Using a spent D engine case to hold a C engine

[OG1959]

I had an idea to use a spent D engine case to adapt a C engine into a D motor mount. I checked and a C engine fits inside a D case perfectly! Of course I would have to thoroughly clean out the D case and glue in a stop ring but I think it would work provided the weight of the rocket could be launched with a A B or C motor.

Has anyone ever done this with success?

 

[neil_w]

Yes, works fine. I think I've only used it in my 24mm Quinstar.

That said, I'm a big fan of the Estes red plastic adapters, which are cheap, lightweight and work beautifully.

 

[Scott_650]

As Neil said it works fine - I’ve done it in a pinch when I couldn’t find an adapter - but it is a messy job getting all the burnt propellant and charred clay out of the 24mm casing. The Estes #2317 18/24 adapters are easier to use and fairly inexpensive at $6 list price for three adapters.

My one tip on building a used engine case adapter is to use epoxy on the thrust ring - it’s tough to get them clean enough for white/wood glue. Or just shorten the 24mm case slightly and do a tape thrust ring on the aft end of the 18mm motor - glue isn’t a worry then!

 

[JPalmer621]

I have used many spent C and D motors for creating paint sticks. Works great. Also have glued a D21 (composite motor) into a spent D motor. Only issue i see is stopping the 18mm from blowing through the 24 mm casing

 

[kuririn]

For BP motors:
A 13 mm motor will fit inside a spent 18mm motor casing.
An 18 mm motor will fit inside a spent 24 mm motor casing.
A 24mm motor will not fit inside a spent 29 mm motor casing unless you either peel a few layers of paper on the 24mm motor or ream out the 29mm casing.
Of course the residue must be cleaned out and the clay nozzle knocked out.

 

[BABAR]

Works great. A bit heavier than the Estes plastic ones, and relatively easy to make your own, also lighter than a motor casing.

 

[OG1959]

I suppose I could just 3D print one from ABS as well. I could include the thrust ring in the print. There's probably one already on Thingiverse.

 

[jimzcatz]

For BP motors:
A 13 mm motor will fit inside a spent 18mm motor casing.
An 18 mm motor will fit inside a spent 24 mm motor casing.
A 24mm motor will not fit inside a spent 29 mm motor casing unless you either peel a few layers of paper on the 24mm motor or ream out the 29mm casing.
Of course the residue must be cleaned out and the clay nozzle knocked out.

Not all of that is true. I leave the clay nozzle in for a motor block. Just expand the nozzle to let ejection pass

 

[brockrwood]

Yes, works fine. I think I've only used it in my 24mm Quinstar.

That said, I'm a big fan of the Estes red plastic adapters, which are cheap, lightweight and work beautifully.

The Estes 18mm to 13mm red plastic adapters work fine for me. I have not tried the 24mm to 18mm adapters.
I have considered using a spent D motor to mount a C motor in a fairly light rocket but was worried about the extra weight the spent D would add to the rear of the rocket. Has anyone tried it?

 

[neil_w]

The Estes 18mm to 13mm red plastic adapters work fine for me. I have not tried the 24mm to 18mm adapters.

They are the same thing, just bigger. I've also gotten good use out of the 29mm/24mm adapters.

I have considered using a spent D motor to mount a C motor in a fairly light rocket but was worried about the extra weight the spent D would add to the rear of the rocket. Has anyone tried it?

It's gonna depend on the rocket.

However, I wouldn't think a spent D with a C inside will weigh more than a fresh D, will it? The more important question would likely be whether the C has enough thrust for the rocket.

 

[brockrwood]

Works great. A bit heavier than the Estes plastic ones, and relatively easy to make your own, also lighter than a motor casing.

Seems like it should be fairly easy to make your own 24mm to 18mm motor mount adapter as long as you have the correct tubes and centering rings lying about. You’d need about 3 inches of BT-20 tube and some centering rings to make it slide into the 24mm (BT-50) motor mount. You’d need a short slice of a spent 18mm engine to use as an engine block.

 

[brockrwood]

However, I wouldn't think a spent D with a C inside will weigh more than a fresh D, will it?

Excellent point.

 

[brockrwood]

I leave the clay nozzle in for a motor block. Just expand the nozzle to let ejection pass

Cool idea!

