54mm Hardware Tail Cone

[Loki Research]

For quite some time now, I've been trying to work out a tail cone for use with 54mm 2800 and 4000 hardware using the single use nozzles. I need to pick a major diameter for the tail cone and I am leaning toward making it the same diameter of the motor case rather than most airframe tubing. I am thinking this because I would prefer these to be able to work for any type of setup where the hardware is used as a second stage. If it is the same as the motor case, the case can act as the interstage coupler. I thought I'd get some feedback just to make sure I'm not overlooking something.

For those who would purchase a tail cone for current and future reloads, which would you prefer the major OD match?
1) the motor case
2) the airframe

 

[mpitfield]

Scott the timing of this is impeccable, I was going to call you to discuss this very subject. I am all for a tailcone on those cases and personally would prefer it to match the O/D of the case not the air-frame.

 

[pondman]

For quite some time now, I've been trying to work out a tail cone for use with 54mm 2800 and 4000 hardware using the single use nozzles. I need to pick a major diameter for the tail cone and I am leaning toward making it the same diameter of the motor case rather than most airframe tubing. I am thinking this because I would prefer these to be able to work for any type of setup where the hardware is used as a second stage. If it is the same as the motor case, the case can act as the interstage coupler. I thought I'd get some feedback just to make sure I'm not overlooking something.

For those who would purchase a tail cone for current and future reloads, which would you prefer the major OD match?
1) the motor case
2) the airframe

Airframe please......

 

[A5tr0 An0n]

OD of the case. NOT the airframe.

 

[Onebadhawk]

One of each please,, lol...

Hey,,
There are different people doing different projects...
This is what the poll is showing...

Teddy

 

[Loki Research]

I might add here, if it was made to the motor case, you could always sand a taper into the back of the airframe in order to somewhat blend it into the tail cone without too much trouble. Conversely, it would require a machine lathe to turn down the tail cone in order to match the motor case. That would make a mess of the hardcoat finish.

Keep the votes coming though please.

 

[markkoelsch]

Scott, my thinking is that any way you do it somebody will not be happy. If you do it to the airframe which airframe- is it 54mm thick/standard, is it 54mm thin wall etc.

I would tend to lean towards the case for the above reason.


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[pondman]

Scott, my thinking is that any way you do it somebody will not be happy. If you do it to the airframe which airframe- is it 54mm thick/standard, is it 54mm thin wall etc.

I would tend to lean towards the case for the above reason.


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That is actually NOT a bad reason Mark. Either way I will adapt........

 

[OverTheTop]

What about having the main part of the tailcone to suit the motor casing, and an additional ring to make it ever so slightly longer and the larger OD of the airframe? You would probably need some sort of locating features to keep them coaxial, but probably easily achievable.

 

[GrouchoDuke]

If I have to choose just one, it’d be motor case diameter. For a max altitude record attempt kind of rocket, I’d want to taper the min-diameter rocket body to meet the taper on the motor.

On the other hand, if I want to do a quickly built, easy in the field min-diameter rocket, a constant diameter body tube with a tapered rear cone that matched its diameter would be great too. So...both!

 

[Salvage-1]

Motor case, for reasons stated before, including use as a sustainer motor.

 

[BDB]

Case. I’d love to use it for a sustainer.


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[Cl(VII)]

Which ever version you offer I'm sure I will happily end up with one.

 

[GrouchoDuke]

Forgot to mention...a tapered motor case diameter tail cone on a full-I 29mm Loki motor would be sweet too.

 

[dhbarr]

Case. I have some CTI that are airframe flush, and I can't hang them out a caliber or two like I want to. If I machine them that's EX, no NAR events.

 

[Tonimus]

The case makes the most sense. I could add a little ring of airframe and sand it to a taper if I wanted something to fit flush with the airframe and not want to modify existing rockets. Or you could possibly make/sell said ring for those who want something like that and it could match whatever your taper actually is.

 

[mpitfield]

if it was made to the motor case, you could always sand a taper into the back of the airframe in order to somewhat blend it into the tail cone without too much trouble. Conversely, it would require a machine lathe to turn down the tail cone in order to match the motor case. That would make a mess of the hardcoat finish.

Without modifications it sounds like machined to the O/D of the motor case is more flexible.

Case. I have some CTI that are airframe flush, and I can't hang them out a caliber or two like I want to. If I machine them that's EX, no NAR events.

