the motor mount tube to the extent that it butts up against the forward bend in the motor hook?

I'd be inclined to check for glue 'boogers' or similar obstructions up inside the motor mount tube which are preventing the motor from going further forward...

 

[DigBaddy]

Being a Mini Mean Machine, leave the motor mount out of it. Glue in an engine block at the right depth for 18mm motors and friction fit 18mm motors or (13mm with adapter) in it. More versatile rocket that way and it'll fly really nice on Bs and Cs

 

[neil_w]

Since the motor hook is a pre-established length with bends front and rear to match the motor casing length, what is keeping the motor from moving forward in the motor mount tube to the extent that it butts up against the forward bend in the motor hook?

I'd be inclined to check for glue 'boogers' or similar obstructions up inside the motor mount tube which are preventing the motor from going further forward...

I agree with this. Excess glue in the tube is the most likely reason for this.

If you can't clear the glue, then I would think it's straightforward to straighten out and then re-bend the hook to the correct length, using some pliers. Just do it carefully and get it right on the first try; repeated bending will weaken the metal (and eventually break it). But I think it would survive a single rebending just fine.

And then if *that* doesn't work, then just build a new motor mount for it. It's easy and the parts to build one cost very little. Or do what @DigBaddy suggests and take the opportunity to convert it to 18mm.

 

[lakeroadster]

No worries.

As @cerving suggested, just wrap a piece of tape around the motor / engine hook prior to launch. That will pull the motor hook snug against the motor.

A zip tie would also work....

 

[Back_at_it]

To answer the question, I would remove the motor clip altogether and simply friction fit the motor if I wanted to stick with 13mm motors.

The mini mean machine flies great on 18mm motors so I would take DigBaddy's suggestion and leave the 13mm mount out and simply use a motor block at the appropriate depth (2.5 inches) for an 18mm motor. This is how I built mine. I fly it on B6-6 motors more than any other motor and have sent it up on C6-7's a couple of times. This is one of those that really should have been 18mm from the start.

Due to the length of the rocket, having the larger motor will not effect stability. Also having the motor hanging out further than normal will not hurt anything.

 

[mtnmanak]

Another option - Cut the engine hook off, friction fit the motor till it is snug and then wrap a bit of masking tape around the exposed part of the motor and motor mount tube. I haven't installed an engine hook on an LPR in at least a decade and haven't had a motor fall out yet.

Edit: Ninja'ed by @Back_at_it

 

[Dee55]

Another option - Cut the engine hook off, friction fit the motor till it is snug and then wrap a bit of masking tape around the exposed part of the motor and motor mount tube. I haven't installed an engine hook on an LPR in at least a decade and haven't had a motor fall out yet.

Edit: Ninja'ed by @Back_at_it

Thanks

 

[BigMacDaddy]

If it is not glue snots it's possible that the top slot / insert of the hook is not tight against the top of engine block. If that is case I would just extend slot back to block so that hook is in correct place. Then maybe wrap some tape over the hole / extended slot.

If it is glue snots, I have found a small flat file can help me scrape things inside a tube till they are square / unobsructed.

 

[brockrwood]

Bend the hook out slightly so it catches the motor, then use a few wraps of masking tape around the hook to keep it from falling back. Been there, done that.

When in doubt about an engine hook’s ability to hold the engine in place, I just wrap masking tape around the engine and motor mount tube where the engine sticks out. It is amazingly effective.

 

[BigMacDaddy]

By the way -- the Mini Mean Machine also makes a great two stage rocket -- definitely do the main stage with an 18mm mount. It is a bit underpowered on a A10-0. Made mine after a hard lading crimped the body tube just above the fins...

 

[brockrwood]

Another option - Cut the engine hook off, friction fit the motor till it is snug and then wrap a bit of masking tape around the exposed part of the motor and motor mount tube. I haven't installed an engine hook on an LPR in at least a decade and haven't had a motor fall out yet.

Edit: Ninja'ed by @Back_at_it

If you use the masking tape around the exposed engine and the motor mount tube, do you even need to friction fit the engine with more tape? It seems like the engine’s own thrust would hold it in during the thrust phase. The tape just needs to resist the ejection charge’s force trying to kick the engine out of the motor mount, right?

 

[mtnmanak]

If you use the masking tape around the exposed engine and the motor mount tube, do you even need to friction fit the engine with more tape? It seems like the engine’s own thrust would hold it in during the thrust phase. The tape just needs to resist the ejection charge’s force trying to kick the engine out of the motor mount, right?

Absolutely, you can just get by with some masking tape. I use that method quite often. If the motor is loose in the tube, though, it is just a bit more piece of mind to wrap a piece of scotch tape around the motor to snug it up a bit. If it is already snug, then just use the masking tape. There are a number of Estes models that do not have hooks and they tell you to tape in the motors. The MIRV (2134) kit is a good example.

Sometimes the hook is just a pain and it isn't very "clean" looking. I like the simplicity and effectiveness of masking tape.

 

[brockrwood]

Absolutely, you can just get by with some masking tape. I use that method quite often. If the motor is loose in the tube, though, it is just a bit more piece of mind to wrap a piece of scotch tape around the motor to snug it up a bit. If it is already snug, then just use the masking tape. There are a number of Estes models that do not have hooks and they tell you to tape in the motors. The MIRV (2134) kit is a good example.

Sometimes the hook is just a pain and it isn't very "clean" looking. I like the simplicity and effectiveness of masking tape.

Wasn’t there once a model rocket in the olden days, the 60’s maybe, that was designed to let the ejection charge kick the engine out of the mount? Then the balance of the rocket changed and it became a glider. I could swear I remember seeing such a craft.

I would think that letting the rocket eject a smoking and still hot engine and letting that engine fall to the ground is frowned upon now.

 

[BABAR]

When in doubt about an engine hook’s ability to hold the engine in place, I just wrap masking tape around the engine and motor mount tube where the engine sticks out. It is amazingly effective.

View attachment 522276

If you do this, wise to put a cellophane or Mylar tape wrap around the tube, preferable wrapped the opposite direction you will put the final tape wrap on. This will keep the later tape wraps from pulling paint off or even worse delamination of the underlying tube when you remove a used motor and tape.

 

[mtnmanak]

Wasn’t there once a model rocket in the olden days, the 60’s maybe, that was designed to let the ejection charge kick the engine out of the mount? Then the balance of the rocket changed and it became a glider. I could swear I remember seeing such a craft.

I would think that letting the rocket eject a smoking and still hot engine and letting that engine fall to the ground is frowned upon now.

I don't remember one that kicked out only the motor (then again, my memory is highly suspect!!), but lots of gliders kick out the whole motor tube, which is usually barely bigger than the motor itself.

Probably my favorite rocket of the 70's & 80's (after the Der Red Max rockets) was the Estes Soaring Eagle. Loved those rockets and built a number of them. They kicked the whole booster section out and it was supposed to come down on a streamer. At least half the flights I did, the streamer fell off and the booster fluttered to the ground without incident.