 

[brockrwood]

The Estes #2317 18/24 adapters are easier to use and fairly inexpensive at $6 list price for three adapters.

My problem is that as soon as I place an order with an on-line vendor of rocket parts (you know, the ususal suspects), and of course I order enough stuff that the shipping cost is not a big comcern, I remember that one other thing I wanted. Such as Estes 24mm to 18mm adapters. Now the shipping cost IS a concern, so I have think of enough extra stuff to buy to negate the shipping cost for a second order. Ad infinitum. Sigh.

 

[BABAR]

Seems like it should be fairly easy to make your own 24mm to 18mm motor mount adapter as long as you have the correct tubes and centering rings lying about. You’d need about 3 inches of BT-20 tube and some centering rings to make it slide into the 24mm (BT-50) motor mount. You’d need a short slice of a spent 18mm engine to use as an engine block.

You may want to add an engine hook

 

[Scott_650]

My problem is that as soon as I place an order with an on-line vendor of rocket parts (you know, the ususal suspects), and of course I order enough stuff that the shipping cost is not a big comcern, I remember that one other thing I wanted. Such as Estes 24mm to 18mm adapters. Now the shipping cost IS a concern, so I have think of enough extra stuff to buy to negate the shipping cost for a second order. Ad infinitum. Sigh.

Flightsketch is a solid vendor with very reasonable shipping rates - under $35 is $3 - over that shipping is included. Their Mini Bluetooth altimeter is very nice and very small - might be worth the wait for it to come back in stock for your next order

 

[bjphoenix]

I have to be careful- this brings all kinds of crazy thoughts to mind... I already have a homemade 38mm-29mm adapter, and a 29mm-24mm adapter. So I could make a 24mm-18mm adapter and put a B motor in my 4" Binder Excel.

But seriously- I found a 3-pack of D12-7 in my stuff so I had to build a rocket to use them- a HiFlier XL. If it survives 3 launches to high altitude then I could launch it on a C6.

 

[neil_w]

My problem is that as soon as I place an order with an on-line vendor of rocket parts (you know, the ususal suspects), and of course I order enough stuff that the shipping cost is not a big comcern, I remember that one other thing I wanted. Such as Estes 24mm to 18mm adapters. Now the shipping cost IS a concern, so I have think of enough extra stuff to buy to negate the shipping cost for a second order. Ad infinitum. Sigh.

Sorry, where’s the problem exactly?

 

[jimzcatz]

You may want to add an engine hook

No hooks

 

[lakeroadster]

It's a long, long road
From which there is no return
While we're on the way to there
Why not share?
And the load of that old motor casing.
Doesn't weigh me down at all

 

[BABAR]

No hooks

Yeah, I guess that wouldn’t work with a casing alone, unless you peeled out the inside layer and inserted a BT-20 or whatever size you are downsizing too. If use hooks on my home made adapters. I make may own centering rings with masking tape, I take a roll and a sharp blade and 3/4“ tape, cut around and around and around to get three 1/4 inch thick lengths (you don’t need to cut all the way to the core at the start, just a few leyers. Wrap the 1/4 tape around until you get the diameter you want. and Bob‘s your uncle!

 

[bwayne64]

I suppose I could just 3D print one from ABS as well. I could include the thrust ring in the print. There's probably one already on Thingiverse.

https://www.thingiverse.com/thing:1963241
Is this the one you mentioned ? Thought I'd link it for the lazy people...... Like me,
; )

Joe

 

[brockrwood]

You may want to add an engine hook

I just friction fit the engine with a little to premasking tape. It takes a little extra time but then I can dispense with engine hook.

No hooks

I have mixed emotions about engine hooks. If they are easy to include in the motor mount and don’t get in the way, I include them. If they are in the way or add unnecessary complexity to the rocket build, I omit them. I have several rockets where I just friction fit the engine with masking tape. No biggie. Just takes an extra minute or two to prep the rocket for launch. I do keep a pair of needle nose pliers in the range box to get the spent engine out after flight.

 

[brockrwood]

and Bob‘s your uncle!

Going to have to Google the meaning of this phrase! “And Bob’s your uncle”?

 

[bwayne64]

My favorite Uncle Bob ; )

 

[BABAR]

. I do keep a pair of needle nose pliers in the range box to get the spent engine out after flight.

