AeroTech Open Thread

[mtnmanak]

RASP file for the K1800 was posted on Thrustcurve today. Similar impulse to the K1000, but with ~50% more initial thrust and 42% faster burn - Yowza! Ran it in a bunch of sims in my existing rockets. As expected, looks to be a massively cool motor for 4 x 75mm clusters. Sim indicates my 8" Goblin will reach 85 MPH by the end of the rail and hit Mach 1.1, all while staying under 8000 feet. Seriously awesome.

 

[AeroTech]

Any chance of these new motor offered in DMS?

There’s always a chance, but not in the works at the moment.

 

[AeroTech]

I asked about 29mm DM motors some pages back, and the answer is that they won't happen because of some arcane transportation exemption or something like that.

DM works for 29mm single use (like the H115DM) but not 29mm reloads because of the nature and scope of our existing DOT approvals. We’re not going to spend $25,000+ for a new approval to sell a few 29mm DM reloads.

 

[smstachwick]

I know it’s a bit off-topic from strictly propulsion, but this still seemed to be the right place to ask: how long is the motor mount tube on the Big Dog kit? I might be in the market for it or something like it, but dimensional data is scarce.

 

[Antares JS]

The K750ST and K1800ST look so interesting that you've got me looking for a kit to fly on those motors. The Wildman Competitor 4 or the Demon 5 look pretty good...

 

[jmasterj]

DM works for 29mm single use (like the H115DM) but not 29mm reloads because of the nature and scope of our existing DOT approvals. We’re not going to spend $25,000+ for a new approval to sell a few 29mm DM reloads.

Thanks for the correction.

 

[Theory]

The K750ST and K1800ST look so interesting that you've got me looking for a kit to fly on those motors. The Wildman Competitor 4 or the Demon 5 look pretty good...

would vote for the Competitor 4

My custom built 17pound 4" bird is similar and sims very nicely on both.

 

[rcktnut]

I know it’s a bit off-topic from strictly propulsion, but this still seemed to be the right place to ask: how long is the motor mount tube on the Big Dog kit? I might be in the market for it or something like it, but dimensional data is scarce.

It is 4.5 in. long

 

[smstachwick]

It is 4.5 in. long

Thank you! That’ll go on my shopping list, then.

 

[StreuB1]

The K750ST and K1800ST look so interesting that you've got me looking for a kit to fly on those motors. The Wildman Competitor 4 or the Demon 5 look pretty good...

Demon 5 is an amazing rocket and a wonderful performer, very versatile as well regarding the motors you can fly it on. Fly it on a big-J or punch-it-off on an M1780NT (Like I am doing at Airfest ;-) ). I have the Demon 5 and the Demon 150. Love them both!!!! Though, the Competitor is also wonderful. Can't go wrong with either.

Below I am flying my Demon 5 on an L1520T at the QCRC club launch last November.

 

[mtnmanak]

The K750ST and K1800ST look so interesting that you've got me looking for a kit to fly on those motors. The Wildman Competitor 4 or the Demon 5 look pretty good...

The WM 5" Goblin is another fun option for these motors. Mine sims out to about 5500 feet on the K1800 - perfect for one of the nice days at Higgs Farm!

 

[Brian H.]

I have an M1800FJ-P that I am getting familiarized with for my L3 certification this weekend. There are 3 extra o-rings .07" thick x 3.90" diameter. There is no mention in the assembly instructions or the assembly drawing from RCS about them.

I would guess they are grain spacer o-rings, but I hate to assume and risk the cert flight.

@AeroTech ??

 

[jd2cylman]

I have an M1800FJ-P that I am getting familiarized with for my L3 certification this weekend. There are 3 extra o-rings .07" thick x 3.90" diameter. There is no mention in the assembly instructions or the assembly drawing from RCS about them.

I would guess they are grain spacer o-rings, but I hate to assume and risk the cert flight.

@AeroTech ??

I'm not @AeroTech , but if they're 1/16" in diameter, then yes, they're grain spacers. Reread your instructions. It should be mentioned. Or, check your parts list. They should be mentioned there.

 

[Brian H.]

I'm not @AeroTech , but if they're 1/16" in diameter, then yes, they're grain spacers. Reread your instructions. It should be mentioned. Or, check your parts list. They should be mentioned there.

I read the instructions 3 times (along with included parts list).
Downloaded the instructions from their website in case an old copy came with reload.
Assembly instructions are here:
https://d11fdyfhxcs9cr.cloudfront.n...yimages/98_10240fj_in_20100_1642720641618.pdf
Downloaded assembly drawing:
https://d11fdyfhxcs9cr.cloudfront.n...ges/98-10240_m1800fj-p_assy_1648897819692.pdf

No mention of these o-rings anywhere.

The parts list also says a phenolic forward seal disc is included with the reload. It is not there, but I plan to use the aluminum forward seal disc that came with the hardware.

 

[Brian H.]

I'm not @AeroTech , but if they're 1/16" in diameter, then yes, they're grain spacers. Reread your instructions. It should be mentioned. Or, check your parts list. They should be mentioned there.

