Shorty Motor

[UMRS]

Got some old kits that need the ole shorty. I was thinking it would be easier to just cut the ends of the A8-3s off on a tube cutter, rather than try to cut them by hand.

Any thoughts of a prefered method to cut them?

And for all you safety nazis out there we know its not supposed to happen.

[Shreadvector]

Why not simply glue or tape a mini motor into a 1.75 inch long segment of used/spent motor casing. Perfectly legal and actually nearly identical to the design of the original Shorty motors. Estes mini motors fit inside the Quest casings perfectly. Much tighter fit inside the modern Estes 18mm motors.

[Doug Sams]

Got some old kits that need the ole shorty. I was thinking it would be easier to just cut the ends of the A8-3s off on a tube cutter, rather than try to cut them by hand.

Any thoughts of a prefered method to cut them?
I'd be afraid a tubing cutter will distort the case and result in debonding the grain. IOW, bang!

I use Fred's method a lot. I do occasionally saw off an 18mm motor, too. I use a wrap of paper to mark a line about 0.05" long (ie, @ 1.8"), then cut it with a razor saw. When sawing boosters, I stuff some wadding into the forward end just in case a spark comes off the saw.

Once the motor is cut, it's usually a little uneven, so I sand it square with a sanding block, using the extra 0.05" to get everything evened up without cutting it short.

Motors suitable for sawing include the A8-3, A8-5, B6-0 and 1/2A6-2. Can't recall about the other B motors, but I think some of them have enough space (1"), too.

Doug

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[Bazookadale]

A fine tooth x-acto razor saw should work. But as a 40 year safety Nazi I prefer Shreadvector's idea

[Bob Kaplow]

Another vote for the Shread Vector method of making "Shortie" motors that comply with the NAR safety code.

Back in the old days (before most of you were born) I dorked a razor saw trying to cut the casing on a B4-2 to make a shorty B. I wouldn't recommend it at all.

if they'd ever toss the "old motor test program: and reinstate safety certification of the old motors instead, I still have a pretty good stash of "S" motors, still sealed in blue tubes.

Which reminds me of the punch line to an old joke:

"Did you see that "S" car go?"

[UMRS]

Why not simply glue or tape a mini motor into a 1.75 inch long segment of used/spent motor casing. Perfectly legal and actually nearly identical to the design of the original Shorty motors. Estes mini motors fit inside the Quest casings perfectly. Much tighter fit inside the modern Estes 18mm motors.


good idea, thats what I like.

Problem

Solution :)

[mojo1986]

I have used a tube cutter to make 18 mm shorties for my old Estes Birdie on numerous occasions. Don't try to do the whole cut with the tube cutter, though. Doug is correct that the pressure you need with the tube cutter to go all the way through will distort the casing and probably crack the grain. Just go around 3 or 4 times with the tube cutter to form a good groove. Then place the engine on a hard flat surface and use the groove as a channel for a sharp knife (I use a kitchen knife). Roll the engine back and forth repeatedly with light pressure. You will get a nice clean cut without disturbing the propellant grain.

Joe

[gpoehlein]

You could always use a Dremel with some nice, sparky brushes! :p

(Ducks thrown objects)

Greg

[tbzep]

I've used X-Acto saws with no problems. I roll the motor as I cut through to the inside. It won't pinch and bend if you are only cutting at one point on the saw. If you cut all the way across without rolling, you have two cutting points on the saw, plus you are more prone to pinching as you get deeper. Both can cause you to bend the saw blade if you aren't careful. I haven't bent a blade since I was about 12. I still have that blade and my son uses it to cut balsa. It was very weak to begin with.

[Mark II]

Any thoughts of a prefered method to cut them?
Hatchet. :D

Or heavy cleaver. :D

Mark \\. (diving into the nearest foxhole)

[Mark II]

[...]
Motors suitable for sawing include the A8-3, A8-5, B6-0 and 1/2A6-2. Can't recall about the other B motors, but I think some of them have enough space (1"), too.

Doug

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That would give you something that Estes itself never offered: a shorty B motor! :)

Personally, I'd like to see a shorty E motor: 1.75" long, 38mm in diameter! :p :chuckle:

Mark \\.

[Doug Sams]

That would give you something that Estes itself never offered: a shorty B motor! :) They offer it - they just don't know it :D

I've flown a K-40 on a B6-0S to A8-5S. You need extra eyes for that one :)

Doug

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[Mark II]

They offer it - they just don't know it :D

I've flown a K-40 on a B6-0S to A8-5S. You need extra eyes for that one :)

Doug

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Uhhh...yeahhh! ;)

Bust the waiver with it? :chuckle:

Mark \\.

[ghrocketman]

I am the POLAR OPPOSITE of a safety-nazi and would use whatever method you feel works best as long as you don't plan on flying at a sanctioned event. I fly on my own private land so the entire "certified" business is a moot point.

[UMRS]

Yeah my brother in law has 40 acres in northern MI, that we fly the interesting stuff at ;)