Engines for my first 29mm Motor Rocket

I'm a little confused.

My Aerotech Airspike (Mustang w/o decals?) has a 29mm motor mount. I picked up the web special and received the rocket with two F20s. The F20's appear to fit correctly with the single 1" spacer that comes with the Airspike. The specs on the Econojets say these are 73 mm long but there are no dimensions of 73mm anywhere on the motor. The casing is 83mm.

My questions become these:

1) Should an F20 use either of the cardboard spacers in addition to the 1" spacer that comes with the kit?

2) Will a 29/40-120 RMS fit into a mount like this?

3) Are the F25 and F50 longer? Specs say they are 98mm long.

4) Any idea where the 73mm dimension came from?

Please let me know.

Thanks.

Reply to
Thomas Koszuta
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The Aerotech F20 is 29mm x 73mm. The F25 and F50 are 29mm x 98mm. The 29/40-120 RMS casing should fit just fine. Use whatever spacer or combination of spacers for the engine hook to engage properly on your Mustang.

Reply to
Bruce Sexton

Assuming you installed your engine block correctly (don't laugh, I didn't on one of my AT kits), you will need the one inch spacer, AND, the cardboard spacer that came with the pack of motors. When the motor is installed, the aft end of the hook should seat snugly into one of the slots on the nozzle end of the motor. As an added security measure, put a wrap or two of masking tape around the hook and motor. AT's motor clips are strong, but have been known to let a motor kick out on ejection.

David

Reply to
Dlogan

No. Use a masking tape thrust ring on the motor case. Report the anomoly to Aerotech so they can make new spacers for the new F20's. Tell them Jerry sent you.

Yes. The thrust ring will butt against the rear of the motor tube. Again I suggest tape anyway on the case right behind the thrust ring so the tape you Apply on the outside to retain the motor will stick better. It doesn't stick well to the closure, especially with any grease on it.

Aerotech is changing all of their motors this season, so the motors you find will vary for a year or so till all old stock is gone.

Also I expect other people's responses to vary from mine alot.

I fly rockets almost every day. And rockets are expendable :)

Jerry

Pardon the tech post!

Reply to
Jerry Irvine

Found the answer to the question while playing with my toy last night.

The hook fits very nicely right to the end of the nozzle if you do not put in the little cardboard spacer. In fact, it fits so well it looks correct - the hook even has the bend to get right to the end of the nozzle and lock. When I put the little spacer in it fits exacty as David says.

There still is no 73mm dimension on that F20, but Aerotech must have compensated by reducing the length of the cardboard spacer. As Jerry said, they are changing the motors and this one came right from their "Webstore" last month.

Thanks.

Reply to
Thomas Koszuta

Jerry,

You mean to wrap tape on the aft end of the engine to butt up against the engine tube? What is the advantage of that over the cardboard spacer?

Reply to
Thomas Koszuta

Yes.

ANY length motor may be used.

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Tech Jerry

Reply to
Jerry Irvine

I had this same conversation back when I started(Aerotech Arreaux), only I was you. Here's the advantage. Go burn five of those shorter motors, then try and take that spacer that the kit comes with back out. I got one stuck good. The trick to that is a piece of coat-hanger bent about 75-80, a little longer than the width of your motor tube diameter, so as you push it into the tube it will go in, but at the spacer when you try and pull it back out it will dig into it and pull it back out(Thanks Roy Potter of RoCC). This would be easier to show you, naturally.

Or you can wrap masking tape around the end of the motor and make a thick tape ring that will keep the motor from going up the tube, and put that spacer in your range box to rattle around in it for a few years before you recycle it into another project.

After you have to dig that spacer out once so you can fly bigger motors, you'll kick yourself and make the switch.

Best of luck, John G.

Reply to
JohnG

Myself, I kind of like the spacers. I don't like the mess I sometimes get with hot, sticky masking tape, or when I forget to take it off right away and it ends up being more 'permanent' than I'd like.

