• Have you entered ???
    LAUNCH LAB ROCKETRY GIVEAWAY

CTI Discussion Thread

The Rocketry Forum

Help Support The Rocketry Forum:

Cesaroni Technologies

Lifetime Supporter
TRF Lifetime Supporter
Joined
Sep 29, 2020
Messages
76
Reaction score
155
Location
Gormley, ON
Do you have the dimensions of the adapter ring and the boat tail? I bought the PR98-AR and the PR98-BT for the Gen 2. The adapter ring looks to be the same size as a retaining ring, one half inch thick. When I tighten both the forward retaining ring until It's flush with the casing and the aft adapter ring so it sandwiches the motor between them, there are no threads left to screw on the boat tail. It almost seems like the adapter ring should be more than 1/2 inch thick. I am talking about the 5800 here with the 6xl case. When both 1/2 inch retaining rings are flush with the end of the casing, the motor is nice and tight between the rings.
The adapter ring is about .25" wider than the regular rings.
 

HyperSonic

Well-Known Member
TRF Supporter
Joined
Dec 31, 2016
Messages
217
Reaction score
108
Location
Loony Tunes Land
The adapter ring is about .25" wider than the regular rings.
Thank You. So what I must have bought thinking it was an Adapter ring, was really just a Retaining ring. The boat tail is OK with the correct threads. I was told by the seller that it was the Adapter Ring for the Gen 2 Boat Tail.

While I have you here, I was wondering if there would be any benefit or not from sharing the load by using the top of the motor to push on a bulkhead that is epoxied into place, either by using the end of the casing to push, or by using a threaded rod screwed into the FC, thus taking some of the load off the Boat Tail/thrust ring.
 

Cesaroni Technologies

Lifetime Supporter
TRF Lifetime Supporter
Joined
Sep 29, 2020
Messages
76
Reaction score
155
Location
Gormley, ON
Thank You. So what I must have bought thinking it was an Adapter ring, was really just a Retaining ring. The boat tail is OK with the correct threads. I was told by the seller that it was the Adapter Ring for the Gen 2 Boat Tail.

While I have you here, I was wondering if there would be any benefit or not from sharing the load by using the top of the motor to push on a bulkhead that is epoxied into place, either by using the end of the casing to push, or by using a threaded rod screwed into the FC, thus taking some of the load off the Boat Tail/thrust ring.
Yes any support at the top of the motor will provide benefit. The threaded hole at the top of the motor is usually used for motor retention.
 

OverTheTop

Well-Known Member
TRF Supporter
Joined
Jul 10, 2007
Messages
5,130
Reaction score
2,420
Location
Melbourne Australia
While I have you here, I was wondering if there would be any benefit or not from sharing the load by using the top of the motor to push on a bulkhead that is epoxied into place, either by using the end of the casing to push, or by using a threaded rod screwed into the FC, thus taking some of the load off the Boat Tail/thrust ring.
That is how I fly all my HPR. The length of airframe in compression is shorter so much less likely to buckle. The rear of the airframe is in tension where composites work better, rather than in compression. I take all thrust to the front mount.
 

HyperSonic

Well-Known Member
TRF Supporter
Joined
Dec 31, 2016
Messages
217
Reaction score
108
Location
Loony Tunes Land
That is how I fly all my HPR. The length of airframe in compression is shorter so much less likely to buckle. The rear of the airframe is in tension where composites work better, rather than in compression. I take all thrust to the front mount.
Do you push with the top of the casing, or would it be OK to push with a threaded rod screwed into the FC? I could use the threaded rod to do both, push under thrust, and retain the motor. Not sure about pushing with the FC. Seems like I might be trying to shove the FC down into the liner. How do you do it?
 

Cesaroni Technologies

Lifetime Supporter
TRF Lifetime Supporter
Joined
Sep 29, 2020
Messages
76
Reaction score
155
Location
Gormley, ON
Do you push with the top of the casing, or would it be OK to push with a threaded rod screwed into the FC? I could use the threaded rod to do both, push under thrust, and retain the motor. Not sure about pushing with the FC. Seems like I might be trying to shove the FC down into the liner. How do you do it?
No I wouldn't use the forward closure as a means of supporting thrust. You'll likely need to epoxy a coupler above the motor to support the bulkhead for the threaded rod anyway. Coupler adds support to the motor and threaded rod will retain it.
 

Dave A

Lifetime Supporter
TRF Lifetime Supporter
Joined
Jan 22, 2013
Messages
1,174
Reaction score
129
I use a "hub cap" and a CTI fwd to push on all of my 75 and 98 snap ring cases.
My N snap-ring casing has no thrust ring. I just "pushed" my 85# Patriot to 6200' on that N motor with a rod and large washer under the bulkplate..
I use it for extra protection with a eye on the end of it and a short kevlar lanyard to try to keep it with the vehicle if something worth to cato. No guarantee but it is worth the backup retention.

