Cesaroni spacer size?

[bill2654]

Does anyone know the outside diameter of the 38mm Cesaroni spacer?

 

[jpummil]

Hey Bill!

Already settled in for the evening, but I'll go dig one out in the morning and measure with some calipers

See ya Sunday!

--Jeff

 

[bill2654]

Thanks Jeff. I'll be flying my Gizmo (avitar) Sunday. See you there.

 

[qquake2k]

Does anyone know the outside diameter of the 38mm Cesaroni spacer?

Mine measures at 1.357". My Aerotech spacer measures at 1.3675".

 

[bill2654]

The reason I ask is I was wondering if it's possible to use spacers in a snap ring case. I need spacers with an OD of 1.30".

 

[troj]

The reason I ask is I was wondering if it's possible to use spacers in a snap ring case. I need spacers with an OD of 1.30".

I don't think any of the snap ring manufacturers offer spacers.

If they did, you'd need to use spacers designed for those cases, instead of spacers for another type of case. Otherwise, it would be an uncertified combination.

-Kevin

 

[bobkrech]

The reason I ask is I was wondering if it's possible to use spacers in a snap ring case. I need spacers with an OD of 1.30".

For EX purposes only as using a spacer decertifies a snap ring motor, a Kosdon type grain spacer is the length of 1 propellant grain.

The spacer OD needs to be a few mils less than the casing ID to slide in, and the spacer wall thickness needs to be thick enough so it will not buckle when loaded by the forward closure, but thin enough so it doesn't weigh a lot. I'd guess 1/32" minimum wall thickness, 1/16" maximum wall thickness with 6061T6 aluminum. Alternatively, heavy wall Phenolic CE liner cut to 1 grain length should also work. Phenolic is lighter than aluminum, so a double thickness is ok.

Kosdon style cases are heavier than the CTI or AT cases so you need to be carefull not to make the spacers and heavier than either the CTI or AT spacers, and be sure and run a sim with the correct loaded motor weight to make sure the reduced T/W ratio is sufficient for you rocket, and that the CG has not been shifted aft significantly to effect stability.

Bob

 

[COrocket]

I don't think any of the snap ring manufacturers offer spacers.

If they did, you'd need to use spacers designed for those cases, instead of spacers for another type of case. Otherwise, it would be an uncertified combination.

-Kevin

Gorilla does in 54 and 75MM. They even offer a 54MM starter set (bottom of the page)

https://gorillarocketmotors.com/hardware.php

 

[Pantherjon]

so it will not buckle when loaded by the forward closure, but thin enough so it doesn't weigh a lot.

Just to nit a pick..Wouldn't the proper sequence with spacer usage be from aft to fore: nozzle,grains, forward closure, spacer, forward internal snap ring. That is the sequence when using the spacer in my CTI 6G 75mm case..Should be pretty much the same in a snap ring case, yes?

 

[bobkrech]

Just to nit a pick..Wouldn't the proper sequence with spacer usage be from aft to fore: nozzle,grains, forward closure, spacer, forward internal snap ring. That is the sequence when using the spacer in my CTI 6G 75mm case..Should be pretty much the same in a snap ring case, yes?

Absolutely correct.

The internal combustion pressure will load the forward closure and push the spacer against the forward snap ring transfering the load, so the spacer must be stiff enough not to buckle under compressive loading.

Bob

 

[bill2654]

I guess I should have made my question more clear. Yes I do have a Kosdon case and I will be using it for EX. I was just curious about spacers so I wouldn't have to buy a whole range of differant size cases. Where can I get the heavy wall Phenolic CE liners? And what does CE stand for?

 

[bobkrech]

These composites are commonly called Garolite. You can get it from a number of online sources.

mcmaster.com has an adequate selection starting at page 3582 of their current on-line catalog.

Garolite X, XX, XXX = paper phenolic composite (aka phenolic motor liners)
Garolite LE = linen phenolic composite
Garolite CE = canvas phenolic composite

All should be ok for a spacer as would be 1/16" aluminum tubing.

Bob

 

[tfish]

I deleted my previous post do to it having some Ex stuff in it.

back to your normally scheduled showing.

Tony

 

[Sailorbill]

I have talked to several people that have used PVC or CPVC pipe. It is light, strong, easily available, and no the motors do not get hot enough to melt the pipe.