But, you've pointed out a good note about those spacers -- so here's what I might try. I'll take the spacer and drill through it, and then put a piece of rod (which would be better, brass or steel?) through it, and glue it on the inside of the spacer so that the diameter of the spacer isn't changed. Then, I can use your 'coathanger' idea to make a hook instead of a reverse-wedge, and simply put the hook around the rod in the spacer and pull it back out.

This might be overkill, but you only really need to do this to one spacer.

BTW, I'm having a heck of a time finding good old wire coathangers anymore. My wife gets those stupid plastic ones at the store that last a couple of months before breaking. I've got a stash of a few 'real' coathangers put away for use as 'tools', but don't see the 'real' ones around as much.

David Erbas-White

Reply to
David Erbas-White

Take some of your wife's clothes to the drycleaners, and they will inevitably come back on wire hangers of some sort. Of course, you're as likely as not to get those wire hangers with a cardboard stick as the cross-piece, which are useless for most wire-hanger-reuse projects, since they are actually 2 seperate pieces of wire when un-twisted.

Or, just leave 2 or more wire hangers in a dark hall closet for a month or two, and let them breed.

- Rick "Mommie Dearest" Dickinson

Reply to
Rick Dickinson

Pants and stuff that gets draped over the bottom rod get the cardboard hangers. Shirts and the like get the wire ones.

Bob Kaplow NAR # 18L TRA # "Impeach the TRA BoD" >>> To reply, remove the TRABoD!

Reply to
Bob Kaplow

David,

3 or 4 wraps of 1/4" masking tape to form a thrust ring will never, ever cause a "hot, sticky" mess.

You're assuming you're dealing with only two motor lengths. In 29mm rockets, you may well need to handle four lengths, with many more possible (but you're unlikely to fly F's thru I's in the same rocket). Even in 24mm, there are at least four lengths to deal with.

I've gotten to the point that I rarely install motor blocks in anything anymore.

Me, too. My problem seems to be that my do-gooder wife has to round up all my shirt hangers and take them back to the laundry when she drops off my shirts (so the laundry can shrink them and crack the buttons :(

Doug

Reply to
Doug Sams

a "hot, sticky" mess.

Oh, trust me, I've done it. Used cheap masking tape from the 99 cent store. Won't make that mistake again.

you may well need to handle four lengths, with many more possible (but you're unlikely to fly F's thru I's in the same rocket). Even in 24mm, there are at least four lengths to deal with.

I should have mentioned, I'm not currently doing HPR, just mid-power, so the Aerotech 24mm works fine with a one-inch spacer (for Estes E rockets), and the 29mm just has one spacer size needed (to the best of my knowledge) for the available mid-power rockets.

David Erbas-White

Reply to
David Erbas-White

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Good point.

Reply to
Jerry Irvine

Yes, you will need both spacers. It's been suggested that a wrap of tape will serve as a thrust ring and you can leave out the spacers. Don't, because the crust that forms inside the motor tube from the ejection charges will make getting your RMS hardware and G80s, etc. hard to get in and scratch up the anodize on the reloads. The spacers will protect the inside of the mount and your rocket will last longer.

Yes. Assuming you've built the mount correctly. Use a wire tie or wrap of tape around the hook/motor to prevent it kicking. I've seen it happen. Also, clean the wire mesh/baffle regularly and verify that it's clear by blowing through from the nose end. Motors will kick no matter what you do to keep them in if the baffle is obstructed.

Yes. Note that the new version of the F20 is a bit longer than the old version of the F20. The spacers provided take that into account (i.e. the newer spacers are shorter.)

See above!

For what it's worth, I call my Airspike the Mustang LCV (Low Cost Version). Doesn't come with decals, no 24mm adapter, and a published motor list that is Econojets exclusively. Mine's flown many times and survived at least two F20 CATOs. One at LDRS 22!

Later!

Reply to
Tim Burger

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