I believe I found what I needed on their website in their 98/2560-15360 generic instructions here:
https://d11fdyfhxcs9cr.cloudfront.n...-15360 2-page instr 3-15-22_1656446404864.pdf

It tells you what to do with the spacer o-rings if they are in the reload.

Would be nice to have all pertinent information included with the reload.

 

[StreuB1]

The callout in the parts list in the assy instructions "Forward seal disk (3-5/8" O.D. phenolic disk)" is likely a typo and/or remnant from another set of instructions that were copied and amended for creating these instructions. This is how engineering works, we reuse ALL the time; we don't redraw or type things. "Copy Based On - Except For" Because of this, at times errors can propagate. Happens to me time to time. Not saying that is what happened here but it is just my guess.

A bit odd though that the o-ring spacers are not called out, but are included.

 

[boatgeek]

The callout in the parts list in the assy instructions "Forward seal disk (3-5/8" O.D. phenolic disk)" is likely a typo and/or remnant from another set of instructions that were copied and amended for creating these instructions. This is how engineering works, we reuse ALL the time; we don't redraw or type things. "Copy Based On - Except For" Because of this, at times errors can propagate. Happens to me time to time. Not saying that is what happened here but it is just my guess.

A bit odd though that the o-ring spacers are not called out, but are included.

Why did the engineer cross the road?

They looked in the file and that's what they did last year.

 

[StreuB1]

Why did the engineer cross the road?

They looked in the file and that's what they did last year.

DAMN YOU!!!

 

[Theory]

Arrived!!!!!!!

 

[3stoogesrocketry]

Arrived!!!!!!!

View attachment 533433

Can we talk about this 75/10240......

 

[Theory]

Noticed that too…

Unsure exactly what’s up with it

 

[StreuB1]

Can we talk about this 75/10240......

Sooooo, @AeroTech ..........

 

[AeroTech]

I have an M1800FJ-P that I am getting familiarized with for my L3 certification this weekend. There are 3 extra o-rings .07" thick x 3.90" diameter. There is no mention in the assembly instructions or the assembly drawing from RCS about them.

I would guess they are grain spacer o-rings, but I hate to assume and risk the cert flight.

@AeroTech ??

How old is the reload and what instructions came with it?

 

[Brian H.]

How old is the reload and what instructions came with it?

Moto Joe said it was a pretty old reload.
The date code on one of the grains is 05111702
The instructions that came with it are the same ones available for download from the RCS website here:
https://d11fdyfhxcs9cr.cloudfront.n...yimages/98_10240fj_in_20100_1642720641618.pdf
I found mention of grain spacer o-rings int the 98/2560-15360 generic instructions and assembled it with the o-rings just dropped in-between the grains. Flight was successful and I am now L3!!

 

[gdjsky01]

Confirmed, really nice motor. Cant wait to see the K-1800 as well! Typical that the photos and video do not do the motor justice.
View attachment 532199

The photo does more 'justice' than the useless video. JMO. And YMMV

 

[wsume99]

Now that production of the J510W has been suspended I have a question for @AeroTech, are you planning to continue offering the 38/1320 EMK on RCS?

 

[JohnCoker]

Does anyone have the certification letter for the DMS I65?

 

[Sooner Boomer]

Something I thought of while getting things layed out for Airfest; it would be nice to have a motor martix that breaks out motors/loads by propellant type in each diameter/case. Sometimes I want a particular "flavor" to fly a specific rocket with.

 

[jmasterj]

Something I thought of while getting things layed out for Airfest; it would be nice to have a motor martix that breaks out motors/loads by propellant type in each diameter/case. Sometimes I want a particular "flavor" to fly a specific rocket with.

You can do that with thrust curve since AT includes the propellant type in the designation.

 

[SolarYellow]

Not sure if this has been answered before, but figured this is the thread to ask.
I'm looking at using 24mm RMS motors in a minimum diameter 24mm rocket with a carbon fiber tube. I assume the motor case gets hot and will thus expand during flight. How much room does it need? If I mount it in a carbon fiber tube that is a true 24mm ID, is that enough clearance for thermal expansion? Or does it need to be 24.1mm? I'm assuming straightness of the tube and motor case will be adequate over the relevant 40-60mm.

I'm asking because I've found a supplier of off the shelf nominal 24 ID / 25 OD carbon tube. There's a build thread here (probably a few) for a successful 29mm rocket >1.5 Mach with a 0.013 carbon sleeve over 0.013 cardboard tube, so I'm figuring 0.020 solid carbon with some bulkheads and couplers reinforcing it should be enough structure to get into the transonic range and knock on the door of Mach 1 safely. Don't want to add too much weight; 1mm wall thickness is available, but obviously weighs twice as much and that eats into performance.

Basically, I'm looking to build an MD rocket to mess around with the bigger MPR 24mm motor ranges. Not having to deal with the material, tooling and labor costs of sleeving cardboard is attractive. Until today, I hadn't found anyone selling appropriate solid c.f. tubes in 24mm sizes. And they are all much thicker in the larger sizes, so I'd discounted solid carbon as an option.