See below.
The secret to burning AT/CTI 98 reloads in a Kosdon 4" case, yeah I know it's considered EX.
I figured this out when burning CTI 75 loads in an AMW case, CTI, see what you started!
 

Attachments

Last edited:

HyperSonic

Well-Known Member
TRF Supporter
Joined
Dec 31, 2016
Messages
217
Reaction score
108
Location
Loony Tunes Land
No I wouldn't use the forward closure as a means of supporting thrust. You'll likely need to epoxy a coupler above the motor to support the bulkhead for the threaded rod anyway. Coupler adds support to the motor and threaded rod will retain it.
Thank You for your advise. I will come up with something that pushes off the casing (like the coupler idea) The reason I bring this up is because there isn't many threads inside the Gen 2 Boat Tail for a lot of thrust (N5800) and I wanted to try and help share some of the load.
 

gjrockets

Active Member
Joined
Aug 8, 2012
Messages
36
Reaction score
7
Hello TRF community.
My name is Bob Pouliot. I have worked for Cesaroni Technologies since 2007 and am a BAR since 2000. After recently being promoted to management I've been snooping around the TRF and I'm glad to see that it's very popular and insightful. My hope is that CTI can provide an outlet for rocketeers who have questions, comments or concerns about our products.
I'm not a "Rocket Scientist" as some may think. I will leave that distinction to those who have earned it. I do have basic knowledge of how things work, and with my 20+ years of experience flying I'm sure I can be a valuable asset.
So if you have any questions, comments or concerns I'd love to hear them, or if you just want to chat feel free.
Sorry if someone's already asked this but what's the status of the VMax motors? Is CTI no longer making them?
 

Cesaroni Technologies

Lifetime Supporter
TRF Lifetime Supporter
Joined
Sep 29, 2020
Messages
76
Reaction score
155
Location
Gormley, ON
Haven't made them for Pro X in 5 years, no plans to make them in the near future.
We do however still have Pro24 and Pro29 VMax available, as well as AMW 54 3 and 4G
 
Last edited:

Neutron95

Well-Known Member
TRF Supporter
Joined
Jan 17, 2010
Messages
332
Reaction score
147
Are there any new reloads being planned?

The CTI catalog is filled out pretty well, but there will always be motors that people want that aren't available. Personally, I would love an Imax reload for the 29 6XL casing, as well as more Mellow motors. I would also love to see more unconventional motor designs, like the J145.
 

crossfire

Lifetime Supporter
TRF Lifetime Supporter
Joined
Jan 16, 2011
Messages
4,712
Reaction score
592
I use a "hub cap" and a CTI fwd to push on all of my 75 and 98 snap ring cases.
My N snap-ring casing has no thrust ring. I just "pushed" my 85# Patriot to 6200' on that N motor with a rod and large washer under the bulkplate..
I use it for extra protection with a eye on the end of it and a short kevlar lanyard to try to keep it with the vehicle if something worth to cato. No guarantee but it is worth the backup retention.

See below.
The secret to burning AT/CTI 98 reloads in a Kosdon 4" case, yeah I know it's considered EX.
I figured this out when burning CTI 75 loads in an AMW case, CTI, see what you started!
I have heard and see the hub cap for years but what does it do?
 

T34zac

Well-Known Member
Joined
Jul 23, 2014
Messages
944
Reaction score
31
Location
Massachusetts
I have heard and see the hub cap for years but what does it do?
Allows you to fly CTI 75mm loads in AMW snap ring hardware. The hubcap sits on top of the CTI 75mm forward closure and once the reload is assembled in the case, you tighten the bolts on top to 'compress' the reload in the case.

I used one a number of years ago for a L395 with a spacer in an AMW case.
 

crossfire

Lifetime Supporter
TRF Lifetime Supporter
Joined
Jan 16, 2011
Messages
4,712
Reaction score
592
Allows you to fly CTI 75mm loads in AMW snap ring hardware. The hubcap sits on top of the CTI 75mm forward closure and once the reload is assembled in the case, you tighten the bolts on top to 'compress' the reload in the case.

I used one a number of years ago for a L395 with a spacer in an AMW case.
Thanks for info.
 

OverTheTop

Well-Known Member
TRF Supporter
Joined
Jul 10, 2007
Messages
5,130
Reaction score
2,420
Location
Melbourne Australia
Do you push with the top of the casing, or would it be OK to push with a threaded rod screwed into the FC? I could use the threaded rod to do both, push under thrust, and retain the motor. Not sure about pushing with the FC. Seems like I might be trying to shove the FC down into the liner. How do you do it?
I only push on the forward closure. I do not have the front of the casing end against a shoulder.

No I wouldn't use the forward closure as a means of supporting thrust. You'll likely need to epoxy a coupler above the motor to support the bulkhead for the threaded rod anyway. Coupler adds support to the motor and threaded rod will retain it.
What is the rationale for that please?
 