Can’t speak for HPR, but for LPR i find pulling the motor out soon after the flight has two advantages.

paradoxically it seem easier to pull then when it cools (you’d think it would be the other way around, but that hasn’t been my experience.)

also, I immediately put the motor casing an a plastic bag, if not a sealable one, at least one I can wind a few times and get a near seal. I store everything in the trunk of my car, and a found if I left the motors in the rocket in the trunk on the way home, somehow the odors would waft into the cockpit of the car.

the saying, “I love the smell of BP in the morning” sounds good to rocketry fans, but I find it fails the reality test personally.

 

[bjphoenix]

also, I immediately put the motor casing an a plastic bag, if not a sealable one, at least one I can wind a few times and get a near seal. I store everything in the trunk of my car, and a found if I left the motors in the rocket in the trunk on the way home, somehow the odors would waft into the cockpit of the car.

I drive my Jeep Wrangler out to the launch site so a plastic bag is the only defense I have. That doesn't help with smell from the rockets themselves, I may start taking a large trashbag for them.

I've got a few new kits to build that have 24mm mounts but most of the time I would prefer to launch them on a B or C for my small field. I was thinking about making a few of the adapters out of D12 casings. I assume that means friction fitting the 18mm motor, or making a special motor hook.

I wonder if it would be acceptable to glue an 18mm motor inside of a D12 casing for single use? Maybe with the effort needed to clean out a D12 casing I wouldn't want it to be single use. I was thinking I could cut a groove down the side of the D12 for the motor hook to fit into and another groove around the perimeter of the D12 for a ring to hold the motor hook. I have a strip of metal that came out of an old windshield wiper blade that I could make a motor hook out of, it would need longer hooks to reach the 18mm motor.

Or I could just get a piece of BT-20 and a standard motor hook, make some centering rings from rolled paper, and use that. It would probably be lighter overall than the D12 casing.

Currently I have the Estes HiFlier XL that I've launched with D12-7. It flies great with no wind but goes high enough that you need a day with no wind and a large field, on the small field that we sometimes use I prefer that size rocket on a B or maybe a C. I have another HiFlier XL kit that I'm bashing into another design and I would prefer to launch it on B or C also. I could use C11 but it is so much easier to buy C6 for cheap at the local Hobby Lobby.

 

[Scott_650]

I drive my Jeep Wrangler out to the launch site so a plastic bag is the only defense I have. That doesn't help with smell from the rockets themselves, I may start taking a large trashbag for them.

I've got a few new kits to build that have 24mm mounts but most of the time I would prefer to launch them on a B or C for my small field. I was thinking about making a few of the adapters out of D12 casings. I assume that means friction fitting the 18mm motor, or making a special motor hook.

I wonder if it would be acceptable to glue an 18mm motor inside of a D12 casing for single use? Maybe with the effort needed to clean out a D12 casing I wouldn't want it to be single use. I was thinking I could cut a groove down the side of the D12 for the motor hook to fit into and another groove around the perimeter of the D12 for a ring to hold the motor hook. I have a strip of metal that came out of an old windshield wiper blade that I could make a motor hook out of, it would need longer hooks to reach the 18mm motor.

Or I could just get a piece of BT-20 and a standard motor hook, make some centering rings from rolled paper, and use that. It would probably be lighter overall than the D12 casing.

Currently I have the Estes HiFlier XL that I've launched with D12-7. It flies great with no wind but goes high enough that you need a day with no wind and a large field, on the small field that we sometimes use I prefer that size rocket on a B or maybe a C. I have another HiFlier XL kit that I'm bashing into another design and I would prefer to launch it on B or C also. I could use C11 but it is so much easier to buy C6 for cheap at the local Hobby Lobby.

As already mentioned earlier the Estes #2317 18/24 adapters are easier to use than spent cases and fairly inexpensive at $6 list price for three adapters.

 

[BABAR]

As already mentioned earlier the Estes #2317 18/24 adapters are easier to use than spent cases and fairly inexpensive at $6 list price for three adapters.

Also much lower weight penalty. Going DOWN a motor size potentially means less velocity off the rod or rail. With a light adapter, may not lose much as you drop some mass compared to a larger motor, and you shift CG forward. The 24mm motor casings are I believe a good bit heavier than the Estes adapters, so you are ADDING mass in the worst possible place.

the adapters also act as built in motor blocks.

 

[Raco123]

Great Idea