The CTI 54mm is external where the tapered closure replaces the regular closure and also becomes the thrust ring. So I can see how it would be considered EX, because you are modifying something that potentially affects the integrity of the motor hardware. However their 98mm is internal using a wider rear closer that the tailcone threads onto. So if you modified that tailcone I wonder if it would be considered EX because the modification would not have any affect on the motor case integrity.

At least that is how I see it, anyone know if that is an accurate perception?

If so, and Loki had the case threaded internally, and it was certified this way, then could you not go as far as to use your own rear tailcone?

 

[plugger]

Scott, my thinking is that any way you do it somebody will not be happy. If you do it to the airframe which airframe- is it 54mm thick/standard, is it 54mm thin wall etc.

I would tend to lean towards the case for the above reason.


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+1. I hand roll my airframes and invariably my OD is smaller than commercial offerings. I always prefer tailcones flush with the casing.

 

[AeroAggie]

I think case makes the most sense for all the above reasons, but:

• What do you do with the thrust ring for staging coupler use? Do you use the forward closure to push against a bulkhead? I'm not into staging yet, so pardon my ignorance. But now I'm thinking about staging L to M on a 54 min diameter...:eyepop:
• How would you attach any tailcone on a case with internal snap ring nozzle retention? I'm thinking you'll have a two piece design with a threaded ring held in by the snap ring, then the tailcone/nozzle screws into that...?

I've got both the 2800 and 4000 and my gears are turning. Can't wait to see what you come up with!

 

[CoyoteNumber2]

I'm abstaining from voting as I would love to see both case and airframe offerings. Here is the tail cone I had made for the L1040 (yes, I know the OD doesn't match the airframe.)

 

[Zebedee]

Matching the case with an optional thrust ring for the airframe seems like an interesting compromise.

 

[Wizard]

I'm abstaining from voting as I would love to see both case and airframe offerings. Here is the tail cone I had made for the L1040 (yes, I know the OD doesn't match the airframe.)

View attachment 329399

Is that the cone for which you needed the case/nozzle measurements? That's Nice!

 

[mpitfield]

I'm abstaining from voting as I would love to see both case and airframe offerings. Here is the tail cone I had made for the L1040 (yes, I know the OD doesn't match the airframe.)

View attachment 329399

Hmm interesting, did you just use three set screws directly into the phenolic nozzle to hold that tail cone on?

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[CoyoteNumber2]

Is that the cone for which you needed the case/nozzle measurements? That's Nice!

Indeed. Thanks! I sketched it, and a coworker did the machining.

Hmm interesting, did you just use three set screws directly into the phenolic nozzle to hold that tail cone on?

Effectively. There's a few wraps of masking tape around the nozzle, which is about 1.71" OD, and the tail cone is made from 1.75" ID tubing. I'd be nervous about tightening set screws on the nozzle directly.

 

[Loki Research]

Matching the case with an optional thrust ring for the airframe seems like an interesting compromise.

Adding a second very small part just to transition between the airframe and case diameters adds a lot more cost and complexity in design than one might think. I'd still have the same problem that Mark mentioned. What type/brand/size airframe do you match the ring to?

Set screws directly to the phenolic nozzle is exactly how the prototype was done and it works great. The part is light enough in weight that doesn't take much to hold it in place, but the stock material has to be smaller than 1.75" in order to mate flush with the nozzles 1.710" OD. It is pictured here but I'll probably omit the flat ~1/4" long section.

If you've flown that L-1040 Coyote, please email me a short flight report and altimeter data if it has acceleration data.

 

[Tonimus]

Scott, very interesting solution. Given how the tailcone attaches to the nozzle, I agree that a small added ring that's only going to me a millimeter or two thick is a bunch of added work without much benefit. Motor case diameter seems to be the most logical direction.

 

[CoyoteNumber2]

If you've flown that L-1040 Coyote, please email me a short flight report and altimeter data if it has acceleration data.

Will do Scott. Probably won't fly it until December.

 

[afadeev]

I might add here, if it was made to the motor case, you could always sand a taper into the back of the airframe in order to somewhat blend it into the tail cone without too much trouble. Conversely, it would require a machine lathe to turn down the tail cone in order to match the motor case. That would make a mess of the hardcoat finish.

That, plus you can't control the airframe variations that people will build and fly.

Therefore - motor case.

a

 

[Rocketjunkie]

Motor case. Leave the 1/4" straight section for those who want the cone to match the airframe. They can attach a tapered piece of airframe.