JimJarvis50

Well-Known Member
Joined
Jan 18, 2009
Messages
2,515
Reaction score
817
Allows you to fly CTI 75mm loads in AMW snap ring hardware. The hubcap sits on top of the CTI 75mm forward closure and once the reload is assembled in the case, you tighten the bolts on top to 'compress' the reload in the case.

I used one a number of years ago for a L395 with a spacer in an AMW case.
I'm glad you mentioned that the L395 can be used with the AMW case and the hub cap. I have that combination in the works for an upcoming flight, but won't have any fallback if this were not to be feasible. Relieved to see that this works.

By the way, I hope no one is using the forward closure as a push point. Seems like a bang just waiting to happen.

Jim
 

eggplant

L3 | NAR 93664, TRA 17791
Joined
Jan 5, 2011
Messages
1,727
Reaction score
199
Assume an N5800 runs at a chamber pressure of 1000 PSI and has a closure diameter of 3.5". That means that there's nearly 10,000 lbf pushing the closure against the retention ring during a firing. The 1500 lbf peak thrust isn't close.

Obviously if CTI doesn't recommend it I wouldn't do it to avoid warranty issues, but I would be curious to hear their reasoning in case there is something I've missed. I've static fired up through 4" N motors with the thrust going through the forward closure into the stand without an issue.
 

OverTheTop

Well-Known Member
TRF Supporter
Joined
Jul 10, 2007
Messages
5,130
Reaction score
2,420
Location
Melbourne Australia
I am curious too. I have flown all my HPR that way and have not had a cato. I have had a very good think about it and could not come up with a reason to invalidate my method. I am happy to be told I'm wrong, but I want the reasoning behind it.

Be prepared to convince me using physics and/or engineering.
 
Last edited:

rocket_troy

Well-Known Member
Joined
Sep 9, 2013
Messages
194
Reaction score
70
Assume an N5800 runs at a chamber pressure of 1000 PSI and has a closure diameter of 3.5". That means that there's nearly 10,000 lbf pushing the closure against the retention ring during a firing. The 1500 lbf peak thrust isn't close.
Chamber pressure shouldn't really matter. The active forces involved are the (upper) chamber pressure x active area of forward bulkhead vs Pc x At x Cf
note: the 2 Pc terms cancel out

or (Pc x bulkhead area) / thrust

Every commercial HPR motor will have the numerator substantially greater than the denominator in that equation which provides agreement with the point you and Stewart are making.

TP
 
Last edited:

Cesaroni Technologies

Lifetime Supporter
TRF Lifetime Supporter
Joined
Sep 29, 2020
Messages
76
Reaction score
155
Location
Gormley, ON
Are there any new reloads being planned?

The CTI catalog is filled out pretty well, but there will always be motors that people want that aren't available. Personally, I would love an Imax reload for the 29 6XL casing, as well as more Mellow motors. I would also love to see more unconventional motor designs, like the J145.
Likely won't be many new propellants in the near future, but we are planning on certifying some more existing propellants, the Pro29 IM and more mellow are on the list.
 

gjrockets

Active Member
Joined
Aug 8, 2012
Messages
36
Reaction score
7
Haven't made them for Pro X in 5 years, no plans to make them in the near future.
We do however still have Pro24 and Pro29 VMax available, as well as AMW 54 3 and 4G
What # of grains for the 29mm? I think my local dealer doesn't know that any VMax's are available anymore so I want to see if he can get me some.
 

JimJarvis50

Well-Known Member
Joined
Jan 18, 2009
Messages
2,515
Reaction score
817
It is the only way I fly Jim. No CATO yet. The physics said it should work ;) .
The physics are fine as long as the motor is burning normally. Are there any conditions or motor types where this would not be the case? I'd be curious to hear from CTI on this as well.

I would point out that the motor isn't designed to perform this function and that the method brings other factors into play. Just some things that occur to me are what length of threaded rod will this work for - if the rod is 3/8 or 5/16 for example. Can I push on a 3-foot length of all thread? If the thrust is transferred to a bulkplate at the top of the coupler, then that bulkhead would take all of the force. You wouldn't design a motor mount with all of the force transferred to a glue joint on one centering ring? Is the bulkhead itself strong enough? Are the treads on the closure and the point where thrust is applied up to the task?

I was reviewing a college project earlier this year where, as best as I could tell, they were proposing this technique. I asked about it but things got derailed before they answered. But the above were a few things I was asking about for their project.

Jim
 

Cesaroni Technologies

Lifetime Supporter
TRF Lifetime Supporter
Joined
Sep 29, 2020
Messages
76
Reaction score
155
Location
Gormley, ON
It is the only way I fly Jim. No CATO yet. The physics said it should work ;) .
I understand what you're saying. When the motor is under pressure there is enough force on the forward closure to withstand the push from the motor. From my point of view (not saying it's the right point of view 🙂), since the forward closure isn't fixed to the case mechanically I wouldn't use it to push on.
I beleive on AT cases the forward closure screws onto the case, those I wouldn't have an issue with.
 
Top